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1

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

USGS Publications Warehouse

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.

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

2

The “VIM” users group  

Microsoft Academic Search

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

F. William Rambo

1975-01-01

3

Wavelength scaling of laser plasma coupling  

SciTech Connect

The use of shorter wavelength laser light both enhances collisional absorption and reduces deleterious collective plasma effects. Coupling processes which can be important in reactor-size targets are briefly reviewed. Simple estimates are presented for the intensity-wavelength regime in which collisional absorption is high and collective effects are minimized.

Kruer, W.L.

1983-11-03

4

Effective Wavelength Scaling for Optical Antennas Lukas Novotny*  

E-print Network

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

Novotny, Lukas

5

Estimation of wavelength difference using scale adjustment in two-wavelength digital holographic interferometry.  

PubMed

We propose a method for an estimation of wavelength difference using scale adjustment in two-wavelength digital holographic interferometry. To estimate wavelength difference, two holograms recorded with different wavelengths are reconstructed on the basis of the Fresnel diffraction integral, and pixel sizes in the reconstruction plane, which depend on the wavelength in recording hologram, are analyzed. In the analysis, a zero-padding method and an intensity correlation function are used to adjust pixel sizes in the reconstruction plane and then obtain a wavelength difference given by a difference between the pixel sizes. Theoretical predictions and experimental results are shown to indicate the usefulness of the proposed method in this paper. PMID:22086028

Funamizu, Hideki; Aizu, Yoshihisa

2011-11-01

6

Laboratory-scale mirrors for submillimeter wavelengths  

NASA Astrophysics Data System (ADS)

A machining procedure based on an elementary concept has been applied successfully to produce metal mirrors suitable for submillimeter wavelengths. Ninety-degree off-axis paraboloidal or ellipsoidal mirror sections may be cut from brass or aluminum by means of a series of predetermined increments on a conventional laboratory lathe. Paraboloidal mirrors with low f-numbers (f/2) made by this technique have been used with good results as part of the collecting optics of a submillimeter-wave heterodyne radiometer.

Dionne, G. F.

1982-05-01

7

Laboratory-scale mirrors for submillimeter wavelengths  

Microsoft Academic Search

A machining procedure based on an elementary concept has been applied successfully to produce metal mirrors suitable for submillimeter wavelengths. Ninety-degree off-axis paraboloidal or ellipsoidal mirror sections may be cut from brass or aluminum by means of a series of predetermined increments on a conventional laboratory lathe. Paraboloidal mirrors with low f-numbers (f\\/2) made by this technique have been used

G. F. Dionne

1982-01-01

8

Principal components analysis of Jupiter VIMS spectra  

USGS Publications Warehouse

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

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

2004-01-01

9

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

USGS Publications Warehouse

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

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

2008-01-01

10

A close look at Saturn's rings with Cassini VIMS  

USGS Publications Warehouse

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

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

2008-01-01

11

Talbot images of wavelength-scale amplitude gratings.  

PubMed

By means of experiment and simulation, we achieve unprecedented insights into the formation of Talbot images to be observed in transmission for light diffracted at wavelength-scale amplitude gratings. Emphasis is put on disclosing the impact and the interplay of various diffraction orders to the formation of Talbot images. They can be manipulated by selective filtering in the Fourier plane. Experiments are performed with a high-resolution interference microscope that measures the amplitude and phase of fields in real-space. Simulations have been performed using rigorous diffraction theory. Specific phase features, such as singularities found in the Talbot images, are discussed. This detailed analysis helps to understand the response of fine gratings. It provides moreover new insights into the fundamental properties of gratings that often find use in applications such as, e.g., lithography, sensing, and imaging. PMID:22418296

Kim, Myun-Sik; Scharf, Toralf; Menzel, Christoph; Rockstuhl, Carsten; Herzig, Hans Peter

2012-02-27

12

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

E-print Network

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

Lai, Chien-Jen

13

Chip-scale wavelength-division multiplexed integrated sensor arrays  

Microsoft Academic Search

We demonstrate a wavelength-division multiplexing (WDM) technique for interrogating multiple sensors on a single chip. While wavelength- and frequency-division multiplexing (FDM) has previously been demonstrated in micro-electro mechanical (MEMS) sensors, numerous off-chip components were required thereby increasing the system size and limiting the number of sensors. In contrast, our approach enables all components to be developed on-chip. The high Q-factor

Marcel W. Pruessner; Todd H. Stievater; R. Bass; J. B. Boos

2010-01-01

14

Composition of Titan's surface from Cassini VIMS  

USGS Publications Warehouse

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.

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

15

Molding the flow of light at deep sub-wavelength scale  

E-print Network

The diffractive nature of light has limited optics and photonics to operate at scales much larger than the wavelength of light. The major challenge in scaling-down integrated photonics is how to mold the light flow below diffraction-limit in all three dimensions. A high index solid immersion lens can improve the spatial resolution by increasing the medium refractive index, but only to few times higher than in air. Photonic crystals can guide light in three dimensions, however, the guided beam width is around a wavelength. Surface plasmons has a potential to reach the sub-wavelength scales; nevertheless, it is confined in the two-dimensional interface between metals and dielectrics. Here, we present a new approach for molding the light flow at the deep sub-wavelength scale, using metamaterials with uniquely designed dispersion. We develop a design methodology for realizing sub-wavelength ray optics, and demonstrate lambda/10 width light beams flow through three-dimensional space.

Han, Seunghoon; Genov, Dentcho; Liu, Zhaowei; Bartal, Guy; Zhang, Xiang

2007-01-01

16

Wavelength scale terahertz two-dimensional photonic crystal waveguides.  

PubMed

A terahertz-scale two-dimensional photonic-crystal waveguide based on a silicon-on-insulator was fabricated, and the optical transmission spectrum was measured. Terahertz beam propagation characteristics were observed using a thermal imaging camera, with incident light in the 10.1-10.7 microm range. The measured transmission spectrum was in good agreement with a three-dimensional finite-difference time-domain calculation. PMID:19488208

Lin, Chunchen; Chen, Caihua; Schneider, Garrett; Yao, Peng; Shi, Shouyuan; Sharkawy, Ahmed; Prather, Dennis

2004-11-15

17

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

PubMed Central

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

Montealegre, Maria Camila; Correa, Adriana; Briceño, 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

18

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

19

A multi-scale, multi-wavelength source extraction method: getsources  

NASA Astrophysics Data System (ADS)

We present a multi-scale, multi-wavelength source extraction algorithm called getsources. Although it has been designed primarily for use in the far-infrared surveys of Galactic star-forming regions with Herschel, the method can be applied to many other astronomical images. Instead of the traditional approach of extracting sources in the observed images, the new method analyzes fine spatial decompositions of original images across a wide range of scales and across all wavebands. It cleans those single-scale images of noise and background, and constructs wavelength-independent single-scale detection images that preserve information in both spatial and wavelength dimensions. Sources are detected in the combined detection images by following the evolution of their segmentation masks across all spatial scales. Measurements of the source properties are done in the original background-subtracted images at each wavelength; the background is estimated by interpolation under the source footprints and overlapping sources are deblended in an iterative procedure. In addition to the main catalog of sources, various catalogs and images are produced that aid scientific exploitation of the extraction results. We illustrate the performance of getsources on Herschel images by extracting sources in sub-fields of the Aquila and Rosette star-forming regions. The source extraction code and validation images with a reference extraction catalog are freely available.

Men'shchikov, A.; André, Ph.; Didelon, P.; Motte, F.; Hennemann, M.; Schneider, N.

2012-06-01

20

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

21

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

Microsoft Academic Search

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

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

2008-01-01

22

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

NASA Astrophysics Data System (ADS)

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

Goguen, Jay D.; Buratti, Bonnie J.

2014-11-01

23

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

Microsoft Academic Search

A high-speed cyclonic vortex centered on the north pole of Saturn has been revealed by the visual-infrared mapping spectrometer (VIMS) onboard the Cassini–Huygens Orbiter, thus showing that the tropospheres of both poles of Saturn are occupied by cyclonic vortices with winds exceeding 135m\\/s. High-spatial-resolution (~200km per pixel) images acquired predominantly under night-time conditions during Saturn's polar winter—using a thermal wavelength

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

2009-01-01

24

Cloud-Top evaluation of a Saturn's giant vortex by Cassini VIMS-V observations  

NASA Astrophysics Data System (ADS)

Recent observations of Saturn performed by the Cassini probe, orbiting the ringed system since July 2004, show that a giant oval structure has formed in the planet's North hemisphere. The structure has been observed in different hyperspectral images retrieved by VIMS-V, on board Cassini, starting from May 2011. VIMS is a multi-channel imaging spectrometer, able to produce 2D images of the observed target that also contain their spectral information. The instrument consists of an infrared channel (VIMS-IR) ranging from 0.85 to 5.1 ?m and a visual channel (VIMS-V) operating in the wavelength range 0.35 - 1.05 ?m; the visual channel has a nominal spectral resolution of 7.3 nm and a nominal angular resolution of 500 ?rad; in this study we will work on the data collected by this last one. We evaluate the top level of the clouds located over the oval structure observed on January 2012 by VIMS around 35° North latitude, by examining the bottom of the 0.89-?m methane (CH4) absorption band by means of the VIMS-V hyperspectral images analysis. Methane is indeed the most absorbing gas in Saturn's atmosphere in the wavelength range covered by VIMS-V. Moreover, the 0.89 ?m absorption band is the strongest in this wavelength range and it allows us to sound the highest levels of the atmosphere. A radiative transfer model has been developed to simulate the radiance field on the planet. This model uses the discrete ordinate solver for a plane parallel atmosphere and considers different configurations of microphysical, optical and geometrical parameters both for clouds and aerosols. These parameters have been tested to fit to the 0.89 ?m CH4 absorption band whose depth depends also on the reflection by the highest clouds and/or haze layers. Finally, aerosol parameters must be carefully tuned to obtain the same shape between the synthetic and VIMS-V measured spectra. Vortices have been observed at Saturn since the Voyager missions, but thanks to Cassini we now have the possibility to study their evolution with a better continuity and with high spatial and spectral resolution. The temporal variability for the retrieved cloud-top level is then checked by analyzing two hyperspectral observations imaging the same vortex, recorded on a time lapse of five months. To this extent we'll take advantage of the results obtained in a parallel study (Moriconi et al., 2012) and presented in a second abstract. References M.L. Moriconi, E. D'Aversa, A. Adriani, G.Filacchione: Cassini VIMS-V observations of a giant dynamical structure in the Saturn's northern hemisphere. Abstract submitted to this meeting, 2012.

Oliva, F.; Adriani, A.; Moriconi, M. L.

2012-12-01

25

VIMS Molluscan Ecology Oyster Reef Community Research  

NSDL National Science Digital Library

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

26

Mimas: Preliminary Evidence For Amorphous Water Ice from VIMS  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

27

Energy and wavelength scaling of shock-ignited inertial fusion targets  

NASA Astrophysics Data System (ADS)

In inertial fusion shock ignition, separation of the stages of fuel compression and hot spot creation introduces some degree of design flexibility. A lower implosion velocity can be compensated for by a more intense ignition pulse. Flexibility increases with target (and driver) size and allows for a compromise between energy gain and risk reduction. Having designed a reference ignition target, we have developed an analytical model for (up)-scaling targets as a function of laser energy, while keeping under control parameters related to hydro- and plasma instabilities. Detailed one-dimensional simulations confirm the model and generate gain curves. Options for increasing target robustness are also discussed. The previous results apply to UV laser light (with wavelength ? = 0.35 ?m). We also show that our scaling model can be used in the design of targets driven by green laser light (? = 0.53 ?m).

Atzeni, S.; Marocchino, A.; Schiavi, A.; Schurtz, G.

2013-04-01

28

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

E-print Network

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

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

2011-10-14

29

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

PubMed

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

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

2014-10-30

30

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

31

Mapping of Titan surface at high resolution with VIMS/CASSINI hyperspectral images  

NASA Astrophysics Data System (ADS)

The VIMS imaging spectrometer onboard CASSINI provides images of Titan in 352 contiguous spectral channels from 0.3 to 5.1 ?m. The infrared domain is particularly useful to image the surface of Titan through the atmosphere, which is completely opaque at visible wavelengths. In this study, the emphasize will be made on the processing strategies for VIMS data in order to improve the surface mapping capabilities, despite the blurring effects of the atmospheric aerosols. Indeed, both spatial and spectral filtering strategies can be applied to the data to help in characterizing Titan surface properties. The spatial dimension provides information about the morphology of surface features, and the spectral information, when combined accurately, allows the mapping of the main compositional heterogeneities. VIMS acquires images of 64x64 pixels using two scanning mirrors. However, it can also operate in single line mode (1x64) using a single scanning mirror, with the second dimension of the image being given by the evolution of the ground track of the satellite ("noodle" mode). This is particularly useful when VIMS is observing within the closest approach period. The first test of this observing strategy was done on 25 October 2006 (T20 flyby). The example of the T20 data, which are so far the best VIMS data in terms of spatial resolution (reaching 500m/pixels at closest approach) will therefore be discussed. Short time exposure are needed to operate fast enough during the closest approach period. We show that the signal quality can be significantly improved in this particular case by using a series of processing steps such as an optimisation of the dark current removal, a minimum noise fraction analysis, a co-adding of several adjacent spectral channels and the use of band ratios. Infrared images of surface features as small as the dunes can be obtained, which is particularly interesting for the comparison with radar images. Similarly, flow-like features have been mapped, and areas possibly enriched in water ice have been found at the border between bright and dark regions. These processing steps can have implication for the design of the forthcoming flybys both in the nominal and extended mission. The next opportunity for VIMS to observe in this "noodle" mode will be at the end of July 2007 (T34), which will also be presented at the workshop.

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

2007-08-01

32

Ten Years of VIMS at Saturn  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft is an imaging spectrometer that has 352 spectral channels comprising a range of 0.35-5.2 microns, and a pixel size of 500 mrad. In the roughly ten years since it has been obtaining data on all the objects in the Saturn system, it has made a number of important advances in our understanding of Saturn, its rings, satellites, atmosphere and magnetosphere. Those advances and our expectations for future advances will be described.

Brown, Robert H.

2014-05-01

33

Cassini/VIMS observations of the moon  

USGS Publications Warehouse

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

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

2002-01-01

34

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

PubMed Central

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

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

2013-01-01

35

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

SciTech Connect

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

Blomquist, R.N.

1992-09-01

36

Lessons learned from applying VIM to fast reactor critical experiments  

SciTech Connect

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.

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

1995-05-17

37

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

USGS Publications Warehouse

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

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

2004-01-01

38

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

PubMed Central

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

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

2008-01-01

39

Mapping the Atmospheric and Surface Properties of Titan by the Massive Inversion of Cassini/VIMS Spectra  

NASA Astrophysics Data System (ADS)

Since the beginning of the Cassini mission, the imaging spectrometer VIMS has acquired ~40000 hyperspectral images of Titan containing several millions of spectra. Such a huge amount of data cannot be analyzed with a radiative transfer solver like SHDOM because of computational limits. Nevertheless, such a solver is the most suited tool to extract simultaneous information of the atmosphere and the surface of Titan from VIMS datacubes. We have developed a method of analyzing VIMS data that consents to use the power of a RT model without the inconvenience of long computational times, by the creation of look-up tables for different values of the RT model's parameters (geometry of the observation, surface albedo, aerosols opacity). We employ up-to-date information on gaseous spectral coefficients, aerosols’ optical properties and Titan’s climatology. These look-up tables, appropriately interpolated, are then used to minimize the observations and create simultaneous maps of aerosols opacity and of surface albedo (at the wavelengths of Titan’s spectral windows). This method lowers the computational time by a factor of several thousands and thus, for the first time, a truly massive treatment of VIMS data. In this paper we present the results of our method applied to the area of the Huygens landing site and their comparison with the results of other Cassini instruments. We also show the retrieved maps of a region observed multiple times at different Cassini flybys with different observational conditions, as the T13/T17 mosaic of the Atzlan area. The perspectives for atmospheric and surface seasonal monitoring are highlighted.

Maltagliati, Luca; Rodriguez, Sébastien; Appéré, Thomas; Vincendon, Mathieu; Douté, Sylvain; LeMouelic, Stéphane; Rannou, Pascal; Sotin, Christophe; Barnes, Jason W.; Coustenis, Athena; Brown, Robert H.

2014-11-01

40

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

Microsoft Academic Search

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

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

2007-01-01

41

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

SciTech Connect

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

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

2011-02-01

42

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

NASA Astrophysics Data System (ADS)

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.

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

43

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

NASA Astrophysics Data System (ADS)

We present new results combining the VIMS and RADAR medium resolution data on Titan’s surface. In RADAR data we consider two geophysical quantities: the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for the incidence angle, and the calibrated antenna temperature determined from the radiometer measurement, as found in publicly available data products. In VIMS data, combining spatial and spectral information, we have selected some atmospheric windows in the spectral range between 2 and 5 ?m, providing the best optical depth to measure surface reflectance. The two RADAR parameters are combined with VIMS data, with estimated errors, to produce an aggregate data set, that we process using multivariate classification methods to identify homogeneous taxonomic units in the multivariate space of the samples. 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.

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

44

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

SciTech Connect

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

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

1990-05-01

45

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

NASA Astrophysics Data System (ADS)

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.

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

1989-06-01

46

Titan's Atmosphere Observed by Cassini/VIMS Solar Occultations  

NASA Astrophysics Data System (ADS)

VIMS solar occultations provide a unique opportunity to extract information on the vertical characteristics of Titan's atmosphere between 50- 700 km with a vertical resolution of 10 km on average. We will present here the analysis of the full VIMS solar occultation dataset, which includes 10 occultations. Due to various observational problems, we could retain only 4 of them, which span different seasons and latitudes. We extracte the vertical profiles of methane and CO. CH4 profiles show a significantly lower stratospheric abundance with respect to the GCMS value (1.28% vs. 1.48%). We also detect and identify several absorption bands that are not included in our atmospheric model. Most of them can be attributed to gaseous ethane, whose near-IR spectrum has been measured in laboratory but not modeled. Other additional absorptions are instead attributed to the C-H stretching bands associated with aerosols, generated by aliphatic and possibly aromatic hydrocarbons.

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

2014-04-01

47

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

NASA Astrophysics Data System (ADS)

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.

Mari, Luca

2015-02-01

48

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

Microsoft Academic Search

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

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

2006-01-01

49

Titan's Surface Composition from Cassini VIMS Solar Occultation Observations  

NASA Astrophysics Data System (ADS)

Titan's surface is obscured by a thick absorbing and scattering atmosphere, allowing direct observation of the surface within only a few spectral win-dows in the near-infrared, complicating efforts to identify and map geologi-cally important materials using remote sensing IR spectroscopy. We there-fore investigate the atmosphere's infrared transmission with direct measure-ments using Titan's occultation of the Sun as well as Titan's reflectance measured at differing illumination and observation angles observed by Cas-sini's Visual and Infrared Mapping Spectrometer (VIMS). We use two im-portant spectral windows: the 2.7-2.8-mm "double window" and the broad 5-mm window. By estimating atmospheric attenuation within these windows, we seek an empirical correction factor that can be applied to VIMS meas-urements to estimate the true surface reflectance and map inferred composi-tional variations. Applying the empirical corrections, we correct the VIMS data for the viewing geometry-dependent atmospheric effects to derive the 5-µm reflectance and 2.8/2.7-µm reflectance ratio. We then compare the cor-rected reflectances to compounds proposed to exist on Titan's surface. We propose a simple correction to VIMS Titan data to account for atmospheric attenuation and diffuse scattering in the 5-mm and 2.7-2.8 mm windows, generally applicable for airmass < 3.0. We propose a simple correction to VIMS Titan data to account for atmospheric attenuation and diffuse scatter-ing in the 5-mm and 2.7-2.8 mm windows, generally applicable for airmass < 3.0. The narrow 2.75-mm absorption feature, dividing the window into two sub-windows, present in all on-planet measurements is not present in the occultation data, and its strength is reduced at the cloud tops, suggesting the responsible molecule is concentrated in the lower troposphere or on the sur-face. Our empirical correction to Titan's surface reflectance yields properties shifted closer to water ice for the majority of the low-to-mid latitude area covered by VIMS measurements. Four compositional units are defined and mapped on Titan's surface based on the positions of data clusters in 5-mm vs. 2.8/2.7-mm scatter plots; a simple ternary mixture of H2O, hydrocarbons and CO2 might explain the reflectance properties of these surface units. The vast equatorial "dune seas" are compositionally very homogeneous, perhaps suggesting transport and mixing of particles over very large distances and/or and very consistent formation process and source material. The composi-tional branch characterizing Tui Regio and Hotei Regio is consistent with a mixture of typical Titan hydrocarbons and CO2, or possibly methane/ethane; the concentration mechanism proposed is something similar to a terrestrial playa lake evaporate deposit, based on the fact that river channels are known to feed into at least Hotei Regio.

McCord, Thomas; Hayne, Paul; Sotin, Christophe

2013-04-01

50

Molecular Epidemiology of VIM-4 Metallo-?-Lactamase-Producing Pseudomonas sp. Isolates in Hungary?  

PubMed Central

VIM metallo-?-lactamase-producing serotype O11 or O12 Pseudomonas aeruginosa isolates infecting or colonizing 19 patients from seven hospitals in Hungary were characterized between October 2003 and November 2005. Macrorestriction analysis revealed the involvement of hospitals from three different towns in northwest Hungary in an outbreak caused by VIM-4-producing P. aeruginosa. PMID:17000739

Libisch, Balázs; Muzslay, Mónika; Gacs, Mária; Minárovits, János; Knausz, Márta; Watine, Joseph; Ternák, Gábor; Kenéz, Éva; Kustos, Ildikó; Rókusz, László; Széles, Klára; Balogh, Boglárka; Füzi, Miklós

2006-01-01

51

The Saturnian satellite Rhea as seen by Cassini VIMS  

USGS Publications Warehouse

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

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

2012-01-01

52

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

USGS Publications Warehouse

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

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

2009-01-01

53

Remote sensing applications in marine science programs at VIMS  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

54

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

SciTech Connect

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

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

2012-10-01

55

VimA mediates multiple functions that control virulence in Porphyromonas gingivalis  

PubMed Central

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

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

2013-01-01

56

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

SciTech Connect

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

Blomquist, R.N.

1992-09-01

57

Equinoctial Activity Over Titan Dune Fields Revealed by Cassini/vims  

NASA Astrophysics Data System (ADS)

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.

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

58

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

NASA Astrophysics Data System (ADS)

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.

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

2010-03-01

59

VIMS spectral mapping observations of Titan during the Cassini prime mission  

USGS Publications Warehouse

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

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

2009-01-01

60

What happened to VIM thalamotomy for Parkinson's disease?  

PubMed

A prospective review of 75 of 190 parkinsonian patients undergoing unilateral thalamotomy was displayed with a computer graphics technique examining three equal consecutive groups from the pre-, early, and late L-dopa eras. Histograms for average function and scattergrams of individual patient's performance preoperatively and up to 2 years postoperatively were prepared. No ipsilateral effects or consistent iatrogenic deterioration of any function were identified. 2 years after surgery, 82% had no tremor in the contralateral fingers or hand and 7% had almost no tremor; contralateral tremor elsewhere was infrequent. Rigidity and manual dexterity improved less strikingly, the latter only reflecting abolition of tremor; locomotion, speech, facial movement and handwriting did not improve. There was no mortality, but 8% had persistent significant complications. VIM thalamotomy remains the treatment of choice for severe drug-resistant parkinsonian tremor. PMID:6367656

Tasker, R R; Siqueira, J; Hawrylyshyn, P; Organ, L W

1983-01-01

61

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

E-print Network

Abstract Observations from Cassini VIMS and ISS show localized but extensive surface brightenings in the wake of the 2010 September cloudburst. Four separate areas, all at similar latitude, show similar changes: Yalaing ...

Barnes, Jason W

62

Emitted Power Of Jupiter Based On Cassini CIRS And VIMS Observations  

NASA Technical Reports Server (NTRS)

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.

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

63

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

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

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

2013-09-20

64

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

65

Single-cycle powerful megawatt to gigawatt terahertz pulse radiated from a wavelength-scale plasma oscillator  

NASA Astrophysics Data System (ADS)

We propose a scheme to generate single-cycle powerful terahertz (THz) pulses by ultrashort intense laser pulses obliquely incident on an underdense plasma slab of a few THz wavelengths in thickness. THz waves are radiated from a transient net current driven by the laser ponderomotive force in the plasma slab. Analysis and particle-in-cell simulations show that such a THz source is capable of providing power of megawatts to gigawatts, field strength of MV/cm-GV/cm, and broad tunability range, which is potentially useful for nonlinear and high-field THz science and applications.

Wu, Hui-Chun; Sheng, Zheng-Ming; Zhang, Jie

2008-04-01

66

Control of Strong-Laser-Field Coupling to Electrons in Solid Targets with Wavelength-Scale Spheres  

SciTech Connect

Irradiation of a planar solid by an intense laser pulse leads to fast electron acceleration and hard x-ray production. We have investigated whether this high field production of fast electrons can be controlled by introducing dielectric spheres of well-defined size on the target surface. We find that the presence of spheres with a diameter slightly larger than half the laser wavelength leads to Mie enhancements of the laser field which, accompanied by multipass stochastic heating of the electrons, leads to significantly enhanced hard x-ray yield and temperature.

Sumeruk, H. A.; Kneip, S.; Symes, D. R.; Churina, I. V.; Belolipetski, A. V.; Ditmire, T. [Texas Center for High Intensity Laser Science, Dept. of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); Donnelly, T. D. [Physics Department, Harvey Mudd College, Claremont, California (United States)

2007-01-26

67

Spectral characteristics of the Titanian haze at 1-5 micron from Cassini/VIMS solar occultation data  

NASA Astrophysics Data System (ADS)

We retrieved optical-depth spectra of the Titanian haze in the range 1-5 ?m from solar occultation data obtained by the Cassini/Visual Infrared Mapping Spectrometer (VIMS) at altitudes of 59-502 km. Only limited wavelength intervals within this spectral range have been analyzed before. The haze spectra we retrieved are mostly similar to those of alkane particles (or powders), with three major absorption peaks typical of alkane powders at 2.3, 3.4, and 4.3 ?m. This result suggests that at least in the ~60-500 km altitude range, the Titanian haze is mostly composed of alkane particles, possibly with some trace impurities. The absence of the 3.0 and 4.6 ?m features excludes the molecules containing NH and CN bonds that are typical of laboratory-made tholins reported in the literature. The alkane-like spectral characteristics of the haze we observed at ~60-500 km differ from previous results obtained at different or overlapping altitudes: a) the presence of aromatic compounds derived from solar-pumped emissions observed at high altitude (600-1250 km) by Cassini/VIMS near 3.3 ?m; and b) the detection of HCN and NH3 in the cores of haze particles collected at low altitude (20-130 km) by the Huygens/Aerosol Collector and Pyrolyser (ACP). We suggest that these different characteristics arise from different structural layers formed by coagulation/coalescence during particle sedimentation. Data contained in Figs. 1 and 2 are only available in electronic form 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/557/L6

Kim, Sang J.; Courtin, Régis

2013-09-01

68

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

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 qac?E1-sul1. PMID:25331700

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

2015-01-01

69

Cloud structure of Jupiter’s troposphere from Cassini VIMS  

NASA Astrophysics Data System (ADS)

Cassini VIMS 4.5-5.1?m thermal emission spectra were used to study the composition and cloud structure of Jupiter’s middle troposphere during the 2000/2001 flyby. The radiance observed varies considerably across the planet (a factor of 50 between the warm North Equatorial Belt and the cool Equatorial Zone) but the spectral shape remains constant, suggesting the presence of a spectrally flat, spatially inhomogeneous cloud deck. Spectra were analysed using the NEMESIS radiative transfer code and retrieval algorithm. Both night- and day-side nadir spectra could be well reproduced using a model with a single, compact, grey cloud deck. For hotter spectra, this grey cloud could be located as deep as 3.0 bar, but the cooler spectra required the cloud deck to be at pressures of 1.2 bar or less. At these pressures, the clouds are expected to be NH4SH or NH3, but the single-scattering albedos of pure ices of NH3 or NH4SH produce spectral features that are incompatible with the VIMS data. These spectral signatures may be masked by complex rimming/coating processes, and/or by the presence of multiple cloud decks. Retrievals show that the cloud optical thickness varies significantly with latitude and longitude. The North Equatorial Belt contains discrete cloud-free “hot-spots” whose radiance is twice as bright as the coolest parts of the belt. The turbulent region in the wake of the Great Red Spot (GRS) has the thickest clouds of the South Equatorial Belt; these begin to thin out on the opposite hemisphere, 180° away from the GRS. The relatively low spectral resolution and model degeneracies mean that no variability could be detected (or ruled out) in the gaseous species (NH3, PH3 and other disequilibrium species). A limb darkening analysis was carried out using the nightside observations. Extreme inhomogeneity within latitude circles meant that simultaneous retrievals at different emission angles were not possible. However, forward modelling was used to show that highly scattering particles are required to produce results consistent with the data. Acceptable fits were obtained using cloud particles with high single-scatter albedos (?>0.85) and low asymmetry parameters (g<0.75).

Giles, Rohini S.; Fletcher, Leigh N.; Irwin, Patrick G.

2014-11-01

70

Isolation of VIM-2-producing Pseudomonas monteilii clinical strains Disseminated in a Tertiary Hospital in Northern Spain.  

PubMed

We describe the occurrence of blaVIM-2 in 10 carbapenem-resistant Pseudomonas monteilii strains isolated from different clinical samples in our hospital in Northern Spain. All the blaVIM-2-harbouring P. monteilii isolates possessed a class 1 integron, with the cassette array [intI1_blaVIM-2_aac(6' )-Ib_qacE?1_sul1]. Our results show the emergence of VIM-2-producing multidrug-resistant species other than P. aeruginosa or P. putida in a Spanish hospital. P. monteilii, though sporadically isolated, should also be considered as an important MBLs reservoir. PMID:25421471

Ocampo-Sosa, Alain A; Guzmán-Gómez, Laura P; Fernández-Martínez, Marta; Román, Elena; Rodríguez, Cristina; Marco, Francesc; Vila, Jordi; Martínez-Martínez, Luis

2014-11-24

71

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

NASA Astrophysics Data System (ADS)

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.

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

72

Titan's atmospheric and surface properties of the Ontario Lacus region from Cassini/VIMS remote sensing  

NASA Astrophysics Data System (ADS)

The existence of oceans or lakes of liquid hydrocarbons on Titan's surface was predicted more than 20 years ago. These would serve as a source of atmospheric methane and would also contain the end products of the photochemical reactions occurring high in the atmosphere. Although no oceans were ever found, lake-like features poleward of 70°N were first detected by the radar instrument onboard Cassini on July 2006. Before that, Cassini Imaging Science Subsystem (ISS) images of the south pole from June 2005 revealed an intriguing lake-like dark feature named Ontario Lacus. Recently an interesting and important result has been published about the identification of liquid ethane contained within Ontario Lacus (Brown et al. 2008). The authors analysed a near-infrared Visual and Infrared Mapping Spectrometer (VIMS) observation of the Ontario Lacus performed the 2007 December 4, during the T38 flyby. Their result needs nevertheless to be confirmed and improved using a more detailed methodology. Here we report on the analysis of this observation using a radiative transfer model (the libRadtran package) to simulate the atmospheric contribution. LibRadtran is a library of tools developed for radiative transfer calculations in the Earth's atmosphere, but adapted here to Titan's atmospheric conditions. Extinction sources were calculated for atmospheric methane and aerosols as a function of altitude and wavelength. Using the DISORT solver we were able to invert the surface spectrum of the lake interior and of an adjacent, non-lake region, in the near-infrared methane windows. The surface spectra were then compared with spectra of different ices and liquid hydrocarbons, yielding constraints on the possible constituents of Titan's lakes and their adjacent areas. Reference: Brown, R. et al. 2008. The identification of liquid ethane in Titan's Ontario Lacus, Nature 454, 607-610.

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

2009-04-01

73

Cassini-VIMS at Jupiter: Solar occultation measurements using Io  

USGS Publications Warehouse

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.

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

74

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

PubMed Central

A small but growing literature indicates that many animal colours are produced by combinations of structural and pigmentary mechanisms. We investigated one such complex colour phenotype: the highly chromatic wing colours of pierid butterflies including oranges, yellows and patterns which appear white to the human eye, but strongly absorb the ultraviolet (UV) wavelengths visible to butterflies. Pierids produce these bright colours using wing scales that contain collections of minute granules. However, to date, no work has directly characterized the molecular composition or optical properties of these granules. We present results that indicate these granules contain pterin pigments. We also find that pterin granules increase light reflection from single wing scales, such that wing scales containing denser granule arrays reflect more light than those with less dense granule collections. As male wing scales contain more pterin granules than those of females, the sexual dichromatism found in many pierid species can be explained by differences in wing scale pterin deposition. Additionally, the colour pattern elements produced by these pterins are known to be important during mating interactions in a number of pierid species. Therefore, we discuss the potential relevance of our results within the framework of sexual selection and colour signal evolution. PMID:17164199

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

2006-01-01

75

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

PubMed

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

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

2013-07-01

76

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)

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.

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

77

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

78

VimA-Dependent Modulation of Acetyl Coenzyme A Levels and Lipid A Biosynthesis Can Alter Virulence in Porphyromonas gingivalis  

PubMed Central

The Porphyromonas gingivalis VimA protein has multifunctional properties that can modulate several of its major virulence factors. To further characterize VimA, P. gingivalis FLL406 carrying an additional vimA gene and a vimA-defective mutant in a different P. gingivalis genetic background were evaluated. The vimA-defective mutant (FLL451) in the P. gingivalis ATCC 33277 genetic background showed a phenotype similar to that of the vimA-defective mutant (FLL92) in the P. gingivalis W83 genetic background. In contrast to the wild type, gingipain activity was increased in P. gingivalis FLL406, a vimA chimeric strain. P. gingivalis FLL451 had a five times higher biofilm-forming capacity than the parent strain. HeLa cells incubated with P. gingivalis FLL92 showed a decrease in invasion, in contrast to P. gingivalis FLL451 and FLL406, which showed increases of 30 and 40%, respectively. VimA mediated coenzyme A (CoA) transfer to isoleucine and reduced branched-chain amino acid metabolism. The lipid A content and associated proteins were altered in the vimA-defective mutants. The VimA chimera interacted with several proteins which were found to have an LXXTG motif, similar to the sorting motif of Gram-positive organisms. All the proteins had an N-terminal signal sequence with a putative sorting signal of L(P/T/S)X(T/N/D)G and two unique signatures of EXGXTX and HISXXGXG, in addition to a polar tail. Taken together, these observations further confirm the multifunctional role of VimA in modulating virulence possibly through its involvement in acetyl-CoA transfer and lipid A synthesis and possibly by protein sorting. PMID:22144476

Aruni, A. Wilson; Lee, J.; Osbourne, D.; Dou, Y.; Roy, F.; Muthiah, A.; Boskovic, D. S.

2012-01-01

79

The source of widespread 3-?m absorption in Jupiter’s clouds: Constraints from 2000 Cassini VIMS observations  

NASA Astrophysics Data System (ADS)

The Cassini flyby of Jupiter in 2000 provided spatially resolved spectra of Jupiter's atmosphere using the Visual and Infrared Mapping Spectrometer (VIMS). A prominent characteristic of these spectra is the presence of a strong absorption at wavelengths from about 2.9 ?m to 3.1 ?m, previously noticed in a 3-?m spectrum obtained by the Infrared Space Observatory (ISO) in 1996. While Brooke et al. (Brooke, T.Y., Knacke, R.F., Encrenaz, T., Drossart, P., Crisp, D., Feuchtgruber, H. [1998]. Icarus 136, 1-13) were able to fit the ISO spectrum very well using ammonia ice as the sole source of particulate absorption, Sromovsky and Fry (Sromovsky, L.A., Fry, P.M. [2010]. Icarus 210, 211-229), using significantly revised NH 3 gas absorption models, showed that ammonium hydrosulfide (NH 4SH) provided a better fit to the ISO spectrum than NH 3, but that the best fit was obtained when both NH 3 and NH 4SH were present in the clouds. Although the large FOV of the ISO instrument precluded identification of the spatial distribution of these two components, the VIMS spectra at low and intermediate phase angles show that 3-?m absorption is present in zones and belts, in every region investigated, and both low- and high-opacity samples are best fit with a combination of NH 4SH and NH 3 particles at all locations. The best fits are obtained with a layer of small ammonia-coated particles ( r ˜ 0.3 ?m) overlying but often close to an optically thicker but still modest layer of much larger NH 4SH particles ( r ˜ 10 ?m), with a deeper optically thicker layer, which might also be composed of NH 4SH. Although these fits put NH 3 ice at pressures less than 500 mb, this is not inconsistent with the lack of prominent NH 3 features in Jupiter's longwave spectrum because the reflectivity of the core particles strongly suppresses the NH 3 absorption features, at both near-IR and thermal wavelengths. Unlike Jupiter, Saturn lacks the broad 3-?m absorption feature, but does exhibit a small absorption near 2.965 ?m, which resembles a similar jovian feature and suggests that both planets contain upper tropospheric clouds of sub-micron particles containing ammonia as a minor fraction.

Sromovsky, L. A.; Fry, P. M.

2010-11-01

80

NASA Wavelength  

NSDL National Science Digital Library

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

2014-04-07

81

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

82

The surface composition of Iapetus: Mapping results from Cassini VIMS  

NASA Astrophysics Data System (ADS)

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-?m diameter particles consistent with nanophase hematite and nanophase iron. Spectral signatures of ice also indicate that sub-0.5-?m 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.

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

83

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

USGS Publications Warehouse

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.

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

84

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

Microsoft Academic Search

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

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

2011-01-01

85

THE COLLEGE OF WILLIAM AND MARY / VIMS PAYROLL DIRECT DEPOSIT AUTHORIZATION  

E-print Network

THE COLLEGE OF WILLIAM AND MARY / VIMS PAYROLL DIRECT DEPOSIT AUTHORIZATION Name (Please print authorize the College of William and Mary to initiate credit entries (deposits) and, if necessary, debit & National Defense) Return this form to: The College of William and Mary, Payroll Office, P.O. Box 8795

Zobin, Nahum

86

Center for Coastal Resources Management www.ccrm.vims.edu From the Wetlands Advisory  

E-print Network

not only an integrated approach to environmental management programs, but also the incorporation of social and those hosted by VIMS. Integrated Coastal & Shoreline Management Guidance Integrated coastal zone and economic issues. The disconnect between current management practices and the concept of integrated coastal

87

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

E-print Network

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

88

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

89

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

PubMed Central

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

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

2014-01-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

91

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

92

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

USGS Publications Warehouse

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

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

2007-01-01

93

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

USGS Publications Warehouse

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

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

2007-01-01

94

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

95

VIM-Based Dynamic Sparse Grid Approach to Partial Differential Equations  

PubMed Central

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

Mei, Shu-Li

2014-01-01

96

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

NASA Astrophysics Data System (ADS)

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.

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

97

Nosocomial infection by VIM-2 metallo-beta-lactamase-producing Pseudomonas putida.  

PubMed

Nosocomial infections caused by multidrug-resistant and carbapenem-resistant Pseudomonas putida isolates have been reported occasionally in severely ill or immunocompromised patients. Here we report the microbiological characteristics of what are believed to be the two first carbapenem-resistant VIM metallo-beta-lactamase (MBL)-producing P. putida strains in Spain, which were isolated from patients at the University Hospital Complex of Santiago de Compostela. Both patients were immunocompromised with severe underlying diseases and had been hospitalized for more than 15 days. One of them had previously been treated with a broad-spectrum therapy. Antimicrobial susceptibility testing showed that both strains were resistant to piperacillin/tazobactam, ceftazidime, cefepime, imipenem, meropenem, gentamicin, tobramycin, aztreonam, trimethoprim/sulfamethoxazole and ciprofloxacin, but sensitive to amikacin and colistin. For both isolates PCR and sequencing was positive for the bla(VIM-2) gene. Fingerprinting analysis revealed these were two different strains. One patient recovered clinically and one died; no direct link could be established between the isolation of P. putida and death. Our data expose the emergence of multidrug-resistant P. putida VIM-2 MBL, probably arising by independent horizontal transfer of resistance genes. So, although P. putida is not frequently isolated, it may survive easily in the hospital setting and occasionally cause difficult-to-treat nosocomial infections in severely ill patients. PMID:20360397

Treviño, M; Moldes, L; Hernández, M; Martínez-Lamas, L; García-Riestra, C; Regueiro, B J

2010-07-01

98

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

NASA Astrophysics Data System (ADS)

We apply a multivariate statistical method to Titan data acquired by different instruments onboard the Cassini spacecraft. We have searched through Cassini/VIMS hyperspectral cubes, selecting those data with convenient viewing geometry and that overlap with Cassini/RADAR scatterometry footprints with a comparable spatial resolution. We look for correlations between the infrared and microwave ranges the two instruments cover. Where found, the normalized backscatter cross-section obtained from the scatterometer measurement, corrected for incidence angle, and the calibrated antenna temperature measured along with the scatterometry echoes, are combined with the infrared reflectances, with estimated errors, to produce an aggregate data set, that we process using a multivariate classification method to identify homogeneous taxonomic units in the multivariate space of the samples. In medium resolution data (from 20 to 100 km/pixel), sampling relatively large portions of the satellite's surface, we find regional geophysical units matching both the major dark and bright features seen in the optical mosaic. Given the VIMS cubes and RADAR scatterometer passes considered in this work, the largest homogeneous type is associated with the dark equatorial basins, showing similar characteristics as each other on the basis of all the considered parameters. On the other hand, the major bright features seen in these data generally do not show the same characteristics as each other. Xanadu, the largest continental feature, is as bright as the other equatorial bright features, while showing the highest backscattering coefficient of the entire satellite. Tsegihi is very bright at 5 ?m but it shows a low backscattering coefficient, so it could have a low roughness on a regional scale and/or a different composition. Another well-defined region, located southwest of Xanadu beyond the Tui Regio, seems to be detached from the surrounding terrains, being bright at 2.69, 2.78 and 5 ?m but having a low radar brightness. In this way, other units can be found that show correlations or anti-correlations between the scatterometric response and the spectrophotometric behavior, not evident from the optical remote sensing data.

Tosi, F.; Orosei, R.; Seu, R.; Coradini, A.; Lunine, J. I.; Filacchione, G.; Gavrishin, A. I.; Capaccioni, F.; Cerroni, P.; Adriani, A.; Moriconi, M. L.; Negrão, A.; Flamini, E.; Brown, R. H.; Wye, L. C.; Janssen, M.; West, R. D.; Barnes, J. W.; Wall, S. D.; Clark, R. N.; Cruikshank, D. P.; McCord, T. B.; Nicholson, P. D.; Soderblom, J. M.; Cassini VIMS and RADAR Teams

2010-07-01

99

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

100

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)

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.

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

101

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

NASA Astrophysics Data System (ADS)

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

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

2007-10-01

102

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

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

103

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

E-print Network

Geomorphological significance of Ontario Lacus on Titan: Integrated interpretation of Cassini VIMS 14853, USA. Abstract Ontario Lacus is the largest lake of the whole southern hemisphere of Titan, Saturn of Ontario Lacus, based on a joint analysis of ISS, VIMS and RADAR SAR datasets, along with the T49

Brest, Université de

104

Emergence in Klebsiella pneumoniae and Enterobacter cloacae Clinical Isolates of the VIM-4 Metallo-?-Lactamase Encoded by a Conjugative Plasmid  

PubMed Central

Resistance to carbapenems is an emerging problem among gram-negative hospital pathogens. A transferable plasmid encoding the VIM-4 metallo-?-lactamase was detected in isolates of Klebsiella pneumoniae and Enterobacter cloacae obtained from a single patient under carbapenem therapy. Thus, enterobacteria appear to increasingly contribute to the spread of VIM-type enzymes. PMID:14742229

Luzzaro, Francesco; Docquier, Jean-Denis; Colinon, Céline; Endimiani, Andrea; Lombardi, Gianluigi; Amicosante, Gianfranco; Rossolini, Gian Maria; Toniolo, Antonio

2004-01-01

105

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

NASA Astrophysics Data System (ADS)

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

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

106

Method of Controlling Lasing Wavelength(s)  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

107

Synthesis of metallo-?-lactamase VIM-2 is associated with a fitness reduction in Salmonella enterica Serovar Typhimurium.  

PubMed

Antibiotic resistance, especially due to ?-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 ?-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-?-lactamase-producing Salmonella spp. PMID:25136026

Cordeiro, Nicolás F; Chabalgoity, José A; Yim, Lucía; Vignoli, Rafael

2014-11-01

108

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

109

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

USGS Publications Warehouse

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

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

2010-01-01

110

resistome analysis of Enterobacter cloacae CY01, an extensively drug-resistant strain producing VIM-1 metallo-?-lactamase from China.  

PubMed

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

Yang, Ling; Wu, Ai-Wu; Su, Dan-Hong; Lin, Yong-Ping; Chen, Ding-Qiang; Qiu, Yu-Rong

2014-10-01

111

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

NASA Astrophysics Data System (ADS)

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 6°±1°. 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 0.76±0.09 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.

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

112

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

USGS Publications Warehouse

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.

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

2009-01-01

113

Spectroscopic identification of Dione' and Rhea' terrain units using Cassini VIMS data  

NASA Astrophysics Data System (ADS)

Since July 2004, the Cassini spacecraft performed several observations of Saturn's icy satellites, allowing a better insight of their compositional and physical characteristics. The Visual and Infrared Mapping Spectrometer (VIMS) is a spectrometer onboard the Cassini Orbiter. In this work, we have selected 76 VIMS cubes of Dione and 166 cubes of Rhea in the infrared range 0.85-5.1 ?m. These data are characterized by a phase angle smaller than 50° and a good S/N ratio. After normalizing all data at ?=2.232 ?m to minimize photometric effects, we apply the supervised Spectral Angle Mapper (SAM) clustering technique to emphasize the existence of spectral units. Initially, for each satellite we define two end-members, respectively represented by one spectrum (one pixel) of a low-albedo terrain and one spectrum (one pixel) of a high-albedo terrain as seen at high spatial resolution. In the SAM method applied to remote sensing data, each spectrum is represented by a vector in the n-dimensional coordinate system, where n is the number of spectral channels. To compare the spectrum of each pixel of the target with the reference spectra selected a priori, the algorithm evaluates an angle ? that represents the separation between the vector of the reference spectrum (reference pixel) and the vector representing another pixel's spectrum in the data space. Small values of ? are indicative of a higher degree of similarity between the data. We set ?=0.1o as the maximum allowed angle value. In the cases detailed here, because two reference spectra/pixels show up to be not representative of the entire surface of the satellites, further a priori end-members are added until the whole surface as imaged by VIMS is properly classified. In particular, we select 9 and 12 different terrain types for Dione and Rhea, respectively. For both satellites, the infrared spectrum is dominated by the prominent signatures of H2O ice / OH bands at 1.5, 2.0 and 3.0 ?m. For Rhea the spectral signatures due to water ice at 1.04 and 1.25 ?m are observed on the overall surface, while for Dione these features are present just on a few percentage of the surface. A classification method applied to VIMS hyperspectral data is crucial to understand geochemical processes taking place on the surface of the icy satellites. The goal of this work is to investigate the possible presence on the surface of Dione and Rhea of non-water ice material, such as methane and ammonia. From the classification we find several spectral units on the two satellites characterized by different values of the spectral indices (e.g., water ice bands' depth, reflectance of the 3.6 ?m peak). Finally, some classes show also a peculiar trend with respect to the phase angle, possibly related to the physical structure of the surface constituents (e.g, average grain size of the surface regolith).

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

2012-04-01

114

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

USGS Publications Warehouse

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.

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

115

Potentially active regions on Titan: New processing of Cassini/VIMS data  

NASA Astrophysics Data System (ADS)

The Cassini Visual and Infrared Mapping Spectrometer (VIMS) obtained data of Titan's surface from flybys performed during the last seven years. In the 0.8-5.2 µm range, these spectro-imaging data showed that the surface consists of a multivariable geological terrain hosting complex geological processes. The data from the seven narrow methane spectral "windows" centered at 0.93, 1.08, 1.27, 1.59, 2.03, 2.8 and 5 µm provide some information on the lower atmospheric context and the surface parameters that we want to determine. Atmospheric scattering and absorption need to be clearly evaluated before we can extract the surface properties. We apply here a statistical method [1, 2] and a radiative transfer method [3, 1] on three potentially "active" regions on Titan, i.e. regions possibly subject to change over time (in brightness and/or in color etc) [4]: Tui Regio (20°S, 130°W) [5], a 1,500-km long flow-like figure, Hotei Regio (26°S, 78°W) [6], a 700-km wide volcanic-like terrain, and Sotra Facula (15°S, 42°W) [7], a 235-km in diameter area. With our method of Principal Component Analysis (PCA) we have managed to isolate specific regions of distinct and diverse chemical composition. We have tested this method on the previously studied Sinlap crater [8], delimitating compositional heterogeneous areas compatible with the published conclusions by Le Mouélic et al. (2008). Our follow-up method focuses on retrieving the surface albedo of the three areas and of the surrounding terrains with different spectral response by applying a radiative transfer (RT) code. We have used as input most of the Cassini HASI and DISR measurements, as well as new methane absorption coefficients [9], which are important to evaluate the atmospheric contribution and to allow us to better constrain the real surface alterations, by comparing the spectra of these regions. By superposing these results onto the PCA maps, we can correlate composition and morphology. As a test case, we used our RT code to verify the varying brightness of Hotei Regio reported by other investigators based on models lacking proper simulation of the atmospheric absorption [10]. Even though we have used exactly the same dataset, we did not detect any significant surface albedo variations over time; this led us to revise the definition of "active" regions: even if these regions have not visually changed over the course of the Cassini mission, the determination of the chemical composition and the correlation with the morphological structures [11] observed in these areas do not rule out that past and/or ongoing cryovolcanic processes are still a possible interpretation. [1] Solomonidou, A. et al. (2011). Potentially active regions on Titan: New processing of Cassini/VIMS data. In preparation. [2] Stephan, K. et al. (2008). Reduction of instrument-dependent noise in hyperspectral image data using the principal component analysis: Applications to Galileo NIMS data. Planetary and Space Science 56, 406-419. [3] Hirtzig, M. et al. (2011). Applications of a new methane linelist to Cassini/VIMS spectra of Titan in the 1.28-5.2 µm range . In preparation. [4] Wall, s. D. et al. (2009). Cassini RADAR images at Hotei Arcus and western Xanadu, Titan: Evidence for geologically recent cryovolcanic activity. Journal of Geophysical Research 36, L04203, [5] Barnes, J.W. et al. (2006). Cassini observations of flow-like features in western Tui Regio, Titan. Geophysical Research Letters 33, L16204. [6] Soderblom, L.A. et al. (2009). The geology of Hotei Regio, Titan: Correlation of Cassini VIMS and RADAR. Icarus 204, 610-618. [7] Lopes, R.M.C. et al. (2010). Distribution and interplay of geologic processes on Titan from Cassini radar data. Icarus 205, 540-558. [8] Le Mouélic et al. (2008). Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data. Journal of Geophysical Research 113, E04003. [9] Campargue, A. et al. (2011). An empirical line list for methane at 80 K and 296 K in the 1.26-1.71 µm region for planetary investigations.

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

2012-04-01

116

Electric Field and Plasma Density Observations of Long Wavelength Structures and Localized Packets of Short Scale Waves Associated with Sporadic-E Layers in the Presence of QP Radar Echoes  

NASA Astrophysics Data System (ADS)

Electric field and plasma density data gathered on sounding rockets launched in the presence of sporadic-E layers and QP radar echoes reveal a complex electrodynamics including both DC parameters and plasma waves detected over a large range of scales. We present results from two different sounding rocket experiments equipped with similar instrumentation which were conducted in the presence of intense QP radar echoes: a NASA sporadic-E investigation launched from Wallops Island, Va., in 1999 and the Japanese "SEEK-2" rocket launched from Uchinoura, Japan in 2002. Electric field data from both experiments reveal the presence of km-scale waves as well as well-defined packets of broadband (10's of meters to meters) irregularities. What is surprising is that in both experiments, neither the large scale nor short scale waves appear to be distinctly organized by the sporadic-E density layer. Data from the NASA rocket revealed large scale structures with wavelengths of 2-4 km and amplitudes of 1-2 mV/m that were most intense in the region of 90-110 km during the downleg trajectory of this flight. The waves were oriented in the NE-SW quadrants. On the other hand, during the SEEK-2 experiment, the electric field data above the sporadic-E layer on the upleg, from 110 km to the rocket apogee of 151 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10-15 km that also propagated between the NE-SW quadrants. The electric field structures had typical amplitudes of 3-5 mV/m with some excursions to 8-9 mV/m, and had associated perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and may have mapped upwards along the magnetic field from the sporadic-E region below. Candidate mechanisms to explain the origin of these structures include the Kelvin-Helmholtz instability and the Es Layer instability. In both cases, the same shear that formed the sporadic-E layer would presumably provide the energy to generate the km-scale structures. Other possibilities include a gravity wave explanation or a combination of these processes. The data suggest that these structures were associated with the lower altitude density striations that were the seat of the QP radar echoes observed simultaneously. The SEEK-2 structures may also have been associated with the mechanism responsible for a well-defined pattern of "whorls" in the neutral wind data that were revealed in a chemical trail released by a second sounding rocket launched 15 minutes later. Well-defined packets of higher frequency (shorter scales < 100 m) broadband waves were also observed in-situ on both rockets, consistent with the observations of intense radar backscatter during the times of each launch. The linear gradient drift instability involving the DC electric field and the vertical plasma gradient is shown to be incapable of driving most, although not all, of the short scale waves observed during each flight. The data suggest that other sources of free energy may have been important factors for wave growth, and we conclude that drift waves associated with winds and horizontal plasma density gradients, as well as thermal or other instabilities, are necessary to explain the short-scale wave generation observed during these sporadic-E encounters.

Pfaff, R. F.; Freudenreich, H.; Kudeki, E.; Larsen, M.

2006-05-01

117

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

118

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

PubMed Central

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

M, Jeya

2014-01-01

119

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

Microsoft Academic Search

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 mum to at least 4.1 mum. We propose that active thunderstorms originating in the 10-20 bar water-condensation region vertically transport dark materials at

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

2009-01-01

120

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

Microsoft Academic Search

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 10–20bar water-condensation region vertically transport dark materials at depth to the

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

2009-01-01

121

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

NASA Astrophysics Data System (ADS)

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

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

122

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

123

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

PubMed Central

The ability to combine physiology and engineering analyses with computer sciences has opened the door to the possibility of creating the "Virtual Human" reality. This paper presents a broad foundation for a full-featured biomechanical simulator for the human musculoskeletal system physiology. This simulation technology unites the expertise in biomechanical analysis and graphic modeling to investigate joint and connective tissue mechanics at the structural level and to visualize the results in both static and animated forms together with the model. Adaptable anatomical models including prosthetic implants and fracture fixation devices and a robust computational infrastructure for static, kinematic, kinetic, and stress analyses under varying boundary and loading conditions are incorporated on a common platform, the VIMS (Virtual Interactive Musculoskeletal System). Within this software system, a manageable database containing long bone dimensions, connective tissue material properties and a library of skeletal joint system functional activities and loading conditions are also available and they can easily be modified, updated and expanded. Application software is also available to allow end-users to perform biomechanical analyses interactively. Examples using these models and the computational algorithms in a virtual laboratory environment are used to demonstrate the utility of these unique database and simulation technology. This integrated system, model library and database will impact on orthopaedic education, basic research, device development and application, and clinical patient care related to musculoskeletal joint system reconstruction, trauma management, and rehabilitation. PMID:17343764

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

2007-01-01

124

The Long Wavelength Array  

Microsoft Academic Search

Application of self-calibration techniques to low-frequency (< 150 MHz) radio interferometric data has enabled high-resolution, high sensitivity imaging at long wavelengths for the first time. We illustrate these advances using NRAO Very Large Array (VLA) 74 MHz images having sub-arcminute resolution and sub-Jansky sensitivity. The VLA 74 MHz breakthrough has inspired the Long Wavelength Array (LWA), a completely electronic array

N. E. Kassim; E. J. Polisensky; T. E. Clarke; B. C. Hicks; P. C. Crane; K. P. Stewart; P. S. Ray; K. W. Weiler; L. J. Rickard; T. J. W. Lazio; A. S. Cohen; M. E. Nord; W. C. Erickson; R. A. Perley

2005-01-01

125

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

NASA Astrophysics Data System (ADS)

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

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

126

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

128

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

USGS Publications Warehouse

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.

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

2011-01-01

129

Long-wavelength equation for vertically falling films  

Microsoft Academic Search

An equation is derived for describing wave evolution on the surface of a vertically falling viscous film. The traditional long-wavelength scaling is replaced by a new scaling to reduce the two dimensional Navier-Stokes equations to a single evolution equation for the scaled film thickness h(x,t) . The scaling suggests that the Weber number ( We ) must be used instead

Mohan K. R. Panga; Ramesh R. Mudunuri; Vemuri Balakotaiah

2005-01-01

130

Long wavelength semiconductor lasers  

Microsoft Academic Search

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

G. P. Agrawal; N. K. Dutta

1986-01-01

131

Saturn's depths in a new light: Novel views of meteorology, circulation and dynamics by Cassini/VIMS  

NASA Astrophysics Data System (ADS)

The depths of Saturn below the ubiquitous covering of ammonia hazes have been revealed in detail by the Visual Infrared Mapping Spectrometer (VIMS) onboard the Cassini orbiter. Using Saturn's own indigenous glow produced by warm air at depth to back-light deep clouds, a diverse array of cloud features have been discovered near the 3-bar level, some 75 km underneath the ammonia clouds. Likely comprised of ammonia hydrosulfide, perhaps with a complement of water, the menagerie of deep cloud structures - including dozens of surprisingly narrow axisymmetric "zones", "smoke rings", a long-lived "string of pearls" spanning 1/4 of the planet, large plume-like and cyclonic features, and a deep-seated hexagonal feature circumscribing the north pole - reveal Saturn at depth to be a dynamic, meteorologically active planet much more like frenetic Jupiter than the classically serene face Saturn shows in sunlight. Additional information on Saturn's dynamically active nature is provided by daytime imagery of discrete clouds observed at the southpole - revealing two compositional types of clouds, suggesting a variety of upwelling phenomena - and the latitudinal variability of the trace disequilibrium gases arsine and phosphine observed in VIMS spectra.

Baines, Kevin; Momary, Thomas; Roos-Serote, Maarten; Showman, Adam; Atreya, Sushil K.; Brown, Robert H.; Buratti, Bonnie; Clark, Roger; Nicholson, Phillip

132

Scale  

ERIC Educational Resources Information Center

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…

Schaffhauser, Dian

2009-01-01

133

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

Microsoft Academic Search

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

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

2009-01-01

134

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

E-print Network

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

New Hampshire, University of

135

The Long Wavelength Array  

Microsoft Academic Search

Sub-arcminute resolution and sub-Jy sensitivity below 100 MHz is now being obtained on a routine basis using self-calibration or field-based calibration techniques with the 74 MHz system on the NRAO Very Large Array (VLA). The VLA 74 MHz breakthrough has inspired an emerging suite of new low frequency instruments, including the Long Wavelength Array (LWA), an electronic array planned to

E. Polisensky; N. Kassim; T. J. W. Lazio; K. Weiler; P. Crane; P. Ray; K. Stewart; B. Hicks; A. Cohen; W. Peters; M. Nord; W. C. Erickson

2004-01-01

136

Scales  

SciTech Connect

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

Murray Gibson

2007-04-27

137

Millimeter wavelength thermographic scanner.  

PubMed

Two new types of thermographic instruments sensitive to millimeter-wave electromagnetic radiation have been designed, constructed, and tested. These instruments utilize wavelengths that are three orders of magnitude longer and much more penetrating than those used in conventional infrared thermography. The instruments are capable of detecting apparent thermal variations as small as a fraction of a degree existing at tissue depths of several millimeters below the skin. By comparison, conventional IR thermographic units are limited to sampling radiation emitted only from the surface. The millimeter wave thermographic units are designed to contribute to the clinical detection of breast abnormalities with the specific aim of accurately and noninvasively detecting breast cancer. PMID:7322066

Cacak, R K; Winans, D E; Edrich, J; Hendee, W R

1981-01-01

138

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

USGS Publications Warehouse

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

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

2006-01-01

139

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

140

Monoclonal outbreak of VIM-1-carbapenemase-producing Enterobacter cloacae in intensive care unit, University Hospital Centre Split, Croatia.  

PubMed

Emergence of carbapenem-resistant Enterobacteriaceae has become a substantial global health problem. The aim of this study was to analyze carbapenem-resistant isolates of Enterobacter cloacae that have emerged for the first time in the intensive care unit (ICU) at the University Hospital Centre Split, Croatia. The strains were selected in the period between June and August 2012, according to their susceptibility patterns to carbapenems. Resistant isolates were screened for metallo-?-lactamase (MBL) production with the use of the imipenem-EDTA disk synergy test, and positive findings were confirmed by PCR. The type of VIM ?-lactamase gene was determined by sequencing of PCR products. The genetic relatedness was evaluated using pulsed-field gel electrophoresis analysis. The demographic and clinical data were retrospectively analyzed from medical records. Five patients were infected and one patient was colonized with a single clone of multidrug-resistant VIM-1-producing E. cloacae susceptible only to colistin. Three cases of lower respiratory tract infections, one case of bacteremia, and one case of intra-abdominal infection were identified. All cases were hospital-acquired after prolonged stay in ICU. All patients had serious underlying diseases and received a broad-spectrum antibiotic. Four patients died and two had unimprovable medical condition at the time of discharge from the hospital. MBL-producing E. cloacae can cause fatal infection in severely ill patients. Monoclonal outbreak highlights the need for continuous surveillance and good infection control practices to prevent further spread since the antibiotic therapy options for infections caused by such strains are strongly limited. PMID:24716493

Novak, Anita; Goic-Barisic, Ivana; Andrasevic, Arjana Tambic; Butic, Iva; Radic, Marina; Jelic, Marko; Rubic, Zana; Tonkic, Marija

2014-10-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

142

Wavelength meter having elliptical wedge  

DOEpatents

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

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

1992-01-01

143

Wavelength meter having elliptical wedge  

DOEpatents

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

Hackel, R.P.; Feldman, M.

1992-12-01

144

Outbreak of Carbapenem-Resistant Pseudomonas aeruginosa Producing VIM-8, a Novel Metallo-?-Lactamase, in a Tertiary Care Center in Cali, Colombia  

PubMed Central

The prevalence of imipenem resistance among Pseudomonas aeruginosa isolates at a 195-bed tertiary care medical center in Cali, Colombia, rose from 2% in 1996 to 28% in 1997 and to over 40% in 2003. Many isolates showed high-level multiresistance, and phenotypic characterization suggested the spread of a predominant strain with minor variants. Sixty-six resistant isolates collected between February 1999 and July 2003 from hospitalized patients (n = 54) and environmental samples (n = 12) were subjected to a fuller analysis. Genetic fingerprints were compared by pulsed-field gel electrophoresis (PFGE) of SpeI-digested genomic DNA, and blaIMP and blaVIM genes were sought by PCR. PFGE and serotyping indicated that 52 of the 66 isolates belonged to a single strain, with 82% similarity; the PFGE pattern for this organism was designated pattern A. Two further pairs of isolates represented single strains; the remaining nine isolates were unique, and in the case of one isolate, no satisfactory PFGE profile could be obtained. The pattern A isolates were mostly of serotype O12 and were highly resistant to imipenem (MICs, 32 to >256 ?g/ml), with this resistance decreased eightfold or more in the presence of EDTA. They yielded amplicons with blaVIM-specific primers, and sequencing of DNA from a representative isolate revealed blaVIM-8, a novel allele with three polymorphisms compared with the sequence of blaVIM-2. Two of these nucleotide changes were silent, but the third determined a Thr139Ala substitution. Only 4 of 13 resistant isolates (2 clinical isolates and 2 environmental isolates) assigned to other PFGE types carried blaVIM alleles, whereas the others were less multiresistant and mostly had lower levels of imipenem resistance (MICs, ?32 ?g/ml) which was not significantly reduced by EDTA. No blaIMP alleles were detected. During 2003, when the environmental study was undertaken, serotype O12 isolates with blaVIM were recovered from sinks and stethoscopes in the most-affected units, although not from the hands of staff; the problem declined once these reservoirs were disinfected and hygienic precautions were reinforced. PMID:15528701

Crespo, M. P.; Woodford, N.; Sinclair, A.; Kaufmann, M. E.; Turton, J; Glover, J.; Velez, J. D.; Castañeda, C. R.; Recalde, M.; Livermore, D. M.

2004-01-01

145

Atmospheric Seeing at Infrared Wavelengths  

NASA Astrophysics Data System (ADS)

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

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

1993-05-01

146

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

PubMed

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

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

2015-01-01

147

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

PubMed

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

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

2014-10-01

148

Keck long-wavelength spectrometer  

NASA Astrophysics Data System (ADS)

UCSD's IR astronomy group is building an imaging mid-IR spectrometer for the Keck Telescope. This instrument, the Long-Wavelength Spectrometer (LWS), is built around a 96 X 96 element, Si:As impurity band conduction array built by GenCorp Aerojet Electronics Systems Division. The LWS has low and moderate spectroscopy modes with nominal spectral resolutions of R (equals (lambda) /(Delta) (lambda) ) equals 100 and 1400 respectively, operating in the 10 micrometers (second order) and 20 micrometers (first order) ground- based atmospheric spectral windows. The LWS is also capable of direct imaging from 5 micrometers to 27 micrometers through a selection of 16 filters. For each of the spectroscopic modes and the direct imaging mode, the plate scale is 0.12 arcsec/pixel, which Nyquist samples the telescope's diffraction pattern at 10 micrometers . Because of the large light gathering power of the Keck Telescope and it's small diffraction pattern, the LWS will have unparalleled point source sensitivity, making it the premiere instrument for extragalactic and general faint-source mid-IR spectroscopy.

Jones, Barbara; Puetter, Richard C.

1993-10-01

149

The Exciting Wavelength of Extended Red Emission  

NASA Astrophysics Data System (ADS)

We propose to determine the wavelength of the photons which excite Extended Red Emission {ERE} by mapping the small scale structure of ERE and molecular hydrogen {H_2} in the reflection nebulae NGC 2023 and 7023. Both of these nebulae display sharp narrow ERE-filaments within photodissociation regions {PDR} which also show infrared H_2 fluorescence. In these opically thick filaments, different wavelength photons penetrate to different depths. By comparing the widths of these filaments in ERE and H_2 we will determine the exciting wavelength of ERE. This is possible because the combined opacity of dust and H_2 to the exciting radiation {lambda < 1100 A} of H_2 fluorescence is known, and the comparison of the thickness of the ERE and H_2 filaments will allow a determination of the dust opacity at the wavelength at which ERE is being excited. This is a sensitive test to distinguish between different materials which have been proposed as the carrier of ERE {e.g., carbon or silicon nanoparticles, polycyclic aromatic hydrocarbon molecules, hydrogenated amorphous carbon, etc.}, because the photoluminescense excitation spectra of these different materials differ by large amounts. Identifying the material which produces ERE is important as recent work on ERE in the diffuse interstellar medium has shown that the material which produces ERE comprises a significant component of dust grains.

Gordon, Karl

2003-07-01

150

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

USGS Publications Warehouse

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

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

2006-01-01

151

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

USGS Publications Warehouse

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

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

2012-01-01

152

Acoustofluidics 22: multi-wavelength resonators, applications and considerations.  

PubMed

One important niche for multi-wavelength resonators is the filtration of suspensions containing very high particle concentration. For some applications, multi-wavelength ultrasound enhanced sedimentation filters are second only to the centrifuge in efficiency but, unlike the centrifuge they are easily adapted for continuous flow. Multi-wavelength resonators are also an obvious consideration when half-wavelength chambers are too small for a specific application. Unfortunately the formula, bigger = higher-throughput, does not scale linearly. Here we describe the relationships between chamber size and throughput for acoustic, electrical, flow and thermal convection actions, allowing the user to define initial parameters for their specific applications with some confidence. We start with a review of some of the many forms of multi-wavelength particle manipulation systems. PMID:23291740

Hawkes, Jeremy J; Radel, Stefan

2013-02-21

153

Blackbody Radiation: Frequency and Wavelength  

NSDL National Science Digital Library

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

Palop, Jose I.

2010-12-12

154

A novel interferometric wavelength converter  

Microsoft Academic Search

The fiber Kerr effect employment in a wavelength conversion version, owing to low silica nonlinearity, has been prevented by the lack of an efficient interferometric architecture. A novel all-fiber wavelength converter is presented and characterized. The proposed scheme while taking advantage of the Kerr effect properties in standard communication optical fiber overcomes classical interferometric structure limitations, such as high environmental

Pierpaolo Boffi; Lucia Marazzi; Mario Martinelli

1999-01-01

155

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

USGS Publications Warehouse

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

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

2009-01-01

156

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

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

157

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

USGS Publications Warehouse

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

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

2007-01-01

158

Multiple-wavelength Raman lidar measurements of atmospheric water vapor  

SciTech Connect

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

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

1994-11-15

159

Multiple-wavelength tunable laser  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

160

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

USGS Publications Warehouse

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

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

2006-01-01

161

Towards short wavelengths FELs workshop  

SciTech Connect

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.

Ben-Zvi, I.; Winick, H.

1993-12-01

162

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

USGS Publications Warehouse

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

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

2006-01-01

163

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

165

What Wavelength Goes With a Color?  

NSDL National Science Digital Library

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

2009-09-30

166

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  

E-print Network

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 six years. Over the past two years, Fermi-LAT 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 VLBA monitoring revealed a brightening of the radio core, followed by the ejection of a superluminal knot. Since we observed the gamma-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 second gamma-ray flare 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, if we take the distance of the 43 GHz core from th...

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

2014-01-01

167

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)

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.

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

168

Solid colloidal optical wavelength filter  

DOEpatents

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.

Alvarez, Joseph L. (Boulder, CO)

1992-01-01

169

Power measurements at submillimetre wavelengths  

Microsoft Academic Search

Techniques for power measurements in the submillimeter wavelength region for lasers and similar sources are considered. Applications of submillimeter waves in plasma diagnostics, stratospheric monitoring, spectroscopy, radar and communications, component and system specification and design and spectroradiometry are indicated, and a distinction is made between continuum and narrow-band radiation sources. Examples of power measurement problems encountered for lasers and other

T. G. Blaney

1980-01-01

170

Long wavelength vertical cavity lasers  

Microsoft Academic Search

The need for low cost, high speed telecommunication sources demands the maturation of long wavelength vertical cavity lasers (VCLs). Both long haul fiber optic systems and gigabit ethernet links are potential markets for 1.3 and 1.55 micron VCLs. This past year has seen much progress to this end, but the emerging technology has yet to be determined. This paper overviews

K. A. Blacka; P. Abraham; A. Keating; Y. J. Chiu; E. L. Hu; J. E. Bowers

1999-01-01

171

Astronomical Images in Different Wavelengths  

NSDL National Science Digital Library

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

Foundation, Wgbh E.

2004-02-20

172

ON THE OPTICAL CONSTANTS OF METALS AT WAVELENGTHS SHORTER THAT THEIR CRITICAL WAVELENGTHS (1)  

E-print Network

154. ON THE OPTICAL CONSTANTS OF METALS AT WAVELENGTHS SHORTER THAT THEIR CRITICAL WAVELENGTHS (1 investigated in the extreme ultraviolet at wavelengths shorter than their critical wavelengths. It was found of electro- magnetic waves in a medium containing free charges is the existence of a critical wavelength Ã?c

Paris-Sud XI, Université de

173

Wavelength-multiplexed entanglement distribution  

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

174

Long wavelength carbonyl sulfide photodissociation  

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

175

Molecular astronomy at submillimeter wavelengths  

NASA Technical Reports Server (NTRS)

It is pointed out that the region of the spectrum from 300 to 3000 GHz (100 to 1000 microns), which is referred to as the submillimeter, is one of the least explored areas in the electromagnetic spectrum. The reasons for this situation are related to a lack of adequate instrumentation for detecting the radiation and an almost complete absorption of the radiation by the earth's atmosphere. The vast majority of the rotational transitions of molecules occur in the millimeter and submillimeter wavelength region of the spectrum. The strength of the lines increases at higher frequencies until a condition is reached in which the energy levels are no longer populated. The study of molecular clouds at submillimeter wavelengths promises to provide new important results. Attention is given to the design of suitable submillimeter receivers, problems of atmospheric transmission, and galactic molecular lines.

Buhl, D.

1984-01-01

176

Review of short wavelength lasers  

SciTech Connect

There has recently been a substantial amount of research devoted to the development of short wavelength amplifiers and lasers. A number of experimental results have been published wherein the observation of significant gain has been claimed on transitions in the EUV and soft x-ray regimes. The present review is intended to discuss the main approaches to the creation of population inversions and laser media in the short wavelength regime, and hopefully aid workers in the field by helping to provide access to a growing literature. The approaches to pumping EUV and soft x-ray lasers are discussed according to inversion mechanism. The approaches may be divided into roughly seven categories, including collisional excitation pumping, recombination pumping, direct photoionization and photoexcitation pumping, metastable state storage plus optical pumping, charge exchange pumping, and finally, the extension of free electron laser techniques into the EUV and soft x-ray regimes. 250 references.

Hagelstein, P.L.

1985-03-18

177

Laser wavelengths and oral implantology  

Microsoft Academic Search

In modern implant dentistry there are several clinical indications for laser surgery. Different laser systems have a considerable\\u000a spectrum of application in soft and hard peri-implant tissues. The literature was searched for clinical application of different\\u000a laser wavelengths in peri-implant tissues: second-stage surgery of submerged implants, treatment of infrabony defects, removal\\u000a of peri-implant hyperplastic overgrowths, and, possibly, the preparation of

George E. Romanos; Norbert Gutknecht; Sandra Dieter; Frank Schwarz; Roberto Crespi; Anton Sculean

2009-01-01

178

Wavelength-encoded OCDMA system using opto-VLSI processors.  

PubMed

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. PMID:17603568

Aljada, Muhsen; Alameh, Kamal

2007-07-01

179

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

E-print Network

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

Mueser, Martin

180

Measurement of thin films using very long acoustic wavelengths  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

181

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

NASA Technical Reports Server (NTRS)

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

Montano, J. W.

1987-01-01

182

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

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

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; Bonomo, Robert A

2014-10-01

183

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

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

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

2014-12-01

184

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

185

The Fine-Structure Constant and Wavelength Calibration  

NASA Astrophysics Data System (ADS)

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

Whitmore, Jonathan

186

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

PubMed Central

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

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

2011-01-01

187

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

NASA Astrophysics Data System (ADS)

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

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

1996-06-01

188

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

189

Multi-wavelength phase imaging interference microscopy  

Microsoft Academic Search

Multi-wavelength phase imaging interferography is a technique that combines phase-shifting interferometry with multi-wavelength phase unwrapping. It can be used to obtain phase profile of an object without 2pi ambiguities inherent to single wavelength phase images. In this technique, a Michelson-type interferometer is illuminated by an LED and the reference mirror is dithered for obtaining interference images at four phase quadratures,

Nilanthi Warnasooriya; Myung K. Kim

2006-01-01

190

Wavelength-doubling optical parametric oscillator  

DOEpatents

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

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

2007-07-24

191

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

PubMed Central

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

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

2014-01-01

192

Athermal Wavelength Filters toward Optical Interconnection to LSIs  

NASA Astrophysics Data System (ADS)

Photonic integrated circuits (PICs) produced by large-scale integration (LSI) on Si platforms have been intensively researched. Since thermal diffusion from the LSI logic layer is a serious obstacle to realizing a Si-based optical integrated circuit, we have proposed and realized athermal wavelength filters using Si slot waveguides embedded with benzocyclobutene (BCB). First, the athermal conditions were theoretically investigated by controlling the waveguide and gap width of the slot waveguides. In order to introduce the calculated waveguide structures to wavelength filters, the propagation losses and bending losses of the Si slot waveguides were evaluated. The propagation losses were measured to be 5.6 and 5.3dB/cm for slot waveguide widths of 500 and 700nm, respectively. Finally, athermal wavelength filters, a ring resonator, and a Mach-Zhender interferometer (MZI) with a slot waveguide width of 700nm were designed and fabricated. Further, a temperature coefficient of -0.9pm/K for the operating wavelength was achieved with the athermal MZI.

Atsumi, Yuki; Oda, Manabu; Kang, Joonhyun; Nishiyama, Nobuhiko; Arai, Shigehisa

193

Wavelength modulation spectroscopy using novel mechanical light chopper blade designs  

E-print Network

Wavelength modulation spectroscopy using novel mechanical light chopper blade designs Jayeeta wavelength modulation spectroscopy. The left and the right half of a beam emerging from a monochromator would periodic variation in the wavelength distribution, enabling wavelength modulation spectroscopy. In contrast

Ghosh, Sandip

194

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

NASA Astrophysics Data System (ADS)

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

Momary, Thomas W.; Baines, Kevin H.

2014-11-01

195

Optimum wavelengths for two color ranging  

NASA Technical Reports Server (NTRS)

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

Degnan, John J.

1993-01-01

196

The universe at infrared wavelengths  

NASA Technical Reports Server (NTRS)

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.

Beichman, C. A.

1988-01-01

197

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

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

198

Use of two wavelengths in microscopic TV holography for nondestructive testing  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

199

A plasmonic metal grating wavelength splitter  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

200

The MIT Short-Wavelength Laser Project: A Status Report  

SciTech Connect

The goal of the MIT Short-Wavelength Laser Project is to develop a small-scale, high repetition rate, EUV laser suitable for practical applications. The present report summarizes recent progress in this effort, both experimental and theoretical. Our experimental work has dealt with development of the pump laser, design of the target chamber and the associated target alignment system, investigation of short-wavelength laser cavities, and design of appropriate EUV diagnostics. Our theoretical work has included a study of the kinetics of transiently pumped laser plasmas, the development of efficient numerical algorithms applicable to laser-plasma rate equations, an investigation of frequency mixing in the EUV, and an analysis of x-ray detection using GaAs quantum-well structures.

Hagelstein, P.L.; Basu, S.; Muendel, M.H.; Braud, J.P.; Tauber, D.; Kaushik, S.; Goodberlet, J. (Massachusetts Inst. of Tech., Cambridge, MA (United States)); Hung, T.Y. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Maxon, S. (Lawrence Livermore National Lab., CA (United States))

1990-01-01

201

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

NASA Technical Reports Server (NTRS)

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

Montano, J. W.

1986-01-01

202

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

PubMed Central

Background Neck and shoulder complaints are common among employees in sedentary occupations characterized by intensive computer use. Specific strength training is a promising type of physical exercise for relieving neck and shoulder pain in office workers. However, the optimal combination of frequency and exercise duration, as well as the importance of exercise supervision, is unknown. The VIMS study investigates in a cluster randomized controlled design the effectiveness of different time wise combinations of specific strength training with identical accumulated volume, and the relevance of training supervision for safe and effective training. Methods/design A cluster randomized controlled trial of 20 weeks duration where employed office workers are randomized to 1 × 60 min, 3 × 20 min, 9 × 7 min per week of specific strength training with training supervision, to 3 × 20 min per week of specific strength training with a minimal amount of training supervision, or to a reference group without training. A questionnaire will be sent to 2000 employees in jobs characterized by intensive computer work. Employees with cardiovascular disease, trauma, hypertension, or serious chronic disease will be excluded. The main outcome measure is pain in the neck and shoulders at week 20. Trial Registration The trial is registered at ClinicalTrials.gov, number NCT01027390. PMID:20687940

2010-01-01

203

Outbreak due to a Klebsiella pneumoniae strain harbouring KPC-2 and VIM-1 in a German university hospital, July 2010 to January 2011.  

PubMed

We describe the epidemiology and characteristics of the pathogen and patients (n=7) associated with an outbreak of a carbapenem-resistant Klebsiella pneumoniae (CRKP) strain in a German university hospital from July 2010 to January 2011. Species identification and detection of carbapenem resistance were carried out using standard microbiological procedures. Carbapenemases were detected by phenotypic methods and specific polymerase chain reactions (PCRs). DNA fingerprinting profiles were performed with repetitive sequence-based PCR. Medical records of colonised or infected patients were retrospectively reviewed. Antibiotic resistance profiles, PCR-specific amplification products and genotyping demonstrated that the outbreak occurred because of the spread of a single CRKP clone harbouring both KPC-2 and VIM-1. Five of the seven patients had invasive infections with the CRKP strain; the deaths of four of them were directly related to the infection. Early implementation of infection control interventions brought about efficient containment of further cross-transmission. Rapid dissemination of carbapenemase-producing Enterobacteriaceae is a serious concern in patient care and is a problem that has emerged in western Europe. PMID:21871227

Steinmann, J; Kaase, M; Gatermann, S; Popp, W; Steinmann, E; Damman, M; Paul, A; Saner, F; Buer, J; Rath, Pm

2011-01-01

204

Use of imipenem to detect KPC, NDM, OXA, IMP, and VIM carbapenemase activity from gram-negative rods in 75 minutes using liquid chromatography-tandem mass spectrometry.  

PubMed

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

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

2014-07-01

205

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

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

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

2014-01-01

206

Extended measures for controlling an outbreak of VIM-1 producing imipenem-resistant Klebsiella pneumoniae in a liver transplant centre in France, 2003-2004.  

PubMed

We report the successful control of an outbreak caused by imipenem-resistant VIM-1-producing Klebsiella pneumoniae (IR-Kp) in France. This outbreak occurred in a care centre for abdominal surgery that includes a 15-bed liver intensive care unit and performs more than 130 liver transplantations per year. The index case was a patient with acute liver failure transferred from a hospital in Greece for urgent liver transplantation who was carrying IR-Kp at admission as revealed by routine culture of a rectal swab. Infection control measures were undertaken and included contact isolation and promotion of hand hygiene with alcohol-based hand rub solution. Nevertheless, secondary IR-Kp cases were identified during the six following months from 3 December 2003 to 2 June 2004. From 2 June to 21 October, extended infection control measures were set up, such as cohorting IR-Kp carriers, contact patients and new patients in distinct sections with dedicated staff, limiting ward admission, and strict control of patient transfer. They led to a rapid control of the outbreak. The global attack rate of the IR-Kp outbreak was 2.5%, 13% in liver transplant patients and 0.4% in the other patients in the care centre (p<0.005). Systematic screening for IR-Kp of all patients admitted to the care centre is still maintained to date and no secondary IR-Kp case has been detected since 2 June 2004. PMID:21144428

Kassis-Chikhani, N; Saliba, F; Carbonne, A; Neuville, S; Decre, D; Sengelin, C; Guerin, C; Gastiaburu, N; Lavigne-Kriaa, A; Boutelier, C; Arlet, G; Samuel, D; Castaing, D; Dussaix, E; Jarlier, V

2010-11-18

207

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

NASA Astrophysics Data System (ADS)

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

Montano, J. W.

1986-09-01

208

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

SciTech Connect

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.

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

2007-01-01

209

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

SciTech Connect

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

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

2010-12-16

210

Optical amplification at the 1. 31 wavelength  

DOEpatents

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.

Cockroft, N.J.

1994-02-15

211

Multimode fiber optic wavelength division multiplexing  

NASA Technical Reports Server (NTRS)

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.

Spencer, J. L.

1982-01-01

212

SHORT-WAVELENGTH ELECTROSTATIC FLUCTUATIONS IN THE SOLAR WIND  

SciTech Connect

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

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

2011-09-20

213

Single sub-wavelength aperture with greatly enhanced transmission  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

214

Multiple wavelength photolithography for preparing multilayer microstructures  

DOEpatents

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

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

2003-06-24

215

Apparatus for shifting the wavelength of light  

DOEpatents

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.

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

1983-01-01

216

Interferometric SOA-based cascaded wavelength conversion  

Microsoft Academic Search

SOA-based wavelength conversion is obtained in an interferometric device exploiting two synchronous cascaded conversion processes in a SLALOM followed by a nonlinear filter. An accurate analysis and experimental eye-diagrams demonstrate significant signal quality improvement.

Lucia Marazzi; Paola Parolari; Pierpaolo Boffi; Samuele Cozza; Mario Martinelli

2002-01-01

217

Holographic Wavelength Demultiplexer For Optical Fiber Communications  

NASA Astrophysics Data System (ADS)

In this paper optimized parameters of optical configuration of Holographic Wavelength Demultiplexer(HWD) has been obtained with aberration balancing. The wavefront aberration caused by wavelength shift has been minimized. The image size of a point source formed by HWD was found with ray tracing. For reducing the size of the image, we proposed a phase compensation function and calculated the image size. The phase compensation could be achieved by Computer-Generated Hologram(CGH).

Zuo, Xu; Ben, Wang; Zhi-ping, Fu; Da-hsiung, Hsu

1986-08-01

218

From Satellites to Rings: The Diversity of the Saturnian System Ices in the VIS-NIR at the End of Cassini-VIMS Nominal Mission  

NASA Astrophysics Data System (ADS)

After four years of nominal mission, VIMS has observed the whole population of Saturnian icy objects allowing a comparative analysis of the VIS-NIR spectral properties of the regular satellites (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus, Phoebe), minor moons (Atlas, Prometheus, Pandora, Janus, Epimetheus, Telesto, Calypso) and main rings (A, B, C and Cassini division). The results we present are derived from the whole dataset available at june 2008 which consists of about 1500 full-disk observations of the moons as well as several radial mosaics of the ring system. The most important spectrophotometric indicators (I/F continua, VIS spectral slopes, water and carbon dioxide IR bands strengths and positions) are calculated for each observation in order to identify the disk-integrated compositional units of the satellites, the distribution of water ice respect to "contaminants” abundances and typical regolith grain properties for both satellites and rings. These quantities are varying between the almost pure water ice surfaces of Enceladus and Calypso to the organic and carbon dioxide rich Hyperion, Iapetus and Phoebe. Some significant differences are detected in the VIS colors of co-orbital moons Epimetheus and Janus, with the first very red and therefore similar to Hyperion while the last is more "neutral” these results could help to decipher the origins and evolutional story of these two moons. The water ice band strengths of the A-B rings are the most intense of the Saturnian system denoting a minimal presence of "contaminants” which can be estimated thanks to the 350-520 nm spectral slope. Finally we compare these spectral parameters with some TNOs and outer solar system objects (1995UG5, 90377-Sedna, 1996TO66, Pholus, Triton, Charon, Oberon, Titania) to search for possible analogies. This research was possible thanks to the support of the Italian Space Agency (ASI).

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

2008-09-01

219

Evaluation of Double- and Triple-Antibiotic Combinations for VIM- and NDM-Producing Klebsiella pneumoniae by In Vitro Time-Kill Experiments  

PubMed Central

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

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

2014-01-01

220

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

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

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

2015-03-01

221

Millimeter wavelength spectroscopy and continuum studies of the planets  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

222

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

PubMed

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

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

2014-08-25

223

IR detectors with adaptive responsivity and wavelength  

NASA Astrophysics Data System (ADS)

Microbolometers and other thermal detectors have traditionally been limited to seeing objects in a broad wavelength band at a single sensitivity. Recent advances in interface heat transfer and optical cavity design promise to change that. In this paper, we present recent work on thermal infrared detectors with tunable responsivity and wavelength. First, we demonstrate that extended dynamic range in thermal detectors can be achieved by electrostatically bringing a portion of the detector support structure in contact with the substrate. The exact amount of heat transfer can be controlled by adjusting the contact area and pressure. The thermal conductance and responsivity can be switched more than an order of magnitude using this technique. Next, we demonstrate that a wavelength tunable device in the LWIR can be achieved by modifying the structure of a microbolometer to incorporate a modified Gires Tournois optical cavity. The cavity couples light at a single wavelength into the microbolometer while other wavelengths are rejected. We demonstrate that resonance can be tuned from 8.7 to 11.1 ?m with applied voltages from 0 to 42 V. The FWHM of the resonance can be switched between around 1.5 ?m in a narrow-band mode and 2.83 ?m in a broad-band mode.

Song, W.-B.; Talghader, J. J.

2007-02-01

224

Wavelength tuning of VECSELs by cavity geometry  

NASA Astrophysics Data System (ADS)

In this paper we report on the wavelength tuning of a VECSEL by changing the cavity geometry. The development and demonstration of a tunable high power single frequency Vertical External Cavity Surface Emitting Lasers (VECSEL) operating at various wavelengths from the UV to the IR region of the spectrum have been reported in many papers. However, it is important to understand that in many instances a precise lasing wavelength is required for proper operation. For example, VECSELs have been designed to specifically interact with the sodium spectral lines. If the VECSEL growth is not adequate, it may not be possible to reach the desired wavelength in a traditional cavity where the intracavity mode interacts with the VECSEL chip at normal incidence. Here we notice that if a fold angle is introduced at the VECSEL chip, a spectral blue shift occurs, and extended tunability may be possible. Therefore, by altering the cavity geometry it may be possible to further optimize a VECSEL design to obtain maximum output power at a desired wavelength.

Hessenius, Chris; Lukowski, Michal; Moloney, Jerome; Fallahi, Mahmoud

2012-03-01

225

Compact digital holoscope with dual wavelength  

NASA Astrophysics Data System (ADS)

Digital holography allows fast, nondestructive, full-field 3D measurement of reflecting as well as transmitting objects. It is a well-established two-step method of digital recording and numerical reconstruction of the full complex field of wavefront. It has found applications in diverse fields, such as micro-optics and MEMS metrology, cell imaging and particle characterization. However, for quantitative phase measurement there is 2? by phase ambiguities that limit measurements of optical path lengths to the wavelength of the illumination light. For continuous profiles, phase unwrapping is used to overcome the phase jumps. One approach is to use a synthetic wavelength using two lasers with different wavelengths. This synthetic wavelength would depend on the wavelengths of the two sources and thus can be tuned by selecting appropriate sources. In this paper, this concept is integrated into the compact digital holoscope which provides the system with the capability of measuring over a range of step heights from the nanometer to the micrometer realm. Applications of the system for reflecting geometries is discussed.

Di, Jianglei; Zhao, Jianlin; Asundi, Anand

2012-11-01

226

Cryogenic Amplifier Based Receivers at Submillimeter Wavelengths  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

227

Mechanisms and Methods for Selective Wavelength Filtering  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

228

Dynamic polarizabilities and magic wavelengths for dysprosium  

E-print Network

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 are a set of magic wavelengths of the unpoarized 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 which, near resonances, allows for the determination of approximate values of the magic wavelengths without calculating the dynamic polarizabilities of the excited states.

Dzuba, V A; Lev, Benjamin L

2010-01-01

229

Radio Wavelength Observatories within the Exploration Architecture  

E-print Network

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

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

2007-01-26

230

Dynamic polarizabilities and magic wavelengths for dysprosium  

SciTech Connect

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.

Dzuba, V. A.; Flambaum, V. V.; Lev, Benjamin L. [School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801-3080 (United States)

2011-03-15

231

Device for wavelength-selective imaging  

DOEpatents

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

Frangioni, John V. (Wayland, MA)

2010-09-14

232

Effects of Laser Wavelength on Ablator Testing  

NASA Technical Reports Server (NTRS)

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.

White, Susan M.

2014-01-01

233

Short wavelength ion temperature gradient turbulence  

SciTech Connect

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

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

2012-10-15

234

Dual-wavelength adaptive optical systems.  

PubMed

A method for decomposition of phase difference error between measurements of atmospheric turbulence-induced phase distortion at two different wavelengths is described. Calculations are made of the phase difference errors in the first five Zernike radial modes for both ground-to-ground and ground-to-space transmission of laser radiation. It is found that the phase difference error compared with the uncorrected wavefront phase error is relatively insignificant in the first (tilt) Zernike mode but increases in significance with the order of the Zernike mode. Relative phase difference error is also found to depend on transmitted and received wavelengths, aperture diameter, propagation path, and strength of turbulence. PMID:18200255

Winocur, J

1983-12-01

235

Modulation compression for short wavelength harmonic generation  

SciTech Connect

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.

Qiang, J.

2010-01-11

236

An economic Fabry-Perot wavelength reference  

NASA Astrophysics Data System (ADS)

Precision radial velocity (PRV) measurements are key in studying exoplanets, and so are wavelength calibrators in PRV instruments. ThAr lamps offer an affordable but somewhat limited solution for the visible passband. Laser frequency combs are ideal calibrators, except the (still) narrow wavelength coverage and large price tag. White light Fabry-Perot (FP) calibrators offer frequency-comb like properties in a more affordable and less complicated package1. Using a commercial solid FP etalon and off-the shelf components we have constructed an economic FP calibrator suitable for observatories on a smaller budget.

F?rész, Gábor; Glenday, Alex; Latham, Christian

2014-07-01

237

Wavelength Calculator Applet Version 2.0  

NSDL National Science Digital Library

Created by Professor Umberto Ravaioli at the University of Illinois, and presented by the NanoEd Resource Portal, the Wavelength Calculator java applet "provides an interactive way to explore the spectrum of electromagnetic radiation and evaluate the wavelength by varying the frequency." The site has detailed instructions on how to use the calculator with clear illustrations and the general formulas that the calculator uses. The calculator itself requires a java plug-in which is standard on most recent browsers. This tool is a handy one for students and researchers in nanoscience or physics environments.

Ravaioli, Umberto

2012-04-23

238

Predicting Ripple Wavelength in Wave-Current Flows  

NASA Astrophysics Data System (ADS)

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.

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

2006-12-01

239

The Variability of Sagittarius A* at Centimeter Wavelengths  

E-print Network

We present the results of a 3.3-year project to monitor the flux density of Sagittarius A* at 2.0, 1.3, and 0.7 cm with the VLA. The fully calibrated light curves for Sgr A* at all three wavelengths are presented. Typical errors in the flux density are 6.1%, 6.2%, and 9.2% at 2.0, 1.3, and 0.7 cm, respectively. There is preliminary evidence for a bimodal distribution of flux densities, which may indicate the existence of two distinct states of accretion onto the supermassive black hole. At 1.3 and 0.7 cm, there is a tail in the distribution towards high flux densities. Significant variability is detected at all three wavelengths, with the largest amplitude variations occurring at 0.7 cm. The rms deviation of the flux density of Sgr A* is 0.13, 0.16, and 0.21 Jy at 2.0, 1.3, and 0.7 cm, respectively. During much of this monitoring campaign, Sgr A* appeared to be relatively quiescent compared to results from previous campaigns. At no point during the monitoring campaign did the flux density of Sgr A* more than double its mean value. The mean spectral index of Sgr A* is alpha=0.20+/-0.01, with a standard deviation of 0.14. The spectral index appears to depend linearly on the observed flux density at 0.7 cm with a steeper index observed during outbursts. This correlation is consistent with the expectation for outbursts that are self-absorbed at wavelengths of 0.7 cm or longer and inconsistent with the effects of simple models for interstellar scintillation. Much of the variability of Sgr A*, including possible time lags between flux density changes at the different wavelengths, appears to occur on time scales less than the time resolution of our observations (8 days). Future observations should focus on the evolution of the flux density on these time scales.

R. M. Herrnstein; J. -H. Zhao; G. C. Bower; W. M. Goss

2004-02-24

240

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

E-print Network

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

Yu, Edward T.

241

Resolving the Moth at Millimeter Wavelengths  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

242

RESOLVING THE MOTH AT MILLIMETER WAVELENGTHS  

SciTech Connect

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

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

2013-09-01

243

Meter wavelength radio astronomy in Chile  

Microsoft Academic Search

Current meter-wavelength research at Maipu consists largely of a galactic survey for the southern sky, a search for secondary calibration sources, pulsar studies, a search for atmospheric pulses from Saturn, and the continuing investigation of Jovian S bursts above 30 MHz.

J. May; F. Reyes; H. Alvarez; J. Aparici; T. Carr; J. Phillips; J. Levy; G. Lebo

1986-01-01

244

Dual wavelength laser thermal processing of semiconductors  

SciTech Connect

By employing a dual wavelength laser source and tailoring the time delay between pulses at the two wavelengths to take advantage of the strong temperature dependence of the absorption coefficient for the initially less-strongly absorbed wavelength, the annealing of ion-implantation damage in semiconductors by laser irradiation may be optimized. A solid-state laser emitting high-intensity pulses at 0.53 micrometers and 1.06 micrometers was used in this study in conjunction with an optical fiber delay line to examine the annealing characteristics of an As-implanted silicon solar cell wafer. By varying the length of fiber and thereby varying the delay between pulses of the two wavelengths, it was determined that at 25 nsec delay, the sample surface is preheated by the 0.53 micrometers radiation to provide optimal coupling for the following 1.06 micrometers radiation. These results are in agreement with a theoretical model based on melting and liquid phase epitaxial regrowth. Caculations based on this model are presented.

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

1980-06-30

245

Surface profilometry by wavelength scanning Fizeau interferometer  

Microsoft Academic Search

We have applied wavelength scanning interferometry to Fizeau interferometer for surface profilometry. This interferometer is free from ambiguity of the sign in the measurement result. It is more compact in setup than the Michelson interferometer used previously. Experimental results from a step and a dip on a mirror surface are shown. In the focal depth of imaging system, we could

Akihiro Yamamoto; Ichirou Yamaguchi

2000-01-01

246

Discrete wavelength-locked external cavity laser  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

247

An Update on the Long Wavelength Array  

Microsoft Academic Search

The Long Wavelength Array (LWA), a SKA Pathfinder, will be a new multi-purpose radio telescope operating in the frequency range 10-88 MHz. Scientific programs include pulsars, supernova remnants, general transient searches, radio recombination lines, solar and Jupiter bursts, investigations into the \\

Gregory B. Taylor; S. E. Tremblay; Y. Pihlstrom; J. Craig; L. Rickard; J. Dowell; N. Kassim; T. Clarke; B. Hicks; E. Polisensky; P. Ray; H. Schmitt; D. Woods; J. Hartman; S. Ellingson; C. Wolfe; R. Navarro; E. Sigman; M. Soriano; F. Owen

2011-01-01

248

Minimal Wavelength Assignment in Survivable Mesh Networks  

E-print Network

1 Minimal Wavelength Assignment in Survivable Mesh Networks Richard S. Barr Mark W. Lewis Southern Methodist University ©1999,2000 Richard Barr, Mark W. Lewis #12;2 Telecommunications Networks Identification Spare Capacity Allocation (MODCAP) · Kennington & Lewis approach: #12;12 Minimum Modular Spare

Barr, Richard

249

Wavelength Agility in Multihop Lightwave Networks  

Microsoft Academic Search

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

Jean-françois P. Labourdette; Anthony S. Acampora

1990-01-01

250

All-fiber Kerr wavelength converter  

Microsoft Academic Search

The authors present a novel fibre wavelength converter architecture based on the joint use of Kerr phase modulation and interferometric conversion where drawbacks are greatly reduced. The proposed interferometric architecture maintains all the advantages of the Kerr effect band phase modulation in fiber while assuring a very low operation noise

L. Marazzi; P. Boffi; M. Martinelli

1998-01-01

251

SDIO long wavelength infrared detector requirements  

NASA Technical Reports Server (NTRS)

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.

Duston, Dwight

1990-01-01

252

Wavelength tracking with thermally controlled silicon resonators  

E-print Network

, high-speed silicon electro-optic modulator," Opt. Express 17(25), 22484­22490 (2009). 3. M. R. Watts, D shift and the drift of laser wavelength. This feedback control scheme allows microring- based electro-optic modulators to be used in a dynamic environment. ©2011 Optical Society of America OCIS codes: (130

Mellor-Crummey, John

253

The wavelength dependence of Triton's light curve  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

254

Narrowband multiple wavelengths filter in aperiodic optical superlattice  

Microsoft Academic Search

We report on a theoretical analysis for the narrowband multiple wavelengths filter in aperiodic optical superlattice (AOS). The sequences of the opposite domains in AOS are optimized to realize the prescribed multiple wavelengths filtering using simulated annealing (SA) algorithm. Two, three and four wavelengths narrowband filters at telecommunication wavelength (near 1550 nm) are presented. The full width at half maximum

Xi Gu; Xianfeng Chen; Yuping Chen; Xianglong Zeng; Yuxing Xia; Yingli Chen

2004-01-01

255

Multi-wavelength injection seeded mid-infrared optical parametric oscillator for DIAL  

SciTech Connect

We have constructed and fielded a multi-wavelength injection seeded mid-IR OPO source for DIAL. This OPO system was built for ground based remote sensing measurements of species with both broad (300 cm{sup -1}) and narrow absorption bandwidths (0.07 cm{sup -1} FWHM). The OPO utilizes a single frequency tunable diode laser for the injection seeded signal wavelength in the region from 6400 to 6700 cm{sup -1} and an angle phase-matched 5 cm LiNbO3 crystal to provide large tuning excursions on a slow time scale. The pump was a diode pumped Nd:YAG MOPA (9398 cm{sup -1}) running at 180 Hz. This pump source was repeatedly injection seeded with a different wavelength on each of film sequential shots forming a set of three pulses having wavelength separations on the order of 0.4 cm{sup -1} at a three color set repetition rate of 60 Hz. This combination of OPO signal and pump source produced a set of three time staggered idler wavelengths separated by 0.4 cm{sup -1} with the center wavelength tunable from 2700 to 3000 cm{sup -1}. This OPO system was used in field test experiments to detect the release of chemicals from a standoff distance of 3.3 Km. We present key OPO design criteria, performance data, and numerical simulations that agree with our observations of pump induced spectral impurities in the OPO output.

Webb, M.S.; Stanion, K.B.; Deane, D.J. [and others

1996-01-27

256

Alternative explanation for intermediate--wavelength magnetic anomalies  

SciTech Connect

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.

Shure, L.; Parker, R.L.

1981-12-10

257

Wavelength Calibration of the Hamilton Echelle Spectrograph  

NASA Astrophysics Data System (ADS)

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

Pakhomov, Yu. V.; Zhao, G.

2013-10-01

258

WAVELENGTH CALIBRATION OF THE HAMILTON ECHELLE SPECTROGRAPH  

SciTech Connect

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

Pakhomov, Yu. V. [Institute of Astronomy, Russian Academy of Sciences, Moscow (Russian Federation); Zhao, G., E-mail: pakhomov@inasan.ru [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2013-10-01

259

Radio Wavelength Transients: Current and Emerging Prospects  

E-print Network

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

J. Lazio

2008-01-18

260

Discrete Wavelength-Locked External Cavity Laser  

NASA Technical Reports Server (NTRS)

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

Pilgrim, Jeffrey S.; Silver, Joel A.

2004-01-01

261

Wavelength-tunable spasing in the visible.  

PubMed

A SPASER, short for surface plasmon amplification by stimulated emission of radiation, is key to accessing coherent optical fields at the nanoscale. Nevertheless, the realization of a SPASER in the visible range still remains a great challenge because of strong dissipative losses. Here, we demonstrate that room-temperature SPASER emission can be achieved by amplifying longitudinal surface plasmon modes supported in gold nanorods as plasmon nanocavities and utilizing laser dyes to supply optical gain for compensation of plasmon losses. By choosing a particular organic dye and adjusting the doping level, the resonant wavelength of the SPASER emission can be tuned from 562 to 627 nm with a spectral line width narrowed down to 5-11 nm. This work provides a versatile route toward SPASERs at extended wavelength regimes. PMID:23915034

Meng, Xiangeng; Kildishev, Alexander V; Fujita, Koji; Tanaka, Katsuhisa; Shalaev, Vladimir M

2013-09-11

262

Multi-Wavelength Observations of Supernova Remnants  

NASA Technical Reports Server (NTRS)

Supernova remnants (SNRs) provide a laboratory for studying various astrophysical processes, including particle acceleration, thermal and non thermal emission processes across the spectrum, distribution of heavy elements, the physics of strong shock waves, and the progenitor systems and environments of supernovae. Long studied in radio and X-rays, the past decade has seen a dramatic increase in the detection and subsequent study of SNRs in the infrared and gamma-ray regimes. Understanding the evolution of SNRs and their interaction with the interstellar medium requires a multi-wavelength approach. I will review the various physical processes observed in SNRs and how these processes are intertwined. In particular, I will focus on X-ray and infrared observations, which probe two very different but intrinsically connected phases of the ISM: gas and dust. I will discuss results from multi-wavelength studies of several SNRs at various stages of evolution, including Kepler, RCW 86, and the Cygnus Loop.

Williams, B.

2012-01-01

263

Polarizabilities, Atomic Clocks, and Magic Wavelengths  

NASA Astrophysics Data System (ADS)

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

Safronova, Marianna

2008-05-01

264

Estimation of Snow Parameters from Dual-Wavelength Airborne Radar  

NASA Technical Reports Server (NTRS)

Estimation of snow characteristics from airborne radar measurements would complement In-situ measurements. While In-situ data provide more detailed information than radar, they are limited in their space-time sampling. In the absence of significant cloud water contents, dual-wavelength radar data can be used to estimate 2 parameters of a drop size distribution if the snow density is assumed. To estimate, rather than assume, a snow density is difficult, however, and represents a major limitation in the radar retrieval. There are a number of ways that this problem can be investigated: direct comparisons with in-situ measurements, examination of the large scale characteristics of the retrievals and their comparison to cloud model outputs, use of LDR measurements, and comparisons to the theoretical results of Passarelli(1978) and others. In this paper we address the first approach and, in part, the second.

Liao, Liang; Meneghini, Robert; Iguchi, Toshio; Detwiler, Andrew

1997-01-01

265

Deformable mirror for short wavelength applications  

DOEpatents

A deformable mirror compatible with short wavelength (extreme ultraviolet) radiation that can be precisely controlled to nanometer and subnanometer accuracy is described. Actuators are coupled between a reaction plate and a face plate which has a reflective coating. A control system adjusts the voltage supplied to the actuators; by coordinating the voltages supplied to the actuators, the reflective surface of the mirror can be deformed to correct for dimensional errors in the mirror or to produce a desired contour.

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

1999-01-01

266

Varactor diodes for millimeter and submillimeter wavelengths  

NASA Technical Reports Server (NTRS)

Whisker-contacted GaAs Schottky barrier varactor diodes are the most common high-frequency multiplier element in use today. They are inherently simple devices that have very high frequency response and have been used to supply local oscillator power for Schottky heterodyne receivers to frequencies approaching 700 GHz. This paper discusses the development of improved varactor diode technology for space based applications at millimeter and submillimeter wavelengths.

Rizzi, Brian J.; Hesler, Jeffrey L.; Dossal, Hasan; Crowe, Thomas W.

1992-01-01

267

Using large radio telescopes at decametre wavelengths  

Microsoft Academic Search

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

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

2004-01-01

268

Thermal behavior of millimeter wavelength radio telescopes  

Microsoft Academic Search

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

Albert Greve; Michel Dan; Juan Penalver

1992-01-01

269

CW seeded optical parametric amplifier providing wavelength and pulse duration tunable nearly transform limited pulses.  

PubMed

An optical parametric amplifier that delivers nearly transform limited pulses is presented. The center wavelength of these pulses can be tuned between 993 nm and 1070 nm and, at the same time, the pulse duration is varied between 206 fs and 650 fs. At the shortest pulse duration the pulse energy was increased up to 7.2 microJ at 50 kHz repetition rate. Variation of the wavelength is achieved by applying a tunable cw seed while the pulse duration can be varied via altering the pump pulse duration. This scheme offers superior flexibility and scaling possibilities. PMID:20174154

Hädrich, S; Gottschall, T; Rothhardt, J; Limpert, J; Tünnermann, A

2010-02-01

270

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

PubMed Central

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

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

2009-01-01

271

Multiple wavelength X-ray monochromators  

DOEpatents

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

Steinmeyer, P.A.

1992-11-17

272

Multiple wavelength X-ray monochromators  

DOEpatents

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

Steinmeyer, Peter A. (Arvada, CO)

1992-11-17

273

Wavelength meter having single mode fiber optics multiplexed inputs  

DOEpatents

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.

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

1993-02-23

274

Wavelength meter having single mode fiber optics multiplexed inputs  

DOEpatents

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.

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

1993-01-01

275

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

PubMed Central

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

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

2014-01-01

276

Snapshot Mueller matrix polarimeter by wavelength polarization coding  

E-print Network

Snapshot Mueller matrix polarimeter by wavelength polarization coding Matthieu Dubreuil, Sylvain of our knowledge, experimental configuration of Mueller matrix polarimeter based on wavelength. Anastasiadou, E. Deléchelle, and A. De Martino, "Registration scheme suitable to Mueller matrix imaging

Boyer, Edmond

277

Frequency-wavelength calculator with table of dielectric properties  

NASA Technical Reports Server (NTRS)

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.

Thompson, L. L.

1972-01-01

278

Laser-to-electricity energy converter for short wavelengths  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

279

Fizeau wavemeter for pulsed laser wavelength measurement  

NASA Technical Reports Server (NTRS)

A Fizeau wavelength meter optimized for use with pulsed laser sources has been developed and characterized which demonstrates a CW resolution better than 2 parts in 10 to the 7th and a pulsed resolution better than 1 part in 10 to the 6th. The static optical design is based on a Fizeau wedge interferometer, which together with spatial filtering and collimating optics is used to produce a pattern of parallel fringes which is imaged on a linear photodiode array and analyzed by a minicomputer. A series of CW and pulsed measurements of various narrowband laser sources are described, and particular difficulties involved in pulsed laser measurements with the wavemeter are examined.

Morris, M. B.; Mcilrath, T. J.; Synder, J. J.

1984-01-01

280

High efficiency CCD detectors at UV wavelengths  

NASA Astrophysics Data System (ADS)

The Faint Intergalactic Redshifted Emission Balloon (FIREBall) is a NASA/CNES balloon-borne ultraviolet multi-object spectrograph designed to observe the diffuse gas around galaxies (the circumgalactic medium) via line emission redshifted to ~205 nm. FIREBall uses a ultraviolet-optimized delta doped e2v CCD201 with a custom designed high efficiency five layer anti-reflection coating. This combination achieves very high quantum efficiency (QE) and photon-counting capability, a first for a CCD detector in this wavelength range. We also present new work on red blocking mirror coatings to reduce red leak.

Hamden, Erika T.; Jewell, April D.; Gordon, Samuel; Hennessy, John; Hoenk, Michael E.; Nikzad, Shouleh; Schiminovich, David; Martin, D. Christopher

2014-07-01

281

Decoherence induced by long wavelength gravitons  

E-print Network

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.

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

2014-12-15

282

SAGE 3: A visible wavelength limb sounder  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

283

Quasi-optical diplexer for millimeter wavelengths.  

PubMed

A quasi-optical diplexer for injection of signal and local oscillator frequencies into a mixer at millimeter wave-lengths is described. The diplexer accepts both image and signal bands, presents low loss at both the signal and local oscillator frequencies and rejects local oscillator noise at the signal frequency. The configuration of the device makes it particularly useful for Cassegrain receivers using a cooled mixer and a lens corrected feed system. The diplexer has been tested at 150 GHz on the 11-m radio telescope operated by The National Radio Astronomy Observatory in Tucson, Arizona. PMID:18699048

Payne, J M; Wordeman, M R

1978-12-01

284

Novel algorithms for wavelength converters placement in wavelength-routed network  

NASA Astrophysics Data System (ADS)

In this paper, the placement problem of wavelength converters in DWDM (Dense Wavelength Division Multiplexing) networks with arbitrary topologies is investigated. We could settle the problem easily by considering the two sub-problems of routing selecting and converter placement simultaneously. A reasonable path algorithm in which load balance and shortest path are considering together was proposed. Based on this model, we presented three simple algorithms A,B and C for wavelength converter placement. Simulation results on the basic characteristic of converter placement of EON and NSFNET are presented. With the three algorithms, the cost (including routing selecting and placement of WC) of optimizing network has been greatly reduced but the blocking performance has not been reduced.

Xu, Hao; Zhang, Xinliang; Liu, Deming; Huang, Dexiu

2005-02-01

285

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

PubMed

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

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

2014-08-25

286

Wavelength-Division Multiplexing Of Bipolar Digital Signals  

NASA Technical Reports Server (NTRS)

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."

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

1994-01-01

287

Fast Ethernet Restoration based on Alternative Wavelength Paths  

Microsoft Academic Search

We propose and we experimentally demonstrate a novel fast restoration method for Gigabit Ethernet based on the wavelength recovery. It permits to route the wavelength of a broken link in another existing ling exploiting the wavelength division multiplexing of the fibre. Such a procedure is obtained by means of an optical switch, driven by a Loss of Light signal generated

Francesco Matera; L. Rea; M. Venezia; L. Capanna; G. Pierri; G. Del Prete

2007-01-01

288

WAVELENGTH CONVERSION USING BISMUTH-BASED NONLINEAR OPTICAL LOOP MIRROR  

E-print Network

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

Wai, Ping-kong Alexander

289

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

290

Short wavelength topography on the inner-core boundary  

PubMed Central

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

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2007-01-01

291

Resolving The Moth at Millimeter Wavelengths  

E-print Network

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 (SMA) observations of the debris disk around HD 61005 at a spatial resolution of 1.9 arcsec 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. 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 constr...

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

2013-01-01

292

Progress in extended wavelength VCSEL technology  

NASA Astrophysics Data System (ADS)

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 10?sec.

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

2013-03-01

293

A wavelength tunable 2-ps pulse VECSEL  

NASA Astrophysics Data System (ADS)

We report a mode-locked Vertical-External-Cavity Surface-Emitting Laser (VECSEL) that exhibits 13.7 nm of tuning around a centre wavelength of 1042 nm. The wavelength tuning is achieved by incorporating an uncoated, 25 ?m thick, fused silica etalon into the cavity of the laser at Brewster's angle. The etalon is then tilted with respect to the cavity axis. The etalon has a calculated free spectral range of 14 nm at normal incidence. The repetition rate of the laser is measured to be 1.88 GHz. The pulse duration, averaged over the tuning range, is 1.9 ps corresponding to a mean time bandwidth product of 0.46. For a sech2 pulse this is 1.46 times larger than the transform limit. The average power of the laser does not fall below 2.6 mW and, over the tuning range, averages 3.5 mW. With appropriate amplification, such a laser would be highly suited to the generation of heralded single photons in photonic crystal fibre.

Morris, Oliver J.; Wilcox, Keith G.; Head, C. Robin; Turnbull, Andrew P.; Mosley, Peter J.; Quarterman, Adrian H.; Kbashi, Hani J.; Farrer, Ian; Beere, Harvey E.; Ritchie, David A.; Tropper, Anne C.

2012-03-01

294

Wavelength-shift-free Mamyshev regenerator  

NASA Astrophysics Data System (ADS)

Optical regeneration is a key technology for next generation high-speed optical networks. All-optical regeneration can increase the reach of transmission systems without expensive optical-to-electrical signal conversion. Among various regeneration schemes, the Mamyshev regenerator attracted particular attention due to its simplicity and robustness. In this paper, we report an all-optical regeneration of a 40 Gbit/s return-to-zero signals. The regenerator proposed is based on the standard Mamyshev regenerator, which the temporal intensity profile and the average power are recovered. This device allows regenerating the signal without wavelength shift, decreasing the complexity and cost when compared with others 2-R regenerators reported. The input signal is first spectrally broadened, by self-phase modulation, after passing through a highly nonlinear fiber. Afterwards, the signal is amplified by a bidirectional erbium doped fiber amplifier, and offset spectral backscattering sliced by a fiber Bragg grating. In the second stage, the signal is spectral broadening and filtered recovering the input wavelength. The transfer function for the regenerator proposed is measured, and the all-optical regeneration is assessed by means of bit-error-rate measurements as well as real-time observation of the signal.

Fernandes, Gil M.; Tiburcio, Bruno; Muga, Nelson J.; Pinto, Armando N.

2013-11-01

295

Study of All-Optical Wavelength Conversion and Regeneration Subsystems for use in Wavelength Division  

E-print Network

the signal to noise ratio (SNR). Chromatic dispersion affects the pulse shape, while different types, the noise properties of the converted signal generated by the four-wave mixing based wavelength conversion are based on the non-linear four-wave mixing process which occurs when fields with proper spectral and power

Kouroupetroglou, Georgios

296

Absolute brightness temperature measurements at 3.5-mm wavelength. [of sun, Venus, Jupiter and Saturn  

NASA Technical Reports Server (NTRS)

Careful observations have been 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 - 4.7 K), and Saturn (153.4 + or - 4.8 K) with a standard error of about three percent. This is a significant improvement in accuracy over previous results at millimeter wavelengths. A stable transmitter and novel superheterodyne receiver were constructed and used to determine the effective collecting area of the Millimeter Wave Observatory (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.

Ulich, B. L.; Rhodes, P. J.; Davis, J. H.; Hollis, J. M.

1980-01-01

297

Selection of remote sensing techniques - Surface roughness information from 3 cm wavelength SLAR images  

NASA Technical Reports Server (NTRS)

The value of SLAR (Side-Looking Airborne Radar) image data for detecting and measuring small-scale surface roughness is examined, using as an example the Cottonball Basin in Death Valley National Monument, California. The SLAR image was obtained by an X-band (3 cm wavelength) synthetic aperture radar system operated at an altitude of 10,732 m above sea level. The polarization of the transmitted and received signals was horizontal. Film density values were used to produce color hypsometric maps of small-scale surface irregularities. It is shown that semi-quantitative surface roughness information, from uniquely flat surfaces such as the Cottonball Basin, can be obtained by analysis of 3 cm wavelength SLAR images calibrated by limited field measurements. Quantitative roughness data could be obtained with proper consideration of modifying surface and radar system parameters.

Schaber, G. G.; Berlin, G. L.; Pitrone, D. J.

1976-01-01

298

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

DOEpatents

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.

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

2002-01-01

299

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

300

Teachers' Domain: Astronomical Images in Different Wavelengths  

NSDL National Science Digital Library

This item is an interactive set of astronomical images produced from four types of telescopes: radio, infrared, x-ray, and visible-light. Image sets include the Milky Way, the crab nebula, a supernova, and the most luminous star in our galaxy. The organization of the images allows students to easily compare how the various telescopes detect different wavelengths of electromagnetic radiation. This collection was produced especially for Teachers' Domain, and includes background information, questions for classroom discussion, and content standards. Teachers' Domain is an NSF-funded pathway of the National Science Digital Library (NSDL). It is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2009-06-18

301

Short Wavelength Chemical Laser (SWCL) Workshop  

NASA Astrophysics Data System (ADS)

The workshop was held for the purpose of identifying the government's interest in SWCL technology, reviewing past and present efforts in this area and presenting the government's plans for a new thrust in SWCL source development. In addition, the workshop was to provide a forum for interaction between members of the Strategic Defense Initiation Organization (SDIO) and the 6.1 agencies with the technical community in order to create an enthusiastic response to the SWCL thrust and to generate new concepts as well as to involve new participants in this technically challenging area. This document contains abstracts of papers presented at the workshops. Some of the topics discussed in the sessions include: HF Lasers - What have we learned?; Chemical Oxygen Iodine Laser Review; Why So FEw Chemical Lasers?; Approach to Efficient Short-Wavelength Chemical Lasers; Metal/Oxidizer Systems; Pyrotechnic Systems; Metastable State Production; Metastable Transfer Systems; Energy Exchange Mechanisms.

Watt, W.

1984-12-01

302

Design Of Long Wavelength Telecommunication Systems  

NASA Astrophysics Data System (ADS)

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

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

1983-08-01

303

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

PubMed Central

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

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

2014-01-01

304

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

SciTech Connect

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

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

2012-05-01

305

Information-theoretic method for wavelength selection in bioluminescence tomography  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

306

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

NASA Astrophysics Data System (ADS)

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

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

2003-09-01

307

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

PubMed

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

Sahin, Levent; Figueiro, Mariana G

2013-05-27

308

Using Guide Wavelengths to Assess Far-Infrared Laser Emissions  

NASA Astrophysics Data System (ADS)

An optically pumped molecular laser system with a transverse excitation scheme has been used to observe 77 guide wavelengths associated with the modes of an oversized waveguide laser resonator. These guide wavelengths, spanning from 102.6 to 990.6 ?m, were generated by a variety of lasing media, including methanol along with several symmetric- and asymmetric-top molecules. The guide wavelengths displayed several consistent characteristics when compared with their respective fundamental laser emissions: their wavelengths were about 0.47 % larger and their relative powers were at least a factor of ten weaker. The properties of these guide wavelengths were used to assess frequency and wavelength measurements associated with known far-infrared laser emissions. For several of these laser emissions, this prompted a reinvestigation and subsequent revision of their measured values. Five far-infrared laser frequencies were also measured for the first time.

DeShano, B.; Olivier, K.; Cain, B.; Zink, L. R.; Jackson, M.

2015-01-01

309

Using Guide Wavelengths to Assess Far-Infrared Laser Emissions  

NASA Astrophysics Data System (ADS)

An optically pumped molecular laser system with a transverse excitation scheme has been used to observe 77 guide wavelengths associated with the modes of an oversized waveguide laser resonator. These guide wavelengths, spanning from 102.6 to 990.6 ?m, were generated by a variety of lasing media, including methanol along with several symmetric- and asymmetric-top molecules. The guide wavelengths displayed several consistent characteristics when compared with their respective fundamental laser emissions: their wavelengths were about 0.47 % larger and their relative powers were at least a factor of ten weaker. The properties of these guide wavelengths were used to assess frequency and wavelength measurements associated with known far-infrared laser emissions. For several of these laser emissions, this prompted a reinvestigation and subsequent revision of their measured values. Five far-infrared laser frequencies were also measured for the first time.

DeShano, B.; Olivier, K.; Cain, B.; Zink, L. R.; Jackson, M.

2014-09-01

310

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

311

Broadband wavelength conversion of incoherent light in silicon nanowaveguides  

Microsoft Academic Search

We demonstrate broadband wavelength conversion of an incoherent light source via four-wave mixing in a silicon rib nanowaveguide. We observe a conversion efficiency of -24 dB over the entire wavelength range of the incoherent source. OCIS codes: (190.4380) Nonlinear optics, four-wave mixing; (130.7405) Wavelength conversion devices While the telecom band has benefited greatly from readily available sources and detectors, the

Ryan K. W. Lau; Yoshitomo Okawachi; Michael Menard; Michal Lipson; Alexander L. Gaeta

2011-01-01

312

Opto-VLSI-based N × M wavelength selective switch.  

PubMed

In this paper, we propose and experimentally demonstrate a novel N × M wavelength selective switch (WSS) architecture based on the use of an Opto-VLSI processor. Through a two-stage beamsteering process, wavelength channels from any input optical fiber port can be switched into any output optical fiber port. A proof-of-concept 2 × 3 WSS structure is developed, demonstrating flexible wavelength selective switching with an insertion loss around 15 dB. PMID:23938686

Xiao, Feng; Alameh, Kamal

2013-07-29

313

Limited-Range Wavelength Translation in All-Optical Networks  

Microsoft Academic Search

This paper examines wavelength translation in allopticalwavelength-routed networks. Previous studies[4-7] have shown that wavelength translation canimprove the blocking performance of these networks.However, all previous work [4-7] has assumed thatwavelength translators can translate from any inputwavelength to any output wavelength. In contrast, allopticalwavelength translators demonstrated in the laboratoryto date [9-11] are, in general, only capable oflimited translation. In this...

Jennifer M. Yates; Jonathan P. R. Lacey; David Everitt; Mark Summerfield

1996-01-01

314

Wavelength resolved UV photodesorption and photochemistry of CO2 ice.  

PubMed

Over the last four years we have illustrated the potential of a novel wavelength-dependent approach in determining molecular processes at work in the photodesorption of interstellar ice analogs. This method, utilizing the unique beam characteristics of the vacuum UV beamline DESIRS at the French synchrotron facility SOLEIL has revealed an efficient indirect desorption mechanism that scales with the electronic excitations in molecular solids. This process, known as DIET--desorption induced by electronic transition--occurs efficiently in ices composed of very volatile species (CO, N2), for which photochemical processes can be neglected. In the present study, we investigate the photodesorption energy dependence of pure and pre-irradiated CO2 ices at 10-40 K and between 7 and 14 eV. The photodesorption from pure CO2 is limited to photon energies above 10.5 eV and is clearly initiated by CO2 excitation and by the contribution of dissociative and recombination channels. The photodesorption from "pre-irradiated" ices is shown to present an efficient additional desorption pathway below 10 eV, dominating the desorption depending on the UV-processing history of the ice film. This effect is identified as an indirect DIET process mediated by photoproduced CO, observed for the first time in the case of less volatile species. The results presented here pinpoint the importance of the interconnection between photodesorption and photochemical processes in interstellar ices driven by UV photons having different energies. PMID:25302397

Fillion, J H; Fayolle, E C; Michaut, X; Doronin, M; Philippe, L; Rakovsky, J; Romanzin, C; Champion, N; Oberg, K I; Linnartz, H; Bertin, M

2014-01-01

315

Array of Bolometers for Submillimeter- Wavelength Operation  

NASA Technical Reports Server (NTRS)

A feed-horn-coupled monolithic array of micromesh bolometers is undergoing development for use in a photometric camera. The array is designed for conducting astrophysical observations in a wavelength band centered at 350 m. The bolometers are improved versions of previously developed bolometers comprising metalized Si3N4 micromesh radiation absorbers coupled with neutron- transmutation-doped Ge thermistors. Incident radiation heats the absorbers above a base temperature, changing the electrical resistance of each thermistor. In the present array of improved bolometers (see figure), the thermistors are attached to the micromesh absorbers by indium bump bonds and are addressed by use of lithographed, vapor-deposited electrical leads. This architecture reduces the heat capacity and minimizes the thermal conductivity to 1/20 and 1/300, respectively, of earlier versions of these detectors, with consequent improvement in sensitivity and speed of response. The micromesh bolometers, intended to operate under an optical background set by thermal emission from an ambient-temperature space-borne telescope, are designed such that the random arrival of photons ("photon noise") dominates the noise sources arising from the detector and readout electronics. The micromesh is designed to be a highly thermally and optically efficient absorber with a limiting response time of about 100 s. The absorber and thermistor heat capacity are minimized in order to give rapid speed of response. Due to the minimization of the absorber volume, the dominant source of heat capacity arises from the thermistor.

Bock, James; Turner, Anthony

2007-01-01

316

The dusty Universe: astronomy at infrared wavelengths  

NASA Astrophysics Data System (ADS)

The last twenty years have shown ever more convincingly that most of the star formation activity in the universe is enshrouded in dust. Half of the energy and most of the photons pervading intergalactic space come from the infrared (IR) spectral region. In this review, I describe briefly what has been discovered with IRAS, ISO, and now Spitzer, and look ahead toward the recently launched IR satellite, Herschel, and the future JWST. The focus is extragalactic, mainly star-forming galaxies, and on diagnostics to distinguish them from galaxies hosting active nuclei. I will illustrate the importance of IR wavelengths for probing dust-enshrouded starbursts, quantifying physical processes in the interstellar medium, and measuring star-formation density across cosmic time. Particular attention will be paid to trends with metal abundance; studying how stars form in nearby metal-poor galaxies can help understand the transition between primordial star formation in metal-free environments and the chemically evolved starbursts in the Local Universe.

Hunt, L. K.

317

The millimeter wavelength emissivity in IC5146  

NASA Astrophysics Data System (ADS)

We have observed a core in the northern streamer of the IC5146 cloud using the MPIfR 19-channel Bolometer system on the IRAM 30m telescope at a wavelength of 1.2mm. We smoothed our observations to the same angular resolution (30'') as a new map of the NIR extinction of this cloud (Lada, Alves, and Lada 1998) and in this way obtained direct measurements of the ratio of millimeter emissivity to dust extinction. Our results are compatible with a ratio of the visual extinction coefficient kappa_V to the 1.2mm grain absorption coefficient kappa_ {1.2} of (4+/- 2) x 10(4) . This is in good agreement with the theoretical predictions for bare interstellar grains (Draine & Lee 1984; Mathis 1990). Within the errors our measurements are also consistent with recent models of grains with ice mantles whose size distribution has been modified due to coagulation but whose millimeter emissivities are not a strong function of grain size (Ossenkopf & Henning 1994). We find that the ratio of millimeter grain emissivity to visual extinction varies roughly inversely with the visual extinction over our map and interpret this as implying a gradient in dust temperature from roughly 8K in the core interior (A_V>20mag) to 20K in regions of low (5mag) extinction. One consequence of our result is that the 1.2mm intensity, by itself, is not a good tracer of mass in this cloud.

Kramer, C.; Alves, J.; Lada, C.; Lada, E.; Sievers, A.; Ungerechts, H.; Walmsley, M.

1998-01-01

318

Visible-wavelength semiconductor lasers and arrays  

DOEpatents

A visible semiconductor laser. The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1.lambda.) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%.

Schneider, Jr., Richard P. (Albuquerque, NM); Crawford, Mary H. (Albuquerque, NM)

1996-01-01

319

Visible-wavelength semiconductor lasers and arrays  

DOEpatents

The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1{lambda}) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%. 5 figs.

Schneider, R.P. Jr.; Crawford, M.H.

1996-09-17

320

FORBIDDEN AND INTERCOMBINATION LINES OF RR TELESCOPII: WAVELENGTH MEASUREMENTS AND ENERGY LEVELS  

SciTech Connect

Ultraviolet and visible spectra of the symbiotic nova RR Telescopii are used to derive reference wavelengths for many forbidden and intercombination transitions of ions +1 to +6 of elements C, N, O, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, and Ca. The wavelengths are then used to determine new energy values for the levels within the ions' ground configurations or first excited configuration. The spectra were recorded by the Space Telescope Imaging Spectrograph of the Hubble Space Telescope and the Ultraviolet Echelle Spectrograph of the European Southern Observatory in 2000 and 1999, respectively, and cover 1140-6915 A. Particular care was taken to assess the accuracy of the wavelength scale between the two instruments. An investigation of the profiles of the emission lines reveals that the nebula consists of at least two plasma components at different velocities. The components have different densities, and a simple model of the lines' emissions demonstrates that most of the lines principally arise from the high density component. Only these lines were used for the wavelength study.

Young, P. R. [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States); Feldman, U. [Artep Inc., Ellicott City, MD 21042 (United States); Lobel, A. [Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussels (Belgium)

2011-10-01

321

All-optical polymeric interferometeric wavelength converter comprising an excited state intramolecular proton transfer dye  

NASA Astrophysics Data System (ADS)

We designed and demonstrated an all-optical wavelength converter using a polymeric Mach-Zehnder interferometer (MZI) comprised of an excited state intramolecular proton transfer (ESIPT) dye, 2,2'-{oxybis[4-(4-methoxyphenyl)quinoline-6,2-diyl]}bis(5-methoxyphenol) (MQ). This MZI wavelength converter is composed of the MQ dye-doped polymeric waveguide and a thick light blocking metal film. A feature of this device is that one arm of the MZI can be irradiated by 355 nm pulses (signal beam), while the other arm was not, thus allowing a differential phase shift in the submicrosecond time scale. Because of the refractive index change of the ESIPT dye in one arm of interferometer upon irradiation with the signal beam, phase modulation of the continuous-wave probe light propagating in the irradiated arm of the MZI takes place, leading to the intensity modulation at the output defined by the signal beam, resulting in an all-optical wavelength converter, that is, the conversion of the signal modulation to output signal modulation of the probe light of the MZI. The characteristics of the wavelength converter are well described by a simple kinetic model.

Kang, Jae-Wook; Kim, Sehoon; Park, Soo Young; Kim, Jang-Joo

2004-05-01

322

Saturn's aurora observed by Cassini camera in visible wavelengths  

NASA Astrophysics Data System (ADS)

Cassini camera's movies in 2009-2013 show Saturn's aurora in both the northern and southern hemispheres. The color of the aurora changes from pink at a few hundreds of km above the cloud tops to purple at 1000-1500 km above the cloud tops. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with the laboratory simulated auroras [1]. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs, sometimes a spiral around the pole, and sometimes double arcs at 70-75(°) both north and south latitude. 10,000-km-scale longitudinal brightness structures can persist for more than 100 hours. This structures rotate together with Saturn. Besides the steady structure, the auroras brighten suddenly on the timescales of few minutes. 1000-km-scale disturbances may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The persistence of the longitudinal structure of the aurora in two long observations in 2009 and 2012 allowed us to estimate its period of rotation of 10.65 ± 0.15 h for 2009 and 10.8± 0.1 h for 2012. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time. The 2012 south aurora period is longer than any SKR periods detected at the time, but it is similar to the SKR period of the south branch of SKR periods in 2004-2008. These periods are also close to the rotation period of the lightning storms on Saturn. We discuss those periodicities and their relevance to Saturn's internal rotation. [1] Aguilar, A. et al. The Electron-Excited Mid-Ultraviolet to Near-Infrared Spectrum of H_2: Cross Sections and Transition Probabilities. Astrophys. J. Supp. Ser. 177, 388-407 (2008).

Dyudina, Ulyana; Porco, Carolyn; Ingersoll, Andrew; Ewald, Shawn; Wellington, Danika

323

Investigating short wavelength correlated errors on low resolution mode altimetry  

NASA Astrophysics Data System (ADS)

Although conventional radar altimetry products (Jason1, Jason2, LRM CRYOSAT2, etc) have a spatial resolution as high as 300 m, the observation of ocean scales smaller than 100 km is limited by the existence of a "spectral hump", i.e. a geographically coherent error. In the frame of the future altimetry missions (SAR for Cryosat -2 and Sentinel-3 missions and interferometry for the SWOT mission) it becomes crucial to investigate again and to better understand the signals obtained at small scales by conventional altimeter missions. Through an analysis of simulations, we show that heterogeneous backscattering scenes can result in the corruption of the altimeter waveforms and retracked parameters. The retrackers used in current ground processors cannot well fit the Brown model during backscattering events because this model has been designed for a homogeneous scene. The error is also propagated along-track because of the size and shape of the low resolution mode (LRM) disc-shaped footprint. The hump phenomenon is shown to be almost ubiquitous in the ocean, yet more intense at low latitudes and in the Indian Ocean and Western Pacific Ocean, where backscattering events are more frequent. Its overall signature could be a Gaussian-like random signal smooth for wavelengths smaller than 15 km, i.e. white noise on 1 Hz products. The analysis of current data from 5 altimetry missions highlights the influence of the instrument design and altitude, and the influence of the retracker used. The spectral hump is a systematic response to random events and it is possible to mitigate it with new processing. Simulations and geographically limited datasets from the synthetic aperture radar mode (SARM) of Cryosat-2 show that the thin stripe-shaped synthetic footprint of SARM might be less sensitive to the artifact.

Poisson, Jean-Christophe; Thibaut, Pierre; Dibarboure, Gérald; Labroue, Sylvie; Lasne, Yannick; Boy, François; Picot, Nicolas

2013-04-01

324

Working standard of wavelength unit for pulsed laser  

SciTech Connect

Finding it necessary to include a metrological circuitry for means of measurement of pulsed laser wavelength, a working standard and standard and working means of measurements of the pulsed laser wavelengths were designed and built. The working standard (WS) is designed to transfer the wavelength unit to the standard lasers and the standard means of measurement. The design of the WS is described. The WS of the wavelength unit for pulsed lasers was developed based on multipath Fizeau interferometers with an automatic system for processing of measurement information.

Balakhnin, A.E.; Bukovskii, B.L.; Bobrik, V.I.; Ivashechkina, M.A.; Mikhailova, T.P.; Sultanov, N.B.; Tomashevskii, Yu.F.

1987-06-01

325

Long external cavity Si photonic wavelength tunable laser diode  

NASA Astrophysics Data System (ADS)

We fabricated wavelength-tunable laser diodes with external cavity consist of Si photonic wire waveguide ring resonators. About 51.5 nm wavelength tuning operation, which covers the entire L-band of the optical communication wavelength range, was obtained. The cavity length dependence of the spectral line width was verified to obtain narrower spectral linewidth. The observed spectral linewidth of 3.78 mm long cavity and 8.19 mm long cavity are 131.0 and 64.8 kHz, respectively. The advantage of long external cavity to design the narrow spectral linewidth Si photonic wavelength tunable laser diode was confirmed.

Kita, Tomohiro; Nemoto, Keita; Yamada, Hirohito

2014-01-01

326

Two-wavelength laser interferometry using superheterodyne detection.  

PubMed

In two-wavelength interferometry, synthetic wavelengths are generated in order to reduce the sensitivity or to extend the range of unambiguity for interferometric measurements. Here a novel optoelectronic technique, called superheterodyne detection, is presented, which permits measurement of the phase difference of two optical frequencies that cannot be resolved by direct optoelectronic heterodyne detection. This technique offers the possibility for operation of two-wavelength interferometry in real time with arbitrary synthetic wavelengths from micrometers to meters in length. Preliminary experimental results are reported. An optical arrangement for absolute range-finding applications using tunable-laser sources (e.g., semiconductor lasers) is proposed. PMID:19745891

Dändliker, R; Thalmann, R; Prongué, D

1988-05-01

327

Multi-wavelength superlensing with layered phonon-resonant dielectrics.  

PubMed

We theoretically propose a multilayered polar-dielectric superlens system capable of sub-diffraction limited imaging simultaneously at different wavelengths. Our theory and simulation results show that this multilayered lens can fulfill a superlensing condition at multiple different wavelengths due to phonon resonances of polar dielectrics, and the number of superlensing wavelengths of the lens can be easily tuned by controlling the number of polar dielectrics. Ideally, by suitably choosing polar dielectrics, our lens can cover wavelengths ranging from infrared to THz frequencies. PMID:22714166

Li, Peining; Taubner, Thomas

2012-05-21

328

Towards Aerosol Light-Absorption Measurements with a 7Wavelength Aethalometer: Evaluation with a Photoacoustic Instrument and 3Wavelength Nephelometer  

Microsoft Academic Search

Two extreme cases of aerosol optics from the Reno Aerosol Optics Experiment are used to develop a model-based calibration scheme for the 7-wavelength aethalometer. The cases include those of very white and very dark aerosol samples. The former allows for an assessment of the scattering offset associated with this filter-based method, with the wavelength-dependent scattering measured from a 3-wavelength nephelometer,

W. Patrick Arnott; Khadeejeh Hamasha; Hans Moosmüller; Patrick J. Sheridan; John A. Ogren

2005-01-01

329

Cloud Power Spectra-Dependence on Solar Zenith Angle and Wavelength, Implications for Cloud Optical Property Retrievals  

NASA Technical Reports Server (NTRS)

Scale breaks (spatial scales at which power-law exponent changes occur) observed in Landsat radiances have proven to be useful indicators of radiative interactions, and have aided the development of improved techniques in the remote sensing of clouds. This work extends previous theoretical studies to absorbing wavelengths by using both Landsat Thematic Mapper (TM) observations and Monte Carlo (MC) simulations to infer the systematic dependencies of power spectral shape on cloud characteristics, illumination conditions, and wavelength. We show that MC simulations operating on a simple fractal model of horizontally inhomogeneous clouds produce power spectra that qualitatively resemble observed spectra. We also show that the decrease in the spectra power-law exponent seen at intermediate scales (referred to as "roughening") as the Sun becomes more oblique is more pronounced at absorbing wavelengths. An automated procedure designed to detect the small scale break location is unable to find systematic differences between TM Band 4 and Band 7, despite the fact that MC simulations point to systematic differences in horizontal fluxes. The effect of these qualitative characteristics of the spatial spectra on the retrieval of cloud optical properties is examined by comparing power spectra of nadir radiances with power spectra of optical properties retrieved using either traditional Independent Pixel Approximation approaches or modifications based on normalized radiance indices and the inverse Non-local Independent Pixel Approximation. Assuming that the actual cloud properties follow perfect scaling behavior at all scales, we show the improvement of the proposed retrieval modifications.

Oreopoulos, Lazaros; Marshak, A.; Cahalan, R. F.; Wen, G.

1999-01-01

330

Highly accurate Michelson type wavelength meter that uses a rubidium stabilized 1560 nm diode laser as a wavelength reference  

SciTech Connect

We investigated the accuracy limitation of a wavelength meter installed in a vacuum chamber to enable us to develop a highly accurate meter based on a Michelson interferometer in 1550 nm optical communication bands. We found that an error of parts per million order could not be avoided using famous wavelength compensation equations. Chromatic dispersion of the refractive index in air can almost be disregarded when a 1560 nm wavelength produced by a rubidium (Rb) stabilized distributed feedback (DFB) diode laser is used as a reference wavelength. We describe a novel dual-wavelength self-calibration scheme that maintains high accuracy of the wavelength meter. The method uses the fundamental and second-harmonic wavelengths of an Rb-stabilized DFB diode laser. Consequently, a highly accurate Michelson type wavelength meter with an absolute accuracy of 5x10{sup -8} (10 MHz, 0.08 pm) over a wide wavelength range including optical communication bands was achieved without the need for a vacuum chamber.

Masuda, Shin; Kanoh, Eiji; Irisawa, Akiyoshi; Niki, Shoji

2009-08-01

331

Transdentinal cell photobiomodulation using different wavelengths.  

PubMed

SUMMARY Objective : The aim of this study was to investigate the effects of transdentinal irradiation with different light-emitting diode (LED) parameters on odontoblast-like cells (MDPC-23). Methods and Materials : Human dentin discs (0.2 mm thick) were obtained, and cells were seeded on their pulp surfaces with complete culture medium (Dulbecco modified Eagle medium). Discs were irradiated from the occlusal surfaces with LED at different wavelengths (450, 630, and 840 nm) and energy densities (0, 4, and 25 J/cm(2)). Cell viability (methyltetrazolium assay), alkaline phosphatase activity (ALP), total protein synthesis (TP), and cell morphology (scanning electron microscopy) were evaluated. Gene expression of collagen type I (Col-I) was analyzed by quantitative polymerase chain reaction (PCR). Data were analyzed by the Mann-Whitney test with a 5% significance level. Results : Higher cell viability (21.8%) occurred when the cells were irradiated with 630 nm LED at 25 J/cm(2). Concerning TP, no statistically significant difference was observed between irradiated and control groups. A significant increase in ALP activity was observed for all tested LED parameters, except for 450 nm at 4 J/cm(2). Quantitative PCR showed a higher expression of Col-I by the cells subjected to infrared LED irradiation at 4 J/cm(2). More attached cells were observed on dentin discs subjected to irradiation at 25 J/cm(2) than at 4 J/cm(2). Conclusion : The infrared LED irradiation at an energy density of 4 J/cm(2) and red LED at an energy density of 25 J/cm(2) were the most effective parameters for transdentinal photobiomodulation of cultured odontoblast-like cells. PMID:25136901

Turrioni, Aps; Basso, Fg; Alonso, Jrl; de Oliveira, Cf; Hebling, J; Bagnato, Vs; de Souza Costa, Ca

2015-01-01

332

Long Wavelength Emission from Extrasolar Planets  

NASA Astrophysics Data System (ADS)

At long wavelengths (? > 6 m; ? < 40 MHz), the emission from Jupiter is dominated by extremely strong and variable cyclotron maser emission. This emission arises from solar wind deposited keV electrons in the magnetosphere, which subsequently develop an anisotropy in their energy distribution, becoming unstable. When these electrons encounter the auroral zones of the planet, emission results at the gyrofrequency of the magnetic field at the location of the electron (fg = 2.8 Bgauss MHz). The emission is very sporadic, but can reach magnitudes of 105 Jy. In addition, the emission is modulated by the satellite Io. It would be extremely valuable to detect this type of emission from Extrasolar Giant Planets (EGPs), because it provides the following: Direct detection of the EGP; Presence and strength of the EGP magnetic field; Existence of satellites; Rotation period of the EGP. Current predictions (using the so-called ``Radiometric Bode's Law'') suggest that it is possible to detect this type of emission from EGPs, but that it is necessary to catch the planet in an outburst. Even in outburst, the predicted emission is weak, of order mJy. Searches with the VLA at 74 and 330 MHz have been unsuccessful so far [2]. Added sensitivity and lower frequencies are what are needed for more conclusive searches for this emission. There are currently two instruments being proposed to be built which would provide additional sensitivity at low frequencies: LOFAR and SKA. Prospects seem good that at least LOFAR may come on-line within the next decade or so. [1] Farrell et al., 1999, JGR, 104, 14025; Zarka et al., 2001, Ap&SS, 277, 293. [2] Bastian et al., 2000, ApJ, 545, 1058.

Butler, B. J.

2003-05-01

333

An Update on the Long Wavelength Array  

NASA Astrophysics Data System (ADS)

The Long Wavelength Array (LWA), a SKA Pathfinder, will be a new multi-purpose radio telescope operating in the frequency range 10-88 MHz. Scientific programs include pulsars, supernova remnants, general transient searches, radio recombination lines, solar and Jupiter bursts, investigations into the "dark ages" using redshifted hydrogen, and ionospheric phenomena. Upon completion, LWA will consist of 53 phased array "stations” distributed across a region over 400 km in diameter. Each station consists of 256 pairs of dipole-type antennas whose signals are formed into beams, with outputs transported to a central location for high-resolution aperture synthesis imaging. The resulting image sensitivity is estimated to be a few mJy (5sigma, 8 MHz, 2 polarizations, 1 h, zenith) from 20-80 MHz; with angular resolution of a few arcseconds. A technical overview of the LWA project is available (Ellingson etal. 2009, Proc. IEEE, 97, 1421), and additional information is online at http://lwa.unm.edu. Partners in the LWA project include LANL, JPL, NRAO, NRL, UNM, NMT, and Virginia Tech. The first station of the LWA, called "LWA-1", is located near the center of the EVLA and is expected to achieve initial operational capability in early 2011. As of September 2010, all antennas have been installed as well as a subset of the "production” versions of receivers, digital electronics, data recorders, and monitoring and control system. The "transient buffer - wideband” (TBW) capability is operational with 20 dipoles, and provides the ability to capture simultaneous raw 196 MSPS A/D output over the entire 10-88 MHz tuning range in 61 ms bursts. Other operating modes are in the final stages of implementation. Some early results obtained with LWA-1 will be presented. Funding for the LWA has been provided by the Office of Naval Research.

Taylor, Gregory B.; Tremblay, S. E.; Pihlstrom, Y.; Craig, J.; Rickard, L.; Dowell, J.; Kassim, N.; Clarke, T.; Hicks, B.; Polisensky, E.; Ray, P.; Schmitt, H.; Woods, D.; Hartman, J.; Ellingson, S.; Wolfe, C.; Navarro, R.; Sigman, E.; Soriano, M.; Owen, F.

2011-01-01

334

Photonic nanostructures for wavelength division multiplexing Martina Gerken a  

E-print Network

Photonic nanostructures for wavelength division multiplexing Martina Gerken a , David A. B. Millerb nanostructures promise compact wavelength division multiplexing (WDM) devices. An important criterion nanostructures can be designed to exhibit high dispersion [5]. We focus on one-dimensional nanostructures, since

Miller, David A. B.

335

Wavelength Agile, Integrated Optical Transmitters for Analog Applications  

E-print Network

-Integrated SGDBR Laser Transmitter for Analog Applications L. A. Johansson, Y. A. Akulova, G. A. Fish, Member, IEEE for analog applications. The wavelength can be tuned anywhere from 1522 to 1573 nm. The suboctave spurious--Distortion, distributed Bragg reflector lasers, wavelength-division multiplexing. I. INTRODUCTION HIGHLY LINEAR analog

Coldren, Larry A.

336

On multicasting in wavelength-routing mesh networks  

Microsoft Academic Search

This paper considers multicasting on wavelength-routing mesh optical networks. Although multicasting has been studied extensively in dieren t network environments, multicasting in this environment is dieren t, and more involved. The paper discusses the challenges of multicast support in optical wavelength routing networks, and reports on the advances made so far in this venue. The paper introduces a classication and

Ashraf Hamad; Tao Wu; Ahmed E. Kamal; Arun K. Somani

2006-01-01

337

ATMOSPHERIC PHASE NOISE AND APERTURE SYNTHESIS IMAGING AT MILLIMETER WAVELENGTHS  

E-print Network

wavelength aperture synthesis images is limited by atmospheric turbulence. Observing techniques and dataATMOSPHERIC PHASE NOISE AND APERTURE SYNTHESIS IMAGING AT MILLIMETER WAVELENGTHS M. C. H. Wright on short baselines and in turbulent weather. The rms phase at a 1 km baseline is 1 mm, with a variation

Militzer, Burkhard

338

23 Wavelength with 100 GHz spacing comb generator source  

E-print Network

, polarization maintaining fibre, semicon- ductor optical amplifier 1. Introduction In the recent past there has of 23 wavelengths, spaced at 100 GHz, is demonstrated from a single source using a semiconductor optical also been investigated, in which multi- wavelength oscillation was obtained in a semiconductor optical

Vlachos, Kyriakos G.

339

Very-short-wavelength collective modes in fluids  

Microsoft Academic Search

The existence of very-short-wavelength collective modes in fluids is discussed. These collective modes are the extensions of the five hydrodynamic (heat, sound, viscous) modes to wavelengths of the order of the mean free path in a gas or to a fraction of the molecular size in a liquid. They are computed here explicitly on the basis of a model kinetic

I. M. de Schepper; E. G. D. Cohen

1982-01-01

340

Multiple wavelength operation of an erbium-doped fiber laser  

Microsoft Academic Search

Wavelength-locked, six-channel, colasing operation using a single gain medium is reported for the first time. The system is an all-fiber, erbium-amplifier-based design that uses a grating wavelength division multiplexer with a fixed channel spacing of 4.8 nm for frequency selection. The authors investigate two possible configurations for the laser cavity

J. W. Dawson; K. J. Vahala

1992-01-01

341

High accuracy wavelength calibration for a scanning visible spectrometer  

Microsoft Academic Search

Spectroscopic applications for plasma velocity measurements often require wavelength accuracies <=0.2 A˚. An automated calibration, which is stable over time and environmental conditions without the need to recalibrate after each grating movement, was developed for a scanning spectrometer to achieve high wavelength accuracy over the visible spectrum. This method fits all relevant spectrometer parameters using multiple calibration spectra. With a

Filippo Scotti; Ronald E. Bell

2010-01-01

342

Wavelength division multiplexed fiber optic absolute position encoder  

Microsoft Academic Search

A wavelength division multiplexing (WDM) method for fiber optic sensors is proposed which uses a broadband light source and narrow bandpass thin film optical filter coatings on cylindrical graded index lenses. In the WDM system described here, all bits are multiplexed onto a single signal return fiber by assigning each bit a unique wavelength. A multielement photodetector array is used

Eric D. Park; Erann Gat

1989-01-01

343

Radio-echo studies of meteors at 68-centimeter wavelength  

Microsoft Academic Search

Radio-echo observations of sporadic meteors at 68 cm are described. Sufficient information was gathered to permit the computation of the velocity, height, duration, and intensity for most of the meteors. The principal conclusions reached are that (a) the meteors recorded at this short wavelength are seen ov. era height range not sensibly different from that at long wavelengths; (b) the

J. V. Evans

1965-01-01

344

Long-wavelength HgCdTe negative luminescent devices  

NASA Astrophysics Data System (ADS)

We have investigated the negative luminescent properties of a HgCdTe device, fabricated from a 1 mm diameter array of photodiodes having peak emission at a wavelength of 8.5 ?m. This long-wavelength luminescence is of sufficient efficiency and area to be useful in device applications.

Ashley, T.; Gordon, N. T.; Nash, G. R.; Jones, C. L.; Maxey, C. D.; Catchpole, R. A.

2001-08-01

345

The near millimetre wavelength optical constants of calcium lanthanum sulphide  

NASA Astrophysics Data System (ADS)

Spectroscopic measurements at near millimeter wavelengths made on calcium lanthanum sulphide, a potential material for infrared window applications in high speed aircraft, have revealed a region of transparency below 40/cm. The optical constants of the material have been measured from 5 to 40/cm at 293 K, in order to consider its suitability for near millimeters wavelength applications.

Birch, J. R.; Savage, J. A.; Wilson, A. E. J.; Brierley, C. J.

1992-09-01

346

Selection of Wavelengths for Optimum Precision in Simultaneous Spectrophotometric Determinations.  

ERIC Educational Resources Information Center

Although many textbooks include a description of simultaneous determinations employing absorption spectrophotometry and treat the mathematics necessary for analytical quantitations, treatment of analytical wavelength selection has been mostly qualitative. Therefore, a general method for selecting wavelengths for optimum precision in simultaneous…

DiTusa, Michael R.; Schilt, Alfred A.

1985-01-01

347

Incoherent-to-coherent wavelength conversion using semiconductor optical amplifier  

Microsoft Academic Search

This paper reports for the first time an all-optical wavelength conversion of an incoherent optical signal to a coherent optical signal using the cross-gain modulation in semiconductor optical amplifiers. Wavelength division multiplexed networks using broadband sources have performance limited by beat noise; conversion from a noncoherent to a coherent signal eliminates beat noise and enables the elimination of the bit

Mourad Menif; Pascal Lemieux; Walid Mathlouthi; Leslie Ann Rusch

2004-01-01

348

Short wavelength electromagnetic propagation in magnetized quantum plasmas  

Microsoft Academic Search

The quantum electrodynamical (QED) short wavelength correction on plasma wave propagation for a nonrelativistic quantum plasma is investigated. A general dispersion relation for a thermal multicomponent quantum plasma is derived. It is found that the classical dispersion relation for any wave mode can be modified to include quantum and short wavelength QED effects by simple substitutions of the thermal velocity

J. Lundin; J. Zamanian; M. Marklund; G. Brodin

2007-01-01

349

Planarian Phototactic Assay Reveals Differential Behavioral Responses Based on Wavelength  

PubMed Central

Planarians are free-living aquatic flatworms that possess a well-documented photophobic response to light. With a true central nervous system and simple cerebral eyes (ocelli), planarians are an emerging model for regenerative eye research. However, comparatively little is known about the physiology of their photoreception or how their behavior is affected by various wavelengths. Most phototactic studies have examined planarian behavior using white light. Here, we describe a novel planarian behavioral assay to test responses to small ranges of visible wavelengths (red, blue, green), as well as ultraviolet (UV) and infrared (IR) which have not previously been examined. Our data show that planarians display behavioral responses across a range of wavelengths. These responses occur in a hierarchy, with the shortest wavelengths (UV) causing the most intense photophobic responses while longer wavelengths produce no effect (red) or an apparent attraction (IR). In addition, our data reveals that planarian photophobia is comprised of both a general photophobic response (that drives planarians to escape the light source regardless of wavelength) and wavelength-specific responses that encompass specific behavioral reactions to individual wavelengths. Our results serve to improve the understanding of planarian phototaxis and suggest that behavioral studies performed with white light mask a complex behavioral interaction with the environment. PMID:25493551

Paskin, Taylor R.; Jellies, John; Bacher, Jessica; Beane, Wendy S.

2014-01-01

350

Analysis of a dual-wavelength surface reference radar technique  

NASA Technical Reports Server (NTRS)

The use of the single-wavelength surface reference technique (SRT), the standard dual-wavelength technique (DWT), and dual-wavelength surface reference technique (DSRT) for measuring precipitation from space is analyzed, and the results are compared. The characteristics of the three methods are described, and the surface return powers during clear air conditions are measured. It is observed that the rain rate estimates obtained with the DWT and DSRT are identical in form, and the surface reflectance can be derived from the estimates by replacing the rain reflectivity statistics with those of the backscattering cross section of the surface. The data reveal that the DSRT is more applicable than the SRT when the wavelength correlation in the backscattering cross section of the surface is high or when the mean values of the backscattering cross section at the two wavelengths are nearly equal.

Meneghini, Robert; Jones, Jeffrey A.; Gesell, Leslie H.

1987-01-01

351

Lethal effects of short-wavelength visible light on insects  

PubMed Central

We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light. PMID:25488603

Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

2014-01-01

352

Polarization-independent optical wavelength filter for channel dropping applications  

DOEpatents

The polarization dependence of optical wavelength filters is eliminated by using waveguide directional couplers. Material birefringence is used to compensate for the waveguide (electromagnetic) birefringence which is the original cause of the polarization dependence. Material birefringence is introduced in a controllable fashion by replacing bulk waveguide layers by finely layered composites, such as multiple quantum wells using III-V semiconductor materials. The filter has use in wavelength-division-multiplexed fiber optic communication systems. This filter has broad application for wavelength-tunable receivers in fiber optic communication links, which may be used for telecommunications, optical computer interconnect links, or fiber optic sensor systems. Since multiple-wavelength systems are increasingly being used for all of these applications, the filter is useable whenever a rapidly tunable, wavelength-filtering receiver is required.

Deri, Robert J. (Pleasanton, CA); Patterson, Frank (Livermore, CA)

1996-01-01

353

Polarization-independent optical wavelength filter for channel dropping applications  

DOEpatents

The polarization dependence of optical wavelength filters is eliminated by using waveguide directional couplers. Material birefringence is used to compensate for the waveguide (electromagnetic) birefringence which is the original cause of the polarization dependence. Material birefringence is introduced in a controllable fashion by replacing bulk waveguide layers by finely layered composites, such as multiple quantum wells using III-V semiconductor materials. The filter has use in wavelength-division multiplexed fiber optic communication systems. This filter has broad application for wavelength-tunable receivers in fiber optic communication links, which may be used for telecommunications, optical computer interconnect links, or fiber optic sensor systems. Since multiple-wavelength systems are increasingly being used for all of these applications, the filter is useable whenever a rapidly tunable, wavelength-filtering receiver is required. 14 figs.

Deri, R.J.; Patterson, F.

1996-05-07

354

Lethal effects of short-wavelength visible light on insects.  

PubMed

We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light. PMID:25488603

Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

2014-01-01

355

Lethal effects of short-wavelength visible light on insects  

NASA Astrophysics Data System (ADS)

We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light.

Hori, Masatoshi; Shibuya, Kazuki; Sato, Mitsunari; Saito, Yoshino

2014-12-01

356

Short-wavelength Yb:fiber laser analysis  

NASA Astrophysics Data System (ADS)

Yb:fiber lasers have shown excellent performance in the 980–1100 nm wavelength range. To extend the range below 980 nm, it becomes difficult to reach the transparent condition due to the smaller ratio between emission and absorption cross sections. As a result, a high demand of population inversion is needed, and the selection of pump wavelength as well as other intra-cavity parameters are crucial for lasing in the 920–960 nm wavelength range. To find a feasible solution, the pump wavelength, fiber length, and laser cavity transmittance were systematically studied. Based on the experimental result of a 960 nm Yb:fiber laser, the re-absorption loss and temperature dependent gain can be reliably modeled. The result shows promise in the development of a Yb:fiber laser at a wavelength as short as 920 nm.

Yi, J. Y.; Chang, S. F.; Hsu, C. N.

2013-12-01

357

The Balmer Wavelength Range of BP Tauri  

NASA Astrophysics Data System (ADS)

We have analyzed all the observations of BP Tauri taken by the International Ultraviolet Explorer (IUE) in the low-resolution (??~6 Å), long-wavelength (?=1850-3350 Å) range. This data set contains 61 spectra. We observe variability in the ultraviolet continuum of ?mcont.~1 mag and variability in the Mg II line flux of ?mMgII~0.8 mag. Moreover, these spectra do not show any correlation between the continuum flux and the Mg II line flux, thus resolving a standing controversy in the literature concerning the origin of the Mg II line flux. There is no correlation between the color temperature of the UV continuum and the average value of its flux. Using models of the accretion process recently developed by other authors, we obtain energy fluxes, accretion spot sizes, and accretion rates from the IUE observations of BP Tauri. We find average energy fluxes of 5.0×1011 ergs cm-2 s- 1, average spot sizes of 4.4×10-3 times the stellar surface, and average accretion rates of 1.6×10-8 Msolar yr-1. Our analysis shows that the particle energy flux and the UV flux in the stellar surface are proportional to each other. Most strikingly, we observe a correlation between accretion rate and spot size, with the spot size increasing as the square of the accretion rate. Based on the results of a simulation, we conclude that geometrical effects (i.e., the varying inclination of the spot with respect to the observer) are not enough to account for this effect. Current models of the accretion process fail to reproduce such an effect, suggesting the need of using more realistic descriptions of the stellar field when treating magnetospheric accretion. There may also be an unmodeled efficiency factor that determines how matter is loaded into the field lines. Nondipole fields, geometry, oblique shocks, and the possibility of ``limb brightening'' should be taken into account when creating models and explaining the results of observations of T Tauri stars.

Ardila, David R.; Basri, Gibor

2000-08-01

358

A Study of Wavelength Calibration of NEWSIPS High-Dispersion Spectra  

E-print Network

In this study we cross-correlate many IUE echellograms of a variety of stars to evaluate systematic error sources in the wavelength zeropoint of all three cameras. We first evaluated differences between the final archived ("NEWSIPS") and the originally processed ("IUESIPS") spectra. These show a clear time dependence in zeropoint for the SWP camera due to revisions in the IUESIPS wavelength scale. Small IUESIPS - NEWSIPS differences are also found for the LWR camera. We also examined wavelength zeropoint disparities between data obtained both through the small and large entrance apertures and for observations made by different target acquisition modes for faint and bright stars. We found that velocities resulting from these alternative observing modes are nil. For large-aperture observations the dominant error source is the target position placement in the aperture. We searched for spurious trends with time, and found only a suggestion of time trends for faint stars observed with the SWP camera. We also discovered 1-day, +/-3 km/s sinusoidsal patterns in intensive monitoring data which are ascribable to changes in telescope focus resulting from thermal drifts. In the second part of the paper, we measured mean zeropoint errors of NEWSIPS echellogram data against laboratory results by using the GHRS spectral atlas of the 10 Lac. We find that the derived apparent velocity difference for this star is -1 +/-3.5 km/s. Several less precise comparisons lead to similar results. The zeropoints of the NEWSIPS-processed LWP/LWR cameras are evaluated and are also found to be nearly zero (+/-5 km/s) relative to HST atlases of Arcturus and Procyon atlas. These results do not support result by Gonzalez-Riestra et al. that corrections should be introduced to the wavelength scales of various NEWSIPS high-dispersion data products.

Myron A. Smith

2001-04-03

359

Nanometer scale imaging with table top extreme ultraviolet sources  

Microsoft Academic Search

Decreasing the illumination wavelength allows to improve the spatial resolution in photon-based imaging systems and enables a nanometer-scale spatial resolution. Due to a significant interest in nanometer-scale spatial resolution imaging short wavelengths from extreme ultraviolet (EUV) region are often used. A few examples of various imaging techniques, such as holography, zone plate EUV microscopy, computer generated hologram EUV reconstruction, lens-less

Przemyslaw W. Wachulak; Richard L. Sandberg; Artak Isoyan; Lukasz Urbanski; Andrzej Bartnik; Randy A. Bartels; Carmen S. Menoni; Henryk Fiedorowicz; Jorge J. Rocca; Mario C. Marconi

2010-01-01

360

Scale effects on dynamic wave propagation in heterogeneous media  

NASA Astrophysics Data System (ADS)

To study scale-effects on wave propagation in 3-D heterogeneous media, we conducted dynamic and static laboratory experiments on seven samples of glass beads cast with epoxy. We measured P and S wave velocities and frequency dispersion by the pulse-transmission method, and static elastic Young's modulus by a uniaxial stress test. We changed the scale of the heterogeneity by varying the diameter of the glass beads in each sample, and obtained wavelength to scale ratios varying from 0.2 to 20. We observed about 22% P-wave velocity dispsersion and 15% S-wave velocity dispersion within this range of wavelength to scale ratios. We observed no scale effects on the static Young's modulus of the same seven samples. It is clear that strong wave velocity dispersion in the experiment is due to the dynamic wavelength-scale effects caused by scattering.

Yin, Hezhu; Mavko, Gary; Mukerji, Tapan; Nur, Amos

361

Standard Reference Materials: Hydrogen Cyanide H13C14N Absorption Reference for 1530-1560 nm Wavelength Calibration - SRM 2519  

Microsoft Academic Search

Standard Reference Material (SRM) 2519 is an optical-fiber-coupled absorption cell containing hydrogen cyanide (H13C14N) gas. It is intended for use in calibrating the wavelength scale of wavelength measuring instruments in the 1500 nm region. About 50 accurately measured absorption lines of the R and P branch of the 2 ?3 rotational-vibrational band of H 13C14N are located in the 1530-1560

Sarah L. Gilbert; William C. Swann; Chih-Ming Wang

362

Laser line wavelength sensor based in a dual-wavelength fiber laser with a Hi-Bi loop Sagnac interferometer  

NASA Astrophysics Data System (ADS)

We present an experimental method for straight forward dual wavelength Erbium doped fiber linear cavity laser characterization based in laser line spectrum behavior due to the Hi-Bi FOLM transmission spectrum wavelength displacement by temperature variations in the fiber loop. The laser operation is for a single and dual mode, obtained through the adjustment of the cavity losses by the Sagnac interferometer spectrum wavelength displacement due to the temperature variation of the fiber loop. The method allow determine the laser operation from a single emission line and a two emission lines simultaneously through the Sagnac transmittance spectrum optical power variations measurement due to wavelength spectrum shifting for each laser wavelength generated separately and overlapping these obtained spectrums.

Durán Sánchez, M.; Álvarez Tamayo, R. I.; Pottiez, O.; Kuzin, E. A.; Ibarra-Escamilla, B.; González-García, A.; Barcelata Pinzón, A.

2014-06-01

363

A wavelength conversion circuit for active multi-spectral detection  

NASA Astrophysics Data System (ADS)

Active multi-spectral detection technology is used to acquire the information of the targets - such as spectrum, distance, intensity, and location and so on. So the active multi-spectral detection technology becomes one of the main trends of development of detection system in the future. Based on the analyzing the theory of streak tube lidar active multi-spectral detection system, we design a wavelength conversion circuit which can be applied to implement wavelength conversion in the streak tube lidar in the active multi-spectral detection. Through the O-E-O conversion mode, the wavelength of laser echo signal which contains the target information is transformed into another wavelength which represents the spectral peak response wavelength of the stripe tube photocathode. The simulation results show that when the input laser echo signal wavelength is 1.55um, and the after-converted wavelength is 0.85um , the photon conversion efficiency can reach 2.2×106 ,the signal to noise ratio can reach 19.3dB. And when the target distance or the signal bandwidth increases, the signal to noise ratio(SNR) will decrease accordingly.

Kang, Yanyan; Han, Shaokun; Xia, Wenze; Li, Baowei

2014-10-01

364

Wavelength-Agile External-Cavity Diode Laser for DWDM  

NASA Technical Reports Server (NTRS)

A prototype external-cavity diode laser (ECDL) has been developed for communication systems utilizing dense wavelength- division multiplexing (DWDM). This ECDL is an updated version of the ECDL reported in Wavelength-Agile External- Cavity Diode Laser (LEW-17090), NASA Tech Briefs, Vol. 25, No. 11 (November 2001), page 14a. To recapitulate: The wavelength-agile ECDL combines the stability of an external-cavity laser with the wavelength agility of a diode laser. Wavelength is modulated by modulating the injection current of the diode-laser gain element. The external cavity is a Littman-Metcalf resonator, in which the zeroth-order output from a diffraction grating is used as the laser output and the first-order-diffracted light is retro-reflected by a cavity feedback mirror, which establishes one end of the resonator. The other end of the resonator is the output surface of a Fabry-Perot resonator that constitutes the diode-laser gain element. Wavelength is selected by choosing the angle of the diffracted return beam, as determined by position of the feedback mirror. The present wavelength-agile ECDL is distinguished by design details that enable coverage of all 60 channels, separated by 100-GHz frequency intervals, that are specified in DWDM standards.

Pilgrim, Jeffrey S.; Bomse, David S.

2006-01-01

365

Diffraction limit investigation with sub-wavelength pixels  

NASA Astrophysics Data System (ADS)

Current state-of-the-art pixel dimensions for both visible and long-wave infrared (LWIR) imagers are approaching the wavelength of measurement. It is expected that technological advances will continue and that sub-wavelength pixels for these wavebands will become a reality. In light of the diffraction limit, scientists and engineers in the visible and infrared domains have now begun pose the question as to whether it is worth having a focal plane array (FPA) with pixel dimensions smaller than the imaging wavelength. Meanwhile, in the terahertz domain, FPAs have already been fabricated and cameras designed around them with sub-wavelength pixels. INO has developed THz cameras with 160x120 pixels with pixel pitch of 52 ?m and with 388 x 284 pixels with pixel pitch of 35 ?m. The THz wavelength range is from 40 ?m to 1000 ?m and thus the focal plane array has pixel dimensions below that of the imaging wavelength. This paper discusses experimental results of diffraction limit investigation using sub-wavelength pixel THz cameras.

Bergeron, A.; Terroux, M.; Marchese, L.; Dufour, D.; Le Noc, L.; Chevalier, C.

2013-06-01

366

[High-precision wavelength calibration of wide-band monochromator].  

PubMed

Usually the monochromator is used to output monochromatic light to calibrate the space remote sensing spectrometer. In the present paper, the confidence of space remote sensing spectrometer is used as a standard to evaluate the precision of wide-band monochromator wavelength calibration. Through analysis of the accuracy of the instrument, the monochromator wavelength repeatability error and deviations was obtained respectively. And the intrinsic spectrum of the high pressure mercury lamp and the grating diffraction was used as calibration lines to avoid the error caused by replacing the light source. Through the special method of wavelength calibration to shorten the scan time, the Gaussian fitting was used to look for peaks of wavelength to reduce error. Finally, the relationship derived from polynomial fitting to measure the exact wavelengths' accuracy of the monochromator and calculate the calibration confidence of the space remote sensing spectrometer. Using this method, we can make wavelength accuracy of the 1.5 M monochromator with wavelength band from 200 to 840 nm to reach to +/- 0.016 nm, then the confidence of the space remote sensing spectrometer can reach to 99.82%. PMID:23285905

Zhang, Zi-Hui; Wang, Shu-Rong; Huang, Yu; Li, Bo; Yu, Xiang-Yang; Lin, Guan-Yu

2012-10-01

367

Wavelength adjustment using an eye model from aberrometry data.  

PubMed

We developed a method to convert aberrometry data obtained in one wavelength to the corresponding data in another wavelength using an eye model. A single map of aberrometry data is used to construct a free-form one-surface eye model. A general algorithm for the surface construction is described and implemented for real aberrometry data. Our method can handle varying conjugate distances of the measurement plane of the aberrometer and can also manage the chief ray prism that may be present. The algorithm is validated with the aid of an artificial plastic eye. The wavefronts in different wavelengths are compared through the Zernike analysis not only for lower-order aberrations, but also for higher-order aberrations. The results show that the changes of the Zernike aberration coefficients due to wavelengths are non-uniform. The defocus term has the highest effect from wavelength changes, which is consistent with the previous literature. Our method is compared with two approximate semi-analytical algorithms. The wavelength adjustments from a multi-surface eye model are contrasted with our method. We prove analytically that the conventional method of wavelength adjustment is based on paraxial analysis. In addition, we provide a method of finding the chief ray using back-projection in some cases and discuss different meanings of prism. PMID:20596142

Nam, Jayoung; Rubinstein, Jacob; Thibos, Larry

2010-07-01

368

(Very) long wavelength deformations of Africa since late Cretaceous times  

NASA Astrophysics Data System (ADS)

The African continent is characterized by a bimodal topography. The 900-1100m elevation peak mainly corresponds to the Southern African (Kalahari Plateau) and the East African Domes, whereas the 300-400 m peak is the mean elevation of the Sahara. Those reliefs are characterized by very long wavelength (x1000 km), similar to the scale of mantle dynamics. The origin of this relief, dynamic topography or more local controls (e.g. old lithospheric inheritance), are highly debated and more geological controls are required. To answer those questions - in the frame of the TopoAfrica project - we performed a geomorphical study of Africa coupled with the tectono-sedimentary study of the sedimentary basins or the magmatism. (1) Most of the African reliefs are younger than the Early-Middle Eocene (55-40 Ma). (2) The only significative old relief of Africa is the Southern African Plateau that experienced a two steps evolution, a first uplift during Late Cretaceous contemporaneous with high erosion under humid climatic conditions, followed by a second uplift during Late Eocene - Early Oligocene. The present-day arid to semi-arid climate could explain its preservation. (3) Most of Africa is uplifted during Miocene times (20-10 Ma), age of most of the present-day reliefs. (4) The African magmatic provinces (Virunga-Kivu, Cameroon Volcanic Line, Hoggar, Aïr…) are associated with local uplifts that started around Late Eocene times (40-35 Ma). The relationships of those reliefs with the migration of the African plate over the African superswell will be discussed.

Guillocheau, Francois; The Topoafrica Working Group

2014-05-01

369

Lightpath routing and wavelength assignment in WDM networks  

NASA Astrophysics Data System (ADS)

This paper consider the design of lightpath Routing and Wavelength Assignment (RWA) problem in Wavelength Division Multiplexing (WDM) networks with or without wavelength conversion. To minimize the required network cost, one has to device as few network devices and take the least network building cost with respect to the required demand requirements. In our model, the required cost including the one to install wavelengths in the network nodes and the building cost to use a specific wavelength in a specified optical link. The problem is formulated as a binary linear programming where the objective function is the minimization of network building cost. Many literatures have pointed out that solving the formulation of this kind is very computationally demanding and heuristic algorithms and/or relaxation techniques are needed for problems with nontrivial size. In this paper, a Lagrangian relaxation based solving procedure is developed for the RWA problem. In particular, We first transfer the RWA problem into a multicommodity integer flow problem using graph transformation technique by adding some artificial network nodes and links with proper cost on them. To achieve minimum network cost, two problem solving phases are developed for networks with and without wavelength converter respectively. In the first phase, we try to optimize the cost of routing without violating the wavelength continuity constraints. If no feasible solutions are obtained in this phase, it means there are no sufficient paths to route lightpaths without wavelength converter. We then take another graph extension with wavelength converter geared to the RWA problem and then applying a shortest path based heuristic algorithm to solve the problem based on the solution obtained from first phase. Two network topologies, GTE network and NSFNET network, are used to evaluate the computational results. Examining the Lagrangian based heuristic results and the lower bounds reveal that the proposed algorithm can efficiently provide a nearly optimal solution for our problem.

Lee, Steven S.; Wu, Cheng-Shong; Chang, Ching-Lung

2001-10-01

370

Optical amplification at the 1.31 wavelength  

DOEpatents

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

Cockroft, Nigel J. (Los Alamos, NM)

1994-01-01

371

Tutorial on multimode fiber optic wavelength division multiplexing  

NASA Technical Reports Server (NTRS)

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

Spencer, J. L.

1982-01-01

372

Nonstoichiometric Laser Materials: Designer Wavelengths in Neodymium Doped Garnets  

NASA Technical Reports Server (NTRS)

The tunable nature of lasers provides for a wide range of applications. Most applications rely on finding available laser wavelengths to meet the needs of the research. This article presents the concept of compositional tuning, whereby the laser wavelength is designed by exploiting nonstoichiometry. For research where precise wavelengths are required, such as remote sensing, this is highly advantageous. A theoretical basis for the concept is presented and experimental results in spectroscopic measurements support the theoretical basis. Laser operation nicely demonstrates the validity of the concept of designer lasers.

Walsh, Brian M.; Barnes, Norman P.

2008-01-01

373

Rational choices for the wavelengths of a two color interferometer  

SciTech Connect

If in a two color interferometer for plasma density measurements, the two wavelengths are chosen to have a ratio that is a rational number, and if the signals from each of the wavelengths are multiplied in frequency by the appropriate integer of the rational number and then heterodyned together, the resultant signal will have all effects of component motion nulled out. A phase measurement of this signal will have only plasma density information in it. With CO{sub 2} lasers, it is possible to find suitable wavelength pairs which are close enough to rational numbers to produce an improvement of about 100 in density resolution, compared to standard two color interferometers.

Jobes, F.C.

1995-07-01

374

Planar Rowland spectrometer for fiber-optic wavelength demultiplexing  

NASA Astrophysics Data System (ADS)

A planar Rowland spectrometer was fabricated and characterized as a wavelength demultiplexer for multimode fiber-optic applications. The spectrometer consisted of a planar multimode glass waveguide with two curved end faces and a cylindrical concave attached to one of the end faces. Semiconductor lasers with wavelengths between 0.825 and 0.845 micron were used for the measurements. Cross-talk isolation between two adjacent fibers with center-to-center separation of 175 microns (100 A in wavelength difference) was measured to be 18 dB. The device's performance was limited by grating diffraction efficiency, optical aberration, waveguide dispersion, and waveguide losses.

Yen, H. W.; Friedrich, H. R.; Morrison, R. J.; Tangonan, G. L.

1981-12-01

375

Observation of a Long-Wavelength Hosing Modulation of a High-Intensity Laser Pulse in Underdense Plasma  

NASA Astrophysics Data System (ADS)

We report the first experimental observation of a long-wavelength hosing modulation of a high-intensity laser pulse. Side-view images of the scattered optical radiation at the fundamental wavelength of the laser reveal a transverse oscillation of the laser pulse during its propagation through underdense plasma. The wavelength of the oscillation ?hosing depends on the background plasma density ne and scales as ?hosing˜ne-3/2. Comparisons with an analytical model and two-dimensional particle-in-cell simulations reveal that this laser hosing can be induced by a spatiotemporal asymmetry of the intensity distribution in the laser focus which can be caused by a misalignment of the parabolic focusing mirror or of the diffraction gratings in the pulse compressor.

Kaluza, M. C.; Mangles, S. P. D.; Thomas, A. G. R.; Najmudin, Z.; Dangor, A. E.; Murphy, C. D.; Collier, J. L.; Divall, E. J.; Foster, P. S.; Hooker, C. J.; Langley, A. J.; Smith, J.; Krushelnick, K.

2010-08-01

376

Stress induced long wavelength photoconductivity in doped silicon infrared detectors  

NASA Technical Reports Server (NTRS)

The long wavelength cutoff of a Si:P detector was extended to 34 microns by the application of a uniaxial stress. An unstressed Si:P photoconductive detector responds to photons of up to 28 microns wavelength. By applying a uniaxial stress to a detector along the /100/ crystal axis, the response was extended to approximately 34 microns. The /100/ axis was chosen as the stress direction because theoretical calculations predicted that such a stress extends the wavelength response more than one along the /110/ axis. These theoretical calculations were based upon fits to experimental data obtained at stresses of up to approximately kbar, and indicated that the extension in wavelength response continues to increase at much larger stresses.

Houck, J. R.

1982-01-01

377

The Long Wavelength Array (LWA) and Interplanetary Scintillation (IPS)  

E-print Network

The Long Wavelength Array (LWA) and Interplanetary Scintillation (IPS) Patrick C. Crane 12 January scintillation (IPS) is the random fluctuation in the intensity and phase of electromagnetic waves passing

Ellingson, Steven W.

378

Dual wavelength laser thermal processing of semiconductors. Final report  

SciTech Connect

The annealing of ion-implantation damage in semiconductors by laser irradiation is optimized by employing a dual wavelength laser source and tailoring the time delay between pulses at the two wavelengths. This takes advantage of the strong temperature dependence of the absorption coefficient for the initially less-strongly absorbed wavelength. A solid-state laser emitting high-intensity pulses at 0.53 millimicrons and 2.06 millimicrons was used in conjunction with an optical fiber delay line to experimentally study the annealing characteristics of an arsenic-implanted silicon solar cell wafer. By varying the length of fiber and varying the delay between pulses of the two wavelengths, it was determined that at 25 nanoseconds delay, the sample surface is preheated by the 0.53 millimicron radiation. These results are in agreement with a theoretical model based on melting and liquid phase epitaxial regrowth. Calculations based on this model are presented.

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

1980-06-01

379

Massively Sub-wavelength Guiding of Electromagnetic Waves.  

PubMed

Recently a new form of ultra-thin flexible waveguide consisting of a conducting comb-like structure with a thickness of the order of 1/600(th) of the operating wavelength was presented. However, whilst the thickness of the guide was massively sub-wavelength, the remaining dimensions (the height and period of the comb) were much longer. In this paper we propose, and experimentally verify, that a modified guiding geometry consisting of a chain of ultra-thin conducting spirals allows guiding of electromagnetic waves with wavelengths that are many times (40+) longer than any characteristic dimension of the guide, enabling super-sub-wavelength guiding and localisation of electromagnetic energy. PMID:25510662

Hooper, I R; Tremain, B; Dockrey, J A; Hibbins, A P

2014-01-01

380

Dynamic Wavelength Conversion in Copropagating Slow-Light Pulses  

NASA Astrophysics Data System (ADS)

Dynamic wavelength conversion (DWC) is obtained by controlling copropagating slow-light signal and control pulse trajectories. Our method is based on the understanding that conventional resonator-based DWC can be generalized, and is linked to cross-phase modulation. Dispersion-engineered Si photonic crystal waveguides produce such slow-light pulses. Free carriers generated by two-photon absorption of the control pulse dynamically shift the signal wavelength. Matching the group velocities of the two pulses enhances the shift, elongating the interaction length. We demonstrate an extremely large wavelength shift in DWC (4.9 nm blueshift) for the signal wavelength. Although DWC is similar to the Doppler effect, we highlight their essential differences.

Kondo, K.; Baba, T.

2014-06-01

381

MEMS based wavelength selective optical switching for integrated photonic circuits  

E-print Network

wavelength dropping behavior. (b) and (c) Ring resonator switch with the lossy material shown in and out) Fig. 2. (a) Optical image of a MEMS ring resonator switch. (b) SEM of the bridge over the ring

Barbastathis, George

382

Nonlinear and wavelength-tunable plasmonic metasurfaces and devices.  

E-print Network

??Wavelength-tunable optical response from solid-state optoelectronic devices is a desired feature for a variety of applications such as spectroscopy, laser emission tuning, and telecommunications. Nonlinear… (more)

Lee, Jongwon

2014-01-01

383

Wavelength-selective, sequential Q-switching laser cavity  

NASA Technical Reports Server (NTRS)

Single-frequency continuous output of laser is converted into series of high-power laser pulses at high repetition rates. Applications include pollutant detection by absorption, laser gain measurements at discrete wavelengths, laser propagation measurement, and laser plasma diagnostics.

Allario, F.; Lucht, R. A.

1974-01-01

384

InAs/AlSb short wavelength quantum cascade lasers.  

E-print Network

??Application of InAs/AlSb materials system for development of short-wavelength quantum cascade lasers is explored. Molecular beam epitaxy (MBE) technology allowing to grow multiperiodical unstrained InAs/AlSb… (more)

Devenson, Jan

2010-01-01

385

Opportunities for Raman wavelength conversion with silicon microdisks  

NASA Astrophysics Data System (ADS)

In this paper, we numerically demonstrate the promise of silicon microdisks for Raman Stokes/anti-Stokes wavelength conversion. We design a silicon microdisk suitable for Raman wavelength conversion with "automatic" quasi-phase matching. We show that with this design and with a 2.5% incoupling efficiency for the pump and Stokes input, we can theoretically achieve wavelength conversion efficiencies up to 3.2 dB at input pump powers as low as 7.8 mW. Regarding fabrication tolerances of the design, we find that small deviations from the optimal cross coupling coefficient and from the condition for "automatic" quasi-phase matching are allowed without deteriorating the wavelength conversion efficiency.

Degli-Eredi, Iterio; Vermeulen, Nathalie; Thienpont, Hugo

2014-05-01

386

Wavelength-Dependent Optical Absorption Properties of Artificial and Atmospheric Aerosol Measured by a Multi-Wavelength Photoacoustic Spectrometer  

NASA Astrophysics Data System (ADS)

Various aspects of the photoacoustic (PA) detection method are discussed from the point of view of developing it into a routine tool for measuring the wavelength-dependent optical absorption coefficient of artificial and atmospheric aerosol. The discussion includes the issues of calibration, cross-sensitivity to gaseous molecules, background PA signal subtraction, and size-dependent particle losses within the PA system. The results in this paper are based on a recently developed four-wavelength PA system, which has operational wavelengths in the near-infrared, in the visible, and in the ultraviolet. The measured spectra of artificial and atmospheric aerosol prove the outstanding applicability of the presented PA system.

Utry, N.; Ajtai, T.; Pintér, M.; Bozóki, Z.; Szabó, G.

2014-12-01

387

Dual photosensitive polymers with wavelength-selective photoresponse.  

PubMed

Polyurethane thin films that photopolymerize and photodegrade upon exposure to light of different wavelengths are presented. The chromic response is based on two caged monomers with the ability to be activated or photocleaved with different wavelengths under single and two-photon excitation. This material represents a dual photoresist with "positive" and "negative" tone contained in a single resist formulation and with the ability to generate complex 2D and 3D patterns. PMID:24831417

García-Fernández, Luis; Herbivo, Cyril; Arranz, Verónica San Miguel; Warther, David; Donato, Loïc; Specht, Alexandre; del Campo, Aránzazu

2014-08-01

388

Wavelength division multiplexed fiber optic absolute position encoder  

NASA Technical Reports Server (NTRS)

A wavelength division multiplexing (WDM) method for fiber optic sensors is proposed which uses a broadband light source and narrow bandpass thin film optical filter coatings on cylindrical graded index lenses. In the WDM system described here, all bits are multiplexed onto a single signal return fiber by assigning each bit a unique wavelength. A multielement photodetector array is used as the encoded position information is in parallel. Preliminary prototype test results are presented.

Park, Eric D.; Gat, Erann

1989-01-01

389

High Accuracy Wavelength Calibration For A Scanning Visible Spectrometer  

Microsoft Academic Search

Spectroscopic applications for plasma velocity measurements often require wavelength accuracies 0.2Â. An automated calibration for a scanning spectrometer has been developed to achieve a high wavelength accuracy overr the visible spectrum, stable over time and environmental conditions, without the need to recalibrate after each grating movement. The method fits all relevant spectrometer paraameters using multiple calibration spectra. With a steping-motor

Ronald Bell Filippo Scotti

2010-01-01

390

Wavelength-dependent spectral extinction of atmospheric aerosols  

NASA Astrophysics Data System (ADS)

A simple functional expression is derived for the wavelength dependence of the extinction coefficient characterizing the extinction of light by atmospheric aerosols. Plots of the reduced optical depth of the aerosol column density vs wavelength are presented for values 2, 3, and 4 of the particle size exponent. The plots are characteristic of those reported in the literature and of those inferred from comparative studies of south horizon and zenith sky radiances in the northern part of urban Toronto.

Nicholls, R. W.

1984-04-01

391

LED-based multi-wavelength phase imaging interference microscopy  

Microsoft Academic Search

LED-based multi-wavelength phase imaging interference microscopy combines phase-shifting interferometry with multi-wavelength optical phase unwrapping. This technique consists of a Michelson-type interferometer illuminated with a LED. The reference mirror is dithered for obtaining interference images at four phase quadratures, which are then combined to calculate the phase of the object surface. The 2pi ambiguities are removed by repeating the experiment using

N. Warnasooriya; M. K. Kim

2007-01-01

392

Topologies for wavelength-routing all-optical networks  

Microsoft Academic Search

Three regular meshed topologies are compared in light of their possible use for the implementation of large all- optical wavelength-routing communication networks (or inter- connection systems). These systems provide all source-destination pairs with end-to-end transparent channels that are identified through a wavelength and a physical path. The considered topolo- gies are the A--dimensional bidirectional square lattice, the twin shuffle, and

Marco Ajmone Marsan; Andrea Bianco; Emilio Leonardi; Fabio Neri

1993-01-01

393

An Automated Dual-Wavelength Spectrophotometer Optimized for Phytochrome Assay  

Microsoft Academic Search

A microcomputer-controlled dual-wavelength spectrophotometer suitable for automated phytochrome assay is described. The optomechanical unit provides for sequential irradiation of the sample by the two measuring wavelengths with intervening dark intervals and for actinic irradiation to inter-convert phytochrome between its two forms. Photomultiplier current is amplified, converted to a digital value and transferred into the computer using a custom-designed IEEE-488 bus

Lee H. Pratt; John E. Wampler; Edwin S. Rich Jr

1984-01-01

394

All-optical wavelength conversion of a polarization multiplexed signal  

Microsoft Academic Search

The implementation of the all-optical wavelength-conversion (AOWC) function will be a key-feature in next-generation networks, as it could enable dynamic signal routing, wavelength reuse and path protection and restoration. At the same time, the use of differential-quadrature phase-shift-keying (DQPSK) modulation technique in combination with polarization multiplexing (POLMUX) is considered as the most promising candidate for the realization of high-bit-rate transmission

P. Martelli; P. Boffi; M. Ferrario; L. Marazzi; P. Parolari; R. Siano; V. Pusino; P. Minzioni; I. Cristiani; C. Langrock; M. M. Fejer; M. Martinelli; V. Degiorgio

2009-01-01

395

Multiple wavelength generation from a mode locked silicon evanescent laser  

Microsoft Academic Search

In this paper, an improved performance of mode locked lasers using silicon evanescent laser approach is shown. Its potential application as multiple wavelength WDM (wavelength division multiplexing) sources is presented. Results from a hybrid silicon evanescent mode locked laser (ML-SEL) that creates a comb of over 100 optical modes within 10-dB of the peak mode output power are also presented.

B. R. Koch; A. W. Fang; O. Cohen; M. Paniccia; D. J. Blumenthal; J. E. Bowers

2008-01-01

396

A single crystal multiple-wavelength electro-optic modulator  

Microsoft Academic Search

A new multi-wavelength low voltage electro-optic modulator has been constructed using the r41coefficient in a single crystal of ADP. It is intended for use in multi-color laser display and recording systems employing a single source such as a krypton-ion laser. The modulator accepts a coaxial mixed wavelength beam and separates the colors using a set of direct view spectroscopic prisms.

J. Schlafer; V. J. Fowler

1971-01-01

397

Wavelength modulation photoacoustic spectroscopy: Theoretical description and experimental results  

Microsoft Academic Search

A theoretical description of photoacoustic spectroscopy generated by wavelength modulation of a semiconductor laser source is reported for a Lorentzian absorption line. This model describes the first- and second-harmonic photoacoustic signals produced by a current-modulated semiconductor laser. Combined intensity- and wavelength-modulation is considered with arbitrary phase shift. Experimental results obtained when probing a CO2 absorption line with a 2-?m distributed

Stéphane Schilt; Luc Thévenaz

2006-01-01

398

Wavelength dependence of colorimetric properties of lighting sources based on multi-color LEDs.  

PubMed

Taking color quality scale (CQS) as color rendering assessment criterion, the parameters including each color LED's peak wavelength ?i and fractional radiant flux Ii are optimized using genetic algorithm to maximize the luminous efficacy of radiation (LER) of the spectral power distributions (SPDs) of multi-color white light source with 3 to 7 components while maintaining the deviation of its color and color-rendering capability from that of the reference light source within the specified scope. Then the wavelength dependence of these SPDs is analyzed. It is shown that to achieve a Q(a) greater than 95 (5-color LEDs) or even close to 100 (7-color LEDs), the spectral energy could be concentrated in the range of 410~675 nm, indicating that this wavelength range makes a major contribution to high color rendering properties. Spectra filtering experiments show that spectrum around 580nm is harmful to color rendering. To obtain a white light source composed of 3-color LEDs with CQS Q(a) ? 80 and correlated color temperature (CCT) within 2700-6500K, the energy ratios among 410-495nm, 495-595nm, and 595-675nm intervals, can be simplified as that of the reference source with the same CCT. PMID:23481833

Li, Hongtao; Mao, Xianglong; Han, Yanjun; Luo, Yi

2013-02-11

399

Identification of wavelengths of strain heterogeneities during creep deformation in Carrara Marble  

NASA Astrophysics Data System (ADS)

We use a new technique combining microfabrication technology and compression tests to map the strain field at a micrometric scale in polycrystalline materials. The motivation of such high-resolution mapping is to identify characteristic wavelengths of heterogeneities for different plasticity mechanisms under varying creep conditions. The micro-strain mapping technique was applied to Carrara Marble under different deformation regimes, at a confining pressure of 300 MPa and temperatures ranging from 200 to 700 °C. In samples deformed to 10% strain in compression at 400°C, 500°C and 600°C, at a 3x10-5 s-1 strain rate, strain can be up to 5 times greater along twins and grain boundaries compared to the macroscopic strain accommodated over the entire sample. Strain averaged across a particular grain may vary by as much as 100%. Moreover, there is a gradual but clear change in the accommodation of strain, from twins to grain boundaries as temperature increases. For a fixed temperature of 600°C, varying strain from 10% to 30% does not appear to increase the wavelength of heterogeneities (i.e. the strain field does not homogenize). Macroscopically, strain hardening is minimal and there seems to be a constant generation of perturbations of similar wavelength.

Quintanilla-Terminel, Alejandra; Evans, Brian

2014-05-01

400

Large-aperture Wide-bandwidth Antireflection-coated Silicon Lenses for Millimeter Wavelengths  

NASA Technical Reports Server (NTRS)

The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n 3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating.We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30deg with low cross polarization.We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth.

Datta, R.; Munson, C. D.; Niemack, M. D.; McMahon, J. J.; Britton, J.; Wollack, Edward J.; Beall, J.; Devlin, M. J.; Fowler, J.; Gallardo, P.; Hubmayr, J.; Irwin, K.; Newburgh, L.; Nibarger, J. P.; Page, L.; Quijada, Manuel A.; Schmitt, B. L.; Staggs, S. T.; Thornton, R.; Zhang, L.

2013-01-01

401

Sensitivity enhancement of grating interferometer based two-dimensional sensor arrays using two-wavelength readout  

SciTech Connect

Diffraction gratings integrated with microelectromechanical systems (MEMS) sensors offer displacement measurements with subnanometer sensitivity. However, the sensitivity of the interferometric readout may drop significantly based on the gap between the grating and the reference surface. A two-wavelength (2-{lambda}) readout method was previously tested using a single MEMS sensor for illustrating increased displacement measurement capability. This work demonstrates sensitivity enhancement on a sensor array with large scale parallelization ({approx}20,000 sensors). The statistical representation, which is developed to model sensitivity enhancement within a grating based sensor array, is supported by experimental results using a thermal sensor array. In the experiments, two lasers at different wavelengths (633 and 650 nm) illuminate the thermal sensor array from the backside, time-sequentially. The diffracted first order light from the array is imaged onto a single CCD camera. The target scene is reconstructed by observing the change in the first diffracted order diffraction intensity for both wavelengths. Merging of the data from two measurements with two lasers was performed by taking the larger of the two CCD measurements with respect to the reference image for each sensor. {approx}30% increase in the average sensitivity was demonstrated for a 160x120 pixel IR sensor array. Proposed architecture is also applicable to a variety of sensing applications, such as parallel biosensing and atomic force microscopy, for improved displacement measurements and enhanced sensitivity.

Ferhanoglu, Onur; Urey, Hakan

2011-07-01

402

Large-aperture wide-bandwidth antireflection-coated silicon lenses for millimeter wavelengths.  

PubMed

The increasing scale of cryogenic detector arrays for submillimeter and millimeter wavelength astrophysics has led to the need for large aperture, high index of refraction, low loss, cryogenic refracting optics. Silicon with n=3.4, low loss, and high thermal conductivity is a nearly optimal material for these purposes but requires an antireflection (AR) coating with broad bandwidth, low loss, low reflectance, and a matched coefficient of thermal expansion. We present an AR coating for curved silicon optics comprised of subwavelength features cut into the lens surface with a custom three-axis silicon dicing saw. These features constitute a metamaterial that behaves as a simple dielectric coating. We have fabricated silicon lenses as large as 33.4 cm in diameter with micromachined layers optimized for use between 125 and 165 GHz. Our design reduces average reflections to a few tenths of a percent for angles of incidence up to 30° with low cross polarization. We describe the design, tolerance, manufacture, and measurements of these coatings and present measurements of the optical properties of silicon at millimeter wavelengths at cryogenic and room temperatures. This coating and lens fabrication approach is applicable from centimeter to submillimeter wavelengths and can be used to fabricate coatings with greater than octave bandwidth. PMID:24513939

Datta, R; Munson, C D; Niemack, M D; McMahon, J J; Britton, J; Wollack, E J; Beall, J; Devlin, M J; Fowler, J; Gallardo, P; Hubmayr, J; Irwin, K; Newburgh, L; Nibarger, J P; Page, L; Quijada, M A; Schmitt, B L; Staggs, S T; Thornton, R; Zhang, L

2013-12-20

403

Design optimization of volume holographic gratings for wavelength filters  

NASA Astrophysics Data System (ADS)

Volume holography is promising for devices such as wavelength filters. However, in previously reported work with these holographic devices the diffraction efficiency and wavelength selectivity were not so satisfactory, which affected the insertion loss and channel spacing of the device respectively. In order to investigate the performances for most of the volume holographic devices which are of finite size and with 90 degree geometry, two-dimensional (2-D) coupled-wave theory is more accurate than that based on the well-known Kogelnik"s coupled-wave theory. In this paper a close-form analytical solution to 2-D coupled wave theory for 2-D restricted gratings is presented firstly. Then in order to achieve the optimum insertion loss and channel spacing for dense wavelength division multiplexing (DWDM) filters, diffraction properties, especially effects of the grating strength and grating size ratio on the peak diffraction efficiency and wavelength selectivity are researched based on the 2-D coupled-wave theory and its solution. The results show that this solution is capable of design optimization of volume holographic gratings for various devices, including wavelength filters. And the design optimization is given in order to gain the optimum peak diffraction efficiency and wavelength selectivity. Finally, some experimental results showing the angular selectivity for different grating size ratio are given, which agree well with the 2-D coupled-wave theory.

Wang, Bo; Chang, Liang; Tao, Shiquan

2005-02-01

404

Why is the Great Red Spot Red? The Exogenic, Photolytic Origin of the UV/Blue-Absorbing Chromophores of Jupiter’s Great Red Spot as Determined by Spectral Analysis of Cassini/VIMS Observations using New Laboratory Optical Coefficients  

NASA Astrophysics Data System (ADS)

For centuries, a major question for Jupiter has been: Why is the Great Red Spot red? In particular, two major theories have been proposed: (1) that the coloring is due to photolytic processes in the upper cloud layer, or (2) it is due to the upwellimg of red materials processed relatively deep within the troposphere. Utilizing indices of refraction for red choromophores generated by the photolysis of ammonia and acetylene in the laboratory, we present results of a spectral analysis of the core of Jupiter’s Great Red Spot (GRS) as observed by the visual channel of the Cassini/Visual Infrared Mapping Spectrometer (VIMS). Consistent with the physical origin of such laboratory-generated chromophores in Jupiter – i.e., by solar-driven UV photolysis within the upper levels of the GRS structure near ~ 0.3 bar – our spectral modeling yields satisfactory results for such Mie scattering chromophores only when they are confined to the upper ~ 100 mbar of the GRS. Beneath this reddish upper cloud layer, our models indicate that the remainder of the GRS cloud – assumed to extend down to at least the ammonia condensation level near 0.6 bar – must be relatively spectrally bright throughout the UV-red spectrum; that is, they must be predominantly a whitish or grey color at depth. Thus, our 0.35-1.0 micron spectral models of the GRS are inconsistent with an endogenic origin of the reddish coloring originating in the depths of Jupiter, but are consistent with a photolytic origin due to the photolysis of ammonia and acetylene in the upper troposphere.

Baines, Kevin H.; Carlson, Robert W.; Momary, Thomas W.

2014-11-01

405

On the wavelength dependence of the effects of turbulence on average refraction angles in occultations by planetary atmospheres  

NASA Technical Reports Server (NTRS)

The dependence of the effects of planetary atmospheric turbulence on radio or optical wavelength in occultation experiments is discussed, and the analysis of Hubbard and Jokipii (1977) is criticized. It is argued that in deriving a necessary condition for the applicability of their method, Hubbard and Jokipii neglect a factor proportional to the square of the ratio of atmospheric or local Fresnel zone radius and the inner scale of turbulence, and fail to establish sufficient conditions, thereby omitting the square of the ratio of atmospheric scale height and the local Fresnel zone radius. The total discrepancy is said to mean that the results correspond to geometrical optics instead of wave optics, as claimed, thus being inapplicable in a dicussion of wavelength dependence. Calculations based on geometrical optics show that the bias in the average bending angle depends on the wavelength in the same way as does the bias in phase path caused by turbulence in a homogeneous atmosphere. Hubbard and Jokipii comment that the criterion of Haugstad and Eshleman is incorrect and show that there is a large wave optical domain where the results are independent of wavelength.

Haugstad, B. S.; Eshleman, V. R.

1979-01-01

406

Integration of both dense wavelength-division multiplexing and coarse wavelength-division multiplexing demultiplexer on one photonic crystal chip  

NASA Astrophysics Data System (ADS)

An integrated model of photonic crystal (PC) demultiplexer that can be used to combine dense wavelength-division multiplexing (DWDM) and coarse wavelength-division multiplexing (CWDM) systems is first proposed. By applying the PC demultiplexer, dense channel spacing 0.8 nm and coarse channel spacing 20 nm are obtained at the same time. The transmission can be improved to nearly 90%, and the crosstalk can be decreased to less than -18 dB by enlarging the width of the bus waveguide. The total size of the device is 21×42 ?m2. Four channels on one side of the demultiplexer can achieve DWDM in the wavelength range between 1575 and 1578 nm, and the other four channels on the other side can achieve CWDM in the wavelength range between 1490 and 1565 nm, respectively. The demonstrated demultiplexer can be applied in the future CWDM and DWDM system, and the architecture costs can be significantly reduced.

Tian, Huiping; Shen, Guansheng; Liu, Weijia; Ji, Yuefeng

2013-07-01

407

Four-Wavelengths-Mixed White Light Emitting Diodes with Dual-Wavelength-Pumped Green and Red Phosphors  

NASA Astrophysics Data System (ADS)

The wavelengths of dual-wavelength light-emitting diodes (LEDs) are near ultraviolet (UV) at approximately 409 and 459 nm for blue when driven at 20 mA. The near-UV emission intensity of LEDs is stronger than the blue emission intensity with a 20 mA driven current. The green and red emission intensities of the phosphor are almost the same as, but less than, the blue emission intensity of the dual-wavelength LED with a 20 mA driven current. The CIE color coordinates are x=0.32 and y=0.35, while the dual-wavelength LED with a green and red phosphor LED lamp is driven at 20 mA.

Lai, Wei-Chih; Sheu, Jinn-Kong; Fu, Yi-Keng; Kuo, Cheng-Huang; Kuo, Chi-Wen; Tun, Ching-Ju; Pan, Ching-Jen; Chi, Gou-Chung

2008-08-01

408

Novel WDM to OTDM wavelength conversion system for transmission of discrete sampling spectrum in single wavelength channel  

NASA Astrophysics Data System (ADS)

In this paper, a novel WDM-to-OTDM conversion system which has a simple setup is proposed. The system is a type of fiber loop consisting of an optical single-side-band (SSB) modulator that is driven by a RF signal source at 10 GHz, a fiber circulator, a single mode fiber coupler, a fiber amplifier and an ultra-narrowband high reflectivity fiber Bragg grating (FBG). The multi-wavelength WDM signals with the spectral sampling interval of 10 GHz (0.08 nm at 1550 nm) is inputted into the system and can be transformed to an OTDM signal carried by one wavelength. The advantages of this multi-wavelength conversion system are that the requirement for the input optical power is low, the wavelength conversion is fast due to the optic-electro effect in a nonlinear optical crystal and the system configuration is compact without need of time delay lines.

Yang, Tianxin; Wang, Changle; Wang, Junlong; Ge, Chunfeng; Sang, Mei

2011-03-01

409

Four-Wavelengths-Mixed White Light Emitting Diodes with Dual-Wavelength-Pumped Green and Red Phosphors  

Microsoft Academic Search

The wavelengths of dual-wavelength light-emitting diodes (LEDs) are near ultraviolet (UV) at approximately 409 and 459 nm for blue when driven at 20 mA. The near-UV emission intensity of LEDs is stronger than the blue emission intensity with a 20 mA driven current. The green and red emission intensities of the phosphor are almost the same as, but less than,

Wei-Chih Lai; Jinn-Kong Sheu; Yi-Keng Fu; Cheng-Huang Kuo; Chi-Wen Kuo; Ching-Ju Tun; Ching-Jen Pan; Gou-Chung Chi

2008-01-01

410

Parsec Scale Faraday Rotation in Quasars  

Microsoft Academic Search

A system for making polarization very long baseline interferometry (VLBI) maps of extragalactic radio sources has been developed over that last decade by the radioastronomy group at Brandeis University. This work represents the first extension of these methods to multiple frequency mapping of the complex polarization of quasars on milliarcsecond scales. By observing at two wavelengths, 3.6 cm and 6

Michael Frank Ochs

1995-01-01

411

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

PubMed Central

We report the use of an all-solid-state ultrashort pulsed source specifically for two-photon microscopy at wavelengths shorter than those of the conventional Ti:Sapphire laser. Our approach involves sum–frequency mixing of the output from an optical parametric oscillator (?= 1400–1640 nm) synchronously pumped by a Yb-doped fibre laser (?= 1064 nm), with the residual pump radiation. This generated an fs-pulsed output tunable in the red spectral region (?= 620–636 nm, ?150 mW, 405 fs, 80 MHz, M2? 1.3). We demonstrate the performance of our ultrashort pulsed system using fluorescently labelled and autofluorescent tissue, and compare with conventional Ti:Sapphire excitation. We observe a more than 3-fold increase in fluorescence signal intensity using our visible laser source in comparison with the Ti:Sapphire laser for two-photon excitation at equal illumination peak powers of 1.16 kW or less. PMID:23078118

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

2012-01-01

412

Multi-Wavelength Radar Studies of Lunar Pyroclastic Deposits  

NASA Astrophysics Data System (ADS)

Lunar pyroclastic deposits were formed early in the Moon's history and are comprised of fine-grained, glassy materials. These low-albedo features are typically associated with mare boundaries, sites of mare volcanism, and fractures in and around impact craters. Optical, ultraviolet and infrared data have been used to map the locations of over one hundred pyroclastic deposits and to study their compositional differences (e.g. Gaddis et al., Icarus, 161, 262, 2003; Weitz et al., JGR, 103, 22725, 1998). We use multi-wavelength radar observations to study the distribution, depth and embedded rock abundance of these deposits. Data were acquired at S-band (12.6 cm wavelength) and P-band (70 cm wavelength) using Arecibo Observatory and the Green Bank Telescope in a bistatic configuration. The P-band images have resolutions of 150 m/pixel; S-band images have resolutions between 20 and 80 m/pixel. Pyroclastic deposits appear dark to the radar at both observed wavelengths because they are smooth, easily penetrable by radar waves, and generally contain few embedded blocks. At S-band wavelengths, changes in radar reflectivity across some of the pyroclastic deposits highlight areas with increased rock abundance. Radar circular polarization ratio maps can be used to identify fine-grained deposits in cases where optical or near-infrared data are ambiguous about the presence of pyroclastics. In some cases, data from multiple radar wavelengths (including archival 3.8 cm wavelength data) can place constraints on the deposit depth. We will present results for pyroclastic deposits surrounding Mare Serenitatis, including Sulpicius Gallus, Rima Menelaus, and Taurus-Littrow, as well as new polarimetry of the Aristarchus Plateau that compliments work done by Campbell et al. (2008, Geology, 36, 135). The S-band data are part of a larger study to map the entire lunar nearside at 80 m/pixel resolution.

Carter, Lynn M.; Campbell, B. A.; Hawke, B. R.; Campbell, D. B.; Nolan, M. C.

2008-09-01

413

Unilateral thalamic Vim and GPi stimulation for the treatment of Holmes' tremor caused by midbrain cavernoma: case report and review of the literature.  

PubMed

A 30-year-old man with brainstem cavernoma experienced hemorrhage and was operated in 2008. Six months after the operation, the patient presented with new complaints of left arm tremor namely Holmes' tremor. Neurological examination also revealed left-sided internuclear ophthalmoplegia, left-sided mild paresis, and increased deep tendon reflexes of the left upper extremity, truncal ataxia, and dysarthria. Brain magnetic resonance imaging showed a postoperative cavity and gliosis at the level of the superior and inferior colliculus in the right tegmentum and right red nucleus with extension to the substantia nigra. Fahn-Tolosa-Marin tremor rating scale (TRS) for his left upper extremity (Part A, score 6) was 11 for the proximal and the distal arm. After the failure of medical treatment, the patient underwent right globus pallidum internus and ventral intermediate thalamic nucleus deep brain stimulation. There were no side effects related to the stimulation. Final TRS months after operation was 3 for the proximal and 4 for the distal arm. PMID:23319330

Aydin, Sabri; Abuzayed, Bashar; Kiziltan, Gunes; Gunduz, Aysegul; Yagci, Selin; Mengi, Murat; Kizilkilic, Osman; Uzan, Mustafa; Hanci, Murat

2013-07-01

414

Wavelength-scale confinement of light and its applications in on-chip photonic devices  

NASA Astrophysics Data System (ADS)

We present design and experimental work toward building room temperature, continuous-wave (CW) lasers with a cavity that confines light to a volume of ? (lambda/n)3. We begin with the mechanisms of strong optical confinement using dispersive metals and photonic crystals. Finite-difference time-domain methods (FDTD) are used to simulate the behavior of electromagnetic fields in the cavity; fast Fourier transform from FDTD-generated near-field data calculates the far-field radiation pattern from the microcavity laser. We then present our investigations into designs where metals are incorporated into microdisk and photonic crystal optical cavities to curb or redirect radiation loss. The significant effects of boundary conditions and substrate feedback on far-field radiation directionality are studied. We evaluate the threshold gain required to achieve room temperature lasing in these metallo-dielectric cavities. While studying the confinement mechanism of photonic crystals on metal substrate, it became clear that room temperature lasing can be achieved in optically-thick photonic crystal cavities, where the thicker semiconductor layer would give us more freedom in designing the vertical p-i-n doping profile within, for a less resistive and leaky electrical path for current injection operation. We fabricate and demonstrate single-mode room temperature lasing by optical pumping in an optically-thick single-defect cavity. We move on to present our design and characterization of coupled-cavity photonic crystal lasers operating with CW, high output power, and directional emission. Single-mode stable emission with output power on the order of 10 muW and linear polarization was achieved. Moreover, we switched from the commonly used InGaAsP quantum well material to the lesser-known InAsP quantum wells in InP cladding, and found that the large band-edge offset between InAsP and InP made a world of difference in achieving high power operation despite the large thermal resistance in the device. For a microcavity laser with directional radiation, Purcell-enhanced spontaneous emission, and diminished effects due to feedback from surrounding structures such as the substrate, nanobeam photonic crystal lasers are analyzed, fabricated, and characterized. Despite thermal resistance an order of magnitude higher than their 2D counterparts, quasi-CW operation with a soft threshold turn-on was achieved. Much work was done to optimize fabrication techniques in order to realize the optical cavity designs with little fabrication error. We detail the high-contrast hydrogen silsesquioxane (HSQ) electron-beam lithography and deep vertical dry etch procedures especially developed for this work. Lastly, related projects on nonlinear silicon photonic devices are presented. Synthetic nonlinear polymer is integrated on to the silicon photonic platform to achieve low half-wave voltage electro-optic modulation. Causes and magnitude of the nonlinear loss particular to silicon waveguides with sub-mum 2 cross-section are evaluated.

Huang, Jingqing

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Optimal wavelength scale diffraction gratings for light trapping in solar cells  

NASA Astrophysics Data System (ADS)

Dielectric gratings are a promising method of achieving light trapping for thin crystalline silicon solar cells. In this paper, we systematically examine the potential performance of thin silicon solar cells with