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1

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

USGS Publications Warehouse

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

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

2010-01-01

2

Wavelength Scaling of High Harmonic Generation Efficiency  

SciTech Connect

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

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

2009-08-14

3

Effective Wavelength Scaling for Optical Antennas  

Microsoft Academic Search

In antenna theory, antenna parameters are directly related to the wavelength lambda of incident radiation, but this scaling fails at optical frequencies where metals behave as strongly coupled plasmas. In this Letter we show that antenna designs can be transferred to the optical frequency regime by replacing lambda by a linearly scaled effective wavelength lambdaeff=n1+n2lambda\\/lambdap, with lambdap being the plasma

Lukas Novotny

2007-01-01

4

Wavelength-scale deformed microdisk lasers  

SciTech Connect

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

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

2011-12-15

5

Zero-Points of FOS Wavelength Scales  

NASA Astrophysics Data System (ADS)

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

Rosa, Michael R.; Kerber, Florian

6

FUV Internal/External Wavelength Scale Monitor  

NASA Astrophysics Data System (ADS)

This program monitors the offsets between the wavelength scale set by the internal wavecal versus that defined by absorption lines in external targets. This is accomplished by observing two external targets in the SMC: SK191 with G130M and G160M and Cl* NGC 330 ROB B37 with G140L {SK191 is too bright to be observed with G140L}. The cenwaves observed in this program are a subset of the ones used during Cycle 17. Observing all cenwaves would require a considerably larger number of orbits. Constraints on scheduling of each target are placed so that each target is observed once every 2-3 months. Observing the two targets every month would also require a considerably larger number of orbits.;

Oliveira, Cristina

2008-07-01

7

The Surface of Titan as Seen by the Cassini VIMS Investigation  

Microsoft Academic Search

The Cassini Visual and Infrared Mapping Spectrometer (VIMS) is an imaging spectrometer working in the wavelength region 0.35-5.2 mum. The science goals of the VIMS investigation range over the entire suite of objects in the Saturn system. As seen by VIMS, the surface of Titan shows several interesting geologic structures, albedo variations and compositional units, among them signs of cryovolcanism

Robert H. Brown; R. Clark; L. Soderblom; J. Barnes; C. Sotin; C. Griffith; B. Buratti; T. McCord; K. Baines; P. Nicholson

2006-01-01

8

Wavelength scaling for reactor-size laser-fusion targets  

Microsoft Academic Search

The symmetric implosion of pellet shells will require sideways thermal transport smoothing of any laser intensity nonuniformities. A scaling law shows a surprisingly strong laser wavelength dependence for this smoothing mechanism; it places a large premium on the use of longer-wavelength near-infrared lasers. This smoothing requirement conflicts with the advantages of shorter laser wavelengths for controlling deleterious plasma instabilities.

John Gardner; Stephen Bodner

1981-01-01

9

Selected Surface-Science Results of the first year of the Cassini VIMS Investigation  

NASA Astrophysics Data System (ADS)

The Cassini Visual and Infrared Mapping Spectrometer (VIMS) is an imaging spectrometer working in the wavelength region 0.35-5.2 microns. The science goals of the VIMS investigation range over the entire suite of objects in the Saturn system. During the year in orbit around Saturn VIMS has made extensive observations of Saturn's rings, its icy satellites, and had 1 distant and 6 close flybys of Titan. Results for Iapetus show the presence of water ice, bound water, CO2 complexed in a similar fashion as on Phoebe, organics and CN compounds Results for Enceladus show a surface that is almost pure water, with no detectable non-water molecular components. Some variations in the size of the individual water-ice grains is seen. The surface of Titan shows several interesting geologic structures and albedo variations, among them signs of cryovolcanism, ridge and groove topography on the scale of a few hundred meters, a bright area in the southern hemisphere that may be ground fog or surface deposits that have been eruptively emplaced, and no evidence for global-scale deposits of liquid methane. This talk will review the recent VIMS results for the surfaces of Titan, Enceladus and Iapetus.

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

2005-08-01

10

Charge and wavelength scaling of RF photoinjector designs  

SciTech Connect

The optimum design of an emittance compensated rf photoinjector is very complicated and time-consuming, relying heavily on multi-particle simulations without good analytical models as a guide. Emittance compensated designs which have been developed, however, can be used to generate other designs with no additional effort if the original design is scaled correctly. This paper examines the scaling of rf photoinjector design with respect to charge and wavelength, and presents emittance and brightness scaling laws for these variables. Parametric simulation studies are presented to illustrate these scaling laws. Deviations from scaling and practical considerations are also discussed. {copyright} 1995 {ital American Institute of Physics}.

Rosenzweig, J. [UCLA Department of Physics, 405 Hilgard Ave., Los Angeles, California 90024 (United States); Colby, E. [UCLA Department of Physics and Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510 (United States)

1995-06-01

11

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

Microsoft Academic Search

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

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

2008-01-01

12

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

13

Cassini/VIMS Spectra and Time-Evolution of Precipitation-Associated Surface Brightenings on Titan  

NASA Astrophysics Data System (ADS)

Large areas of Titan's surface brightened at all wavelengths as seen from Cassini/VIMS for several months, then faded. The brightenings occurred after a large storm and rainfall event, and may relate to volatile refreezing due to evaporative cooling.

Barnes, J. W.; Buratti, B. J.; Turtle, E. P.; Bow, J.; Dalba, P. A.; Perry, J.; Rodriguez, S.; Lemouelic, S.; Baines, K. H.; Sotin, C.; Lorenz, R. D.; Malaska, M. J.; McCord, T. B.; Brown, R. H.; Clark, R. N.; Jaumann, R.; Hayne, P.; Nicholson, P. D.; Soderblom, J. M.; Soderblom, L. A.

2012-03-01

14

Wavelength Scaling of Terahertz Generation by Gas Ionization  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

15

Investigating the Surface of Titan in the 1-2.8 µm Range with CassiniI/VIMS Hyperspectral Images  

NASA Astrophysics Data System (ADS)

We focus in this presentation on the global mapping of the surface of Titan using data from the Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini. The objective is to produce seamless mosaics in the short-wavelength surface windows.

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

2012-03-01

16

Silicon based chip-scale nonlinear optical devices: Laser, amplifier, and wavelength converter  

Microsoft Academic Search

Taking advantage of the high optical nonlinearity and strong light confinement in silicon waveguides, chip-scale nonlinear devices such as Raman lasers, amplifiers, and wavelength converters are realized. Performance and application potential of these devices are presented.

Haisheng Rong; Shengbo Xu; Simon Ayotte; Oded Cohen; Omri Raday; Mario Paniccia

2008-01-01

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.

Montealegre, Maria Camila; Correa, Adriana; Briceno, 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

Vertical Distribution of Gases and Aerosols in Titan's Atmosphere Observed by VIMS/Cassini Solar Occultations  

NASA Astrophysics Data System (ADS)

We present the vertical distribution of gaseous species and aerosols in Titan's atmosphere through the analysis of VIMS solar occultations. We employ the infrared channel of VIMS, which covers the 1 - 5 ?m wavelength range. VIMS occultations can provide good vertical resolution (~10 km) and an extended altitude range (from 70 to 700 km), complementing well the information from other Cassini instruments. VIMS has retrieved 10 solar occultations up to now. They are distributed through the whole Cassini mission and they probe different latitudes in both hemispheres. Two main gases can be observed by VIMS occultations: methane, through its bands at 1.2, 1.4, 1.7, 2.3 and 3.3 ?m, and CO, at 4.7 ?m. We can extract methane's abundance between 70 and 750 km and CO's between 70 and 180 km. Regarding aerosols, the VIMS altitude range allows to get information on the properties of both the main haze and the detached layer. Aerosols also affect the transmittance through their spectral signatures. In particular, a spectral signature at 3.4 ?m that was attributed to aerosols was recently discovered by the analysis of the first VIMS occultation. We will monitor the latitudinal and temporal variations of the 3.4 ?m feature through various occultations. A change in the global circulation regime of Titan sets in with the approaching to the vernal equinox, and a strong decrease of the altitude of the detached layer between the winter solstice and the equinox has indeed been observed. The temporal coverage of VIMS occultations allows the study the effect of these variations in the vertical distribution of aerosol optical and spectral properties.

Maltagliati, Luca; Vinatier, Sandrine; Sicardy, Bruno; Bézard, Bruno; Sotin, Christophe; Nicholson, Philip D.; Hedman, Matt; Brown, Robert H.; Baines, Kevin; Buratti, Bonnie; Clark, Robert

2013-04-01

19

Development of Titan Atmospheric Removal Models for Cassini VIMS Data  

NASA Astrophysics Data System (ADS)

I/F spectra of Titan's surface acquired by Cassini's Visual & Infrared Mapping Spectrometer (VIMS) include signal contributions from both Titan's surface and atmosphere; the strength and wavelength coverage of the atmospheric absorptions leaves on the order of 10 data points with which spectral identification of surface ices and hydrocarbons can be reasonably attempted. Plane parallel radiative transfer (RT) correction methods offer some utility for modeling and subtracting out the atmospheric component in VIMS observations of Titan that are away from the limb and where angle of emergence e?30° and angle of incidence i?120-130°. To accomplish this, we use a DISORT-based radiative transfer correction code, extended from the version used successfully in surface-atmospheric separation retrievals for Mars to include a vertically varying CH4 to N2 ratio, multiple non-Lambertian options for defining the bidirectional reflectance function (BDRF) of the surface layer, and vertically varying haze aerosol properties. In a previous work, we reported our progress on replacing Voyager with Cassini-Huygens model inputs, e.g., pressure-temperature as a function of altitude profile from Huygens ASI and methane mixing ratio combined from Huygens GCMS. In this work, we incorporate new density data from Cassini INMS and haze scattering properties provided by the Huygens DISR team to generate model I/F for Titan's atmosphere up to 1400 km altitude above a non-Lambertian surface. Examples of surface-atmospheric separation of VIMS I/F data extracted from 64 x 64 pixel scenes and planned work to extend this protocol to global VIMS mosaics using 3D spherical shell radiative transfer models will be discussed. Work performed under contract to NASA and under appointment to the NASA Postdoctoral Program (ORAU).

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

2007-10-01

20

Global spectral properties of Rhea measured by VIMS  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

21

VIMS spectra of Titan's surface  

NASA Astrophysics Data System (ADS)

The atmosphere of Titan has been puzzling the scientists for centuries. The presence of methane will perhaps find an answer thanks to the Cassini-Huygens mission. Mapping the surface is compulsory to understand the geological phenomenon ruling the topography of Saturn's satellite. VIMS (Visual and Infrared Mapping Spectrometer [Brown et al. (2003)]) is one of the tools we can use to recover both images of the surface features and hints about its chemical composition. One problem we face is the absorption and diffusion of the solar light by the atmospheric methane and aerosols. The presence of "windows" of low methane absorption allow us to probe down to the surface, with little contribution by the atmosphere. Yet the scattering by the aerosols and the remnant absorption by the methane can be corrected : we use here a radiative transfer model code by Rannou et al. (2005), updated version of the McKay et al. (1989) taking into account the microphysical evolution of the fractal aerosols. It is also further constrained by DISR data [Tomasko et al, 2005]. This model compares fairly well with the atmospheric transmission data VIMS could acquire on the flybys of Titan by Cassini. After correction, we can deduce both the qualitative surface spectrum by inversion of the geometrical albedo, and some hints about the chemical composition of several geomorphological areas we can distinguish on our maps [Rodriguez et al (in press)]. In the future, this code will also allow us to constrain Titan's clouds and atmospheric activity.

Hirtzig, M.; Rodriguez, S.; Rannou, P.; Negrao, A.; Sotin, C.; Coustenis, A.; Le Mouelic, S.; Tobie, G.; Brown, R. H.

2007-08-01

22

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

SciTech Connect

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

Lan Pengfei; Takahashi, Eiji J.; Midorikawa, Katsumi [Extreme Photonics Research Group, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)

2010-06-15

23

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

24

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

PubMed

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

2011-01-31

25

Performance studies of the parallel VIM code.  

National Technical Information Service (NTIS)

In this paper, the authors evaluate the performance of the parallel version of the VIM Monte Carlo code on the IBM SPx at the High Performance Computing Research Facility at ANL. Three test problems with contrasting computational characteristics were used...

B. Shi R. N. Blomquist

1996-01-01

26

VIM-15 and VIM-16, Two New VIM-2-Like Metallo-?-Lactamases in Pseudomonas aeruginosa Isolates from Bulgaria and Germany?  

PubMed Central

Two Pseudomonas aeruginosa urine isolates from Bulgaria and Germany produced two new VIM-2 variants. VIM-15 had one amino acid substitution (Tyr218Phe) which caused a significant increase in hydrolytic efficiency. The substitution Ser54Leu, characterizing VIM-16, showed no influence on enzyme activity. Both genes were part of class I integrons located in the chromosome.

Schneider, Ines; Keuleyan, Emma; Rasshofer, Rudolf; Markovska, Rumyana; Queenan, Anne Marie; Bauernfeind, Adolf

2008-01-01

27

VIM-15 and VIM-16, two new VIM-2-like metallo-beta-lactamases in Pseudomonas aeruginosa isolates from Bulgaria and Germany.  

PubMed

Two Pseudomonas aeruginosa urine isolates from Bulgaria and Germany produced two new VIM-2 variants. VIM-15 had one amino acid substitution (Tyr218Phe) which caused a significant increase in hydrolytic efficiency. The substitution Ser54Leu, characterizing VIM-16, showed no influence on enzyme activity. Both genes were part of class I integrons located in the chromosome. PMID:18519714

Schneider, Ines; Keuleyan, Emma; Rasshofer, Rudolf; Markovska, Rumyana; Queenan, Anne Marie; Bauernfeind, Adolf

2008-06-02

28

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

PubMed

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

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

2009-10-12

29

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra  

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

30

Crossover scaling of wavelength selection in directional solidification of binary alloys.  

PubMed

We simulate cellular and dendritic growth in directional solidification in dilute binary alloys using a phase-field model solved with adaptive-mesh refinement. The spacing of primary branches is examined for a wide range of thermal gradients and alloy compositions and is found to undergo a maximum as a function of pulling velocity, in agreement with experimental observations. We demonstrate that wavelength selection is unambiguously described by a nontrivial crossover scaling function from the emergence of cellular growth to the onset of dendritic fingers. This result is further validated using published experimental data, which obeys the same scaling function. PMID:15697829

Greenwood, Michael; Haataja, Mikko; Provatas, And Nikolas

2004-12-06

31

VIM: A Tool to Explore Your Sources  

NASA Astrophysics Data System (ADS)

VIM (Virtual Observatory Integration and Mining) is a web-based data retrieval and exploration application that assumes an astronomer has a list of `sources' (positions in the sky), and wants to explore archival catalogs, images, and spectra of the sources, in order to identify, select, and mine the list. VIM does this through web forms, building a custom `data matrix', whose rows are the uploaded source positions, and the columns show archival data -- in fact any VO-registered catalog service can be used by VIM, as well as co-registered image cutouts from VO-image services, and spectra from VO-spectrum services. The user could, for example, show together: proper motions from GSC2, name and spectral type from NED, magnitudes and colors from 2MASS, and cutouts and spectra from SDSS. VIM can compute columns across surveys and sort on these (eg. 2MASS J magnitude minus SDSS g). For larger sets of sources, VIM utilizes the asynchronous Nesssi services from NVO, that can run thousands of cone and image services overnight.

Williams, R. D.

2008-08-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

33

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

34

Connections between spectra and structure in Saturn's main rings based on Cassini VIMS data  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

35

Engineering light at the sub-wavelength scale using silicon photonics  

NASA Astrophysics Data System (ADS)

As a result of the evolution semiconductor fabrication tools and methods over several decades, it now possible to routinely design and make optical devices with features comparable to or smaller than the wavelength of the light that propagates through these structures. This paper will review some silicon optical structures with critical features at these extremely short length scales. For example it becomes possible to create segmented waveguide structures with optical properties that can be tuned continuously between those of the cladding and waveguide core, using lithographic patterning rather than varying etch depth. Using thin high index contrast waveguides and the correct polarization, the optical electric field profiles can be shaped to maximize the coupling to molecular monolayers or cladding layers with specific functionality. Examples are given from our recent work on optical biosensors chips which employ grating couplers made by sub-wavelength digital patterning, and use waveguides optimized for coupling to molecular monolayers.

Janz, S.; Cheben, P.; Schmid, J. H.; Bock, P.; Halir, R.; Xu, D.-X.; Densmore, A.; Ma, R.; Molina-Fernandez, I.; Delâge, A.; Vachon, M.; Lapointe, J.; Sinclair, W.; Post, E.; Lamontagne, B.

2011-02-01

36

Comparison between VIMS and radar data on Sinlap crater on Titan  

NASA Astrophysics Data System (ADS)

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

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

37

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

SciTech Connect

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

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

2010-07-15

38

VIM: Initial ENDF/B-VI experience  

SciTech Connect

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

Blomquist, R.N.

1997-08-01

39

Adsorption equilibrium, kinetics and thermodynamics of ?-amylase on poly(DVB-VIM)-Cu(+2) magnetic metal-chelate affinity sorbent.  

PubMed

Designing an immobilised metal ion affinity process on large-scale demands that a thorough understanding be developed regarding the adsorption behaviour of proteins on metal-loaded gels and the characteristic adsorption parameters to be evaluated. In view of this requirement, interaction of ?-amylase as a model protein with newly synthesised magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter, 53-212 ?m) was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerising of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterised by N(2) adsorption/desorption isotherms, electron spin resonance, elemental analysis, scanning electron microscope and swelling studies. Cu(2+) ions were chelated on the m-poly(DVB-VIM) beads and used in adsorption of ?-amylase in a batch system. The maximum ?-amylase adsorption capacity of the m-poly(DVB-VIM)-Cu(2+) beads was determined as 10.84 mg/g at pH 6.0, 25 °C. The adsorption data were analyzed using three isotherm models, which are the Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The pseudo-first-order, pseudo-second-order, modified Ritchie's-second-order and intraparticle diffusion models were used to test dynamic experimental data. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. PMID:22736275

Osman, Bilgen; Kara, Ali; Demirbel, Emel; Kök, Senay; Be?irli, Necati

2012-06-27

40

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

SciTech Connect

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

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

2008-05-02

41

VIMS Molluscan Ecology Oyster Reef Community Research  

NSDL National Science Digital Library

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

2011-10-04

42

Wavelength-scale lens microscopy via thermal reshaping of colloidal particles  

NASA Astrophysics Data System (ADS)

Lenses are by far the most simple tools for visualization. Although they are intrinsically limited in resolution, recent efforts have aimed at focusing visible light in micro-scale lenses with subwavelength resolution, triggering an intense interest in further improving and understanding their performances. Herein, we report on a distinctive library of wavelength-scale solid immersion lenses facilitated the self-assembly of polystyrene colloidal particles. The thermally activated structural changes in polystyrene colloidal spheres directly impact the optical performance of the obtained lenses. Similar melting dynamics is observed for spheres of various size spheres at different temperatures. This allows precise control of the contact angle spanning a broad range from 180° to <20°. The fabricated lenses display deviations from the ray optics, allowing us to resolve features as small as 180 nm using a simple microscopy setup. We succeed in proper self-assembly of the colloidal lenses that enables large-area optical nanoscopy through simple and reliable experimental protocols. The limitations and the artifacts of the present technique are discussed.

Vlad, Alexandru; Huynen, Isabelle; Melinte, Sorin

2012-07-01

43

Wavelength-scale lens microscopy via thermal reshaping of colloidal particles.  

PubMed

Lenses are by far the most simple tools for visualization. Although they are intrinsically limited in resolution, recent efforts have aimed at focusing visible light in micro-scale lenses with subwavelength resolution, triggering an intense interest in further improving and understanding their performances. Herein, we report on a distinctive library of wavelength-scale solid immersion lenses facilitated the self-assembly of polystyrene colloidal particles. The thermally activated structural changes in polystyrene colloidal spheres directly impact the optical performance of the obtained lenses. Similar melting dynamics is observed for spheres of various size spheres at different temperatures. This allows precise control of the contact angle spanning a broad range from 180° to <20°. The fabricated lenses display deviations from the ray optics, allowing us to resolve features as small as 180 nm using a simple microscopy setup. We succeed in proper self-assembly of the colloidal lenses that enables large-area optical nanoscopy through simple and reliable experimental protocols. The limitations and the artifacts of the present technique are discussed. PMID:22728662

Vlad, Alexandru; Huynen, Isabelle; Melinte, Sorin

2012-06-25

44

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

45

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

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

46

Biochemical and Structural Characterization of the Subclass B1 Metallo-?-Lactamase VIM-4 ?  

PubMed Central

The metallo-?-lactamase VIM-4, mainly found in Pseudomonas aeruginosa or Acinetobacter baumannii, was produced in Escherichia coli and characterized by biochemical and X-ray techniques. A detailed kinetic study performed in the presence of Zn2+ at concentrations ranging from 0.4 to 100 ?M showed that VIM-4 exhibits a kinetic profile similar to the profiles of VIM-2 and VIM-1. However, VIM-4 is more active than VIM-1 against benzylpenicillin, cephalothin, nitrocefin, and imipenem and is less active than VIM-2 against ampicillin and meropenem. The crystal structure of the dizinc form of VIM-4 was solved at 1.9 Å. The sole difference between VIM-4 and VIM-1 is found at residue 228, which is Ser in VIM-1 and Arg in VIM-4. This substitution has a major impact on the VIM-4 catalytic efficiency compared to that of VIM-1. In contrast, the differences between VIM-2 and VIM-4 seem to be due to a different position of the flapping loop and two substitutions in loop 2. Study of the thermal stability and the activity of the holo- and apo-VIM-4 enzymes revealed that Zn2+ ions have a pronounced stabilizing effect on the enzyme and are necessary for preserving the structure.

Lassaux, Patricia; Traore, Daouda A. K.; Loisel, Elodie; Favier, Adrien; Docquier, Jean-Denis; Sohier, Jean Sebastien; Laurent, Clementine; Bebrone, Carine; Frere, Jean-Marie; Ferrer, Jean-Luc; Galleni, Moreno

2011-01-01

47

Physical Properties of the Saturnian Ring System Inferred from Cassini VIMS Opposition Observations  

NASA Astrophysics Data System (ADS)

Much can be learned about the nature of Saturn's ring particles and their regoliths by studying the wavelength dependence of their reflectance as a function of phase angle. At small phase angles the reflectance of the rings exhibits the opposition effect (OE) a significant increase in reflectance as phase angle approaches zero degrees. The wavelength dependence of the width and the peak of the OE are indicators of important physical properties of the regoliths of the ring particles such as particle size, particle shape, packing density and albedo. The Cassini VIMS multi spectral imaging spectrometer obtained low phase observations of the Saturnian ring system from 0.4-5.2 microns during 2005. These data clearly show a pronounced (OE). Cassini VIMS opposition surge data indicate a wavelength dependence of the OE that relates to the size and separation of the scattering centers on the surface of the ring particles. Laboratory studies and theoretical models of the OE relate the size and shape of the reflectance increase to physical properties of the medium (Nelson et al, 2002; Spilker et al. 1995; Hapke et al., 1993)). The OE arises from two processes, shadow hiding (SH) and coherent backscattering (CB). The SHOE is observed because shadows cast by the particulate grains on one another are eliminated as phase angle approaches zero degrees. The CBOE is due to constructive interference between light rays traveling in opposite paths through the medium as the path length decreases with decreasing phase angle. The VIMS data at 1.9 microns, where the rings are highly reflective, indicate a strong CBOE effect, however, at 2.1 microns, where the rings are very absorbing, the shape of the phase curve is consistent with SHOE. Hapke et al. 1993,Science, 260, 509-511 Nelson, R. M. et al., 2002. Planetary and Space Science, 50, 849-856 Spilker aka Horn, L.J et al., 1995. IAU Colloquium #150 This work done at JPL under contract with NASA

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

2005-12-01

48

Development of vehicle intelligent monitoring system (VIMS)  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

49

Detection and Characterization of VIM-31, a New Variant of VIM-2 with Tyr224His and His252Arg Mutations, in a Clinical Isolate of Enterobacter cloacae  

PubMed Central

We report the first description of the metallo-?-lactamase VIM-31, a new variant of VIM-2 with Tyr224His and His252Arg mutations, in Enterobacter cloacae 11236, which was isolated from blood specimens of a patient with colonic adenocarcinoma in Belgium. blaVIM-31 was found on a class 1 integron located on a self-transferable but not typeable 42-kb plasmid. Compared to values published elsewhere for VIM-2, the purified VIM-31 enzyme showed weaker catalytic efficiency against all the tested beta-lactam agents (except for ertapenem), resulting from lower kcat (except for ertapenem) and higher Km values for VIM-31.

Bebrone, Carine; Huang, Te-Din; Bouchahrouf, Warda; DeGheldre, Yves; Deplano, Ariane; Hoffmann, Kurt; Glupczynski, Youri

2012-01-01

50

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

51

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

52

High-harmonic spectroscopy of isoelectronic molecules: Wavelength scaling of electronic-structure and multielectron effects  

NASA Astrophysics Data System (ADS)

We study the interplay of electronic-structure and multielectron effects in high-harmonic spectra of the two isoelectronic molecules CO2 and N2O as a function of the near-infrared driving wavelength and intensity. We show that the minima observed in the spectra of aligned molecules (=0.54-0.64) are intensity dependent at the shortest investigated wavelength (1.17 ?m) but become gradually intensity independent at longer wavelengths (1.36 and 1.46 ?m). These results combined with detailed theoretical modeling show that the contributions of several ionization channels are important in the spectra recorded with short-wavelength driving pulses because the minima are located in the cutoff region where the contributions from different channels are comparable. In spectra recorded with longer driving wavelengths, the minima are located in the plateau region of the spectrum and are caused by the electronic structure of the molecules. Our results also rationalize and reconcile previous results and provide general guidelines for future studies.

Rupenyan, A.; Kraus, P. M.; Schneider, J.; Wörner, H. J.

2013-03-01

53

Millimeter scale electrostatic mirror with sub-wavelength holes for terahertz wave scanning  

NASA Astrophysics Data System (ADS)

This work reports the design, microfabrication, and characterization of highly reflective electrostatic mirrors with sub-wavelength holes for scanning terahertz (THz) waves. The mirror consists of an aluminum coated silicon mirror plate precisely assembled on the top of two axis torsional microactuators. The mirror plate with sub-wavelength microholes not only provides high reflectivity over 98% at THz waves by decoupling the surface plasmon resonance but also reduces air damping by allowing air to flow through the mirror plate during the mirror scanning. The device can provide many opportunities for miniaturized THz time domain spectroscopic imaging systems.

Park, Hyeon-Cheol; Lee, Jung-Hwan; Park, Sang-Gil; Yee, Dae-Su; Jeong, Ki-Hun

2013-01-01

54

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

55

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

PubMed

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

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

2012-01-01

56

Compositional Mapping Saturn's Icy satellites with Cassin VIMS (Invited)  

NASA Astrophysics Data System (ADS)

Cassini has completed over 5 years of satellite fly-bys in the Saturn system. The Visual and Infrared Mapping Spectrometer (VIMS) has obtained spatially resolved imaging spectroscopy data on numerous satellites of Saturn. Compositional mapping shows that the satellite surfaces are composed largely of H2O ice, with small amounts of CO2, trace organics, bound water or OH-bearing minerals, and possible signatures of ammonia, H2O or OH-bearing minerals, and as yet unidentified materials. The Cassini Rev 49 Iapetus fly-by on September 10, 2007, provided imaging spectroscopy data on both the dark material and the transition zone between the dark material and the visually bright ice on the trailing side. The dark material has very low albedo with a linear increase in reflectance with wavelength, a 3-micron water absorption, and a CO2 absorption. We have been unable to match this spectrum using tholins and carbon compounds. The dark material is matched by a high component of fine-grained metallic iron plus a small component of nano-phase hematite contributing a UV absorber. Spatially resolved Iapetus data show mixing of dark material with ice and the mixtures display a blue scattering peak with a UV absorber. The blue scattering peak and UV-Visible absorption is observed in spectra of all satellites which contain dark material and in spectra of Saturn's rings. The scattering peak and UV absorption can be explained by Rayleigh scattering from sub-micron particles with a UV absorption, or a combination of Rayleigh scattering and Rayleigh absorption as attributed to spectral properties of the moon. Rayleigh absorption requires high absorption coefficient nano-sized particles, which is also consistent with metallic iron. The UV absorber appears to have increased strength on satellite surfaces close to Saturn, with a corresponding decrease in metallic iron signature. A possible explanation is that the iron is oxidized closer to Saturn by oxygen in the extended atmosphere of Saturn's rings.

Clark, R. N.; Cruikshank, D. P.; Jaumann, R.; Brown, R. H.; Hoefen, T. M.; Stephan, K.; Dalle Ore, C. M.; Curchin, J. M.; Buratti, B. J.; Filacchione, G.; Baines, K. H.; Nicholson, P.

2009-12-01

57

Density Wave Signatures In VIMS Spectral Data  

NASA Astrophysics Data System (ADS)

Spectral scans of Saturn's rings by the Cassini VIMS instrument have revealed both regional and local variations in the depths of the water ice bands at 1.5 and 2.0 microns, which have been interpreted in terms of variations in regolith grain size and the amount of non-icy "contaminants" (Filacchione et al. 2012; Hedman et al. 2012). Noteworthy among the local variations are distinctive patterns associated with the four strong density waves in the A ring. Within each wavetrain there is a peak in band strength relative to the surrounding material, while extending on both sides of the wave is a "halo" of reduced band strength. The typical width of these haloes is 400-500 km, about 2-3 times the visible extent of the density waves. The origin of these features is unknown, but may involve enhanced collisional erosion in the wave zones and transport of the smaller debris into nearby regions. A similar pattern of band depth variations is also seen at several locations in the more opaque B ring in association with the strong 3:2 ILRs of Janus, Pandora and Prometheus. The former shows a pattern just like its siblings in the A ring, while the latter two resonances show haloes, but without central peaks. In each case, the radial widths of the halo approaches 1000 km, but stellar occultation profiles show no detectable density wavetrain. We suggest that this spectral signature may be a useful diagnostic for the presence of strong density waves in regions where the rings are too opaque for occultations to reveal a typical wave profile. More speculatively, the displacement of the haloes' central radii from the calculated ILR locations of 600-700 km could imply a surface density in the central B ring in excess of 500 g/cm^2. This research was supported by the Cassini/Huygens project.

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

2012-10-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

59

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

60

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

61

Visible Infrared Mapping Spectrometer--visible channel (VIMS-V)  

Microsoft Academic Search

The VIMS-V is a passive remote sensing instrument under development for the Italian Space Agency to perform high resolution spectral imaging in the optical waveband. Its unique design relies substantially on conventional materials and fabrication techniques to obtain high sensitivity and versatility in a compact, lightweight, and low power instrument suitable for deep space missions. The prototype will fly on

Francis M. Reininger; Michele Dami; Riccardo Paolinetti; Silvano Pieri; Silvio Falugiani

1994-01-01

62

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

NASA Astrophysics Data System (ADS)

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

Hibbitts, C.; Hansen, G. B.

2009-12-01

63

Cassini-VIMS Observations of Saturn's Rings at SOI  

Microsoft Academic Search

Following the Cassini spacecraft's Saturn Orbit Insertion (SOI) burn on 1 July 2004, the Visual and Infrared Mapping Spectrometer (VIMS) obtained near-infrared spectra from 0.9 to 5.1~mu m in two continuous radial scans across the unlit side of the rings, at ranges of ˜30,000~km. The first scan covers the outer C and inner B rings at a phase angle, alpha

P. D. Nicholson; R. H. Brown; R. N. Clark; D. P. Cruikshank; M. R. Showalter; B. Sicardy

2004-01-01

64

Cassini-VIMS Observations of Saturn's Rings at SOI  

Microsoft Academic Search

Following the Cassini spacecraft's Saturn Orbit Insertion (SOI) burn on 1 July 2004, the Visual and Infrared Mapping Spectrometer (VIMS) obtained near-infrared spectra from 0.9 to 5.1 mu m in two continuous radial scans across the unlit side of the rings, at ranges of ˜30,000 km. The first scan covers the outer C and inner B rings at a phase

P. D. Nicholson; R. N. Clark; D. P. Cruikshank; M. R. Showalter; B. Sicardy; Cassini VIMS

2004-01-01

65

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

66

Purification and Biochemical Characterization of the VIM1 Metallo-b-Lactamase  

Microsoft Academic Search

VIM-1 is a new group 3 metallo-b-lactamase recently detected in carbapenem-resistant nosocomial isolates of Pseudomonas aeruginosa from the Mediterranean area. In this work, VIM-1 was purified from an Escherichia coli strain carrying the cloned blaVIM-1 gene by means of an anion-exchange chromatography step followed by a gel permeation chromatography step. The purified enzyme exhibited a molecular mass of 26 kDa

NICOLA FRANCESCHINI; BERARDO CARAVELLI; JEAN-DENIS DOCQUIER; MORENO GALLENI; JEAN-MARIE FRERE; GIANFRANCO AMICOSANTE; GIAN MARIA ROSSOLINI

2000-01-01

67

Multi-wavelength View of Kiloparsec-scale Clumps in Star-forming Galaxies at z ~ 2  

NASA Astrophysics Data System (ADS)

This paper studies the properties of kiloparsec-scale clumps in star-forming galaxies at z ~ 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 ~ 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 ~10% and together ~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 ~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; Ferguson, Henry C.; Cassata, Paolo; Koekemoer, Anton M.

2012-10-01

68

The Composition of Saturn's Rings and Satellites from Cassini VIMS and UVIS  

NASA Astrophysics Data System (ADS)

Spectra of the rings and icy satellites of Saturn from Cassini UVIS and VIMS, covering from ~0.1 to 5.1 microns show both expected and unusual properties. The spectra of all these objects are dominated by absorption and scattering by water-ice grains, variable amounts of a non-ice material that is strongly absorbing with a stronger UV absorption, small and variable amounts of CO2 and trace amounts of CH compounds, trapped H2, and possible trace NH compounds. The dark material seems to contain the trapped H2, CO2 and NH compounds. Classical interpretations of the UV absorber and dark material are varying amounts of tholins and carbon. A newer interpretation is that the main spectral components are ice + nano-grains of metallic iron, and nano-hematite. Iron is an efficient H2 trap. Iron has the highest absorption coefficient we have found, approaching one million per cm at 0.25 microns. Nano-sized grains create both Rayleigh absorption and Rayleigh scattering producing the variable spectral signatures seen in the Saturn system. The large spectral range of combined UVIS + VIMS spectra provide strong constraints on composition and grain size distribution. Spectra of the rings and all icy satellites indicate a large range of ice grain sizes, from tens of microns to sub-micron. Sub-micron ice grains create unusual spectral properties, including decreased reflectance near 5-microns, decreased 3.1-micron Fresnel peak, decreased 2.6-micron reflectance, asymmetric to longer wavelength 2-micron absorption, reduced 1.5/2-micron ice band depth ratio, and enhanced reflectance at shorter wavelengths, all of which are seen in the spectra of the rings and satellites. In the blue/UV, spectra of the rings and satellites depart from that of ice because of the UV absorber. Some spectra of Saturn's rings are very similar to spectra of some locations on icy satellites, indicating common compounds are spectrally active from the rings to Iapetus. Sub-micron ice grains create Rayleigh scattering into the UV which competes with the UV absorber to create the various spectral shapes seen in the Saturn system.

Clark, R. N.; Bradley, E. T.; Hendrix, A. R.; Cuzzi, J. N.; Cruikshank, D. P.; Filacchione, G.; Pearson, N.; Nicholson, P. D.; Hedman, M. M.; Brown, R. H.; Buratti, B. J.; Baines, K. H.; Sotin, C.; Livo, K. E.; Nelson, R.

2011-12-01

69

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

NASA Astrophysics Data System (ADS)

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

Nelson, Robert

70

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.

Libisch, Balazs; Muzslay, Monika; Gacs, Maria; Minarovits, Janos; Knausz, Marta; Watine, Joseph; Ternak, Gabor; Kenez, Eva; Kustos, Ildiko; Rokusz, Laszlo; Szeles, Klara; Balogh, Boglarka; Fuzi, Miklos

2006-01-01

71

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

72

The Saturnian satellite Rhea as seen by Cassini VIMS  

NASA Astrophysics Data System (ADS)

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 CO2 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 H2O ice-rich cratered terrain of the leading hemisphere. The concentration of H2O 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.

Stephan, Katrin; Jaumann, Ralf; Wagner, Roland; Clark, Roger N.; Cruikshank, Dale P.; Giese, Bernd; Hibbitts, Charles A.; Roatsch, Thomas; Matz, Klaus-Dieter; Brown, Robert H.; Filacchione, Gianrico; Cappacioni, Fabrizio; Scholten, F.; Buratti, Bonnie J.; Hansen, Gary B.; Nicholson, Phil D.; Baines, Kevin H.; Nelson, Robert M.; Matson, Dennis L.

2012-02-01

73

VIM-19, a Metallo-?-Lactamase with Increased Carbapenemase Activity from Escherichia coli and Klebsiella pneumoniae ?  

PubMed Central

Two carbapenem-resistant isolates, one Escherichia coli isolate and one Klebsiella pneumoniae isolate, recovered from an Algerian patient expressed a novel VIM-type metallo-?-lactamase (MBL). The identified blaVIM-19 gene was located on a ca. 160-kb plasmid and located inside a class 1 integron in both isolates. VIM-19 differed from VIM-1 by the Asn215Lys and Ser228Arg substitutions, increasing its hydrolytic activity toward carbapenems. Site-directed mutagenesis experiments showed that both substitutions were necessary for the increased carbapenemase activity of VIM-19. This study indicates that MBLs with enhanced activity toward carbapenems may be obtained as a result of very few amino acid substitutions.

Rodriguez-Martinez, Jose-Manuel; Nordmann, Patrice; Fortineau, Nicolas; Poirel, Laurent

2010-01-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

75

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

Microsoft Academic Search

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

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

2001-01-01

76

Cryovolcanism on Titan: New results from Cassini RADAR and VIMS  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

77

Spectral changes associated with rain on Titan: observations by VIMS  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

78

Preliminary Results Of Titan's Tropical Surface Albedo Using Cassini Vims Measurements  

NASA Astrophysics Data System (ADS)

Titan is shrouded by a thick atmosphere, which limits studies of its surface composition. Cassini's Visual and Infrared Mapping Spectrometer (VIMS) offers an opportunity to investigate Titan's surface at 8 near-IR wavelengths where the atmosphere is relatively transparent and a portion of the reflected sunlight comes from Titan's surface. The challenge is to characterize the scattering and absorption of Titan's atmosphere well enough to determine the surface albedo. To this effect, we designed a discrete ordinates radiative transfer model of its atmosphere, the scattering characteristics of the tropical atmosphere so that it accurately reproduces in situ measurements by Huygens' Descent Imager-Spectral Radiometer (DISR). We limited our study to the tropical region of Titan that is characterized by the same haze and methane conditions measured by Huygens. We determine the surface albedo at 0.93, 1.08, 1.28, 1.58, 2.00, 2.78, and 5.0 microns, between the methane vibrational bands. We present here preliminary results of several tropical regions on Titan where the surface albedo has been accurately determined.

Turner, Jake; Griffith, C. A.; Penteado, P.

2012-10-01

79

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

PubMed

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

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

2012-02-13

80

Power-scaling of Pr:YAlO3 laser operating in CW regime at 747 nm and 720 nm wavelengths  

NASA Astrophysics Data System (ADS)

We report efficient continuous-wave laser operation of laser-diode pumped Pr:YAlO3 crystal in the power-scaled resonator arrangement. Using two pumping GaN-laser-diodes emitting at 448 nm wavelengths with a maximum output power of 1 W each, 290 mW of Pr:YAlO3 output power in the near-infrared spectral region (747 nm) with oscillation threshold of about 500 mW has been reached. The maximum absorbed pump power was approximately 1.5 W resulting in the slope efficiency of 28 %. Moreover, switchable laser operation at two wavelengths (747 nm and 720 nm) has been demonstrated employing the broadband laser resonator mirrors in connection with the tuning element (Lyot filter).

Fibrich, Martin; Jelínková, Helena

2013-03-01

81

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

82

VimA mediates multiple functions that control virulence in Porphyromonas gingivalis.  

PubMed

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 W; Robles, A; Fletcher, H M

2012-12-21

83

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

USGS Publications Warehouse

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

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

2010-01-01

84

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

85

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

NASA Astrophysics Data System (ADS)

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.; Donnelly, T. D.; Ditmire, T.

2007-01-01

86

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

87

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

NASA Astrophysics Data System (ADS)

The latitudinal variation of Saturn's tropospheric composition (NH3, PH3 and AsH3) and aerosol properties (cloud altitudes and opacities) are derived from Cassini/VIMS 4.6-5.1 ?m thermal emission spectroscopy on the planet's nightside (April 22, 2006). The gaseous and aerosol distributions are used to trace atmospheric circulation and chemistry within and below Saturn's cloud decks (in the 1- to 4-bar region). Extensive testing of VIMS spectral models is used to assess and minimise the effects of degeneracies between retrieved variables and sensitivity to the choice of aerosol properties. Best fits indicate cloud opacity in two regimes: (a) a compact cloud deck centred in the 2.5-2.8 bar region, symmetric between the northern and southern hemispheres, with small-scale opacity variations responsible for numerous narrow light/dark axisymmetric lanes; and (b) a hemispherically asymmetric population of aerosols at pressures less than 1.4 bar (whose exact altitude and vertical structure is not constrained by nightside spectra) which is 1.5-2.0× more opaque in the summer hemisphere than in the north and shows an equatorial maximum between ±10° (planetocentric).Saturn's NH3 spatial variability shows significant enhancement by vertical advection within ±5° of the equator and in axisymmetric bands at 23-25°S and 42-47°N. The latter is consistent with extratropical upwelling in a dark band on the poleward side of the prograde jet at 41°N (planetocentric). PH3 dominates the morphology of the VIMS spectrum, and high-altitude PH3 at p < 1.3 bar has an equatorial maximum and a mid-latitude asymmetry (elevated in the summer hemisphere), whereas deep PH3 is latitudinally-uniform with off-equatorial maxima near ±10°. The spatial distribution of AsH3 shows similar off-equatorial maxima at ±7° with a global abundance of 2-3 ppb. VIMS appears to be sensitive to both (i) an upper tropospheric circulation (sensed by NH3 and upper-tropospheric PH3 and hazes) and (ii) a lower tropospheric circulation (sensed by deep PH3, AsH3 and the lower cloud deck).

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

2011-08-01

88

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

89

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

NASA Astrophysics Data System (ADS)

Since entering orbit around Saturn in July 2004, the VIMS instrument on the Cassini spacecraft has observed 15 stellar occultations by Saturn's rings, at incidence angles ranging from 3.5 to 51 degrees. The radial resolution of the resulting optical depth profiles varies from 200 meters to 4 km. We will present selected results from these observations, concentrating on the narrow, kinky, multistranded and eccentric F ring. An initial series of grazing occultations of the long-period variable star, o Ceti yielded eight high S/N profiles of the F ring, revealing a dense central strand of FWHM 25-45 km flanked by inner and outer strands which are variable both in normal optical depth (0.005-0.035) and radial separation from the core (250-465 km). All three strands are embedded in a broad `skirt' of diffuse material which is at least 1200 km wide. These results are qualitatively consistent with Cassini imaging observations (Porco etal. 2005). Despite local radial distortions of up to 50 km, the measured radii of the F ring's core are found to be remarkably consistent with the model developed by Bosh etal. (2002) - based on Voyager and Earth-based occultation data - of an eccentric, inclined keplerian orbit precessing under the influence of Saturn's oblate figure. Our measured radii of the fainter flanking strands, on the other hand, do not appear to support the one-armed trailing spiral model developed by Charnoz etal. (2005). One VIMS profile across the F ring shows evidence for a dense embedded clump, approximately 1 km in diameter, which may correspond to one of the bright pointlike features seen in several Cassini images. This clump was also seen in simultaneous observations by the UVIS instrument (Esposito etal. 2007), where it is clearly seen to be partially transparent (ie., it is not an embedded moonlet).

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

2007-07-01

90

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

91

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

NASA Astrophysics Data System (ADS)

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

Lamy, L.

2011-10-01

92

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

PubMed

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

2007-02-01

93

A new integron carrying VIM2 metallo-?-lactamase gene cassette in a Serratia marcescens isolate  

Microsoft Academic Search

Serratia marcescens is an important nosocomial pathogen which is often resistant to multiple antimicrobial agents. An imipenem-resistant S. marcescens isolate from a urine specimen was found to carry a blaVIM-2 gene cassette on a class 1 integron. This finding indicates that blaVIM-2 is presently spreading even to Serratia spp. in Korea, which could compromise the usefulness of carbapenem in the

Jong Hwa Yum; Dongeun Yong; Kyungwon Lee; Hyon-Suk Kim; Yunsop Chong

2002-01-01

94

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

Microsoft Academic Search

We present the preliminary results of our study on the variations of (1) the vertical aerosol layer structure and (2) the phosphine (PH3) distribution on Saturn, utilizing Cassini\\/VIMS spectral imagery. From the Cassini\\/VIMS infrared channel spectral data of Saturn acquired in 2004, we sample a dozen pixels at each of the following four latitudes (-10, -27, -47, and -73 degree)

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

2006-01-01

95

The vimE gene downstream of vimA is independently expressed and is involved in modulating proteolytic activity in Porphyromonas gingivalis W83.  

PubMed

Regulation/activation of the Porphyromonas gingivalis gingipains is poorly understood. A unique 1.3-kb open reading frame downstream of the bcp-recA-vimA transcriptional unit was cloned, insertionally inactivated with the ermF-ermAM antibiotic resistance cassette, and used to create a defective mutant by allelic exchange. In contrast to the wild-type W83 strain, the growth rate of the mutant strain (designated FLL93) was reduced, and when plated on Brucella blood agar it was nonpigmented and nonhemolytic. Arginine- and lysine-specific gingipain activities were reduced by approximately 90 and 85%, respectively, relative to activities of the parent strain. These activities were unaffected by the culture's growth phase, in contrast to the vimA-defective mutant P. gingivalis FLL92, which has increased proteolytic activity in stationary phase. Expression of the rgpA, rgpB, and kgp gingipain genes was unaltered in P. gingivalis FLL93 compared to that of the wild-type strain. Further, in extracellular protein fractions a 64-kDa band was identified that was immunoreactive with the RgpB-specific proenzyme antibodies. Active-site labeling with dansyl-glutamyl-glycyl-arginyl chloromethyl ketone or immunoblot analysis showed no detectable protein band representing the gingipain catalytic domain. In vitro protease activity could be slightly induced by a urea denaturation-renaturation cycle in an extracellular protein fraction, in contrast to the vimA-defective mutant P. gingivalis FLL92. Expression of flanking genes, including recA, vimA, and Pg0792, was unaltered by the mutation. Taken together, these results suggest that the vimA downstream gene, designated vimE (for virulence-modulating gene E), is involved in the regulation of protease activity in P. gingivalis. PMID:15385452

Vanterpool, Elaine; Roy, Francis; Fletcher, Hansel M

2004-10-01

96

Allosteric inhibition of VIM metallo-?-lactamases by a camelid nanobody.  

PubMed

M?L (metallo-?-lactamase) enzymes are usually produced by multi-resistant Gram-negative bacterial strains and have spread worldwide. An approach on the basis of phage display was used to select single-domain antibody fragments (VHHs, also called nanobodies) that would inhibit the clinically relevant VIM (Verona integron-encoded M?L)-4 M?L. Out of more than 50 selected nanobodies, only the NbVIM_38 nanobody inhibited VIM-4. The paratope, inhibition mechanism and epitope of the NbVIM_38 nanobody were then characterized. An alanine scan of the NbVIM_38 paratope showed that its binding was driven by hydrophobic amino acids. The inhibitory concentration was in the micromolar range for all ?-lactams tested. In addition, the inhibition was found to follow a mixed hyperbolic profile with a predominantly uncompetitive component. Moreover, substrate inhibition was recorded only after nanobody binding. These kinetic data are indicative of a binding site that is distant from the active site. This finding was confirmed by epitope mapping analysis that was performed using peptides, and which identified two stretches of amino acids in the L6 loop and at the end of the ?2 helix. Because this binding site is distant from the active site and alters both the substrate binding and catalytic properties of VIM-4, this nanobody can be considered as an allosteric inhibitor. PMID:23289540

Sohier, Jean S; Laurent, Clémentine; Chevigné, Andy; Pardon, Els; Srinivasan, Vasundara; Wernery, Ulrich; Lassaux, Patricia; Steyaert, Jan; Galleni, Moreno

2013-03-15

97

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

99

Characterization of the New Metallo-?-Lactamase VIM-13 and Its Integron-Borne Gene from a Pseudomonas aeruginosa Clinical Isolate in Spain?  

PubMed Central

During a survey conducted to evaluate the incidence of class B carbapenemase (metallo-?-lactamase [MBL])-producing Pseudomonas aeruginosa strains from hospitals in Majorca, Spain, five clinical isolates showed a positive Etest MBL screening test result. In one of them, strain PA-SL2, the presence of a new blaVIM derivative (blaVIM-13) was detected by PCR amplification with blaVIM-1-specific primers followed by sequencing. The blaVIM-13-producing isolate showed resistance to all ?-lactams (except aztreonam), gentamicin, tobramycin, and ciprofloxacin. VIM-13 exhibited 93% and 88% amino acid sequence identities with VIM-1 and VIM-2, respectively. blaVIM-13 was cloned in parallel with blaVIM-1, and the resistance profile conferred was analyzed both in Escherichia coli and in P. aeruginosa backgrounds. Compared to VIM-1, VIM-13 conferred slightly higher levels of resistance to piperacillin and lower levels of resistance to ceftazidime and cefepime. VIM-13 and VIM-1 were purified in parallel as well, and their kinetic parameters were compared. The kcat/Km ratios for the antibiotics mentioned above were in good agreement with the MIC data. Furthermore, EDTA inhibited the activity of VIM-13 approximately 25 times less than it inhibited the activity of VIM-1. VIM-13 was harbored in a class 1 integron, along with a new variant (Ala108Thr) of the aminoglycoside-modifying enzyme encoding gene aacA4, which confers resistance to gentamicin and tobramycin. Finally, the VIM-13 integron was apparently located in the chromosome, since transformation and conjugation experiments consistently yielded negative results and the blaVIM-13 probe hybridized only with the genomic DNA.

Juan, Carlos; Beceiro, Alejandro; Gutierrez, Olivia; Alberti, Sebastian; Garau, Margalida; Perez, Jose L.; Bou, German; Oliver, Antonio

2008-01-01

100

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

101

Spectrophotometric Modeling of Enceladus Surface Properties and Composition from Vims Data  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

102

Cassini-VIMS Observations of Self-gravity Wakes in Saturn's Rings - II  

NASA Astrophysics Data System (ADS)

Azimuthal variations in the reflectivity (at both visual and radar wavelengths), brightness temperature and optical depth of Saturn's rings have been widely observed and are generally attributed to what are now referred to as 'self-gravity wakes', as observed in numerical models of spontaneous gravitational clumping in a shearing disk. If this wake-dominated picture of the rings is correct, then the variation of transmission with opening angle is likely to deviate from the classical expression, T=e^{-?sin B}, where ? is the normal optical depth and B is the ring opening angle. This expectation is confirmed by recent analyses of both UVIS (Colwell etal. 2007) and VIMS (Hedman etal. 2007) stellar occultation data. By comparing several occultations whose lines of sight are quasi-parallel to the wakes, we can exploit this apparent variation of ? with B to separate the filling fraction of the wakes, f, from the optical depth in the `gaps' between them. We find remarkably consistent results from occultations at 11 °

Nicholson, Philip D.; Hedman, M. M.; Salo, H. J.; Cassini VIMS Team

2008-05-01

103

Investigating Chemical Compositions of Select Saturnian Satellites via Mosaicking of Cassini VIMS Observations.  

NASA Astrophysics Data System (ADS)

Cassini has collected data of many of Saturn's moons which provide information on the surface composition of the satellites and ultimately investigate their chemical and physical history. Mosaics are vital in analyzing the large amounts of data gathered from VIMS. Programs ENVI 4.8 and ISIS 3 were utilized and their results compared to determine optimum efficiency and output when creating mosaics. It was desirable to duplicate the cluster analysis of Mimas performed by Marzo [1] to definitively prove ISIS 3's capability to create mosaics identical to ENVI. Concerning the satellites of Saturn we were interested in searching for evidence of polycyclic aromatic hydrocarbons (PAHs) as well as CO2 via cluster analysis. Preliminary results of Mimas show that the outline of Hershel crater belongs to a different group than the immediate surroundings implicating a variation in the physical properties of the ice. Since the clustering was done focusing on a short wavelength range around the 1.5 micron water band the variation is most likely due to grain size differences as shown by Stephan et al (2005) in their study of Ganymede. The other intriguing feature outlined by the clustering of Mimas is a pattern on the side of the ring outlining the Hershel crater. The representative spectrum of this group shows an anomaly that could be due to contamination of minerals from an impact. Further analysis is necessary to confirm this preliminary result. The ultimate goal of our attempt at reproducing the mosaic independently (with ISIS3) and to repeat the cluster analysis is to investigate this intriguing result.

Hosmer, Laura; Dalle Ore, C.; Mastrapa, R.; Speck, A.

2012-01-01

104

VIMS Observations of Saturn’s Rings Investigated by means of Montecarlo Ray Tracing  

NASA Astrophysics Data System (ADS)

The VIMS instrument onboard Cassini has extensively observed the Saturn’s rings producing a number of mosaics that allow the study of the radial variability of the rings spectral properties at visible and infrared wavelengths. Along with compositional variations some systematic effects induced by observation geometry are observed in the rings spectra, such as phase angle dependence of water ice band depths and spectral reddening. In this paper we investigate the mechanisms at the origin of these photometric effects by adopting a Montecarlo raytracing, in the geometric optics limit. We report about the results obtained from several simulations varying rings physical properties (optical depth, particle size distribution, single particle phase function) in order to investigate the variation of the angular distribution of the light scattered by the ring plane. The results of these simulations indicate that even if the total power reflected by the rings plane is dominated by single scattered light, the multiple scattered fraction (inter-particle scattering) produces a dependence of the spectral features on observation geometry (phase angle) at least for the denser regions of the rings. Moreover using the same Montecarlo code we are able to reproduce the dependence of the spectral features (band depths, spectral slopes) on viewing geometry (incidence, emergence and phase angles). Disentangling illumination effects from rings particle albedo permits a more accurate retrieval of the physical properties (grain size, amount of contaminants) of the regolith that covers the ring particles when radiative transfer models are applied to fit remote sensing spectra. This research is supported by an Italian Space Agency (ASI) grant.

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

2012-10-01

105

A new season of Saturn auroral observations by Cassini/VIMS  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

106

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

107

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

PubMed Central

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

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

2000-01-01

108

Inactivation of vimF, a putative glycosyltransferase gene downstream of vimE, alters glycosylation and activation of the gingipains in Porphyromonas gingivalis W83.  

PubMed

Regulation/activation of the Porphyromonas gingivalis gingipains is poorly understood. A 1.2-kb open reading frame, a putative glycosyltransferase, downstream of vimE, was cloned, insertionally inactivated using the ermF-ermAM antibiotic resistance cassette, and used to create a defective mutant by allelic exchange. In contrast to the wild-type W83 strain, this mutant, designated P. gingivalis FLL95, was nonpigmented and nonhemolytic when plated on Brucella blood agar. Arginine- and lysine-specific gingipain activities were reduced by approximately 97% and 96%, respectively, relative to that of the parent strain. These activities were unaffected by the growth phase, in contrast to the vimA-defective mutant P. gingivalis FLL92. Expression of the rgpA, rgpB, and kgp gingipain genes was unaffected in P. gingivalis FLL95 in comparison to the wild-type strain. In nonactive gingipain extracellular protein fractions, multiple high-molecular-weight proteins immunoreacted with gingipain-specific antibodies. The specific gingipain-associated sugar moiety recognized by monoclonal antibody 1B5 was absent in FLL95. Taken together, these results suggest that the vimE downstream gene, designated vimF (virulence modulating gene F), which is a putative glycosyltransferase group 1, is involved in the regulation of the major virulence factors of P. gingivalis. PMID:15972484

Vanterpool, Elaine; Roy, Francis; Fletcher, Hansel M

2005-07-01

109

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.

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

2012-01-01

110

Imaging of Titan in the infrared with Cassini/VIMS : Toward homogeneous surface maps  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Imaging Spectrometer (VIMS) onboard Cassini has acquired a near global coverage of Titan in 352 wavelengths from 0.3 to 5.1 microns at a medium spatial resolution (10-20 km/pixels). Few percents of the surface have been observed with a resolution better than 5 km/pixel. The surface can be observed in seven narrow "windows" where the atmospheric methane does not absorb. This data set has allowed the cartography and spectral study of a wide range of surface morphological features, such as mountains, channels, dunes, impact craters, lakes, or cryovolcanic areas. However, the integration of the global data set into fully homogeneous global maps is hampered by the coupled effect of surface and atmosphere, which is all the more problematic than the geometry of observation covers a wide range of incidence, emergence and phase angle. Our objective is to find an empirical way to correct the mosaics from this coupled effect. We first study the 5 µm surface window, which is the less affected by the additive component of the signal due to the scattering by the particles in the haze layer. Seams at this wavelength result only from differences of absorption at 5 µm of the atmospheric species and the surface phase function, which are both multiplicative components. Then, we investigate different empirical corrections for the other methane windows (1.08, 1.27, 1.59, 2.03, 2.69, 2.78 microns) by using the 5 µm window as a reference. These windows contain both an additive component due to the scattering of the particles in the atmosphere, and a multiplicative component due to the absorption by aerosols and gas, and the surface phase function. We found in particular that the effect of the atmosphere in these methane windows can be significantly lowered by subtracting the bottom of their wings, which account mainly for the flux reflected by the aerosols in the upper layers of the atmosphere. This is consistent with the first order outputs of a radiative transfer model developed by Rodriguez et al. (2009)

Le Mouélic, Stéphane; Cornet, Thomas; Rodriguez, Sébastien; Sotin, Christophe; Barnes, Jason W.; Brown, Robert H.; Baines, Kevin H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D.

2010-05-01

111

Characterization of the New Metallo Lactamase VIM13 and Its Integron-Borne Gene from a Pseudomonas aeruginosa Clinical Isolate in Spain  

Microsoft Academic Search

During a survey conducted to evaluate the incidence of class B carbapenemase (metallo--lactamase (MBL))-producing Pseudomonas aeruginosa strains from hospitals in Majorca, Spain, five clinical isolates showed a positive Etest MBL screening test result. In one of them, strain PA-SL2, the presence of a new blaVIM derivative (blaVIM-13) was detected by PCR amplification with blaVIM-1-specific primers followed by sequencing. The blaVIM-13-producing

Carlos Juan; Alejandro Beceiro; Olivia Gutierrez; S. Alberti; Margalida Garau; J. L. Perez; G. Bou; A. Oliver

2008-01-01

112

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

Microsoft Academic Search

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,

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

2005-01-01

113

The vimE Gene Downstream of vimA Is Independently Expressed and Is Involved in Modulating Proteolytic Activity in Porphyromonas gingivalis W83  

Microsoft Academic Search

Regulation\\/activation of the Porphyromonas gingivalis gingipains is poorly understood. A unique 1.3-kb open reading frame downstream of the bcp-recA-vimA transcriptional unit was cloned, insertionally inactivated with the ermF-ermAM antibiotic resistance cassette, and used to create a defective mutant by allelic exchange. In contrast to the wild-type W83 strain, the growth rate of the mutant strain (designated FLL93) was reduced, and

Elaine Vanterpool; Francis Roy; Hansel M. Fletcher

2004-01-01

114

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

115

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

116

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

Microsoft Academic Search

Motivated by the possibility that small amounts of adsorbed water may be stable on illuminated portions of the lunar surface, possibly as OH- , (e.g. Starukhina and Shkuratov, 2000; Hibbitts et al., 2009; Dyar et al., 2009; McCord et al., 2009) and to confirm not yet released observations by other spacecraft, we have reanalyzed the VIMS (Visual and Infrared Mapping

C. Hibbitts; G. B. Hansen

2009-01-01

117

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

National Technical Information Service (NTIS)

Teaching aids available from VIMS/Sea Grant Marine Education Center are listed in this inventory. Audio-visual aids listed are in the following categories: 16 mm color films, silent films, 8 mm film loops, filmstrips with cassettes, filmstrips with record...

S. Gammisch

1979-01-01

118

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

ERIC Educational Resources Information Center

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

Gammisch, Sue, Comp.

119

Role of vimA in cell surface biogenesis in Porphyromonas gingivalis  

PubMed Central

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

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

2010-01-01

120

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

Microsoft Academic Search

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

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

2008-01-01

121

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

122

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

123

Titan through the time of Cassini: a database of VIMS observations  

NASA Astrophysics Data System (ADS)

Since Cassini's arrival at Saturn, VIMS has recorded over 104 cubes, containing over 10^7 spectra. This still increasing amount of observations precludes direct inspection of all data, either to select the observations, or to identify the occurrence and time variation of specific spectral or spatial features. Additionally, many VIMS observations are taken as a large number of cubes with small spatial extent, which cannot be meaningfully visualized without assembling mosaics. This work presents titan_browse, a tool developed to deal with these difficulties. Titan_browse comprises both a database of observations, and a visualization tool to inspect them. The database contains every VIMS observation of Titan in the PDS archive, and provides a flexible query system, which can select individual cubes or spatial pixels based on arbitrary functions of the instrumental or photometric data. Once observations are selected, titan_browse can be used to directly inspect them, through mosaics in several map projections, or displaying images of selected bands, or spectra of selected spatial pixels. This allows users to interactively explore the data, to refine queries to obtain those most useful to the intended analysis. The selected cubes or spectra can them be directly exported from the database, either to an IDL session, or to files (one format being the original cubes, in ISIS format). The cubes used in the database were processed to contain more geometric information than either the original PDS files or those that are produced by the VIMS pipeline, including the coordinates of the edges of each spatial pixel (necessary for precise mosaics), and more information on the illumination angles (to aid in analyses of specular reflections). This version of the titan_browse is a complete reimplementation of its previous titan_browse, to overcome the previous coverage and performance limitations, and is the first to be made publicly available.

Penteado, Paulo

2010-04-01

124

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

125

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

126

Emergence of VIM-1-carbapenemase-producing Enterobacter cloacae in Tyrol, Austria.  

PubMed

The rapid emergence and dissemination of carbapenemase-producing Enterobacter species and other members of the Enterobacteriaceae poses a considerable threat to the care of hospitalized patients and to public health. In this study, Enterobacter isolates demonstrating decreased susceptibility to carbapenems detected at the Division of Hygiene and Medical Microbiology, Innsbruck Medical University, between January 2006 and December 2010 were tested for bla(VIM-1), bla(NDM-1), bla(IMP), bla(KPC) and bla(OXA-48) using a multiplex PCR with published primers. PFGE was performed to determine the genetic relatedness. In total, 33 isolates (28 Enterobacter cloacae and 5 Enterobacter aerogenes) were collected during the study period. From 2006 to 2009, between two and seven isolates were found per year. In 2010, a significant increase of carbapenem-resistant strains was observed (n?=?12). The bla(VIM-1) gene was detected in all 28 isolates of E. cloacae. Typing of E. cloacae by PFGE revealed three distinct clusters, the biggest of which contained 18 isolates. These findings demonstrate the emergence of VIM-1-producing Enterobacter in Tyrol, western Austria. The clonal relationship confirms the risk of spread of these organisms and their possible persistence over time. PMID:22194339

Heller, Ingrid; Grif, Katharina; Orth, Dorothea

2011-12-22

127

The Evolution of Saturn's Northern Storm of 2010-2011 and Environs as Viewed by Cassini/VIMS  

NASA Astrophysics Data System (ADS)

Images and spectra acquired by the Visual Infrared Mapping Spectrometer on board the Cassini Orbiter reveal that the current northern storm on Saturn is remarkable for (1) its location - the first significant storm seen in northern mid-latitudes since 1906, (2) its duration - presently approaching 8 months, and (3) its power, as indicated by the relatively massive ammonia-laden clouds it produces that reveal significant, persistent transport of materials over at least one bar of depth (> 30 km of altitude). Situated near 35 degrees north latitude (planetocentric) near the maximum of a westward jet, the storm head moves westward at ~ 2.7 degrees per day, or ~ 27 m/s. Multi-spectral images of the feature and its environs in 352 colors spanning nearly all longitudes were acquired by VIMS on February 24, May 11 and July 12, 2011. In all imagery, the head of the storm appears atypically dark in ammonia-ice sensitive wavelengths 2.73-3.1 micron, indicating significant amounts of ammonia ice. Simultaneously, the feature appears bright at pseudo-continuum near-infrared wavelengths, particularly at 4.08 micron, indicating an atypically massive cloud of large particles. Some 3-5 degree of latitude to the north and south of the cloudhead, streamers of such large-particle ammonia clouds extend more than 150 degrees of longitude to the east. While these streamers appear nearly equivalent in brightness in diagnostic wavelengths in the February 24, 2011 observations, the northern streamer clearly dominates in the May 11, 2011 map. As well, a new dark spot, the first observed associated with this storm, appears more than 250 degrees of longitude downstream of the cloudhead in the May 11, 2011 images and persists through the July 12, 2011 observations. Its appearance may be associated with the dissipation of overlying cloud features as the dark spot wandered eastward, Similar in size (> 3000 km) and spectral appearance to the dark spots associated with the 2008 southern storm (Baines et al, Planetary and Space Sci., 57, 1650-1658,2009), this feature suggests upwelling of materials from the ~10-bar level, as previously proposed for the southern storm. New imagery expected in August 2011 as well as additional analysis of the July, 2011 images will be discussed and dynamical implications presented, including possible relationships of the northern storm with the String of Pearls feature observed for 5 years in the same latitude and longitude range but which has not been observed since the advent of the storm in December 2010.

Baines, K. H.; Momary, T.; Fletcher, L.; Showman, A. P.; Delitsky, M.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.; Sotin, C.

2011-12-01

128

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

129

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

PubMed

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

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

2006-01-19

130

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

131

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

132

Physics of Very Short Wavelength Acceleration  

NASA Astrophysics Data System (ADS)

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

Katsouleas, T.

2006-01-01

133

The General Definition of the p97/Valosin-containing Protein (VCP)-interacting Motif (VIM) Delineates a New Family of p97 Cofactors*  

PubMed Central

Cellular functions of the essential, ubiquitin-selective AAA ATPase p97/valosin-containing protein (VCP) are controlled by regulatory cofactors determining substrate specificity and fate. Most cofactors bind p97 through a ubiquitin regulatory X (UBX) or UBX-like domain or linear sequence motifs, including the hitherto ill defined p97/VCP-interacting motif (VIM). Here, we present the new, minimal consensus sequence RX5AAX2R as a general definition of the VIM that unites a novel family of known and putative p97 cofactors, among them UBXD1 and ZNF744/ANKZF1. We demonstrate that this minimal VIM consensus sequence is necessary and sufficient for p97 binding. Using NMR chemical shift mapping, we identified several residues of the p97 N-terminal domain (N domain) that are critical for VIM binding. Importantly, we show that cellular stress resistance conferred by the yeast VIM-containing cofactor Vms1 depends on the physical interaction between its VIM and the critical N domain residues of the yeast p97 homolog, Cdc48. Thus, the VIM-N domain interaction characterized in this study is required for the physiological function of Vms1 and most likely other members of the newly defined VIM family of cofactors.

Stapf, Christopher; Cartwright, Edward; Bycroft, Mark; Hofmann, Kay; Buchberger, Alexander

2011-01-01

134

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.

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

2004-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

136

Specular Scattering on Titan observed by Cassini VIMS: Liquids in the North Polar Region  

NASA Astrophysics Data System (ADS)

After more than 50 close flybys of Titan by the Cassini spacecraft, it has become clear that features similar in morphology to terrestrial lakes and seas exist on Titan’s surface. Widespread evidence for fluvial erosion, presumably driven by precipitation of liquid methane from Titan’s dense atmosphere is also apparent from these data. Lake-like features have thus far only been observed in Titan’s polar regions. Of these presumed lakes, liquids have only been conclusively identified in Ontario Lacus, a relatively small lake in Titan’s south-polar region. As Titan progresses into northern summer, the much larger lake-like features in the north-polar region identified in Radar data, are becoming directly illuminated for the first time since the arrival of Cassini. This allows the Cassini optical instruments to search for specular reflections to confirm the presence of liquids in these presumed lakes. On July 8th, 2009 the Cassini Visual and Infrared Mapping Spectrometer (VIMS) successfully detected a specular reflection in the north-polar region of Titan. The signal is restricted to the VIMS channels at ~5 µm where most of the incident light reaches the surface without being scattered by aerosols in Titan’s atmosphere. By mapping these observations onto the RADAR image from the T19 flyby, the VIMS specular reflection was found to be associated with the western part of Kraken Mare, one of Titan’s large northern lakes, indicating the lakes surface is mirror like, strongly suggesting it is liquid.

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

2009-12-01

137

First Detection of Metallo-?-Lactamase VIM-2 in Pseudomonas aeruginosa Isolates from Colombia  

PubMed Central

Carbapenem resistance rates in Pseudomonas aeruginosa isolates in Colombia, as in many South American countries, are high for reasons that remain unclear. From our nationwide network, we describe the first detection of the metallo-?-lactamase VIM-2 in clinical isolates of P. aeruginosa from multiple cities within Colombia. Metallo-?-lactamases were not detected in the two centers with the highest imipenem resistance rates. Clonality was noted in five of the eight centers with strains meeting the criteria for molecular typing. The high carbapenem resistance in P. aeruginosa in Colombia may be attributable to a combination of factors, including the presence of metallo-?-lactamases and nosocomial transmission.

Villegas, Maria Virginia; Lolans, Karen; del Rosario Olivera, Maria; Suarez, Carlos Jose; Correa, Adriana; Queenan, Anne Marie; Quinn, John P.

2006-01-01

138

Emergence of VIM-1 metallo-?-lactamase-producing Escherichia coli in a neonatal intensive care unit.  

PubMed

A carbapenem-resistant Escherichia coli isolate was recovered from rectal swab of a 12-day-old female neonate, which was admitted to a Greek neonatal intensive care unit (NICU). Phenotypic testing, polymerase chain reaction assays with sequencing, and plasmid analysis revealed that the isolate harbored a plasmid-mediated bla(VIM-1) metallo-?-lactamase gene. The appearance of a metallo-?-lactamase-producing E. coli in NICU is worrisome. Further surveys are needed to determine whether such Enterobacteriaceae may also be spreading in other NICUs. PMID:21117968

Papadimitriou, Maria; Voulgari, Evangelia; Ranellou, Kyriaki; Koemtzidou, Evangelia; Lebessi, Evangelia; Tsakris, Athanassios

2010-11-30

139

Iapetus surface variability revealed from statistical clustering of a VIMS mosaic  

NASA Astrophysics Data System (ADS)

We present the study of a collection of spectra of Iapetus obtained with VIMS, the Visual and Infrared Mapping Spectrometer on board of Cassini spacecraft. The data evaluated (about 1.3x10^4 spectra from 0.35 to 5.1 micron) were obtained during the second flyby of Iapetus, in September 2007. We apply statistical clustering to address the surface composition of Iapetus. We identify 7 statistically distinct units on Iapetus' surface and compare the main characteristics of their representative spectra (centroids).

Pinilla-Alonso, N.; Marzo, G. A.

2011-11-01

140

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

141

Outbreak Caused by a Multidrug-Resistant Klebsiella pneumoniae Clone Carrying blaVIM-12 in a University Hospital?  

PubMed Central

From November 2006 to April 2007, nine nonrepetitive isolates of Klebsiella pneumoniae with reduced susceptibility or resistance to carbapenems were recovered from clinical specimens from separate patients hospitalized in a tertiary care hospital. The imipenem-EDTA synergy test was positive for all isolates. PCR, sequencing, and transferability experiments revealed the novel blaVIM-12 metallo-?-lactamase gene, which was plasmid mediated and located in a class 1 integron. Pulsed-field gel electrophoresis demonstrated a single macrorestriction pattern, indicating the clonal spread of VIM-12-producing K. pneumoniae.

Tokatlidou, Despina; Tsivitanidou, Maria; Pournaras, Spyros; Ikonomidis, Alexandros; Tsakris, Athanassios; Sofianou, Danae

2008-01-01

142

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

PubMed Central

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

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

2012-01-01

143

Detection of Adsorbed Water and Hydroxyl on the Moon with Cassini VIMS  

NASA Astrophysics Data System (ADS)

Cassini flew by the Moon on August 19, 1999, and the Visual and Infrared Mapping Spectrometer (VIMS) obtained 13 image cubes with a spatial resolution of about 175 km per pixel with spectral coverage over the 3-?m region. The thermal emission from the lunar surface is a low-frequency shape added to the spectra that complicates but does not prevent the search for narrower water and hydroxyl absorptions. Thermal emission is lower in the lunar polar regions due to the lower temperatures, reducing the complications. The thermal emission was removed from the VIMS spectra and the data were searched for the spectral signatures of volatile compounds. Abundances of any detected water are difficult to determine because the amounts of water indicated in the spectra are dependent on the albedo and the grain sizes in the rocks and soils and on the type of mixing. A 3% absorption, for example, ranges from 10 to 1,000 parts per million in a spatially uniform distribution or locally higher. Results will be presented.

Clark, Roger Nelson

2009-09-01

144

Photoclinometry, Morphometry, and Spectroscopy of Titan's Sand Dunes from Cassini/VIMS  

NASA Astrophysics Data System (ADS)

We present results from recent Cassini Visual and Infrared Mapping Spectrometer (VIMS) observations of the sand seas that cover Titan's equatorial region. High-resolution (~500 m/pixel) spectral mapping from the T20 Titan flyby on 2006 October 20 shows the dunes. The dunes themselves, and presumably therefore the sand of which they are comprised, are dark in all of Titan's spectral windows. The spectrum best matches organic material, but a small water-ice component cannot be ruled out. Thus the sand particles cannot be pure water ice but could still be mostly ice by volume but coated by an organic rind at least several microns thick. The dunes are separated by interdunes in some places, but are continuous in others. Where interdunes exist, we are able to map the extent of the substrate units. Where no interdunes exist, we use photoclinometry to ascertain crest-trough-crest heights of between 30 and 70 meters. Dune separations in the T20 observations are just over 2 kilometers from crest to crest; the dunes' orientations are predominantly east-west, but with variations of up to 10 degrees in either direction. A properly designed future VIMS observation would be capable of gathering a resolved profile of the dune slopes to ascertain wind direction and present activity status.

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

2007-12-01

145

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

NASA Astrophysics Data System (ADS)

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

Dybkaer, René

2010-06-01

146

Molecular characterization of VIM-producing Klebsiella pneumoniae from Scandinavia reveals genetic relatedness with international clonal complexes encoding transferable multidrug resistance.  

PubMed

VIM-producing Klebsiella pneumoniae (VPKP) has been identified as a source of hospital outbreaks and is prevalent particularly in the Mediterranean region. In this study we have characterized eight VPKP isolates identified in Scandinavia during 2005-2008. With the exception of one isolate, all were from patients with recent history of hospitalization abroad (Greece, n = 6; Turkey, n = 1). Multilocus sequence typing (MLST) resulted in five sequence types (STs), ST36 (n = 1), ST147 (n = 4), ST272 (n = 1), ST273 (n = 1) and ST383 (n = 1), which except for ST272 were part of putative international clonal complexes. All were multidrug resistant due to the presence of other resistance determinants, including extended-spectrum ?-lactamases (CTX-M-3, SHV-5 and SHV-12), 16S rRNA methylases (ArmA) and plasmid-mediated quinolone resistance determinants (QnrS). One isolate harboured a novel VIM-variant (VIM-26) while VIM-1 and VIM-19 were detected in six and one isolate, respectively. Two different genetic structures surrounding the bla(VIM) gene were identified in four isolates. In two isolates bla(VIM-1) and bla(VIM-26) were located in an integron similar to In-e541 (intI1;bla(VIM-1/-26);aacA7; dhfrI;aadA1;3'CS) while in the other two isolates bla(VIM-1) was located in an integron lacking 3'CS but with an IS26 element in the 3'end (intI1;bla(VIM-1);aac(6')-Ib;IS26), as identified in the IncN plasmid pKOX105. The bla(VIM) -genes were located on transferable plasmids ranging from ?40 to ?240 kb and associated with Tn21 in four isolates. PCR-based replicon typing indicated association of bla(VIM) with IncN (n = 3) and A/C (n = 1) broad-host-range plasmids but also with unknown replicons (n = 4). In conclusion, Scandinavian VPKP is associated with importation and genetically related to international clones encoding transferable plasmid-mediated multidrug resistance. PMID:21595797

Samuelsen, Ø; Toleman, M A; Hasseltvedt, V; Fuursted, K; Leegaard, T M; Walsh, T R; Sundsfjord, A; Giske, C G

2011-05-20

147

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

NASA Astrophysics Data System (ADS)

In this study we measure physical parameters of the same set of 155 M- and X-class solar flares observed with AIA/SDO as analyzed in Paper I, by performing a differential emission measure analysis to determine the flare peak emission measure EM p , peak temperature Tp , electron density np , and thermal energy E th, in addition to the spatial scales L, areas A, and volumes V measured in Paper I. The parameter ranges for M- and X-class flares are log (EM p ) = 47.0-50.5, Tp = 5.0-17.8 MK, np = 4 × 109-9 × 1011 cm–3, and thermal energies of E th = 1.6 × 1028-1.1 × 1032 erg. We find that these parameters obey the Rosner-Tucker-Vaiana (RTV) scaling law T_p^2 \\propto n_p L and HvpropT 7/2 L –2 during the peak time tp of the flare density np , when energy balance between the heating rate H and the conductive and radiative loss rates is achieved for a short instant and thus enables the applicability of the RTV scaling law. The application of the RTV scaling law predicts power-law distributions for all physical parameters, which we demonstrate with numerical Monte Carlo simulations as well as with analytical calculations. A consequence of the RTV law is also that we can retrieve the size distribution of heating rates, for which we find N(H)vpropH –1.8, which is consistent with the magnetic flux distribution N(?)vprop?–1.85 observed by Parnell et al. and the heating flux scaling law FH vpropHLvpropB/L of Schrijver et al.. The fractal-diffusive self-organized criticality model in conjunction with the RTV scaling law reproduces the observed power-law distributions and their slopes for all geometrical and physical parameters and can be used to predict the size distributions for other flare data sets, instruments, and detection algorithms.

Aschwanden, Markus J.; Shimizu, Toshifumi

2013-10-01

148

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

PubMed Central

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

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

2012-01-01

149

Wavelength conversion device  

US Patent & Trademark Office Database

A feature of a wavelength conversion device of this invention is the board range of selection of wavelengths which can be obtained by conversion. A wavelength conversion device of this invention comprises an SC light generation portion 12, which receives an excitation light pulse output from an excitation light pulse source and generates SC light, and an optical wavelength filter 14 which filters the SC light. An excitation light pulse source generates an excitation light pulse, of central wavelength .lamda..sub.S. When the excitation light pulse generated by the excitation light pulse source is incident on the SC medium, SC light having a flat spectral shape over the range from wavelength .lamda..sub.L to wavelength .lamda..sub.H (where .lamda..sub.L<.lamda..sub.H) is generated. The optical wavelength filter has a characteristic such that the filtering transmitted central wavelengths are .lamda..sub.1, .lamda..sub.2, .lamda..sub.3, . . . , .lamda..sub.n (where n is a natural number). A further feature is that the following conditions (1) and (2-1), (2-2), . . . , (2-n) between the wavelength .lamda..sub.L, the wavelength .lamda..sub.H, the wavelength .lamda..sub.S, and the wavelengths .lamda..sub.1, .lamda..sub.2, .lamda..sub.3, . . . , .lamda..sub.n (where n is a natural number) are satisfied. .lamda..sub.L<.lamda..sub.S<.lamda..sub.H (1) .lamda..sub.L<.lamda..sub.1<.lamda..sub.H (2-1) .cndot. .cndot. .cndot. .lamda..sub.L<.lamda..sub.n<.lamda..sub.H (2-n)

2006-04-25

150

The Vertical Composition of Titan’s Atmosphere observed by VIMS/Cassini Solar Occultations  

NASA Astrophysics Data System (ADS)

The VIMS instrument has acquired 10 solar occultations since the beginning of the Cassini-Huygens mission. This dataset covers different seasons and latitudes and allows to study a large part of the atmosphere (between 50 and 700 km) by the acquisition of spectra in the infrared range (1-5 µm) with a vertical resolution of ~ 10 km on average. We present here the vertical profiles of gases and other atmospheric components, together with their spatial and temporal evolution, for a selection of VIMS occultations. Two main components of Titan's atmosphere, CH4 and CO, are observed in particular. Methane presents strong bands at 1.2, 1.4, 1.7, 2.3 and 3.2 µm. Its vertical profile, computed by the inversion of the 2.3 µm band, shows an almost constant abundance of ~ 1.2-1.3% above 250 km, less than the reference value of 1.41% from the GSMS instrument (Niemann et al. 2010). CO is detectable below ~ 160 km through its band at 4.7 µm. The resulting profiles are in good agreement with CIRS results that indicate a constant mixing ratio of 50 ppm (De Kok et al. 2007). Other spectral signatures have been detected by VIMS solar occultations. The strongest of these signatures is blended with the 3.2 µm CH4 band. It is centered at 3.4 µm and was discovered by a previous analysis of one solar occultation (Bellucci et al. 2009). It has been attributed to the C-H stretch by alkanes and aromatics present in Titan’s aerosols. An additional absorption observed at 2.4 µm, within the 2 µm methane band, can tentatively be attributed to overtone signatures of this C-H stretch. We are discussing this interpretation and its implications on the composition of aerosols and their temporal and spatial variability. Other bands at 2.7 and 4.2 µm have been detected for the first time by the present study and are still unidentified. Their characteristics and possible attribution are analyzed.

Maltagliati, Luca; Vinatier, S.; Bezard, B.; Sotin, C.; Sicardy, B.; Nicholson, P. D.; Hedman, M.; Clark, R. N.; Brown, R. H.

2013-10-01

151

What's a Wavelength?  

NSDL National Science Digital Library

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

University Of Houston

152

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

153

Simulation of full-scale backscattering measurements of a radar with a knife-edge beam by using radio probing data in the centimeter wavelength band  

NASA Astrophysics Data System (ADS)

We propose an algorithm for conversion of the data obtained by using a centimeter-wave radar designed to measure precipitation intensity to the data obtained by using a radar with a knife-edge beam. This opens up the way for simulation of satellite-based measurements with a knife-edge beam radar at the development stage with high confidence. Processing of the converted centimeter-wave radar data confirmed the efficiency of the algorithms used to reconstruct the dispersion of swelling tilts. A technique is proposed to form a panoramic image of the sea surface, and its operability is proved by analysis of the centimeter-wave radar data. This technique will allow one to reveal and study manifestations of large-scale wave processes on the sea surface.

Karaev, V. Yu.; Meshkov, E. M.; Chu, X.; He, Y.

2012-05-01

154

VIM-2-producing Multidrug-Resistant Pseudomonas aeruginosa ST175 Clone, Spain  

PubMed Central

A total of 183 patients were colonized or infected with multidrug-resistant Pseudomonas aeruginosa isolates at a hospital in Spain during 2007–2010; prevalence increased over this period from 2.8% to 15.3%. To characterize these isolates, we performed molecular epidemiologic and drug resistance analysis. Genotyping showed that 104 (56.8%) isolates belonged to a single major clone (clone B), which was identified by multilocus sequence typing as sequence type (ST) 175. This clone was initially isolated from 5 patients in 2008, and then isolated from 23 patients in 2009 and 76 patients in 2010. PCR analysis of clone B isolates identified the blaVIM-2 gene in all but 1 isolate, which harbored blaIMP-22. ST175 isolates were susceptible to only amikacin (75%) and colistin (100%). Emergence of the ST175 clone represents a major health problem because it compromises therapy for treatment of P. aeruginosa nosocomial infections.

Viedma, Esther; Juan, Carlos; Villa, Jennifer; Barrado, Laura; Orellana, M. Angeles; Sanz, Francisca; Otero, Joaquin R.; Oliver, Antonio

2012-01-01

155

Characterization of Inclusions in VIM/VAR NiTi Alloys  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

156

Haze and clouds properties and distribution on Titan with VIMS instrument  

NASA Astrophysics Data System (ADS)

The VIMS instrument onboard Cassini observed the north polar region the 28th december 2006, and detected a vast polar cloud. Aside from this cloud, the observation also gives information about the haze layer in this region. The data that we use do not allow to probe down to the surface. In this work, we characterized the stratosphere haze layer, the troposphere scatterers and the polar cloud. We give new constraints about the optical constant of the aerosol material around 2.8 m, and we are able to draw a new spectral behaviour for the haze refractive index between about 0.4 and 4.0 m from various sources. We also indentify the origin of spectral features in the 2.8 m methane window, which are mainly due to CH3D.

Rannou, P.; Sotin, C.; Lemouelic, S.; Rodriguez, S.; Cours, T.; Brown, R.; Clark, R.; Barnes, J.; Baines, K.; Buratti, B.

2009-04-01

157

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

158

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

160

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

NASA Astrophysics Data System (ADS)

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

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

161

Geology of the Selk Crater Region of Titan from Cassini VIMS Observations  

NASA Astrophysics Data System (ADS)

Observations of Titan obtained by Cassini VIMS have revealed Selk crater, a geologically young bright-rimmed impact crater, located 800 km north-northwest of the Huygens landing site. The crater rim-crest diameter is 95 km; its floor diameter is 55 km. A central-peak complex, 20 km in diameter, is suggested in the VIMS data. The inner rim of Selk crater is fluted, probably by eolian erosion, while the outer flank and presumed ejecta blanket appear dissected by drainages, likely the result of pluvial erosion. Terracing is observed on the northern and western walls of Selk forming a terrace zone approximately 20 km wide. The polygonal appearance of the crater likely results from two preexisting planes of weakness. We conclude Selk crater is a typical complex impact crater exhibiting morphology and morphometry similar to complex lunar craters. A generally bright terrain that exhibits similar infrared color variation and contrast to Selk crater extends east-southeast from the crater several hundred km; we informally refer to this terrain as the Selk "bench". The Belet dune field surrounds both Selk crater and the bench. Multiple hypotheses for the genesis of the bench include: wind shadowing in the lee of Selk crater preventing the encroachment of dunes, impact-induced cryovolcanism, flow of a fluidized ejecta blanket (similar to the bright crater outflows observed on Venus), and erosion of a streamlined upland by erosive fluid flow, either liquid or gas, formed in the lee of Selk. Vestigial circular outlines in the bench just east of Selk's ejecta blanket suggest that this might be a remnant of an ancient cratered crust. The southern margin of the bench evidently has sufficient relief to prevent the encroachment of dunes. We conclude that the bench either represents a relatively high-viscosity fluidized ejecta flow or a streamlined upland that formed downstream from Selk crater.

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

2009-09-01

162

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

Microsoft Academic Search

We investigated the phenotypic and genetic properties of metallo--lactamase-producing Pseudomonas isolates collected at a tertiary-care hospital in Korea since 1995. The prevalence of imipenem resistance among Pseudomonas aeruginosa isolates reached 16% in 1997, when 9% of the resistant organisms were found to produce VIM-2 -lactamase, a class B enzyme previously found only in P. aeruginosa isolates from Europe. VIM-2-producing isolates

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

2002-01-01

163

Short wavelength FELS  

SciTech Connect

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

Sheffield, R.L.

1991-01-01

164

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

165

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

166

Longer wavelength EUV lithography (LW-EUVL)  

NASA Astrophysics Data System (ADS)

Extreme UV Lithography (EUVL) is generally accepted as the leading candidate for next generation lithography. Several challenges remain for EUVL, especially as its insertion point is pushed to finer resolution. Although diffractive scaling may suggest a transition to shorter EUVL wavelengths, several issues arise that would make that difficult. Challenges involve issues such as flare, multilayer (ML) bandwidth, and reflector throughput which tend to worsen with decreasing wavelength. In this study, we have evaluated the tradeoff between flare scaling effects and diffractive scaling effects for EUVL, where flare induced image degradation is likely to dominate as sub-13.5 nm wavelengths are considered. With surface scatter effects scaling as 1/?2, the idea of longer wavelength (LW-EUVL) becomes interesting. Since a working wavelength is driven by the selection of ML materials (which are molybdenum and silicon for 13.5 nm), the identification of suitable alternatives is an initial challenge. We have optimized aluminum and various refractory metals at 17.2 nm and present results. The optimized combination of aluminum with yttrium, zirconium, and other metals result in theoretical reflectivity values above 75%. We also describe possibilities for alternative LW-EUVL sources for 17.2 nm operation as well as the impact on resist absorption, especially through halogens of higher molar absorption (such as fluorine). The impact on mask absorber materials is also presented, which may also exhibit increased absorbance, leading to a lowering of film thickness requirements.

Maloney, Christopher W.; Smith, Bruce W.

2012-03-01

167

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

168

Multi-wavelength Studies Of Saturn's Rings To Constrain Ring Particle Properties And Ring Structure  

NASA Astrophysics Data System (ADS)

The characteristics of Saturn’s ring particles and their regoliths are examined by modeling variations in brightness, color, temperature and spectral parameters with changing viewing geometry over a wide range of wavelengths. Data from Cassini CIRS, ISS, VIMS and UVIS scans of the lit and unlit main rings at multiple geometries and solar elevations are used. Using multi-wavelength data sets allows us to test different thermal models by combining effects of particle albedo, regolith grain size and surface roughness with thermal emissivity and inertia, and particle spin rate and spin axis orientation. Over a range of solar elevations the CIRS temperature and ISS color variations are confined primarily to phase angle with only small differences from changing spacecraft elevation. Color and temperature dependence with varying solar elevation angle are also observed. Brightness dependence with changing solar elevation angle and phase angle is observed with UVIS. VIMS observations show that IR water ice absorption band depths are a very weak function of phase angle, out to 140 deg phase, suggesting that interparticle light scattering is relatively unimportant except at very high phase angles. These results imply that the individual properties of the ring particles may play a larger role than the collective properties of the rings, in particular at visible wavelengths. The temperature and color variation with phase angle may be a result of scattering within the regolith and on possibly rough surfaces of the clumps, as well as a contribution from scattering between individual particles in a many-particle-thick layer. Preliminary results from our joint studies will be presented. This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2012 California Institute of Technology. Government sponsorship is acknowledged.

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

2012-10-01

169

Metallic Iron and Iron Oxide as an Explanation for the Dark Material Observed on Saturn's Icy Satellites and Rings with Cassini VIMS  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Mapping Spectrometer (VIMS) on Cassini has obtained spatially resolved spectra on satellites of Saturn. The Cassini Rev 49 Iapetus fly-by on September 10, 2007, provided data on both the dark material and the transition zone between the dark material and the visually bright ice. The dark material has low albedo with a linear increase in reflectance with wavelength, 3-micron water, and CO2 absorptions. The transition between bright and dark regions shows mixing with unusual optical properties including increased blue scattering and increasing strength of a UV absorber in areas with stronger ice absorptions. Similar spectral effects are observed on other Saturnian satellites and in the rings. We have been unable to match these spectral properties and trends using tholins and carbon compounds. However, the dark material is spectrally matched by fine-grained metallic iron plus nano-phase hematite and adsorbed water which contribute UV and 3-micron absorption, respectively. The blue scattering peak and UV absorption can be explained by Rayleigh scattering from sub-micron particles with a UV absorption, or a combination of Rayleigh scattering and Rayleigh absorption as has been attributed to spectral properties of the Moon. A new radiative transfer model that includes Rayleigh scattering and Rayleigh absorption has been constructed. Models of ice, sub-micron metallic iron, hydrated iron oxide, and trace CO2 explain the observed spectra. Rayleigh absorption requires high absorption coefficient nano-sized particles, which is also consistent with metallic iron. The UV absorber appears to have increased strength on satellite surfaces close to Saturn, with a corresponding decrease in metallic iron signature. A possible explanation is that the iron is oxidized closer to Saturn by oxygen in the extended atmosphere of Saturn's rings, or the dark material is simply covered by clean fine-grained ice particles, for example, from the E-ring.

Clark, Roger Nelson; Cruikshank, D. P.; Jaumann, R.; Brown, R. H.; Dalle Ore, C.; Stephan, K.; Hoefen, T. M.; Curchin, J. M.; Buratti, B. J.; Filacchione, G.; Baines, K. H.; Nicholson, P. D.

2010-10-01

170

Virtual Interactive Musculoskeletal System (VIMS) in orthopaedic research, education and clinical patient care.  

PubMed

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 Y S; Armiger, Robert S; Yoshida, Hiroaki; Lim, Jonathan; Haraguchi, Naoki

2007-03-08

171

Linear wavelength spectrometer  

Microsoft Academic Search

Generally, a spectrometer uses a diffraction grating to spread the spectral components of a light incident on the diffraction grating on a one-dimensional detector. The detector is composed of pixels linearly distributed along a line. However, the diffracted light is not spread linearly on the detector which means that the wavelength on pixel 1 is not linearly correlated with the

Simon Thibault

2001-01-01

172

Ultraviolet Wavelength Smoke Detector.  

National Technical Information Service (NTIS)

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

T. M. Trumble

1975-01-01

173

Short wavelength laser  

DOEpatents

A short wavelength laser is provided that is driven by conventional-laser pulses. A multiplicity of panels, mounted on substrates, are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path. When the panels are illuminated by the conventional-laser pulses, single pass EUV or soft x-ray laser pulses are produced.

Hagelstein, P.L.

1984-06-25

174

Wavelength conversion in WDM networking  

Microsoft Academic Search

Wavelength conversion has been proposed for use in wavelength-division multiplexed networks to improve efficiency. This study highlights systems challenges and performance issues which need to be addressed in order to incorporate wavelength conversion effectively. A review\\/survey of the enabling technologies, design methods, and analytical models used in wavelength-convertible networks is provided

Byrav Ramamurthy; Biswanath Mukherjee

1998-01-01

175

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

176

Sub-wavelength diffractive optics  

SciTech Connect

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

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

1998-03-01

177

Deformation and shape measurement using multiple wavelength microscopic TV holography  

NASA Astrophysics Data System (ADS)

Characterization of deformation and surface shape is an important parameter in quality testing of micro-objects in view of the functionality, reliability, and integrity of the components. Single-wavelength TV holography is widely used for deformation analysis. However, the single-wavelength TV holographic configuration suffers from overcrowding of fringes for large deformation that sets a limitation due to speckle decorrelation for quantitative fringe analysis. Furthermore, shape cannot be determined when using single wavelength. In this paper, we describe a multiple-wavelength microscopic TV holographic configuration that uses sequentially recorded phase-shifted frames at three different wavelengths before and after deformation of the specimen for evaluation of relatively large deformation fields at the effective wavelengths. Use of multiple wavelengths for deformation and shape evaluation is discussed. The design of the system along with the experimental results on small-scale rough specimens under static load is presented.

Kumar, U. Paul

2009-02-01

178

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

179

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

180

Constraints on the Variability of the Tropospheric Methane Abundance on Titan from Cassini VIMS Observations  

NASA Astrophysics Data System (ADS)

Titan's methane cycles between the atmosphere and the surface, similarly to the hydrological cycle on Earth, as its frequently observed clouds and surface fluvial features indicate. With the constant loss of methane due to photolysis, a surface source is needed to preserve the current high methane abundance in the atmosphere. However, no liquid surfaces or active volcanism have been identified so far, so that the surface branch of Titan's hydrological cycle and its interaction with the atmosphere are yet largely unconstrained. The lack of large liquid surfaces and the preferential occurence of the methane clouds in small areas in the south suggest that the methane distribution on Titan's troposphere might be highly variable, confining the clouds to regions near the surface sources. We present Cassini VIMS (Visual and Infrared Mapping Spectrometer) observations of the 0.64µm methane band, and the constraints on the spatial variation of methane abundance derived from it. The depth of the band is sensitive to the methane as well as the scattering of light by the haze, which increases the apparent methane optical depth. In order to separate the effect of variation in the methane abundance to that of the haze, we compare the methane band depth to the haze optical depth. We find that the band increases to the south of Titan's equator, independently from the haze variation. To quantify the methane variation, we reproduce the observed spectra with radiative transfer models based on the haze properties and vertical distribution at the equatorial region derived by the Huygens DISR (Descent Imager and Spectral Radiometer) team. We find that the band is most sensitive to the higher troposphere and the methane abundance at 20-40 km altitude. We present constraints on the latitudinal distribution of haze, tropospheric methane, and discuss their uncertainties.

Paulo, Penteado F.; Griffith, C.; VIMS Team

2006-09-01

181

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

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

182

Short wavelength laser  

DOEpatents

A short wavelength laser (28) is provided that is driven by conventional-laser pulses (30, 31). A multiplicity of panels (32), mounted on substrates (34), are supported in two separated and alternately staggered facing and parallel arrays disposed along an approximately linear path (42). When the panels (32) are illuminated by the conventional-laser pulses (30, 31), single pass EUV or soft x-ray laser pulses (44, 46) are produced.

Hagelstein, Peter L. (Livermore, CA)

1986-01-01

183

Millimeter-wavelength observations of minor planets  

NASA Astrophysics Data System (ADS)

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

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

1994-07-01

184

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

NASA Astrophysics Data System (ADS)

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 be accurately implemented to these types of nonlinear equations. The results of HPM and VIM confirm the correctness of those obtained by Adomian decomposition method.

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

185

Feedback stabilization of the SCA/FEL wavelength  

NASA Astrophysics Data System (ADS)

The Stanford superconducting accelerator/free electron laser provides the unique ability to modulate laser wavelength on fast time scales by electronically varying the energy of the electron beam. Through the use of an appropriate feedback circuit, this offers us the opportunity to stabilize the laser wavelength. Our first attempt at frequency response measurement and stabilization is discussed, as are possibilities for future work.

Marziali, A.; Smith, T. I.

1993-07-01

186

Atmospheric Intensity Scintillation of Stars. II. Dependence on Optical Wavelength  

Microsoft Academic Search

Atmospheric intensity scintillation of stars on milli- and microsecond time scales was extensively measured at the astronomical observatory on La Palma (Canary Island). Scintillation statistics and temporal changes were discussed in Paper I, while this paper shows how scintillation depends on optical wavelength. Such effects originate from the changing refractive index of air, and from wavelength-dependent diffraction in atmospheric inhomogeneities.

D. Dravins; L. Lindegren; E. Mezey; A. T. Young

1997-01-01

187

Dynamic digital holographic wavelength filtering  

Microsoft Academic Search

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

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

1998-01-01

188

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

Microsoft Academic Search

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

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

2010-01-01

189

Routing and Wavelength Assignment in Wavelength Division Multiplexing Networks  

Microsoft Academic Search

\\u000a The problem of wavelength routing and assignment (WRA) to lighpaths in a multi-hop wavelength division multiplexed (WDM) optical\\u000a network has been addressed in this paper. The wavelength assignment problem has been solved by mapping it to a heuristic based\\u000a clique partitioning problem. For routing a connection, K-shortest paths are found out and a path having minimum link interference\\u000a with other

Ajit Pal; Umesh Patel

2004-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

191

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

PubMed

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

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

2013-04-18

192

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

NASA Astrophysics Data System (ADS)

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 Mouélic 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.

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

2012-01-01

193

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

194

The Atmospheres of Saturn and Titan in the Near-Infrared First Results of Cassini/vims  

NASA Astrophysics Data System (ADS)

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.

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

2005-06-01

195

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

NASA Astrophysics Data System (ADS)

One atmospheric science objective of VIMS is to measure windspeeds of cloud features in the Saturnian system at known altitudes, as determined from the 352 spectral bands that VIMS provides. The Titan encounter of 2 July 2004 provided the first opportunity to measure cloud-tracked winds on Titan. Spectral imagery revealed that cloud coverage of Titan was sparse, covering less than 1.5% of the observed sunlit surface. Nevertheless several clouds were followed during the encounter. The most prominent cloud, comprising the bulk of the cloud coverage, was located near the South Pole ( 87 degrees south, 0 degrees lon) and was roughly circular with a diameter of 600 ± 110 km. We tracked this feature over 11 images spanning a 13 hour period. In an attempt to quantify movement of the clouds in a Titanian windstream, we navigated the clouds using three distinct methods: 1) by tracking the brightest pixel in each cloud feature and employing SPICE kernel derived geometry, 2) similarly, by tracking the centroid of the main cloud feature, and 3) for the first time for an outer solar system body, by tracking relative to surface features seen in atmospheric spectral windows, most notably at 2.02 microns. The variable brightness of the most prominent cloud feature and its proximity to the South Pole of Titan make it rather difficult to track accurately. However, preliminary results obtained by tracking the centroid of the main cloud feature, as well as by tracking relative to surface features, indicate that there is little movement over a period of 13 hours. Specifically, we measure a mean windspeed of 0.5 ± 3.3 m/s in the prograde direction.

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

2004-11-01

196

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

National Technical Information Service (NTIS)

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

J. W. Montano

1986-01-01

197

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

198

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

199

Emergence of Multidrug-Resistant Klebsiella pneumoniae Isolates Producing VIM-4 Metallo-?-Lactamase, CTX-M-15 Extended-Spectrum ?-Lactamase, and CMY-4 AmpC ?-Lactamase in a Tunisian University Hospital?  

PubMed Central

Klebsiella pneumoniae clinical isolates resistant to carbapenems were recovered from 11 patients in the hospital of Sfax, Tunisia. The isolates were closely related as shown by pulsed-field gel electrophoresis, and they produced VIM-4 metallo-enzyme, CTX-M-15 extended-spectrum ?-lactamase, and CMY-4 AmpC enzyme. The blaVIM-4 gene is part of a class 1 integron.

Ktari, Sonia; Arlet, Guillaume; Mnif, Basma; Gautier, Valerie; Mahjoubi, Fouzia; Ben Jmeaa, Mounir; Bouaziz, Mounir; Hammami, Adnane

2006-01-01

200

Long-wavelength microinstabilities in toroidal plasmas  

SciTech Connect

Realistic kinetic toroidal eigenmode calculations have been carried out to support a proper assessment of the influence of long-wavelength microturbulence on transport in tokamak plasmas. In order to efficiently evaluate large-scale kinetic behavior extending over many rational surfaces, significant improvements have been made to a toroidal finite element code used to analyze the fully two-dimensional (r,[theta]) mode structures of trapped-ion and toroidal ion temperature gradient (ITG) instabilities. It is found that even at very long wavelengths, these eigenmodes exhibit a strong ballooning character with the associated radial structure relatively insensitive to ion Landau damping at the rational surfaces. In contrast to the long-accepted picture that the radial extent of trapped-ion instabilities is characterized by the ion-gyroradius-scale associated with strong localization between adjacent rational surfaces, present results demonstrate that under realistic conditions, the actual scale is governed by the large-scale variations in the equilibrium gradients. Applications to recent measurements of fluctuation properties in TFTR L-mode plasmas indicate that the theoretical trends appear consistent with spectral characteristics as well as rough heuristic estimates of the transport level. Benchmarking calculations in support of the development of a three-dimensional toroidal gyrokinetic code indicate reasonable agreement with respect to both the properties of the eigenfunctions and the magnitude of the eigenvalues during the linear phase of the simulations of toroidal ITG instabilities.

Tang, W.W.; Rewoldt, G.

1993-01-01

201

Long-wavelength microinstabilities in toroidal plasmas  

SciTech Connect

Realistic kinetic toroidal eigenmode calculations have been carried out to support a proper assessment of the influence of long-wavelength microturbulence on transport in tokamak plasmas. In order to efficiently evaluate large-scale kinetic behavior extending over many rational surfaces, significant improvements have been made to a toroidal finite element code used to analyze the fully two-dimensional (r,{theta}) mode structures of trapped-ion and toroidal ion temperature gradient (ITG) instabilities. It is found that even at very long wavelengths, these eigenmodes exhibit a strong ballooning character with the associated radial structure relatively insensitive to ion Landau damping at the rational surfaces. In contrast to the long-accepted picture that the radial extent of trapped-ion instabilities is characterized by the ion-gyroradius-scale associated with strong localization between adjacent rational surfaces, present results demonstrate that under realistic conditions, the actual scale is governed by the large-scale variations in the equilibrium gradients. Applications to recent measurements of fluctuation properties in TFTR L-mode plasmas indicate that the theoretical trends appear consistent with spectral characteristics as well as rough heuristic estimates of the transport level. Benchmarking calculations in support of the development of a three-dimensional toroidal gyrokinetic code indicate reasonable agreement with respect to both the properties of the eigenfunctions and the magnitude of the eigenvalues during the linear phase of the simulations of toroidal ITG instabilities.

Tang, W.W.; Rewoldt, G.

1993-01-01

202

Multiple-wavelength plasmonic nanoantennas.  

PubMed

We propose a type of photonic-plasmonic antennas capable of focusing light into subwavelength focal point(s) at several wavelengths, which are formed by embedding conventional dimer gap or bow-tie nanoantennas into multiple-periodic gratings. Fano-type coupling between localized surface plasmon resonances of dimer antennas and photonic modes in the gratings adds new functionalities, including multiple-wavelength operation and controllable enhancement of the field intensity in the focal point. Multiple-wavelength operation of nanoantennas provides tremendous opportunities for broadband single-molecule fluorescence and Raman sensing, emission enhancement, and near-field imaging. PMID:20160810

Boriskina, Svetlana V; Dal Negro, Luca

2010-02-15

203

Providencia isolates carrying bla PER1 and bla VIM2 genes: Biofilm-forming capacity and biofilm inhibitory concentrations for carbapenem antibiotics  

Microsoft Academic Search

Multidrug-resistant clinical isolates of Providentia carrying bla\\u000a PER-1 and bla\\u000a VIM-2 were evaluated for the abilities to form biofilm and high biofilm forming capacity was demonstrated in them. Minimum biofilm\\u000a inhibitory concentrations (MBICs), minimum biofilm eradication concentrations (MBECs), and minimum inhibitory concentrations\\u000a (MICs) for imipenem and meropenem were also determined. In all tested strains, the MBICs were higher than the

Jungmin Kim; Shukho Kim; Hee Woo Lee; Sung Min Kim; Sung Yong Seol

2011-01-01

204

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

PubMed Central

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

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

2012-01-01

205

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

Microsoft Academic Search

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

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

2008-01-01

206

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

Microsoft Academic Search

A novel OXA-type enzyme, named OXA-46, was found to be encoded by a gene cassette inserted into a class 1 integron from a multidrug-resistant Pseudomonas aeruginosa clinical isolate. The variable region of the integron also contained a blaVIM-1 metallo--lactamase cassette and a duplicated aacA4 aminoglycoside acetyltransferase cassette. OXA-46 belongs to the OXA-2 lineage of class D -lactamases. It exhibits 78%

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

2005-01-01

207

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

Microsoft Academic Search

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

J. W. Montano

1986-01-01

208

Establishing Clonal Relationships between VIM-1-Like Metallo-?-Lactamase-Producing Pseudomonas aeruginosa Strains from Four European Countries by Multilocus Sequence Typing?  

PubMed Central

Ten multidrug-resistant Pseudomonas aeruginosa strains producing VIM-1-like acquired metallo-?-lactamases (MBLs), isolated from four European countries (Greece, Hungary, Italy, and Sweden), were analyzed for genetic relatedness by several methodologies, including fliC sequence analysis, macrorestriction profiling of genomic DNA by pulsed-field gel electrophoresis (PFGE), random amplification of polymorphic DNA (RAPD), and multilocus sequence typing (MLST). The four approaches yielded consistent results overall but showed different resolution powers in establishing relatedness between isolates (PFGE > RAPD > MLST > fliC typing) and could usefully complement each other to address issues in the molecular epidemiology of P. aeruginosa strains producing acquired MBLs. In particular, the recently developed MLST approach was useful in revealing clonal relatedness between isolates when this was not readily apparent using RAPD and PFGE, and it suggested a common ancestry for some of the VIM-1-like MBL-positive P. aeruginosa strains currently spreading in Europe. The MBL producers belonged in three clonal complexes/burst groups (BGs). Of these, one corresponded to the previously described BG4 and included serotype O12 strains from Hungary and Sweden, while the other two were novel and included serotype O11 or nonserotypable strains from Greece, Sweden, and/or Italy. Comparison of the integrons carrying blaVIM-1-like cassettes of various isolates revealed a remarkable structural heterogeneity, suggesting the possibility that multiple independent events of acquisition of different blaVIM-containing integrons had occurred in members of the same clonal lineage, although a contribution of integrase-mediated cassette shuffling or other recombination mechanisms during the evolution of similar strains could also have played a role in determining this variability.

Giske, Christian G.; Libisch, Balazs; Colinon, Celine; Scoulica, Effie; Pagani, Laura; Fuzi, Miklos; Kronvall, Goran; Rossolini, Gian Maria

2006-01-01

209

Single wavelength silicon evanescent lasers  

Microsoft Academic Search

We review here recent work in the area of single wavelength silicon evanescent lasers that utilize distributed feedback, distributed Bragg reflector, and sampled grating distributed Bragg reflector laser topographies.

Alexander W. Fang; Brian R. Koch; Richard Jones; Erica Lively; John E. Bowers; Omri Raday; John E. Bowers

2009-01-01

210

Secure Communications at Millimeter Wavelengths.  

National Technical Information Service (NTIS)

The millimeter wavelength spectrum is being utilized more and more to fill specific communication needs to take advantage of the larger bandwidths available and the smaller antenna sizes required. Although the low atmospheric attenuation 'windows' in the ...

R. G. Murray

1971-01-01

211

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

PubMed

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

Hänzelmann, Petra; Schindelin, Hermann

2011-09-13

212

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

213

The distribution of CO2 over part of the surface of Iapetus revealed from statistical clustering of a VIMS mosaic.  

NASA Astrophysics Data System (ADS)

We present a detailed study of an Iapetus mosaic of Cassini-VIMS data with high spatial resolution (0.5 x 0.5°) [5]. We analyze this set of data using a statistical clustering approach to reduce the analysis of a large number of data (? 104 spectra from 0.35 to 5.10 ?m) to the study of seven representative groups accounting for 99.6 % of the surface covered by the original sample. We give special attention to the study of the CO2 band. We find that CO2 absorption is widespread over both the bright and dark regions of Iapetus' surface, and probably represents the trapping of carbon dioxide as a clathrate, hydrate, or adsorbate at the molecular level with other materials. The strength of the CO2 band in the areas where both, H2O- and carbon- bearing materials exist, gives support to the hypothesis that this volatile is formed on the surface of Iapetus as a product of irradiation of these two components.

Pinilla-Alonso, N.; Roush, T. L.; Marzo, G. A.; Cruikshank, D.; Dalle Ore, C. M.

2011-10-01

214

High-performance wavelength-locked diode lasers  

NASA Astrophysics Data System (ADS)

Rapidly maturing industrial laser applications are placing ever-tighter constraints on spectral width and wavelength emission stability over varying operating temperatures of high power diode laser pump sources. For example, improved power scaling and efficiency can be achieved by pumping the narrow upper laser level of Nd:YAG solid state lasers at 885 nm and the 1532-nm absorption band of Er:YAG solid state lasers, though taking full advantage of these configurations requires wavelength-locked pump sources. nLight offers a wide variety of wavelength-locked diode products based on external volume grating optics technology. It is often believed that the use of external gratings to wavelength lock diode lasers leads to an unavoidable loss in power and efficiency. nLight's design methodology is shown to eliminate the problem in our grating-locked diode laser products. These results are expected to enable improved performance in diode-pumped solid state and fiber laser systems.

Leisher, Paul; Price, Kirk; Karlsen, Scott; Balsley, David; Newman, Doug; Martinsen, Rob; Patterson, Steve

2009-02-01

215

Effects of wavelength routing and selection algorithms on wavelength conversion gain in WDM optical networks  

Microsoft Academic Search

Wavelength division multiplexing technology is emerging as the transmission and switch- ing mechanism for future optical mesh networks. In these networks, it is desired that a wavelength can be routed without electrical conversions. Two technologies are possible for this purpose: Wavelength Selective Cross-Connects (WSXC), and Wavelength Interchanging Cross-Connects (WIXC) which involve wavelength conversion. It is believed that wavelength converters may

Ezhan Karasan; Ender Ayanoglu

1998-01-01

216

Solid colloidal optical wavelength filter  

DOEpatents

The present invention relates generally to techniques and methods to filter optical wavelengths for spectroscopy, protection from intense radiation, monochromatizing, and analyzing optical radiation, and more particularly to a solid colloidal rejection filter and a method for constructing a solid colloidal rejection filter. A solid colloidal optical wavelength filter includes a suspension of spherical 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. 3 figs.

Alvarez, J.L.

1990-12-31

217

Solid colloidal optical wavelength filter  

DOEpatents

The present invention relates generally to techniques and methods to filter optical wavelengths for spectroscopy, protection from intense radiation, monochromatizing, and analyzing optical radiation, and more particularly to a solid colloidal rejection filter and a method for constructing a solid colloidal rejection filter. A solid colloidal optical wavelength filter includes a suspension of spherical 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. 3 figs.

Alvarez, J.L.

1990-01-01

218

On the wavelength of self-organized shoreline sand waves  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

219

Multi-wavelength applications of gravitational lensing  

NASA Astrophysics Data System (ADS)

Using an array of multi-wavelength data, we examine a variety of astrophysical problems with gravitational lensing. First, we seek to understand the mass distribution of an early-type galaxy with an analysis of the lens Q0957+561. We dissect the lens galaxy into luminous and dark components, and model the environment using results from weak lensing. Combining constraints from newly-discovered lensed images and stellar population models, we find the lens has a density profile which is shallower than isothermal, unlike those of typical early-type galaxies. Finally, using the measured time delay between the quasar images we find the Hubble constant to be H 0 = 79.3+6.7-8.5 km s-1 Mpc-1 . One intriguing application of lensing is to exploit the lens magnification boost to study high-redshift objects in greater detail than otherwise possible. Here, we analyze the mid-infrared properties of two lensed z ˜ 2 star-forming galaxies, SDSS J120602.09+514229.5 and SDSS J090122.37+181432.3, using Spitzer /IRS spectra to study their rest-frame ˜ 5-12 ?m emission. Both systems exhibit strong polycyclic aromatic hydrocarbon (PAH) features in the spectra, indicating strong star formation and the absence of significant AGN activity. For SDSS J090122.37+181432.3, this detection belies that inferred from optical measurements, indicating mid-IR spectroscopy provides key information needed to understand the properties of high-redshift star-forming galaxies. While lensing provides measurements of the macroscopic properties of lens systems, it can also shed light on small-scale structure of galaxies. To identify and understand lens substructure, we examine the multi-wavelength properties of flux ratios for six lenses. Variations of the flux ratios with wavelength can be used to study the lensed quasars and the small-scale mass distribution of lens galaxies. We detect strong multi-wavelength variations in the lenses HE 0435-1223 and SDSS 0806+2006. For HE 0435-1223, we study its substructure with a series of lens models which add clumps of mass near the lensed images. We detect the presence of a clump near image A, with a mass of log (MA

Fadely, Ross

2010-12-01

220

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

221

Compact integrated dynamic wavelength equalizer  

Microsoft Academic Search

An integrated dynamic wavelength equalizer that can control attenuation at 22 points across 35 nm of spectrum in a smooth manner is presented. It achieves low loss and compactness because it consists of a Michelson interferometer with a waveguide grating router in only one arm

C. R. Doerr; P. Schiffer; L. W. Stulz; M. Cappuzzo; E. Laskowski; A. Paunescu; L. Gomez; J. Gates

1999-01-01

222

40-wavelength add drop filter  

Microsoft Academic Search

We present in 40-wavelength, 100-GHz channel spacing, programmable, planar add-drop filter that has flattened passbands without excess loss. For TE polarized light, the insertion loss is 9-11 dB for the through channels, and the dropping extinction ratio is ⩾33 dB

C. R. Doerr; L. W. Stulz; M. Cappuzzo; E. Laskowski; A. Paunescu; L. Gomez; J. V. Gates; S. Shunk; A. E. White

1999-01-01

223

Wavelength shift in DCG holograms  

Microsoft Academic Search

It is known that for given recording and reconstruction geometries, the wavelength of light for which a volume reflection hologram recorded in the dichromated gelatin has the highest efficiency can be adjusted by suitable preparation, sensitization, exposure, and processing of the DCG layer. Unfortunately, reliable data on these factors is very limited; thus a detailed experimental study on the relations

Sylviane Lelievre; Romuald Pawluczyk

1991-01-01

224

Wavelength conversion technologies for WDM network applications  

Microsoft Academic Search

WDM networks make a very effective utilization of the fiber bandwidth and offer flexible interconnections based on wavelength routing. In high capacity, dynamic WDM networks, blocking due to wavelength contention can he reduced by wavelength conversion. Wavelength conversion addresses a number of key issues in WDM networks including transparency, interoperability, and network capacity. Strictly transparent networks offer seamless interconnections with

S. J. B. Yoo

1996-01-01

225

Long wavelength free electron lasers in 1994  

Microsoft Academic Search

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

H. P. Freund; V. L. Granatstein

1995-01-01

226

Multiple Wavelength Surface Emitting Semiconductor Laser Array  

Microsoft Academic Search

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

Fumio KOYAMA

227

vimA gene downstream of recA is involved in virulence modulation in Porphyromonas gingivalis W83.  

PubMed

A 0.9-kb open reading frame encoding a unique 32-kDa protein was identified downstream of the recA gene of Porphyromonas gingivalis. Reverse transcription-PCR and Northern blot analysis showed that both the recA gene and this open reading frame are part of the same transcriptional unit. This cloned fragment was insertionally inactivated using the ermF-ermAM antibiotic resistance cassette to create a defective mutant by allelic exchange. When plated on Brucella blood agar, the mutant strain, designated P. gingivalis FLL92, was non-black pigmented and showed significant reduction in beta-hemolysis compared with the parent strain, P. gingivalis W83. Arginine- and lysine-specific cysteine protease activities, which were mostly soluble, were approximately 90% lower than that of the parent strain. Expression of the rgpA, rgpB, and kgp protease genes was the same in P. gingivalis FLL92 as in the wild-type strain. In contrast to the parent strain, P. gingivalis FLL92 showed increased autoaggregration in addition to a significant reduction in hemagglutinating and hemolysin activities. In in vivo experiments using a mouse model, P. gingivalis FLL92 was dramatically less virulent than the parent strain. A molecular survey of this mutant and the parent strain using all known P. gingivalis insertion sequence elements as probes suggested that no intragenomic changes due to the movement of these elements have occurred in P. gingivalis FLL92. Taken together, these results suggest that the recA downstream gene, designated vimA (virulence-modulating gene), plays an important role in virulence modulation in P. gingivalis W83, possibly representing a novel posttranscriptional or translational regulation of virulence factors in P. gingivalis. PMID:11119521

Abaibou, H; Chen, Z; Olango, G J; Liu, Y; Edwards, J; Fletcher, H M

2001-01-01

228

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

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

229

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

230

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

231

Diagnosis of Bladder Cancer Recurrence Based on Urinary Levels of EOMES, HOXA9, POU4F2, TWIST1, VIM, and ZNF154 Hypermethylation  

PubMed Central

Background Non muscle invasive bladder cancer (NMIBC) has the highest recurrence rate of any malignancy and as many as 70% of patients experience relapse. Aberrant DNA methylation is present in all bladder tumors and can be detected in urine specimens. Previous studies have identified DNA methylation markers that showed significant diagnostic value. We evaluated the significance of the biomarkers for early detection of tumor recurrence in urine. Methodology/Principal Findings The methylation levels of EOMES, HOXA9, POU4F2, TWIST1, VIM, and ZNF154 in urine specimens were measured by real-time PCR (MethyLight). We analyzed 390 urine sediments from 184 patients diagnosed with NMIBC. Urine from 35 age-matched control individuals was used to determine the methylation baseline levels. Recurrence was diagnosed by cystoscopy and verified by histology. Initially, we compared urine from bladder cancer patients and healthy individuals and detected significant hypermethylation of all six markers (P<0.0001) achieving sensitivity in the range 82%–89% and specificity in the range 94%–100%. Following, we validated the urinary hypermethylation for use in recurrence surveillance and found sensitivities of 88–94% and specificities of 43–67%. EOMES, POU4F2, VIM and ZNF154 were more frequently methylated in urine from patients with higher grade tumors (P?0.08). Univariate Cox regression analysis showed that five markers were significantly associated with disease recurrence; HOXA9 (HR?=?7.8, P?=?0.006), POU4F2 (HR?=?8.5, P?=?0.001), TWIST1 (HR?=?12.0, P?=?0.015), VIM (HR?=?8.0, P?=?0.001), and ZNF154 (HR?=?13.9, P<0.001). Interestingly, for one group of patients (n?=?15) we found that hypermethylation was consistently present in the urine samples despite the lack of tumor recurrences, indicating the presence of a field defect. Conclusion/Significance Methylation levels of EOMES, HOXA9, POU4F2, TWIST1, VIM, and ZNF154 in urine specimens are promising diagnostic biomarkers for bladder cancer recurrence surveillance.

Reinert, Thomas; Borre, Michael; Christiansen, Anders; Hermann, Gregers G.; ?rntoft, Torben F.; Dyrskj?t, Lars

2012-01-01

232

Design and verification of wavelength routing function in WDM networks using wavelength transfer matrix approach  

Microsoft Academic Search

The wavelength transfer matrix is a powerful approach to designing and verifying the wavelength routing needed for complicated WDM networks1. This paper first describes the wavelength transfer matrix, its basic form and some extensions. A full-mesh WDM PON system that can directly connect ONUs and an OLT is proposed and analyzed in terms of wavelength by using the wavelength transfer

Kohei Okada; Kimio Oguchi

2005-01-01

233

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

SciTech Connect

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

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

1982-01-01

234

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

235

Multi-wavelength modeling of protoplanetary disks  

NASA Astrophysics Data System (ADS)

The on-going revolution of high angular resolution observations and increasing wavelength coverage promises to unlock tightly-kept secrets of circumstellar disks. Thanks to these advances, many issues have already been addressed : large scale geometry of disks, evidence of grain growth, of dust settling, ldots Most of these results are based on models that emphasize on fitting either SEDs or scattered light images or, more recently, interferometric visibilities. In this contribution, we present a global approach which aims at interpreting the increasing amount of observational data coherently, in the framework of a single model, in order to get a more global picture and to better characterize both the dust population and the disk properties. Results of such a modeling approach, applied to a few disks for which large observational data-sets are available, are presented.

Pinte, C.; Ménard, F.; Duchêne, G.; Augereau, J.-C.

2006-06-01

236

Alternative wavelengths for optically pumped alkali lasers  

NASA Astrophysics Data System (ADS)

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

Perram, Glen P.

2012-05-01

237

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

PubMed

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

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

2011-10-08

238

Short wavelength interferometer for ITER  

SciTech Connect

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

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

1992-04-01

239

Saturn’s Equatorial Plumes At Depth Observed By Cassini/VIMS and Radar: Some Ammonia-wet, Some Dry  

NASA Astrophysics Data System (ADS)

Large (> 3000 km), discrete clouds and ammonia vapor features buried under Saturn’s ubiquotous equatorial haze have been mapped contemporaneously in Cassini/VIMS 5-micron spectra and 2-cm raster-scan imagery by the Cassini/RADAR used in passive mode. Since 2008 these features have been clearly observed on four occasions - October 14-15, 2009, December 8-10, 2009, July 24-25, 2010, and March 19-21, 2011 - from a vantage point close to the knife-edge of the rings, which reduced the ring obscuration to just ± 3 degrees of latitude about the equator. Spectral modeling indicates that the cloud features are primarily located in the 2-3 bar region, and thus are likely to be comprised of ammonia hydrosulfide (NH4SH) with perhaps an admixture of water, but not of pure ammonia condensate. RADAR imagery reveals variations of the local ammonia humidity in the same 2-3 bar region, assuming constant temperatures at depth to within a few degrees. Observations acquired March 19-21, 2011 clearly show correlations of ammonia-humid air with NH4SH cloud features, consistent with the idea that NH4SH clouds form from updrafts of ammonia-humid air, akin to the formation of convective water clouds on Earth in regions of high humidity. However, observations acquired December 8-10, 2009 show the opposite behavior, with localized cloud features largely coinciding with regions of low ammonia humidity. One possible explanation is that in the case of weaker updrafts, the rising NH3 is significantly depleted as it creates the NH4SH clouds, leaving ammonia-depleted holes in the background ammonia vapor. Alternatively, the supply of H2S in updrafts may vary relative to NH3, thus regulating the formation of both NH4SH aerosols and the left-over NH3 vapor. Finally, clouds in ammonia-dry regions may just indicate mature clouds no longer undergoing formation, as observed in the downwind “comet tail” clouds of the major northern storm of 2010-2011.

Baines, Kevin H.; Momary, T. W.; Janssen, M. A.; Ingersoll, A. P.; Fletcher, L. N.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.; Sotin, C.

2012-10-01

240

Wavelength tunable alexandrite regenerative amplifier  

SciTech Connect

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

Harter, D.J.; Bado, P.

1988-11-01

241

Standard reference material 2036 near-infrared reflection wavelength standard.  

PubMed

Standard Reference Material 2036 (SRM 2036) is a certified transfer standard intended for the verification and calibration of the wavelength/wavenumber scale of near-infrared (NIR) spectrometers operating in diffuse or trans-reflectance mode. SRM 2036 Near-Infrared Wavelength/Wavenumber Reflection Standard is a combination of a rare earth oxide glass of a composition similar to that of SRM 2035 Near-Infrared Transmission Wavelength/Wavenumber Standard and SRM 2065 Ultraviolet-Visible-Near-Infrared Transmission Wavelength/Wavenumber Standard, but is in physical contact with a piece of sintered poly(tetrafluoroethylene) (PTFE). The combination of glass contacted with a nearly ideal diffusely reflecting backing provides reflection-absorption bands that range from 15% R to 40% R. SRM 2036 is certified for the 10% band fraction air wavelength centroid location, (10%)B, of seven bands spanning the spectral region from 975 nm to 1946 nm. It is also certified for the vacuum wavenumber (10%)B of the same seven bands in the spectral region from 10 300 cm(-1) to 5130 cm(-1) at 8 cm(-1) resolution. Informational values are provided for the locations of thirteen additional bands from 334 nm to 804 nm. PMID:15901335

Choquette, Steven J; Duewer, David L; Hanssen, Leonard M; Early, Edward A

2005-04-01

242

Wavelength-scale stationary-wave integrated Fouriertransform spectrometry  

Microsoft Academic Search

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

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

2007-01-01

243

Bolometric Arrays for Millimeter Wavelengths  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

244

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

Microsoft Academic Search

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

Alex M. H. Wong; George V. Eleftheriades

2011-01-01

245

Wavelength comparison study for bioaerosol detection  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

246

Single-wavelength STED microscope  

NASA Astrophysics Data System (ADS)

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

Baer, Stephen C.

2011-02-01

247

Effective wavelength calibration for moire fringe projection  

SciTech Connect

The fringe patterns seen when using moire instruments are similar to the patterns seen in traditional interferometry but differ in the spacing between consecutive fringes. In traditional interferometry, the spacing is constant and related to the wavelength of the source. In moire fringe projection, the spacing (the effective wavelength) may not be constant over the field of view and the spacing depends on the system geometry. In these cases, using a constant effective wavelength over the field of view causes inaccurate surface height measurements. We examine the calibration process of the moirefringe projection measurement, which takes this varying wavelength into account to produce a pixel-by-pixel wavelength map. The wavelength calibration procedure is to move the object in the out-of-plane direction a known distance until every pixel intensity value goes through at least one cycle. A sinusoidal function is then fit to the data to extract the effective wavelength pixel by pixel, yielding an effective wavelength map. A calibrated step height was used to validate the effective wavelength map with results within 1% of the nominal value of the step height. The error sources that contributed to the uncertainty in determining the height of the artifact are also investigated.

Purcell, Daryl; Davies, Angela; Farahi, Faramarz

2006-12-01

248

Galactic emission at decimeter wavelengths (Platania+, 2003)  

NASA Astrophysics Data System (ADS)

The diffuse galactic emission maps at decimeter wavelengths (408 MHz, Haslam et al., 1982A&AS...47....1H), (1420 MHz, Reich, 1982A&AS...48..219R, Reich & Reich 1986A&AS...63..205R), (2326 MHz, Jonas et al., 1998MNRAS.297..977J) have been destriped using the method proposed by Schlegel et al., 1998ApJ...500..525S. Statistical and systematic errors have been evaluated for each map. Each map is presented in two different pixelizations: ECP (Cartesian Projection) and HEALPix. In the case of HEALPix pixelization (in which the pixel area is constant), we omitted the (constant) error maps; the statistical and systematic errors for each map are summarized in the "Table 2" section below. Synchrotron spectral index and normalization factor have been evaluated using the three destriped surveys. Some of the results in this work have been derived using the HEALPix (Gorski et al., 1999, Proceedings of the MPA/ESO Conference on Evolution of Large-Scale Structure: from Recombination to Garching, ed. A.J. Banday, R.K. Sheth, & L. Da Costa, 37). (1 data file).

Platania, P.; Burigana, C.; Maino, D.; Caserini, E.; Bersanelli, M.; Cappellini, B.; Mennella, A.

2003-10-01

249

Finite parallel wavelengths and ionospheric structuring  

SciTech Connect

Much large-scale fluid structuring in the ionosphere has been attributed to the flutelike Rayleigh-Taylor and E x B gradient drift instabilities. The finite extent of the ionosphere and the spatial variation of plasma parameters within the ionosphere suggest that these instabilities can be expected to vary along magnetic field lines. The variations are taken into account by assuming a nonzero component of wave number parallel to the ambient magnetic field. The accompanying electric fields are not purely electrostatic but imply mode magnetic fields that may permit plasma transport across density gradients that are larger than classical cross-field diffusion. This enhanced diffusion, which is most effective for sufficiently large and tenuous plasma clouds, can limit the minimum size of striations to a larger value than classical considerations alone permit. Finite parallel wave number has the additional effect of allowing ion free energy to be transferred to parallel electron motion and so the Rayleigh-Taylor and E x B gradient drift instabilities can contribute to structuring at conjugate points along magnetic field lines where electron energy is deposited. Also, the transfer of free energy indicates that long-term structural persistence requires a continuous source of ion free energy. Some finite parallel wavelength effects, particularly those relating to transport, can be included in present two-dimensional striation simulations.

Sperling, J.L.

1983-05-01

250

Wavelength selective cross connect using arrayed waveguide lens multi-wavelength filters  

Microsoft Academic Search

We present an experimental demonstration of a partially equipped 128×128 OC-192 novel wavelength selective cross connect using a broadcast-and-select architecture. Novel silica multi-wavelength filters are key elements in the cross connect

C. R. Doerr; B. M. Mikkelsen; G. Raybon; P. Schiffer; W. Stulz; M. Zirngibl; G. Wilfong; M. Cappuzzo; E. Laskowski; A. Paunescu; L. Gomez; J. Gates

1999-01-01

251

Research with high-power short-wavelength lasers  

SciTech Connect

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

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

1985-03-05

252

Imaging Uranus at Submillimeter to Centimeter Wavelengths  

Microsoft Academic Search

We have been making regular observations of Uranus for the past several years, in part to search for variability associated with the 2007 equinox. We will present an analysis of our current data set, spanning wavelengths from 1 mm to 20 cm (using the SMA and VLA radio observatories), including our latest data collected in August of 2007. These wavelengths

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

2007-01-01

253

Tunable dispersion compensator with integrated wavelength locking  

Microsoft Academic Search

We demonstrate a compact and simple silica-waveguide 10-Gb\\/s dispersion compensator that works with uncontrolled wavelength transmitters by tracking the signal wavelength. 10.7-Gb\\/s transmissions over 5100ps\\/nm with duobinary and 3825ps\\/nm with unchirped NRZ are shown.

C. R. Doerr; S. Chandrasekhar; L. L. Buhl; M. A. Cappuzzo; E. Y. Chen; A. Wong-Foy; L. T. Gomez

2005-01-01

254

Sulfur dioxide absorption at DF laser wavelengths  

Microsoft Academic Search

The absorption of DF laser lines by sulfur dioxide under atmospheric conditions is measured in light of the possible application of optical methods to the detection of the atmospheric pollutant. Absorption measurements were performed for 20 DF laser wavelengths between 2792 and 2509 kaysers in a multipass absorption cell. Weak absorption is detected around a wavelength of 3.7 microns and

J. Altmann; P. Pokrowsky

1980-01-01

255

Long-Wavelength Astronomy on the Moon  

Microsoft Academic Search

There have been a variety of proposals for a long-wavelength radio astronomical telescope on the Moon since soon after the first human landings. We highlight two aspects of the Moon that make it particularly appealing for long-wavelength radio astronomy. 1. There are locations on the Moon that can be shielded completely from terrestrial emissions and at least partially from solar

J. Lazio; R. J. MacDowall; D. L. Jones; J. C. Kasper; K. Weiler; S. D. Bale; S. Neff

2006-01-01

256

Multiwavelength optical networks with limited wavelength conversion  

Microsoft Academic Search

This paper proposes optical wavelength division multiplexed (WDM) networks with limited wavelength conver- sion that can efficiently support lightpaths (connections) between nodes. Each lightpath follows a route in a network and must be assigned a channel on each link along the route. The load of a set of lightpaths is the maximum over all links of the number of lightpaths

Rajiv Ramaswami; Galen H. Sasaki

1998-01-01

257

Multiwavelength Optical Networks with Limited Wavelength Conversion  

Microsoft Academic Search

This paper proposes optical wavelength division multiplexed (WDM) networks withlimited wavelength conversion that can efficiently support lightpaths (connections) betweennodes. Each lightpath follows a route in the network and must be assigned achannel along each link in its route. The load max of a set of lightpath requests is themaximum over all links of the number of lightpaths that use the

Rajiv Ramaswami; Galen H. Sasaki

1997-01-01

258

Radar astronomy at millimeter and submillimeter wavelengths  

Microsoft Academic Search

The scant two-decade existence of radar astronomy has seen important contributions by this new technique to positional astronomy, to the metrics of the solar system, and to the study of lunar and planetary surfaces. The role of millimeter wavelengths in this new astronomy is discussed and the problems unique to these short wavelengths defined. Brief mention is made of the

J. W. Meyer

1966-01-01

259

GHRS Cycle 5 Echelle Wavelength Monitor  

NASA Astrophysics Data System (ADS)

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

Soderblom, David

1995-07-01

260

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

Microsoft Academic Search

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

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

2000-01-01

261

The Circular Polarization of Sagittarius A* at Submillimeter Wavelengths  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

262

THE CIRCULAR POLARIZATION OF SAGITTARIUS A* AT SUBMILLIMETER WAVELENGTHS  

SciTech Connect

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

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

2012-02-01

263

The Theory of Scale Relativity  

Microsoft Academic Search

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

Laurent Nottale

1992-01-01

264

[VIM-2 metallo-ß-lactamase gen detection in a class 1 integron associated to bla(CTX-M-2) in a Pseudomonas aeruginosa clinical isolate in Uruguay: first communication].  

PubMed

In order to analyze the presence of metallo-ß-lactamase in our country, we included in this study Pseudomonas aeruginosa isolates causing nosocomial infections in a hospital from Uruguay. The presence of a metallo-ß-lactamase VIM-2 in a class 1 integron and of an extended spectrum -lactamase CTX-M-2 was detected in one isolate. This is the first report of both genes, bla(CTX-M-2) and bla(VIM-2),in the same P. aeruginosa isolate. Although carbapenemases have been extensively documented in the world, this is the first report of an acquired metallo-ß-lactamase with carbapenemase activity in pathogenic bacteria in Uruguay. PMID:22430993

Ingold, Ana J; Castro, Mercedes; Nabón, Adriana; Borthagaray, Graciela; Márquez, Carolina

265

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

PubMed

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

De Bièvre, Paul

2009-03-01

266

Wavelengths effective in induction of malignant melanoma  

SciTech Connect

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

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

1993-07-15

267

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

268

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

SciTech Connect

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

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

2011-04-15

269

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

270

The Galactic Center at Different Wavelengths  

NSDL National Science Digital Library

This page from then UCLA Galactic Center Group provides images of the galactic center over most of the electromagnetic spectrum. Each image has explanatory text, and a background section explains the value of observing the galactic center at various wavelengths.

2007-06-22

271

An Integrated Wavelength-Sensitive Polarimeter  

Microsoft Academic Search

An integrated, wavelength-dependent polarimeter for measuring the PMD distortion on a data-loaded signal is proposed. Results are presented using a tunable, narrowband filter with a FWHM=2 GHz realized in 4% index contrast waveguides

C. K. Madsen; E. J. Laskowski; J. Bailey; E. Chen; A. Griffin; M. A. Cappuzzo; L. Gomez; R. Long; L. Stulz; A. Wong-Foy

2002-01-01

272

Polymeric wavelength filters with polymer gratings  

NASA Astrophysics Data System (ADS)

Wavelength filters with Bragg gratings are demonstrated based on low-loss polymer waveguides and high-refractive-index polymer gratings. Two kinds of fluorinated polymers, perfluorocyclobutane and fluorinated poly(arylene ethers) are used for the low-loss waveguide operating around the 1.55 ?m wavelength. The polymer grating is made of Resole, and it is successfully integrated in the polymer waveguides. In order to fabricate the Bragg gratings on the polymer waveguides, we use a phase mask and a Hg lamp in a mask aligner as the illuminating source instead of the laser. This method provides uniform gratings on a large area as well as the alignment capability. In the fabricated wavelength filters, the reflectivity at the Bragg wavelength is 30 dB, the 3 dB bandwidth is as narrow as 0.6 nm, and the insertion loss is 3.7 dB.

Oh, Min-Cheol; Lee, Myung-Hyun; Ahn, Joo-Heon; Lee, Hyung-Jong; Han, Seon Gyu

1998-03-01

273

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

274

Wavelength-agile optical access networking system  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

275

Undulators for short wavelength FEL amplifiers.  

National Technical Information Service (NTIS)

Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength ...

R. D. Schlueter

1994-01-01

276

Short wavelength regenerative amplifier free electron lasers  

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

277

An automatic 40-wavelength channelized equalizer  

Microsoft Academic Search

We demonstrate a wavelength equalizer in planar silica waveguides that can automatically control individual channel powers in a 40-channel 100-GHz-channel-spacing wavelength-division multiplexed system, yet gives no distortion to channels that already have the same power as their neighbors. It has <6.8 dB insertion loss over 32-nm, 9-13-dB attenuation range, and <0.18 dB polarization\\/time-dependent loss

C. R. Doerr; L. W. Stulz; R. Pafchek; L. Gomez; M. Cappuzzo; A. Paunescu; E. Laskowski; L. Buhl; H. K. Kim; S. Chandrasekhar

2000-01-01

278

Rossby wave equation for long wavelength  

NASA Astrophysics Data System (ADS)

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

Orito, Kohtaro; Sato, Masatomo; Irie, Haruyuki

1995-06-01

279

Highly sensitive detector for submillimeter wavelength range  

NASA Astrophysics Data System (ADS)

A highly sensitive detector of submillimeter wavelength radiation is reported. The detector consists of a semiconductor quantum dot (QD) and a metallic single-electron transistor (SET). The SET detects change in the potential distribution induced by photon absorption within the QD. We have fabricated and studied this detector at wavelengths longer than 200 ?m. High sensitivity, ~10-20 W/Hz in terms of noise equivalent power, is found. Further optimization of the detector design is suggested.

Hashiba, H.; Antonov, V.; Kulik, L.; Komiyama, S.; Stanley, C.

2004-12-01

280

Monolithic multiband wavelength router for fast reconfigurable data networking  

Microsoft Academic Search

A compact and highly scaleable reconfigurable wavelength router is proposed and demonstrated using an electronically-gated cyclic wavelength router. Power penalties for wavelength multiplexed 3x10Gb\\/s wavelength channels of order 0.2dB are achieved. Keywords: Integrated optoelectronics, Photonic switching systems; Wavelength division multiplexing

A. Rohit; K. A. Williams; X. J. M. Leijtens; T. de Vries; Y. S. Oei; M. J. R. Heck; L. M. Augustin; R. Notzel; D. J. Robbins; M. K. Smit

2010-01-01

281

The fabrication of millimeter-wavelength accelerating structures  

SciTech Connect

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

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

1996-11-01

282

Wavelength selection of fingering instability inside Hele-Shaw cell  

NASA Astrophysics Data System (ADS)

Fingering instabilities between fluids confined between two plates sometimes involve a typical wavelength ? proportional to the gap h. This unexplained behavior is investigated in the case of the Rayleigh-Taylor instability between two liquids of same viscosity. Using linear stability analysis based on a simplified model of hydrodynamics (Darcy-Stokes equation), we show in particular that, in the miscible case, the wavelength ? of the instability normalized by the gap b of the cell and the dimensionless growth rate ? remain constant when the Péclet number Pe = fracb^3 ??12? D is large ( ? viscosity, g gravitational acceleration, D diffusivity, ?? density difference). The same result holds in the immiscible case for large capillary number C_a=fracb^2??12? (? surface tension). In this saturation regime, the dominant wavelength is given by ?=2.3b, while in the opposite limit (low Pe or low C_a) ? scales respectively as fracbPe or fracbC_a^1/2. These theoretical solutions are then compared to experimental measurements for a wide range of Peclet numbers (more than 4 orders of magnitude) : a very good agreement is observed in particular for viscous fluids.

Kurowski, Pascal; Limat, Laurent; Petitjeans, Philippe; Fernandez, Juan

2001-11-01

283

Novel wavelength-matching scheme for wavelength routers without any reference sources  

NASA Astrophysics Data System (ADS)

In this paper, we propose and demonstrate a novel and effective wavelength-matching scheme for wavelength grating routers to match their transmission peaks to the wavelength assignment of the data channels without any reference sources. The unused portion of the amplified spontaneous emission (ASE) power of the Erbium doped fiber amplifiers is utilized as the monitoring light source and fiber Bragg gratings of a particular center reflection wavelength is used as the wavelength reference. The scheme supports in- service monitoring and will not degrade the performance of the data channels. It is also insensitive to dynamic ASE power variations arising form channel ad-drop. We have experimentally demonstrated the proposed wavelength-matching scheme for WGR and analyzed the scheme numerically for design optimization.

Chan, Chun Kit; Kong, T. P.; Tong, Franklin K.; Chen, Lian-Kuan

1998-07-01

284

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

PubMed Central

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

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

2011-01-01

285

Optical lithography at a 126-nm wavelength  

NASA Astrophysics Data System (ADS)

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

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

2001-08-01

286

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

NASA Astrophysics Data System (ADS)

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

Poberezhskiy, Ilya Y.; Fetterman, Harold R.

2002-03-01

287

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

PubMed

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

Poberezhskiy, Ilya Y; Fetterman, Harold R

2002-03-15

288

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

NASA Astrophysics Data System (ADS)

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

Zheng, Sheng; Tian, Jinwen; Liu, Jian

2005-04-01

289

Wavelength selection of fingering instability inside Hele-Shaw cells  

NASA Astrophysics Data System (ADS)

Fingering instabilities involving fluids confined between two plates sometimes give rise to a typical wavelength ? proportional to the gap h. This unexplained behavior is investigated for the case of the Rayleigh-Taylor instability between two liquids of the same viscosity. Using qualitative scaling arguments and linear stability analysis for a simplified model of hydrodynamics, we show that, in the miscible case, h becomes a natural cut-off when diffusion is negligible, i.e., when the Péclet number Pe=h3??g/(?D) is large (? viscosity, g gravitational acceleration, D diffusivity, ?? density difference). The same result holds in the immiscible case for large capillary number Ca=h2??g/(12?) (? surface tension). In this saturation regime, the dominant wavelength is given by ?~2.3h, while in the opposite limit (low Pe or low Ca) ? scales, respectively, as h/Pe or h/Ca1/2. These results are in agreement with a recent experimental study.

Fernandez, J.; Kurowski, P.; Limat, L.; Petitjeans, P.

2001-11-01

290

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

291

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

292

Sparse Regeneration in Translucent Wavelength-Routed Optical Networks: Architecture, Network Design and Wavelength Routing  

Microsoft Academic Search

In this paper we study an alternate network architecture, called translucent network, to the fully transparent and fully opaque network architectures. In a translucent wavelength-routed optical network, a technique called sparse regeneration is used to overcome the severe lightpath blocking due to signal quality degradation and wavelength contention in a fully transparent network while using much less regenerators than in

Xi Yang; Byrav Ramamurthy

2005-01-01

293

980-nm pump-band wavelengths for long-wavelength-band erbium-doped fiber amplifiers  

Microsoft Academic Search

The impact of pump wavelength and input signal power on the output signal and backward spontaneous emission noise power of L-band erbium-doped fiber amplifiers is examined. It is shown experimentally that tuning the pump wavelength ±30-nm away from the 980-nm absorption peak provides 3-5-dB improvement in pump-to-signal conversion

F. A. Flood; C. C. Wang

1999-01-01

294

Wavelength-tunable microbolometers with metamaterial absorbers.  

PubMed

Microbolometers are modified by metallic resonant absorber elements, leading to an enhanced responsivity at selectable wavelengths. The dissipative energy absorption of tailored metamaterials allows for engineering the response of conventional bolometer microbridges. The absorption peak position and height are determined by the geometry of the metamaterial. Square-shaped metal/dielectric/metal stacks as absorber elements show spectral resonances at wavelengths between 4.8 and 7.0 microm in accordance with numerical simulations. Total peak absorptions of 0.8 are obtained. The metamaterial modified bolometers are suitable for multispectral thermal imaging systems in the mid-IR and terahertz regime. PMID:19794799

Maier, Thomas; Brückl, Hubert

2009-10-01

295

Multi-Wavelength Observations of Pulsars  

NASA Astrophysics Data System (ADS)

Almost 30 Isolated Neutron Stars (INSs) of different flavours have been identified at optical, ultraviolet, or infrared (UVOIR) wavelengths. Here, I present a short review of the historical background and describe the scientific impact of INS observations in the UVOIR. Then, I focus on UVOIR observations of rotation-powered pulsars, so far the most numerous class of INSs identified at these wavelengths, and their observational properties. Finally, I present the results of new UVOIR observations and an update of the follow-ups of ?-ray pulsars detected by Fermi.

Mignani, R. P.

2012-12-01

296

Observe an exploded star at different wavelengths  

NSDL National Science Digital Library

This Earth science resource enables students to observe and compare the appearance of the Crab Nebula under different wavelengths. The introduction explains how the nebula is the remains of an exploded star (supernova). It also reveals how temperature variations in the nebula are detected by different wavelengths. Students are instructed to move the cursor across the spectrum to see images of the nebula captured using radio and microwaves; infrared, visible, and ultraviolet light; and gamma rays. Each image is labeled with the appropriate portion of the electromagnetic spectrum. Copyright 2005 Eisenhower National Clearinghouse

Education, Terc. C.; Littell, Mcdougal

2003-01-01

297

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

SciTech Connect

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

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

2010-03-15

298

Multilayer mirrors for XUV Ge laser wavelengths  

Microsoft Academic Search

Mo\\/Si multilayer mirrors with a high reflectance at normal incidence in the 232 - 236 angstrom spectral region have been deposited by rf magnetron sputtering for use in a XUV Ge-laser. The mirrors had a peak reflectance of 26% in this wavelength region. Characterization by TEM and XRD indicates good thickness control in the deposition process and low interface roughness,

Claude Montcalm; Brian T. Sullivan; Henri Pepin; Jerzy A. Dobrowolski; G. D. Enright

1992-01-01

299

A wavelength multiplexed fiber optic hydrogen sensor  

NASA Astrophysics Data System (ADS)

We present a novel configuration of a fiber-optic hydrogen sensor suitable for wavelength multiplexing. It is based on a palladium-coated tapered fiber and a fiber Bragg grating. This scheme allows sensor's multiplexing, which increases the capability to implement multipoint sensor networks for volumetric detection. Moreover, the sensitivity of the sensor is enhanced since light interacts twice with the palladium layer.

Zalvidea, Dobryna; Diez, Antonio; Cruz Munoz, Jose Luis; Andres, Miguel V.

2004-10-01

300

A wavelength multiplexed fiber optic hydrogen sensor  

Microsoft Academic Search

We present a novel configuration of a fiber-optic hydrogen sensor suitable for wavelength multiplexing. It is based on a palladium-coated tapered fiber and a fiber Bragg grating. This scheme allows sensor's multiplexing, which increases the capability to implement multipoint sensor networks for volumetric detection. Moreover, the sensitivity of the sensor is enhanced since light interacts twice with the palladium layer.

Dobryna Zalvidea; Antonio Diez; Jose Luis Cruz Munoz; Miguel V. Andres

2004-01-01

301

Monolithic Multiband Nanosecond Programmable Wavelength Router  

Microsoft Academic Search

A compact scalable reconfigurable multiwavelength router is proposed and demonstrated using an electronically gated cyclic router. Simultaneous wavelength-multiplexed channel allocation is performed with power penalties of 0.2-0.8 dB. Nanosecond timescale reconfiguration is achieved within a 2-ns guard band using semiconductor optical amplifier gates.

A. Rohit; K. A. Williams; X. J. M. Leijtens; T. de Vries; Y. S. Oei; M. J. R. Heck; L. M. Augustin; R. Notzel; D. J. Robbins; M. K. Smit

2010-01-01

302

Multi-wavelength heterodyne holography and interferometry  

NASA Astrophysics Data System (ADS)

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

Yatagai, Toyohiko

2013-09-01

303

Wavelength-sensitive-function controlled reflectance reconstruction.  

PubMed

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

Tian, Jiandong; Tang, Yandong

2013-08-01

304

Wavelength Tunable Light Emitting Nanostructures and Devices  

Microsoft Academic Search

In this paper, we report our recent progress in wavelength tunable organic light emitting diodes (OLEDs) and nanostructures. For OLEDs, a considerable color tunability by changing the applied voltage is demonstrated and the mechanisms of the tunability are discussed. For the nanostructures, the tunable emission of ZnSe nanobelts by modifying the operation temperature is reported. The origins of the emission

W. C. H. Choy; C. J. Liang; Y. P. Leung

2006-01-01

305

Wavelength ratiometric fluorescent probes for glucose  

NASA Astrophysics Data System (ADS)

We have developed a new series of glucose sensitive fluorophores that display shifts in emission wavelengths upon the binding of glucose. Complexation of glucose with the boronic acid moiety changes both its orbital hybridization and its ability to accept and donate electrons. This change results in distinct emission spectra for the fluorophores when free in solution or complexed with glucose.

DiCesare, Nicholas; Lakowicz, Joseph R.

2002-06-01

306

Wavelength compensation by time reverse ray tracing  

Microsoft Academic Search

We specified 406 mm diameter off axis powered HOEs to operate at 1.06 microns and for trials at 670 nm, then looked for ways to construct them at 488 nm. We were able to write holographic surfaces directly in Zemax, then play back other wavelengths through them to display the aberrations that needed to be canceled. Zemax had easy entry

Richard D. Rallison; Scott R. Schicker

1995-01-01

307

The Two-Wavelength Method of Microspectrophotometry  

PubMed Central

The two-wavelength method of microspectrophotometry corrects for distributional error and measures the amount of absorbing material by taking advantage of certain spectral characteristics of the specimen. Under certain circumstances, such as the absorption of nucleic acids in the ultraviolet and of black or multiple stains in the visible, the spectral characteristics are not suitable for the application of the method. To circumvent this, a photomicrograph of the object is taken with monochromatic light of a suitable wavelength. A second plate is exposed as a contact print of the photomicrograph and is developed in the presence of a coupling agent. After bleaching and fixation, the positive appears as a monochromatic color transparency. Two-wavelength analysis of such a transparency can be made in terms of the new color. The measurements will be free of distributional error and can be equated to the original object. The necessary formulae are derived, and a method which has proven suitable for color development is given. The photographic and the direct two-wavelength method were found to give equivalent results when both were used on the same series of liver nuclei. The application of the photographic method to ultraviolet absorption has been demonstrated. The new method is potentially applicable to other types of photographic densitometry involving heterogeneous images.

Mendelsohn, Mortimer L.

1958-01-01

308

Cutoff Wavelengths of Elliptical Metallic Waveguides  

Microsoft Academic Search

The cutoff wavelengths lambdacmn of elliptical metallic waveguides with perfectly conducting walls are determined analytically. Two different methods are used for the evaluation. In the first, the electromagnetic field is expressed in terms of elliptical-cylindrical wave functions. In the second, a shape perturbation method, the field is expressed in terms of circular-cylindrical wave functions only, while the equation of the

Georgios D. Tsogkas; John A. Roumeliotis; Stylianos P. Savaidis

2009-01-01

309

Wavelengths effective in induction of malignant melanoma  

Microsoft Academic Search

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

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

1993-01-01

310

Modular wavelength selective cross-connects  

Microsoft Academic Search

Optical cross-connects are an enabling technology for transparent mesh networking, but are better implemented in modular fashion for economic benefits. Various cross-connect constructs are reviewed and found that using wavelength-selective switches offers the greatest advantages.

D. Marom

2004-01-01

311

Wavelength shifting and bandwidth broadening in DCG  

Microsoft Academic Search

Experimental results are described concerning the influence of processing parameters on the spectral selectivity of reflection holograms recorded in dichromated gelatin. The aim of this investigation was to produce holographic gratings with well-defined filter properties and to shift the central wavelength toward the red spectral region and to broaden their bandwidth.

Dorina Corlatan; Martin Schaefer; Gerhard Anders

1991-01-01

312

Two-wavelength spatial-heterodyne holography  

DOEpatents

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

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

2007-12-25

313

Radar Astronomy at Millimeter and Submillimeter Wavelengths.  

National Technical Information Service (NTIS)

The scant two-decade existence of radar astronomy has seen important contributions by this new technique to positional astronomy, to the metrics of the solar system, and to the study of lunar and planetary surfaces. The role of millimeter wavelengths in t...

J. W. Meyer

1965-01-01

314

Visible to Gamma-Ray Wavelength Ratio.  

National Technical Information Service (NTIS)

The authors report on procedures and a preliminary result for a measurement of the wavelength of the 198Au 412 KeV line relative to that of a molecularly stabilized laser in the visible. The measurement involves: optical interferometry of a Si lattice rep...

R. D. Deslattes E. G. Kessler W. C. Sauder A. Henins

1976-01-01

315

Wavelength Conversion in Shortest-Path All-Optical Networks  

Microsoft Academic Search

We consider all-optical networks with shortest-path routing that use wavelength- division multiplexing and employ wavelength conversion at specic nodes in order to maximize their capacity usage. We present ecien t algorithms for deciding whether a placement of wavelength converters allows the network to run at maximum capacity, and for nding an optimal wavelength assignment when such a placement of con-

Thomas Erlebach; Stamatis Stefanakos

2003-01-01

316

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

NASA Astrophysics Data System (ADS)

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

Lively, Erica

317

Behavior of 2D Turbulence Spectra at Long Wavelengths in Relation to Perpendicular Particle Transport  

Microsoft Academic Search

Much past work on perpendicular particle transport in 2D magnetic turbulence has employed a model 2D spectrum with somewhat pathological characteristics such as an infinite correlation scale. Here we consider how the behavior of the spectrum at long wavelengths influences the perpendicular diffusion coefficient, by using spectrum models ranging from the somewhat pathological one commonly used in the past, to

J. W. Bieber; W. H. Matthaeus

2009-01-01

318

Wavelength dependence of the light scattered from a dielectric film deposited on a metal substrate  

Microsoft Academic Search

We consider a scattering system consisting of a dielectric film deposited on a semi-infinite metal, and focus on the wavelength dependence of the total integrated scattering and angle resolved scattering from such a system. In particular we study theoretically by a large scale rigorous numerical simulation approach the reflectivity, R((lambda) ), as well as the total scattered energy, U((lambda) ),

Ingve Simonsen; Tamara A. Leskova; Alexei A. Maradudin; Ola D. Hunderi

2000-01-01

319

Saturation gain-length product during short-wavelength plasma lasing  

NASA Astrophysics Data System (ADS)

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

Bleiner, Davide

2012-08-01

320

Spectral sensitivity and wavelength discrimination of the human peripheral visual field.  

PubMed

Spectral sensitivity and wavelength discrimination are determined along the nasal horizontal meridian of the human peripheral retina. The target size as a function of eccentricity is varied according to a particular cortical magnification factor. Spectral sensitivity is measured by flicker photometry parameterized for the flicker frequency (10-20 Hz) and is found to be independent of the eccentricity (0-80 degrees) for 20-Hz flicker photometry after correction of the foveal spectral sensitivity for macular pigment absorption. This 20-Hz function is chosen as being representative for the peripheral luminous-efficiency function and is used in the wavelength-discrimination experiments. The peripheral retina can perform wavelength discrimination up to an eccentricity of 80 degrees. If field-size scaling according to the eccentricity-dependent cone density, the cortical magnification factor, or the reciprocal of the interganglion cell distance is applied, then wavelength-discrimination performance from 8 degrees to 80 degrees eccentricity is roughly the same. Foveal wavelength discrimination is considerably better than peripheral wavelength discrimination. PMID:6726492

van Esch, J A; Koldenhof, E E; van Doorn, A J; Koenderink, J J

1984-05-01

321

Breakdown of the Debye approximation for the acoustic modes with nanometric wavelengths in glasses  

PubMed Central

On the macroscopic scale, the wavelengths of sound waves in glasses are large enough that the details of the disordered microscopic structure are usually irrelevant, and the medium can be considered as a continuum. On decreasing the wavelength this approximation must of course fail at one point. We show here that this takes place unexpectedly on the mesoscopic scale characteristic of the medium range order of glasses, where it still works well for the corresponding crystalline phases. Specifically, we find that the acoustic excitations with nanometric wavelengths show the clear signature of being strongly scattered, indicating the existence of a cross-over between well-defined acoustic modes for larger wavelengths and ill-defined ones for smaller wavelengths. This cross-over region is accompanied by a softening of the sound velocity that quantitatively accounts for the excess observed in the vibrational density of states of glasses over the Debye level at energies of a few milli-electronvolts. These findings thus highlight the acoustic contribution to the well-known universal low-temperature anomalies found in the specific heat of glasses.

Monaco, Giulio; Giordano, Valentina M.

2009-01-01

322

Multi-wavelength fluorometry for anaerobic digestion process monitoring.  

PubMed

Applicability of multi-wavelength fluorometry for anaerobic digestion process monitoring was investigated in a 3.5 L upflow anaerobic sludge bed (UASB) lab-scale reactor. Both off-line and on-line monitoring of key process parameters was tested. Off-line emission spectra were measured at an angle of 90 degrees to the excitation beam using a cuvette. On-line measurements were carried out using a fiber optic probe in the external recirculation line of the digester. Fluorescence spectra were correlated to available analytical measurements to obtain partial least square regression models. An independent set of measurements was used to validate the regression models. Model estimations showed reasonable agreement with analytical measurements with multiple determination coefficients (R2) between 0.6 and 0.95. Results showed that offline fluorescence measurements can be used for fast estimation of anaerobic digestor effluent quality. At the same time, the on-line implementation of multi-wavelength fluorescence measurements can be used for realtime process monitoring and, potentially, for on-line process control. PMID:16180465

Morel, E; Santamaria, K; Perrier, M; Guiot, S R; Tartakovsky, B

2005-01-01

323

Wavelength dependence of reflectometric cone photoreceptor directionality  

NASA Astrophysics Data System (ADS)

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

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

2003-01-01

324

The Long Wavelength Array Software Library  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

325

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

326

Automatic wavelength channel-by-channel equalizer  

Microsoft Academic Search

We demonstrate a wavelength equalizer that can automatically control individual channel powers in a 40 channel system, yet gives no distortion to channels that already have the same power as their neighbors. It has <6.8 dB insertion loss over 32 nm, 9-13 dB attenuation range, and <0.18 dB polarization\\/time-dependent loss

C. R. Doerr; L. W. Stulz; R. Pafchek; L. Gomez; M. Cappuzzo; A. Paunescu; E. Laskowski; L. Buhl; H. K. Kim; S. Chandrasekhar

2000-01-01

327

Source of coherent short wavelength radiation  

DOEpatents

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

Villa, Francesco (Alameda, CA)

1990-01-01

328

Tune-out wavelengths for potassium  

NASA Astrophysics Data System (ADS)

The five longest tune-out wavelengths for the potassium atom are determined using a relativistic structure model which treats the atom as consisting of a single valence electron moving outside a closed shell core. The importance of various terms in the dynamic polarizability in the vicinity of the 4pJ, 5pJ, and 6pJ transitions are discussed.

Jiang, Jun; Tang, Li-Yan; Mitroy, J.

2013-03-01

329

Examine the sun at different wavelengths  

NSDL National Science Digital Library

This Earth science resource enables students to observe and compare the sun's appearance under different types of electromagnetic radiation. Students are instructed to move the cursor across the spectrum to see images of the sun under radio and microwaves; infrared, visible, and ultraviolet light; and gamma rays. Each image includes a label that indicates the portion of the electromagnetic spectrum, the wavelength in angstroms and meters, and the layer of the sun in view. Copyright 2005 Eisenhower National Clearinghouse

Education, Terc. C.; Littell, Mcdougal

2003-01-01

330

Optical Detection in Ultrafast Short Wavelength Science  

SciTech Connect

A new approach to coherent detection of ionising radiation is briefly motivated and recounted. The approach involves optical scattering of coherent light fields by colour centres in transparent solids. It has significant potential for diffractive imaging applications that require high detection dynamic range from pulsed high brilliance short wavelength sources. It also motivates new incarnations of Bragg's X-ray microscope for pump-probe studies of ultrafast molecular structure-dynamics.

Fullagar, Wilfred K.; Hall, Chris J. [School of Physics, Monash University, Victoria 3800 (Australia); Monash Centre for Synchrotron Science, Monash University, Victoria 3800 (Australia); Centre of Excellence for Coherent X-ray Science, School of Physics, University of Melbourne, Victoria, 3010 (Australia)

2010-06-23

331

Wavelengths and energy levels of Fe VIII  

NASA Astrophysics Data System (ADS)

The Fe VIII (Fe7+) spectrum has been investigated in the 35-200 nm wavelength region. The radiation emission following slow ion-atom collisions has been observed for the collision system Fe8+ + T (T He or Ar) at the Fe8+ energy 80keV. Twelve new transitions from different excited states in Fe VIII were identified. New energy levels of Fe VIII have been established from the transitions. The analysis was supported by Hartree-Fock calculations.

Wang, M.; Arnesen, A.; Dunne, P.; Hallin, R.; Heijkenskjöld, F.; O'Reilly, F.

1997-01-01

332

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

333

Long Wavelength Ripples in the Nearshore  

NASA Astrophysics Data System (ADS)

Sediment bedforms are ubiquitous in the nearshore environment, and their characteristics and evolution have a direct effect on the hydrodynamics and the rate of sediment transport. The focus of this study is long wavelength ripples (LWR) observed at two locations in the nearshore at roughly 3m water depth under combined current and wave conditions in Duck, North Carolina. LWR are straight-crested bedforms with wavelengths in the range of 20-200cm, and steepness of about 0.1. They occur in the build up and decay of storms, in a broader range of values of the flow parameters compared to other ripple types. The main goal of the study is to test the maximum gross bedform-normal transport (mGBNT) hypothesis, which states that the orientation of ripples in directionally varying flows is such that the gross sediment transport normal to the ripple crest is maximized. Ripple wavelengths and orientation are measured from rotary fanbeam images and current and wave conditions are obtained from electromagnetic (EM) flowmeters and an offshore pressure gauge array. Preliminary tests in which transport direction is estimated from the combined flow velocity vectors indicate that the mGBNT is not a good predictor of LWR orientation. Results from tests of the mGBNT hypothesis using a sediment transport model will be presented.

Alcinov, T.; Hay, A. E.

2008-12-01

334

Acoustic dynamics of network-forming glasses at mesoscopic wavelengths.  

PubMed

The lack of long-range structural order in amorphous solids induces well known thermodynamic anomalies, which are the manifestation of distinct peculiarities in the vibrational spectrum. Although the impact of such anomalies vanishes in the long wavelength, elastic continuum limit, it dominates at length scales comparable to interatomic distances, implying an intermediate transition regime still poorly understood. Here we report a study of such mesoscopic domains by means of a broadband version of picosecond photo-acoustics, developed to coherently generate and detect hypersonic sound waves in the sub-THz region with unprecedented sampling efficiency. We identify a temperature-dependent fractal v(3/2) frequency behaviour of the sound attenuation, pointing to the presence of marginally stable regions and a transition between the two above mentioned limits. The essential features of this behaviour are captured by a theoretical approach based on random spatial variation of the shear modulus, including anharmonic interactions. PMID:23653205

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

2013-01-01

335

Acoustic dynamics of network-forming glasses at mesoscopic wavelengths  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

336

Sub-Wavelength Optical Fluorescence Microscopy for Biological Applications  

NASA Astrophysics Data System (ADS)

Visualization of sub-cellular structures and their temporal evolution contributes substantially to our understanding of biological processes. Far-field optical microscopy is arguably the most powerful imaging technique for cells and tissues because it allows live specimens to be studied over extended periods of time with only minimal perturbation due to the measurement. In fluorescence microscopy, biomolecules or supramolecular structures of interest are specifically labeled by light-emitting moieties and thus can be imaged with excellent contrast. A disadvantage of standard optical microscopy is its moderate spatial resolution, which is restricted to about half the wavelength of visible light (˜200 nm) by fundamental physical laws governing wave optics. Consequently, molecular interactions occurring on spatial scales of 1-100 nm cannot be resolved. However, a variety of super-resolution fluorescence microscopy techniques have recently been developed that overcome the resolution limitation. Here we present a brief overview of these techniques and their application to cellular biophysics.

Hedde, P. N.; Nienhaus, Gerd Ulrich

337

On the gyrokinetic model in long wavelength regime  

NASA Astrophysics Data System (ADS)

The gyrokinetic quasi-neutrality equation is considered from the point of view of the push-forward representation of particle density associated with the guiding-center transformation and the gyro-center transformation involved in the standard gyrokinetic formulation. It is clearly shown that the higher order displacement vector of the guiding-center transformation as well as the gyro-center displacement vector should be taken into account in the long wavelength regime. The higher order displacement vector of the guiding-center transformation yields additional higher order terms related to nonuniformity of magnetic field in the gyrokinetic quasi-neutrality equation. These additional terms may be important when the gradient scale length of electric field can be comparable to that of the magnetic field as in low aspect ratio tokamaks. Also the gyrokinetic Hamiltonian should be modified for consistency.

Miyato, N.; Scott, B. D.; Yagi, M.

2013-07-01

338

Laser damage testing of coated reflectors at excimer laser wavelengths  

SciTech Connect

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

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

1981-01-01

339

A Simple Orthomode Transducer for Centimeter to Submillimeter Wavelengths  

NASA Astrophysics Data System (ADS)

We describe a simple orthomode transducer suitable for operation from centimeter to submillimeter wavelengths with appropriate scaling. It is fabricated as a split-block assembly with all waveguides in the same plane, and requires no septum or polarizing wires. The OMT operates over a 1.3:1 frequency band, narrower than a full waveguide band (typically 1.5:1). For a WR-10 version of the OMT, covering 78-102 GHz, the polarization isolation is > 37 dB and the return loss at the rectangular waveguide ports > 24 dB. The practical upper frequency for this design is probably limited by the precision of alignment that can be achieved between the block halves, which affects the polarization isolation.

Dunning, A.; Srikanth, S.; Kerr, A. R.

2009-04-01

340

Lowering plasma frequency by enhancing the effective mass of electrons: A route to deep sub-wavelength metamaterials  

NASA Astrophysics Data System (ADS)

Deep sub-wavelength metamaterials are the key to the further development of practical metamaterials with small volumes and broadband properties. We propose to reduce the electrical sizes of metamaterials down to more sub-wavelength scales by lowering the plasma frequencies of metallic wires. The theoretical model is firstly established by analyzing the plasma frequency of continuous thin wires. By introducing more inductance elements, the effective electron mass can be enhanced drastically, leading to significantly lowered plasma frequencies. Based on this theory, we demonstrate that both the electric and the magnetic plasma frequencies of metamaterials can be lowered significantly and thus the electrical sizes of metamaterials can be reduced to more sub-wavelength scales. This provides an efficient route to deep sub-wavelength metamaterials and will give rigorous impetus for the further development of practical metamaterials.

Qin, Gang; Wang, Jia-Fu; Yan, Ming-Bao; Chen, Wei; Chen, Hong-Ya; Li, Yong-Feng

2013-08-01

341

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

342

Hydrogen Cyanide H(13)C(14)N Absorption Reference for 1530 nm to 1560 nm Wavelength Calibration-SRM-2519. Standard Reference Materials.  

National Technical Information Service (NTIS)

Standard Reference Material (SRM) 2519 is an optical-fiber-coupled abosption 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 acc...

S. L. Gilbert W. C. Swann C. M. Wang

1998-01-01

343

Coherence techniques at extreme ultraviolet wavelengths  

NASA Astrophysics Data System (ADS)

The renaissance of Extreme Ultraviolet (EUV) and soft x-ray (SXR) optics in recent years is mainly driven by the desire of printing and observing ever smaller features, as in lithography and microscopy. This attribute is complemented by the unique opportunity for element specific identification presented by the large number of atomic resonances, essentially for all materials in this range of photon energies. Together, these have driven the need for new short-wavelength radiation sources (e.g. third generation synchrotron radiation facilities), and novel optical components, that in turn permit new research in areas that have not yet been fully explored. This dissertation is directed towards advancing this new field by contributing to the characterization of spatial coherence properties of undulator radiation and, for the first time, introducing Fourier optical elements to this short-wavelength spectral region. The first experiment in this dissertation uses the Thompson-Wolf two-pinhole method to characterize the spatial coherence properties of the undulator radiation at Beamline 12 of the Advanced Light Source. High spatial coherence EUV radiation is demonstrated with appropriate spatial filtering. The effects of small vertical source size and beamline apertures are observed. The difference in the measured horizontal and vertical coherence profile evokes further theoretical studies on coherence propagation of an EUV undulator beamline. A numerical simulation based on the Huygens-Fresnel principle is performed. Accurate knowledge of the refractive index in this wavelength region is of fundamental importance for the design of optical systems. However, due to the high absorption, no previous direct measurement of the real part of the refractive index has been performed at EUV wavelengths. To overcome these limitations, a novel diffractive optical element based on Fourier optics techniques is invented, fabricated, and demonstrated for the first time. The improved efficiency of the interferometer employing this novel optical element enables the first direct measurement of the refractive index at EUV wavelengths. Both the real and imaginary parts of the complex refractive indices are measured directly, without recourse to Kramers-Kronig transformations. Data for Al and Ni, in the vicinity of their L and M-edges, respectively, are presented as first examples of this technique. The first novel Fourier optical element used in the above EUV interferometer is also discussed in detail. This diffractive optical element, when illuminated by a uniform plane wave, will produce two symmetric off-axis first order foci suitable for interferometric experiments. In addition to the symmetricalness, the flux throughput is improved by ˜10 times as compared with separate elements providing the same functionality. The efficiency of this optical element is measured. Future work on computer generated holograms is suggested and compared with the Fourier optical element. The invention of this Fourier optical element opens a new era in the use of sophisticated optical techniques at short wavelengths.

Chang, Chang

344

Wavelength Dependence of Polarization. XIII. Interstellar Extinction and Polarization Correlations.  

National Technical Information Service (NTIS)

Observations of the wavelength dependence of polarization and UBVRI photometry of highly polarized stars were made. Two extreme cases of the wavelength dependence of the interstellar polarization were found: the maximum polarization of stars HD 147889 and...

K. Serkowski T. Gehrels W. Wisniewski

1968-01-01

345

LkH? 101 at millimeter wavelengths  

NASA Astrophysics Data System (ADS)

We present new millimeter observations made with the IRAM interferometer and 30 m telescope of the ionized wind from the massive young stellar object LkH? 101. Several recombination lines, including higher order transitions, were detected for the first time at radio wavelengths in this source. From three ?-transitions, we derive an accurate value for the stellar velocity and for the first time, an unambiguous expansion velocity of the wind that is 55 km s-1. This velocity is much slower than reported previously, and the resulting mass loss rate is 1.8 × 10-6 M? yr-1. The wideband continuum spectra and the interferometer visibilities show that the density of the wind falls off more steeply than what is compatible with constant-velocity expansion. We argue that these properties indicate that the wind is launched from a radially narrow region of the circumstellar disk, and we propose that slow speed and a steep density gradient are characteristic properties of the evolutionary phase, where young stars of intermediate and high mass clear away the gaseous component of their accretion disks. The recombination lines are emitted close to local thermal equilibrium, but the higher order transitions appear systematically broader and weaker than expected, probably because of impact broadening. Finally, we show that LkH? 101 shares many properties with MWC 349, the only other stellar wind source where radio recombination lines have been detected, with some of them masing. We argue that LkH? 101 evades masing at millimeter wavelengths because of the disk's smaller size and unfavorable orientation. Some amplification may however be detectable at shorter wavelengths.

Thum, C.; Neri, R.; Báez-Rubio, A.; Krips, M.

2013-08-01

346

Multi-wavelength switching in SOAs  

NASA Astrophysics Data System (ADS)

Four-wave mixing (FWM) has potential to become an enabling technology of the future alloptical communication systems. FWM was used for laboratory demonstrations of multiplexing/demultiplexing in ultra- high speed time-division multiplexed (TDM) communication systems. This thesis focuses on FWM in wavelength division multiplexed (WDM) optical communication system. It was proposed to use FWM as all-optical, transparent, modulation format independent technique for partial or complete wavelength conversion in optical cross-connects. In this thesis, next generation integrated wavelength converters using multiple FWM in a single device are investigated. Potential applications are in future optical cross-connects (OXCs) with reduced complexity. The scope is this thesis is on multiple FWM in semiconductor optical amplifiers (SOAs) and its applicability as wavelength converter in WDM communication systems. A theoretical and experimental investigation of SOA saturation behavior under strong optical injection and a characterization of signal distortion through intersymbol interference (ISI) is included. Methods to minimize power penalties through ISI are outlined. It is concluded that for FWM using high pump power levels, ISI is minimized. Previously, this improvement was solely attributed to signal-to-noise ratio improvements only. The investigation of integrated FWM focuses on two configurations: a novel independently controlled FWM configuration and a multi-probe/single pump configuration. For both systems, limiting factors are investigated. Specifically, frequency response, FWM efficiency, signal-to-noise ratio, extinction ratio, crosstalk through FWM and crosstalk through cross gain modulation (XGM) are addressed. Strategies on improving FWM performance by minimizing these detrimental effects are given. Finally, dual channel independently controlled FWM in a single SOA is successfully demonstrated and limitations of the multi-probe/single pump configurations are pointed out. Based on this research, it is concluded that presently, FWM performance is limited by the current SOA devices. Up to now, SOA optimization for FWM application was performed through increase in amplifier length; systematic optimization procedures might lead to significant improvements in SOA performance. In this thesis, a physically based statespace representation of a SOA is introduced. Through this work, integrated SOA optimization strategies will become feasible.

Scholz, Christoph J.

347

Dual-wavelength moisture meter for clay  

NASA Astrophysics Data System (ADS)

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

Norgia, Michele; Pesatori, Alessandro

2012-10-01

348

Multi-wavelength compressive computational ghost imaging  

NASA Astrophysics Data System (ADS)

The field of ghost imaging encompasses systems which can retrieve the spatial information of an object through correlated measurements of a projected light field, having spatial resolution, and the associated reflected or transmitted light intensity measured by a photodetector. By employing a digital light projector in a computational ghost imaging system with multiple spectrally filtered photodetectors we obtain high-quality multi-wavelength reconstructions of real macroscopic objects. We compare different reconstruction algorithms and reveal the use of compressive sensing techniques for achieving sub-Nyquist performance. Furthermore, we demonstrate the use of this technology in non-visible and fluorescence imaging applications.

Welsh, Stephen S.; Edgar, Matthew P.; Jonathan, Phillip; Sun, Baoqing; Padgett, Miles J.

2013-03-01

349

Water vapor estimates using simultaneous dual-wavelength radar observations  

Microsoft Academic Search

A technique for the estimation of humidity in the lower troposphere using simultaneous dual-wavelength radar observations is proposed and tested. The method compares the reflectivity from clouds and precipitation of a non-attenuated wavelength (S-band, 10 cm) and an attenuated wavelength (Ka-band, 8 mm) to compute the clear-air gaseous attenuation at the attenuated wavelength. These estimates are of total gaseous attenuation

Scott M. Ellis; Jothiram Vivekanandan

2010-01-01

350

Dual-wavelength parallel interferometer with superhigh resolution  

NASA Astrophysics Data System (ADS)

A dual-wavelength parallel interferometer for subnanometer displacement measurement is introduced. A synthetic wavelength is used to subdivide the fringes formed by a single wavelength. An experimental setup that uses a heat-stabilizing dual-wavelength 633-nm He-Ne laser as the light source is established. The primary experimental result shows that a resolution of 0.210 nm over a 350-nm range has been achieved.

Zhao, Yang; Cheng, Xiaohui; Li, Dacheng

2002-04-01

351

Wavelength conversion characteristics of optical packets using digital wavelength converter based on optical SSB modulator  

NASA Astrophysics Data System (ADS)

We have already proposed the wavelength conversion method which is composed of an optical Single Side-Band (SSB) modulator and Mach-Zehnder interferometer (MZI). The optical signal is converted by using basic part of this wavelength converter with 50GHz frequency conversion. We have observed the converted frequency optical spectra, eye diagrams and bit error-rate. The converted optical signals are detected without bit error, but the received optical power at 10-9 error rate is degraded by the conversion because of the optical amplifier noise and filtering by MZI. The wavelengths of 10Gbit/s optical packets are converted by this basic unit. The converted packets are routed using AWG de-multiplexer. The carrier components are around 15dB lower compared with signal. The switching time was 200ns which is correspond to the delay of the loop.

Takahiro, Kawada; Kenichi, Sasaki; Katsushi, Iwashita

2010-12-01

352

Analysis of hot-potato optical networks with wavelength conversion  

Microsoft Academic Search

The performance of wavelength routed optical networks (WRONs) employing packet switching critically depends on packet contentions at the intermediate nodes. This paper shows that, when the active nodes are provided with a number of optical receivers\\/transmitters equal to the number of wavelengths, routing without buffers, known as hot-potato [1], in conjunction with full wavelength conversion becomes an interesting option to

Alberto Bononi; G. A. Castanon; Ozan K. Tonguz

1999-01-01

353

Adaptive wavelength routing in all-optical networks  

Microsoft Academic Search

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

Ahmed Mokhtar; Murat Azizo?lu

1998-01-01

354

Optimal Routing and Wavelength Assignment in All-Optical Networks  

Microsoft Academic Search

The author consider the problem of routing connections in an optical network using wavelength division multiplexing, where each connection between a pair of nodes in the network is assigned a path through the network and a wavelength on that path, such that connections whose paths share a common link in the network are assigned different wavelengths. They derive an upper

Rajiv Ramaswami; Kumar N. Sivarajan

1994-01-01

355

All-optical networks with sparse wavelength conversion  

Microsoft Academic Search

We study the effects of topological connectivity and wavelength conversion in circuit-switched all-optical wavelength- routing networks. A blocking analysis of such networks is given. We first propose an analytical framework for accurate analysis of networks with arbitrary topology. We then introduce a model for networks with a variable number of converters and analyze the effect of wavelength converter density on

Suresh Subrarnaniam; Murat Azizo?lu; Arun K. Somani

1996-01-01

356

Nonlinear conversion of Ti:sapphire laser wavelengths  

Microsoft Academic Search

We review a series of experimental investigations into the use of nonlinear optics to shift wavelengths generated by the tunable Ti:sapphire laser. We consider two basic approaches: harmonic generation (and the related process of sum frequency generation) to reach shorter wavelengths, and optical parametric generation to cover longer wavelengths. Both techniques have been aided by the development of two sets

Glen A. Rines; Henry H. Zenzie; Richard A. Schwarz; Yelena Isyanova; Peter F. Moulton

1995-01-01

357

Wavelength conversion experiment using fiber four-wave mixing  

Microsoft Academic Search

Wavelength conversion using fiber four-wave mixing in an optical fiber is demonstrated. Utilizing the wavelength region around the zero-dispersion wavelength of a fiber, 622 Mbt\\/s FSK signal light is converted from 1555.2 to 1547.6 nm with a conversion efficiency of -24 dB

Kyo Inoue; Hiromu Toba

1992-01-01

358

Accurate strain measurements with fiber Bragg sensors and wavelength references  

Microsoft Academic Search

Fiber Bragg grating (FBG) sensors are one of many fiber optic sensor technologies that are currently being used in structural health monitoring systems. The sensors operate by detecting a shift in the wavelength of the reflected maxima due to applied strain. This paper studies a new fiber Bragg interrogation method that combines a swept wavelength laser in combination with wavelength

E. Rivera; D. J. Thomson

2006-01-01

359

Quantification of the hematoporphyrin derivative by fluorescence measurementusing dual-wavelength excitation anddual-wavelength detection.  

PubMed

A theory is presented describing a method for quantitative measurement of fluorophores in vivo. The method employs a combination of two-wavelength excitation and two-wavelength detection. A dimensionless fluorescence ratio is defined. The theory predicts that this ratio is a function of the concentration of the fluorophore only and is independent of optical properties, independent of geometrical parameters, and independent of autofluorescence. Experiments using a O.1-10-microg/mL hematoporphyrin derivative in a tissue phantom with the optical properties of the dermis show good agreement with theory. PMID:20802722

Sinaasappel, M; Sterenborg, H J

1993-02-01

360

Sulfur dioxide absorption at DF laser wavelengths  

NASA Astrophysics Data System (ADS)

The absorption of DF laser lines by sulfur dioxide under atmospheric conditions is measured in light of the possible application of optical methods to the detection of the atmospheric pollutant. Absorption measurements were performed for 20 DF laser wavelengths between 2792 and 2509 kaysers in a multipass absorption cell. Weak absorption is detected around a wavelength of 3.7 microns and is attributed to the 2 nu 3 band of SO2. The P 4(6) line at 3.9843 microns is found to be strongly absorbed by the (nu 1 + nu 3) band of SO2, with a specific absorption coefficient of 0.44 + or - 0.01/cm per atm, which indicates that strong SO2 emissions in the atmosphere can be detected optically. Measurements of the pressure dependence of the absorption coefficient of the P4(6) line reveal broadening coefficients between 1.5 and 5 MHz/Torr, depending on line strength, and a wavenumber difference of 0.0043 + or - 0.0004 kaysers from the P4(6) DF line to the center of the nearest SO2 line.

Altmann, J.; Pokrowsky, P.

1980-10-01

361

Short wavelength topography on the inner-core boundary  

PubMed Central

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

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2007-01-01

362

Short wavelength topography on the inner-core boundary.  

PubMed

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

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2006-12-26

363

Short Wavelength Topography on the Inner Core Boundary  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

364

All-optical correlation-based bit-pattern recognition with reduced wavelength sensitivity using wavelength conversion  

Microsoft Academic Search

We demonstrate a method of minimizing the wavelength sensitivity of the all-optical bit-pattern recognition relying on a passive optical correlator. We accomplish all-optical 40-Gb\\/s, 8-bit pattern recognition with much reduced wavelength sensitivity by combining a wavelength converter front-end and a passive optical correlator.

I. Kang; M. Rasras; M. Dinu; L. Buhl; S. Cabot; L. Zhang; M. Cappuzzo; L. T. Gomez; Y. F. Chen; S. S. Patel; D. T. Neilson; C. R. Giles; N. Dutta; A. Piccirilli; J. Jaques

2009-01-01

365

An Optimization Approach to Routing and Wavelength Assignment in WDM All-Optical Mesh Networks without Wavelength Conversion  

Microsoft Academic Search

This paper considers a routing and wavelength assign- ment problem (RWAP) for the implementation of efficient Wavelength Division Multiplexing all-optical mesh net- works without wavelength conversion. For a given physical network and required connections, the solution to the RWAP consists in how to select a suitable path and wave- length among the many possible choices for each connec- tion so

Kyungsik Lee Lee; Kug Chang Kang Kang; Taehan Lee Lee; Sungsoo Park Park

2002-01-01

366

Fiber grating sensor array interrogation with direct-wavelength readout of a wavelength-scanned fiber laser  

Microsoft Academic Search

We present a novel interrogation method to measure wavelength shifts in fiber Bragg grating sensor array. A fiber laser tuned by an intracavity FP (Fabry-Perot) filter was used to interrogate Bragg wavelength variations. To solve the linearity, stability, and accuracy problems caused by the nonlinear response of FP filter, we calculated the wavelength variation of the fiber laser using quadrature

Minho Song

2003-01-01

367

Tunable optical tweezers for wavelength-dependent measurements  

PubMed Central

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

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

2012-01-01

368

Temperature Characteristics of Monolithically Integrated Wavelength-Selectable Light Sources  

NASA Astrophysics Data System (ADS)

The temperature characteristics of monolithically integrated wavelength-selectable light sources are experimentally investigated. The wavelength-selectable light sources consist of four distributed feedback (DFB) lasers, a multimode interferometer coupler, and a semiconductor optical amplifier. The oscillating wavelength of the DFB laser could be modulated by adjusting the device operating temperature. A wavelength range covering over 8.0nm is obtained with stable single-mode operation by selecting the appropriate laser and chip temperature. The thermal crosstalk caused by the lateral heat spreading between lasers operating simultaneously is evaluated by oscillating-wavelength shift. The thermal crosstalk approximately decreases exponentially as the increasing distance between lasers.

Han, Liang-Shun; Zhu, Hong-Liang; Zhang, Can; Ma, Li; Liang, Song; Wang, Wei

2013-10-01

369

Science Results from the Long Wavelength Demonstrator Array  

NASA Astrophysics Data System (ADS)

We present recent scientific results from the Long Wavelength Demonstrator Array (LWDA), a 16 element, full polarization, active dipole antenna array located near the Very Large Array (VLA) in New Mexico. The LWDA is a technology pathfinder for the Long Wavelength Array (LWA, http://lwa.unm.edu) operating over a frequency range of 60-80 MHz, and has been used in two principal scientific investigations. First, LWDA interferometer measurements contributed to a recent study of the secular decrease of the low frequency intensity of Cassiopeia A ("Cas A"). LWDA data was combined with archival 74 MHz VLA data together with data in the literature to confirm (1) the secular decrease is slower than originally predicted, (2) the rate of decrease has been relatively stable for the last 50 years, and (3) the rate of secular decrease between 38 and 74 MHz is nearly identical. The results also demonstrated that there are significant fluctuations about the secular decrease with periods between 3 and 20 years. Further monitoring is needed to search for oscillations on shorter time scales and to explore the frequency dependence (if any) of the fluctuations to constrain their physical origin(s). The second project was an all-sky search for low frequency transient sources. A data processing pipeline was developed to use LWDA observations to construct all-sky images, exploiting the near all-sky field-of-view of the individual antennas and to detect sources within them. A total of 83 hours of "on-sky" time over a six month period was searched for transient sources, and no candidates were found. We compare our results with various transient classes to assess their detectability and place our results in context to previous searches. These studies serve as scientific pathfinders for the emerging much larger dipole-based arrays including the LWA, Low Frequency Array (LOFAR), and Murchison Wide-field Array (MWA).

Helmboldt, Joseph; Kassim, N.; Lazio, T.; Clarke, T.; Gross, C.; Hartman, J.; Lane, W.; Ray, P.; Wood, D.; York, J.

2010-01-01

370

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

PubMed Central

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

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

2013-01-01

371

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

NASA Astrophysics Data System (ADS)

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

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

2004-11-01

372

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

373

Wavelength dispersive X-ray fluorescence imaging.  

PubMed

A new wavelength-dispersive X-ray fluorescence (WD-XRF) imaging spectrometer equipped with a two-dimensional X-ray detector was developed in the laboratory. Straight polycapillary optics was applied instead of a soller slit, which is used in conventional WD-XRF spectrometers. X-rays were guided through the straight polycapillary to the exit of the optics by X-ray external total reflections. X-ray fluorescence was dispersed by an analyzing crystal (LiF(200)), keeping the information of elemental distribution on the surface of the sample. The energy resolution of the developed spectrometer was 130-152 eV at the Zn K? peak. X-ray elemental images of Cu K? and Ni K? were successfully obtained by an X-ray CCD detector at the corresponding diffraction angles. The analytical performance of this technique, and further improvements are discussed. PMID:21749148

Tsuji, Kouichi; Ohmori, Takashi; Yamaguchi, Makoto

2011-07-27

374

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

375

High efficiency photonic crystal based wavelength demultiplexer.  

PubMed

A highly efficient design of a two-channel wavelength demultiplexer in the visible region is presented with finite-difference time-domain simulations. The design process is described in detail with particular attention to the challenges inherent in fabrication of an actual device. A 2D triangular lattice photonic crystal with 75nm air pores in a silicon nitride planar waveguide provides the confinement for visible light. The device losses due to fabrication errors such as stitching misalignment of write fields during e-beam lithography and variation in air pore diameters from etching are modeled using realistic parameters from initial fabrication runs. These simulation results will be used to guide our next generation design of high efficiency photonic crystal based demultiplexing devices. PMID:19529162

Tekeste, Meron Y; Yarrison-Rice, Jan M

2006-08-21

376

New pulsars discovered at 3-m wavelength  

NASA Astrophysics Data System (ADS)

Results of a search of the northern sky for pulsars at a wavelength of 3 m are presented. Observations were carried out at 102.5 MHz with the BSA phased antenna array and a 16-channel radiometer with a 160-kHz channel bandwidth using four antenna beams. The coordinates, periods, dispersion measures and flux densities of the three pulsars discovered, PSR 1632+24, PSR 1839+56 and PSR 2110+27, are indicated, along with sample traces of individual pulses. It is pointed out that the three pulsars have nearly the same dispersion measure (24-27 pc/cu cm), relatively high flux densities (greater than 0.1 Jy), and apparently steeper spectra than the average pulsar.

Shitov, Y. P.; Kuzmin, A. D.; Kutuzov, S. M.; Ilyasov, Y. P.; Alekseev, Y. I.; Alekseev, I. A.

1980-04-01

377

Imaging Jupiter's Aurora at Visible Wavelengths  

NASA Astrophysics Data System (ADS)

On November 9, 1996 and again on April 2, 1997, the Galileo spacecraft's Solid State Imaging (SSI) camera targeted the northern auroral region of Jupiter. These observations represent (i) the first spatially resolved images of the jovian auroral oval either at visible wavelengths or on the nightside of the planet, (ii) the first image at visible wavelengths of an auroral footprint of the Io Flux Tube (IFT), (iii) the first unambiguous detection at visible wavelengths of auroral emission on the jovian limb, and (iv) the first images of the aurora with spatial resolution below 100 km per pixel (46 and 35 km, respectively). Relative to many prior expectations, the visible aurora is (i) lower in altitude, (ii) associated with magnetic field lines that cross the equator closer to the planet, and (iii) more variable in time and space. The 1996 images used a clear (broadband) filter, while the 1997 images used both the clear filter and five narrower filters over wavelengths ranging from violet to 968 nm. The filtered images imply that the visible auroral emission contains atomic hydrogen lines, although there is also a continuum component. We were able to position the aurora in three-dimensional space and found the limb emission to be ˜240 km above the surface of a standard ( P? 1 bar) reference ellipsoid. Our most accurate analysis of the equatormost part of the oval placed it at 54.5° planetocentric latitude and 168° west longitude. Combined with the latest magnetic field models, our results imply that the particles that cause the aurora originate in Jupiter's equatorial plane ˜13 RJfrom the center of the planet. The oval was brighter and wider in the 1996 images than in the 1997 images. The broadband radiance of a typical place on the oval as seen directly overhead varied from ˜80 kR in 1997 to ˜300 kR in 1996. Our estimates of the full width of the oval varied from under 500 km to over 8000 km, partly depending on the signal-to-noise ratio of the image. The radiated power per unit length along the oval ranged from ˜60 to ˜700 W/m, with the associated radiated power from the entire oval varying from ˜10 9to ˜9 × 10 10W. Appreciable auroral emission also occurred both north and south of the main oval. One image contains the northern footprint of the IFT, which appears as a central ellipse with a tail of emission that lies downstream with respect to the plasma flow past Io. The central ellipse is ˜1200 km downstream by ˜500 km cross stream. The IFT is comparable in brightness to the nearby auroral oval (˜250 kR) and has a total radiated power of ˜3 × 10 8W.

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

1998-09-01

378

Two-wavelength photorefractive dynamic optical interconnect.  

PubMed

A novel architecture for a reconfigurable optical routing switch using photorefractive crystals with nondestructive readout is presented. This design reduces the order of complexity from n(2) to n for a general two-wavelength n x n holographic interconnection network. The packing capacity of the network is discussed and is calculated to be of the order of 1000 x 1000 for an ideal volume holographic recording material. In practice, we show that the actual value is constrained by the number of gratings that can be multiplexed in a single photorefractive crystal. A 2 x 3 switch is demonstrated by using a Bi(12)GeO(20) crystal with 514-nm writing beams and 633-nm signal (readout) beams. PMID:19759625

McRuer, R; Wilde, J; Hesselink, L; Goodman, J

1989-11-01

379

Handheld four-wavelength retinal vessel oximeter  

NASA Astrophysics Data System (ADS)

Several techniques for measuring the oxygen saturation of blood in retinal vessels have been reported. One interesting application of retinal vessel oximetry is the identification of occult blood loss in trauma victims. However, all the devices described to date are too bulky and cumbersome to be used in a trauma bay or in the field. We present a design for a handheld instrument that performs four-wavelength retinal vessel oximetry. This device is comparable in size and weight to a commercially available camcorder, and is suitable for use in the trauma bay. The compact size of this device could also extend its applications beyond traditional clinical settings, as it could be used by primary care physicians and home health care workers for the screening and monitoring of ophthalmic diseases. Principles of operation and preliminary data from the device will be described.

Heaton, Larry C.; Smith, Matthew H.; Denninghoff, Kurt R.; Hillman, Lloyd W.

2000-06-01

380

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

381

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

382

Development of a wavelength-shifting fiber-based photon detector for LBNE  

NASA Astrophysics Data System (ADS)

The proposed LBNE experiment will employ liquid argon TPCs for the far detector. We are developing a photon detector prototype based on wavelength-shifting fibers and utilizing silicon photomultipliers for potential use in the LBNE far detector. This paper describes progress and plans of the prototype development. An update on the development of a cryogenic detector development test facility, which includes a 500 L cryostat designed for testing full-scale photon detector components for LBNE will also be covered.

Wasserman, R.; Buchanan, N.

2013-10-01

383

Plasmonic Nano-Slot Antennas for Optical Sub-Wavelength Focusing  

Microsoft Academic Search

A novel plasmonic holographic screen consisting of three nano-scaled slits is proposed to produce sub- wavelength near-field focusing at optical frequencies. This design is inspired by near-field holographic screens constructed at microwave frequencies as well as the concept of plasmonic optical antennas. This paper demonstrates its focusing capability through both theoretical analysis and 3D fullwave simulations. With a simple structure

Yan Wang; Alex M. H. Wong; Amr S. Helmy; George V. Eleftheriades

384

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

SciTech Connect

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

Papin, Pallas A.

2012-06-01

385

Recent activities on antenna measurements at mm- and submm-wavelengths at Aalto University  

Microsoft Academic Search

Department of Radio Science and Engineering at Aalto University is studying and developing antenna measurement techniques at mm- and submm-wavelengths. The research projects are ranging from meter-scale satellite antenna testing to millimetre-sized focal plane array (FPA) element characterization for imaging application. The expertise and novel results gained in the abovementioned research are made available to doctoral students and antenna engineers

A. V. Raisanen; J. Ala-Laurinaho; A. Karttunen; J. Mallat; P. Pousi; A. Tamminen

2011-01-01

386

Tracking nucleation, growth, and sublimation in cirrus clouds using ARM millimeter-wavelength radar observations  

Microsoft Academic Search

On the basis of a case study we outline a stochastic approach to investigate the internal structure of radiative properties of cirrus clouds and place it into the context of the state of the large-scale atmosphere. We analyze radar reflectivity eta(t) measurements obtained with the ground-based millimeter-wavelength radar of the Atmospheric Radiation Measurements (ARM) Program of the Department of Energy

K. Ivanova; T. P. Ackerman

2009-01-01

387

Tracking nucleation, growth, and sublimation in cirrus clouds using ARM millimeter-wavelength radar observations  

Microsoft Academic Search

On the basis of a case study we outline a stochastic approach to investigate the internal structure of radiative properties of cirrus clouds and place it into the context of the state of the large-scale atmosphere. We analyze radar reflectivity ?(t) measurements obtained with the ground-based millimeter-wavelength radar of the Atmospheric Radiation Measurements (ARM) Program of the Department of Energy

K. Ivanova; T. P. Ackerman

2009-01-01

388

Spin-flip Raman laser at wavelengths up to 16.8 mum  

Microsoft Academic Search

An InSb spin-flip Raman (SFR) laser is pumped with an optically pumped NH3 laser line at 780.515 cm-1 to obtain tunable first Stokes laser radiation at wavelengths up to 16.8 mum. We report results on the power output, tunability, and preliminary spectroscopy of UF6. Scaling of the primary CO2 pump laser as well as the NH3 laser together with the

C. K. N. Patel; T. Y. Chang; V. T. Nguyen

1976-01-01

389

Spin-flip Raman laser at wavelengths up to 16.8 ?m  

Microsoft Academic Search

An InSb spin-flip Raman (SFR) laser is pumped with an optically pumped NH3 laser line at 780.515 cm?1 to obtain tunable first Stokes laser radiation at wavelengths up to 16.8 ?m. We report results on the power output, tunability, and preliminary spectroscopy of UF6. Scaling of the primary CO2 pump laser as well as the NH3 laser together with the

C. K. N. Patel; T. Y. Chang; V. T. Nguyen

1976-01-01

390

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

SciTech Connect

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

Druzhinin, Y.P.; Chirkova, E.G. [Institute of Radio Engineering and Electronics, Moscow (Russian Federation)

1995-09-01

391

Particle Characterization of European and Indo-Asian Pollution Plumes With Six-Wavelength Lidar  

Microsoft Academic Search

The institute's scanning six-wavelength aerosol lidar allows a comprehensive characterization of atmospheric particles on a vertical scale. The system provides highly accurate profiles of the spectrum of the particle backscatter coefficient between 355 and 1064 nm, and of extinction coefficients and extinction-to-backscatter (lidar) ratios at 355 and 532 nm. Effective radius, volume and surface-area concentration, and complex refractive index of

D. Mueller; K. Franke; A. Ansmann; F. Wagner; D. Althausen

2001-01-01

392

A unified physical scaling law for tokamak energy confinement  

Microsoft Academic Search

From the equations which describe local transport in a turbulent plasma the scaling of the local diffusivity with the plasma parameters can be established. It is shown that, by appropriate choices of time and length scales for the turbulence, the scaling of the global energy confinement can be cast in two limiting forms: a short and a long wavelength scaling.

J. P. Christiansen; J. G. Cordey; K. Thomsen

1990-01-01

393

Long wavelength infrared photodetector design based on electromagnetically induced transparency  

NASA Astrophysics Data System (ADS)

A novel long-wavelength infrared (IR) photodetector based on Electromagnetically induced transparency (EIT) which is suitable for operation in about room temperature and THz range is proposed and analyzed in detail in this article. The main point in this paper for operation in room temperature is related to convert the incoming long-wavelength IR signal to short-wavelength or visible probe optical field through EIT phenomena. For realization of the idea, we used 4, 5- and 6-level atoms implemented by quantum wells or dots. In the proposed structure long-wavelength IR signal does not interact directly with electrons, but affects the absorption characteristics of short-wavelength or visible probe optical field. Therefore, the proposed structure reduces and cancels out the important thermionic dark current component. So, the proposed idea can operate as long wavelength photodetector.

Zyaei, M.; Saghai, H. Rasooli; Abbasian, K.; Rostami, A.

2008-07-01

394

Design of wavelength-selective waveplates using genetic algorithm  

NASA Astrophysics Data System (ADS)

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

Katayama, Ryuichi

2013-03-01

395

Wavelength dependent, tunable, optical time delay system for electrical signals  

NASA Astrophysics Data System (ADS)

Disclosed is a wavelength dependent, tunable, optical time delay system for electronic signals having a conversion/tuning unit for converting an incoming electrical signal into an optical signal as well as selectively varying the wavelength of the optical signal; a single-mode, high dispersion optical fiber for receiving the optical signal and through which the optical signal propagates at a speed dependent upon its wavelength; and a detector/convertor for converting the optical signal back to an electrical outlet. By utilizing a separate preselected electronic control-field fed to the conversion/tuning unit, the wavelength of the optical signal entering the fiber can be varied over a preselected wavelength band of interest. By selectively varying the wavelength of the optical signal, the electrical signal can be effectively and rapidly time delayed as desired in response to the electronic signal.

Soref, R.

1985-02-01

396

Multiple-wavelength digital holographic interferometry using tunable laser diodes  

SciTech Connect

Here we present multiple-wavelength digital holographic interferometry with a wide measurement range using laser diodes. Small wavelength differences can be easily realized by the wavelength tuning of laser diodes with injection current controls. A contour map of an object with a wide measurement range and a high sensitivity is demonstrated by combining a few contour maps with several measurement sensitivities. Synthetic wavelengths are calibrated using a known height difference. This alleviates the need to have high precise knowledge of the recording wavelengths. The synthetic wavelengths ranged from {approx}3 mm for high measurement sensitivity to {approx}4 cm for wide measurement range. An rms error of {approx}35 {mu}m for a {approx}1 cm height measurement is shown. The measured profile of holographic interferometry agrees with a standard stylus instrument.

Wada, Atsushi; Kato, Makoto; Ishii, Yukihiro

2008-04-20

397

Fractional wavelength OCS based on the golden ratio  

Microsoft Academic Search

With current optical switches, an entire wavelength is switched from a source node to a single destination node, thereby precluding fractional wavelength allocation. This shortcoming results in (i) requiring at least N(N-1) wavelengths for complete connectivity of a network with N end nodes; (ii) inability to aggregate\\/separate traffic in the core nodes; and (iii) a mismatch in connecting subnetworks of

Zvi Rosberg; Diethelm Ostry

2008-01-01

398

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

399

Tunable quarter-wave plate for determining light wavelength  

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

400

Multi-Wavelength WiMAX–PONs With Overlapping Cells  

Microsoft Academic Search

An access network architecture integrating stan- dard wireless signal formats over multi-wavelength splitter passive optical networks (PONs) based on radio-over-fiber (RoF) technology is demonstrated. Frequency division multi- plexing (FDM) is applied to address individual base stations sharing a single wavelength. The extended wavelength band overlay overcomes the need for complex dispersion compen- sation techniques as it avoids the use of

Milos Milosavljevic; Pandelis Kourtessis; John M. Senior

2011-01-01

401

Wavelength encoding technique for particle analyses in hematology analyzer  

NASA Astrophysics Data System (ADS)

The aim of this study is to combine multiple excitation wavelengths in order to improve accuracy of fluorescence characterization of labeled cells. The experimental demonstration is realized with a hematology analyzer based on flow cytometry and a CW laser source emitting two visible wavelengths. A given optical encoding associated to each wavelength allows fluorescence identification coming from specific fluorochromes and avoiding the use of noisy compensation method.

Rongeat, Nelly; Brunel, Patrick; Gineys, Jean-Philippe; Cremien, Didier; Couderc, Vincent; Nérin, Philippe

2011-07-01

402

GHRS Ech-B Wavelength Monitor -- Cycle 4  

NASA Astrophysics Data System (ADS)

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

Soderblom, David

1994-07-01

403

Transparent virtual optical code\\/wavelength path network  

Microsoft Academic Search

The concept of a virtual optical code\\/wavelength path (VOCP\\/VWP) is introduced within the transport layer of the network. A potential solution to wavelength path (WP) allocation problems that may limit the expansion of WDM-based transport on mul-networks is demonstrated by employing optical code division multiplexing (OCDM). Key technologies of the VOC\\/VWP concept are both optical code and wavelength conversions. A

Hideyuki Sotobayashi; Wataru Chujo; Ken-ichi Kitayama

2002-01-01

404

Dispersion Trimming in a Reconfigurable Wavelength Selective Switch  

Microsoft Academic Search

We experimentally demonstrate dispersion compensation in a wavelength selective switch, and characterize the bandwidth-dispersion product. At a channel bit-rate of 80 Gbit\\/s, we compensate for various amounts of dispersion (up to ??60 ps\\/nm), tunable for each wavelength division multiplexed channel, solely by adjusting the phase front of the optical signal inside the wavelength selective switch. Error-free operation is obtained for

Steven Frisken; Jeremy A. Bolger; Dmitri Abakoumov; Glenn Baxter; Simon Poole; Benjamin J. Eggleton

2008-01-01

405

Ice crystal size estimation using multiple-wavelength radar  

Microsoft Academic Search

Measurements and simulations of multiple-wavelength radar scattering have demonstrated the feasibility of using multiple-wavelength systems to estimate effective hydrometeor size in ice-phase clouds, and in various forms of precipitation. Radar reflectivity differences occur when the higher frequency experiences non-Rayleigh scattering. For cloud particle sizing, the higher frequency must exhibit non-Rayleigh scattering from small hydrometeors. This occurs at mm-wavelengths where radar

Stephen M. Sekelsky; Robert E. McIntosh; Warner L. Ecklund; Kenneth S. Gage

1998-01-01

406

Short-wavelength automated perimetry in patients with migraine  

Microsoft Academic Search

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

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

2006-01-01

407

Long wavelength free-electron lasers in 1998  

Microsoft Academic Search

A summary of the current status and most important future directions for long wavelength (?0.5mm) free-electron lasers is presented. The distinction between long and short wavelengths is a natural one. For example, space-charge effects may be important for the high currents typically employed at long wavelengths, and the dominant interaction mechanism is often coherent Raman scattering. In addition, dispersion due

H. P. Freund; V. L. Granatstein

1999-01-01

408

Flares from Sagittarius A* at Millimeter Wavelengths  

NASA Astrophysics Data System (ADS)

Flux monitoring programs of Sagittarius A* at millimeter wavelengths were carried out from 1996 to 2001 using the Nobeyama Millimeter Array (NMA). Forty-six epochs of the observations was obtained at 3 mm and 2 mm. In 1996,1997,1998, and 2000, the observations were concentrated in a period of one to two months for each year with the epochs separated by a few days to a week in a single (intermediate resolution) array configuration in order to obtain identical spatial resolution among different epochs of the observations. From November 2000 to May 2001, the observations were performed in six consecutive months to investigate the variability of longer term. The light curve constructed from these data shows flares in March 1998 and in March 2000. The peaks of flares were 2-3 Jy at 3mm while the averaged quiescent flux was ~1Jy with the typical uncertainty of 15-20 %. We folded the NMA light curve with a quasi-period of 106 days determined from the analysis of the VLA data by Zhao, Bower and Goss (2001, ApJ, 547, L29). The folded data shows distinct high and low activity states.

Tsutsumi, T.; Miyazaki, A.; Tsuboi, M.

2002-06-01

409

Underdense radiation sources: Moving towards longer wavelengths  

NASA Astrophysics Data System (ADS)

Underdense radiation sources have been developed to provide efficient laboratory multi-keV radiation sources for radiography and radiation hardening studies. In these plasmas laser absorption by inverse bremsstrahlung leads to high x-ray conversion efficiency because of efficient ionization of the low density aerogel or gas targets. Now we performing experiments in the soft x-ray energy regime where the atomic physics models are much more complicated. In recent experiments at the NIKE laser, we have irradiated a Ti-doped SiO{2} aerogel with up to 1650 J of 248 nm wavelength light. The absolute Ti L-shell emission in the 200-800 eV range is measured with a diagnostic that uses a transmission grating coupled to Si photodiodes. We will give an overview of the temporally-resolved absolutely calibrated spectra obtained over a range of conditions. Eventually we hope to extend our studies to x-ray production in the EUV range.

Back, C. A.; Seely, J. F.; Weaver, J. L.; Feldman, U.; Tommasini, R.; Glendinning, S. G.; Chung, H.-K.; Rosen, M.; Lee, R. W.; Scott, H. A.; Tillack, M.; Kilkenny, J. D.

2006-06-01

410

Multi-wavelength reflectance pulse oximetry.  

PubMed

The performance of current reflectance pulse oximeters is hindered by poor signal-to-noise ratio. To overcome this problem a new reflectance oximeter has been developed with a sensor which consists of three LEDs and two continuous photodetector rings placed equidistant from the center of the LEDs. In addition, ultra low noise electronics and adaptive algorithm assure improved performance. A validation study was performed on 10 healthy volunteers. Sensors were placed on several sites and measurements were compared to reference arterial blood samples. During the study progressive hypoxemia was induced by lowering the inspired oxygen concentration (FiO2) to 10%, followed by a recovery phase. Twelve blood samples were taken during each cycle, yielding a total of 120 measured data points. Data from randomly selected 5 subjects was used for calibration and subsequently tested on the other 5 subjects. Results proved to be well within clinically acceptable boundaries for all 3 sampling sites with high correlation (R2 > 0.9) and SD around 2%. In conclusion, a new 3 wavelength reflectance pulse oximeter with unique sensor geometry and improved algorithms provides enhanced performance and is less susceptible to poor signal to noise conditions when compared to existing reflectance oximetry systems. PMID:11900033

Mendelson, Yitzhak; Lewinsky, Reuven M; Wasserman, Yoram

2002-01-01

411

Design of a Dual Wavelength Birefringent Filter  

NASA Astrophysics Data System (ADS)

The simulation of a tunable dual wavelength birefringent filter is presented with the ultimate goal of developing a novel optical in the terahertz (THz) region of the electromagnetic spectrum for medical applications. THz radiation is located in the electromagnetic around 300 ?m. For a long time this frequency domain has been named the ``THz-gap'' due to the lack of sources and detector systems. Here we present a novel alternative for a THz laser source based on the novel birefringent filter presented. The filter is constructed using four stages quartz plates placed at Brewster angle. The design of the filter was done using a zero diving angle to facilitate its construction, and the tunability in the overall response of the filter is achieved by rotating only one of the plates. The filter was design to have a center response around 980 nm with the peak separation of 2.50 nm to 3.75, corresponding to frequency separation between 0.8 THz to 1.2 THz, compatible with broadband laser sources in the 980 nm vicinity.

Treviño-Palacios, Carlos Gerardo; Wetzel, Corinna; Zapata-Nava, Oscar Javier

2008-04-01

412

Tunable Dual-Wavelength Narrow-Linewidth Microfiber Laser  

NASA Astrophysics Data System (ADS)

A compact and tunable dual-wavelength narrow-linewidth microfiber laser is demonstrated with a novel and high-Q double-knot resonator. Each wavelength laser spectrum delivers a 2 kHz linewidth and an optical side-mode suppression ratio of over 31 dB. The laser wavelength and frequency separation between the two wavelength lasers can be tuned freely by changing the coupling length and position between the taper-drawn fiber and the double-knot resonator.

Fan, Wei; Zhang, Zhishen; Wei, Xiaoming; Gan, Jiulin; Zhan, Biao; Xu, Shanhui; Yang, Zhongmin

2013-07-01

413

Scale dependence and frontal formation of nighttime medium-scale traveling ionospheric disturbances  

NASA Astrophysics Data System (ADS)

Scale dependence of nighttime medium-scale traveling ionospheric disturbances (MSTIDs) is studied with the midlatitude ionosphere electrodynamics coupling model by changing initial perturbation scales. It is shown that both sporadic E (Es) layer and Perkins instabilities have the scale dependence that a shorter wavelength mode tends to stop growing within a shorter period, whereas a very long wavelength mode grows so slowly in the E region that it does not effectively seed the Perkins instability in the F region. As a result, the typical wavelength of MSTIDs (100-200 km) can be spontaneously generated without scale-dependent forcing. It is also shown that long frontal structures of MSTIDs can be formed by the Pedersen polarization process along the wavefront of MSTIDs by which the wavefront is forced to be uniformly distributed.

Yokoyama, Tatsuhiro

2013-09-01

414

Wavelength dependence of the linear growth rate of the Es layer instability  

NASA Astrophysics Data System (ADS)

It has recently been shown, by computation of the linear growth rate, that midlatitude sporadic-E (Es) layers are subject to a large scale electrodynamic instability. This instability is a logical candidate to explain certain frontal structuring events, and polarization electric fields, which have been observed in Es layers by ionosondes, by coherent scatter radars, and by rockets. However, the original growth rate derivation assumed an infinitely thin Es layer, and therefore did not address the short wavelength cutoff. Also, the same derivation ignored the effects of F region loading, which is a significant wavelength dependent effect. Herein is given a generalized derivation that remedies both these short comings, and thereby allows a prediction for the wavelength dependence of the linear growth rate, as well as computations of various threshold conditions. The wavelength dependence of the linear growth rate is compared with observed periodicities, and the role of the zeroth order meridional wind is explored. A three-dimensional paper model is used to explain the instability geometry, which has been defined formally in previous works.

Cosgrove, R.

2006-12-01

415

Wavelength dependence of the linear growth rate of the Es layer instability  

NASA Astrophysics Data System (ADS)

It has recently been shown, by computation of the linear growth rate, that midlatitude sporadic-E (Es) layers should be subject to a large scale electrodynamic instability. This instability is a logical candidate to explain certain frontal structuring events, and polarization electric fields, which have been observed in Es layers by ionosondes, by coherent scatter radars, and by rockets. As such it provides an alternative, or complementary mechanism to that proposed by Larsen, of a Kelvin-Helmholtz instability in the Neutral wind, for explaining more or less the same set of observations. However, the original growth rate derivation assumed an infinitely thin Es layer, and therefore did not address the short wavelength cutoff. Also, the same derivation ignored the effects of F region loading, which is a significant wavelength dependent effect. Herein is given a generalized derivation that remedies both these short comings, and thereby allows a prediction for the wavelength dependence of the linear growth rate, as well as computations of various threshold conditions. The wavelength dependence of the linear growth rate is compared with observed periodicities, and the role of the zeroth order meridional wind is explored.

Cosgrove, R.

2007-12-01

416

Long-wavelength limit of gyrokinetics in a turbulent tokamak and its intrinsic ambipolarity  

NASA Astrophysics Data System (ADS)

Recently, the electrostatic gyrokinetic Hamiltonian and change of coordinates have been computed to order ?2 in general magnetic geometry. Here ? is the gyrokinetic expansion parameter, the gyroradius over the macroscopic scale length. Starting from these results, the long-wavelength limit of the gyrokinetic Fokker-Planck and quasineutrality equations is taken for tokamak geometry. Employing the set of equations derived in the present paper, it is possible to calculate the long-wavelength components of the distribution functions and of the poloidal electric field to order ?2. These higher order pieces contain both neoclassical and turbulent contributions, and constitute one of the necessary ingredients (the other is given by the short-wavelength components up to second order) that will eventually enter a complete model for the radial transport of toroidal angular momentum in a tokamak in the low flow ordering. Finally, we provide an explicit and detailed proof that the system consisting of second-order gyrokinetic Fokker-Planck and quasineutrality equations leaves the long-wavelength radial electric field undetermined; that is, the turbulent tokamak is intrinsically ambipolar.

Calvo, Iván; Parra, Felix I.

2012-11-01

417

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 scal