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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  

NASA Astrophysics Data System (ADS)

Several of the icy satellites of Saturn show the spectroscopic signature of the asymmetric stretching mode of C-O in carbon dioxide (CO 2) at or near the nominal solid-phase laboratory wavelength of 4.2675 ?m (2343.3 cm -1), discovered with the Visible-Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft. We report here on an analysis of the variation in wavelength and width of the CO 2 absorption band in the spectra of Phoebe, Iapetus, Hyperion, and Dione. Comparisons are made to laboratory spectra of pure CO 2, CO 2 clathrates, ternary mixtures of CO 2 with other volatiles, implanted and adsorbed CO 2 in non-volatile materials, and ab initio theoretical calculations of CO 2 * nH 2O. At the wavelength resolution of VIMS, the CO 2 on Phoebe is indistinguishable from pure CO 2 ice (each molecule's nearby neighbors are also CO 2) or type II clathrate of CO 2 in H 2O. In contrast, the CO 2 band on Iapetus, Hyperion, and Dione is shifted to shorter wavelengths (typically ˜4.255 ?m (˜2350.2 cm -1)) and broadened. These wavelengths are characteristic of complexes of CO 2 with different near-neighbor molecules that are encountered in other volatile mixtures such as with H 2O and CH 3OH, and non-volatile host materials like silicates, some clays, and zeolites. We suggest that Phoebe's CO 2 is native to the body as part of the initial inventory of condensates and now exposed on the surface, while CO 2 on the other three satellites results at least in part from particle or UV irradiation of native H 2O plus a source of C, implantation or accretion from external sources, or redistribution of native CO 2 from the interior. The analysis presented here depends on an accurate VIMS wavelength scale. In preparation for this work, the baseline wavelength calibration for the Cassini VIMS was found to be distorted around 4.3 ?m, apparently as a consequence of telluric CO 2 gas absorption in the pre-launch calibration. The effect can be reproduced by convolving a sequence of model detector response profiles with a deep atmospheric CO 2 absorption profile, producing distorted detector profile shapes and shifted central positions. In a laboratory blackbody spectrum used for radiance calibration, close examination of the CO 2 absorption profile shows a similar deviation from that expected from a model. These modeled effects appear to be sufficient to explain the distortion in the existing wavelength calibration now in use. A modification to the wavelength calibration for 13 adjacent bands is provided. The affected channels span about 0.2 ?m centered on 4.28 ?m. The maximum wavelength change is about 10 nm toward longer wavelength. This adjustment has implications for interpretation of some of the spectral features observed in the affected wavelength interval, such as from CO 2, as discussed in this paper.

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

2010-04-01

2

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

USGS Publications Warehouse

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

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

2007-01-01

3

Large-scale anisotropy at centimeter wavelengths  

Microsoft Academic Search

Intrinsic effects in the case of large-scale anisotropy measurements could possibly provide much information about the early universe. Techniques for experimental investigations at centimeter wavelengths are discussed, taking into account the basic problem to measure the difference in the radiation temperature form two directions in the sky with an accuracy of better than 0.0001 K. The largest anisotropy in the

D. T. Wilkinson

1983-01-01

4

NGC 6251 at multiple scales and wavelengths  

E-print Network

We have studied the FR I radio galaxy NGC 6251 and its environment at several wavelengths and scale lengths. On the large scale, we have probed the gravity field by measuring the velocity dispersion of the cluster members associated with NGC 6251 and relating this to the cluster's X-ray emission. On the small scale, the gravitational information is provided by cold HI near the nucleus and the distribution of stars and gas near the centre of the galaxy. The cold HI gas which we have measured explains the absorption of the central X-ray emission and is consistent with the extinction through the recently discovered HST gas disc of NGC 6251.

P. N. Werner; D. M. Worrall; M. Birkinshaw

2000-11-02

5

Effective Wavelength Scaling for Optical Antennas Lukas Novotny*  

E-print Network

Effective Wavelength Scaling for Optical Antennas Lukas Novotny* Institute of Optics, University, antenna parameters are directly related to the wavelength of incident radiation, but this scaling fails wavelength eff n1 n2=p, with p being the plasma wavelength and n1, n2 being coefficients that depend

Novotny, Lukas

6

Wavelength scaling of laser plasma coupling  

SciTech Connect

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

Kruer, W.L.

1983-11-03

7

Wavelength-scale stationary-wave integrated Fourier transform spectrometry  

E-print Network

1 Wavelength-scale stationary-wave integrated Fourier transform spectrometry Etienne le Coarer1 issued by either reflection (as the principle of colour photography by G. Lippmann) or counterpropagative an elegant way of reducing the volume of spectrometer to a few hundreds of cubic wavelengths

Boyer, Edmond

8

Voyager Interstellar Mission (VIM)  

NASA Technical Reports Server (NTRS)

The DSN (Deep Space Network) mission support requirements for the Voyager Interstellar Mission (VIM) are summarized. The general objectives of the VIM are to investigate the interplanetary and interstellar media and to continue the Voyager program of ultraviolet astronomy. The VIM will utilize both Voyager spacecraft for the period from January 1990 through December 2019. The mission objectives are outlined and the DSN support requirements are defined through the presentation of tables and narratives describing the spacecraft flight profile; DSN support coverage; frequency assignments; support parameters for telemetry, control and support systems; and tracking support responsibility.

Rudd, R.; Textor, G.

1991-01-01

9

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

Microsoft Academic Search

During the Cassini–Huygens flyby of Jupiter in December 2000, VIMS-V acquired multispectral data cubes of Jupiter's atmosphere. The visual and infrared imaging spectrometer-visual channel (VIMS-V) is one of the principal contributions of Italian Space Agency (ASI) to the Cassini–Huygens mission to Saturn. VIMS-V is an imaging spectrometer operating in the wavelength range 300–1050nm, with a (nominal) spectral resolution of 7.3nm,

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

2004-01-01

10

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

USGS Publications Warehouse

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

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

2008-01-01

11

Photonic crystal lasers using wavelength-scale embedded active region  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

12

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

E-print Network

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

Lai, Chien-Jen

13

Studies of Titan's 5-Micron-Bright Regions Using Combined VIMS and ISS Observations  

NASA Astrophysics Data System (ADS)

Coanalysis of the datasets obtained by Cassini VIMS (Visual and Infrared Mapping Spectrometer), ISS (Imaging Science Subsystem), RADAR, and the Huygens probe is driving our understanding of Titan's haze- shrouded surface. We find that high spatial resolution imaging of Titan at 0.938um from ISS provides a useful complement to VIMS' spectral image mapping of Titan at 352 wavelengths but lower spatial resolution. We used ISS images from Tb and VIMS cubes from Tb, T5, and T12 to study in detail those areas identified by VIMS to have unusually high surface reflectivities at 5 microns, Tui Regio and Hotei Regio. VIMS' 5-micron- bright Hotei Regio corresponds to a distinctive bright arc in the ISS data. Correlation of high-resolution and color information from western Tui Regio shows flow-like features, possibly of extrusive, cryovolcanic origin. A small-grained water-ice unit surrounding Tui Regio best explains the area's brightness in short-wavelength ISS data relative to VIMS. We will discuss these findings as well as prospects for future VIMS/ISS collaborations.

Barnes, J. W.; Brown, R. H.; Radebaugh, J.; Buratti, B. J.; Sotin, C.; Le Mouelic, S.; Rodriguez, S.; Turtle, E.; Perry, J.; Clark, R.; Baines, K. H.; Nicholson, P.

2006-12-01

14

VIM: Visual Integration and Mining  

NASA Astrophysics Data System (ADS)

VIM (Virtual Observatory Integration and Mining) is a 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 either through web forms, building a custom 'data matrix,' or locally through downloadable Python code. 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.

U. S. National Virtual Observatory (VAO)

2012-01-01

15

Spectrophotometric Modeling of Rhea's Surface from Vims Data  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

16

Universal instability for wavelengths below the ion Larmor scale  

E-print Network

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

Landreman, Matt; Dorland, William

2014-01-01

17

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

Microsoft Academic Search

The kilometer scale irregularities in the daytime equatorial electrojet are studied within the framework of a two-fluid, nonlocal theory of the gradient drift instability. A separation of scales is introduced into the equations in order to model the effects of the subgrid, short-wavelength (λ < 100 m) modes. The presence of the short-scale turbulence is included in the large-scale equations

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

1990-01-01

18

Composition of Titan's surface from Cassini VIMS  

USGS Publications Warehouse

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

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

2006-01-01

19

Surface of Titan : model and VIMS observations  

NASA Astrophysics Data System (ADS)

The Huygens probe has allowed to describe the atmosphere and the surface of Titan in detail. To date, the surface reflectivity as observed by DISR is not fully understood.In this work, we first propose a model of the surface reflectivity made of a layer of ice covered by a layer of fluffy aerosols. This well explains the observed surface reflectivity by DISR, with a reflectivity having a maximum (peak) at 750 nm and a blue slope at longer wavelength and a red slope at shorter wavelength. Our model essentially relies on our ability to model the radiative transfer inside the continuous layer of aerosol sedimented at the surface. However, we also find a shift in the reflectivity peak between the surface reflectivity as observed by DISR and the results obtained when using the aerosol refractive index of airborne aerosols. We propose an explanation for this effect.The second part of the work consists in checking the data. We find that this shift in the reflectivity peak also exits in the data. Using a model of radiative transfer, with a description of the atmosphere properties derived from analysis made by Huygens instruments, we are able to reproduce the intensity observed by VIMS, and we can retrieve the surface albedo. We essentially focus on the aera around Huygens landing site, and we characterize the differences between the bright and dark zones.

Rannou, Pascal; Toledo, Daniel; Adriani, Alberto; Moriconi, Maria Luisa; D'Aversa, Emiliano; Le Mouélic, Stéphane; Sotin, Christophe; Brown, Robert H.

2014-11-01

20

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

NASA Astrophysics Data System (ADS)

The Cassini Visual and Infrared Mapping Spectrometer (VIMS) instrument is an imaging spectrometer covering the 0.4 to 5.1 mu m wavelength region with 352 spectral channels, and with a spacing of approximately 16 nm, and a Full Width at Half Maximum (FWHM) of approximately 13 nm. The VIMS is also a spatial imager with a field of view of 64 by 64 pixels. During the VIMS thermal vacuum testing, a target projector transferred a 10 cm square image into the thermal vacuum chamber where the VIMS was maintained in a space environment similar to what it will encounter at Saturn. The VIMS 64x64 pixel field gave a spatial resolution in the projector focal plane of about 1.5 mm. Several rock and mineral test targets, chosen to have absorption bands in various VIMS wavelength regions, were measured. The resulting imaging spectroscopy data sets were compared in several ways, including pseudo-true color imaging, false color imaging, and spectral mapping with the USGS Tricorder algorithm. The Tricorder algorithms compare spectral features from a spectral library and search for those features in the VIMS data. Color-coded maps of the minerals found are compared to actual knowledge of the minerals present in the rocks. The results illustrate the power of imaging spectroscopy over traditional imaging or false color imaging. Many minerals can't be distinguished in true color, while false color (including IR wavelengths chosen in or near diagnostic absorption bands) discriminates some minerals, but not even all of the same type. For example, a mineral sample depicted red in a false color image may appear as a completely different color for another sample of the same mineral, but with a different grain size. Sample purity also affects false color discrimination. However, spectral analysis properly identifies the mineralogy, thus supporting the prediction that VIMS will be a very effective instrument at Saturn.

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

1996-09-01

21

Projects To Probe Titan's Surface Composition and Development of Atmospheric Removal Models for Cassini VIMS Data  

NASA Astrophysics Data System (ADS)

In this work, we will describe recent projects performed by our group at the Jet Propulsion Laboratory, California Institute of Technology involving I/F data of Titan's surface acquired by Cassini's Visual and Infrared Mapping Spectrometer (VIMS), including the next stage of development of methods to de-gas and de-fog VIMS images. VIMS I/F spectra include contributions from both surface and atmospheric signal; therefore, current spectral data analysis necessarily focuses on portions of VIMS I/F spectra where atmospheric methane and scattering by haze is at a minimum. However, atmospheric opacity clears enough between wavelengths of 1 and 2 microns to provide strong potential to view complex landforms if a proper atmospheric correction can be applied. Plane- parallel radiative transfer (RT) correction methods have been used successfully in surface-atmospheric separation retrievals for Mars and offer some utility for VIMS observations of Titan that are away from the limb. In a previous work (Pitman et al. 2007, LPSC XXXVIII, p. 1164), we determined which inputs to radiative transfer models must be updated, given results from recent meetings and literature, and evaluated two plane-parallel RT models (adding-doubling, discrete ordinates) to determine which is more easily customized for surface- atmospheric separation of Titan. In this work, we report our progress on replacing Voyager with Cassini-Huygens inputs and how these models currently compare. Work performed under contract to NASA and by appointment to the NASA Postdoctoral Program (ORAU).

Pitman, K. M.; Buratti, B. J.; Baines, K. H.; West, R. A.; Wolff, M. J.; Brown, R. H.

2007-05-01

22

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

23

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 a m = 38 ?m; and (3) a surface roughness parameter value of 33°. The study of phase function shows that both shadow hiding and coherent backscattering contribute to the opposition surge. This study represents the first attempt, in the case of Rhea, to join the spectral and the photometric analysis. The surface model we derived gives a good quantitative description of both spectrum and phase curve of the satellite. The same approach and model, with appropriate modifications, shall be applied to VIMS data of the other icy satellites of Saturn, in order to reveal similarities and differences in the surface characteristics to understand how these bodies interact with their environment.

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

24

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra  

USGS Publications Warehouse

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

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

2011-01-01

25

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

26

Energy and wavelength scaling of shock-ignited inertial fusion targets  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

27

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

NASA Astrophysics Data System (ADS)

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

Goguen, Jay D.; Buratti, Bonnie J.

2014-11-01

28

Optical Path Cross-Connect System Scale Evaluation Using Path Accommodation Design for Restricted Wavelength Multiplexing  

Microsoft Academic Search

The optical path (OP) technology, which employs both wavelength-division multiplexing and wavelength routing, will be the key to enhanced network integrity and an ubiquitous broadband integrated services digital network (B-ISDN) in the future. To construct the OP network, path accommodation design that can solve simultaneously the problems of path routing and wavelength assignment must be established. Since optical wavelengths are

Naohide Nagatsu; Satoru Okamoto; Ken-ichi Sato

1996-01-01

29

Wavelength-Selective Switches for Mode-Division Multiplexing: Scaling and Performance Analysis  

NASA Astrophysics Data System (ADS)

Wavelength-selective switches for mode-division-multiplexing systems are designed by scaling switches from single-mode systems. All modes at a given wavelength are switched as a unit, which is necessary in systems with substantial mode coupling, and minimizes the number of ports required to accommodate a given traffic volume. When a pure mode is present at the input, modal transmission and coupling coefficients are mode-dependent and may be computed using a simple mode-clipping model. When multiple modes are present, interference between modes alters the transmission and coupling coefficients, shifting the passband center frequency and changing its bandwidth. Mode-coupling matrices are used to compute mixed modes having the narrowest or widest bandwidths, or having the largest center-frequency offsets. In a specific design for graded-index fiber, five mode groups and 50-GHz channel spacing, the one-sided bandwidth may change up to $\\pm$3.6 GHz. In a system with many cascaded switches and strong mode coupling, the end-to-end response per switch may be characterized by a mode-averaged transmission coefficient.

Ho, Keang-Po; Kahn, Joseph M.; Wilde, Jeffrey P.

2014-11-01

30

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

E-print Network

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

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

2011-10-14

31

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

32

Rotation-induced Mode Coupling in Open Wavelength-scale Microcavities  

E-print Network

We study the interplay between rotation and openness for mode coupling in wavelength-scale microcavities. In cavities deformed from a circular disk, the decay rates of a quasi-degenerate pair of resonances may cross or anti-cross with increasing rotation speed. The standing-wave resonances evolve to traveling-wave resonances at high rotation speed, however, both the clockwise (CW) and counter-clockwise (CCW) traveling-wave resonances can have a lower cavity decay rate, in contrary to the intuitive expectation from rotation-dependent effective index. With increasing rotation speed, a phase locking between the CW and CCW wave components in a resonance takes place. These phenomena result from the rotation-induced mode coupling, which is strongly influenced by the openness of the microcavity. The possibility of a non-monotonic Sagnac effect is also discussed.

Ge, Li; Cao, Hui

2014-01-01

33

Rotation-induced mode coupling in open wavelength-scale microcavities  

NASA Astrophysics Data System (ADS)

We study the interplay between rotation and openness for mode coupling in wavelength-scale microcavities. In cavities deformed from a circular disk, the decay rates of a quasidegenerate pair of resonances may cross or anticross with increasing rotation speed. The standing-wave resonances evolve to traveling-wave resonances at high rotation speed, however both the clockwise (CW) and counterclockwise (CCW) traveling-wave resonances can have a lower cavity decay rate, contrary to the intuitive expectation from the rotation-dependent effective index. With increasing rotation speed, a phase locking between the CW and CCW wave components in a resonance takes place. These phenomena result from the rotation-induced mode coupling, which is strongly influenced by the openness of the microcavity. The possibility of a nonmonotonic Sagnac effect is also discussed.

Ge, Li; Sarma, Raktim; Cao, Hui

2014-07-01

34

Titan's surface as seen by VIMS  

NASA Astrophysics Data System (ADS)

The Cassini spacecraft has been orbiting in the Saturn's system since July 2004. Remote sensing instruments have discovered that Titan's surface is rich in geological features including dunes, river beds, hydrocarbon lakes, seas, impact craters, mountains and cryovolcanic features. This paper reviews the discovery made by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. This review describes several of the outstanding discoveries by VIMS including the composition of lakes, the 5 micron bright cryovolcanic areas, the diversity of geological provinces, the morphology of impact craters, and the location at 1 km uncertainty of the Huygens Landing Site. It also compares the VIMS spectra with data acquired by the DLIS (Downward Looking Infrared Spectrometer) during the descent of the Huygens probe in the spectral domain 900 -1600 nm. Implications of the recent observations of speculare reflections on the northern lakes will be drawn. The Cassini spacecraft begins its second extended mission (Cassini Solstice Mission) with 56 additional Titan flybys. The paper describes the VIMS observations at closest approach which will help answer the science objectives of the CSM. Acknowledgment: This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology under contract with NASA.

Sotin, Christophe; Brown, Robert H.; Lawrence, Ken; Le Mouelic, Stephane; Rodriguez, Sebastien

35

The wavelength dependence of the gross moist stability and the scale selection in the instability of column integrated moist static energy  

E-print Network

1 The wavelength dependence of the gross moist stability and the scale selection in the instability that incorporate feedbacks from the large-scale flow, that the GMS is smaller at longer wavelengths. The reason for this wavelength dependence is that temperature anomalies required to maintain a given divergent flow increase

Kuang, Zhiming

36

Mimas: Preliminary Evidence For Amorphous Water Ice from VIMS  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

37

Optically optimal wavelength-scale patterned ITO/ZnO composite coatings for thin film solar cells  

E-print Network

Optically optimal wavelength-scale patterned ITO/ZnO composite coatings for thin film solar cells-reflective coating made of ITO or ZnO, or a composite ITO/ZnO coating. These latter structures are realistic and present good performances despite very thin active layers. 1 hal-00672568,version1-21Feb2012 #12;I

Paris-Sud XI, Université de

38

Optically optimal wavelength-scale patterned ITO/ZnO composite coatings for thin film solar cells  

E-print Network

Optically optimal wavelength-scale patterned ITO/ZnO composite coatings for thin film solar cells-reflective coating made of ITO or ZnO, or a composite ITO/ZnO coating. These latter structures are realistic and present good performances despite very thin active layers. 1 hal-00672568,version2-13Mar2012 #12;I

Paris-Sud XI, Université de

39

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

40

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

E-print Network

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

Granados, Eduardo

41

Ten Years of VIMS at Saturn  

NASA Astrophysics Data System (ADS)

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

Brown, Robert H.

2014-05-01

42

Scaling of keV HHG photon yield with drive wavelength.  

PubMed

We study semi-analytically and numerically the photon yield of high harmonic generation (HHG) on the level of the single atom response under ideal conditions: no initial depletion of the ground state prior to the main peak of the pump pulse. We show that the yield decreases exponentially as function of the cutoff energy starting at about 0.5keV in the case of a Ti:sapphire source and a helium target. We show that the yield in helium beyond the 1keV energy range can be increased by orders of magnitude when long wavelength driver sources in the range from 1.5 mum to 3 mum are used. This finding leads to the conclusion that significant HHG beyond 1keV is possible through long wavelength driver pulses. PMID:19495190

Gordon, Ariel; Kärtner, Franz

2005-04-18

43

Titan's Surface Composition Investigated by Spectral Mixture Analysis of VIMS/Cassini Data  

NASA Astrophysics Data System (ADS)

The Visual and Infrared Mapping Spectrometer (VIMS) onboard Cassini and ground-based telescopic observations revealed the diversity of Titan's surface composition. The atmosphere is transparent only in seven narrow ranges of wavelength between 1 and 5 µm, and mixtures of materials certainly occur and distort their absorption bands, even in high spectral resolution measurements. As a consequence, some investigations for specific materials are not fully certain or even failed. In addition, aerosol scattering dominates the signal, especially towards short wavelengths. H2O ice has been reported first by Griffith et al. (2003). Other components are only suggested: CH4 (Coustenis et al. (2005), bitumens and tholins (Lellouch et al., 2004) and CO2 ice (Barnes et al., 2006; Rodriguez et al., 2006) but detection attempt failed for CO2 ice (Hartung et al., 2006). The global spectral shape also contains useful information to derive the surface composition. Thus, we focused on the analysis of VIMS spectra after averaging the signal within each atmospheric window. Data are selected between 70 degrees emergence angle and incidence angles less than 45 degrees for more homogeneity. We apply a linear spectral unmixing model to fit VIMS data with similarly windowed laboratory spectra of known materials and a model of aerosol scattering. Image fraction maps suggest a major role of CO2 in bright regions like the 5-µm bright spot at Tui Regio (Barnes et al., 2005). Results are consistent with the 5-µm window analysis reported in the companion abstracts (Hayne et al., 2007 and in McCord et al., 2007, this meeting). This analysis is also in agreement with H2O ice at locations previously reported by Soderblom et al. (2007) . Atmospheric scattering is ubiquitous and quite homogenous. This analysis revealed a spectral component bright at 2 µm that may be used to identify other surface components.

Combe, Jean-Philippe; McCord, T. B.; Hayne, P.; Hansen, G. B.

2007-10-01

44

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

45

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

46

Ablation scaling in laser-produced plasmas with laser intensity, laser wavelength, and target atomic number  

NASA Astrophysics Data System (ADS)

Layered target experiments at 1.06 ?m have been performed in order to measure the mass-ablation rate ? and the ablation pressure Pa as a function of absorbed laser intensity Ia, laser wavelength ?L, and target atomic number Z in steady-state ablation dominated by nonlocalized inverse bremsstrahlung absorption. The results can be expressed as ?exp(kg/ sec cm2)?65 [Ia(W/cm2)/1013]5/9 ?-4/9L(?m)Z1/4 and Pa(Mbar)?2.5[Ia(W/ cm 2)/ 1013]7/9 ?-2/9L(?m)Z1/8. The measured results show good agreement with theory for nonlocalized absorption and with data of others.

Dahmani, Faiz

1992-06-01

47

Wavelength-scale stationary-wave integrated Fourier-transform spectrometry  

E-print Network

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 reflection (as in the principle of colour photography by Gabriel Lippmann) or counterpropagative interference phenomenon-is expected to be able to overcome this drawback. Here, we present a SWIFTS-based spectrometer relying on an original optical near-field detection method in which optical nanoprobes are used to sample directly the evanescent standing wave in the waveguide. Combined with integrated optics, we report a way of reducing the volume of the spectrometer to a few hundreds of cubic wavelengths. This is the first attempt...

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

2007-01-01

48

Wavelength-scale stationary-wave integrated Fourier-transform spectrometry  

NASA Astrophysics Data System (ADS)

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 reflection (as in the principle of colour photography by Gabriel Lippmann) or counterpropagative interference phenomenon-is expected to be able to overcome this drawback. Here, we present a SWIFTS-based spectrometer relying on an original optical near-field detection method in which optical nanoprobes are used to sample directly the evanescent standing wave in the waveguide. Combined with integrated optics, we report a way of reducing the volume of the spectrometer to a few hundreds of cubic wavelengths. This is the first attempt, using SWIFTS, to produce a very small integrated one-dimensional spectrometer suitable for applications where microspectrometers are essential.

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

2007-08-01

49

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

50

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

51

Anisotropy measurements of the cosmic-background radiation at 3-mm wavelength and an angular scale of 30 arcminutes  

SciTech Connect

This dissertation is concerned with measurements of the anisotropy in the Cosmic Background Radiation, at 3mm wavelength, on angular scales from 5 arcminutes to 1 degree. The data give an upper limit at 95% confidence to fluctuations in the Cosmic Background Radiation of {Delta}T/T < 3.0 {times} 10{sup {minus}5} for Gaussian autocorrelation functions with dispersions from 20 to 30 arcminutes, and weaker limits on smaller and larger scales. In addition, measurements of the galactic plane show unexpectedly high emission at 3mm, inconsistent with the previously accepted single-component galactic dust model with a scaling index of 2. These measurements were carried out with a 1 meter off-axis telescope designed for operation from a stratospheric helium-filled balloon, but also used on the ground from the South Pole. The detector is a superconducting mixer with a sensitivity of 1.7 mK/{radical}Hz (before chopping), and telescope pointing performance is demonstrated to be better than 1 arcminute in both azimuth and elevation. The development of the instrument is described, and details of the optical system, detector, and servo system are given. Discussions of the performance of the various subsystems, along with the limitations of the instrument are included.

Meinhold, P.R.

1990-01-01

52

High resolution CASSINI VIMS mosaics of Titan and the icy satellites of Saturn  

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 of 0.3 and 5.1 microns, generating image cubes in which each pixel represents a spectrum consisting of 352 contiguous wavebands. VIMS consists of two separate optical

R. Jaumann; K. Stephan; T. Roatsch; F. Scholten; K. Matz; R. H. Brown

2005-01-01

53

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

54

Near ultraviolet visible infrared mapping spectrometer (NU-VIMS)  

NASA Astrophysics Data System (ADS)

The NU-VIMS is a new instrument concept for high resolution spectral imaging within the spectral band of 0.25 to 5.0 micrometers . The concept utilizes state-of-the-art detector and grating technologies to extend the capabilities of the Cassini/VIMS-V prototype while maintaining its compact and lightweight format. The NU-VIMS optical design achieves remarkable performance while relying only on spherical surfaces in a single optical channel with only one grating and either one or two detector arrays. Though the concept was developed in anticipation of the MORO, Rosetta, and Pluto-Charon deep space missions, the instrument could also be mounted on a lightweight satellite for low cost remote sensing of the earth.

Reininger, Francis M.

1994-09-01

55

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

56

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

57

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

Microsoft Academic Search

Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as “brown” and “blue” in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3?m). In such composites bluer materials exhibit higher reflectance at 1.3?m and lower at

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

2007-01-01

58

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

59

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

60

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

61

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

62

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

63

Saturn's F Ring In Vims Observations Of A Cassini Ring-plane Crossing  

NASA Astrophysics Data System (ADS)

During a ring-plane crossing (RPX), Saturn's rings are viewed edge-on. As a result, the front of the F ring obscures the main rings--and the back of the back of the F ring is obscured by the main rings of Saturn--to varying degrees as the geometry of the observation changes. RPX observations therefore provide a chance to probe the vertical structure of the F ring. We present Visual and Infrared Mapping Spectrometer (VIMS) data from a 1-2 December 2005 ring-plane crossing by the Cassini Spacecraft. This dataset includes 150 VIMS QUBs of one ansa of the ring. Each QUB includes an image of 12 by 64 pixels at each of 352 wavelengths from 0.35 to 5.1 microns. The QUBs were taken at intervals of less than 10 minutes as Cassini passed from the north (unlit) side of the rings to the south (sunlit) side (solar B=-19.5°) with spacecraft ring-opening angles of 0.016° to -0.014°. The images closest to RPX have ring-opening angles of 0.0000067°. The size of one pixel on the rings is 1000 km, so the rings are vertically unresolved. The unprecedented temporal resolution in this dataset allows us to observe a sudden brightening of the rings just before RPX, which is caused by the back of the F ring emerging from behind the main rings. Another feature in the lightcurve is due to a cluster of four clumps orbiting in the F ring. We present spectroscopy of the ring system and its variation with position in the rings and with time. We interpret the spectra in terms of differing contributions from the main rings and the F ring. This research is supported by the Mead Witter Foundation.

Scharringhausen, Britt; Storck-Post, S. B.; Rehnberg, M. E.; Sans, S. A.; Wolfe, S. M.

2010-10-01

64

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

65

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

VIM-D salvage chemotherapy in Hodgkin's disease  

Microsoft Academic Search

A total of 15 patients with relapsed or resistant Hodgkin's disease were treated with a combination of etoposide (VP16), ifosfamide, mitozantrone and dexamethasone (VIM-D). The regime was well tolerated, the only major toxicity being myelosuppression. Complete remissions (CRs) were obtained in 4 patients and were maintained for 2,4, 10 and 14 months, 10 subjects subsequently received an autologous bone marrow

Julia K. Phillips; Ruth L. Spearing; John M. Davies; Charles R. M. Hay; Huw Parry; John R. Nash

1990-01-01

67

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

E-print Network

Virginia Wetlands Report Center for Coastal Resources Management www.ccrm.vims.edu Volume 26, Issue things, requires VIMS to provide Comprehensive Coastal Resource Management Plans (CCRMP) for each the following components: 1. Best Management Practices (BMPs) for Erosion Control 2. Local Inventory Data

68

Lessons learned from applying VIM to fast reactor critical experiments, summary  

SciTech Connect

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

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

1995-05-17

69

Experimental scaling laws for ablation parameters in plane target-laser interaction with 1.06 µm and 0.35 µm laser wavelengths  

NASA Astrophysics Data System (ADS)

Ablation parameters such as velocity, mass, momentum, pressure, and hydrodynamic efficiency have been investigated with plane targets irradiated in the range 3×1011-1015 W cm-2 with 1 nsec pulses and laser wavelengths of 1.06 ?m and 0.35 ?m. We show that ablation velocity, ablated mass, and momentum are in good agreement with ablation scaling laws deduced from analytical models taking into account inverse bremsstrahlung absorption below the critical density. Nevertheless, processes such as lateral conduction, hot spot, and preheat effects make inaccurate the comparison between ablation pressures, mass ablation rates, or hydrodynamic efficiencies measured for different laser wavelengths. Laser illumination nonuniformities are transmitted to the target in terms of pressure variations. The harmful consequence of a reduced lateral energy flow in 0.35 ?m experiments can eclipse the increasing of ablation pressure and hydrodynamic efficiency.

Meyer, B.; Thiell, G.

1984-01-01

70

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

71

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

SciTech Connect

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

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

2013-09-20

72

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

73

Remote sensing applications in marine science programs at VIMS  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

74

Absorption loss influence on optical characteristics of multilayer distributed Bragg reflector: wavelength-scale analysis by the method of single expression  

NASA Astrophysics Data System (ADS)

Electrodynamical model of a classical distributed Bragg reflector (DBR) consisting of alternating quarter-wave layers of high and low permittivity is considered at the plane wave normal incidence. Reflective characteristics of DBR possessing absorption loss in constituting layers are analysed via correct wavelength-scale boundary problem solution by the method of single expression (MSE). Analysis of optical field and power flow density distributions within the lossy DBR structures explained the peculiarities of their reflective characteristics. Optimal configurations of lossless and lossy DBRs are revealed. Specific DBR structures possessing full transparency at definite number of layers are also analysed.

Baghdasaryan, H. V.; Knyazyan, T. M.; Baghdasaryan, T. H.; Witzigmann, B.; Roemer, F.

2010-12-01

75

Stellar occultation experiment with the CASSINI VIMS instrument  

NASA Astrophysics Data System (ADS)

The VIMS instrument (Visible and Infrared Mapping Spectrometer) will be flown in the late 1990s on the CASSINI mission to Saturn and its moons. VIMS is designed to generate two-dimensional multispectral images of planetary surfaces and their features in the visible and infrared spectra. Compared to earth-based instruments, the stellar occultation experiment will provide unprecedented thickness resolution and chemical composition of planetary atmospheres. It will also gather high SNR optical depth profiles and particle size distribution of the Saturnian rings. The stellar occultation mode ideally requires continuous data acquisition for periods of up to several hours as the instrument stares at a star. This presents a sizeable challenge to the instrument's operational mode: processes that normally occur during mirror retrace must be shifted to data acquisition cycles, thereby creating timing difficulties in the sequencing of these cycles. The presentation focuses on the analysis of the stellar occultation mode and presents solutions to the challenge of an uninterrupted data stream. Several options will be presented that minimize any possible degradation of the experiment's science content.

Walch, Marc; Juergens, Dave; Anthony, Steve; Nicholson, Philip D.

76

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

77

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

78

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

NASA Astrophysics Data System (ADS)

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

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

2006-06-01

79

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

80

Hard X-ray and Hot Electron Production from Intense Laser Irradiation of Wavelength-Scale Droplets  

Microsoft Academic Search

We have examined the production of hard x-rays from the irradiation of 1 mum diameter water droplets with a 35 fs laser at intensity up to 7 x 10^17 W\\/cm^2. We observe substantial x-ray production in the photon energy range above 100 keV and find that the implied hot electron temperatures from these micron scale targets is significantly higher than

T. Ditmire; S. Wilks; J. Zweiback; T. E. Cowan; T. D. Donnelly; M. Rust; I. Weiner; M. Allen; R. A. Smith

2000-01-01

81

Hard x-ray and hot electron production from intense laser irradiation of wavelength-scale particles  

Microsoft Academic Search

We have examined the production of hard x-rays from the irradiation of ?1 µm diameter water droplets with a 35 fs laser at an intensity of up to 7×1017 Wc m?2. We observe substantial x-ray production in the photon energy range above 100 keV and find that the implied hot electron temperatures from these micron- scale targets are significantly higher

T D Donnelly; M Rust; I Weiner; M Allen; R A Smith; C A Steinke; S Wilks; J Zweiback; T Ditmire

2001-01-01

82

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

E-print Network

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

Barnes, Jason W

83

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

84

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

E-print Network

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

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

2012-01-01

85

Emitted Power Of Jupiter Based On Cassini CIRS And VIMS Observations  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

86

NASA Wavelength  

NSDL National Science Digital Library

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

2014-04-07

87

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

88

Cloud structure of Jupiter’s troposphere from Cassini VIMS  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

89

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

90

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

91

Cassini-VIMS at Jupiter: Solar occultation measurements using Io  

USGS Publications Warehouse

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

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

2003-01-01

92

VIM1, a methylcytosine-binding protein required for centromeric heterochromatinization  

PubMed Central

Epigenetic regulation in eukaryotes is executed by a complex set of signaling interactions among small RNA species and chromatin marks, including histone modification and DNA methylation. We identified vim1 (VARIANT IN METHYLATION 1), an Arabidopsis mutation causing cytosine hypomethylation and decondensation of centromeres in interphase. VIM1 is a member of a small gene family, encoding proteins containing PHD, RING, and SRA (SET- and RING-associated) domains, which are found together in mammalian proteins implicated in regulation of chromatin modification, transcription, and the cell cycle. VIM1 is an unconventional methylcytosine-binding protein that interacts in vitro with 5mCpG- and 5mCpHpG-modified DNA (via its SRA domain), as well as recombinant histones (H2B, H3, H4, and HTR12) in plant extracts. VIM1 associates with methylated genomic loci in vivo and is enriched in chromocenters. Our findings suggest that VIM1 acts at the DNA methylation–histone interface to maintain centromeric heterochromatin. PMID:17242155

Woo, Hye Ryun; Pontes, Olga; Pikaard, Craig S.; Richards, Eric J.

2007-01-01

93

Comparison between Dione' and Helene' surfaces using Cassini VIMS  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

94

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

95

Wavelength Routing Networks Wavelength Routing Networks -1  

E-print Network

Pag. 1 Wavelength Routing Networks Wavelength Routing Networks - 1 Optical Networks: from fiber transmission to photonic switching Wavelength-Routing Networks Fabio Neri and Marco Mellia TLC Networks Group.neri@polito.it ­ tel. 011 564 4076 marco.mellia@polito.it ­ tel. 011 564 4173 Wavelength Routing Networks - 2

Mellia, Marco

96

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

E-print Network

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

97

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

E-print Network

Virginia Wetlands Report Center for Coastal Resources Management www.ccrm.vims.edu Volume 23, Issue for Coastal Resources Management at the Virginia Institute of Marine Science recently completed an on not aware of the many alternatives for reducing shoreline erosion. The best method for any particular

98

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

E-print Network

Virginia Wetlands Report Center for Coastal Resources Management www.ccrm.vims.edu Volume 25, Issue for Coastal Resources Management is developing a new suite of tools intended to help regulators and property of bank erosion, existence of an environmentally valuable forested buffer on the shoreline, bank height

99

ACCEPTED MANUSCRIPT Fold interaction and wavelength selection  

E-print Network

ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 1 Fold interaction and wavelength selection in 3D models with analytical and numerical methods. New multilayer-folding domains can be distinguished. Wavelength and growthrate scaling laws and domain-limit equations are derived. Wavelength in 2D and 3D numerical simulations

Kaus, Boris

100

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

101

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

102

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

103

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

USGS Publications Warehouse

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

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

2007-01-01

104

VIM-Based Dynamic Sparse Grid Approach to Partial Differential Equations  

PubMed Central

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

Mei, Shu-Li

2014-01-01

105

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

2012-12-01

106

Mapping Titan's Surface With Vims Data By A Customized Spectral Unmixing Method  

Microsoft Academic Search

To interpret the radiance factor (I\\/F) data from the Visible Infrared Mapping Spectrometer (VIMS) onboard Cassini, we focused on spectral analysis methodololgy and its applications to map the spectral properties of Titan's surface. It is possible to see Titan's surface through six main atmospheric spectral windows between 0.4 and 5.1 micrometers. Using data within only these windows, most of the

Jean-Philippe Combe; T. B. McCord; P. Hayne

2006-01-01

107

Solitary wave solutions of the improved KdV equation by VIM  

Microsoft Academic Search

The variational iteration method (VIM) is applied to solve numerically the improved Korteweg-de Vries equation (IKdV). A correction function is constructed with a general Lagrange multiplier that can be identified optimally via the variational theory. This technique provides a sequence of functions with easily computable components that converge rapidly to the exact solution of the IKdV equation. Propagation of single,

Saleh M. Hassan; Naif M. Alotaibi

2010-01-01

108

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

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

109

Method of Controlling Lasing Wavelength(s)  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

110

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

111

Physics of Very Short Wavelength Acceleration  

SciTech Connect

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. [University of Southern California, Los Angeles, CA 90089-0271 (United States)

2006-01-03

112

The two-micron spectral characteristics of the Titanian haze derived from Cassini/VIMS solar occultation spectra  

NASA Astrophysics Data System (ADS)

Vertically-resolved spectral characteristics of the Titanian haze in the 2-?m wavelength range were derived from solar occultation spectra measured by Cassini/VIMS on January 15, 2006. At the various altitudes probed by the solar occultation measurements, we reproduced the observed spectra using a radiative transfer program including absorption by CH4 ro-vibrational bands, collision-induced absorption by N2-N2 pairs, and H2-N2 dimers, as well as absorption and scattering by the haze particles. The retrieved optical depth spectra (or ?-spectra) for the haze show marked variations in the 2.1-2.8 ?m range, with peaks near 2.30 and 2.35 ?m, and the relative amplitude of these peaks changing with altitude. The gross spectral shape of the ?-spectra is found similar to the typical 2-?m absorption spectra of the alkane group of hydrocarbon (CnH2n+2) ices. The ?-spectra retrieved at 2 ?m and those previously retrieved at 3 ?m by Kim et al. (2011) are simultaneously reproduced by combinations of 2- and 3-?m absorbance spectra of alkane ices such as CH4, C2H6, C5H12, C6H14, with the addition of a nitrile ice, CH3CN. These combinations are neither unique nor limited and need more fine-tuning to fit the detailed features of the ?-spectra. There is a need for additional laboratory measurements of absorbance and indices of refraction for a wider variety of hydrocarbon and nitrile ices in the temperature range relevant to Titan.

Sim, Chae Kyung; Kim, Sang Joon; Courtin, Régis; Sohn, Mirim; Lee, Dong-Hun

2013-11-01

113

Dual Wavelength Lasers  

NASA Technical Reports Server (NTRS)

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

Walsh, Brian M.

2010-01-01

114

Prospective Observational Study of the Impact of VIM1 Metallo Lactamase on the Outcome of Patients with Klebsiella pneumoniae Bloodstream Infections  

Microsoft Academic Search

VIM-1-producing Klebsiella pneumoniae (VPKP) is an emerging pathogen. A prospective observational study was conducted to evaluate the importance of VIM production on outcome of patients with K. pneumoniae bloodstream infections (BSIs). Consecutive patients with K. pneumoniae BSIs were identified and followed up until patient discharge or death. A total of 162 patients were included in the analysis; 67 (41.4%) were

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

2009-01-01

115

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

E-print Network

Middle Suffix Spouses Name Home Phone Office Phone Cell Phone Home Mailing Address e-mail VIMS Mail@vims.edu Date Signature 3) Library, Watermen's Hall, 1st Floor, Carol Coughlin 684-7114, coughlin@vims.edu Date on use of Electronic Communications. Library To enable early registration for accessing on line services

Swaddle, John

116

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

SciTech Connect

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

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

2013-10-20

117

LETTER TO THE EDITOR: Hard x-ray and hot electron production from intense laser irradiation of wavelength-scale particles  

Microsoft Academic Search

We have examined the production of hard x-rays from the irradiation of ~1 µm diameter water droplets with a 35 fs laser at an intensity of up to 7×1017 W cm-2. We observe substantial x-ray production in the photon energy range above 100 keV and find that the implied hot electron temperatures from these micron-scale targets are significantly higher than

T. D. Donnelly; M. Rust; I. Weiner; M. Allen; R. A. Smith; C. A. Steinke; S. Wilks; J. Zweiback; T. E. Cowan; T. Ditmire

2001-01-01

118

Early signatures of large-scale field line opening. Multi-wavelength analysis of features connected with a "halo" CME event  

NASA Astrophysics Data System (ADS)

A fast "halo"-type coronal mass ejection (CME) associated with a two-ribbon flare, GOES class M 1.3, was observed on February 8, 2000. Soft X-ray and EUV images revealed several loop ejections and one wave-like moving front that started from a remote location, away from the flare core region. A radio type-II burst was observed near the trajectory of the moving soft X-ray front, although association with the CME itself cannot be ruled out. Large-scale dimmings were observed in EUV and soft X-rays, both in the form of disappearing transequatorial loops. We can pinpoint the time and the location of the first large-scale field-line opening by tracing the electron propagation paths above the active region and along the transequatorial loop system, in which large-scale mass depletion later took place. The immediate start of a type-IV burst (interpreted as an upward moving structure) which was located over a soft X-ray dimming region, confirms that the CME had lifted off. We compare these signatures with those of another halo CME event observed on May 2, 1998, and discuss the possible connections with the "magnetic breakout" model.

Pohjolainen, S.; Vilmer, N.; Khan, J. I.; Hillaris, A. E.

2005-04-01

119

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. PMID:22371893

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

2012-01-01

120

Calculated criticality for sup 235 U/graphite systems using the VIM Monte Carlo code  

SciTech Connect

Calculations for highly enriched uranium and graphite systems gained renewed interest recently for the new production modular high-temperature gas-cooled reactor (MHTGR). Experiments to validate the physics calculations for these systems are being prepared for the Transient Reactor Test Facility (TREAT) reactor at Argonne National Laboratory (ANL-West) and in the Compact Nuclear Power Source facility at Los Alamos National Laboratory. The continuous-energy Monte Carlo code VIM, or equivalently the MCNP code, can utilize fully detailed models of the MHTGR and serve as benchmarks for the approximate multigroup methods necessary in full reactor calculations. Validation of these codes and their associated nuclear data did not exist for highly enriched {sup 235}U/graphite systems. Experimental data, used in development of more approximate methods, dates back to the 1960s. The authors have selected two independent sets of experiments for calculation with the VIM code. The carbon-to-uranium (C/U) ratios encompass the range of 2,000, representative of the new production MHTGR, to the ratio of 10,000 in the fuel of TREAT. Calculations used the ENDF/B-V data.

Collins, P.J.; Grasseschi, G.L.; Olsen, D.N. (Argonne National Lab.-West, Idaho Falls (United States)); Finck, P.J. (Argonne National Lab., IL (United States))

1992-01-01

121

The measurement of wavelength in space plasmas  

NASA Technical Reports Server (NTRS)

A plasma wave can be described by its frequency and wave vector, while a nonlinear plasma structure such as a solitary wave can be described by its temporal signature and scale size. Time series or frequency measurements are relatively easy to perform from spacecraft, but wavelength or scale size measurements are difficult. Nevertheless, direct measurements of wavelength have contributed to understanding plasma waves and fluctuations; for example, such measurements have established the widespread existence of spatial irregularities in the magnetosphere, determined the characteristics of waves upstream of the earth's bow shock, and allowed the size and motion of double-layer-like structures along auroral field lines to be inferred. This paper reviews progress in making measurements of wavelength and scale sizes. The different techniques for inferring wavelength are described, and then a series of case studies is considered to demonstrate applications.

Labelle, J.; Kintner, P. M.

1989-01-01

122

Wavelength independent interferometer  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

123

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

PubMed

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

Favaro, Marco; Sarti, Mario; Fontana, Carla

2014-11-01

124

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

PubMed

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

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

2014-11-01

125

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

PubMed

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

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

2014-10-01

126

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

USGS Publications Warehouse

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

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

2006-01-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

128

Emergence of VIM-2 and IMP-15 carbapenemases and inactivation of oprD gene in carbapenem-resistant Pseudomonas aeruginosa clinical isolates from Lebanon.  

PubMed

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

Al Bayssari, Charbel; Diene, Seydina M; Loucif, Lotfi; Gupta, Sushim Kumar; Dabboussi, Fouad; Mallat, Hassan; Hamze, Monzer; Rolain, Jean-Marc

2014-08-01

129

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

PubMed Central

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

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

2010-01-01

130

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

131

Saturn's Regional and Global Cloud Properties from Cassini/VIMS 4.5-5.1 Micron Spectroscopy  

NASA Astrophysics Data System (ADS)

Exploiting a region of Saturn's thermal-IR spectrum between 4.5-5.1 microns where there is a dearth of opacity sources, Cassini/VIMS has revealed a wealth of dynamical phenomena in the 1-4 bar region that are transforming our understanding of the gas giant. Narrow dark lanes and discrete cloud features are observed in silhouette against the 5-micron background thermal glow of Saturn's deep atmosphere. The NEMESIS optimal-estimation retrieval algorithm (Irwin et al., JSQRT, 2008) is used to model the 4.5-5.1 micron region using the correlated-k approximation. We determine (a) the sensitivity and correlations associated with determinations of cloud properties and gaseous composition from the Cassini/VIMS dataset; (b) the meridional variation in opacity sources (a multi-layer cloud model, the abundances of phosphine and arsine); (c) the contribution of the thermal and reflected components to VIMS spectra and (d) the spatial variability of opacity sources associated with Saturn's string of pearls and ribbon wave features in the northern hemisphere. The meridional gradients in composition are compared to the Cassini/CIRS derivations of phosphine at higher altitudes (pressures less than 1 bar; Fletcher et al., Icarus, 2009). The seasonal origin of the north-south asymmetry in 5-micron opacity (Baines et al., BAAS, 2006) and the dynamical motions associated with Saturn's complex zonal wave activity will be discussed. The vertical distribution of cloud opacity demonstrates the necessity for aerosols at the 2-3 bar level to successfully replicate the VIMS data. Finally, we search Cassini/CIRS mapping observations at 15.0 cm-1 resolution for mid-IR counterparts (0.1-0.5 bar) to the zonal wave activity in the deeper troposphere (1-4 bars) to investigate the vertical coupling in Saturn's troposphere.

Fletcher, Leigh N.; Baines, K. H.; Momary, T. W.; Orton, G. S.; Roos-Serote, M.; Irwin, P. G. J.

2009-09-01

132

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

PubMed Central

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

M, Jeya

2014-01-01

133

Wavelength and Energy  

NSDL National Science Digital Library

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

134

Long wavelength infrared detector  

NASA Technical Reports Server (NTRS)

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

Vasquez, Richard P. (inventor)

1993-01-01

135

Multi-wavelength Sun  

NASA Technical Reports Server (NTRS)

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

2007-01-01

136

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

USGS Publications Warehouse

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

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

2011-01-01

137

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

138

Wavelength swept ASE source  

NASA Astrophysics Data System (ADS)

We present a novel wavelength swept light source for Optical Coherence Tomography (OCT). Arbitrary sweep rates up to 2x170kHz are achieved by phase-shifted control of two optical bandpass-filters to compensate light propagation effects.

Eigenwillig, Christoph M.; Biedermann, Benjamin R.; Wieser, Wolfgang; Huber, Robert

2009-07-01

139

Long wavelength semiconductor lasers  

Microsoft Academic Search

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

G. P. Agrawal; N. K. Dutta

1986-01-01

140

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

141

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

142

Scales  

ScienceCinema

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

Murray Gibson

2010-01-08

143

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

E-print Network

In the last few years Cassini-VIMS, the Visible and Infared Mapping Spectrometer, returned to us a comprehensive view of the Saturn's icy satellites and rings. After having analyzed the satellites' spectral properties (Filacchione et al. (2007a)) and their distribution across the satellites' hemispheres (Filacchione et al. (2010)), we proceed in this paper to investigate the radial variability of icy satellites (principal and minor) and main rings average spectral properties. This analysis is done by using 2,264 disk-integrated observations of the satellites and a 12x700 pixels-wide rings radial mosaic acquired with a spatial resolution of about 125 km/pixel. The comparative analysis of these data allows us to retrieve the amount of both water ice and red contaminant materials distributed across Saturn's system and the typical surface regolith grain sizes. These measurements highlight very striking differences in the population here analyzed, which vary from the almost uncontaminated and water ice-rich surfac...

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

2012-01-01

144

Accumulation of carbapenem resistance mechanisms in VIM-2-producing Pseudomonas aeruginosa under selective pressure.  

PubMed

Pseudomonas aeruginosa has the potential to achieve resistance to carbapenems via the acquisition of carbapenemase-encoding genes, the downregulation of the OprD porin, the overexpression of efflux systems and the overproduction of cephalosporinases. One hundred and fifty carbapenem-non-susceptible isolates from 2008 to 2010 were screened for carbapenemase production, OprD porin loss, efflux pumps overexpression and inducible AmpC beta-lactamase production. For comparison reasons, the presence of the same mechanisms was also assessed in a previous collection of 30 carbapenem-non-susceptible P. aeruginosa isolated between 2003 and 2005. Results showed the accumulation of various resistance mechanisms among VIM-2 producers isolated between 2008 and 2010 with a parallel considerable increase in imipenem MIC90 and the geometric mean of the MIC values of imipenem and meropenem between the two study groups. The accumulation of carbapenem resistance mechanisms highlights the potential of this formidable pathogen for evolutionary success under antibiotic selective pressure. PMID:24062236

Meletis, G; Vavatsi, N; Exindari, M; Protonotariou, E; Sianou, E; Haitoglou, C; Sofianou, D; Pournaras, S; Diza, E

2014-02-01

145

Triple wavelength monitor PDIC  

NASA Astrophysics Data System (ADS)

Recently the demand for high-capacity optical storage systems compatible with CD, DVD, and Blue is growing. We designed the Vertical NIP photodiode with a diameter of 700um and the trans-impedance circuits by using 0.6um BiCMOS process. The measured sensitivity of the photodiode is 0.25, 0.42, and 0.48A/W for 405, 650, and 780nm wavelength lights, respectively. The capacitance of the PD is 4.5pF. Monitor PDIC for detecting triple wavelength lights is presented in this paper. The complete monitor PDIC with the NIP photodiode of 700um in diameter occupies 1900um*1200um. -3dB bandwidth is 110MHz and the temperature drift of output voltage is 3.2%.

Park, Deukhee; Ha, Chang-woo; Shin, Sang-cheol; Kwon, Kyoung-soo; Ko, Joo-yul; Kang, Shin-jae

2006-08-01

146

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

147

Connectivity and Sparse Wavelength Conversion in Wavelength-Routing Networks  

Microsoft Academic Search

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

Suresh Subramaniam; Murat Azizoglu; Arun K. Somani

1996-01-01

148

Wavelength requirements in arbitrarily connected wavelength-routed optical networks  

Microsoft Academic Search

Wavelength division multiplexed optical networks using wavelength routing (WRONs) represent the most promising solution for future high-capacity wide-area network applications. One of the crucial factors which will determine their feasibility is the number of wavelengths required to satisfy the network traffic demand. In this paper, we consider arbitrarily connected networks as physical topologies for WRONs. By analysing a large number

Stefano Baroni; Polina Bayvel

1997-01-01

149

52 LINCOLN LABORATORY JOURNAL n VOLUME 20, NUMBER 2, 2014 Wavelength Beam  

E-print Network

52 LINCOLN LABORATORY JOURNAL n VOLUME 20, NUMBER 2, 2014 Wavelength Beam Combining for Power today is a well-accepted avenue for laser power scaling. Wavelength beam combining allows for scaling Laboratory has demonstrated a wavelength-beam-combining technique that significantly improves the brightness

Reif, Rafael

150

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

151

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

PubMed

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

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

2014-01-01

152

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

PubMed

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

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

2013-09-01

153

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

154

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

PubMed

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

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

2013-08-01

155

Wavelength meter having elliptical wedge  

DOEpatents

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

Hackel, R.P.; Feldman, M.

1992-12-01

156

A Heuristic Wavelength Assignment Algorithm for Multihop WDM Networks with Wavelength Routing and Wavelength Reuse  

Microsoft Academic Search

The authors present a heuristic algorithm for effectively assigning a limited number of wavelengths among the access stations of a multihop network wherein the physical medium consists of optical fiber segments which interconnect wavelength-selective optical switches. Such a physical medium permits the limited number of wavelengths to be re-used among the various fiber links, thereby offering very high aggregate capacity.

Zhensheng Zhang; Anthony S. Acampora

1994-01-01

157

Wavelength tunable diode laser  

SciTech Connect

This patent describes an apparatus for generating a variable wavelength output optical signal. It comprises signal generation means for generating the output optical signal; reflective feedback means sharing a common optical axis with the signal generation means, for receiving a portion of the output optical signal and for receiving an electrical tuning signal, the reflective feedback means comprising: an optical waveguide formed of electro-optically active material; a dielectric layer forming a surface on top of the waveguide and having a corrugated grating topology along a face parallel to the optical axis of the waveguide, wherein striations of the grating are transverse to the optical axis; tuning means, comprising first and second electrodes disposed on opposite sides of the waveguide for inducing, in response to the electrical tuning signal, an electrical field through the waveguide transverse to the optical axis.

Bradley, E.M.

1991-06-04

158

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

159

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

Microsoft Academic Search

A wide variety of cloud structures - comprised, putatively, of ammonia and ammonia hydrosulfide , but perhaps with an admixture of water - has been characterized by Cassini\\/VIMS, including dozens of axisymmetric zonal features, planetary waves, classic vortex structures at both the north and south poles, and a hexagonal slow-speed wave feature centered on the north pole. At depth, the

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

2008-01-01

160

Metallo--Lactamase Detection: Comparative Evaluation of Double-Disk Synergy versus Combined Disk Tests for IMP, GIM, SIM, SPM, or VIM-Producing Isolates  

Microsoft Academic Search

The emergence of metallo--lactamase (MBL)-producing isolates is a challenge to routine microbiology laboratories, since there are no standardized methods for detecting such isolates. The aim of this study was to evaluate the accuracy of different phenotypic methods to detect MBL production among Pseudomonas spp., Acinetobacter spp., and enterobacterial isolates, including GIM, IMP, SIM, SPM, and VIM variants. A total of

Renata C. Picao; Soraya S. Andrade; Adriana Gianinni Nicoletti; Eloiza H. Campana; Gabriela C. Moraes; Rodrigo E. Mendes; Ana C. Gales

161

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

E-print Network

, likely composed of a thick and liquid-saturated coating of photon-absorbing materials in the infrared, ISS and RADAR data and comparison with the Etosha Pan (Namibia) T. Corneta,1 , O. Bourgeoisa , S. Le (ISS) in 2004 and 2005, Visual and Infrared Mapping Spectrometer (VIMS) in 2007 and 2009 and RADAR

Brest, Université de

162

NASA Wavelength Digital Library  

NSDL National Science Digital Library

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

163

Reflectance standards at ultraviolet wavelengths  

NASA Astrophysics Data System (ADS)

Polytetrafluoroethylene (PTFE) is widely used in remote sensing applications requiring a diffuse reflectance standard for detector calibration. The bi-directional and directional-hemispherical reflectance properties of both pressed and sintered PTFE were measured at ultraviolet wavelengths to provide information for their use as standards in this spectral range. The reflectance decreases with decreasing wavelength for both geometries, and the ratio between the reflectances for these geometries remains constant for wavelengths from 300 nm to 400 nm.

Barnes, P. Yvonne; Nadal, Maria E.; Early, Edward A.

1999-09-01

164

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

165

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

PubMed Central

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

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

2013-01-01

166

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

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

167

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

168

Monoclonal Outbreak of VIM-1-Carbapenemase-Producing Enterobacter cloacae in Intensive Care Unit, University Hospital Centre Split, Croatia.  

PubMed

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

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

2014-10-01

169

Multiple-wavelength tunable laser  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

170

neighboring wavelength will lase, therefore a discretely tunable dual-wavelength laser is obtained. Thirteen pairs of wavelength  

E-print Network

neighboring wavelength will lase, therefore a discretely tunable dual-wavelength laser is obtained. Thirteen pairs of wavelength lasing within the same wavelength range are shown in Figure 5(b). The output between the dual wavelengths is 1 dB, while the SOA driving current works at 85 mA. The optical signal

Myung, Noh-Hoon

171

Wavelength selector for tunable laser  

SciTech Connect

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

Shoshan, I.

1980-10-21

172

Towards short wavelengths FELs workshop  

SciTech Connect

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

Ben-Zvi, I.; Winick, H.

1993-12-01

173

Modulating short wavelength fluorescence with long wavelength light.  

PubMed

Two molecules in which the intensity of shorter-wavelength fluorescence from a strong fluorophore is modulated by longer-wavelength irradiation of an attached merocyanine-spirooxazine reverse photochromic moiety have been synthesized and studied. This unusual fluorescence behavior is the result of quenching of fluorophore fluorescence by the thermally stable, open, zwitterionic form of the spirooxazine, whereas the photogenerated closed, spirocyclic form has no effect on the fluorophore excited state. The population ratio of the closed and open forms of the spirooxazine is controlled by the intensity of the longer-wavelength modulated light. Both square wave and sine wave modulation were investigated. Because the merocyanine-spirooxazine is an unusual reverse photochrome with a thermally stable long-wavelength absorbing form and a short-wavelength absorbing photogenerated isomer with a very short lifetime, this phenomenon does not require irradiation of the molecules with potentially damaging ultraviolet light, and rapid modulation of fluorescence is possible. Molecules demonstrating these properties may be useful in fluorescent probes, as their use can discriminate between probe fluorescence and various types of adventitious "autofluorescence" from other molecules in the system being studied. PMID:25072525

Copley, Graeme; Gillmore, Jason G; Crisman, Jeffrey; Kodis, Gerdenis; Gray, Christopher L; Cherry, Brian R; Sherman, Benjamin D; Liddell, Paul A; Paquette, Michelle M; Kelbauskas, Laimonas; Frank, Natia L; Moore, Ana L; Moore, Thomas A; Gust, Devens

2014-08-27

174

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

PubMed

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

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

2014-11-01

175

Rituximab improves the treatment results of DHAP-VIM-DHAP and ASCT in relapsed\\/progressive aggressive CD20+ NHL: A prospective randomized HOVON trial  

Microsoft Academic Search

We evaluated the role of rituximab during remission induction chemotherapy in relapsed aggressive CD20+non-Hodgkin lymphoma. Of 239 patients, 225 were evaluable for analysis. Randomized to DHAP (cisplatin-cytarabine- dexamethasone)-VIM (etoposide-ifosfamide-methotrexate)-DHAP (cisplatin- cytarabine-dexamethasone) chemotherapy with rituximab (R; R-DHAP arm) were 119 patients (113 evaluable) and to chemotherapy without rituximab (DHAP arm) 120 patients (112 evaluable). Patients in complete remission (CR) and partial

E. Vellenga; Putten van W. L. J; Veer van't M. B; J. M. Zijlstra; W. E. Fibbe; Oers van M. H. J; L. F. Verdonck; P. W. Wijermans; G. W. van Imhoff; P. J. Lugtenburg; P. C. Huijgens

2008-01-01

176

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

177

Compact wavelength division multiplexers and demultiplexers  

E-print Network

Compact wavelength division multiplexers and demultiplexers Revital Shechter, Yaakov Amitai, and Asher A. Friesem Compact devices for wavelength division multiplexing and demultiplexing, believed, including the fact that the recording is done at a single wavelength in the green region. Experimental

Friesem, Asher A.

178

Significance of dual polarized long wavelength radar for terrain analysis  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

180

Crosstalk aware wavelength assignment in static wavelength routing  

Microsoft Academic Search

The transparent WDM optical networks in absence of electrical regenerators reduce the overall network cost. The Quality of Service (QoS) in such networks can be guaranteed if and only if the Bit Error Rate (BER) and the crosstalk induced power penalty is significantly reduced. In this paper we have studied the wavelength assignment mechanism based on BER blocking probability and

Suvarna S. Patil; Bharat S. Chaudhari

2010-01-01

181

Lunar polarization studies at 3.1 mm wavelength  

NASA Technical Reports Server (NTRS)

Observations of the distribution of linearly polarized lunar thermal emission were made at a wavelength of 3.1 mm with The University of Texas 4.88 m parabolic reflector (0.042 deg HPBW). A shadow corrected, rough surface, thermal emission model for a homogeneous moon was least-squares-fitted to the polarization data. Results indicate an effective lunar dielectric constant of 1.34 plus or minus 0.04 with surface roughness characterized by a standard deviation of 17 (plus or minus 5) deg for surface slopes with a normal probability density, independent of lunar phase. A comparison of these results with published values at other wavelengths suggests that the effective lunar dielectric constant, as obtained by lunar emission measurements, decreases with decreasing wavelength of observation. This wavelength dependence may be interpreted in terms of an inhomogeneous surface and/or a surface that possesses intermediate scale surface roughness.

White, T. L.; Cogdell, J. R.

1973-01-01

182

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

183

Long wavelength vertical-cavity light-emitting devices  

NASA Astrophysics Data System (ADS)

Long wavelength tunable transmitters are essential in the field of optical communications. Wavelength control and cost reduction are very important issues, especially in applications such as wavelength division multiplexing (WDM) networks, where several closely spaced wavelengths are transmitted and processed simultaneously. This thesis introduces a transmitter design that can alleviate these problems. This work involves the development, fabrication, and characterization of a narrowband tunable resonant cavity light-emitting diode (LED). The emission is centered at 1.51 mum, an important wavelength for optical communications. The linewidth is only 4 nm and the tuning range covers 75 nm. Wafer bonding and surface micromachining techniques have been integrated in the design to produce a structure that combines the assets of each technology. Wafer bonding is used to build the base for a vertical cavity surface emitting laser (VCSEL) structure, which is composed of an InP-based active layer on a GaAs-based mirror. Surface micromachining is then used to fabricate the suspended top mirror of the VCSEL, in place of the traditional top mirror that is grown directly on the VCSEL structure. The suspended mirror moves towards the substrate with the application of a voltage, thus changing the Fabry-Perot cavity length and providing the wavelength tunability of the device. This transmitter design relaxes the need for preset wavelengths in VCSEL processing by allowing the user to adjust the central wavelength after processing. Arrays of transmitters with identical wavelengths for high power applications or with gradually decreasing emission wavelengths across a wafer can also be achieved. The tunability of the devices allows for real time wavelength monitoring and tracking to ensure stability of the wavelengths with temperature or environmental changes, as well as compensating for shifts in wavelength due to degradation of the devices over time. Due to the monolithic, vertical cavity design, the device has important applications in spectroscopy and optical information processing as well. In addition, the planar processing of the devices makes possible wafer scale fabrication and testing which allows for low cost production, an essential component of manufactured products.

Christenson, Gina Lee

184

Wavelength-modulated photocapacitance spectroscopy  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

185

Wavelength discrimination in the goldfish  

Microsoft Academic Search

Summary Wavelength discrimination was measured in three goldfish using a behavioral training technique. The?? function has three minima which indicate spectral ranges of high discrimination ability: at 410–420 nm, at 500 nm and at 600–610 nm (Fig. 5). The best discrimination of all was found at 500 nm:?? as low as 4 nm. Model computations were performed to find out

Christa Neumeyer; J. Gutenberg-UniversitM

1986-01-01

186

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

187

Laser wavelength selector and output coupler  

NASA Technical Reports Server (NTRS)

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

Hard, T. M.

1970-01-01

188

Short Wavelength Modes 5.1 Introduction  

E-print Network

Chapter 5 Short Wavelength Modes 5.1 Introduction In short wavelength regime (ki) 2 > 1 (cross field wavelength smaller than the ion Larmor radius), the toroidal ITG mode tends to be stabilized is the ion factor. In deuterium plasma with i = 1%, the ratio is approximately 4.3. As the wavelength

Saskatchewan, University of

189

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

190

ccsd00001970, E ects of Laser Wavelength and Density Scalelength  

E-print Network

spectra in the course of interaction between intense laser pulse and overdense plasmas are reexamined from plasma interactions on the laser wavelength was not investigated in a 0 #21; 1. Recently, the laser-in-cell simulation is scaled by I rather than I#21; 2 at the interaction with overdense plasmas with #12;xed ions

191

Millimeter-submillimeter wavelength filter system  

NASA Astrophysics Data System (ADS)

We describe the design, fabrication, measurement, and performance of a set of cryogenic millimetersubmillimeter wavelength filters used in a balloonborne bolometric radiometer. The set contains single resonant mesh grids used as dichroic beam splitters, resonant meshes in a double quarter-wave configuration, a commercial inductive grid filter, and high-frequency blocking filters. The resultant system has passbands at ? = 1.73, 1.05, 0.61, 0.44 mm with ??/? = 0.23, 0.23, 0.12, 0.06. Limits on high-frequency leakage are deduced from laboratory measurements and from the analysis of flight data. The filter set response to three different sources of radiation is presented to show the method and limitations of our characterization. The key element of the filter system is a resonant periodic array of cross-shaped holes etched in thin aluminum. We give an empirical scaling law for the resonant wavelength as a function of structure parameters for aluminum on 25-?m-thick Mylar. Plots of the transmittance for normally incident radiation and the transmittance and reflectance for a 45° incident radiation are presented.

Page, Lyman A.; Cheng, Edward S.; Golubovic, Boris; Meyer, Stephan S.; Gundersen, Joshua

1994-01-01

192

Review of short wavelength lasers  

SciTech Connect

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

Hagelstein, P.L.

1985-03-18

193

Short wavelength magnetic buoyancy instability  

E-print Network

Magnetic buoyancy instability plays an important role in the evolution of astrophysical magnetic fields. Here we revisit the problem introduced by \\citet{Gilman_1970} of the short wavelength linear stability of a plane layer of compressible isothermal fluid permeated by a horizontal magnetic field of strength decreasing with height. Dissipation of momentum and magnetic field is neglected. By the use of a Rayleigh-Schr\\"odinger perturbation analysis, we explain in detail the limit in which the transverse horizontal wavenumber of the perturbation, denoted by $k$, is large (i.e.\\ short horizontal wavelength) and show that the fastest growing perturbations become localized in the vertical direction as $k$ is increased. The growth rates are determined by a function of the vertical coordinate $z$ since, in the large $k$ limit, the eigenmodes are strongly localized in the vertical direction. We consider in detail the case of two-dimensional perturbations varying in the directions perpendicular to the magnetic field,...

Mizerski, K A; Hughes, D W

2013-01-01

194

Quantum detection at millimeter wavelengths  

Microsoft Academic Search

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

John Tucker; Marc Feldman

1985-01-01

195

Mimas at Many Wavelengths and Many Angles  

NASA Astrophysics Data System (ADS)

Discovered by William Herschel during a Saturn ring plane crossing in 1789, Mimas is exceedingly difficult to observe from Earth due to scattered light from Saturn. It is also difficult to plan a targeted flyby with a spacecraft; it was the only major satellite not to have a close encounter by the Cassini spacecraft. Observations of the moon during ring plane crossings established that it was more reflective than any of the icy satellites of Saturn, except Enceladus, and that it exhibited only small albedo variegations (Buratti et al. 1998, Icarus 136, 223). According to models of the dynamics of the E-ring of Saturn (Hamilton and Burns, 1994, Science 264, 550) the trailing side of Mimas should contain accreted particles from that ring. New observations at opposition obtained by the Cassini Visual Infrared Mapping Spectrometer (VIMS) instrument between 0.4 and 5.2 microns show the moon has a surge similar to that seen on other icy bodies, increasing in brightness by over 30% in the last five degrees. During the closest nontargeted flyby by Cassini on February 13, 2010, when the Cassini spacecraft approached within 9500 km of Mimas, maps of the moon were obtained by the Visual Infrared Mapping Spectrometer (VIMS) between 0.4 and 5.0 microns. The only component identified so far on the surface is water ice. Unlike several of the other icy satellites, carbon dioxide and organics do not seem to be present. The 130-km crater Herschel shows significant differences in particle sizes when compared to the surrounding terrain. Ultraviolet maps of the satellite obtained by the Imaging Science Subsystem (ISS) suggest the accretion of E-ring particles on the trailing side, as predicted by Hamilton and Burns. Analysis of the depths of water ice absorption bands is also consistent with this scenario. Funded by NASA.

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

2010-12-01

196

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

197

Submillimeter-wavelength space-based imaging radar. Interim report  

SciTech Connect

This report considers the use of a submillimeter wavelength space-based imaging radar. The main application envisioned is midcourse decoy discrimination for strategic defense, for which it would have the capability of producing a series of images, in real time, at strategic ranges, with less than meter-scale resolution and with modest power requirements. Undoubtedly, there are other applications. The requirements for a SAR and ISAR imaging radar at submillimeter wavelength are determined, and the prospect for the development of rf sources to power the radar is examined.

Manheimer, W.M.

1988-05-31

198

VIM and IMP metallo-?-lactamases and other extended-spectrum ?-lactamases in Escherichia coli and Klebsiella pneumoniae from environmental samples in a Tunisian hospital.  

PubMed

An extremely drug-resistant Enterobacteriaceae species emerged in Kasserine Hospital, Tunisia between 2009 and 2010 causing a local outbreak. We aimed to characterize extended-spectrum ?-lactamase (ESBL) and metallo-?-lactamase (MBL)-producing Enterobacteriaceae from the hospital environment. Swabs were collected from ten different wards from Kasserine Hospital, Tunisia. A total of 46 isolates were cultured onto MacConkey agar supplemented with ceftazidime to select for ESBL-producing Enterobacteriaceae. Identification and susceptibility patterns were performed using Phoenix-automated phenotypic identification criteria. Extended spectrum ?-lactamases (ESBLs) were detected using cefepime ESBL E-test. Colony blotting was first used to detect the occurrence of bla(SHV) , bla(CTX-M) , bla(CMY) , bla(IMP) , and bla(VIM) genes. PCR was used to amplify these genes, and the amplicons were sequenced and analyzed. Total DNA was digested with XbaI, and PFGE was used to type the major isolates that produced IMP-1. Among the 46 isolates, 63% were Klebsiella pneumoniae, 13% were Escherichia coli, 8.7% were Proteus mirabilis, 6% were Enterobacter cloaceae, 4.3% were Providencia rettgeri, 2.5% were Serratia marcescens, and 2.5% were Pantoea agglomerans. PCR amplification and DNA sequencing showed that hospital environment isolates produced SHV-125, CTX-M-15, CMY-2 ESBLs, and IMP-1 and VIM-2 MBLs. PFGE typing showed the emergence of IMP-1 MBL-producing K. pneumoniae isolates that were not clonal. In this study, we report the first characterization of IMP-1 and VIM-2 MBL-producing K. pneumoniae and E. coli isolates collected from Kasserine Hospital, Tunisia. PMID:21917010

Chouchani, Chedly; Marrakchi, Rim; Ferchichi, Leila; El Salabi, Allaaeddin; Walsh, Timothy R

2011-10-01

199

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

200

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. PMID:23056278

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

2012-01-01

201

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

202

BIN Diode For Submillimeter Wavelengths  

NASA Technical Reports Server (NTRS)

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

Maserjian, J.

1989-01-01

203

Dual wavelength holographic interferometry system  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

204

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

E-print Network

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

Mueser, Martin

205

Wavelength allocation algorithms for optical packet switch under limited wavelength conversion  

NASA Astrophysics Data System (ADS)

In an optical packet switch, wavelength allocation algorithm has to be considered when wavelength resources are shared among all optical packets. This paper addresses the wavelength allocation algorithms for optical packet switch with limited wavelength converters and output WDM optical buffer. Under the condition of limited wavelength conversion, two wavelength control strategies, i.e., greedy mode and conservative mode, are proposed. According to these two wavelength control strategies, four wavelength allocation algorithms are presented. Performances of these algorithms are compared in detail by simulation experiments.

Yang, Junjie; Zhang, Hao; Ye, Tong; Shi, Zhengyi

2006-09-01

206

Measurement Assurance Program for Wavelength Dependence of  

E-print Network

Measurement Assurance Program for Wavelength Dependence of Polarization Dependent Loss in Fiber SERVICES: Measurement Assurance Program for Wavelength Dependence of Polarization Dependent Loss in Fiber Electronics and Electrical Engineering Laboratory National Institute of Standards and Technology 325 Broadway

207

Light Transmission through Sub-Wavelength Apertures  

E-print Network

Light Transmission through Sub-Wavelength Apertures #12;#12;VRIJE UNIVERSITEIT Light Transmission Transmission through a Single Sub-wavelength Slit 59 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 3.2 The configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.3 Transmission

Visser, Taco D.

208

Multi-wavelength study of MGRO J2019+37  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

209

Measurement of thin films using very long acoustic wavelengths  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

210

Wavelength conversion in optical transport networks  

Microsoft Academic Search

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical

R. Sabella; E. Iannone

1996-01-01

211

Flare stars at radio wavelengths  

NASA Technical Reports Server (NTRS)

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

Lang, Kenneth R.

1989-01-01

212

A novel wavelength switchable fiber ring laser  

Microsoft Academic Search

We demonstrate a fiber ring laser with a dispersion compensation fiber (DCF) and a delayed interferometer (DI), which is able to switch eleven wavelengths one by one. In ring cavity, DCF supplies different effective cavity lengths for different wavelengths, DI generates a wavelength comb corresponding to the ITU grid, a flat-gain erbium-doped fiber amplifier (EDFA) provides uniform gain for each

Fei Wang; Xinliang Zhang; Jianji Dong; Yu Yu; Zheng Zhang

2008-01-01

213

Wavelength Routing Networks -1 Optical Networks  

E-print Network

Wavelength Routing Networks - 1 Optical Networks: from fiber transmission to photonic switching Wavelength-Routing Networks Fabio Neri and Marco Mellia TLC Networks Group ­ Electronics Department e.mellia@polito.it ­ tel. 011 564 4173 #12;Wavelength Routing Networks - 3 Course program outline · Introduction

Mellia, Marco

214

FOCUS: MALDI Exploring Infrared Wavelength Matrix-  

E-print Network

FOCUS: MALDI Exploring Infrared Wavelength Matrix- Assisted Laser Desorption/Ionization of Proteins) to infrared-wavelength matrix-assisted time-of-flight mass spectrometry (IR-MALDI-TOF-MS) of proteins MALDI-mass spectrometry (MS) measurements of proteins make use of ultraviolet (UV) wavelength laser

Chait, Brian T.

215

External wavelength contention resolution for optical crossconnects  

E-print Network

External wavelength contention resolution for optical crossconnects C.Y. Li and P.K.A. Wai of OXCs in wavelength-routed networks. Simulations confirm the performance of the proposed approach. Introduction Wavelength-routed (WR) network is one of the impor- tant networking infrastructures because it can

Wai, Ping-kong Alexander

216

Modeling and Simulation of Advanced Nano-Scale Very Large Scale Integration Circuits  

E-print Network

With VLSI(very large scale integration) technology shrinking and frequency increasing, the minimum feature size is smaller than sub-wavelength lithography wavelength, and the manufacturing cost is significantly increasing in order to achieve a good...

Zhou, Ying

2010-07-14

217

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

218

Evaluation of a new real-time PCR assay (Check-Direct CPE) for rapid detection of KPC, OXA-48, VIM, and NDM carbapenemases using spiked rectal swabs.  

PubMed

To prevent the spread of carbapenemase-producing bacteria, a fast and accurate detection of patients carrying these bacteria is extremely important. The Check-Direct CPE assay (Check-Points, Wageningen, The Netherlands) is a new multiplex real-time PCR assay, which has been developed to detect and differentiate between the most prevalent carbapenemase genes encountered in Enterobacteriaceae (blaKPC, blaOXA-48, blaVIM, and blaNDM) directly from rectal swabs. Evaluation of this assay using 83 non-duplicate isolates demonstrated 100% sensitivity and specificity and the correct identification of the carbapenemase gene(s) present in all carbapenemase-producing isolates. Moreover, the limit of detection (LoD) of the real-time PCR assay in spiked rectal swabs was determined and showed comparable LoDs with the ChromID CARBA agar. With an excellent performance on clinical isolates and spiked rectal swabs, this assay appeared to be an accurate and rapid method to detect blaKPC, blaOXA-48, blaVIM, and blaNDM genes directly from a rectal screening swab. PMID:24135412

Nijhuis, Roel; Samuelsen, Orjan; Savelkoul, Paul; van Zwet, Anton

2013-12-01

219

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

PubMed

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

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

2014-05-01

220

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

PubMed Central

Background Resistance to carbapenem antibiotics is emerging worldwide among Enterobacteriaceae. To prevent hospital transmission due to unnoticed carriage of carbapenemase producing micro-organisms in newly admitted patients, or follow-up of patients in an outbreak setting, a molecular screening method was developed for detection of the most prevalent carbapenemase genes; blaOXA-48, blaVIM, blaIMP, blaNDM and blaKPC. Methods A real-time multiplex PCR assay was evaluated using a collection of 86 Gram negative isolates, including 62 carbapenemase producers. Seven different laboratories carried out this method and used the assay for detection of the carbapenemase genes on a selection of 20 isolates. Results Both sensitivity and specificity of the multiplex PCR assay was 100%, as established by results on the strain collection and the inter-laboratory comparisons. Conclusions In this study, we present a multiplex real-time PCR that is a robust, reliable and rapid method for the detection of the most prevalent carbapenemases blaOXA-48, blaVIM, blaIMP, blaNDM and blaKPC, and is suitable for screening of broth cultured rectal swabs and for identification of carbapenemase genes in cultures. PMID:24422880

2014-01-01

221

Color reflection holography using four recording wavelengths  

NASA Astrophysics Data System (ADS)

We present a theoretical analysis of color reflection holography using four recording wavelengths. The color reproduction of the hologram is discussed using the 1976 CIE chromaticity diagram. The optimum combination of the four wavelengths which minimizes the distance between the reconstructed image and the object points is calculated using nonlinear least square method. It is found that the extremely good color reproduction can be achieved by four- wavelength recording. We also analyze the color reproduction for the four practical laser wavelengths. The optimum choice of the wavelengths and the attainable color reproduction are discussed.

Kubota, Toshihiro; Takabayashi, Emi; Kashiwagi, Tsuyoshi; Watanabe, Masachika; Ueda, Kenji

2001-06-01

222

Wavelength correction of refractivity variation measurements.  

PubMed

The index of refraction structure constant, Cn2 indicates how strongly the index of refraction varies in a region of the atmosphere. These variations usually arise through turbulent motions, creating an inhomogeneous distribution of species, density, temperature and pressure. Because the index of refraction also depends on wavelength, the measured value of Cn2 will depend on wavelength. This Cn2 difference generally becomes more pronounced as the difference in wavelength increases. This paper describes a technique for converting between measurements of Cn2 at different wavelengths, and gives an example for converting from centimeter to visible and near IR wavelengths. PMID:24514794

Burchett, Lee R; Fiorino, Steven T

2013-12-30

223

Wavelength-encoded processing in semiconductor lasers  

NASA Astrophysics Data System (ADS)

It was the goal of this proposal to study the process of wavelength conversion and wavelength encoded processing in semiconductor laser types of devices. In particular, we report on: (1) the implementation of Boolean logic using wavelength encoded inputs; (2) the use of frequency modulation to control the transmission of a Fabry-Perot laser; (3) nonlinear spectral filtering of a multi-wavelength signal; (4) wavelength-conversion and logic operation based on bistable diode laser amplifiers, including a study of crosstalk, switching power, bit-error-rates, and demonstration of an optically controllable space-switch; (5) wavelength-conversion by a T-gate device; (6) wavelength conversion using four-wave mixing in a Fabry-Perot edge-emitting and vertical cavity surface emitting laser; and (7) high-speed polarization switching in vertical-cavity lasers.

Dagenais, M.

1994-06-01

224

BER Performance in Wavelength Packet Switched WDM systems during Nano-second Wavelength Switching Events  

E-print Network

. This effect may ultimately influence the design of WDM wavelength packet- switched networks employing transmitter, as the overall design of the wavelength packet-switched WDM networks will be heavily dependentBER Performance in Wavelength Packet Switched WDM systems during Nano-second Wavelength Switching

225

Effects of Wavelength Routing and Selection Algorithms on Wavelength Conversion Gain in WDM Optical Networks 1  

E-print Network

Effects of Wavelength Routing and Selection Algorithms on Wavelength Conversion Gain in WDM Optical­3030 Abstract 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

Ayanoglu, Ender

226

BER Performance in Wavelength Packet Switched WDM systems during Nano-second Wavelength Switching Events  

E-print Network

BER Performance in Wavelength Packet Switched WDM systems during Nano-second Wavelength Switching of another WDM signal during fast wavelength switching events. A nano-second tuneable laser is switched across the monitored channel to perform the study. Introduction The migration from single wavelength SDH

227

Radar scattering laws and wavelength dependence of the lunar surface  

NASA Technical Reports Server (NTRS)

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

Simpson, R. A.

1978-01-01

228

Wavelength-doubling optical parametric oscillator  

DOEpatents

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

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

2007-07-24

229

Improving the red wavelength sensitivity of CCDs  

NASA Astrophysics Data System (ADS)

The demand for higher red wavelength sensitivity is being met by various technological developments of modern CCDs. We discuss techniques for achieving higher red wavelength sensitivity by using thicker silicon to make backthinned CCDs, which combines with very low read noise for enhanced sensitivity. Thicker devices requires higher resistivity material including bulk (non epitaxial) silicon. An extended wavelength range also places more demand on the antireflection coatings which benefit from corresponding optimisation.

Jorden, Paul R.; Downing, Mark; Harris, Andrew; Kelt, Andrew; Mistry, Pritesh; Patel, Pash

2010-07-01

230

Athermal waveguides for optical communication wavelengths.  

PubMed

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

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

2011-12-01

231

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

232

A heuristic wavelength assignment algorithm for multihop WDM networks with wavelength routing and wavelength re-use  

Microsoft Academic Search

Abstmct-In this paper, we present a heuristic algorithm for effectively assigning a limited number of Wavelengths among the access stations of a multihop network wherein the physical medium consists of optical fiber segments which interconnect waveleagtbaelective optical switches. Such a physical medium permits the limited number of wavelengths to be re-used among the various fiber links, thereby offeting very high

Zlrensheng Zhang; Anthony S. Acampora

1995-01-01

233

Wavelength specific excitation of gold nanoparticle thin-films  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

234

Wavelength-domain RF photonic signal processing  

NASA Astrophysics Data System (ADS)

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

Gao, Lu

235

Wavelength Converters in Dynamically-Reconfigurable WDM Networks  

Microsoft Academic Search

In simple wavelength-division multiplexed (WDM) networks, a connection must be established along a route using a common wavelength on all of the links along the route. This constraint may be removed by the introduction of wavelength converters, which are devices which take the data modulated on an input wavelength and transfer it to a different output wavelength. Wavelength converters thus

Jennifer M. Yates; Michael P. Rumsewicz; Jonathan P. R. Lacey

1999-01-01

236

Full-scene subnanometer HYDICE wavelength calibration  

Microsoft Academic Search

The Hyperspectral Data and Information Collection Experiment (HYDICE) collected data during 1995 for purposes of assessing and verifying performance. Accurate wavelength calibration to +\\/- 0.1 nm is essential for proper application of atmospheric models in order to derive apparent surface reflectance. A method for precise wavelength calibration is described that makes use of the narrow atmospheric oxygen band absorption feature

Alexander F. Goetz; Kathleen B. Heidebrecht

1996-01-01

237

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

238

Wavelength (nm) 300 400 500 600 700  

E-print Network

Wavelength (nm) 300 400 500 600 700 Isc(nAcm-2) -2 0 2 4 6 8 10 12 AJ-assembly J-domain X 10 The AJ absorption fluorescence Wavelength (nm) 300 400 500 600 700 J Absorption A Absorption AJ Fluorescence J

239

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

240

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

241

Fixed-alternate routing and wavelength conversion in wavelength-routed optical networks  

Microsoft Academic Search

This paper considers optical networks which employ wavelength-routing switches that enable the establishment of wavelength-division-multiplexed (WDM) connections between node-pairs. Alternate routing improves the blocking performance of such networks by providing multiple possible paths between node-pairs. Wavelength conversion improves the blocking performance of such networks by allowing a connection to use different wavelengths along its route. This paper proposes an approximate

S. Ramamurthy; Biswanath Mukherjee

1998-01-01

242

Practical Routing and Wavelength Assignment algorithms for All Optical Networks with Limited Wavelength Conversion  

E-print Network

Practical Routing and Wavelength Assignment algorithms for All Optical Networks with Limited Wavelength Conversion M.D. Swaminathan*, Indian Institute of Science, Bangalore, India. K.N. Sivarajan, kumar and a Ã? shortest path based heuristic algorithm for solving the Rout- ing and Wavelength Assignment

Swaminathan, Madhavan

243

Evaluation of Clonality and Carbapenem Resistance Mechanisms among Acinetobacter baumannii-Acinetobacter calcoaceticus Complex and Enterobacteriaceae Isolates Collected in European and Mediterranean Countries and Detection of Two Novel ?-Lactamases, GES-22 and VIM-35.  

PubMed

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

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

2014-12-01

244

Analysis of multi-wavelength active coherent polarization beam combining system.  

PubMed

In this manuscript, the multi-wavelength active coherent polarization beam combining (CPBC) system is investigated theoretically and experimentally. The relationship between the combining efficiency and the optical path difference (OPD), wavelength number, and the spectral density of power of the amplifier chains is analyzed and validated by establishing a two-channel multi-wavelength CPBC system. Further, the relationship between the combining efficiency and the voltage signal of the photo-detector is developed and validated experimentally. Finally, the feasibility of the active CPBC technique with complex spectral structures is verified and as high as 96% combining efficiency is obtained based on all fiber delay lines to compensate the OPD between different channels, which is crucial for further power scaling of the CPBC system. Our theoretical analysis offers a useful approach to estimate the influence of OPDs, wavelength number, and the spectral density of power of the amplifier chains on multi-wavelength active CPBC system. PMID:24977903

Ma, Pengfei; Wang, Xiaolin; Ma, Yanxing; Zhou, Pu; Liu, Zejin

2014-06-30

245

A novel wavelength availability advertisement based ASON routing protocol implementation  

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

246

Sub-wavelength focusing meta-lens.  

PubMed

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

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

2013-03-25

247

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

248

Multiple wavelength photolithography for preparing multilayer microstructures  

DOEpatents

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

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

2003-06-24

249

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

250

Polymer photochemistry at the EUV wavelength  

E-print Network

The higher energy associated with extreme ultraviolet (EUV) radiation coupled with the high absorptivity of most organic polymers at these wavelengths should lead to increased excited state population and higher quantum ...

Fedynyshyn, Theodore H.

251

WAVELENGTH CALIBRATION OF THE VLT-UVES SPECTROGRAPH  

SciTech Connect

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

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

2010-11-01

252

Nonlocal theory of long-wavelength plasma waves associated with sporadic E layers  

SciTech Connect

In this paper we calculate the nonlocal growth rate of gradient drift plasma waves under conditions where the electron density gradient scale length changes with altitude. The results are compared with the local growth rate and discussed in the context of the kilometer-scale waves which have been observed in the vicinity of mid-latitude sporadic E layers. These large-scale waves drastically violate the local approximation, kL/sub m/>>1, where k is the irregularity wave number and L/sub m/ is the minimum gradient scale length on the edge of a layer. The first step in the analysis is to derive a general eigenmode equation, starting with the same assumptions usually used in the derivation of the local dispersion relation for long wavelength waves. Modeling a sporadic E layer as a slab, the nonlocal growth rate spectrum is found by solving the eigenmode equation for this profile. The solution is an algebraic dispersion relation with a growth rate spectrum which is roughly proportional to k, rather than the k/sup 2/ dependence predicted by conventional local theory at long wavelengths. At short wavelengths the nonlocal growth rate determined with the slab is unbounded, in disagreement with local theory. The slab is an inadequate model for short wavelength waves and a bound on the growth rate is instead derived from a theory which can be applied to any realistic profile with nonzero L/sub m/. At short wavelengths this bound is identical to the local growth rate expression, while at long wavelengths the bound remains proportional to k and thus is consistent with the dispersion relation for a slab. Nonlocal effects alone do not explain the dominance of kilometer scales, but they do tend to favor the excitation of long wavelengths.

Riggin, D.; Kadish, A.

1989-02-01

253

Observations of Venus at 1-meter wavelength  

NASA Astrophysics Data System (ADS)

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

Butler, Bryan J.

2014-11-01

254

Long-wavelength VCSELs for sensing applications  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

255

Optimal Wavelength Routing on Directed Fiber Trees  

Microsoft Academic Search

We present a polynomial time greedy algorithm that assigns proper wavelengths to a set ofrequests of maximum load L per directed fiber link on a directed fiber tree using at most 5=3Lwavelengths. This improves previous results of [12, 10, 8, 9].We also prove that no greedy algorithm can in general use less than 5=3L wavelengths for aset of requests of

Thomas Erlebach; Klaus Jansen; Christos Kaklamanis; Milena Mihail; Pino Persiano

1999-01-01

256

Fiber parametric amplifiers for wavelength band conversion  

Microsoft Academic Search

By using a loop configuration formed by a polarization beam splitter, we experimentally demonstrate that the existing wavelength-division multiplexing (WDM) sources in C-band can be wavelength converted to the S-band with low polarization sensitivity and low crosstalk. Using a fiber parametric amplifier as a band converter, we achieve experimentally 4.7-dB conversion efficiency over 30-nm conversion bandwidth in 315 m of

Mohammed N. Islam; O. Boyraz

2002-01-01

257

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

PubMed Central

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

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

2011-01-01

258

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

PubMed

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

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

2011-04-01

259

C-band wavelength conversion in silicon photonic wire waveguides.  

PubMed

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

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

2005-05-30

260

Long-Wavelength Elastic Interactions in Complex Crystals  

NASA Astrophysics Data System (ADS)

The long-wavelength (LWL) limit of the elastic interactions in complex non-Bravais lattices is investigated on the basis of microscopic elasticity theory. The conceptual simplicity of our approach enables large-scale simulations in materials with complex crystalline structures. We demonstrate the method by calculating the LWL elastic energy of hcp-based dilute Mg alloys for a variety of impurities. Our results show that for large coherent precipitates, the strain-induced interactions control the shape along the hexagonal axis whereas the surface energy dictates the basal growth. Our method allows a straightforward treatment of the long-range elastic interactions in the cluster expansion method for complex crystals.

Diaz Ortiz, Alejandro; Kurta, Ruslan; Bugaev, Volodymyr

2010-03-01

261

Damping of long-wavelength kinetic alfven fluctuations: linear theory  

SciTech Connect

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

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

2008-01-01

262

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

263

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

PubMed Central

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

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

2014-01-01

264

Laser-Matter Interactions at Sub-Micron Laser Wavelengths.  

NASA Astrophysics Data System (ADS)

In recent years there has been considerable interest in the use of sub-micron wavelength lasers for target irradiation in laser fusion experiments. We present here an experimental investiation of laser-matter interaction in this short wavelength regime. We have irradiated planar targets with 0.532, 0.355 and 0.266 (mu)m laser light with pulse lengths of 2 ns and at intensities ranging from 10('12) to 5 x 10('13) W/cm('2). The results show that for these conditions inverse bremsstrahlung is very effective and leads to very high absorption ((TURN)95%). The X-ray spectrum also show that the absorbed energy is well thermalized and only a small number of energetic, non-thermal electrons are present. Also a very low level of scattered light was measured indicating that laser-plasma collective processes are not important. Energy transport was investigated using multilayer targets. Anomalous laser penetration depths in the target were obtained in these measurements. This has been successfully explained in a simple hydrodynamic model where two-dimensional effects were taken into account. In the study of the ablation process wavelength and intensity scaling laws for the mass ablation rate and ablation pressure have been obtained. These results show the inadequacy of the present analytical theories of the laser-driven ablation process.

Pasini, Daniel

265

Wavelength mapping of mixed semiconductors using an automatic IR spectrophotometer  

NASA Astrophysics Data System (ADS)

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

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

1984-09-01

266

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

267

Detection of the dMe flare star YZ Canis Minoris simultaneously at 20 and 90 centimeter wavelengths  

NASA Astrophysics Data System (ADS)

The first aperture synthesis detection of the flare star YZ CMi at 90 cm wavelength is presented here. The simultaneous observations carried out at 20 and 90 cm wavelengths show that the emission at the two wavelengths is unipolar in the same sense and is uncorrelated. The high brightness temperature of ?1013K at 90 cm wavelength strongly supports the coherent nature of the emission. The authors propose that the coherent emission is intrinsically unpolarized and the polarization is introduced by absorption in the higher coronal levels with large-scale magnetic fields, presumably the dipole magnetic field.

Kundu, M. R.; Shevgaonkar, R. K.

1988-11-01

268

The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence  

SciTech Connect

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

Newman, D.E.

1993-09-01

269

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

NASA Astrophysics Data System (ADS)

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

Momary, Thomas W.; Baines, Kevin H.

2014-11-01

270

Submillimeter Wavelength Modeling of Dielectric Materials in Polarimetric Radar Approaches  

E-print Network

the feasibility of modeling clutter at microwave and millimeter wavelengths. Introduction The concept of usingSubmillimeter Wavelength Modeling of Dielectric Materials in Polarimetric Radar Approaches R made polarimetric study of dielectric materials at submillimeter wavelengths possible. The first

Massachusetts at Lowell, University of

271

Scaling exponents estimation from time-scale energy distributions  

Microsoft Academic Search

It is shown using some examples that the problem of estimating the evolution of scaling exponents characterizing locally a self-similar process can be efficiently handled within the general framework of time-scale energy distributions related to the wavelength transform. As is implicit from the structure of the estimators considered, the proposed methodology is dependent on the degree of nonstationarity of such

P. Goncalves; P. Flandrin

1992-01-01

272

Two wavelength satellite laser ranging using SPAD  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

273

Wavelength-tunable silicon microring modulator.  

PubMed

We present a wavelength-tunable, compact, high speed and low power silicon microring modulator. With a ring radius of 5 microm, we demonstrate a modulator with a high speed of 12.5 Gbps and a driving voltage of 3 V to achieve approximately 6 dB extinction ratio in high speed measurement. More importantly, tunability of the resonant wavelength is accomplished by means of a microheater on top of the ring, with an efficiency of 2.4 mW/nm (2.4 mW is needed to tune the resonant wavelength by 1 nm). This device aims to solve the narrow bandwidth problem of silicon microcavity modulators and increase the data bandwidth in optical interconnect systems. PMID:20588949

Dong, Po; Shafiiha, Roshanak; Liao, Shirong; Liang, Hong; Feng, Ning-Ning; Feng, Dazeng; Li, Guoliang; Zheng, Xuezhe; Krishnamoorthy, Ashok V; Asghari, Mehdi

2010-05-24

274

Full-scene subnanometer HYDICE wavelength calibration  

NASA Astrophysics Data System (ADS)

The Hyperspectral Data and Information Collection Experiment (HYDICE) collected data during 1995 for purposes of assessing and verifying performance. Accurate wavelength calibration to +/- 0.1 nm is essential for proper application of atmospheric models in order to derive apparent surface reflectance. A method for precise wavelength calibration is described that makes use of the narrow atmospheric oxygen band absorption feature at 762 nm. Precision of +/- 0.1 nm is feasible despite variable surface cover if the signal-to-noise ratio is greater than 100. Resampling the HYDICE images to a common wavelength results in reduced spectral resolution and adversely affects the radiometric accuracy of narrow features such as the oxygen band.

Goetz, Alexander F. H.; Heidebrecht, Kathleen B.

1996-11-01

275

On storage rings for short wavelength FELs  

SciTech Connect

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

Chattopadhyay, S.

1990-01-01

276

Mechanisms and Methods for Selective Wavelength Filtering  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

277

Radio Wavelength Observatories within the Exploration Architecture  

E-print Network

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

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

2007-01-26

278

Planetary brightness temperature measurements at 8.6 mm and 3.1 mm wavelengths.  

NASA Technical Reports Server (NTRS)

New measurements of the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn at 3.1- and 8.6-mm wavelengths are given. The temperatures reported for the planets at 3.1-mm wavelength are higher than previous measurements in this wavelength range and change the interpretation of some planetary spectra. For Mercury, it is found that the mean brightness temperature is independent of wavelength and that a temperature-dependent thermal conductivity is not required to match the observations. In the case of Mars, the spectrum is shown to rise in the millimeter region, as simple models predict. For Jupiter, the need to recalculate the spectrum with recent models is demonstrated. The flux density scale proposed by Dent (1972) has been revised according to a more accurate determination of the millimeter brightness temperature of Jupiter.

Ulich, B. L.; Cogdell, J. R.; Davis, J. H.

1973-01-01

279

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

PubMed

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

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

2014-07-01

280

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

PubMed Central

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

2010-01-01

281

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

E-print Network

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

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

2014-01-01

282

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

NASA Astrophysics Data System (ADS)

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

Montano, J. W.

1986-09-01

283

Wavelength selection for imaging hemoglobin in skin  

NASA Astrophysics Data System (ADS)

Hyperspectral imaging has been shown to be useful for producing qualitative maps of the concentration of hemoglobin in skin, and quantitative maps of its oxygen saturation. These maps provide information about the health of the skin, which may be useful in medical diagnosis and in planning intervention for skin lesions. Wavelengths have usually been determined on a somewhat intuitive basis using spectra based on analytical models. In the present work, we demonstrate a means of selecting wavelengths from a data cube of experimental data.

Rodriguez-Diaz, Eladio; Velez-Reyes, Miguel; Chin, Ronald K.; DiMarzio, Charles A.

2000-07-01

284

Wavelength Calculator Applet Version 2.0  

NSDL National Science Digital Library

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

Ravaioli, Umberto

2012-04-23

285

Idea Bank: Measuring Wavelength with a Ruler  

NSDL National Science Digital Library

In the late 1960s, Arthur Schawlow, co-inventor of the laser, visited the author's high school physics department to share some intriguing laser demonstrations. He popped colored balloons inside transparent ones, and showed interesting diffraction patterns with laser light. The most memorable demonstration began with the following question: "Can the wavelength of laser light be measured using only a common ruler?" Schawlow's explanation can be simplified and used to easily measure the wavelength of laser light in the classroom (Schawlow 1965), which is described here.

Hewitt, Paul

2004-09-01

286

Modulation compression for short wavelength harmonic generation  

SciTech Connect

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

Qiang, J.

2010-01-11

287

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

288

Short wavelength ion temperature gradient turbulence  

SciTech Connect

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

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

2012-10-15

289

Quantum key distribution network with wavelength addressing  

E-print Network

Most traditional applications of quantum cryptography are point-to-point communications, in which only two users can exchange keys. In this letter, we present a network scheme that enable quantum key distribution between multi-user with wavelength addressing. Considering the current state of wavelength division multiplexing technique, dozens or hundreds of users can be connected to such a network and directly exchange keys with each other. With the scheme, a 4-user demonstration network was built up and key exchanges were performed.

Xiao-Fan Mo; Tao Zhang; Fang-Xing Xu; Zheng-Fu Han; Guang-Can Guo

2006-10-12

290

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

291

SWCam: the short wavelength camera for the CCAT Observatory  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

292

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

293

Self Calibration of a 2-wavelength Pyrometer  

NASA Technical Reports Server (NTRS)

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

Ng, Daniel

1998-01-01

294

Analytical long-wavelength approximation for parallelepipeds  

NASA Astrophysics Data System (ADS)

We suggest a new analytical long-wavelength approximation for rectangular parallelepipeds based on replacement of the internal field with a uniform one. The approximation is not quite accurate (the typical accuracy is of the order of about 10%) but is extremely simple and works in a sufficiently wide region of parameter values.

Farafonov, Victor G.; Il'in, Vladimir B.

2014-10-01

295

Discrete wavelength-locked external cavity laser  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

296

The wavelength dependence of Triton's light curve  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

297

Wavelength doubling bifurcations in coupled map lattices  

Microsoft Academic Search

We report an interesting phenomenon of wavelength doubling bifurcations in the model of coupled (logistic) map lattices. The temporal and spatial periods of the observed patterns undergo successive period doubling bifurcations with decreasing coupling strength. The universality constants alpha and delta appear to be the same as in the case of period doubling route to chaos in the uncoupled logistic

R. E. Amritkar; P. M. Gade

1993-01-01

298

Electricity and short wavelength radiation generator  

DOEpatents

Methods and associated apparati for use of collisions of high energy atoms and ions of He, Ne, or Ar with themselves or with high energy neutrons to produce short wavelength radiation (lambda approx. = 840-1300 A) that may be utilized to produce cathode-anode currents or photovoltaic currents.

George, E.V.

1985-08-26

299

Two wavelength satellite laser ranging using SPAD  

Microsoft Academic Search

When ranging to satellites with lasers, there are several principal contributions to the error budget: from the laser ranging system on the ground, from the satellite retroarray geometry, and from the atmosphere. Using a single wavelength, we have routinely achieved a ranging precision of 8 millimeters when ranging to the ERS-1 and Starlette satellites. The systematic error of the atmosphere,

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

1993-01-01

300

Wavelength conversion in optical packet switching  

Microsoft Academic Search

A detailed traffic analysis of optical packet switch design is performed. Special consideration is given to the complexity of the optical buffering and the overall switch block structure is considered in general. Wavelength converters are shown to improve the traffic performance of the switch blocks for both random and bursty traffic. Furthermore, the traffic performance of switch blocks with add-drop

Soeren Lykke Danielsen; Peter Bukhave Hansen; Kristian E. Stubkjaer

1998-01-01

301

Lightpath (Wavelength) Routing in Large WDM Networks  

Microsoft Academic Search

We address the problem of efficient circuit switching in wide area optical networks. The solution provided is based on finding optimal routes for lightpaths and the new concept of semilightpaths. A lightpath is a fully optical transmission path, while a semilightpath is a transmission path constructed by chaining together several lightpaths, using wavelength conversion at their junctions. A fast and

Imrich Chlamtac; András Faragó; Tao Zhang

1996-01-01

302

RESOLVING THE MOTH AT MILLIMETER WAVELENGTHS  

SciTech Connect

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

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

2013-09-01

303

Experimental wavelength division multiplexed photon pair distribution  

E-print Network

We have experimentally implemented the distribution of photon pairs produced by spontaneous parametric down conversion through telecom dense wavelength division multiplexing filters. Using the measured counts and coincidences between symmetric channels, we evaluate the maximum fringe visibility that can be obtained with polarization entangled photons and compare different filter technologies.

Joe Ghalbouni; Imad Agha; Robert Frey; Eleni Diamanti; Isabelle Zaquine

2012-10-03

304

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

305

Intraocular lens short wavelength light filtering.  

PubMed

There is increasing interest in the effects of reactive oxygen species ('free radicals') in ageing, both in the body overall and specifically in the eye. Cataract and age-related macular degeneration (AMD) are two major causes of blindness, with cataract accounting for 48 per cent of world blindness and AMD accounting for 8.7 per cent. Both cataract and AMD affect an older population (over 50?years of age) and while cataract is largely treatable provided resources are available, AMD is a common cause of untreatable, progressive visual loss. There is evidence that AMD is linked to exposure to short wavelength electromagnetic radiation, which includes ultraviolet, blue and violet wavelengths. The ageing crystalline lens provides some protection to the posterior pole because, as it yellows with age, its spectral absorption increasingly blocks the shorter wavelengths of light. Ultraviolet blocking intraocular lenses (IOLs) have been the standard of care for many years but a more recent trend is to include blue-blocking filters based on theoretical benefits. As these filters absorb part of the visible spectrum, they may affect visual function. This review looks at the risks and the benefits of filtering out short wavelength light in pseudophakic patients. PMID:20950366

Edwards, Keith H; Gibson, G Anthony

2010-11-01

306

A wavelength routing approach to optical communications networks  

Microsoft Academic Search

A class of wavelength-routing optical networks is described on the basis of the interconnection of wavelength multiplexed channels. Unlike previously described optical network structures, these networks allow the reuse of wavelengths in different transmission sections and this leads to fewer wavelengths being needed. A choice of structures using a common set of components leads to the opportunity to design a

G. R. Hill

1988-01-01

307

All Optical Wavelength Conversion at 10 Gbps Introduction  

E-print Network

All Optical Wavelength Conversion at 10 Gbps Introduction We report the demonstration of all-optical wavelength con- version of intensity-modulated data from the probe wave- length to the conjugate wavelength transferred to conjugate wavelength. Experimental Setup ! Figure 1. Schematic of the experimental setup

Das, Bijoy Krishna

308

Sub-wavelength focusing meta-lens Tapashree Roy,1  

E-print Network

Sub-wavelength focusing meta-lens Tapashree Roy,1 Edward T. F. Rogers,1 and Nikolay I. Zheludev1- wavelength hot-spots located beyond the near-field of the metamaterial. By nano-structuring a gold film we by a wavelength of 800 nm. We attribute the occurrence of sub-wavelength hotspots beyond the near field

Zheludev, Nikolay

309

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

NASA Astrophysics Data System (ADS)

A simple widely tunable wavelength spacing dual-wavelength single longitudinal mode (SLM) erbium doped fiber laser (EDFL) based on cascaded fiber Bragg gratings (FBGs) and birefringent fiber filter is proposed and demonstrated. Experimental results show that the lasing wavelength spacing is widely tunable in a range from 2 nm to 18 nm, which has potential to generate frequency tunable terahertz (THz) waves by beating the lasing dual-wavelength in a high speed photodetector. The birefringent fiber filter acts as an ultra-narrow bandpass filter and benefits the simultaneous oscillation of dual-wavelength in a single laser cavity. The output peak power of the lasing dual-wavelength is approximately equalized at room temperature, and a high optical signal-to-noise ratio (OSNR) is realized in the whole tuning range. The SLM operation of dual-wavelength fiber laser is verified by Fabry-Perot (F-P) scanning interferometer, and the clear eye diagram proves that the proposed fiber laser is effective in the application of fiber optic communication system.

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

2014-06-01

310

A wavelength-switched time-slot routing scheme for wavelength-routed networks P. K. A. Wai,1  

E-print Network

A wavelength-switched time-slot routing scheme for wavelength-routed networks C. Y. Li,1 G. M. Li,2 of wavelength- routed (WR) networks. Implementation of all-optical time-slot routing in OTDM-WR networks. In this paper, we proposed a wavelength-switched time- slot routing scheme that can be implemented with fast

Wai, Ping-kong Alexander

311

All-optical Wavelength Conversion in Aluminum Gallium Arsenide at Telecommunications Wavelengths.  

E-print Network

??This thesis aims at both developing highly nonlinear Aluminum Gallium Arsenide waveguides(AlGaAs) and demonstrating all-optical wavelength conversion via cross-phase modulation in AlGaAs waveguides at telecommunications… (more)

Ng, Wing-Chau

2011-01-01

312

Nanoscale dynamics by short-wavelength four wave mixing experiments  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

313

A superradiant clock laser on a magic wavelength optical lattice  

NASA Astrophysics Data System (ADS)

An ideal superradiant laser on an optical clock transition of noninteracting cold atoms is predicted to exhibit an extreme frequency stability and accuracy far below mHz-linewidth. In any concrete setup sufficiently many atoms have to be confined and pumped within a finite cavity mode volume. Using a magic wavelength lattice minimizes light shifts and allows for almost uniform coupling to the cavity mode. Never- theless, the atoms are subject to dipole-dipole interaction and collective spontaneous decay which compromises the ultimate frequency stability. In the high density limit the Dicke superradiant linewidth enhancement will broaden the laser line and nearest neighbor couplings will induce shifts and fluctuations of the laser frequency. We estimate the magnitude and scaling of these effects by direct numerical simulations of few atom systems for different geometries and densities. For Strontium in a regularly filled magic wavelength configuration atomic interactions induce small laser frequency shifts only and collective spontaneous emission weakly broadens the laser. These interactions generally enhance the laser sensitivity to cavity length fluctuations but for optimally chosen operating conditions can lead to an improved synchronization of the atomic dipoles.

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

2014-06-01

314

A superradiant clock laser on a magic wavelength optical lattice.  

PubMed

An ideal superradiant laser on an optical clock transition of noninteracting cold atoms is predicted to exhibit an extreme frequency stability and accuracy far below mHz-linewidth. In any concrete setup sufficiently many atoms have to be confined and pumped within a finite cavity mode volume. Using a magic wavelength lattice minimizes light shifts and allows for almost uniform coupling to the cavity mode. Nevertheless, the atoms are subject to dipole-dipole interaction and collective spontaneous decay which compromises the ultimate frequency stability. In the high density limit the Dicke superradiant linewidth enhancement will broaden the laser line and nearest neighbor couplings will induce shifts and fluctuations of the laser frequency. We estimate the magnitude and scaling of these effects by direct numerical simulations of few atom systems for different geometries and densities. For Strontium in a regularly filled magic wavelength configuration atomic interactions induce small laser frequency shifts only and collective spontaneous emission weakly broadens the laser. These interactions generally enhance the laser sensitivity to cavity length fluctuations but for optimally chosen operating conditions can lead to an improved synchronization of the atomic dipoles. PMID:24921521

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

2014-06-01

315

Discrete Wavelength-Locked External Cavity Laser  

NASA Technical Reports Server (NTRS)

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

Pilgrim, Jeffrey S.; Silver, Joel A.

2004-01-01

316

The Long Wavelength Array Software Library  

E-print Network

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 ($\\gtrsim$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; Stovall, Kevin; Ray, Paul S; Clarke, Tracy; Taylor, Gregory

2012-01-01

317

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

318

Coordinated observations of PHEMU at radio wavelengths.  

NASA Astrophysics Data System (ADS)

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

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

319

WAVELENGTH CALIBRATION OF THE HAMILTON ECHELLE SPECTROGRAPH  

SciTech Connect

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

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

2013-10-01

320

Dual-wavelength laser with topological charge  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

321

Radio Wavelength Transients: Current and Emerging Prospects  

E-print Network

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

J. Lazio

2008-01-18

322

Wavelength-selective uncaging of oligonucleotides.  

PubMed

Caged compounds are light-sensitive molecules with temporarily inactivated biological function. The active compound is released upon irradiation, in which exact spatial and temporal control is accomplished. Beyond this inherently irreversible concept of triggering, the idea of multi-wavelength uncaging provides experiments with more complexity. This unit describes the syntheses of protected nucleoside phosphoramidites of caged dT(NpHP) [pHP = (p-hydroxyphenacyl)], dT(DEACM) {DEACM = [(7-diethylaminocoumarin-4-yl)methyl]} or a dC(NDBF) {NDBF = [1-(3-nitrodibenzofuran-1-yl)ethyl]} modification on the nucleobase, their incorporation in oligonucleotides, characterization, and their wavelength-selective uncaging up to four levels. Curr. Protoc. Nucleic Acid Chem. 57:6.11.1-6.11.32. © 2014 by John Wiley & Sons, Inc. PMID:24961722

Rodrigues-Correia, Alexandre; Seyfried, Patrick; Heckel, Alexander

2014-01-01

323

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

324

Varactor diodes for millimeter and submillimeter wavelengths  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

325

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

326

Astrochemistry at Millimetre and Submillimetre Wavelengths  

Microsoft Academic Search

The focus of this thesis is a series of observational tests, aiming to clarify the chemical and physical origin of interstellar molecules. Spectral lines at millimetre and submillimetre wavelengths, caused by rotational transitions in CO, H2O, NH3, CH3OH, CH3SH, C2H3CN, and several of their isotopologues, have been observed towards regions of star-formation in the Galaxy. Maps of extended H2O and

Eva Wirström S

2009-01-01

327

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

328

Deformable mirror for short wavelength applications  

DOEpatents

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

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

1999-01-01

329

Laser damage thresholds at short wavelengths  

Microsoft Academic Search

A survey of single-pulse laser damage thresholds for a wide variety of commercially available film coatings and prepared surfaces is reported. Tests were conducted at 532, 355, and 248 nm. Pulses for the longer wavelengths, generated by harmonic conversion of 1064-nm light from a Nd:glass laser, had a duration of 0.7 nsec. The 248-nm pulses had a 20-nsec duration and

F. Rainer; T. F. Deaton

1982-01-01

330

Wavelength Calibration in Physical Model Based Pipelines  

Microsoft Academic Search

We show how the wavelength calibration of complex 2D-spectrograms, such as echelle and long slit spectra, can be achieved in a fully self-consistent manner by a physical model based pipeline. The ST-ECF is currently upgrading the HST STIS data calibration pipeline in a step-by-step manner. In a first step the Calibration Enhanced CE-calstis pipeline will be able to generate the

M. Fiorentino; P. Bristow; F. Kerber; M. Rosa

2005-01-01

331

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

332

Gas sensing using wavelength modulation spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

333

Multiple wavelength X-ray monochromators  

DOEpatents

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

Steinmeyer, P.A.

1992-11-17

334

Estimation of Snow Parameters from Dual-Wavelength Airborne Radar  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

335

Long wavelength radar for geological analysis in vegetated terrain  

NASA Technical Reports Server (NTRS)

In contrast to shorter wavelength radars, the range of returns from vegetated surfaces is appreciably less at L-band frequencies. However, the evaluation of differences in image quality due to changes in operational frequency is hindered by several system dissimilarities. In particular, a comparison of the Ka, X- and L-band radar imagery is difficult because of differences in 'effective' resolution. Though the physical resolution of these systems may be somewhat comparable, the inherent averaging of the real aperture systems (X-and Ka-) provides an apparent wider range of gray tones. This effect is related to the fact that at a scale where the resolution cell is discernable, the coherent scintillation of 'speckle' of the synthetic aperture L-band system masks tonal variations. This mismatch of effective resolution impedes detection of small changes in gray tone and makes subtle boundary changes less distinct.

Macdonald, H. C.; Waite, W. P.; Tolman, D. N.; Borengasser, M.

1978-01-01

336

Fast multi-wavelength variability from a black hole  

NASA Astrophysics Data System (ADS)

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

O'Brien, Kieran

2011-10-01

337

Long-Wavelength Elastic Interactions in Complex Crystals  

NASA Astrophysics Data System (ADS)

The long-wavelength (LWL) limit of the elastic interactions in complex non-Bravais lattices is investigated on the basis of microscopic elasticity theory. The conceptual simplicity of our approach enables large-scale simulations in materials with complex crystalline structures. We demonstrate the method by calculating the LWL elastic energy of hcp-based Mg binary alloys for a variety of impurities. Our results show that for large coherent precipitates, the strain-induced interactions control the shape along the hexagonal axis, whereas the surface energy dictates the basal growth. The present formalism enables a straightforward treatment of the long-range elastic interactions in the cluster expansion method for complex crystals.

Kurta, Ruslan P.; Bugaev, Volodymyr N.; Ortiz, Alejandro Díaz

2010-02-01

338

A Novel Portable Multi-Wavelength Laser System  

NASA Astrophysics Data System (ADS)

There is an established need for a portable and affordable Q-switched laser system for use in studio conservation and small scale field use. The ideal system would be capable of producing a variety of wavelengths ranging from the ultraviolet to the infrared with sufficient energy per pulse to treat a wide range of materials including stone, marble, terracotta, wood, organic materials, bone, parchment, textiles, and metals. In this paper we report on such a system which is capable of delivering Q-switched output at 1,064nm in excess of 300mJ per pulse and at repetition rates of up to 25 Hz. Additional outputs are also reported at 266 nm, 355 nm, 532 nm, and 2.94 ?m. Preliminary cleaning results on a small range of objects using the Q-switched 1,064nm output are presented.

Charlton, Andy; Dickinson, B.

339

Acoustic dynamics of network-forming glasses at mesoscopic wavelengths  

PubMed Central

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

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

2013-01-01

340

Comparing laser-induced retinal damage from ir wavelengths to that from visible wavelengths  

NASA Astrophysics Data System (ADS)

An earlier report documented exposure parameters for inducing corneal, lens, and retinal damage with a laser emitting in the `eye-safe' wavelength range (Nd:YAG laser radiation at 1.318 micrometers and 1.356 micrometers ). Ocular damage thresholds are much higher for these wavelengths than for visible wavelength lasers. However, it was also noted that an exposure in the `eye-safe' wavelength range may result in multiple damage sites throughout the ocular medium and retina/choroid; that seemingly unaffected exposure sites, when monitored over time, may reveal slowly developing (days or longer) tissue degeneration; and, that the tissue degradation may ultimately involve regions greater in area than those directly irradiated by the laser. In order to elucidate the nature of tissue degeneration following IR laser exposure, the comparative pathology of retinal tissues exposed to argon and IR laser radiation is reported. Further, periodic post-exposure exams were conducted using scanning laser ophthalmoscopy to monitor the in vivo progress of the ocular tissue response following IR exposures. These observations are also contrasted to the results of corresponding examinations following visible wavelength laser exposures.

Zuclich, Joseph A.; Schuschereba, Steven T.; Zwick, Harry; Cheney, F.; Stuck, Bruce E.

1996-04-01

341

Two wavelength division multiplexing WAN trials  

SciTech Connect

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

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

1995-01-20

342

High efficiency CCD detectors at UV wavelengths  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

343

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Frequency and wavelength bands. 2.101 Section 2.101 Telecommunication ...and Use of Radio Frequencies § 2.101 Frequency and wavelength bands. (a) The radio spectrum shall be...

2010-10-01

344

47 CFR 2.101 - Frequency and wavelength bands.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Frequency and wavelength bands. 2.101 Section 2.101 Telecommunication ...and Use of Radio Frequencies § 2.101 Frequency and wavelength bands. (a) The radio spectrum shall be...

2011-10-01

345

Demonstration of a compact wavelength tracker using a tunable silicon resonator.  

PubMed

Here, we demonstrate a chip-scale integrated optical wavelength tracker with fast response and compact format. By exploiting the electro-optic(EO) effect on a thermally controlled silicon micro-ring resonator filter, the proposed tracker can operate over a wide wavelength range according to the thermo-optic (TO) effect; meanwhile, the tracker's response speed is greatly improved through the EO effect (i.e. tracking within 1 ns), as compared to the traditional TO controlled methods (typical ~10 ?s). With the integration of a photodiode onto the photonics chip, the compact chip is with a footprint of 0.5 mm × 1.5 mm. This tracker has potential applications for wavelength tacking in advanced DWDM network systems, tunable laser sources, and high performance optical sensors. PMID:25321985

Tao, Jifang; Cai, Hong; Gu, Yuandong; Liu, Aiqun

2014-10-01

346

Dual polarized long wavelength radar for discrimination of agricultural land use  

NASA Technical Reports Server (NTRS)

The scattered return of imaging radars is primarily sensitive to target structure or roughness and to composition of complex permittivity. The relative degree of penetration, or the depth of material to which the return is sensitive, also varies directly with the wavelength. Where vegetation can be eliminated as a factor, the surface return may be analyzed for variations in roughness or composition (primarily moisture content). L-band (25-cm) imagery has provided evidence that long-wavelength systems with improved penetration capability have the potential for minimizing the vegetation contribution and enhancing the surface return variations. However, the increased wavelength increases the sensitivity to large-scale structure. In the present paper, it is shown that addition of a cross polarized channel enables the interpreter to distinguish vegetation and orientation perturbations in the surface return.

Waite, W. P.; Macdonald, H. C.; Tolman, D. N.; Barlow, C. A.; Borengasser, M.

1978-01-01

347

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

PubMed

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

García-Martínez, P; Martínez, J L; Sánchez-López, M M; Moreno, I

2010-09-10

348

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

E-print Network

Recently, the electrostatic gyrokinetic Hamiltonian and change of coordinates have been computed to order $\\epsilon^2$ in general magnetic geometry. Here $\\epsilon$ 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 article, it is possible to calculate the long-wavelength components of the distribution functions and of the poloidal electric field to order $\\epsilon^2$. 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 co...

Calvo, Ivan

2012-01-01

349

Sub-wavelength energy trapping of elastic waves in a metamaterial.  

PubMed

Deep sub-wavelength focusing has been demonstrated for locally resonant metamaterials using electromagnetic and acoustic waves. The elastic equivalents of such objects are made of sub-wavelength resonating beams fixed to a two-dimensional plate, as presented here. Independent of a random or regular arrangement of the resonators, the metamaterial shows large bandgaps that are independent of the incident wave direction. Numerical simulations demonstrate that the insertion of a defect in the layout, as a shorter resonator, creates strong amplification of the wave-field on the defect. This energy trapping, which is localized on a spatial scale that is much smaller than the wavelength in the two-dimensional plate, leads to a >1 factor in terms of the local density of energy. PMID:25096146

Colombi, Andrea; Roux, Philippe; Rupin, Matthieu

2014-08-01

350

Complete Sequence of p07-406, a 24,179-Base-Pair Plasmid Harboring the blaVIM-7 Metallo-?-Lactamase Gene in a Pseudomonas aeruginosa Isolate from the United States?  

PubMed Central

An outbreak involving a Pseudomonas aeruginosa strain that was resistant to all tested antimicrobials except polymyxin B occurred in a hospital in Houston, TX. Previous studies on this strain showed that it possesses a novel mobile metallo-?-lactamase (MBL) gene, designated blaVIM-7, located on a plasmid (p07-406). Here, we report the complete sequence, annotation, and functional characterization of this plasmid. p07-406 is 24,179 bp in length, and 29 open reading frames were identified related to known or putatively recognized proteins. Analysis of this plasmid showed it to be comprised of four distinct regions: (i) a region of 5,200 bp having a Tn501-like mercuric resistance (mer) transposon upstream of the replication region; (ii) a Tn3-like transposon carrying a truncated integron with a blaVIM-7 gene and an insertion sequence inserted at the other end of this transposon; (iii) a region of four genes, upstream of the Tn3-like transposon, possessing very high similarity to plasmid pXcB from Xanthomonas campestris pv. citri commonly associated with plants; (iv) a backbone sequence similar to the backbone structure of the IncP group plasmid Rms149, pB10, and R751. This is the first plasmid to be sequenced carrying an MBL gene and highlights the amelioration of DNA segments from disparate origins, most noticeably from plant pathogens. PMID:18591274

Li, Hongyang; Toleman, Mark A.; Bennett, Peter M.; Jones, Ronald N.; Walsh, Timothy R.

2008-01-01

351

Complete Sequence of p07-406, a 24,179-base-pair plasmid harboring the blaVIM-7 metallo-beta-lactamase gene in a Pseudomonas aeruginosa isolate from the United States.  

PubMed

An outbreak involving a Pseudomonas aeruginosa strain that was resistant to all tested antimicrobials except polymyxin B occurred in a hospital in Houston, TX. Previous studies on this strain showed that it possesses a novel mobile metallo-beta-lactamase (MBL) gene, designated bla(VIM-7), located on a plasmid (p07-406). Here, we report the complete sequence, annotation, and functional characterization of this plasmid. p07-406 is 24,179 bp in length, and 29 open reading frames were identified related to known or putatively recognized proteins. Analysis of this plasmid showed it to be comprised of four distinct regions: (i) a region of 5,200 bp having a Tn501-like mercuric resistance (mer) transposon upstream of the replication region; (ii) a Tn3-like transposon carrying a truncated integron with a bla(VIM-7) gene and an insertion sequence inserted at the other end of this transposon; (iii) a region of four genes, upstream of the Tn3-like transposon, possessing very high similarity to plasmid pXcB from Xanthomonas campestris pv. citri commonly associated with plants; (iv) a backbone sequence similar to the backbone structure of the IncP group plasmid Rms149, pB10, and R751. This is the first plasmid to be sequenced carrying an MBL gene and highlights the amelioration of DNA segments from disparate origins, most noticeably from plant pathogens. PMID:18591274

Li, Hongyang; Toleman, Mark A; Bennett, Peter M; Jones, Ronald N; Walsh, Timothy R

2008-09-01

352

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

PubMed

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

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

2014-08-25

353

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

354

The chromosphere above sunspots at millimeter wavelengths  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

355

SHORT-WAVELENGTH MAGNETIC BUOYANCY INSTABILITY  

SciTech Connect

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

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

2013-04-01

356

Wavelength swept amplified spontaneous emission source.  

PubMed

We present a new, alternative approach to realize a wavelength swept light source with no fundamental limit to sweep speed. Amplified spontaneous emission (ASE) light alternately passes a cascade of optical gain elements and tunable optical bandpass filters. We show that for high sweep speeds, the control signal for the different filters has to be applied with a defined, precise phase delay on the order of nanoseconds, to compensate for the light propagation time between the filters and ensure optimum operation. At a center wavelength of 1300 nm sweep rates of 10 kHz, 100 kHz and 340 kHz over a sweep range of 100 nm full width and an average power of 50 mW are demonstrated. For application in optical coherence tomography (OCT), an axial resolution of 12 microm (air), a sensitivity of 120 dB (50 mW) and a dynamic range of 50 dB are achieved and OCT imaging is demonstrated. Performance parameters like coherence properties and relative intensity noise (RIN) are quantified, discussed and compared to the performance of Fourier Domain Mode Locked (FDML) lasers. Physical models for the observed difference in performance are provided. PMID:20372613

Eigenwillig, Christoph M; Biedermann, Benjamin R; Wieser, Wolfgang; Huber, Robert

2009-10-12

357

A wavelength tunable 2-ps pulse VECSEL  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

358

Nonlinear long-wavelength torsional Alfven waves  

NASA Astrophysics Data System (ADS)

Long-wavelength torsional (Alfven) waves in solar and stellar coronal structures experience geometrical amplification with height and hence are subject to nonlinear effects. We analyse this regime in frames the second order thin flux-tube approximation of Zhugzhda, which describes axisymmetric (sausage) magnetohydrodynamic perturbations of a straight untwisted and non-rotating magnetic flux-tube, representing e.g. a polar plume or a jet, or a coronal loop or a prominence filament. Attention is paid to the compressible motions nonlinearly induced by long-wavelength torsional waves of small, but finite amplitude. We obtained that propagating torsional waves induce compressible perturbations oscillating with double the frequency of the torsional waves. In contrast with plane shear Alfven waves, the amplitude of compressible perturbations is independent of the plasma-beta. Moreover, nonlinear evolution of torsional waves is not affected by the singularity appearing at the height when the local Alfven speed is equal to the sound speed. This result significantly reduces the efficiency of nonlinear cascade, and hence suggests that the present theories of the solar and stellar wind heating and acceleration by Alfven waves, based upon the plane wave theory, require modification.

Nakariakov, Valery

2012-07-01

359

Dual-wavelength active optical clock  

E-print Network

We experimentally realize the dual-wavelength active optical clock for the first time. As the Cs cell temperature is kept between 118 $^{\\circ }C$ and 144 $^{\\circ }C$, both the 1359 nm and the 1470 nm stimulated emission output of Cs four-level active optical clock are detected. The 1470 nm output linewidth of each experimental setup of Cs four-level active optical clock is measured to be 590 Hz with the main cavity length unstabilized. To stabilize the cavity length of active optical clock, the experimental scheme of 633 nm and 1359 nm good-bad cavity dual-wavelength active optical clock is proposed, where 633 nm and 1359 nm stimulated emission is working at good-cavity and bad-cavity regime respectively. The cavity length is stabilized by locking the 633 nm output frequency to a super-cavity with the Pound-Drever-Hall (PDH) technique. The frequency stability of 1359 nm bad-cavity stimulated emission output is then expected to be further improved by at least 1 order of magnitude than the 633 nm PDH system d...

Xu, Zhichao; Zhuang, Wei; Chen, Jingbiao

2014-01-01

360

Centroid wavelength of LEDs determined by broadband measurement  

Microsoft Academic Search

The centroid wavelength of a spectrum can be determined directly from the ratio of quantum and radiant flux values. This method is a fundamental spectral measurement since it satisfies the mathematical definition of centroid wavelength. Using broad-band methods for measuring quantum and radiant flux, the centroid wavelength can be determined from a ratio of photocurrents. This simple technique yields spectral

Carolyn F. Jones

1998-01-01

361

Wavelength tunable mode-locked quantum-dot laser  

NASA Astrophysics Data System (ADS)

We study the characteristics of wavelength tunable quantum-dot mode-locked lasers using a curved two-section device, external grating, and optical bandpass filter. Wide wavelength tunability is demonstrated due to the fact that the center wavelength of mode-locking is extended to excited state transitions as well as ground state transitions of the quantum-dot gain media.

Kim, Jimyung; Choi, Myoung-Taek; Lee, Wangkuen; Delfyett, Peter J., Jr.

2006-05-01

362

Analysis of Supportable Rates in Symmetric Blocking Wavelength Routers  

E-print Network

Analysis of Supportable Rates in Symmetric Blocking Wavelength Routers Can Emre Koksal EPFL School-- Constructing an n Ã? n non-blocking wavelength router using n Ã? n optical cross-connects may be impractical due requirements can be handled without a non-blocking router. In this paper, we study blocking wavelength routers

Koksal, Can Emre

363

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

364

Analysis and Calibration of Effective Wavelengths in SIM  

Microsoft Academic Search

The effective wavelength determination is the one of the key calibration issues for the Space Interferometry Mission (SIM). In order to obtain micro-arcsecond accuracy in astrometry, it is critical to have accurate wavelengths for the multiple spectral channels because the wavelength errors directly affect the fringe phase estimates. However, spectral response of SIM is a complicated and changing function, which

X. Pan; G. Worthey

2002-01-01

365

IMAGES OF GRADUAL MILLIMETER EMISSION AND MULTI--WAVELENGTH  

E-print Network

: a footpoint and a loop top source. Nonthermal emissions at microwave and hard X--ray wavelengths are analyzedIMAGES OF GRADUAL MILLIMETER EMISSION AND MULTI--WAVELENGTH OBSERVATIONS OF THE 1994 AUGUST 17 17 flare, the first flare imaged at millimeter (86 GHz) wavelengths. The temporal evolution

White, Stephen

366

Pulsed Digital Holographic Interferometry With 694- and 347-nm Wavelengths  

Microsoft Academic Search

A method for deformation analysis and shape measurement based on digital holography is presented. Two wavelengths, 694 and 347 nm, are used. The object is illuminated with the two wavelengths at the same time, and digital holograms are recorded on a CCD chip. The information corresponding to the two wavelengths is separated in the Fourier domain, and the phase corresponding

Giancarlo Pedrini; Hans J. Tiziani; Mikhail E. Gusev

2000-01-01

367

Absorption spectrum of DNA for wavelengths greater than 300 nm  

Microsoft Academic Search

Although DNA absorption at wavelengths greater than 300 nm is much weaker than that at shorter wavelengths, this absorption seems to be responsible for much of the biological damage caused by solar radiation of wavelengths less than 320 nm. Accurate measurement of the absorption spectrum of DNA above 300 nm is complicated by turbidity characteristic of concentrated solutions of DNA.

JOHN CLARK SUTHERLAND; KATHLEEN PIETRUSZKA GRIFFIN

1981-01-01

368

MILLIMETER-WAVELENGTH RADARS New Frontier in Atmospheric  

E-print Network

MILLIMETER-WAVELENGTH RADARS New Frontier in Atmospheric Cloud and Precipitation Research BY P. KOLLIAS, E. E. CLOTHIAUX, M. A. MILLER, B. A. ALBRECHT, G. L. STEPHENS, AND T. P. ACKERMAN Millimeter-wavelength at the SGP site of the ARM program. 1608 OCTOBER 2007| #12;T he choice of operating wavelength for a radar

Stephens, Graeme L.

369

Inter-domain Routing in Optical Networks with Wavelength Converters  

E-print Network

Inter-domain Routing in Optical Networks with Wavelength Converters Anteneh Beshir, Marcelo@ac.upc.edu Abstract--With the increasing deployment of wavelength- division multiplexing (WDM) optical networks evident. In order to increase efficiency by relaxing the wavelength continuity constraint in WDM optical

Kuipers, Fernando A.

370

A TUNABLE-OUTPUT WAVELENGTH CONVERTER BASED ON A SELF-  

E-print Network

A TUNABLE-OUTPUT WAVELENGTH CONVERTER BASED ON A SELF- SEEDED FABRY-PEROT LASER DIODE ABSTRACT: We report a new all-optical wavelength conversion scheme based on a self-seeded Fabry­Perot laser diode with a chirped fiber grating as the external cavity. This converter can convert the wavelength

Choi, Woo-Young

371

Dynamic Wavelength Routing in WDM Networks via Ant Colony Optimization  

E-print Network

Dynamic Wavelength Routing in WDM Networks via Ant Colony Optimization Ryan M. Garlick1 and Richard Methodist University, Dallas, TX 75275 USA Abstract. This study considers the routing and wavelength assignment problem (RWA) in optical wavelength-division multiplexed networks. The focus is dynamic traffic

Barr, Richard

372

Wavelength Assignment in Optical Networks with Imprecise Network State Information  

E-print Network

Wavelength Assignment in Optical Networks with Imprecise Network State Information Satyajeet Ahuja The University of Arizona {ahuja, krunz, srini}@ece.arizona.edu Abstract-- Efficient routing and wavelength assignment (RWA) in wavelength-routed all-optical networks is critical for achieving high efficiency over

Ramasubramanian, Srinivasan

373

Wavelength modulation spectroscopy using novel mechanical light chopper blade designs  

E-print Network

Wavelength modulation spectroscopy using novel mechanical light chopper blade designs Jayeeta wavelength modulation spectroscopy. The left and the right half of a beam emerging from a monochromator would have spectral distributions that are skewed to longer and shorter wavelengths about the central

Ghosh, Sandip

374

ATMOSPHERIC PHASE NOISE AND APERTURE SYNTHESIS IMAGING AT MILLIMETER WAVELENGTHS  

E-print Network

ATMOSPHERIC PHASE NOISE AND APERTURE SYNTHESIS IMAGING AT MILLIMETER WAVELENGTHS M. C. H. Wright wavelength aperture synthesis images is limited by atmospheric turbulence. Observing techniques and data of observations of astronomical sources. At optical wavelengths, the seeing is limited by tropospheric density

Militzer, Burkhard

375

Short wavelength topography on the inner-core boundary  

PubMed Central

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

Cao, Aimin; Masson, Yder; Romanowicz, Barbara

2007-01-01

376

Multi-wavelength Study Of The Cygnus Loop  

NASA Astrophysics Data System (ADS)

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

Leahy, Denis A.

2006-06-01

377

Multi-Wavelength Views of Messier 81  

NASA Technical Reports Server (NTRS)

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

[figure removed for brevity, see original site]

[figure removed for brevity, see original site]

[figure removed for brevity, see original site]

[figure removed for brevity, see original site]

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

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

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

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

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

2003-01-01

378

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. PMID:22559522

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

2012-01-01

379

Tunable optical tweezers for wavelength-dependent measurements  

NASA Astrophysics Data System (ADS)

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.; López-Mariscal, Carlos; Filgueira, Carly Levin; Huschka, Ryan; Halas, Naomi J.; Helmerson, Kristian

2012-04-01

380

Photoluminescence Study of Long Wavelength Superlattice Infrared Detectors  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

381

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

PubMed

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

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

382

Attacking practical quantum key distribution system with wavelength dependent beam splitter and multi-wavelength sources  

Microsoft Academic Search

Unconditional security of quantum key distribution protocol can be guaranteed by the basic property of quantum mechanics. Unfortunately, the practical quantum key distribution system always have some imperfections, and the practical system may be attacked if the imperfection can be controlled by the eavesdropper Eve. Applying the fatal security loophole introduced by the imperfect beam splitter's wavelength dependent optical property,

Hong-Wei Li; Shuang Wang; Jing-Zheng Huang; Wei Chen; Zhen-Qiang Yin; Fang-Yi Li; Zheng Zhou; Dong Liu; Yang Zhang; Guang-Can Guo; Wan-Su Bao; Zheng-Fu Han

2011-01-01

383

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. PMID:23899934

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

384

Geometrical measurement of cardiac wavelength in reaction-diffusion models.  

PubMed

The dynamics of reentrant arrhythmias often consists in multiple wavelets propagating throughout an excitable medium. An arrhythmia can be sustained only if these reentrant waves have a sufficiently short wavelength defined as the distance traveled by the excitation wave during its refractory period. In a uniform medium, wavelength may be estimated as the product of propagation velocity and refractory period (electrophysiological wavelength). In order to accurately measure wavelength in more general substrates relevant to atrial arrhythmias (heterogeneous and anisotropic), we developed a mathematical framework to define geometrical wavelength at each time instant based on the length of streamlines following the propagation velocity field within refractory regions. Two computational methods were implemented: a Lagrangian approach in which a set of streamlines were integrated, and an Eulerian approach in which wavelength was the solution of a partial differential equation. These methods were compared in 1D/2D tissues and in a model of the left atrium. An advantage of geometrical definition of wavelength is that the wavelength of a wavelet can be tracked over time with high temporal resolution and smaller temporal variability in an anisotropic and heterogeneous medium. The results showed that the average electrophysiological wavelength was consistent with geometrical measurements of wavelength. Wavelets were however often shorter than the electrophysiological wavelength due to interactions with boundaries and other wavelets. These tools may help to assess more accurately the relation between substrate properties and wavelet dynamics in computer models. PMID:25273213

Dupraz, Marie; Jacquemet, Vincent

2014-09-01

385

Performance of chip-size wavelength detectors.  

PubMed

Chip-size wavelength detectors are composed from a linear variable band-pass filter and a photodetector array. The filter converts the incident spectral distribution into a spatial distribution that is recorded by the detector array. This concept enables very compact and rugged spectrometers due to the monolithic integration of all functional components on a single chip. This type of spectrometer reveals its most convincing advantages through appropriate systems integration. We discuss the advantages of this concept for spectroscopy of light distributions that are hard to focus onto the entrance slit of a conventional spectrometer, namely large light emitting areas and moving point-like light sources. The excellent spectral performance of the system is demonstrated for both light input geometries. PMID:19547319

Schmidt, Oliver; Kiesel, Peter; Bassler, Michael

2007-07-23

386

Innovative Long Wavelength Infrared Detector Workshop Proceedings  

NASA Technical Reports Server (NTRS)

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

Grunthaner, Frank J.

1990-01-01

387

Short wavelength infrared hybrid focal plane arrays  

NASA Technical Reports Server (NTRS)

The employment of area focal plane arrays (FPA) has made it possible to obtain second generation infrared imaging systems with high resolution and sensitivity. The Short Wavelength Infrared (SWIR) region (1-2.5 microns) is of importance for imaging objects at high temperature and under conditions of reflected sunlight. The present investigation is concerned with electrooptical characterization results for 32 x 32 SWIR detector arrays and FPAs which are suitable for use in a prototype imaging spectrometer. The employed detector material is Hg(1-x)Cd(x)Te grown by liquid phase epitaxy on a CdTe transparent substrate. Attention is given to details of processing, the design of the detector array, the multiplexer, the fabrication of the hybrid FPA, and aspects of performance.

Vural, K.; Blackwell, J. D.; Marin, E. C.; Edwall, D. D.; Rode, J. P.

1983-01-01

388

Wavelength Prograimable Spectrophotometer For Individual Plant Studies  

NASA Astrophysics Data System (ADS)

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

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

1983-11-01

389

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

390

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

391

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

392

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

393

Atmospheric turbulence power spectral measurements to long wavelengths for several meteorological conditions  

NASA Technical Reports Server (NTRS)

Use of power spectral design techniques for supersonic transports requires accurate definition of atmospheric turbulence in the long wavelength region below the knee of the power spectral density function curve. Examples are given of data obtained from a current turbulence flight sampling program. These samples are categorized as (1) convective, (2) wind shear, (3) rotor, and (4) mountain-wave turbulence. Time histories, altitudes, root-mean-square values, statistical degrees of freedom, power spectra, and integral scale values are shown and discussed.

Rhyne, R. H.; Murrow, H. N.; Sidwell, K.

1976-01-01

394

Information-theoretic method for wavelength selection in bioluminescence tomography  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

395

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

NASA Technical Reports Server (NTRS)

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

Jani, Mahendra G. (Inventor)

1997-01-01

396

Attacking practical quantum key distribution system with wavelength dependent beam splitter and multi-wavelength sources  

E-print Network

Unconditional security of quantum key distribution protocol can be guaranteed by the basic property of quantum mechanics. Unfortunately, the practical quantum key distribution system always have some imperfections, and the practical system may be attacked if the imperfection can be controlled by the eavesdropper Eve. Applying the fatal security loophole introduced by the imperfect beam splitter's wavelength dependent optical property, we propose wavelength-dependent attacking model, which can be applied to almost all practical quantum key distribution systems with the passive state modulation and photon state detection after the practical beam splitter. Utilizing our attacking model, we experimentally demonstrate the attacking system based on practical polarization encoding quantum key distribution system with almost 100% success probability. Our result demonstrate that all practical devices require tightened security inspection for avoiding side channel attacks in practical quantum key distribution experimen...

Li, Hong-Wei; Huang, Jing-Zheng; Chen, Wei; Yin, Zhen-Qiang; Li, Fang-Yi; Zhou, Zheng; Liu, Dong; Zhang, Yang; Guo, Guang-Can; Bao, Wan-Su; Han, Zheng-Fu

2011-01-01

397

Attacking practical quantum key distribution system with wavelength dependent beam splitter and multi-wavelength sources  

E-print Network

Unconditional security of quantum key distribution protocol can be guaranteed by the basic property of quantum mechanics. Unfortunately, the practical quantum key distribution system always have some imperfections, and the practical system may be attacked if the imperfection can be controlled by the eavesdropper Eve. Applying the fatal security loophole introduced by the imperfect beam splitter's wavelength dependent optical property, we propose wavelength-dependent attacking model, which can be applied to almost all practical quantum key distribution systems with the passive state modulation and photon state detection after the practical beam splitter. Utilizing our attacking model, we experimentally demonstrate the attacking system based on practical polarization encoding quantum key distribution system with almost 100% success probability. Our result demonstrate that all practical devices require tightened security inspection for avoiding side channel attacks in practical quantum key distribution experimental realizations.

Hong-Wei Li; Shuang Wang; Jing-Zheng Huang; Wei Chen; Zhen-Qiang Yin; Fang-Yi Li; Zheng Zhou; Dong Liu; Yang Zhang; Guang-Can Guo; Wan-Su Bao; Zheng-Fu Han

2011-10-20

398

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

SciTech Connect

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

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

2012-05-01

399

Wavelength trimming by photoabsorption-included disordering for multiple-wavelength distributed-feedback laser arrays  

Microsoft Academic Search

In this letter, we describe a simple method to adjust the oscillation wavelength of distributed-feedback (DFB) lasers after the device fabrication without using any external active tuning. The method utilizes a permanent change of refractive index in the quantum well active layer induced by external laser beam irradiation. We have demonstrated 0.36 nm adjustment in a 1.55-?m ridge waveguide DFB

Tsurugi K. Sudoh; Mitsutaka Kumano; Yoshiaki Nakano; Kunio Tada

1997-01-01

400

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

NASA Astrophysics Data System (ADS)

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

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

2003-09-01

401

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

402

Using Guide Wavelengths to Assess Far-Infrared Laser Emissions  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

403

Optical wavelength selection for improved spectroscopic photoacoustic imaging?  

PubMed Central

Spectroscopic photoacoustic imaging has the potential to become a powerful tool that can estimate distributions of optically absorbing chromophores in the body. We have developed an algorithm to select imaging wavelengths for spectroscopic photoacoustics given the spectra of expected chromophores. The algorithm uses the smallest singular value of a matrix constructed from the absorption spectra as a criterion to remove extraneous wavelengths. The method performed significantly better than an approach where evenly spaced wavelengths were used in the presence of noise and wavelength-dependent attenuation of light in tissue. Finally, the algorithm was applied to photoacoustic imaging of a phantom containing indocyanine green dye and silica-coated gold nanorods, demonstrating significant improvements in the ability to estimate relative contrast agent concentrations compared to the case where evenly spaced wavelengths were chosen. In summary, our work provides a versatile framework to select optical wavelengths and evaluate sets of absorbers for spectroscopic photoacoustic imaging.

Luke, Geoffrey P.; Nam, Seung Yun; Emelianov, Stanislav Y.

2013-01-01

404

Short wavelength electron temperature gradient instability in toroidal plasmas  

SciTech Connect

The electron temperature gradient (ETG) driven mode in the very short wavelength region k{sub perpendicular}{rho}{sub e}>1 is identified with a gyrokinetic integral equation code in toroidal plasmas. This 'double-humped' growth rate of the conventional ETG and short wavelength ETG modes is attributed to the toroidal drift resonance mechanism and the nonmonotonic behavior of normalized real frequency as the poloidal wavelength varies. This instability provides a possibility existence of a kind of turbulence source with very small size of cells. However, the wavelength of the short wavelength ETG mode is too short and induced transport may be small unless there are inverse cascade effects. In addition, the critical threshold of electron temperature gradient (R/L{sub Te}){sub c} for the short wavelength ETG mode is higher than that for the conventional ETG mode.

Gao Zhe; Sanuki, H.; Itoh, K.; Dong, J.Q. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Southwestern Institute of Physics, Chengdu 610041 (China)

2005-02-01

405

Sub-wavelength infrared imaging of lipids  

PubMed Central

Infrared absorption spectroscopy of lipid layers was performed by combining optics and scanning probe microscopy. This experimental approach enables sub-diffraction IR imaging with a spatial resolution on the nanometer scale of 1, 2-dioleoyl-sn-glycero-3-phosphocholine lipid layers. PMID:21326633

Yarrow, Fiona; Kennedy, Eamonn; Salaun, Frederic

2011-01-01

406

A multi-wavelength LIF detection system  

NASA Astrophysics Data System (ADS)

We present preliminary results from a new pair of 16 channel photon-counting LIF detection systems designed for measurements of ion phase-space fluctuations using laser-induced fluorescence in an magnetized singly-ionized Argon plasma column. Conventional LIF detection systems use narrow-bandwidth interference filters to block background light. These filters have limitations in that they are normally limited to a single wavelength and must be of large diameter to work efficiently with light from a low f-number light-collection first-optic. Especially for experiments observing fluorescence on multiple transitions (or where fluorescence may be spread out over several decay paths) it is useful to be able to observe multiple transitions in the light from each light collection system. We describe a system consisting of two movable light-collecting periscopes where the collected light is expanded to 10 cm diameter beams which are analyzed by means of diffraction gratings and imaged onto 16 element photomuliplier tubes. In each of the channels the pulses are discriminated and counted with an adjustable dwell time. Because the light collection system is imaging, the multiple elements can be used to resolve multiple spatial points or multiple spectral lines.

Skiff, Fred; Drake, Dereth; Good, Tim

2011-11-01

407

Triple wavelength OEIC with improved optical responsivity  

NASA Astrophysics Data System (ADS)

OEICs for the advanced optical storage systems are required to be compatible with three kinds of disk systems, CD (?=780nm), DVD (?=650nm) and bluray disk (?=405nm). In this paper we present a triple wavelength OEIC with improved isolation areas between adjacent photodiodes, which minimize the dark areas for 405nm laser beam and also improve the effective photodiode areas for 650nm and 780nm laser beams. The isolation area is made not with pwell and pbur layer but with floated p+ for increasing the resistance between adjacent photodiodes. The IC was developed in 0.6um BiCMOS technology with integrated N+ finger type photodiodes. A 3-dB frequency response of 163MHz and a sensitivity of 22mV/uW at the blue laser spectral range (405nm) have been measured. A power consumption of 115mW at 5V supply is low enough for the commercial bluray pickup unit, and a chip area of 2.88mm2 is achieved. We have got good jitter performance of 6.8% at the commercial bluray systems.

Park, Deuk Hee; Go, Chae Dong; Jeong, Ha Woong; Kwon, Kyoung Soo; Kim, Byung-Sung

2009-02-01

408

Chandra Multi-wavelength Plane Survey  

NASA Astrophysics Data System (ADS)

The ChaMPlane Survey is designed to investigate the nature of the serendipitous X-ray point sources discovered by the Chandra X-ray Observatory, with its unprecedented spatial resolution, in the galactic plane. This multi-wavelength survey includes data from the Chandra archive and our own 840ks Chandra observations near the galactic center, as well as optical and infrared images and spectra we obtained from the Gemini-S, CTIO-4m, KPNO-4m, Magellan, MMT, WIYN and FLWO-1.5m. Its science goals are: 1) to determine the space density of faint accretion-powered binaries, mainly accreting white dwarfs in cataclysmic variables (CVs) and neutron stars or black holes in low-mass X-ray binaries in quiescence (qLMXBs) in the Galaxy; 2) to measure the Be High-Mass X-ray Binary (BeHMXB) density; and 3) to study the population of stellar coronal X-ray sources. We report our findings and summarize selected highlights from this legacy survey.

Zhao, Ping; Grindlay, Jonathan; Hong, Jaesub; Servillat, Mathieu; Van den Berg, Maureen

409

Laser Wavelength Dependency of Laser Supported Detonation  

NASA Astrophysics Data System (ADS)

The development of high power Neodymium glass (Nd:glass) laser allows for application in laser propulsion. The Nd:glass laser is one of a candidate of the driver for the propulsion. However, there is a lack of study with using the solid state laser. Previous studies found that plasma induced using the glass laser absorbs the laser energy during a short laser supported detonation (LSD) regime compared with CO2 lasers. To investigate a laser wavelengths dependency of LSD in comparison with the CO2 laser, we used plasma emission spectroscopy and measured the electron temperature and electron density. As a result, these parameters of the glass laser appear to be higher value than those for the CO2 laser plasma. Besides, the absorption depth behind the shock wave is longer than that one of the CO2 laser. The results reveal that the long depth absorbs the energy conversion efficiency at almost same order despite a short LSD duration, as compared with the CO2 laser.

Shimamura, Kohei; Michigami, Keisuke; Wang, Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Arakawa, Yoshihiro

2011-11-01

410

Array of Bolometers for Submillimeter- Wavelength Operation  

NASA Technical Reports Server (NTRS)

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

Bock, James; Turner, Anthony

2007-01-01

411

Accurate wavelength calibration method for flat-field grating spectrometers.  

PubMed

A portable spectrometer prototype is built to study wavelength calibration for flat-field grating spectrometers. An accurate calibration method called parameter fitting is presented. Both optical and structural parameters of the spectrometer are included in the wavelength calibration model, which accurately describes the relationship between wavelength and pixel position. Along with higher calibration accuracy, the proposed calibration method can provide information about errors in the installation of the optical components, which will be helpful for spectrometer alignment. PMID:21929865

Du, Xuewei; Li, Chaoyang; Xu, Zhe; Wang, Qiuping

2011-09-01

412

High-efficiency heater-loaded wavelength selectable laser  

Microsoft Academic Search

We have fabricated wavelength selectable lasers loaded with high-efficiency TiPt heater. Wavelength tuning by use of comb-shaped heater structure on DFB lasers array, temperature arise of SOA was suppressed, resulting in drastic improvement for the variation of optical output power at high temperature. Tuning range of 9.8 nm for wavelength selectable laser integrating four DFB lasers was realized with heater

T. Kurobe; T. Kimoto; T. Mukaihara; A. Kasukawa

2004-01-01

413

Observing with the ISO Short-Wavelength Spectrometer  

Microsoft Academic Search

The Short-Wavelength Spectrometer (SWS) is one of the four instruments on-board ESA's Infrared Space Observatory (ISO), launched on November 17, 1995. The spectrometer covers the wavelength range of 2.38 to 45.2mum with a spectral resolution ranging from 1000 to 2000. By inserting Fabry-Perot filters the resolution can be enhanced by a factor 20 for the wavelength range from 11.4 to

Graauw de Th; L. N. Haser; D. A. Beintema; P. R. Roelfsema; H. van Agthoven; L. Barl; H. E. G. Bekenkamp; A.-J. Boonstra; D. R. Boxhoorn; J. Cote; P. de Groene; C. van Dijkhuizen; S. Drapatz; J. Evers; H. Feuchtgruber; M. Frericks; R. Genzel; G. Haerendel; A. M. Heras; K. A. van der Hucht; T. van der Hulst; R. Huygen; H. Jacobs; G. Jakob; T. Kamperman; R. O. Katterloher; D. J. M. Kester; D. Kunze; D. Kussendrager; F. Lahuis; K. Leech; S. van der Lei; R. van der Linden; W. Luinge; D. Lutz; F. Melzner; P. W. Morris; D. van Nguyen; G. Ploeger; S. Price; A. Salama; S. G. Schaeidt; N. Sijm; C. Smoorenburg; J. Spakman; H. Spoon; M. Steinmayer; J. Stoecker; E. A. Valentijn; B. Vandenbussche; H. Visser; C. Waelkens; L. B. F. M. Waters; J. Wensink; P. R. Wesselius; E. Wiezorrek; E. Wieprecht; J. J. Wijnbergen; K. J. Wildeman; E. Young

1996-01-01

414

Dense Wavelength Division Multiplexing Networks: Principles and Applications  

Microsoft Academic Search

The very broad bandwidth of low-loss optical transmission in a single-mode fiber and the recent improvements in single-frequency tunable lasers have stimulated significant advances in dense wavelength division multiplexed optical networks. This technology, including wavelength-sensitive optical switching and routing elements and passive optical elements, has made it possible to consider the use of wavelength as another dimension, in addition to

Charles A. Brackett

1990-01-01

415

Supernova Remnants in the Multi-wavelength Era  

NASA Astrophysics Data System (ADS)

Supernova remnants (SNRs) influence and probe the properties of the gas and dust that compose the interstellar medium (ISM) into which they are born -- the ISM from which other stars and planets may form. The increasing prevalence of sensitive, high-resolution, large-scale surveys offers an avenue to progress our understanding of SNRs, more accurately count sources, and more precisely constrain the stellar contribution to the ISM of the Milky Way. Here I will outline a few case studies in which data from multiple wavebands are brought to bare on issues of source classification, environment, morphology, and evolutionary phase. In examining just these few cases, I find a misclassified SNR, a pair whose unusual morphologies can be explained by a partial transition to the radiative phase, and provide further insight into a set of SNR candidates which, if confirmed, may be amongst the youngest in the Galaxy. These examples demonstrate the potential of including existing multi-wavelength data in the analysis of SNRs.

Robbins, William; Gaensler, B. M.; Murphy, T.; Reeves, S.; Moss, V.; Green, A. J.

2013-01-01

416

Terahertz detectors for long wavelength multi-spectral imaging.  

SciTech Connect

The purpose of this work was to develop a wavelength tunable detector for Terahertz spectroscopy and imaging. Our approach was to utilize plasmons in the channel of a specially designed field-effect transistor called the grating-gate detector. Grating-gate detectors exhibit narrow-linewidth, broad spectral tunability through application of a gate bias, and no angular dependence in their photoresponse. As such, if suitable sensitivity can be attained, they are viable candidates for Terahertz multi-spectral focal plane arrays. When this work began, grating-gate gate detectors, while having many promising characteristics, had a noise-equivalent power (NEP) of only 10{sup -5} W/{radical}Hz. Over the duration of this project, we have obtained a true NEP of 10{sup -8} W/{radical}Hz and a scaled NEP of 10{sup -9}W/{radical}Hz. The ultimate goal for these detectors is to reach a NEP in the 10{sup -9{yields}-10}W/{radical}Hz range; we have not yet seen a roadblock to continued improvement.

Lyo, Sungkwun Kenneth; Wanke, Michael Clement; Reno, John Louis; Shaner, Eric Arthur; Grine, Albert D.

2007-10-01

417

Wavelength resolved UV photodesorption and photochemistry of CO2 ice.  

PubMed

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

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

2014-01-01

418

Four-Photon Quantum Interferometry at a Telecom Wavelength  

E-print Network

We report the experimental demonstration of four-photon quantum interference using telecom-wavelength photons. Realization of multi-photon quantum interference is essential to linear optics quantum information processing and measurement-based quantum computing. We have developed a source that efficiently emits photon pairs in a pure spectrotemporal mode at a telecom wavelength region, and have demonstrated the quantum interference exhibiting the reduced fringe intervals that correspond to the reduced de Broglie wavelength of up to the four photon `NOON' state. Our result should open a path to practical quantum information processing using telecom-wavelength photons.

Masahiro Yabuno; Ryosuke Shimizu; Yasuyoshi Mitsumori; Hideo Kosaka; Keiichi Edamatsu

2011-12-09

419

Dual-Wavelength Internal-Optically-Pumped Semiconductor Laser Diodes  

NASA Astrophysics Data System (ADS)

Dual-wavelength laser sources have various existing and potential applications in wavelength division multiplexing, differential techniques in spectroscopy for chemical sensing, multiple-wavelength interferometry, terahertz-wave generation, microelectromechanical systems, and microfluidic lab-on-chip systems. In the drive for ever smaller and increasingly mobile electronic devices, dual-wavelength coherent light output from a single semiconductor laser diode would enable further advances and deployment of these technologies. The output of conventional laser diodes is however limited to a single wavelength band with a few subsequent lasing modes depending on the device design. This thesis investigates a novel semiconductor laser device design with a single cavity waveguide capable of dual-wavelength laser output with large spectral separation. The novel dual-wavelength semiconductor laser diode uses two shorter- and longer-wavelength active regions that have separate electron and hole quasi-Fermi energy levels and carrier distributions. The shorter-wavelength active region is based on electrical injection as in conventional laser diodes, and the longer-wavelength active region is then pumped optically by the internal optical field of the shorter-wavelength laser mode, resulting in stable dual-wavelength laser emission at two different wavelengths quite far apart. Different designs of the device are studied using a theoretical model developed in this work to describe the internal optical pumping scheme. The carrier transport and separation of the quasi-Fermi distributions are then modeled using a software package that solves Poisson's equation and the continuity equations to simulate semiconductor devices. Three different designs are grown using molecular beam epitaxy, and broad-area-contact laser diodes are processed using conventional methods. The modeling and experimental results of the first generation design indicate that the optical confinement factor of the longer-wavelength active region is a critical element in realizing dual-wavelength laser output. The modeling predicts lower laser thresholds for the second and third generation designs; however, the experimental results of the second and third generation devices confirm challenges related to the epitaxial growth of the structures in eventually demonstrating dual-wavelength laser output.

Green, Benjamin

420

Solar energy converter employing a fluorescent wavelength shifter  

SciTech Connect

A solar converter is described which consists of: (a) a zinc selenide fluorescent wavelength shifter including a fluorescent zinc selenide substrate having anti-reflecting coatings on opposite sides thereof and operative to convert predetermined wavelengths of solar radiation to radiation of different wavelengths for transmission to an adjacent solar cell, the fluorescent wavelength shifter having a response spectra extending between about 0.3 and 0.47 micrometers wavelength; (b) a gallium arsenide or aluminum gallium arsenide solar cell having a pn junction therein and an anti-reflective coating on one surface and further having a response spectra extending from approximately 0.47 micrometers to approximately 0.9 micrometers and operative to convert sunlight radiation of these wavelengths to output power; and (c) means for adhesively bonding one of the anti-reflectingly coated sides of the fluorescent wavelength shifter to the anti-reflective coating of the solar cell and for simultaneously providing good optical matching and transparency between these anti-reflecting coatings, whereby the pn junction of the solar cell converts radiation wavelengths within the fluorescence spectrum of the wavelength shifter to useful output power and thereby enhances and optimizes the solar conversion efficiency of the solar converter.

Garlick, G.F.J.

1986-04-22

421

Wavelength division multiplexed passive optical networks with colorless light sources.  

E-print Network

??The emerging internet services need the future passive optical networks (PONs) to provide considerably increased capacity for subscribers. Wavelength division multiplexed (WDM) PON is expected… (more)

Xu, Zhao Wen.

2010-01-01

422

Investigating short wavelength correlated errors on low resolution mode altimetry  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

423

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

PubMed Central

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

Fallah, F