Sample records for vims wavelength scale

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

    Microsoft Academic Search

    Jason W. Barnes; Robert H. Brown; Laurence Soderblom; Bonnie J. Buratti; Christophe Sotin; Sebastien Rodriguez; Stephane Le Mouèlic; Kevin H. Baines; Roger Clark; Phil Nicholson

    2007-01-01

    We present global-scale maps of Titan from the Visual and Infrared Mapping Spectrometer (VIMS) instrument on Cassini. We map at 64 near-infrared wavelengths simultaneously, covering the atmospheric windows at 0.94, 1.08, 1.28, 1.6, 2.0, 2.8, and 5 ?m with a typical resolution of 50 km\\/pixel or a typical total integration time of 1 s. Our maps have five to ten

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

    USGS Publications Warehouse

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

    2007-01-01

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

  3. Wavelength Scaling of High Harmonic Generation Efficiency

    SciTech Connect

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

    2009-08-14

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

  4. The “VIM” users group

    Microsoft Academic Search

    F. William Rambo

    1975-01-01

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

  5. The Surface of Titan as Seen by the Cassini VIMS Investigation

    Microsoft Academic Search

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

    2006-01-01

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

  6. Scale Invariant Processing Using Multiple Wavelengths

    NASA Astrophysics Data System (ADS)

    Knopp, Jerome

    1990-04-01

    A method for optical correlation is discussed that can use a liquid crystal television in the filter plane. Conventional binary phase-only filtering is compared with a binary amplitude approach that uses the sum of the intensities from multiple binary amplitude correlations. One parallel processing implementation is presented that uses three binary amplitude filters, each filter using a different wavelength of light. A computer simulation using synthetic filters shows that a binary amplitude multiple wavelength filter (BANE) that uses ternary phase correction works as well as a conventional binary phase-only filter when used as a scale invariant filter and as a synthetic estimation filter.

  7. Effective wavelength scaling of rectangular aperture antennas.

    PubMed

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

    2015-04-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  9. Predicting Spar VIM Using CFD

    Microsoft Academic Search

    Samuel Holmes

    2008-01-01

    Recent work toward predicting spar vortex induced motion (VIM) with computational fluid dynamics (CFD) suggests that such simulations can anticipate many aspects of spar response and thus supplement tow tank experiments and other design methods. However, the results also highlight a number of challenges as well. The spar VIM problem is characterized by very high Reynolds numbers, geometric complexity including

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

    USGS Publications Warehouse

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

    2008-01-01

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

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

    Microsoft Academic Search

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

    2007-01-01

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

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

    Microsoft Academic Search

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

    2003-01-01

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

  13. Long-period gratings in wavelength-scale microfibers.

    PubMed

    Xuan, Haifeng; Jin, Wei; Liu, Shujing

    2010-01-01

    We report the fabrication of long-period gratings (LPGs) in wavelength-scale microfibers with diameters from 1.5 to 3 microm. The LPGs were fabricated by use of a femtosecond IR laser to periodically modify the surface of the fibers. These LPGs have grating periods of a few tens of micrometers, much smaller than those in conventional optical fibers. A compact 10-period LPG with a device length of only approximately 150 microm demonstrated a strong resonant dip of >20 dB around 1330 nm. These microfiber LPGs would be useful in-fiber components for microfiber-based devices, circuits, and sensors. PMID:20664681

  14. Scaling laws for photoelectron holography in the midinfrared wavelength regime.

    PubMed

    Huismans, Y; Gijsbertsen, A; Smolkowska, A S; Jungmann, J H; Rouzée, A; Logman, P S W M; Lépine, F; Cauchy, C; Zamith, S; Marchenko, T; Bakker, J M; Berden, G; Redlich, B; van der Meer, A F G; Ivanov, M Yu; Yan, T-M; Bauer, D; Smirnova, O; Vrakking, M J J

    2012-07-01

    Midinfrared strong-field laser ionization offers the promise of measuring holograms of atoms and molecules, which contain both spatial and temporal information of the ion and the photoelectron with subfemtosecond temporal and angstrom spatial resolution. We report on the scaling of photoelectron holographic interference patterns with the laser pulse duration, wavelength, and intensity. High-resolution holograms for the ionization of metastable xenon atoms by 7-16???m light from the FELICE free electron laser are presented and compared to semiclassical calculations that provide analytical insight. PMID:23031101

  15. gamma-Ray wavelength standard for atomic scales.

    PubMed

    Shvyd'ko, Y V; Lerche, M; Jäschke, J; Lucht, M; Gerdau, E; Gerken, M; Rüter, H D; Wille, H C; Becker, P; Alp, E E; Sturhahn, W; Sutter, J; Toellner, T S

    2000-07-17

    The wavelength of the 57Fe Mössbauer radiation is measured with a relative uncertainty of 0.19 ppm by using almost exact Bragg backscattering from a reference silicon crystal. Its value is determined as lambda(M) = 0.860 254 74(16)x10(-10) m. The corresponding Mössbauer photon energy is E(M) = 14 412.497(3) eV. The wavelength of the 57Fe Mössbauer radiation is easily reproducible with an accuracy of at least 10(-11)lambda(M) and could be used as a length standard of atomic dimensions. PMID:10991324

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  17. Scaled intense laseratom physics: the long wavelength T. O. CLATTERBUCK{, C. LYNGA {*, P. COLOSIMOy,

    E-print Network

    Martin, James D. D.

    and cross-correlation measure- ments using ionization of noble gas atoms have been performed on harmonicScaled intense laser­atom physics: the long wavelength regime T. O. CLATTERBUCK{, C. LYNGA° {*, P-binding energy atom (caesium) excited by an intense mid-infrared (3­4 mm) laser pulse. The long- wavelength

  18. Charge and wavelength scaling of RF photoinjector designs

    Microsoft Academic Search

    J. Rosenzweig; E R Colby

    1995-01-01

    The optimum design of an emittance compensated rf photoinjector is very complicated and time-consuming, relying heavily on multi-particle simulations without good analytical models as a guide. Emittance compensated designs which have been developed, however, can be used to generate other designs with no additional effort if the original design is scaled correctly. This paper examines the scaling of rf photoinjector

  19. Angular scatter ultrasound imaging of wavelength scale targets.

    PubMed

    Lacefield, J C; von Ramm, O T

    2000-10-01

    A bistatic ultrasound imaging system is demonstrated that uses two 32-element linear phased array transducers oriented at an angle of 40 degrees to one another. The system simultaneously acquires and displays in real time one conventional backscatter image and one "angular scatter" image formed using side-scattered echoes from the same B-mode sector region. Experiments are presented that show differences in the magnitudes of backscatter and angular scatter signals acquired from three nylon monofilaments with diameters less than one wavelength and from soft tissue structures in vivo. The relative magnitudes of angular scatter signals from the monofilaments are qualitatively consistent with a theoretical analysis of acoustic scattering from elastic cylinders. Larger tissue features are more clearly defined in angular scatter images. This result is attributed to the orientation of specularly reflecting surfaces and the expected influence of scattering angle on the system's sensitivity to different scatterer spacings. PMID:11051517

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

    Microsoft Academic Search

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

    2011-01-01

    The surface properties of the icy bodies in the saturnian system have been investigated by means of the Cassini-VIMS (Visual Infrared Mapping Spectrometer) hyperspectral imager which operates in the 0.35–5.1?m wavelength range. In particular, we have analyzed 111 full disk hyperspectral images of Rhea ranging in solar phase between 0.08° and 109.8°. These data have been previously analyzed by Filacchione

  1. [Multi-wavelength spectral aerosol scale height in inshore in contrast with that in inland].

    PubMed

    Han, Yong; Rao, Rui-Zhong; Wang, Ying-Jian

    2009-01-01

    In the present paper, based on the exponential attenuation of atmospheric aerosol concentration with height, so using continuous spectrum sun-photometer, forward scatter visibility sensor and hygrothermograph, the authors measured the atmosphere column optical characteristic and plane spectral extinction coefficient on earth on the base of two experiments at some edge of ocean at the same time, respectively, set up the calculative method of multi-wavelength spectral aerosol scale height. Firstly, the authors obtained atmospheric horizontal extinction coefficient with forward scattering visibility sensor, which subtracted molecular extinction coefficient, and could get aerosol extinction coefficient near ground; Then, selecting sea salt model, using OPAC software, the authors also could calculate the aerosol extinction coefficient under different humidity (0%, 50%, 70%, 80%, 90%, 95%, 98% and 99%) and different wavelength (400, 450, 500, 550, 600, 650, 700 and 750 nm), the aerosol extinction coefficient was detected by visibility sensor, using interpolation method, respectively; Finally, using the data of atmospheric columniation optical thickness detected by continuous spectral sun-photometer and subtracted molecular optical thickness corresponding wavelengths were accounted out by Modtran 4. 0. The authors obtained the characteristic of spectral aerosol scale height of visible light (wavelength is 400, 440, 532, 550 and 690 nm): with wavelength increments, and spectral aerosol scale height was found to decline neither in inland nor in inshore in China; Spectral aerosol scale height in winter is higher than in summer in southeast inshore; but spectral aerosol scale height in winter is smaller in summer than in inland. PMID:19385200

  2. Improvements to the accuracy of the IUE wavelength scales in high dispersion

    NASA Astrophysics Data System (ADS)

    Turnrose, B. E.; Harvel, C. A.; Bohlin, R. C.

    The data base of Pt-Ne emission lines used to calibrate the IUE high dispersion wavelength scales was scrutinized to improve the internal consistency of the adopted laboratory wavelength values and provide a homogeneous, documented line list, which IUE Guest Observers may use to evaluate quantitatively those Pt-Ne spectra taken to calibrate their data. After deletion of incorrect or inappropriate data in the old data base (lines with incorrect wavelength assignments; lines which are too faint, too bright, or blended; lines which fall near reseau marks, etc.) and the addition of several new entries, a total of 172 Pt-Ne lines for the SWP camera and 164 Pt-Ne lines for the LWR camera are now used for routine wavelength calibration in the high dispersion mode.

  3. Large-scale patterns on the Sun observed in the millimetric wavelength range

    Microsoft Academic Search

    B. Vrsnak; S. Pohjolainen; S. Urpo; H. Terasranta; R. Brajsa; V. Ruždjak; Z. Mouradian; S. Jurac

    1992-01-01

    The nature and behaviour of large-scale patterns on the solar surface, indicated by the areas of brightness-temperature depressions in the millimetric wavelength range, is studied. A large sample of 346 individual, low-temperature regions (LTRs) was employed to provide reliable statistical evidence. An association of 99% was found between the locations of LTRs and the large-scale magnetic field inversion lines, and

  4. Scaling of Ne-like x-ray laser schemes to short wavelength

    SciTech Connect

    Rosen, M.D.; London, R.A.; Hagelstein, P.L.

    1988-03-01

    The driver and target parameters required to extend the successful results from an exploding foil Ne-like-Se soft x-ray laser at 206 A towards wavelengths of 40 A are investigated. The power requirements are found to scale as lambda/sup -4/, which is quite costly. The principal constraint is the refraction of the x-ray laser beam in these high density, single pass, exploding foil targets. Correcting mirrors or nonrefracting target designs could reduce this costly scaling.

  5. VIMS Molluscan Ecology Oyster Reef Community Research

    NSDL National Science Digital Library

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

  6. Particle Size Distribution in Saturn's C Ring and Cassini Division from VIMS and UVIS Stellar Occultations

    NASA Astrophysics Data System (ADS)

    Jerousek, R. G.; Colwell, J. E.; Nicholson, P. D.; Hedman, M. M.; Esposito, L. W.; Harbison, R. A.

    2014-12-01

    More than sixty VIMS (Visual and Infrared Mapping Spectrometer) and more than one hundred UVIS (Ultraviolet Imaging Spectrograph) photometric measurements of stellar occultation profiles have been collected since Cassini's orbit insertion in June, 2004. The UVIS HSP (High Speed Photometer) collects photons with an effective wavelength ?eff = 0.15 ?m within a 6.4 mrad x 6.0 mrad field of view while, when operating in occultation mode, the VIMS instrument collects photons with ?eff = 2.9 ?m incident on a single pixel of angular dimensions 0.5 mrad x 0.25 mrad. Starlight is diffracted through an angle of ? ~ 1.22?eff/2a by ring particles of radius a. Due to the smaller angular dimensions of the VIMS pixel and longer measured wavelength, starlight can be diffracted out of its field of view by small particles (a~ 9 mm) and not replaced by diffraction from neighboring ring particles. This reduction in the measured intensity of starlight can lead to higher optical depths in VIMS occultations than in UVIS occultations. Because self-gravity wakes introduce additional differences in measured optical depths due to differences in viewing geometry, here we compare measurements in the C ring and Cassini Division where self-gravity wakes are not present. We find evidence of sub-cm particles in both the C Ring and Cassini Division. Minimum particles in the C Ring are relatively constant with radial distance from Saturn, with a mean of ~6mm. There is an increasing trend in minimum particle size outward through the Cassini Division.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  8. HOE/lensless matched spatial filter wavelength-scaling correlator. [Holographic Optical Element

    NASA Technical Reports Server (NTRS)

    Shen, M.; Casasent, D.; Luu, T. K.; Feng, B.

    1980-01-01

    A scaling correlator optical pattern recognition system is described in which a lensless matched spatial filter (with the second Fourier transform lens and the matched spatial filter recorded on the same plate) is used with a first Fourier transform lens that is also an holographic optical element. The matched spatial filter is recorded at one wavelength and correlation is obtained at a second wavelength. Experimental demonstration and output correlation SNR data are reported, together with a comparison of the system's noise level using conventional optics and holographic elements.

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

    PubMed Central

    Lassaux, Patricia; Traoré, Daouda A. K.; Loisel, Elodie; Favier, Adrien; Docquier, Jean-Denis; Sohier, Jean Sébastien; Laurent, Clémentine; Bebrone, Carine; Frère, Jean-Marie; Ferrer, Jean-Luc; Galleni, Moreno

    2011-01-01

    The metallo-?-lactamase VIM-4, mainly found in Pseudomonas aeruginosa or Acinetobacter baumannii, was produced in Escherichia coli and characterized by biochemical and X-ray techniques. A detailed kinetic study performed in the presence of Zn2+ at concentrations ranging from 0.4 to 100 ?M showed that VIM-4 exhibits a kinetic profile similar to the profiles of VIM-2 and VIM-1. However, VIM-4 is more active than VIM-1 against benzylpenicillin, cephalothin, nitrocefin, and imipenem and is less active than VIM-2 against ampicillin and meropenem. The crystal structure of the dizinc form of VIM-4 was solved at 1.9 Å. The sole difference between VIM-4 and VIM-1 is found at residue 228, which is Ser in VIM-1 and Arg in VIM-4. This substitution has a major impact on the VIM-4 catalytic efficiency compared to that of VIM-1. In contrast, the differences between VIM-2 and VIM-4 seem to be due to a different position of the flapping loop and two substitutions in loop 2. Study of the thermal stability and the activity of the holo- and apo-VIM-4 enzymes revealed that Zn2+ ions have a pronounced stabilizing effect on the enzyme and are necessary for preserving the structure. PMID:21149620

  10. Development of vehicle intelligent monitoring system (VIMS)

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  11. Engineering light at the sub-wavelength scale using silicon photonics

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  13. Wavelength-scale imaging of trapped ions using a phase Fresnel lens.

    PubMed

    Jechow, A; Streed, E W; Norton, B G; Petrasiunas, M J; Kielpinski, D

    2011-04-15

    A microfabricated phase Fresnel lens was used to image ytterbium ions trapped in a radio frequency Paul trap. The ions were laser cooled close to the Doppler limit on the 369.5 nm transition, reducing the ion motion so that each ion formed a near point source. By detecting the ion fluorescence on the same transition, near-diffraction-limited imaging with spot sizes of below 440 nm (FWHM) was achieved. To our knowledge, this is the first demonstration of wavelength-scale imaging of trapped ions and the highest imaging resolution ever achieved with atoms in free space. PMID:21499360

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

    NASA Astrophysics Data System (ADS)

    Botey, Muriel; Herrero, Ramon; Staliunas, Kestutis

    2010-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    USGS Publications Warehouse

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

    2004-01-01

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

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

    E-print Network

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

    2011-10-14

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

  18. Control of Modes Coupling, Selection and Enhancement in Wavelength-Scale Optical Microcavity Structures: Applications to Microlasers and Biosensing

    Microsoft Academic Search

    Svetlana V. Boriskina; V. Karazin

    2006-01-01

    Recent advances and remaining challenges in spectral engineering of wavelength-scale optical microcavity structures supporting modes with narrow linewidths, wide mode spacing, directional emission, and greatly enhanced sensitivity to the environmental changes will be reviewed. General recipes for efficient control and manipulation of modes coupling and selective enhancement in such structures will be discussed

  19. Spread of bla VIM -1-producing e. coli in a university hospital in Greece. Genetic analysis of the integron carrying the bla VIM -1 metallo-?-lactamase gene

    Microsoft Academic Search

    Efstathia V Scoulica; Ioannis K Neonakis; Achilleas I Gikas; Yannis J Tselentis

    2004-01-01

    BlaVIM-1 gene was detected in four Escherichia coli clinical isolates with both reduced susceptibility to carbapenems and an ESBL phenotype. The VIM-1 determinant was located within the variable region of a Class I integron along with a 6?-N-aminoglycoside acetytransferase gene (aac(6?)-Ib) and it could be transferred by conjugation. In all four clinical isolates the VIM-1 gene cassette presented a characteristic

  20. 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

    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

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

    PubMed

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

    2015-05-26

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

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

    Microsoft Academic Search

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

    2004-01-01

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

  3. High-Resolution Enceladus Atlas and Compositional Maps derived from Cassini ISS and VIMS

    NASA Astrophysics Data System (ADS)

    Roatsch, Thomas; Kersten, Elke; Wählisch, Marita; Hoffmeister, Angelika; Stephan, Katrin; Jaumann, Ralf

    2010-05-01

    The first version of the high-resolution Enceladus atlas was released in 2006 [1]. The Cassini Imaging Science Sub-system (ISS) acquired more high-resolution images (< 1 km/pixel) during five close flybys of Enceladus in 2008 and 2009. We combined these images with lower-resolution coverage taken between 2007 and 2009 to improve the high-resolution global mosaic of Enceladus. The whole mosaic was shifted by 3.5° to the West to be consistent with the IAU definition of the prime meridian location. This new global mosaic is the baseline for the second release of the high-resolution Enceladus atlas that consists again of 15 tiles mapped at a scale of 1:500,000. We proposed 29 additional names for features which will be used as nomenclature in the atlas. We are awaiting validation of the new nomenclature by the IAU. The new release of the atlas will be made available to the public through CICLOPS (http://ciclops.org) and PDS (http://pds.jpl.nasa.gov). The Cassini Visual and Infrared Imaging Spectrometer (VIMS) observed Enceladus during a couple of flybys between 2005 and 2009. This gave us the possibility to combine these data into a global VIMS mosaic. Based on this mosaic maps of Enceladus' spectral properties could be derived. Thus, global maps illustrating the spatial variations of the absorption band depth of water ice were calculated, which are indicative of varying sizes of the water ice particles [2]. The authors gratefully acknowledge the planning and operation work of their colleagues from the Cassini-ISS team lead by Carolyn Porco and from the Cassini-VIMS team lead by Robert Brown. [1] Roatsch, Th. et al., High-resolution Enceladus atlas derived from Cassini-ISS images. Planetary Space Sciences 56, 109-116, 2008. [2] Jaumann, R., Stephan, K., Hansen, G.B., Clark, R.N., Buratti, B.J., Brown, R.H., Baines, K.H., Newman, S.F., Bellucci, G., Filacchione, G., Coradini, A., Cruikshank, D.P., Griffith, C.A., Hibbitts, C.A., McCord, T.B., Nelson, R.M., Nicholson, P.D., Sotin, C., and Wagner, R., 2008: Distribution of icy particles across Enceladus' surface as derived from Cassini-VIMS measurements. Icarus 193.

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

    E-print Network

    Granados, Eduardo

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

  5. A global-scale model of aerosol backscatter at CO2 wavelengths for satellite-based lidar sensors

    NASA Technical Reports Server (NTRS)

    Bowdle, David A.

    1986-01-01

    The status of a global-scale model of background aerosol backscatter cross-sections at CO2 wavelengths is described. The model needs, strategy, concept, parameters, and capabilities are addressed, and the data base is discussed, concluding data selection, CO2 backscatter measurements, aerosol optical measurements, aerosol microphysical measurements, water vapor measurements, and data analysis. Strong evidence is reported for a 'universal' background tropospheric aerosol population. Typical background backscatter values at CO2 wavelengths appear to be about 3 x 10 to the -11th to 8 x 10 to the -11th/m/sr. Background signatures are evident in most aerosol data sets which have global-scale coverage in space or time.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  7. Theoretical Study of Light Trapping in Nanostructured Thin Film Solar Cells Using Wavelength-Scale Silver Particles.

    PubMed

    Dabirian, Ali; Taghavinia, Nima

    2015-07-15

    We propose and theoretically evaluate a plasmonic light trapping solution for thin film photovoltaic devices that comprises a monolayer or a submonolayer of wavelength-scale silver particles. We systematically study the effect of silver particle size using full-wave electromagnetic simulations. We find that light trapping is significantly enhanced when wavelength-scale silver particles rather than the ones with subwavelength dimensions are used. We demonstrate that a densely packed monolayer of spherical 700 nm silver particles enhances integrated optical absorption under standard air mass 1.5 global (AM1.5G) in a 7 ?m-thick N719-sensitized solar cell by 40% whereas enhancement is smaller than 2% when 100 nm ones are used. Superior performance of wavelength-scale silver particles is attributed to high-order whispering gallery modes that they support. These modes scatter the light over a wider angular range, hence increasing the density of both waveguide and resonance modes within the dye-sensitized layer. PMID:26135021

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

    PubMed

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

    2014-03-01

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

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

    Microsoft Academic Search

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

    2006-01-01

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

  10. VIM-D salvage chemotherapy in Hodgkin's disease

    Microsoft Academic Search

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

    1990-01-01

    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

  11. Cassini-VIMS Observations of Saturn's Rings at SOI

    Microsoft Academic Search

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

    2004-01-01

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

  12. Cassini-VIMS Observations of Saturn's Rings at SOI

    NASA Astrophysics Data System (ADS)

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

    2004-11-01

    Following the Cassini spacecraft's Saturn Orbit Insertion (SOI) burn on 1 July 2004, the Visual and Infrared Mapping Spectrometer (VIMS) obtained near-infrared spectra from 0.9 to 5.1 ? m in two continuous radial scans across the unlit side of the rings, at ranges of ˜30,000 km. The first scan covers the outer C and inner B rings at a phase angle, ? = 82o and an emission angle, e = 47o, while the second covers the Cassini Division and entire A ring at ? = 59o and e = 63o. The solar incidence angle was 114o and the radial resolution of both scans is 15-20 km, with sampling intervals of 2-3 km. Structurally, the rings appear to have changed little, if at all, since the Voyager observations in 1980/81 and the 28 Sgr occultations in 1989. This similarity extends even to the quasi-irregular structure which characterizes the inner B ring on scales of ˜100 km. Spectrally, all regions of the rings scanned are dominated by water ice, with prominent absorption bands at 1.55, 2.0 and 3.0 ? m, as well as weaker bands at 1.04 and 1.25 ? m seen primarily in the A and B rings. The ice bands are strongest in the middle A ring, somewhat weaker in the B ring, and much weaker in the C ring and Cassini Division. Locally, however, the fractional band depths appear to be independent of optical depth, suggesting that the light diffusely transmitted through the rings at moderate phase angles is dominated by single scattering. Regionally, the transitions between the C and B rings and between the Cassini Division and A ring are marked by gradual changes in band depth over radial distances of a few thousand km, perhaps indicative of ballistic redistribution of material. A broad reflectance maximum at 3.6 ? m, characteristic of ice grain sizes less than 100 ? m, is prominent everywhere but particularly strong in the outermost parts of the A ring, exterior to the Encke Gap. Besides water ice, the most noteworthy spectral feature is a broad, shallow absorption in the 0.9-1.8 ? m region which we tentatively attribute to Fe-bearing minerals, most likely silicates. This feature is seen primarily in the outer C ring and the Cassini Division, but like the ice band depths it pays only modest attention to structural boundaries. This work was supported by NASA and ESA under contracts with the Cassini-Huygens Project.

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

    PubMed

    Hoover, Brian G; Gamiz, Victor L

    2006-02-01

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

  14. 1.3 mm WAVELENGTH VLBI OF SAGITTARIUS A*: DETECTION OF TIME-VARIABLE EMISSION ON EVENT HORIZON SCALES

    SciTech Connect

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

    2011-02-01

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

  15. CASSINI VIMS AND ALTIMETER JOINT STUDY OF TITAN SURFACE. S. Rodriguez1 , M. Crapeau2

    E-print Network

    Paris-Sud XI, Université de

    CASSINI VIMS AND ALTIMETER JOINT STUDY OF TITAN SURFACE. S. Rodriguez1 , M. Crapeau2 , S. Le Department, USA. Introduction: The joint NASA-ESA-ASI Cassini- Huygens mission reached the saturnian system of an unclouded low atmos- phere [2,3]. Onboard the Cassini spacecraft, the VIMS (Visual and Infrared Mapping

  16. Cloud features and zonal wind measurements of Saturn's atmosphere as observed by Cassini/VIMS

    E-print Network

    Choi, David S.

    Cloud features and zonal wind measurements of Saturn's atmosphere as observed by Cassini/VIMS D. S Cassini's Visual and Infrared Mapping Spectrometer (VIMS), focusing on the meteorology of the features. Comparison with previously constructed profiles from Voyager and Cassini imaging data reveals broad

  17. 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

  18. The Saturnian satellite Rhea as seen by Cassini VIMS

    USGS Publications Warehouse

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

    2012-01-01

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

  19. Wavelength scaling of spiral patterns formed by granular media underneath a rotating fluid

    PubMed

    Zoueshtiagh; Thomas

    2000-05-01

    A spiral pattern formed by granular media underneath a rotating fluid is discussed. Results from a cellular-automaton model are compared to experimental data, and are found to reproduce experimentally observed scalings. A theoretical argument predicting these scalings on the basis of the existence of a critical threshold condition is advanced. It is suggested that the pattern is probably not associated with a hitherto unknown flow instability, as has been speculated previously. It appears that the pattern constitutes some rotating analog to sand ripples in nonrotating systems. PMID:11031612

  20. Remote sensing applications in marine science programs at VIMS

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  1. Saturn B and C ring studies at multiple wavelengths

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    USGS Publications Warehouse

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

    2009-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    PubMed

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

    2013-07-01

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

  5. Stellar occultation experiment with the CASSINI VIMS instrument

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

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

    USGS Publications Warehouse

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

    2010-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  8. Statistical Clustering and Compositional Modeling of Iapetus VIMS Spectral Data

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    It has long been known that the surfaces of Saturn's major satellites are predominantly icy objects [e.g. 1 and references therein]. Since 2004, these bodies have been the subject of observations by the Cassini-VIMS (Visual and Infrared Mapping Spectrometer) experiment [2]. Iapetus has the unique property that the hemisphere centered on the apex of its locked synchronous orbital motion around Saturn has a very low geometrical albedo of 2-6%, while the opposite hemisphere is about 10 times more reflective. The nature and origin of the dark material of Iapetus has remained a question since its discovery [3 and references therein]. The nature of this material and how it is distributed on the surface of this body, can shed new light into the knowledge of the Saturnian system. We apply statistical clustering [4] and theoretical modeling [5,6] to address the surface composition of Iapetus. The VIMS data evaluated were obtained during the second flyby of Iapetus, in September 2007. This close approach allowed VIMS to obtain spectra at relatively high spatial resolution, ~1-22 km/pixel. The data we study sampled the trailing hemisphere and part of the dark leading one. The statistical clustering [4] is used to identify statistically distinct spectra on Iapetus. The composition of these distinct spectra are evaluated using theoretical models [5,6]. We thank Allan Meyer for his help. This research was supported by an appointment to the NASA Postdoctoral Program at the Ames Research Center, administered by Oak Ridge Associated Universities through a contract with NASA. [1] A, Coradini et al., 2009, Earth, Moon & Planets, 105, 289-310. [2] Brown et al., 2004, Space Science Reviews, 115, 111-168. [3] Cruikshank, D. et al Icarus, 2008, 193, 334-343. [4] Marzo, G. et al. 2008, Journal of Geophysical Research, 113, E12, CiteID E12009. [5] Hapke, B. 1993, Theory of reflectance and emittance spectroscopy, Cambridge University Press. [6] Shkuratov, Y. et al. 1999, Icarus, 137, 235-246.

  9. The spectrum of a Saturn ring spoke from Cassini\\/VIMS

    Microsoft Academic Search

    E. D'Aversa; G. Bellucci; P. D. Nicholson; M. M. Hedman; R. H. Brown; M. R. Showalter; F. Altieri; F. G. Carrozzo; G. Filacchione; F. Tosi

    2010-01-01

    On 2008, July, the Cassini\\/VIMS spectrometer detected spokes on the Saturn's B ring for the first time. These are the first measurements of the complete reflectance spectrum of the spokes in a wide spectral range (0.35–0.51 ?m). Here we will focus on a single broad-shaped spoke, imaged by VIMS on July, 9. Radiative transfer modeling supports a pure water ice

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  13. Compositional radial variability in the Saturn's system observed by Cassini-VIMS (INVITED) (Invited)

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    From ~2200 disk-integrated observations of the moons and several radial mosaics of the rings acquired by Cassini-VIMS, we have found very striking differences among the various objects in the Saturn system, ranging from the almost uncontaminated and water ice-rich surfaces of Enceladus and Calypso to the metal/organic-rich and red surfaces of Iapetus’ leading hemisphere and Phoebe. In this framework, we have investigated the relationships between the satellite surface composition, orbital distance from Saturn, and average density. In the F ring environment, the inner satellites (Prometheus, Pandora, Janus and Epimetheus) have average surface water ice abundances similar to particles in the C ring and CD but with much less reddening contaminant. Although their orbits are close to the F-ring, Prometheus and Pandora have very evident differences in surface composition: Prometheus is very water ice-rich but at the same time very red at VIS wavelengths. These properties make it very similar to A-B ring particles while Pandora is bluer. Moving outward, the effects of E ring particles, generated by Enceladus plumes become evident as they contaminate surfaces from Mimas to Rhea. We have found some differences between the Lagrangian moons of Tethys: Calypso is much more water ice-rich and bluer with respect to Telesto. Among the outer satellites, moving from Hyperion, to Iapetus and Phoebe, a linear trend is observed relating the decrease of water ice to reddening, with Hyperion resulting as the reddest object of the population. As a further step, we have investigated how these surface properties are correlated with the average densities and dimensions of the moons. Mid-sized icy satellites are in a transition regime, between the high pressure/high density ice phases of Titan and the high porosity/irregular shapes of the minor moons and Hyperion. Low-density (0.5-1.0 g cm-3) satellites show different trends with Prometheus, Pandora and Calypso characterized by high abundance of surface water ice while Janus and Hyperion are ice-poorer and redder. Higher densities, ranging between 1.0 and 1.6 g cm-3, are typical of the regular satellites which, with the exclusion of Dione and Rhea, have similar water ice abundances. For Iapetus, if we exclude the exogenic dark material covering the leading hemisphere, we find water ice abundances similar to the remaining regular satellites. Finally Phoebe has the greatest density (1.65 g cm-3) of the population and the least water ice abundance. Since VIS-IR spectra can probe surface composition only in a very shallow layer a few wavelengths deep, VIMS measurements are affected by the presence of exogenic particles and processes. However these measurements, when coupled with the results coming from other Cassini orbiter experiments and theoretical models, promise to help us unveil the formation and evolution history of the Saturn’s system. This research is supported by an ASI grant

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

    NASA Astrophysics Data System (ADS)

    Guo, Yicheng; Giavalisco, Mauro; Ferguson, Henry C.; Cassata, Paolo; Koekemoer, Anton M.

    2012-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

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

    USGS Publications Warehouse

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

    2003-01-01

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

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

    PubMed Central

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  19. Infections with VIM-1 Metallo-?-Lactamase-Producing Enterobacter cloacae and Their Correlation with Clinical Outcome?

    PubMed Central

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

    2009-01-01

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

  20. Molecular typing indicates an important role for two international clonal complexes in dissemination of VIM-producing Pseudomonas aeruginosa clinical isolates in Hungary

    Microsoft Academic Search

    Balázs Libisch; Joseph Watine; Boglárka Balogh; Mária Gacs; Mónika Muzslay; Gitta Szabó; Miklós Füzi

    2008-01-01

    VIM metallo-?-lactamase-producing serotype O11 or O12 Pseudomonas aeruginosa isolates infecting or colonising 19 patients from seven hospitals were reported in Hungary between 2003 and 2005. In this study we characterised VIM-producing Pseudomonas spp. clinical isolates from two novel locations in Hungary; we identified three new blaVIM carrying integron types and the presence of the blaVIM-2 allele in Hungary. By applying

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

    Microsoft Academic Search

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

    2010-01-01

    Electrodynamical model of a classical distributed Bragg reflector (DBR) consisting of alternating quarter-wave layers of high\\u000a and low permittivity is considered at the plane wave normal incidence. Reflective characteristics of DBR possessing absorption\\u000a loss in constituting layers are analysed via correct wavelength-scale boundary problem solution by the method of single expression\\u000a (MSE). Analysis of optical field and power flow density

  2. University/Classified Non-Exempt OT Compensation The College of William and Mary/VIMS Banner ID # : Date

    E-print Network

    Swaddle, John

    University/Classified Non-Exempt OT Compensation The College of William and Mary/VIMS Employer: W&M VIMS Banner ID # : Date: Employee Name: Last First Middle University/Classified Non-Exempt Overtime Compensation: Employees in a university/classified position that is designated as non-exempt under the Fair

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

    NASA Astrophysics Data System (ADS)

    Lamy, L.

    2011-10-01

    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.

  4. Multi-Wavelength Observations of the Spatio-Temporal Evolution of Solar Flares with AIA/SDO: I. Universal Scaling Laws of Space and Time Parameters

    E-print Network

    Aschwanden, Markus J; Liu, Kai

    2013-01-01

    We extend a previous statistical solar flare study of 155 GOES M- and X-class flares observed with AIA/SDO (Aschwanden 2012) to all 7 coronal wavelengths (94, 131, 171, 193, 211, 304, 335 \\ang) to test the wavelength-dependence of scaling laws and statistical distributions. Except for the 171 and 193 \\ang\\ 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 $V$, fractal dimension $D_2$), temporal (flare durations $T$), and spatio-temporal parameters (diffusion coefficient $\\kappa$, spreading exponent $\\beta$, and maximum expansion velocities $v_{max}$) 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., $N(L) \\propto L^{-3}$, $N(A) \\propto A^{-2}$, $N(V) \\propto V^{-5/3}$, $N(T) \\propto T^{-2}$, $D_2=3/2$, for a Euclidean dimension $d=3$. Empirical...

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

    NASA Technical Reports Server (NTRS)

    Baines, Kevin H.; Brown, R. H.; Matson, Dennis L.; Nelson, R. M.; Buratti, B. J.; Bibring, J. P.; Langevin, Y.; Sotin, C.; Carusi, A.; Coradini, Angioletta

    1992-01-01

    The scientific objectives and observational scenarios of the Cassini/Visual Infrared Mapping Spectrometer (VIMS) Mission at Titan are addressed. The VIMS represents a powerful and effective means to both investigate, in four dimensions (latitude, longitude, altitude, and time), Titan's atmospheric structure and to map the near infrared spectral character of Titan's surface. Its broad spectral coverage from 0.35 to 5.1 micrometers together with its significant spectral resolution allows it to determine minor constituent distributions and cloud optical/microphysical properties from the surface to several hundred km. A promising means of obtaining high vertical resolution stratospheric profiles of hydrocarbons, oxides, and hazes via stellar occultation observations is discussed.

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

    USGS Publications Warehouse

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

    2009-01-01

    Joint Cassini VIMS and RADAR SAR data of ???700-km-wide Hotei Regio reveal a rich collection of geological features that correlate between the two sets of images. The degree of correlation is greater than anywhere else seen on Titan. Central to Hotei Regio is a basin filled with cryovolcanic flows that are anomalously bright in VIMS data (in particular at 5 ??m) and quite variable in roughness in SAR. The edges of the flows are dark in SAR data and appear to overrun a VIMS-bright substrate. SAR-stereo topography shows the flows to be viscous, 100-200 m thick. On its southern edge the basin is ringed by higher (???1 km) mountainous terrain. The mountains show mixed texture in SAR data: some regions are extremely rough, exhibit low and spectrally neutral albedo in VIMS data and may be partly coated with darker hydrocarbons. Around the southern margin of Hotei Regio, the SAR image shows several large, dendritic, radar-bright channels that flow down from the mountainous terrain and terminate in dark blue patches, seen in VIMS images, whose infrared color is consistent with enrichment in water ice. The patches are in depressions that we interpret to be filled with fluvial deposits eroded and transported by liquid methane in the channels. In the VIMS images the dark blue patches are encased in a latticework of lighter bands that we suggest to demark a set of circumferential and radial fault systems bounding structural depressions. Conceivably the circular features are tectonic structures that are remnant from an ancient impact structure. We suggest that impact-generated structures may have simply served as zones of weakness; no direct causal connection, such as impact-induced volcanism, is implied. We also speculate that two large dark features lying on the northern margin of Hotei Regio could be calderas. In summary the preservation of such a broad suite of VIMS infrared color variations and the detailed correlation with features in the SAR image and SAR topography evidence a complex set of geological processes (pluvial, fluvial, tectonic, cryovolcanic, impact) that have likely remained active up to very recent geological time (<104 year). That the cryovolcanic flows are excessively bright in the infrared, particularly at 5 ??m, might signal ongoing geological activity. One study [Nelson, R.M., and 28 colleagues, 2009. Icarus 199, 429-441] reported significant 2-??m albedo changes in VIMS data for Hotei Arcus acquired between 2004 and 2006, that were interpreted as evidence for such activity. However in our review of that work, we do not agree that such evidence has yet been found.

  7. The Deep Lamp Project: An Investigation of the Precision and Accuracy of the Echelle Wavelength Scales of Space Telescope Imaging Spectrograph

    NASA Astrophysics Data System (ADS)

    Ayres, Thomas R.

    2008-08-01

    The precision and absolute accuracy of the echelle mode wavelength scales of Space Telescope Imaging Spectrograph (STIS) are investigated. The method is to measure deep exposures of the onboard Pt/Cr-Ne hollow cathode calibration lamp. The standard deviation of emission spots from their laboratory wavelengths in a single image is a measure of the internal precision of the pipeline-assigned scales. The average shift of the image as a whole is a measure of the absolute accuracy. While systematic patterns can be identified in all four echelle modes (E140M, E140M, E230M, and E230H), the overall precision (even without compensating for long-range trends with ?) is excellent: of order one-tenth of the resolution element (?~600 and 300 m s-1, for medium- [M] and high- [H] resolution modes, respectively). Furthermore, the absolute accuracy and its repeatability (assessed in a time series of WAVECAL images) is of order a remarkable 100 m s-1, aside from one of the E230M modes (secondary tilt ?2269) that shows a systematic offset 10 times larger. The excellent precision of the STIS echelle wavelengths could be improved by adding higher order terms to the biquadratic polynomial currently implemented in the CALSTIS pipeline. On the other hand, the existing small distortions might be resolved more naturally by a ``physical instrument model,'' currently under development by the Space Telescope European Coordinating Facility's STIS Calibration Enhancement Project.

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

    PubMed

    Mezeme, M Essone; Brosseau, C

    2012-07-30

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

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

    SciTech Connect

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

    2013-09-20

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

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

    Microsoft Academic Search

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

    2010-01-01

    Saturn's B ring demarcates the inner edge of the dynamically fascinating Cassini Division, replete with eccentric and circular ringlets and gaps. We present kinematical models for ringlets and gaps in the Cassini Division, and the outer edge of the B ring, from more than 100 individual Cassini occultations using RSS, VIMS, and UVIS instruments. Recent investigations of the B ring

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

    Microsoft Academic Search

    Thomas B. McCord; Paul Hayne; Jean-Philippe Combe; Gary B. Hansen; Jason W. Barnes; Sébastien Rodriguez; Stéphane Le Mouélic; E. Kevin H. Baines; Bonnie J. Buratti; Christophe Sotin; Philip Nicholson; Ralf Jaumann; Robert Nelson

    2008-01-01

    The surface composition of Titan is of great importance for understanding both the internal evolution of Titan and its atmosphere. The Visual and Infrared Mapping Spectrometer (VIMS) investigation on Cassini is observing Titan from 0.35 to 5.11 ?m with spatial resolution down to a few kilometers during each flyby of the spacecraft as it orbits Saturn. Our search for spectral

  12. Exploring Methods to Rule Out Surface Compositional Types on Titan Using Cassini VIMS T20 Data

    NASA Astrophysics Data System (ADS)

    Buratti, B. J.; Pitman, K. M.; Brown, R. H.; Barnes, J. W.; Baines, K.; Clark, R.; Jaumann, R.; Nicholson, P.; Sotin, C.

    2007-03-01

    During the Oct. 25, 2006, Cassini T20 Titan flyby, VIMS observed Bohai Sinus, a dune-free area exhibiting apparent color differences between materials. Our goal is to develop methods to exclude possible non-H2O endmember candidates for this region.

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

    E-print Network

    in the concepts that support integrated coastal zone management. The workshop presentation will introduce the audi integrate key elements paramount to land use management within a coastal community. The goal is to provideVirginia Wetlands Report Center for Coastal Resources Management www.ccrm.vims.edu Volume 25, Issue

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

    E-print Network

    Virginia Wetlands Report Center for Coastal Resources Management www.ccrm.vims.edu Volume 25, Issue 2 A Biannual Publication Focused on Virginia Wetland Issues and Training Fall 2010 The Center for a website update was provided by DEQ's Virginia Coastal Zone Management Program through a grant from NOAA

  15. 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 28, Issue 1 An Annual Publication Focused on Virginia Wetland Issues and Training Spring 2013 The Virginia Wetlands Report is an annual publication of the Wetlands Program at the Virginia Institute of Marine

  16. 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 27, Issue 1 A Biannual Publication Focused on Virginia Wetland Issues and Training Spring 2012 As the impacts with the latest information on expected future trends in sea level in southeastern Virginia. In this issue

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

    USGS Publications Warehouse

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

    2006-01-01

    The Visual Infrared Mapping Spectrometer (VIMS) onboard the CASSINI spacecraft obtained new spectral data of the icy satellites of Saturn after its arrival at Saturn in June 2004. VIMS operates in a spectral range from 0.35 to 5.2 ??m, generating image cubes in which each pixel represents a spectrum consisting of 352 contiguous wavebands. As an imaging spectrometer VIMS combines the characteristics of both a spectrometer and an imaging instrument. This makes it possible to analyze the spectrum of each pixel separately and to map the spectral characteristics spatially, which is important to study the relationships between spectral information and geological and geomorphologic surface features. The spatial analysis of the spectral data requires the determination of the exact geographic position of each pixel on the specific surface and that all 352 spectral elements of each pixel show the same region of the target. We developed a method to reproject each pixel geometrically and to convert the spectral data into map projected image cubes. This method can also be applied to mosaic different VIMS observations. Based on these mosaics, maps of the spectral properties for each Saturnian satellite can be derived and attributed to geographic positions as well as to geological and geomorphologic surface features. These map-projected mosaics are the basis for all further investigations. ?? 2006 Elsevier Ltd. All rights reserved.

  18. 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

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

    E-print Network

    and those hosted by VIMS. Integrated Coastal & Shoreline Management Guidance Integrated coastal zone and economic issues. The disconnect between current management practices and the concept of integrated coastal zone management is exemplified by the disjoint management of coastal resources that promotes partially

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

    E-print Network

    working with living shoreline partners to continue these conversations about research, monitoring & Development Council, VIMS Watch a video about this project http://www.youtube.com/watch?v=FilWV1Ro0Jw Coming · Chincoteague National Wildlife Refuge ­ US Fish & Wildlife Service, The Nature Conservancy, VMRC Is your new

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  2. Mode analysis of surface plasmon metal-dielectric-metal nanowire array waveguide at sub-wavelength scale

    NASA Astrophysics Data System (ADS)

    Tian, Jinping; Liang, Xijing; Zhang, Caijiao; Li, Hongjuan

    2013-05-01

    A kind of surface plasmon waveguide (SPW) formed from metal-dielectric-metal nanowire array is proposed. The mode properties are analyzed. Theoretical analysis reveals that at appropriate geometrical parameters, the optimal mode properties such as longer propagation length and better sub-wavelength mode confinement can be obtained. It is found that when the center dielectric nanowire is replaced by gain medium, the propagation length can be extended obviously without changing the effective mode index and mode size clearly. The studied waveguide could be an interesting alternative to the application of realizing high density photonic devices integration, nanoscale photonic circuits and sensors.

  3. Analysis of selected Cassini VIMS and RADAR data over the surface of Titan through multivariate classification methods

    NASA Astrophysics Data System (ADS)

    Tosi, F.; Orosei, R.; Seu, R.; Filacchione, G.; Coradini, A.; Capaccioni, F.; Cerroni, P.; Adriani, A.; Moriconi, M. L.; Cassini RADAR Team; Cassini Science Team

    2007-12-01

    We have searched through Cassini/VIMS hyperspectral cubes, selecting those data which have convenient viewing geometry and which overlap with Cassini/RADAR footprints having comparable ground resolution.\

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  5. Looking at some equatorial regions on Titan using Cassini/VIMS and RADAR data: a case for changes in surface properties

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Lopes, Rosaly; Hirtzig, Mathieu; Bratsolis, Emmanuel; Drossart, Pierre; Le Mouélic, Stephane; Rodriguez, Sebastien; Jaumann, Ralf; Stephan, Katrin; Bampasidis, Georgios; Sotin, Christophe; Brown, Robert

    2014-05-01

    Titan, Saturn's largest moon, has a complex, dynamic and -in some aspects- Earth-like atmosphere and surface. Data from the remote sensing instruments on board Cassini, particularly VIMS and the RADAR, have shown the presence of diverse terrains on the surface, suggesting exogenic and endogenic processes [1;2;3]. In this research we focus on some equatorial regions that have been identified as possibly subject to changes, having particular spectral properties and possibly being the strongest cryovolcanic candidate regions, that is: Sotra Patera, Hotei Regio and Tui Regio [1,4,5]. We use VIMS data, to which we apply a state-of-the-art Principal Component Analysis (PCA) and radiative transfer methods [4;7] with updated parameterization for the spectroscopic data and infer the surface albedos of all of these regions, that we interpret in terms of possible surface composition and morphology combining with information from RADAR data. Indeed, by including despeckled SAR images we identify geomorphological units and investigate spatial and temporal geological relationships [6]. This combination provides us with implications on the surface composition of different units. By looking at evolution with time, we find that two of these regions show albedo changes with time, for Tui Regio from 2005-2009 (darkening) and Sotra Patera from 2005-2006 (brightening) at all wavelengths, indicating that dynamical processes control the regions, compatible with their complex morphology. In conclusion, we also associate radiometry and topographic data with the compositional information from VIMS to derive constraints on the chemical composition and the geology of the surface and finally the nature of these regions. References: [1] Lopes, R.M.C., et al.: JGR, 118, 416-435; [2] Solomonidou, A., et al.: PSS, 70, 77-104; [3] Moore, J.M., and Howard, A.D.: GRL, 37, L22205, 2010; [4] Solomonidou, A., et al.: submitted(a); [5] Solomonidou, A., et al.: submitted(b); [6] Bratsolis, E., et al.: PSS, 61, 108-113; [7] Hirtzig, M., et al.: Icarus, 226, 470-486.

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

    USGS Publications Warehouse

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

    2007-01-01

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

  7. Control of single-master multi-slave manipulator system using VIM

    Microsoft Academic Search

    K. Kosuge; J. Ishikawa; K. Furuta; M. Sakai

    1990-01-01

    A single-master, multiple-slave manipulator system and its task-oriented control using VIM (virtual internal model) are proposed. By using this system, the operator no longer has to consider how to control the slave arms in coordination, so the operator can concentrate on his\\/her task during the operation. An experimental single-master, multislave manipulator system with two slave arms, each of which has

  8. Sources of diversity of carbapenem resistance levels in Klebsiella pneumoniae carrying blaVIM-1

    Microsoft Academic Search

    A. Loli; L. S. Tzouvelekis; E. Tzelepi; A. Carattoli; A. C. Vatopoulos; P. T. Tassios; V. Miriagou

    2006-01-01

    Objectives: To elucidate the mechanisms responsible for the diversity of b-lactam resistance phenotypes among isolates of a VIM-1-producing Klebsiella pneumoniae (VPKP) strain that is endemic in Greek hospitals. Methods: Five VPKP clinical isolates were studied. MICs of b-lactams were determined by agar dilution. PFGE of XbaI-digested genomic DNA was used for typing. Profiles of outer membrane proteins (OMPs) were determined

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  10. Ultracompact and large-scale power splitters on silicon-based two-dimensional photonic crystals at near-infrared wavelengths

    NASA Astrophysics Data System (ADS)

    Zhao, Yuzhou; Zhang, Yao; Li, Baojun; Chaudhari, Bharat S.; Chua, Soo J.

    2006-02-01

    An optical power splitter with one input and three output ports is proposed and demonstrated for near-infrared applications in the wavelength range of 2.3 to 2.5 µm. The device operates on the principle of directional coupling by introducing photonic crystal line-defect waveguides. Its functionality and performance have been numerically investigated and simulated by the finite-difference time-domain method. By cascading two 1×3-structure power splitters, a large-scale optical power splitter with one input and five output ports is achieved. The simulated results show that the 1×5 large-scale power splitter can also perform 1×2, 1×3, and 1×4 functions. The required optical power from each of the output waveguides can be easily controlled by adjusting the coupling length of interaction for photonic crystal line-defect waveguides. The total length of the 1×5 power splitter is 40 µm, which is significantly less than that of the conventional non-photonic-crystal power splitter. This is a promising device for future ultracompact and large-scale nanophotonic integrated circuits.

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

    Microsoft Academic Search

    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

    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

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

    PubMed

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

    2007-02-01

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

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

    PubMed Central

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

    2012-01-01

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

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

    USGS Publications Warehouse

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

    2008-01-01

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

  15. Investigation of VIM, IMP, NDM-1, KPC AND OXA-48 enzymes in Enterobacteriaceae strains.

    PubMed

    Demir, Yelda; Zer, Yasemin; Karaoglan, Ilkay

    2015-05-01

    Gram-negative bacteria especially Enterobacteriaceaespecies have become an increasing etiologic agent of nosocomial infections. The development of resistance to carbapenems have become an increasing problem in the treatment of nosocomial infections. Especially carbapenamases are common for Enterobacteriaceae strains. This study was performed to detect the types of carbapenemases in Enterobacteriaceaestrains isolated from various clinical samples. Enterobacteriaceae species were isolated from urine, blood, tracheal aspirates, wound, and other respiratory samples. Susceptibility of isolates to imipenem, meropenem and ertapenem was tested. Carbapenemase genes were studied using HyplexSuperBug ID kit. VIM (1-13), IMP (1-22), NDM-1, KPC(1-10) and OXA-48 genes were investigated. Ninety-five isolates of Enterobacteriaceae spp. were included in the study. Sixty isolates were resistant to imipenem, meropenem and ertapenem and 20 isolates were found resistant to imipenem or ertapenem while 15 were susceptible to all carbapenems. Among the isolates with carbapenem resistance, 57 were positive for one carbapenemase gene and susceptible isolates did not have carbapenemase gene. OXA-48 was found in 49 of the isolates (86%), NDM-1 in 6 (10.5%) isolates, VIM in 2 isolates. IMP and KPC gene loci were not identified. Carbapenemase genes play a crucial rolein the development and spread of resistant strains. PMID:26051720

  16. Metallo-beta-lactamase VIM-2 in Pseudomonas aeruginosa isolates from a cystic fibrosis patient.

    PubMed

    Cardoso, Olga; Alves, Ana Florinda; Leitão, Rui

    2008-04-01

    The increased incidence of Pseudomonas aeruginosa isolated from patients with cystic fibrosis (CF) along with an increase in its multidrug resistance makes therapeutic management very problematic. Careful identification and accurate studies of susceptibility to antibiotics are critical for improving therapeutic measures and for facilitating our understanding of the epidemiology of this pathogen. Fifteen P. aeruginosa isolates obtained from five CF children in the Paediatric Hospital of Coimbra were studied. Isolates from a female patient were resistant to all agents tested except colistin. A VIM-2 enzyme inserted in integron In58 was detected, and this isolate presented a unique random amplified polymorphic DNA (RAPD) type. Others isolates were susceptible to beta-lactams, and each isolate had a different RAPD type. VIM-2 confers resistance to the majority of beta-lactams and is associated with other gene cassettes coding for enzymes that inactivate aminoglycosides. Person-to-person transmission of these isolates is not well understood, therefore it is important to design infection control policies to avoid acquisition and dissemination of multiresistant strains. PMID:18276121

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

    NASA Astrophysics Data System (ADS)

    Dybkaer, René

    2010-06-01

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

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

    PubMed Central

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

    2012-01-01

    In the literature, only three Brevundimonas diminuta environmental isolates carrying metallo-?-lactamase genes were recently published. However, so far, no B. diminuta clinical isolates carrying these carbapenem resistance genes have been described. Here we report the first VIM-2 metallo-?-lactamase-producing B. diminuta clinical isolate obtained from an immunocompromised patient. PMID:22692741

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

    PubMed Central

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

    2014-01-01

    Antibiotic resistance, especially due to ?-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

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

    USGS Publications Warehouse

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

    2010-01-01

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

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

    USGS Publications Warehouse

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

    2010-01-01

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

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

    USGS Publications Warehouse

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

    2009-01-01

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

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

    USGS Publications Warehouse

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

    2008-01-01

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

  4. Characterization of Class 1 Integrons from Pseudomonas aeruginosa That Contain the blaVIM-2 Carbapenem-Hydrolyzing  Lactamase Gene and of Two Novel Aminoglycoside Resistance Gene Cassettes

    Microsoft Academic Search

    LAURENT POIREL; THIERRY LAMBERT; SALIH TURKOGLU; ESTHEL RONCO; JEAN-LOUIS GAILLARD; PATRICE NORDMANN

    2001-01-01

    Two clonally unrelated Pseudomonas aeruginosa clinical strains, RON-1 and RON-2, were isolated in 1997 and 1998 from patients hospitalized in a suburb of Paris, France. Both isolates expressed the class B carbapenem-hydrolyzing b-lactamase VIM-2 previously identified in Marseilles in the French Riviera. In both isolates, the blaVIM-2 cassette was part of a class 1 integron that also encoded aminoglycoside-modifying enzymes.

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

    PubMed Central

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

    2014-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    A unique focal plane array (FPA) assembly combining both electronic and optical components in a single hermetically sealed hybrid package has been designed to meet the performance requirements imposed on the focal plane assembly in the Visual and Infrared Mapping Spectrometer (VIMS) for the Mars Observer (MO) mission. Inside the FPA package is a configuration of three multiplexed linear arrays containing 320 detector elements, a combination of Si and InSb, allowing continuous spectral coverage from 0.35 to 5.14 microns. An optical subassembly consisting of two spectral order-sorting filters with intrinsic field-of-view apertures requiring critical optical alignment is also internal to the hybrid. Several engineering issues arose during the MO/VIMS FPA development phase which had challenging design ramifications. FPA performance requirements, design approach, and critical issues are discussed.

  7. Carbapenem-resistant Klebsiella pneumoniae harbouring blaKPC-3 and blaVIM-2 from central Italy.

    PubMed

    Perilli, Mariagrazia; Bottoni, Carlo; Grimaldi, Alessandro; Segatore, Bernardetta; Celenza, Giuseppe; Mariani, Maurizio; Bellio, Pierangelo; Frascaria, Patrizia; Amicosante, Gianfranco

    2013-02-01

    The frequency of Klebsiella pneumoniae carbapenemase-producing K. pneumoniae is increasing in Italian hospitals and poses an emerging threat to the management of infections in hospitalized patients. In this study, we report a detailed molecular characterization of a K. pneumoniae subsp. pneumoniae KP1/11 isolate from the decubitus ulcer of a hospitalized patient with a serious infection. K. pneumoniae KP1/11 produces KPC-3 and VIM-2 ?-lactamases. The bla(KPC-3) gene is harbored in a large plasmid in a complex structure of Tn3-based transposon, Tn4401a. The chromosomal DNA of K. pneumoniae harbored also 2 class 1 integrons with different variable regions: 1) orfD-aacA8; 2) aacA29-bla(VIM-2). PMID:23153971

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  9. Loss of benefit in VIM thalamic deep brain stimulation (DBS) for essential tremor (ET): how prevalent is it?

    PubMed

    Shih, Ludy C; LaFaver, Kathrin; Lim, Chen; Papavassiliou, Efstathios; Tarsy, Daniel

    2013-07-01

    Ventralis intermedius (Vim) thalamic deep brain stimulation for medication-refractory essential tremor (ET) has been shown to significantly improve severity of limb tremor in several large case series with significant reduction in objective motor scores. A variable proportion of patients experience decline in benefit over time, however, most studies have not been designed to describe the phenomenon of waning benefit in terms that are helpful for patient counseling. In this retrospective single center study, we define waning benefit as a phenomenon that occurs after patients begin to require reprogramming visits to optimize DBS benefit on tremor. We employed a survival analysis with time to escape (TTE) as a quantitative measure of time elapsed between implantation and the need for subsequent reprogramming. In our cohort of ET patients operated on with Vim DBS from 1994 to 2009, among 45 subjects who met inclusion criteria, 73% reported waning benefit at some point during a mean follow-up period of 56 months (range 12-152 months). The mean TTE from implantation date was 18 months (range 3-75 months). We conclude that loss of benefit over time from Vim DBS for ET is more prevalent than previously published estimates have indicated and should be discussed during patient counseling regarding durability of expected benefit. In addition, this data suggests that a disease-based explanation rather than technical factors are more likely to explain the decline in benefit. PMID:23582712

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

    USGS Publications Warehouse

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  12. Cloud structure and composition of Jupiter's troposphere from 5-{\\mu}m Cassini VIMS spectroscopy

    E-print Network

    Giles, Rohini S; Irwin, Patrick G J

    2015-01-01

    Jupiter's tropospheric composition and cloud structure are studied using Cassini VIMS 4.5-5.1 {\\mu}m thermal emission spectra from the 2000-2001 flyby. We make use of both nadir and limb darkening observations on the planet's nightside, and compare these with dayside observations. Although there is significant spatial variability in the 5-{\\mu}m brightness temperatures, the shape of the spectra remain very similar across the planet, suggesting the presence of a spectrally-flat, spatially inhomogeneous cloud deck. We find that a simple cloud model consisting of a single, compact cloud is able to reproduce both nightside and dayside spectra, subject to the following constraints: (i) the cloud base is located at pressures of 1.2 bar or lower; (ii) the cloud particles are highly scattering; (iii) the cloud is sufficiently spectrally flat. Using this cloud model, we search for global variability in the cloud opacity and the phosphine deep volume mixing ratio. We find that the vast majority of the 5-{\\mu}m inhomoge...

  13. Analysis of Titan Ontario Lacus' region from Cassini/VIMS observations

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    Liquid hydrocarbons on Titan's surface were long predicted before the radar instrument onboard Cassini detected lakes poleward of 70°N on July 2006. Before that the Cassini Imaging Science Subsystem (ISS) observed a lake-like feature in the south pole, named Ontario Lacus, on June 2005. Here we analyze observations of Ontario Lacus taken by the Visual and Infrared Mapping Spectrometer (VIMS) on 2007 December 4, during the T38 flyby. These are the best spatially resolved images of a Titan lake to date, and were previously reported in Brown et al. (2008). We analyze images taken in the 5 micron, 2.75 micron and 2 micron methane windows. The observing geometry and our data processing (the methodology and its limitations) will be explained, followed by a discussion of the main characteristics of these images. These reproduce a portion of Ontario Lacus, supposedly filled with liquid hydrocarbons. Only part of it is visible on Titan's sunlit side. These images also show what appears to be a "beach", brighter then the lake's core but also brighter then the surrounding area of the lake. The morphology and composition of this beach is investigated and possible scenarios for its formation are explored. This yield constrains to geomorphologic models of Titan's surface. Reference: Brown, R. et al. 2008. The identification of liquid ethane in Titan's Ontario Lacus, Nature 454, 607-610.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  15. Aerosol Optical Depth Assimilation for a Size-Resolved Sectional Model: Impacts of Observationally Constrained, Multi-Wavelength and Fine Mode Retrievals on Regional Scale Analyses and Forecasts

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    An aerosol optical depth (AOD) three-dimensional variational data assimilation technique is developed for the Gridpoint Statistical Interpolation (GSI) system when WRF-Chem forecasts are performed with a detailed sectional model (MOSAIC). Within GSI, forward AOD and adjoint sensitivities are performed using Mie computations from the WRF-Chem optical properties module providing consistency with the forecast. GSI tools such as recursive filters and weak constraints are used to provide correlation within aerosol size bins and upper and lower bounds for the optimization. The system is used to perform assimilation experiments with fine vertical structure and no data thinning or re-gridding on a 12-km horizontal grid over the region of California, USA. A first set of simulations is performed comparing the assimilation impacts of operational MODIS dark target retrievals to observationally constrained ones (i.e. calibrated with AERONET data), the latter ones showing higher error reductions and increased fraction of improved PM2.5 and AOD ground-based monitors. A second set of experiments reveals that the use of fine mode fraction AOD and ocean multi-wavelength retrievals can improve the representation of the aerosol size distribution, while assimilating only 550nm AOD retrievals produces no or at times degraded impact. A demonstration of these tools will also be presented for operational forecast for flight planning of the SEAC4RS campaign. Left panels: May 2010 average maps of operational MODIS Terra (top-left), NASA-NNR (top-middle) product for the same MODIS Terra data, non-assimilated model (bottom-left) and assimilated using NASA NNR (bottom-middle). Monthly averages of the raw and observationally constrained retrievals can be quite different, and assimilation brings model estimates closer to the observation. Right panels: 550-870nm Angstrom exponent fractional error reductions from non-assimilated to assimilated model computed with respect to Aqua retrievals. Figure on top assimilates only MODIS 550nm AOD while the one on the bottom assimilates MODIS 550, 660, 870, and 1240nm over ocean and only 550nm over land. Higher error reductions on angstrom exponent when using multi-wavelength data point towards improvements in aerosol size distributions.

  16. 900 1000 1100 1200 Wavelength ()

    E-print Network

    ) EffectiveArea(cm2 ) (d) (c) (b) (a) LiF2 LiF1 SiC2 SiC1 Figure 4 Estimated effective area of the four between channels. Note that the scales are different for the SiC and LiF channels. 5.4. Wavelength in coating reflectivity, grating efficiency, and detector sensitivity, there is a substantial variation

  17. 900 1000 1100 1200 Wavelength ()

    E-print Network

    ) Effective Area (cm 2 ) (d) (c) (b) (a) LiF2 LiF1 SiC2 SiC1 Figure 4 Estimated effective area of the four between channels. Note that the scales are different for the SiC and LiF channels. 5.4. Wavelength in coating reflectivity, grating efficiency, and detector sensitivity, there is a substantial variation

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

    PubMed Central

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.; Shimizu, Toshifumi

    2013-10-01

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

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

    SciTech Connect

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

    2013-10-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

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

  2. The Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Taylor, Gregory B.

    2007-08-01

    The Long Wavelength Array (LWA) will be a new, open, user-oriented astronomical instrument operating in the relatively unexplored window from 20 80 MHz near arcsecond angular resolution and milliJansky sensitivity. Operated by the University of New Mexico on behalf of the Southwest Consortium (SWC) the LWA will provide a unique training ground for the next generation of radio astronomers. Students may also put skills learned on the LWA to work in computer science, electrical engineering, and the communications industry, among others. The development of the LWA will follow a phased build which benefits from lessons learned at each phase. Four university-based Scientific Testing and Evaluation (ST&E) teams with different areas of concentration: (i) high-resolution imaging and particle acceleration; (ii) wide-field imaging and large scale structures; (iii) ionospheric physics; and (iv) radio frequency interference (RFI) suppression and transient detection will provide the feedback needed to assure that science objectives are met as the build develops. Currently in its first year of construction funding, the LWA team is working on the design for the first station (see also Ray et al. 2006).

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

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

    PubMed

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

    2014-10-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2004-11-01

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

  8. The Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Taylor, G. B.

    2006-08-01

    The Long Wavelength Array (LWA) will be a new, open, user-oriented astronomical instrument operating in the poorly explored window from 20-80 MHz at arcsecond level resolution and mJy level sensitivity. Key science drivers include (1) acceleration, propagation, and turbulence in the ISM, including the space-distribution and spectrum of Galactic cosmic rays, supernova remnants, and pulsars; (2) the high redshift universe, including the most distant radio galaxies and clusters - tools for understanding the earliest black holes and the cosmological evolution of Dark Matter and Dark Energy; (3) planetary, solar, and space science, including space weather prediction and extra-solar planet searches; and (4) the radio transient universe: including the known (e.g., SNe, GRBs) and the unknown. Because the LWA will explore one of the last and least investigated regions of the spectrum, the potential for new discoveries, including new classes of physical phenomena, is high, and there is a strong synergy with exciting new X-ray and Gamma-ray measurements, e.g. for cosmic ray acceleration, transients, and galaxy clusters. Operated by the University of New Mexico on behalf of the South West Consortium (SWC) the LWA will also provide a unique training ground for the next generation of radio astronomers. Students may also put skills learned on the LWA to work in computer science, electrical engineering, and the communications industry, among others. The development of the LWA will follow a phased build, which benefits from lessons learned at each phase. Four university-based Scientific Testing and Evaluation (ST&E) teams with different areas of concentration (1. High resolution imaging and particle acceleration; 2. Wide field imaging and large scale structures; 3. Ionosphere, and 4. RFI suppression and transient detection) will provide the feedback needed to assure that science objectives are met as the build develops. Currently in its first year of construction funding, the LWA team is now bringing up the first station near the Very Large Array site in the southwest US. See also the LWA web pages at: http://lwa.unm.edu and http:// lwa.nrl.navy.mil.

  9. Spontaneous emission within wavelength-scale microstructures

    E-print Network

    Exeter, University of

    major applications in devices such as light emitting diodes (LEDs). This thesis focuses on methods, we focus our attention on parameters appropriate for organic microcavity LED structures. We Wasey to the University of Exeter as a thesis for the degree of Doctor of Philosophy in Physics June

  10. Wavelength and Energy

    NSDL National Science Digital Library

    2012-08-03

    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.

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

    Microsoft Academic Search

    Frank Sczerzenie; Graeme Paul; Clarence Belden

    2011-01-01

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

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

    PubMed

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

    2014-11-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-10-01

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

  15. Short wavelength laser

    DOEpatents

    Hagelstein, P.L.

    1984-06-25

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

  16. Rapid detection of blaNDM, blaKPC, blaIMP, and blaVIM carbapenemase genes in bacteria by loop-mediated isothermal amplification.

    PubMed

    Cheng, Cancan; Zheng, Fen; Rui, Yongyu

    2014-12-01

    A loop-mediated isothermal amplification (LAMP) assay was developed and evaluated for rapid detection of blaKPC, blaNDM, blaIMP, and blaVIM carbapenemase genes. Six oligonucleotides, including outer, inner, and loop primers, were designed for eight distinct regions in each target gene. Two qualitative criteria were used to evaluate LAMP reactions: visual inspection of color change and real-time detection of fluorescence change. The lower detection limit was 10 colony forming units (CFU) per reaction for real-time detection and 100 CFU per reaction for visual inspection for each gene. Two hundred twenty-two carbapenem-resistant clinical isolates (including 100 Pseudomonas aeruginosa, 100 Acinetobacter sp., and 22 Enterobacteriaceae) were tested by LAMP assay. At the same time, these isolates were confirmed by conventional polymerase chain reaction (PCR) and sequencing analysis. In these clinical isolates, the results of 11 strains with blaNDM, 11 strains with blaKPC, 11 strains with blaVIM, and 2 strains with blaIMP obtained using LAMP assays were concordant with conventional PCR. The LAMP method reported here may be a useful and powerful tool for rapid detection of blaNDM, blaKPC, blaIMP, and blaVIM carbapenemase genes in bacteria. PMID:25000338

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

    USGS Publications Warehouse

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

    2012-01-01

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

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

    PubMed

    Hänzelmann, Petra; Schindelin, Hermann

    2011-11-01

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

  19. Optical wavelength image slicer

    Microsoft Academic Search

    Matthew C. Doolan; Michael A. Dopita; Liam E. Waldron; John Hart; Ross Zhelem; Gabe Bloxham; Peter Conroy; Peter McGregor; Leigh Pfitzner

    2004-01-01

    The Wide Field Spectrograph (WiFeS) is a high-throughput double-beam image-slicing spectrograph that will operate over the visible wavelength range 320nm to 1000nm. Designed by the Australian National University's Research School of Astronomy and Astrophysics (RSAA) at Mount Stromlo, WiFeS is based on an Integral Field Unit (IFU) and Volume Phased Holographic (VPH) grating technology. Central to the IFU design is

  20. The Long Wavelength Array

    Microsoft Academic Search

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

    2004-01-01

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

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

    USGS Publications Warehouse

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

    2009-01-01

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

  2. Scales

    SciTech Connect

    Murray Gibson

    2007-04-27

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

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

    USGS Publications Warehouse

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

    2007-01-01

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

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

    USGS Publications Warehouse

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

    2006-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Sczerzenie, Frank; Paul, Graeme; Belden, Clarence

    2011-07-01

    Inclusion content is important for the mechanical behavior and performance of Nitinol wires, particularly in fatigue-rated devices. The purpose of this work was to make a quantitative comparison between inclusion populations in cold drawn wires and the precursor populations in hot-rolled rod coil. Inclusion content was examined in a series of VIM-VAR alloys with different transformation temperatures (TTR) controlled by the Ni to Ti ratio. This range of chemistry was chosen to assess the effect of Ni to Ti ratio on inclusion formation. In order to understand the differences in behavior between carbides and intermetallic oxides in wire drawing, carbides, and intermetallic oxide inclusions were measured separately using optical metallography pursuant to ASTM F2063. In VIM-VAR alloys at higher Ni to Ti ratios about 50.79 a/o Ni the formation of intermetallic oxides appears to be suppressed in the as-cast material through the presence of carbon and the precipitation of eutectic TiC in place of eutectic Ti4Ni2O x . The structure of VIM-VAR alloy also varies after hot working depending on the TTR of the alloy. Higher TTR binary alloys with lower Ni to Ti ratios tend to have more and larger intermetallic oxides and fewer and smaller carbides after hot working. Microsegregation plays a role in inclusion formation. That is, during solidification, C, O, N diffuse to the interdendritic regions. This increases the potential for the precipitation of nonmetallic species. Carbides and intermetallic oxides behave differently in hot working and cold drawing. The change in maximum carbide size from coil to wire is very near zero for all Ni to Ti ratios. The change in maximum inclusion size from coil to wire is driven mainly by the fracture of intermetallic oxides and the formation of intermetallic oxide stringers.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  9. Providencia isolates carrying bla (PER-1) and bla (VIM-2) genes: biofilm-forming capacity and biofilm inhibitory concentrations for carbapenem antibiotics.

    PubMed

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

    2011-06-01

    Multidrug-resistant clinical isolates of Providentia carrying bla (PER-1) and bla (VIM-2) were evaluated for the abilities to form biofilm and high biofilm forming capacity was demonstrated in them. Minimum biofilm inhibitory concentrations (MBICs), minimum biofilm eradication concentrations (MBECs), and minimum inhibitory concentrations (MICs) for imipenem and meropenem were also determined. In all tested strains, the MBICs were higher than the MICs for both drugs. Interestingly, the MBICs and the MBEC(50) for meropenem were lower than those for imipenem in the isolates producing high amounts of biofilm, suggesting that meropenem is superior to imipenem in the growth inhibition and eradication of biofilm forming Providentia strains. PMID:21717342

  10. Wavelength references for 1300-nm wavelength-division multiplexing

    Microsoft Academic Search

    T. Dennis; E. A. Curtis; C. W. Oates; L. Hollberg; S. L. Gilbert

    2002-01-01

    We have conducted a study of potential wavelength calibration references for use as both moderate-accuracy transfer standards and high-accuracy National Institute of Standards and Technology (NIST) internal references in the 1280-1320-nm wavelength-division-multiplexing region. We found that most atomic and molecular absorption lines in this region are not ideal for use as wavelength references owing to factors such as weak absorption,

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

    PubMed

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

    2010-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    The most detailed pre-Cassini investigation of the geometry of Saturn's rings was published two decades ago as part of an effort to determine Saturn's pole direction and the radius scale for the ring system [1] (henceforth F93). This study was based on the Voyager 1 egress RSS ring occultation from 1980, the 1981 Voyager 2 egress PPS stellar occultation of ? Sco, and high-SNR earth-based 28 Sgr occultation measurements that were limited in radial resolution by the 20 km projected diameter of the occulted star; Bosh [2] expanded on these "historical" results by incorporating occultation results from the Hubble Space Telescope (HST). The wealth of Cassini occultation observations has provided detailed views of the structure of Saturn's rings at much higher spatial resolution and better SNR than ever before [3], especially in the optically thick B ring, and our Cassini-based orbit fits to the rings have provided important corrections to the F93 radius scale of the rings. The F93 results were based on orbit fits to 38 putatively circular features from an atlas of 66 numbered features visible in the Voyager and 28 Sgr data, with a grand total of 452 data points from three occultations fitted to obtain Saturn's pole direction and the ring radius scale. Compared to these solutions, we have increased the number of occultations from three to over 150 and the catalog of consistently identifiable, persistent sharp-edged features from 66 to over 300, mostly in the C and B rings, and the Cassini Division (the A ring is etched by almost innumerable density waves produced by Saturn's plethora of satellites). Figure 1 shows a portion of our updated atlas of features. We have determined the orbital elements of all of these features, with an estimated accuracy of ~250 m in orbital radius. Much of the newly-explored structure in the B ring is poorly understood, and may represent viscous overstabilities in the denser parts of the rings [3]; these accurate orbit solutions, coupled with the decade timescale of the Cassini observations, will enable us to set limits on possible changes in the locations of these abrupt features. The comprehensive catalog, accurately registered in absolute radius, will also provide a guide to other investigators who wish to determine the absolute radius of nearby features in imaging and occultation observations.

  13. Laser wavelength comparison by high resolution interferometry.

    PubMed

    Layer, H P; Deslattes, R D; Schweitzer, W G

    1976-03-01

    High resolution interferometry has been used to determine the wavelength ratio between two molecularly stabilized He-Ne lasers, one locked to a methane absorption at 3.39 microm and the other locked to the k peak of (129)I(2) at 633 nm. An optical beat frequency technique gave fractional orders while a microwave sideband method yielded the integer parts. Conventional (third derivative) peak seeking servoes stabilized both laser and cavity lengths. Reproducibility of the electronic control system and optics was a few parts in 10(12), while systematic errors associated with curvature of the cavity mirrors limited the accuracy of the wavelength ratio measurement to 2 parts in 10(10). The measured wavelength ratio of the methane stabilized He-Ne laser at 3.39 microm [P(7) line, nu(3) band] to the (129)I(2) (k peak) stabilized He-Ne laser at 633 nm was 5.359 049 260 6 (0.000 2 ppm). This ratio agrees with that calculated from the (lower accuracy) results of earlier wavelength measurements made relative to the (86)Kr standard. Its higher accuracy thus permits a provisional extension of the frequency scale based on the cesium oscillator into the visible spectrum. PMID:20165049

  14. Compact integrated silica wavelength filters

    Microsoft Academic Search

    Christopher N. Morgan; Siyuan Yu; Richard V. Penty; Ian H. White

    2002-01-01

    The realization of compact low-loss wavelength filters using two-dimensional integrated optics (2DIO) in a silica-on-silica material system is reported. Two designs suitable for data-communications applications are reported: a 4 × 4 channel 6.4-nm channel wavelength spacing device and an 8 × 8 channel 3.2-nm channel wavelength spacing device. The devices are fabricated in one deep etch step, and after cleaving

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

    PubMed

    Hawkes, Jeremy J; Radel, Stefan

    2013-02-21

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

  16. Radio telescopes for millimeter wavelength

    Microsoft Academic Search

    S. von Hoerner

    1975-01-01

    General rules are discussed for selecting the shortest observational wavelength and for finding the largest technically possible diameter for the design of steerable radio telescopes. The shortest wavelength should be in one of the four atmospheric windows of good transparency, and the largest diameter then is defined by thermal deformations if gravitational deformations are omitted by a homologously deforming design.

  17. AWG Filter for Wavelength Interrogator

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  18. Wavelength selector for tunable laser

    SciTech Connect

    Shoshan, I.

    1980-10-21

    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.

  19. Long wavelength quantum cascade lasers

    Microsoft Academic Search

    A. Tredicucci; F. Capasso; C. Gmachl; D. L. Sivco; A. L. Hutchinson; A. Y. Cho

    1999-01-01

    Quantum cascade (QC) lasers operating on intersubband transitions between conduction band states in InGaAs\\/AlInAs heterostructures have proven so far to be extremely versatile, covering the range of wavelengths of the two atmospheric windows (3.4 ?m, 13 ?m). Their extension to even longer wavelengths is, however, problematic, due to the increasingly smaller radiative efficiency of intersubband transitions and to the optical

  20. Modulating short wavelength fluorescence with long wavelength light.

    PubMed

    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

    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

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

    PubMed Central

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

    2015-01-01

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

  2. Prevalence of bla NDM, bla PER, bla VEB, bla IMP, and bla VIM Genes among Acinetobacter baumannii Isolated from Two Hospitals of Tehran, Iran.

    PubMed

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

    2014-01-01

    Background and Objectives. The aim of this study was to determine the frequency of bla NDM, bla PER, bla VEB, bla IMP, and bla VIM 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 bla PER-1, bla VEB-1, bla IMP-1, and bla VIM-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

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

    PubMed

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

    2015-01-01

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

  4. Extensively drug-resistant pseudomonas aeruginosa isolates containing blaVIM-2 and elements of Salmonella genomic island 2: a new genetic resistance determinant in Northeast Ohio.

    PubMed

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

    2014-10-01

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

  5. A wavelength-convertible optical network

    Microsoft Academic Search

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

    1993-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    PubMed

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

    2014-12-01

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

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

    PubMed Central

    Jirauschek, Christian; Huber, Robert

    2015-01-01

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

  9. Solid colloidal optical wavelength filter

    DOEpatents

    Alvarez, Joseph L. (Boulder, CO)

    1992-01-01

    A solid colloidal optical wavelength filter includes a suspension of spheal particles dispersed in a coagulable medium such as a setting plastic. The filter is formed by suspending spherical particles in a coagulable medium; agitating the particles and coagulable medium to produce an emulsion of particles suspended in the coagulable medium; and allowing the coagulable medium and suspended emulsion of particles to cool.

  10. Spuriousless single wavelength quartz resonators

    Microsoft Academic Search

    Y. Nagaura; K. Nagaura; Z. Nagaura

    2004-01-01

    The primary research objective is to manufacture quartz resonators that can oscillate elastic waves with a single wavelength and a precise directional performance. This objective has been the dream of many researchers since the discovery of the piezoelectric effect of quartz in 1880 by the brothers Pierre and Jacques Curie who brought into being the development of the ultrasonic and

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  12. Wavelength stabilized multi-kW diode laser systems

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    Microsoft Academic Search

    P. Michel; L. Divol; R. P. J. Town; M. D. Rosen; D. A. Callahan; N. B. Meezan; M. B. Schneider; J. D. Moody; E. L. Dewald; K. Widmann; E. Bond; C. A. Thomas; S. Dixit; E. A. Williams; D. E. Hinkel; R. L. Berger; O. L. Landen; M. J. Edwards; B. J. MacGowan; J. D. Lindl

    2011-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Momary, Thomas W.; Baines, Kevin H.

    2014-11-01

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

  15. Multi-wavelength holographic profilometry

    NASA Astrophysics Data System (ADS)

    Barbosa, E. A.; Gesualdi, M. R.; Muramatsu, M.

    2006-01-01

    A novel method for surface profilometry by holography is presented. We used a diode laser emitting at many wavelengths simultaneously as the light source and a Bi 12TiO 20 (BTO) crystal as the holographic medium in single exposure processes. The employ of multi-wavelength, large free spectral range (FSR) lasers leads to holographic images covered of interference fringes corresponding to the contour lines of the studied surface. In order to obtain the relief of the studied surface, the fringe analysis was performed by the phase stepping technique (PST) and the phase unwrapping was carried out by the Cellular-automata method. We analysed the relief of a tilted flat metallic bar and a tooth prosthesis.

  16. Wavelength Selection in Gyrotactic Bioconvection.

    PubMed

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

    2015-06-01

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

  17. Millimeter-wavelengths propagation studies

    NASA Technical Reports Server (NTRS)

    Hodge, D. B.; Zintsmaster, L. R.

    1972-01-01

    The various meteorological parameters that influence millimeter wavelength satellite-to-ground space diversity links are summarized. Space diversity propagation statistics obtained using the 15.3 GHz down-link on ATS-5 are presented. The radiometric temperature as well as attenuation of the satellite signal was recorded for correlation purposes. Both statistics of individual storm events and cumulative statistics have been analyzed yielding single site and joint fade distributions, correlation between attenuation experienced at the two receiving terminals, and correlation between path radiometric temperatures observed at the two receiving terminals. These data indicate that the use of space diversity is indeed effective in improving the reliability of millimeter wavelength satellite-to-ground communication links.

  18. High power millimetric wavelength sources

    Microsoft Academic Search

    Itzhak Shraga

    1989-01-01

    The aim was to develop powerful, millimetric-wavelength microwave sources, based on a free electron laser in which a dense relativistic electron beam interacts with a longitudinal magnetostatic wiggler. The theoretical background is presented for magnetically guided electron orbits, cyclotron resonance instability, and the Lowbitron-longitudinal wiggler. The electron beam was produced by a PI105 accelerator, which can accelerate 10-kA beams to

  19. Photon's Wavelength Stretching and Shrinking?

    NASA Astrophysics Data System (ADS)

    Smarandache, Florentin

    2013-09-01

    The photon is considered of having a dual form: wave and particle. (a) If the photon is a wave, it has been asserted that the photon's wavelength is stretched inside the intergalactic space, because of the expansion of the universe. But what happens with the photon's wavelength when the photon enters a galactic space (which is not expanding), and afterwards it exists the galactic space and enters an intergalactic space (which is expanding), and so on? But, when the wavelength increases the wave frequency decreases (redshift); therefore the wave's momentum and energy are diminished in the expansion of the universe. It seems to be an antithesis between the quantum mechanics (Copenhagen style) and the universe expansion. (b) If the photon is a particle, similarly because of the so-called expansion of the universe, does its pathlength increases inside the intergalactic space (which is expanding) and decreases inside the galactic space (which is not expanding)? Thus, what happens with its pathlength when the photon passes from an intergalactic space to a galactic space, then again to intergalactic space, and so on?

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

    SciTech Connect

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

    1982-01-01

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

  1. Wavelength Effects In Femtosecond Pulsed Laser Ablation And Deposition

    SciTech Connect

    Castillejo, Marta; Nalda, Rebeca de; Oujja, Mohamed; Sanz, Mikel [Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid (Spain)

    2010-10-08

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

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

    E-print Network

    Zhou, Ying

    2010-07-14

    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 ...

  3. Repeated wavelength conversion of 10 Gbit\\/s signal using wavelength-tunable semiconductor lasers

    Microsoft Academic Search

    Hiroshi Yasaka; Hiroyuki Ishii; Yuzo Yoshikuni; Kunishige Oe

    1995-01-01

    Repeated wavelength conversion of 10 Gbit\\/s pseudorandom non-return-to-zero signals is demonstrated using superstructure grating distributed Bragg reflector lasers operating in the 1.55-?m wavelength region. Error-free and very low-power-penalty wavelength conversion can be achieved in both first and second wavelength conversion for a fixed converted wavelength over a broad wavelength range from 1.486 to 1.573 ?m (about 90-nm wide). The power

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

    NASA Astrophysics Data System (ADS)

    Kita, Tomohiro; Tang, Rui; Yamada, Hirohito

    2015-03-01

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

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

    E-print Network

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

    2014-01-01

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

  6. Use of Imipenem To Detect KPC, NDM, OXA, IMP, and VIM Carbapenemase Activity from Gram-Negative Rods in 75 Minutes Using Liquid Chromatography-Tandem Mass Spectrometry

    PubMed Central

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

    2014-01-01

    Resistance to extended-spectrum ?-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

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  9. Making Displaced Holograms At Two Wavelengths

    NASA Technical Reports Server (NTRS)

    Witherow, William K.; Ecker, Andreas

    1989-01-01

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

  10. Simultaneous wavelength conversion of ASK and DPSK signals based on four-wave-mixing in dispersion engineered silicon waveguides.

    PubMed

    Xu, Lin; Ophir, Noam; Menard, Michael; Lau, Ryan Kin Wah; Turner-Foster, Amy C; Foster, Mark A; Lipson, Michal; Gaeta, Alexander L; Bergman, Keren

    2011-06-20

    We experimentally demonstrate four-wave-mixing (FWM)-based continuous wavelength conversion of optical differential-phase-shift-keyed (DPSK) signals with large wavelength conversion ranges as well as simultaneous wavelength conversion of dual-wavelength channels with mixed modulation formats in 1.1-cm-long dispersion-engineered silicon waveguides. We first validate up to 100-nm wavelength conversion range for 10-Gb/s DPSK signals, showcasing the capability to perform phase-preserving operations at high bit rates in chip-scale devices over wide conversion ranges. We further validate the wavelength conversion of dual-wavelength channels modulated with 10-Gb/s packetized phase-shift-keyed (PSK) and amplitude-shift-keyed (ASK) signals; demonstrate simultaneous operation on multiple channels with mixed formats in chip-scale devices. For both configurations, we measure the spectral and temporal responses and evaluate the performances using bit-error-rate (BER) measurements. PMID:21716454

  11. Multiple wavelength light collimator and monitor

    NASA Technical Reports Server (NTRS)

    Gore, Warren J. (Inventor)

    2011-01-01

    An optical system for receiving and collimating light and for transporting and processing light received in each of N wavelength ranges, including near-ultraviolet, visible, near-infrared and mid-infrared wavelengths, to determine a fraction of light received, and associated dark current, in each wavelength range in each of a sequence of time intervals.

  12. A Review of Routing and Wavelength Assignment Approaches for WavelengthRouted Optical WDM Networks

    E-print Network

    Jue, Jason P.

    simulation. 1 Introduction Wavelength­division multiplexing (WDM) in optical fiber networks has been rapidlyA Review of Routing and Wavelength Assignment Approaches for Wavelength­Routed Optical WDM Networks@cs.ucdavis.edu August 13, 1999 Abstract This study focuses on the routing and wavelength assignment (RWA) problem

  13. High-performance wavelength-locked diode lasers

    Microsoft Academic Search

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

    2009-01-01

    Rapidly maturing industrial laser applications are placing ever-tighter constraints on spectral width and wavelength emission stability over varying operating temperatures of high power diode laser pump sources. For example, improved power scaling and efficiency can be achieved by pumping the narrow upper laser level of Nd:YAG solid state lasers at 885 nm and the 1532-nm absorption band of Er:YAG solid

  14. Long wavelength video detection of fire in ship compartments

    Microsoft Academic Search

    Jeffrey C. Owrutsky; Daniel A. Steinhurst; Christian P. Minor; Susan L. Rose-Pehrsson; Frederick W. Williams; Daniel T. Gottuk

    2006-01-01

    This paper describes progress using filtered, long wavelength video image-based detection (LWVD) of events in laboratory tests and full scale fire testing within the Volume Sensor Program at the U.S. Naval Research Laboratory (NRL). This effort toward developing a real-time, remote sensing detection system utilizes video image detection (VID) systems based on cameras that operate in the visible region, which

  15. Solar flares at submillimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Trottet, Gérard; Kaufmann, Pierre; Lüthi, Thomas; Guillermo Guiménez de Castro, C.; Raulin, Jean-Pierre; Marun, Adolfo; Klein, Karl-Ludwig

    2010-05-01

    The presence of a new solar burst spectral component with flux density increasing with frequency above 200 GHz, spectrally different from the well-known microwave component, has been recently revealed by observations made at 212 and 405 GHz by the Solar Submillimeter Telescope and at 210, 230 and 345 GHz with the telescope of the Köln Observatory for Submillimeter and Millimeter Astronomy. Such unprecedented observations bring new possibilities to explore particle acceleration and energy transport processes during a flare, both observationally and theoretically. In this presentation we give a brief overview of submillimeter and joint microwave and X-ray-gamma-ray observations obtained so far. Possible mechanisms to explain the double spectral components at microwaves and in the submillimeter domain are discussed. We finally emphasize the need of observations at shorter wavelengths, in particular in the far infrared domain, to fully benefit from these new diagnostics of the flaring processes.

  16. Transparency of the atmosphere to short horizontal wavelength gravity waves

    NASA Astrophysics Data System (ADS)

    Preusse, Peter; Eckermann, Stephen D.; Ern, Manfred

    2008-12-01

    We use theory and global ray modeling to investigate how the potential of gravity waves to transport momentum flux globally from the lower atmosphere into the mesosphere and lower thermosphere (MLT) varies with horizontal wavelength and ground-based phase speed. Ray modeling is performed using the Gravity Wave Regional or Global Ray Tracer (GROGRAT) interfaced to realistic three-dimensional global winds and temperatures from 0 to 100 km altitude, specified by fusing analysis fields at lower altitudes to GCM results higher up. We focus on gravity waves in the short 10- to 50-km horizontal wavelength range that are unresolved by global models and, according to theory, can transport appreciable momentum flux into the MLT. Ray results for different seasons reproduce some of the limits derived from simple wave theory: that horizontal wavelengths shorter than 10 km tend to be removed by vertical reflection or evanescence at the source and slower phase speeds are more prone to critical level removal, leading to a preference for waves with longer horizontal wavelengths and faster ground-based phase speeds to reach the MLT. These findings are compared to the wavelength scales currently resolved by satellite limb and nadir sounders, highlighting wavelength ranges currently measured and those currently unresolved. A road map is developed for how current and future satellite measurements can be combined to measure the full space-time spectrum of gravity waves relevant to eddy flux deposition and momentum forcing of the global MLT. In particular, recommendations for new satellite measurement strategies that fill current measurement gaps are provided.

  17. Optical wavelength converters for photonic band gap microcircuits

    SciTech Connect

    Vujic, Dragan; John, Sajeev [Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario, M5S-1A7 (Canada)

    2009-05-15

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

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

    PubMed

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

    2015-03-01

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

  19. Inter-network regions of the Sun at millimetre wavelengths

    NASA Astrophysics Data System (ADS)

    Wedemeyer-Böhm, S.; Ludwig, H. G.; Steffen, M.; Leenaarts, J.; Freytag, B.

    2007-09-01

    Aims:The continuum intensity at wavelengths around 1 mm provides an excellent way to probe the solar chromosphere and thus valuable input for the ongoing controversy on the thermal structure and the dynamics of this layer. The synthetic continuum intensity maps for near-millimetre wavelengths presented here demonstrate the potential of future observations of the small-scale structure and dynamics of internetwork regions on the Sun. Methods: The synthetic intensity/brightness temperature maps are calculated on basis of three-dimensional radiation (magneto-)hydrodynamic (MHD) simulations. The assumption of local thermodynamic equilibrium (LTE) is valid for the source function. The electron densities are also treated in LTE for most maps but also in non-LTE for a representative model snapshot. Quantities like intensity contrast, intensity contribution functions, spatial and temporal scales are analysed in dependence on wavelength and heliocentric angle. Results: While the millimetre continuum at 0.3 mm originates mainly from the upper photosphere, the longer wavelengths considered here map the low and middle chromosphere. The effective formation height increases generally with wavelength and also from disk-centre towards the solar limb. The average intensity contribution functions are usually rather broad and in some cases they are even double-peaked as there are contributions from hot shock waves and cool post-shock regions in the model chromosphere. The resulting shock-induced thermal structure translates to filamentary brightenings and fainter regions in between. Taking into account the deviations from ionisation equilibrium for hydrogen gives a less strong variation of the electron density and with it of the optical depth. The result is a narrower formation height range although the intensity maps still are characterised by a highly complex pattern. The average brightness temperature increases with wavelength and towards the limb although the wavelength-dependence is reversed for the MHD model and the NLTE brightness temperature maps. The relative contrast depends on wavelength in the same way as the average intensity but decreases towards the limb. The dependence of the brightness temperature distribution on wavelength and disk-position can be explained with the differences in formation height and the variation of temperature fluctuations with height in the model atmospheres. The related spatial and temporal scales of the chromospheric pattern should be accessible by future instruments. Conclusions: Future high-resolution millimetre arrays, such as the Atacama Large Millimeter Array (ALMA), will be capable of directly mapping the thermal structure of the solar chromosphere. Simultaneous observations at different wavelengths could be exploited for a tomography of the chromosphere, mapping its three-dimensional structure, and also for tracking shock waves. The new generation of millimetre arrays will be thus of great value for understanding the dynamics and structure of the solar atmosphere.

  20. Wavelength comparison study for bioaerosol detection

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  1. Wavelength Compensation in Fused Fiber Couplers.

    NASA Astrophysics Data System (ADS)

    Wang, Zhi G.

    The performance of fused fiber couplers is wavelength dependent. Wavelength spectral compensation is a technique to decrease the effect of the wavelength dependence, which is an essential task for many applications in fiber optic communication systems. Fiber devices such as wavelength -flattened couplers (WFCs) can be fabricated using wavelength spectral compensation methods. In this dissertation, wavelength spectral compensation techniques in fused biconical taper (FBT) couplers including both multimode and single-mode fiber couplers are studied in detail. In multimode fiber coupler operation, a novel theoretical model based on frustrated total internal reflection (FTIR) has been developed to effectively describe the power coupling and loss mechanism. Experimental results support the theoretical predictions. In single -mode fiber couplers, the conventional technique of fabricating WFCs is discussed. An alternative analytical model has been developed based upon coupled mode theory, which provides a relatively simple and mathematically sound explanation to the wavelength spectral compensation. Aiming to simplify WFC fabrication, a new way of constructing WFCs is proposed and demonstrated by connecting regular single-mode fiber couplers, some of which serve as wavelength spectral compensators. WFCs of various structures including 2 x 2, 1 x 3, 1 x 2 ^{N}, and 4 x 4 have been developed, and the experimental data agree with theoretical predictions of performance. Potential applications and future research directions in wavelength spectral compensation are also presented.

  2. Astronomical Interferometry at Submillimetre Wavelengths

    E-print Network

    Lay, Oliver Peter

    1994-10-18

    the dust continuum emission on scales of HL Tau and LlSS1-IRS S. An analysis of the visibility curves is presented, showing that the emission is extended perpendicular to the outflow direction in each case; radii to half...

  3. Wavelength Converters in Dynamically-Reconfigurable WDM Networks

    Microsoft Academic Search

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

    1999-01-01

    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

  4. Wavelength-domain RF photonic signal processing

    NASA Astrophysics Data System (ADS)

    Gao, Lu

    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.

  5. Optimum wavelengths for two color ranging

    NASA Technical Reports Server (NTRS)

    Degnan, John J.

    1993-01-01

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

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

    SciTech Connect

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

    2007-01-01

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

  7. 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

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

    2008-09-01

    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

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

    SciTech Connect

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

    2012-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  10. Wavelength detection using optical fiber speckle patterns

    Microsoft Academic Search

    Byungchoon Yang; Il-Min Lee; Byoungho Lee

    2000-01-01

    If the wavelength of injected light changes, the phase of the field also changes. Then the intensity distribution also changes. This property has been introduced to the application of holographic recording to reduce crosstalk and enhance hologram density. We can use this property in the sensing of wavelength change in an optical fiber sensing system. In the experiment, the laser

  11. Wavelength tracking with thermally controlled silicon resonators

    E-print Network

    Mellor-Crummey, John

    of the resonant wavelength of a silicon dual-ring resonator. The feedback signal is the difference in optical-optic tuning with micro-heaters. This control scheme keeps the central wavelength of the resonator aligning, and R. Baets, "Athermal Silicon-on-insulator ring resonators by overlaying a polymer cladding

  12. A wavelength detector for monochromatic light beams

    Microsoft Academic Search

    L. Ngo Phong; I. Shih

    1996-01-01

    Wavelength detection of monochromatic light beams can be achieved with a pair of optical sensors located behind a linear variable filter. The active area of one sensor increases, whereas that of the other sensor decreases along the direction of increasing value of transmission wavelength of the filter. By computing the ratio of the photoresponse of one sensor to the other,

  13. FOCUS: MALDI Exploring Infrared Wavelength Matrix-

    E-print Network

    Chait, Brian T.

    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. The shapes of the spectral peaks obtained with DE-IR-MALDI-MS are compared with those obtained from the same

  14. Efficient routing and wavelength assignment for reconfigurable WDM ring networks with wavelength converters

    Microsoft Academic Search

    Li-Wei Chen; Eytan Modiano

    2005-01-01

    We consider the problem of wavelength assignment in reconfigurable WDM networks with wavelength converters. We show that for N-node P-port bidirectional rings, a minimum number of ?PN\\/4? wavelengths are required to support all possible connected virtual topologies in a rearrangeably nonblocking fashion, and provide an algorithm that meets this bound using no more than ?PN\\/2? wavelength converters. This improves over

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

    Microsoft Academic Search

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

    2000-01-01

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

  16. Wavelength Converter Placement Scheme for Optical Network with Sparse-Partial Wavelength Conversion Capability

    Microsoft Academic Search

    Andre Soares; Paulo Cunha; Jose Maranhao

    In this paper it is proposed a new wavelength converter placement scheme called First Load Priority - FLP, useful for designing and planning of optical networks with sparse- partial wavelength conversion architecture. A performance eval- uation of FLP working in different scenarios is provided. Com- paring to other wavelength converter placement schemes like MBPF, TOT and XC, FLP achieved better

  17. Wavelength dependence of maximal diffraction-limited output power of fiber lasers

    NASA Astrophysics Data System (ADS)

    Otto, Hans-Jürgen; Modsching, Norbert; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

    2015-03-01

    The threshold-like onset of mode instabilities is currently the main limitation for the scaling of the average output power of fiber-laser systems with diffraction limited beam quality. In this contribution wavelength shifting of the seed signal has been experimentally investigated in order to mitigate mode instabilities. Against the expectations, it is experimentally shown that the highest mode instabilities threshold is reached around 1030 nm and not for the smallest wavelength separation between pump and signal wavelength. This finding implies that the quantum defect is not the sole significant source for thermal heating in the fiber.

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

    NASA Technical Reports Server (NTRS)

    Suematsu, Y.; Iga, K.

    1980-01-01

    Crystal growth and the characteristics of semiconductor lasers and diodes for the long wavelength band used in optical communications are examined. It is concluded that to utilize the advantages of this band, it is necessary to have a large scale multiple wavelength communication, along with optical cumulative circuits and optical exchangers.

  19. High power millimetric wavelength sources

    NASA Astrophysics Data System (ADS)

    Shraga, Itzhak

    1989-11-01

    The aim was to develop powerful, millimetric-wavelength microwave sources, based on a free electron laser in which a dense relativistic electron beam interacts with a longitudinal magnetostatic wiggler. The theoretical background is presented for magnetically guided electron orbits, cyclotron resonance instability, and the Lowbitron-longitudinal wiggler. The electron beam was produced by a PI105 accelerator, which can accelerate 10-kA beams to 800 keV energy, in 10-nsec pulses. A cold foilless diode electron source was built, with a graphite cathode and variously shaped, interchangeable anodes, and the beam was guided along a stainless steel drift tube by a pulsed axial magnetic field. Onto a 30-kgauss field was superimposed a ripple, generated by a series of alternating insulating and conducting rings outside the drift tube. Electron beam and magnetic field parameters were measured, using a Faraday cup, witness plates and Rogowski coils, and the total generated microwave power, in the 60-140-GHz range, was measured with a broadband solid state detector or a calorimeter. Computer simulations and microwave measurements were used to establish the optimum electrode geometry for the foilless diode; a spherical graphite cathode and planar anode were chosen and a 1-kA pencil electron beam was extracted through an iris, centered on the longitudinal axis of the drift tube. Cyclotron instability studies showed that application of magnetic resonance criteria, in accordance with the theoretical model, enabled the maximum microwave power to be obtained. The 2nd harmonic of the cyclotron frequency was also found to agree well with the theoretical model. A 400-A, 740-kV, 4-mm diameter beam was used to investigate the Lowbitron-longitudinal wiggler free electron laser. A short, magnetoresonance-based, undulator was used to convert axial to perpendicular energy, and the beam was passed through the magnetostatic wiggler, implemented by magnetic diffusion. The microwave spectra were measured and analyzed for different wiggler periods and a modified dispersion equation for the cylindrical waveguide was solved numerically. Frequency and growth-rate solutions agreed well with the measurements.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  1. Short wavelength FELs using the SLAC linac

    SciTech Connect

    Winick, H.; Bane, K.; Boyce, R. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)] [and others

    1993-08-01

    Recent technological developments have opened the possibility to construct a device which we call a Linac Coherent Light Source (LCLS); a fourth generation light source, with brightness, coherence, and peak power far exceeding other sources. Operating on the principle of the free electron laser (FEL), the LCLS would extend the range of FEL operation to much aborter wavelength than the 240 mn that has so far been reached. We report the results of studies of the use of the SLAC linac to drive an LCLS at wavelengths from about 3-100 nm initially and possibly even shorter wavelengths in the future. Lasing would be achieved in a single pass of a low emittance, high peak current, high energy electron beam through a long undulator. Most present FELs use an optical cavity to build up the intensity of the light to achieve lasing action in a low gain oscillator configuration. By eliminating the optical cavity, which is difficult to make at short wavelengths, laser action can be extended to shorter wavelengths by Self-Amplified-Spontaneous-Emission (SASE), or by harmonic generation from a longer wavelength seed laser. Short wavelength, single pass lasers have been extensively studied at several laboratories and at recent workshops.

  2. Wavelength-spacing tuning of a dual-wavelength active-mode locking fiber laser.

    PubMed

    Lee, Hwi Don; Jeong, Myung Yung; Kim, Chang-Seok

    2014-11-01

    We demonstrate a novel concept of wavelength-spacing tuning of a dual-wavelength active-mode locking fiber laser in the 1.3-?m wavelength region. A dual-cavity configuration is implemented using a chirped fiber Bragg grating pair for wavelength-spacing tuning. Both normal and anomalous dispersion cavities were schematically designed for wavelength-spacing tuning ranging from 3.52-33.54 nm. The side-mode suppression ratio was ?30??dB for both wavelengths. Because of the filter-less tuning mechanism, a fast repletion rate of wavelength-spacing sweeping and switching was demonstrated for frequencies up to 50 kHz. PMID:25361287

  3. Magic wavelengths for terahertz clock transitions

    SciTech Connect

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

    2010-01-15

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

  4. Optical amplification at the 1. 31 wavelength

    DOEpatents

    Cockroft, N.J.

    1994-02-15

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

  5. Polymer photochemistry at the EUV wavelength

    E-print Network

    Fedynyshyn, Theodore H.

    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 ...

  6. The ISO Long-Wavelength Spectrometer

    Microsoft Academic Search

    Paolo Saraceno; P. A. R. Ade; C. Armand; J.-P. Baluteau; M. J. Barlow; M. A. Buckley; J.-C. Berges; M. Burgdorf; E. Caux; C. Ceccarelli; R. Cerulli; S. E. Church; F. Cotin; P. Cox; P. Cruvellier; J. L. Culhane; G. R. Davis; A. di Giorgio; B. R. Diplock; D. L. Drummond; R. J. Emery; J. D. Ewart; J. Fischer; I. Furniss; W. M. Glencross; M. A. Greenhouse; M. J. Griffin; C. Gry; A. S. Harwood; A. S. Hazell; M. Joubert; K. J. King; T. Lim; R. Liseau; J. A. Long; D. Lorenzetti; S. Molinari; A. G. Murray; D. A. Naylor; B. Nisini; K. Norman; A. Omont; R. Orfei; T. J. Patrick; D. Pequignot; D. Pouliquen; M. C. Price; Nguyen-Q-Rieu; A. J. Rogers; F. D. Robinson; M. Saisse; G. Serra; S. D. Sidher; A. F. Smith; H. A. Smith; L. Spinoglio; B. M. Swinyard; D. Texier; W. A. Towlson; N. R. Trams; S. J. Unger; G. J. White

    1996-01-01

    The Long-Wavelength Spectrometer (LWS) is one of two complementary spectrometers aboard the European Space Agency's Infrared Space Observatory (ISO) (Kessler et al., 1996A&A...315L..49D). It operates over the wavelength range 43-196.9mum at either medium (about 150 to 200) or high (6800 to 9700) spectral resolving power. This Letter describes the instrument and its modes of operation; a companion paper (Swinyard et

  7. The ISO Long-Wavelength Spectrometer.

    NASA Astrophysics Data System (ADS)

    Clegg, P. E.; Ade, P. A. R.; Armand, C.; Baluteau, J.-P.; Barlow, M. J.; Buckley, M. A.; Berges, J.-C.; Burgdorf, M.; Caux, E.; Ceccarelli, C.; Cerulli, R.; Church, S. E.; Cotin, F.; Cox, P.; Cruvellier, P.; Culhane, J. L.; Davis, G. R.; di Giorgio, A.; Diplock, B. R.; Drummond, D. L.; Emery, R. J.; Ewart, J. D.; Fischer, J.; Furniss, I.; Glencross, W. M.; Greenhouse, M. A.; Griffin, M. J.; Gry, C.; Harwood, A. S.; Hazell, A. S.; Joubert, M.; King, K. J.; Lim, T.; Liseau, R.; Long, J. A.; Lorenzetti, D.; Molinari, S.; Murray, A. G.; Naylor, D. A.; Nisini, B.; Norman, K.; Omont, A.; Orfei, R.; Patrick, T. J.; Pequignot, D.; Pouliquen, D.; Price, M. C.; Nguyen-Q-Rieu; Rogers, A. J.; Robinson, F. D.; Saisse, M.; Saraceno, P.; Serra, G.; Sidher, S. D.; Smith, A. F.; Smith, H. A.; Spinoglio, L.; Swinyard, B. M.; Texier, D.; Towlson, W. A.; Trams, N. R.; Unger, S. J.; White, G. J.

    1996-11-01

    The Long-Wavelength Spectrometer (LWS) is one of two complementary spectrometers aboard the European Space Agency's Infrared Space Observatory (ISO) (Kessler et al., 1996A&A...315L..49D). It operates over the wavelength range 43-196.9?m at either medium (about 150 to 200) or high (6800 to 9700) spectral resolving power. This Letter describes the instrument and its modes of operation; a companion paper (Swinyard et al, 1996) describes its performance and calibration.

  8. Short wavelength regenerative amplifier free electron lasers

    E-print Network

    Dunning, D J; Thompson, N R

    2008-01-01

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

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

    SciTech Connect

    Newman, D.E.

    1993-09-01

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

  10. Monolithic wavelength-graded VCSEL and wavelength-selective photodetector arrays for WDM applications

    NASA Astrophysics Data System (ADS)

    Cheng, Julian; Luong, Sanh Q.; Ortiz, Gerry G.; Zhou, Yuxin; Lu, Jun; Hou, Hong Q.; Hammons, B. E.; Vawter, G. Allen

    1997-12-01

    Monolithic, multiple-wavelength VCSEL arrays have been obtained by using the surface-controlled enhancement and reduction of the MOCVD epitaxial growth rate to produce a periodic and repeatable grading of the resonance wavelength over a span of greater than 30 nm. Room temperature, electrically-injected, cw lasing has also been achieved with a wavelength span of greater than 20 nm. We show here both the enhancement and the reduction of the growth rate of the entire VCSEL structure and demonstrate the controlled variation of the VCSEL lasing wavelength over a widened spectral range by exploiting both of these effects. Using the same growth techniques, wavelength-selective, resonance-enhanced photodetector arrays with closely-matched resonance wavelengths can be monolithically integrated on the same epilayer structure. We demonstrate the repeatability of this technique using different arrays from the same growth run.

  11. Wavelength Assignment in Multi-Fiber WDM Networks by ...

    E-print Network

    In this paper, we study wavelength assignment problems in multi-fiber WDM net ... Optical Networks, Graph Theory, Combinatorial Optimization, Integer .... A wavelength converter is able to convert a single optical signal from any wavelength to.

  12. Efficient Routing and Wavelength Assignment for Reconfigurable WDM Networks with Wavelength Converters

    Microsoft Academic Search

    Li-wei Chen; Eytan Modiano

    2003-01-01

    We consider the problem of wavelength assignment in a reconfigurable bi-directional ring network with wavelength converters. We show that for N -node P -port bidirectional rings, a minimum number of PN\\/4 wavelengths are required to support all possible virtual topologies in a rearrangeably non-blocking fashion, and provide an algorithm that meets this bound for con- nected topologies using no more

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

    Microsoft Academic Search

    Dhritiman Banerjee; Biswanath Mukherjee

    1996-01-01

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

  14. Wavelength-selective detection and wavelength monitoring using optical waveguide photodetectors

    NASA Astrophysics Data System (ADS)

    Jessop, Paul E.; Densmore, Adam S.

    1998-12-01

    Quantum well waveguide photodetectors that contain two inline segments have been used as wavelength monitors with sensitivities in the picometer range. Multi-segment detectors can also be configured as wavelength demultiplexers to separate up to four optical communications channels. We review recent work in this area and report on the use of a wavelength monitor for the 1.55 micrometers region in a fiber optic strain sensor application.

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

    PubMed

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

    2014-08-25

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

  16. Millimeter wavelength spectroscopy and continuum studies of the planets

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  17. Wavelength-Selective Photovoltaics for Power-generating Greenhouses

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    PubMed Central

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

    2014-01-01

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

  19. Dual-wavelength InP quantum dot lasers

    SciTech Connect

    Shutts, S.; Smowton, P. M. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Krysa, A. B. [EPSRC National Centre for III-V Technologies, Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2014-06-16

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

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

    SciTech Connect

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

    2010-03-15

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

  1. Plasmonic All-Optical Tunable Wavelength Shifter

    SciTech Connect

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

    2007-12-01

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

  2. Two wavelength satellite laser ranging using SPAD

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  3. Wavelength-tunable silicon microring modulator.

    PubMed

    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

    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

  4. Dynamic polarizabilities and magic wavelengths for dysprosium

    SciTech Connect

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

    2011-03-15

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

  5. Dynamic polarizabilities and magic wavelengths for dysprosium

    E-print Network

    Dzuba, V A; Lev, Benjamin L

    2010-01-01

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

  6. Lithographic spiral antennas at short wavelengths

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  7. Wavelength-codified fiber laser hydrogen detector

    NASA Astrophysics Data System (ADS)

    Ortigosa-Blanch, A.; Díez, A.; González-Segura, A.; Cruz, J. L.; Andrés, M. V.

    2005-11-01

    We report a scheme for an optical hydrogen detector that codifies the information in wavelength. The system is based on an erbium-doped fiber laser with two coupled cavities and a Palladium-coated tapered fiber within one of the laser cavities. The tapered fiber acts as the hydrogen-sensing element. When the sensing element is exposed to a hydrogen atmosphere, its attenuation decreases changing the cavity losses. This change leads the system to switch lasing from the wavelength of the auxiliary cavity to the characteristic wavelength of the cavity which contains the sensing element. The detection level can be shifted by adjusting the reflective elements of the cavity containing the sensing element.

  8. Effects of Laser Wavelength on Ablator Testing

    NASA Technical Reports Server (NTRS)

    White, Susan M.

    2014-01-01

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

  9. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    Schlueter, R.D.

    1994-12-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  10. Undulators for short wavelength FEL amplifiers

    SciTech Connect

    Schlueter, R. [Lawrence Berkeley Lab., CA (United States). Accelerator and Fusion Research Div.

    1994-08-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FELs, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

  11. Undulators for short wavelength FEL amplifiers

    NASA Astrophysics Data System (ADS)

    Schlueter, R.

    1994-08-01

    Issues critical to the design of undulators for use in short wavelength FEL amplifiers, such as attainable on-axis field strength, device compactness, field quality, required magnetic gap, and strong focusing schemes, are discussed. The relative strength of various undulator technologies, including pure permanent magnet, hybrid, warm electromagnetic, pulsed, and superconducting electromagnetic devices in both helical and planar configurations are reviewed. Favored design options for proposed short wavelength FEL's, such as the Linac Coherent Light Source at SLAC and the DUV Free-Electron Laser at BNL, are presented.

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

    NASA Astrophysics Data System (ADS)

    Lively, Erica

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

  13. Dual-Wavelength Vertical-Cavity Surface-Emitting Laser Arrays Fabricated by Nonplanar Wafer Bonding

    E-print Network

    Bowers, John

    Dual-Wavelength Vertical-Cavity Surface-Emitting Laser Arrays Fabricated by Nonplanar Wafer Bonding active regions integrated on a common mirror by nonplanar wafer bonding. WDM systems and next and electrical functionality. Fabricating these highly versatile chips requires wafer-scale integration

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

    E-print Network

    Yu, Edward T.

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

  15. Compact and Low Power Consumption Hybrid Integrated Wavelength Tunable Laser Module Using Silicon Waveguide Resonators

    Microsoft Academic Search

    Nobuhide Fujioka; Tao Chu; Masashige Ishizaka

    2010-01-01

    Silicon photonics is expected to reduce size and cost of photonic devices and realize large scale photonic integrated circuits for telecom and datacom applications. In this paper, we demonstrate a compact wavelength tunable laser module using hybrid integrated semiconductor optical amplifier and silicon waveguide resonators. The power consumption of the laser module is 1 W to obtain +8 dBm fiber

  16. Discrete wavelength-locked external cavity laser

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  17. Engineering polarization entanglement at telecom wavelengths

    E-print Network

    Paris-Sud XI, Université de

    photonic bandwidths ranging from 25 MHz to 1 THz, and creating any two-photon state. OCIS codes: 270]. The association of standard low-loss optical fibers and reliable guided-wave components make it possible to create and distribute photonic entanglement in the telecom C-band of wavelengths (1530-1565nm). In addition

  18. A differential radiometer for mm wavelengths

    Microsoft Academic Search

    L. Piccirillo; M. Calabresi; M. Zucchetti

    1992-01-01

    The performance of an antenna system operating at millimeter wavelengths is discussed. Results from several measurements under different test conditions are presented. The antenna was used to make observations from Antarctica of the diffuse sky emission at 94 GHz. The instrument was used with the 94-GHz detector during the 1989\\/90 Italian Antarctica Expedition. Emission from both the Small and the

  19. Wavelengths effective in induction of malignant melanoma

    Microsoft Academic Search

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

    1993-01-01

    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

  20. Long wavelength magnetic fluctuations in toroidal plasmas

    SciTech Connect

    Hegna, C.C.; Callen, J.D.

    1992-10-01

    Fluctuating bootstrap currents provide a mechanism for long wavelength electromagnetic fluctuations in tokamak plasmas. The existence of micro-magnetic islands may be responsible for the experimental observations of core density fluctuations. A fluctuation model is introduced for the tokamak that describes the magnetic topology as a time-varying mix of magnetic islands, stochastic zones and ``good`` magnetic surfaces.

  1. Long wavelength magnetic fluctuations in toroidal plasmas

    SciTech Connect

    Hegna, C.C.; Callen, J.D.

    1992-10-01

    Fluctuating bootstrap currents provide a mechanism for long wavelength electromagnetic fluctuations in tokamak plasmas. The existence of micro-magnetic islands may be responsible for the experimental observations of core density fluctuations. A fluctuation model is introduced for the tokamak that describes the magnetic topology as a time-varying mix of magnetic islands, stochastic zones and good'' magnetic surfaces.

  2. Photospheric spectrum line asymmetries and wavelength shifts

    Microsoft Academic Search

    D. Dravins

    1982-01-01

    Results of studies on the asymmetries of spectral lines that have hitherto been regarded as symmetric are discussed. The discrepancy between solar and laboratory wavelengths is summarized, including the limb effect. Solar line profiles have been accurately measured, revealing intrinsic asymmetries in the lines. The causes of asymmetries and shifts can be traced back to photospheric inhomogeneities, so that high

  3. Wavelength switching components for future photonic networks

    Microsoft Academic Search

    Ian White; Richard Penty; Matthew Webster; Yew Jun Chai; Adrian Wonfor; Sadegh Shahkooh

    2002-01-01

    This article provides a review of integrated laser and semiconductor optical amplifier components that have been configured to provide a variety of all-optical functions such as wavelength conversion, routing, signal regeneration, and add-drop multiplexing. The components have been devised so that they can be reliably and simply used within a multiwavelength network. The article introduces the components by outlining the

  4. Wavelength selection for imaging hemoglobin in skin

    Microsoft Academic Search

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

    2000-01-01

    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

  5. Electricity and short wavelength radiation generator

    DOEpatents

    George, E.V.

    1985-08-26

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

  6. Four-wavelength retinal vessel oximetry

    Microsoft Academic Search

    Jonathan Jensen Drewes

    1999-01-01

    This dissertation documents the design and construction of a four-wavelength retinal vessel oximeter, the Eye Oximeter (EOX). The EOX scans low-powered laser beams (at 629, 678, 821 and 899 nm) into the eye and across a targeted retinal vessel to measure the transmittance of the blood within the vessel. From the transmittance measurements, the oxygen saturation of the blood within

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

    PubMed Central

    Monaco, Giulio; Giordano, Valentina M.

    2009-01-01

    On the macroscopic scale, the wavelengths of sound waves in glasses are large enough that the details of the disordered microscopic structure are usually irrelevant, and the medium can be considered as a continuum. On decreasing the wavelength this approximation must of course fail at one point. We show here that this takes place unexpectedly on the mesoscopic scale characteristic of the medium range order of glasses, where it still works well for the corresponding crystalline phases. Specifically, we find that the acoustic excitations with nanometric wavelengths show the clear signature of being strongly scattered, indicating the existence of a cross-over between well-defined acoustic modes for larger wavelengths and ill-defined ones for smaller wavelengths. This cross-over region is accompanied by a softening of the sound velocity that quantitatively accounts for the excess observed in the vibrational density of states of glasses over the Debye level at energies of a few milli-electronvolts. These findings thus highlight the acoustic contribution to the well-known universal low-temperature anomalies found in the specific heat of glasses. PMID:19240211

  8. Wavelength-tunable electrooptic polarization conversion in birefringent waveguides

    Microsoft Academic Search

    Fred Heismann; Rod C. Alferness

    1988-01-01

    Wavelength-tunable, electrooptic polarization conversion in a birefringenet waveguide accomplished with a multiple cascade of alternating TE-to-TM mode converter and TE\\/TM phase shifter sections is analylzed. Such polarization converters have been demonstrated in LiNbO3 and have been used as electrooptically tunable narrowband (Delta-wavelength less than phase-match condition wavelength\\/1000) wavelength filters with tuning ranges of at least phase-match condition wavelength\\/200. Here, it

  9. Tunable dual-wavelength all-PM fiber ring laser

    Microsoft Academic Search

    Raymond M. Sova; Chang-Seok Kim; Jin U. Kang

    2002-01-01

    A multisegment all-PM fiber ring laser is constructed to demonstrate a tunable dual-wavelength laser source with continuous tuning in absolute wavelength and discrete tuning in wavelength spacing. The tuning method is based on birefringence filtering properties of a segmented all-PM fiber ring resonator. Using this method, we show a discrete wavelength spacing of dual-wavelength output from 0.9 to 2.5 nm,

  10. Measurement of discontinuous surfaces using multiple-wavelength interferometry

    Microsoft Academic Search

    Paul Kumar Upputuri

    2009-01-01

    Interferometric surface profilers using a single wavelength offer excellent vertical resolution, but have an ambiguity-free range of less than half a wavelength. Multiple-wavelength or white light interference techniques are used to overcome the problem. We discuss a three-wavelength interferometric technique used with a phase-shifting phase evaluation procedure. The phase evaluation at the three wavelengths gives wrapped phase at any pixel

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

    PubMed

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

    2014-06-01

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

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

    E-print Network

    Dyudina, Ulyana A; Ewald, Shawn P; Wellington, Danika

    2015-01-01

    The first observations of Saturn's visible-wavelength aurora were made by the Cassini camera. The aurora was observed between 2006 and 2013 in the northern and southern hemispheres. The color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000-1500 km above the horizon. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with laboratory simulated auroras. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs between 70 and 80 degree latitude north and between 65 and 80 degree latitude south, which sometimes spiral around the pole, and sometimes form double arcs. A large 10,000-km-scale longitudinal brightness structure persists for more than 100 hours. This structure rotates approximately together with Saturn. On top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. These brightenings repeat with a period of about 1 hour....

  13. Multi-wavelength fluorometry for anaerobic digestion process monitoring.

    PubMed

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

    2005-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Richards, Mark A.; Hager, Bradford H.

    1989-01-01

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

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

    PubMed

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

    2013-01-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2015-03-01

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

  18. Diffuse optical tomography using wavelength-swept laser

    NASA Astrophysics Data System (ADS)

    Cho, Jaedu; Lim, Gukbin; Jeong, Myung Yung; Nalcioglu, Orhan; Kim, Chang-Seok; Gulsen, Gultekin

    2013-03-01

    The design and implementation of a diffuse optical tomography system using wavelength-swept laser is described. Rapid and continuous wavelength change is utilized for high speed spectral scanning from 775 nm to 875 nm optical wavelength. Maximum speed of wavelength repetition is 1 kHz and averaged output power of the wavelength-swept laser is 20 mW. A fiber-optic Sagnac interferometer is incorporated to conduct passive amplitude modulation of the wavelength-swept laser. It is shown that the wavelength-swept laser can be successfully incorporated to the DOT system, and then reduces wavelength-shifting time and hardware complexity in multi-wavelength DOT implementation.

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

    Microsoft Academic Search

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

    1985-01-01

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

  20. Discrete Wavelength-Locked External Cavity Laser

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S.; Silver, Joel A.

    2004-01-01

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

  1. Radio Wavelength Transients: Current and Emerging Prospects

    E-print Network

    J. Lazio

    2008-01-18

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

  2. Eye-safe visible wavelength lidar

    NASA Technical Reports Server (NTRS)

    Cooley, T. W.; Reagan, J. A.

    1992-01-01

    Recent technological advances on several fronts offer the possibility for relatively low-cost, eye-safe visible-wavelength lidar systems for autonomous aerosol/environmental monitoring applications. Improved silicon photodiodes and avalanche photodiodes that have become available offer high-quantum-efficiency detection at very low dark counts (10 to 1000 count/s) and can be used in a photon counting mode for signal plus background and dark current photoelectron count rates of megahertz. The essential requirements and features of a possible lidar system that capitalizes on technical advances on several fronts are outlined. A baseline lidar system is suggested for monitoring tropospheric and stratospheric aerosols. Sensitivity to wavelength, background radiation, detector characteristics, and other system parameters is discussed for several simulated data sets.

  3. Intrinsically stable light source at telecom wavelengths

    E-print Network

    Monteiro, Fernando; Sanguinetti, Bruno; Zbinden, Hugo

    2013-01-01

    We present a highly stable light source at telecom wavelengths, based on a short erbium doped fiber. The high stability arises from the high inversion of the Er3+ion population. This source is developed to work as a stable reference in radiometric applications and is useful in any application where high stability and/or a large bandwidth are necessary. The achieved long-term stability is 10 ppm.

  4. Review -EM Waves Wavelengths of 108 to

    E-print Network

    Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University

    #12;Review - EM Waves EM Waves Wavelengths of 108 to 10-16 meters (10-1024 Hz) Traveling wave) given by BES rrr ×= 0 1 )(sin 111 22 0 2 00 tkxE c E c EBS m -=== Review - EM Waves 2 0 1 mpeak E c pr = c I pr = c I pr 2 = Total absorption Total reflection EM Waves: Radiation pressure #12;Source

  5. Using large radio telescopes at decametre wavelengths

    Microsoft Academic Search

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

    2004-01-01

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

  6. Thermal behavior of millimeter wavelength radio telescopes

    Microsoft Academic Search

    Albert Greve; Michel Dan; Juan Penalver

    1992-01-01

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

  7. Radio wavelength transients: Current and emerging prospects

    Microsoft Academic Search

    J. Lazio

    2008-01-01

    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

  8. Deformable mirror for short wavelength applications

    DOEpatents

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

    1999-01-01

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

  9. Multiple wavelength X-ray monochromators

    DOEpatents

    Steinmeyer, Peter A. (Arvada, CO)

    1992-11-17

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

  10. Gas sensing using wavelength modulation spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  11. Multiple wavelength X-ray monochromators

    DOEpatents

    Steinmeyer, P.A.

    1992-11-17

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

  12. Wavelength meter having single mode fiber optics multiplexed inputs

    DOEpatents

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

    1993-01-01

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

  13. Wavelength meter having single mode fiber optics multiplexed inputs

    DOEpatents

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

    1993-02-23

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

  14. Short communication Routing and wavelength assignment for core-based

    E-print Network

    Yang, Mei

    -based tree (CBT) service in a wavelength-di- vision-multiplexing (WDM) network, where k sources need to send from sources to the core with the constraint of wavelength collision free. To address different

  15. SAGE 3: A visible wavelength limb sounder

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  16. ISO'S SHORT WAVELENGTH SPECTROMETER ULTIMATE SENSITIVITY

    E-print Network

    effects. For instance, for the small (120 \\Theta120 ¯m) InSb diode­detectors, which hardly have any memory/s 1 In:Sb 0.6 0.6 ­ 1.0 2 Si:Ga 0.6 1.5 ­ 3.5 3 Si:As BIBIB 0.5 4 ­ 5 4 Ge:Be 0.9 5 ­ 15 5 Si:Sb 0.5 2, the in­orbit noise levels of the Short Wavelength Spectrometer (SWS) detectors show a sig­ nificant

  17. Single-Photon Detection at Telecom Wavelengths

    NASA Astrophysics Data System (ADS)

    Sun, Zhi-Bin; Ma, Hai-Qiang; Lei, Ming; Wang, Di; Liu, Zhao-Jie; Yang, Han-Dong; Wu, Ling-An; Zhai, Guang-Jie; Feng, Ji

    2007-02-01

    A single-photon detector based on an InGaAs avalanche photodiode has been developed for use at telecom wavelengths. A suitable delay and sampling gate modulation circuit are used to prevent positive and negative transient pulses from influencing the detection of true photon induced avalanches. A monostable trigger circuit eliminates the influence of avalanche peak jitter, and a dead time modulation feedback control circuit decreases the afterpulsing. From performance tests we find that at the optimum operation point, the quantum efficiency is 12% and the dark count rate 1.5×10-6 ns-1, with a detection rate of 500 kHz.

  18. Two wavelength division multiplexing WAN trials

    SciTech Connect

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

    1995-01-20

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

  19. Galactic emission at decimeter wavelengths (Platania+, 2003)

    Microsoft Academic Search

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

    2003-01-01

    The diffuse galactic emission maps at decimeter wavelengths (408 MHz, Haslam et al., 1982A&AS...47....1H), (1420 MHz, Reich, 1982A&AS...48..219R, Reich & Reich 1986A&AS...63..205R), (2326 MHz, Jonas et al., 1998MNRAS.297..977J) have been destriped using the method proposed by Schlegel et al., 1998ApJ...500..525S. Statistical and systematic errors have been evaluated for each map. Each map is presented in two different pixelizations: ECP (Cartesian

  20. Wavelength stabilization of semiconductor lasers with a tunable photodetector

    Microsoft Academic Search

    Lorenzo Colace; Gianlorenzo Masini; Gaetano Assanto

    2002-01-01

    We introduce an approach to stabilizing the wavelength of a semiconductor laser employing a voltage-tunable photodetector. The latter provides a bipolar error signal driving a feedback loop for the laser retuning. We demonstrate wavelength stabilization within +\\/-25 pm in the 1.55 mum window. Performances, system compactness, and integrability make the approach quite appealing for use in dense wavelength division multiplexing

  1. CO2 probe laser with rapid wavelength switching

    Microsoft Academic Search

    S. Holly; S. Aiken

    1977-01-01

    The paper outlines the design and potential of a low-power wavelength switching CO2 probe laser that switches its operating wavelength at a rapid rate in a controlled manner, allowing a stable output at each wavelength for a period long enough to make the necessary gain measurements. The design of the probe laser concentrates on solving two problems, viz., to move

  2. Analysis of Supportable Rates in Symmetric Blocking Wavelength Routers

    E-print Network

    Koksal, Can Emre

    Analysis of Supportable Rates in Symmetric Blocking Wavelength Routers Can Emre Koksal EPFL School-- Constructing an n × n non-blocking wavelength router using n × 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

  3. Adaptive wavelength routing in all-optical networks

    Microsoft Academic Search

    Ahmed Mokhtar; Murat Azizo?lu

    1998-01-01

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

  4. Wavelength conversion experiment using fiber four-wave mixing

    Microsoft Academic Search

    Kyo Inoue; Hiromu Toba

    1992-01-01

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

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

    PubMed

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

    2014-08-25

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

  6. Multi-wavelength Study Of The Cygnus Loop

    NASA Astrophysics Data System (ADS)

    Leahy, Denis A.

    2006-06-01

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

  7. Progress in extended wavelength VCSEL technology

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  8. The chromosphere above sunspots at millimeter wavelengths

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  9. A wavelength tunable 2-ps pulse VECSEL

    NASA Astrophysics Data System (ADS)

    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

    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.

  10. Wavelength-Spacing Tunable Multi-wavelength Fiber Lasers Based on Hybrid Gain Medium and Mach-Zehnder Interferometer

    Microsoft Academic Search

    Daru Chen; Shan Qin; Ying Gao; Sailing He

    2007-01-01

    Wavelength-spacing continuously tunable multi-wavelength fiber lasers based on a Mach-Zehnder interferometer comb filter are achieved. Stable multi-wavelength lasing based on hybrid gains of Erbium-doped fiber amplification and fiber Raman amplification (semiconductor optical amplification) is demonstrated.

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

    DOEpatents

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

    2002-01-01

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

  12. Tunable optical tweezers for wavelength-dependent measurements

    PubMed Central

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

    2012-01-01

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

  13. Photoluminescence Study of Long Wavelength Superlattice Infrared Detectors

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  15. Long-Wavelength Infrared (LWIR) Quantum Dot Infrared Photodetector (QDIP) Focal Plane Array

    Microsoft Academic Search

    S. D. Gunapala; S. V. Bandara; K. Liu; C. J. Hill; S. B. Rafol; J. M. Mumolo; E. R. Blazejewski

    We have exploited the artificial atomlike properties of epitaxially self-assembled quantum dots for the development of high operating temperature long wavelength idrared (LWlR) focal plane arrays. Quantum dots are nanometer-scale islands that form spontaneously on a semiconductor substrate due to lattice mismatch. QDTPs are expected to outperform quantum well infrared detectors (QWIPs) and are expected to offer significant advantages over

  16. Measurements of the wavelength dependence and other properties of stellar scintillation at Mauna Kea, Hawaii

    NASA Astrophysics Data System (ADS)

    Dainty, J. C.; Levine, B. M.; Brames, B. J.; Odonnell, K. A.

    1982-04-01

    Photon counting and on-line digital analysis techniques are used to measure the intensity variance of stellar scintillation as a function of wavelength, with experimental results that are consistent with those predicted by the theory of Tatarski (1967). Time scales in the 1.7-10 msec range were observed, and the higher moments were consistently lower than those predicted by a log normal distribution.

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

    SciTech Connect

    Papin, Pallas A.

    2012-06-01

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

  18. Short-Wavelength Solar Wind Turbulence: Kinetic Alfven vs. Whistler Fluctuations

    Microsoft Academic Search

    S. Peter Gary

    2009-01-01

    The inertial range of solar wind turbulence corresponds to magnetic power spectra which scale as f^-alpha with alpha˜ 5\\/3. Many observations show, however, that at observed frequencies f ˜ 0.2 Hz, there is a ``breakpoint'' such that power spectra at higher frequencies follow a steeper power-law dependence with alpha> 5\\/3. The constituent modes of this high-frequency, short-wavelength regime are often

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-01-01

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

  1. Wavelength domain multiplexed fiber specklegram sensor

    NASA Astrophysics Data System (ADS)

    Rodriguez-Cobo, L.; Lomer, M.; Cobo, A.; Real, E.; Lopez-Higuera, J. M.

    2014-05-01

    In this work, a low-cost WDM interrogation system has been proposed and experimentally tested to obtain two independent channels of a fiber specklegram sensor. Two lasers of different wavelengths have been launched into two multimode Polymer Optical Fibers (POFs) and then combined through a coupler before their interrogation using a RBG camera. By analyzing each color of the video sequence, the two fiber channels can be independently obtained. Besides, the speckle sensitivity has been also studied by analyzing different properties of speckle patterns such as their contrast or the speckle size. The achieved results help to the development of new fiber specklegram sensors by allowing a direct comparison between two specklegrams of different properties.

  2. Innovative Long Wavelength Infrared Detector Workshop Proceedings

    NASA Technical Reports Server (NTRS)

    Grunthaner, Frank J.

    1990-01-01

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

  3. Handheld four-wavelength retinal vessel oximeter

    NASA Astrophysics Data System (ADS)

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

    2000-06-01

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

  4. An Optical Interferometer with Wavelength Dispersion

    E-print Network

    T. R. Bedding; J. G. Robertson; R. G. Marson

    1994-04-04

    MAPPIT is an optical interferometer installed at the coude focus of the 3.9-m Anglo-Australian Telescope. The instrument combines non-redundant masking with wavelength dispersion and is able to record fringes simultaneously over a wide bandwidth. For typical observations centred near 600 nm, the bandwidth is 55 nm and the spectral resolution is 3 nm. This paper describes the instrument and the data processing methods and presents some results. We find the star sigma Sgr to be a close binary; the system is only partially resolved, with a separation of (11.5 +/- 2) milliarcsec (assuming the components to have equal magnitudes). We also give angular diameter measurements of two red giant stars, alpha Sco and beta Gru. The observations of beta Gru (spectral type M5 III) resolve the star for the first time and give an equivalent uniform-disk diameter of (27 +/- 3) milliarcsec.

  5. Frequency tuning of long-wavelength VCSELs

    NASA Astrophysics Data System (ADS)

    Lytkine, A.; Jäger, W.; Tulip, J.

    2006-04-01

    Tuning properties of long-wavelength VCSELs have been studied experimentally, for the first time to our knowledge. Injection current and temperature tuning rates of two VCSELs operating near 1512 and 1577 nm have been measured using a Fabry-Perot etalon with free spectral range 0.056 cm -1. A 100-Hz saw-tooth modulation with depths of modulation of ˜10% or less was superimposed on a direct injection current (dc bias) to tune lasers in narrow spectral intervals (0.3-1.2 cm -1) around a central frequency set by the dc bias. The lasers have been found to be capable of being tuned faster at higher levels of dc bias. The enhancement factors were up to ˜2 and ˜3 for the 1512- and 1577-nm lasers, respectively, as compared with their tuning rates measured at the levels of the dc bias close to the threshold of lasing. A linear dependence between injection current tuning rates and the levels of dc bias has been observed. Temperature tuning coefficients have been proved to be independent of the laser heat sink temperature and of the dc bias. Frequency tuning curves were approximated with a second-order polynomial. The frequencies of more than 40 absorption lines of CO, CO 2, H 2O and NH 3 known from spectral databases were compared with the calculated frequencies. The accuracy of the approximation was found to be within 0.2 cm -1 for spectral intervals up to 38 cm -1. The dependence of current tuning rates of the VCSELs on dc bias was shown to be taken into account for accurate analysis of absorption line profiles. The results obtained can be used for precise spectroscopic measurements with long-wavelength VCSELs.

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

    SciTech Connect

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

    2012-05-01

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

  7. Optical wavelength selection for improved spectroscopic photoacoustic imaging?

    PubMed Central

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

    2013-01-01

    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. PMID:25302148

  8. Design of wavelength-selective waveplates using genetic algorithm

    NASA Astrophysics Data System (ADS)

    Katayama, Ryuichi

    2013-03-01

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

  9. Multiple-wavelength digital holographic interferometry using tunable laser diodes

    SciTech Connect

    Wada, Atsushi; Kato, Makoto; Ishii, Yukihiro

    2008-04-20

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

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

    E-print Network

    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

    2011-12-20

    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.

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

    NASA Technical Reports Server (NTRS)

    Jani, Mahendra G. (Inventor)

    1997-01-01

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

  12. Wire grid polarizers for visible wavelengths

    NASA Astrophysics Data System (ADS)

    Johnson, Joshua Hans

    Detailed analysis of wire-grid (WG) polarizers for visible wavelengths is presented. Rigorous coupled-wave analysis (RCWA) is used to model their performance. The optimum choice of metal for the wires is identified, and the effects of different substrate indices of refraction are considered. The polarization properties are considered with changes in the physical parameters, including period, duty cycle, and wire thickness. It is shown that the performance of WG polarizers improves with increasing angle of incidence. The effect of non-square wire profiles is considered, as is the effect of adding additional dielectric layers between the wires and the substrate. The effect of metal oxide layers forming on the wires is also modeled. While most of this work concerns WG polarizers used in transmission, the performance in reflection is also discussed. Several visible-wavelength WG polarizers were fabricated at the Cornell Nanofabrication Facility (CNF) in Ithaca, NY. Electron-beam lithography was used to write the patterns for these devices, and two different methods of pattern transfer were compared. These were the lift-off method and reactive-ion etching (RIE). We found that lift-off could not produce wires thick enough for good polarization properties. RIE could produce much thicker wires with good profiles and was used for all of the experimental work presented here. Two different methods for metal film deposition, evaporation and sputtering were also compared. Films deposited by sputtering were found to have much lower indices of refraction and to not respond to etching as well. Thermally evaporated films performed much better in WG polarizers. Alternative methods for the mass-production of visible-wavelength WG polarizers are also discussed. The performance of the fabricated WG polarizers is compared to theory. When the measured physical parameters are used in RCWA to predict the performance, the measured extinction ratio is found to be much lower than the predicted result in all cases. The measured transmission coefficient was somewhat higher than predicted by theory. These discrepancies occurred regardless of the film deposition or pattern transfer process used. Three different models are compared to explain these differences. These are the size effect, an effective-medium theory, and an increased oxide thickness model. The best model is found to be an increased oxide thickness on the wires. As the film is etched, previously unexposed grain boundaries and pores in the films become exposed to the atmosphere, allowing oxygen to enter the wires and oxidize them. Modeling this excess oxidation as an increased oxide thickness on the wires gives excellent agreement between theory and experiment. Measured changes in the polarization properties with changing physical parameters are found to agree with the theoretical predictions. The performance of several commercially-available visible polarizers are also measured and compared. Finally, some methods for enhancing the performance further are discussed.

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

    PubMed

    Sahin, Levent; Figueiro, Mariana G

    2013-05-27

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

  14. Using wavelength and slope to infer the historical origin of semiarid vegetation bands.

    PubMed

    Sherratt, Jonathan A

    2015-04-01

    Landscape-scale patterns of vegetation occur worldwide at interfaces between semiarid and arid climates. They are important as potential indicators of climate change and imminent regime shifts and are widely thought to arise from positive feedback between vegetation and infiltration of rainwater. On gentle slopes the typical pattern form is bands (stripes), oriented parallel to the contours, and their wavelength is probably the most accessible statistic for vegetation patterns. Recent field studies have found an inverse correlation between pattern wavelength and slope, in apparent contradiction with the predictions of mathematical models. Here I show that this "contradiction" is based on a flawed approach to calculating the wavelength in models. When pattern generation is considered in detail, the theory is fully consistent with empirical results. For realistic parameters, degradation of uniform vegetation generates patterns whose wavelength increases with slope, whereas colonization of bare ground gives the opposite trend. Therefore, the empirical finding of an inverse relationship can be used, in conjunction with climate records, to infer the historical origin of the patterns. Specifically, for the African Sahel my results suggest that banded vegetation originated by the colonization of bare ground during circa 1760-1790 or since circa 1850. PMID:25831503

  15. Wavelength encoding technique for particle analyses in hematology analyzer

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  16. Design of a variable optical attenuator with wavelength selectivity

    Microsoft Academic Search

    Tsair-Liang Tsai; Jieh-Chian Wu

    2010-01-01

    We propose a theoretical design of a high-speed wavelength-selective variable optical attenuator (VOA) constructed by a waveguide-type\\u000a Raman amplifier and two directional couplers. The VOA can attenuate each incident WDM wavelength individually and simultaneously\\u000a in a few tens of picoseconds by applying the corresponding pumping wavelength to the Raman amplifier. We define two operation\\u000a modes, which may allow the attenuation

  17. Phased-array wavelength demultiplexers and their integration with photodetectors

    Microsoft Academic Search

    M. R. Amersfoort

    1994-01-01

    Wavelength Division Multiplexing (WDM) exploits the huge bandwidth of the optical fiber by parallel transmission of several independent channels located at different wavelengths and in addition has the potential of all-optical routed networks. A key component in such a WDM-system is a low-loss wavelength demultiplexer for spatial separation of the different channels. This thesis describes the design, realization and characterization

  18. Optimal Placement of Wavelength Converters in Trees and Trees of Rings*

    E-print Network

    $ Ophir Frieder 5 Abstract In wavelength routed optical networks, wavelength converters can potentially, Chicago, IL 60616. Email: ophir@cs.iit.edu. 1 Introduction In wavelength routed WDM (wavelength

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  20. Flux monitoring of Sagittarius A* at mm-wavelengths

    NASA Astrophysics Data System (ADS)

    Miyazaki, Atsushi; Shen, Zhi-Qiang; Miyoshi, Makoto; Tsuboi, Masato; Tsutsumi, Takahiro

    2006-12-01

    We performed the monitoring observations of the fbx density toward the Galactic center compact radio source, Sagittarius A* (Sgr A*), which is associated with a supermassive black hole, since 1996 using the Nobeyama Millimeter Array (NMA). The monitoring observations of Sgr A* were carried out in the 3- and 2-mm (100 and 140 GHz) bands over one to several months on each NMA observable season. We have detected several fares of Sgr A * with duration of, roughly, one month. The fbx density at the fare peak increases 100% 200% at 100 GHz band and 200% 400% at 140 GHz band, respectively, while the averaged quiescent fbx density was about 1 Jy. We also found some intraday variations (IDVs) of Sgr A* at both 2- and 3-mm bands. The shortest twofold increase timescale of the IDV is estimated to be about 1.5 hr at 140 GHz. This short timescale variability suggests that the physical size of emitting region is compact on a scale at or below about 12 AU (~150 RS). The IDV at mm-wavelengths has a similar increase timescale as those in the X-ray and infrared fares but has a smaller amplitude.

  1. Original article The influence of light wavelength on reproductive

    E-print Network

    Paris-Sud XI, Université de

    blackheaded bunting (Emberiza melanocephala) Sangeeta RANI, Sudhi SINGH, Manju MISRA, Vinod KUMAR* Department wavelength on reproductive photorefractoriness in the migratory male blackheaded bunting held under long

  2. Smoke optical depths - Magnitude, variability, and wavelength dependence

    NASA Technical Reports Server (NTRS)

    Pueschel, R. F.; Russell, P. B.; Colburn, D. A.; Ackerman, T. P.; Allen, D. A.

    1988-01-01

    An airborne autotracking sun-photometer has been used to measure magnitudes, temporal/spatial variabilities, and the wavelength dependence of optical depths in the near-ultraviolet to near-infrared spectrum of smoke from two forest fires and one jet fuel fire and of background air. Jet fuel smoke optical depths were found to be generally less wavelength dependent than background aerosol optical depths. Forest fire smoke optical depths, however, showed a wide range of wavelength depedences, such as incidents of wavelength-independent extinction.

  3. Four-Photon Quantum Interferometry at a Telecom Wavelength

    E-print Network

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

    2011-12-09

    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.

  4. Designing scalable WDM optical interconnects using predefined wavelength conversion

    NASA Astrophysics Data System (ADS)

    Hamza, Haitham S.; Deogun, Jitender S.

    2006-05-01

    We investigate the problem of designing scalable wavelength division multiplexing (WDM) optical interconnects with reduced hardware complexity. We present a new WDM interconnect based on the well-known three-stage Clos network. For scalability purposes, any wavelength conversion occurs between two predefined wavelengths, eliminating the need for any full- or wide-range wavelength converters. We show that the new design provides better scalability at a reduced hardware complexity compared with most of the recent best interconnect designs. We also show that the proposed interconnect admits existing routing algorithms for the three-stage space Clos network with simple extensions.

  5. Two-wavelength laser interferometry using superheterodyne detection.

    PubMed

    Dändliker, R; Thalmann, R; Prongué, D

    1988-05-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  7. Chandra Multi-wavelength Plane Survey

    NASA Astrophysics Data System (ADS)

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

    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.

  8. Array of Bolometers for Submillimeter- Wavelength Operation

    NASA Technical Reports Server (NTRS)

    Bock, James; Turner, Anthony

    2007-01-01

    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.

  9. Neutron scintillators using wavelength shifting fibers

    SciTech Connect

    Hutchinson, D.P.; Miller, V.C.; Ramsey, J.A.

    1995-06-01

    A proposed design for an optically-based, one-dimension scintillation detector to replace the gas-filled position-sensitive proportional counter currently used for a wide-angle neutron detector (WAND) at the high-Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory (ORNL) is presented. The scintillator, consisting of a mixture of {sup 6}LiF and ZnS(Ag) powders in an epoxy binder, is coupled to an array of wavelength shifting optical fibers which provide position resolution. The wide-angle neutron detector is designed to cover a 120 degree arc with a 75 cm radius of curvature. The final detector design provides for 600 optical fibers coupled to the scintillator screen with an angular resolution of 0.2 degrees. Each individual pixel of the detector will be capable of operating at count rates exceeding 1 MHz. Results are presented from the measurement of neutron conversion efficiencies for several screen compositions, gamma-ray sensitivity, and spatial resolution of a 16 element one-dimensional array prototype.

  10. OPS laser EPI design for different wavelengths

    NASA Astrophysics Data System (ADS)

    Moloney, J. V.; Hader, J.; Li, H.; Kaneda, Y.; Wang, T. S.; Yarborough, M.; Koch, S. W.; Stolz, W.; Kunert, B.; Bueckers, C.; Chaterjee, S.; Hardesty, G.

    2009-02-01

    Design of optimized semiconductor optically-pumped semiconductor lasers (OPSLs) depends on many ingredients starting from the quantum wells, barrier and cladding layers all the way through to the resonant-periodic gain (RPG) and high reflectivity Bragg mirror (DBR) making up the OPSL active mirror. Accurate growth of the individual layers making up the RPG region is critical if performance degradation due to cavity misalignment is to be avoided. Optimization of the RPG+DBR structure requires knowledge of the heat generation and heating sinking of the active mirror. Nonlinear Control Strategies SimuLaseTM software, based on rigorous many-body calculations of the semiconductor optical response, allows for quantum well and barrier optimization by correlating low intensity photoluminescence spectra computed for the design, with direct experimentally measured wafer-level edge and surface PL spectra. Consequently, an OPSL device optimization procedure ideally requires a direct iterative interaction between designer and grower. In this article, we discuss the application of the many-body microscopic approach to OPSL devices lasing at 850nm, 1040nm and 2?m. The latter device involves and application of the many-body approach to mid-IR OPSLs based on antimonide materials. Finally we will present results on based on structural modifications of the epitaxial structure and/or novel material combinations that offer the potential to extend OPSL technology to new wavelength ranges.

  11. Visible-wavelength semiconductor lasers and arrays

    DOEpatents

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

    1996-01-01

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

  12. Underdense radiation sources: Moving towards longer wavelengths

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

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

  13. Sub-wavelength plasmonic modes in a conductor-gap-dielectric system with a nanoscale gap.

    PubMed

    Avrutsky, Ivan; Soref, Richard; Buchwald, Walter

    2010-01-01

    We study guided modes in a conductor-gap-dielectric (CGD) system that includes a low-index dielectric gap layer of deep sub-wavelength thickness sandwiched between a conductor and a high-index dielectric cladding. Analysis of the dispersion equation for CGD modes provides an analytical estimation for the cut-off thickness of the gap layer. This guided mode is unusual because it exists when the gap thickness is less than the cutoff thickness. In the direction normal to the interfaces, the modal electric field is tightly confined within the gap. Sub-wavelength lateral mode confinement is readily provided by a spatial variation of the gap-layer thickness: the modal field localizes at the narrowest gap. Various lateral confinement schemes are proposed and verified by numerical simulations. Possible applications of CGD modes include surface-plasmon nano-lasers (SPASERs) and sensors. If these plasmonic waveguides are scaled for operation at far infrared rather than telecomm wavelengths, then the propagation losses are dramatically reduced, thereby enabling the construction of practical chip-scale plasmonic integrated circuits or PLICs. PMID:20173855

  14. Crater Floor Slope as a Measure of Long-wavelength Changes in Topography on Mercury

    NASA Astrophysics Data System (ADS)

    Balcerski, J.; Hauck, S. A.; Barnouin, O. S.; Neumann, G. A.; Oberst, J.; Phillips, R. J.; Preusker, F.; Solomon, S. C.; Zuber, M. T.

    2011-12-01

    During the course of three flybys and an orbital mission phase that began on 18 March 2011, the MESSENGER spacecraft has been performing a detailed survey of Mercury in order to characterize the planet's origin and evolution. Precise topographic information about the surface of Mercury is being collected by the Mercury Laser Altimeter (MLA), largely over the northern hemisphere where the spacecraft slant range from the surface is less than 1500 km. Complementary knowledge of surface relief is gained through stereographic imaging by the Mercury Dual Imaging System (MDIS). Analysis of stereographic images returned during MESSENGER's first flyby of Mercury revealed, and orbital MLA profiles have confirmed, the presence of unexpected long-wavelength topography within and adjacent to the Caloris impact basin. In particular, basin topography is far from radially symmetric, and portions of the northern basin floor lie at higher elevation than the nearby basin rim. The anomalously high areas of basin floor appear to be part of a larger-scale topographic variation that extends outside the basin. To assess the nature and development time of this long-wavelength topography we examine surface features that may have been tilted during its formation. In particular, we investigate the idea that the slopes of the floors of nominally flat-floored impact craters within and near the Caloris basin may, depending on their age, reflect changes in long-wavelength slopes associated with the large-scale topography. Whereas floor slopes for individual craters may be the result of any of several volcanic, tectonic, or impact processes, a large-scale organization of slope direction and magnitude can be an indicator of a common origin. Results from the measurement of crater floor slopes from MLA profiles across the northern Caloris region of Mercury reveal that a majority of flat crater floors profiled by MLA have along-track slopes between ~0.25 and 1.5°. Moreover, the magnitudes and along-track slope directions of these crater floors are generally spatially correlated with the long-wavelength slope of the Caloris floor topography. Ongoing collection of topographic profiles by MLA will serve to extend the statistical sample of craters that may have been influenced by the development of this large-scale feature as well as permit estimation of cross-track slopes for some craters, both crucial for understanding its development. Results to date also suggest that measurement of post-impact tilting of crater floors may provide a means more generally to assess the existence and development of comparable late-stage long-wavelength surface deformation across the planet.

  15. Ultra-broadband wavelength-swept Tm-doped fiber laser using wavelength-combined gain stages.

    PubMed

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

    2015-01-12

    A wavelength-swept thulium-doped fiber laser system employing two parallel cavities with two different fiber gain stages is reported. The fiber gain stages were tailored to provide emission in complementary bands with external wavelength-dependent feedback cavities sharing a common rotating polygon mirror for wavelength scanning. The wavelength-swept laser outputs from the fiber gain elements were spectrally combined by means of a dichroic mirror and yielded over 500 mW of output with a scanning range from ~1740 nm to ~2070 nm for a scanning frequency of ~340 Hz. PMID:25835692

  16. Compressing surface plasmons for nano-scale optical focusing.

    PubMed

    Choi, Hyeunseok; Pile, David F; Nam, Sunghyun; Bartal, Guy; Zhang, Xiang

    2009-04-27

    A major challenge in optics is how to deliver and concentrate light from the micron-scale into the nano-scale. Light can not be guided, by conventional mechanisms, with optical beam sizes significantly smaller than its wavelength due to the diffraction limit. On the other hand, focusing of light into very small volumes beyond the diffraction limit can be achieved by exploiting the wavelength scalability of surface plasmon polaritons. By slowing down an optical wave and shrinking its wavelength during its propagation, optical energy can be compressed and concentrated down to nanometer scale, namely, nanofocusing. Here, we experimentally demonstrate and quantitatively measure the nanofocusing of surface plasmon polaritons in tapered metallic V-grooves down to the deep subwavelength scale - approximately lambda/40 at wavelength of 1.5 micron - with almost 50% power efficiency. PMID:19399129

  17. Structure Measurements of Leaf and Woody Components of Forests with Dual-Wavelength Lidar Scanning Data

    NASA Astrophysics Data System (ADS)

    Strahler, A. H.; Li, Z.; Schaaf, C.; Howe, G.; Martel, J.; Hewawasam, K.; Douglas, E. S.; Chakrabarti, S.; Cook, T.; Paynter, I.; Saenz, E. J.; Wang, Z.; Woodcock, C. E.; Jupp, D. L. B.; Schaefer, M.; Newnham, G.

    2014-12-01

    Forest structure plays a critical role in the exchange of energy, carbon and water between land and atmosphere and nutrient cycle. We can provide detailed forest structure measurements of leaf and woody components with the Dual Wavelength Echidna® Lidar (DWEL), which acquires full-waveform scans at both near-infrared (NIR, 1064 nm) and shortwave infrared (SWIR, 1548 nm) wavelengths from simultaneous laser pulses. We collected DWEL scans at a broadleaf forest stand and a conifer forest stand at Harvard Forest in June 2014. Power returned from leaves is much lower than from woody materials such as trunks and branches at the SWIR wavelength due to the liquid water absorption by leaves, whereas returned power at the NIR wavelength is similar from both leaves and woody materials. We threshold a normalized difference index (NDI), defined as the difference between returned power at the two wavelengths divided by their sum, to classify each return pulse as a leaf or trunk/branch hit. We obtain leaf area index (LAI), woody area index (WAI) and vertical profiles of leaf and woody components directly from classified lidar hits without empirical wood-to-total ratios as are commonly used in optical methods of LAI estimation. Tree heights, diameter at breast height (DBH), and stem count density are the other forest structure parameters estimated from our DWEL scans. The separation of leaf and woody components in tandem with fine-scale forest structure measurements will benefit studies on carbon allocation of forest ecosystems and improve our understanding of the effects of forest structure on ecosystem functions. This research is supported by NSF grant, MRI-0923389

  18. Supplementary Information ECL emission linewidth and wavelength stability analysis

    E-print Network

    Hergenrother, Paul J.

    systems utilize first-order diffraction from a grating to provide the optical feedback and wavelength selection, as in typical Littrow and Littman­Metcalf configurations.1, 2 Guided mode resonant filters and photonic crystal reflection filters have also been demonstrated as efficient wavelength selective mirrors

  19. The extra-terrestrial vacuum-ultraviolet wavelength range

    Microsoft Academic Search

    J. Gethyn Timothy; Klaus Wilhelm; Lidong Xia

    2010-01-01

    Electromagnetic radiation in the vacuum-ultraviolet (VUV) and extra-terrestrial range at wavelengths from 10 nm to 300 nm is absorbed in the upper atmosphere by ozone, molecular and atomic oxygen, and molecular nitrogen. Observations at wavelengths down to ≈ 200 nm can be carried out from stratospheric balloons, and observations below 200 nm require space platforms operating at altitudes above 250

  20. Wavelength division multiplexing and transmission of analog signals over fiber

    Microsoft Academic Search

    Willis D. Potter; Eric Donkor

    2006-01-01

    We present results from the multiplexing and transmission of amplitude modulated, frequency modulated, and video analog signals over fiber. The optical carrier's wavelengths for these signals were centered in the 1545-1560nm telecommunication wavelength regimes. A direct modulation format was used for the AM signals whereas external modulation formats were used for the FM and video signals. Standard telecommunication WDM components

  1. Dense wavelength multiplexing for a high power diode laser

    Microsoft Academic Search

    Christian Wessling; Martin Traub; Dieter Hoffmann; Reinhart Poprawe

    2006-01-01

    At present methods of polarization and wavelength multiplexing with dielectric coatings are used to increase the brightness of diode lasers. The number of suitable diode laser wavelengths is limited by the temperature- and current-dependent spectral characteristics of the diode laser and the slope of dielectric edge-filters. By use of external volume diffraction gratings it is possible to constrict the emission

  2. Wavelength stabilized high-power diode laser modules

    Microsoft Academic Search

    Bernd Köhler; Thomas Brand; Matthias Haag; Jens Biesenbach

    2009-01-01

    In this work we report on high-power diode laser modules with enhanced spectral brightness by means of volume holographic gratings for wavelength stabilization. High-power diode laser modules typically have a relatively broad spectral width of about 3 to 6 nm. In addition the center wavelength shifts by changing the temperature and the driving current, which is obstructive for pumping applications

  3. Holography, wave-length diversity and inverse scattering

    Microsoft Academic Search

    N. H. Farhat

    1980-01-01

    The use of wavelength diversity to enhance the performance of thinned coherent imaging apertures is discussed. It is shown that wavelength diversity lensless Fourier transform recording arrangements that utilize a reference point source in the vicinity of the object can be used to access the three-dimensional Fourier space of nondispersive perfectly reflecting or weakly scattering objects. Hybrid (opto-digital) computing applied

  4. Dynamic Wavelength Routing in WDM Networks via Ant Colony Optimization

    E-print Network

    Barr, Richard

    of all-optical networks is accomplished, in part, by send- ing multiple signals simultaneously through the same fiber-optic cable. This is achieved through wavelength-division multiplexing (WDM), whichDynamic Wavelength Routing in WDM Networks via Ant Colony Optimization Ryan M. Garlick1 and Richard

  5. Fast fiber-optic multi-wavelength pyrometer.

    PubMed

    Fu, Tairan; Tan, Peng; Pang, Chuanhe; Zhao, Huan; Shen, Yi

    2011-06-01

    A fast fiber-optic multi-wavelength pyrometer was developed for the ultraviolet-visible-near infrared spectra from 200 nm to 1700 nm using a CCD detector and an InGaAs detector. The pyrometer system conveniently and quickly provides the sufficient choices of multiple measurement wavelengths using optical diffraction, which avoids the use of narrow-band filters. Flexible optical fibers are used to transmit the radiation so the pyrometer can be used for temperature measurements in harsh environments. The setup and calibrations (wavelength calibration, nonlinearity calibration, and radiation response calibration) of this pyrometer system were described. Development of the multi-wavelength pyrometer involved optimization of the bandwidth and temperature discrimination of the multiple spectra data. The analysis results showed that the wavelength intervals, ??(CCD) = 30 nm and ??(InGaAs) = 50 nm, are the suitable choices as a tradeoff between the simple emissivity model assumption and the multiple signal discrimination. The temperature discrimination was also quantificationally evaluated for various wavelengths and temperatures. The measurement performance of the fiber-optic multi-wavelength pyrometer was partially verified through measurements with a high-temperature blackbody and actual hot metals. This multi-wavelength pyrometer can be used for remote high-temperature measurements. PMID:21721719

  6. Design of Wavelength Converting Switches for Optical Burst Switching

    E-print Network

    results. We study the performance of optical burst switches using wavelength converting switches based Switches, Wavelength Routers I. INTRODUCTION The transmission capacity of optical fibers has been increas the electronic line cards needed to terminate the channels from just a single fiber. Optical burst switching

  7. Calibration and performance of the ISO Long-Wavelength Spectrometer

    Microsoft Academic Search

    B. M. Swinyard; P. E. Clegg; P. A. R. Ade; C. Armand; J.-P. Baluteau; M. J. Barlow; J.-C. Berges; M. Burgdorf; E. Caux; C. Ceccarelli; R. Cerulli; S. E. Church; S. Colgan; F. Cotin; P. Cox; P. Cruvellier; G. R. Davis; A. Digiorgio; R. J. Emery; D. Ewart; J. Fischer; I. Furniss; W. M. Glencross; M. Greenhouse; M. J. Griffin; M. R. Gry; C. Haas; M. Joubert; K. J. King; T. Lim; R. Liseau; S. Lord; D. Lorenzetti; S. Molinari; D. A. Naylor; B. Nisini; A. Omont; R. Orfei; T. Patrick; D. Pequignot; D. Pouliquen; M. C. Price; Nguyen-Q-Rieu; F. D. Robinson; M. Saisse; P. Saraceno; G. Serra; S. D. Sidher; H. A. Smith; L. Spinoglio; D. Texier; W. A. Towlson; N. Trams; S. J. Unger; G. J. White

    1996-01-01

    The wavelength and flux calibration, and the in-orbit performance of the Infrared Space Observatory Long-Wavelength Spectrometer (LWS) are described. The LWS calibration is mostly complete and the instrument's performance in orbit is largely as expected before launch. The effects of ionising radiation on the detectors, and the techniques used to minimise them are outlined. The overall sensitivity figures achieved in

  8. Light-current characterization of dual-wavelength VCSELs

    Microsoft Academic Search

    Vlad Badilita; Jean-Francois Carlin; Marcel Brunner; Marc Ilegems

    2002-01-01

    The purpose of this paper is to present a detailed characterization of a dual-wavelength VCSEL - the BiVCSEL. This device consists of two active optical cavities, which share a coupling mirror and can be independently electrically pumped. We present the output powers for the two emitted wavelengths (short - (lambda) S, long - (lambda) L versus the currents in the

  9. Systematic wavelength selection for improved multivariate spectral analysis

    DOEpatents

    Thomas, Edward V. (2828 Georgia NE., Albuquerque, NM 87110); Robinson, Mark R. (1603 Solano NE., Albuquerque, NM 87110); Haaland, David M. (809 Richmond Dr. SE., Albuquerque, NM 87106)

    1995-01-01

    Methods and apparatus for determining in a biological material one or more unknown values of at least one known characteristic (e.g. the concentration of an analyte such as glucose in blood or the concentration of one or more blood gas parameters) with a model based on a set of samples with known values of the known characteristics and a multivariate algorithm using several wavelength subsets. The method includes selecting multiple wavelength subsets, from the electromagnetic spectral region appropriate for determining the known characteristic, for use by an algorithm wherein the selection of wavelength subsets improves the model's fitness of the determination for the unknown values of the known characteristic. The selection process utilizes multivariate search methods that select both predictive and synergistic wavelengths within the range of wavelengths utilized. The fitness of the wavelength subsets is determined by the fitness function F=.function.(cost, performance). The method includes the steps of: (1) using one or more applications of a genetic algorithm to produce one or more count spectra, with multiple count spectra then combined to produce a combined count spectrum; (2) smoothing the count spectrum; (3) selecting a threshold count from a count spectrum to select these wavelength subsets which optimize the fitness function; and (4) eliminating a portion of the selected wavelength subsets. The determination of the unknown values can be made: (1) noninvasively and in vivo; (2) invasively and in vivo; or (3) in vitro.

  10. Monolithic multiple wavelength tunable vertical cavity surface emitting laser array

    Microsoft Academic Search

    C. J. Chang-Hasnain; M. W. Maeda; J. P. Harbison; L. T. Florez

    1991-01-01

    The wavelength multiplexing and tuning capabilities are highly important for applications in optical interconnects and optical communications using wavelength division multiplexing (WDM). In this paper, we describe novel methods and experimental results to achieve these functions in vertical cavity surface emitting lasers for the first time. We achieved a 2-dimensional surface emitting laser array emitting 140 unique, nonredundant, unformly separated,

  11. Routing and wavelength assignment in all-optical networks

    Microsoft Academic Search

    Rajiv Ramaswami; Kumar N. Sivarajan

    1995-01-01

    This paper considers the problem of routing connections in a reconfigurable optical networkusing wavelength division multiplexing, where each connection between a pair of nodes inthe network is assigned a path through the network and a wavelength on that path, suchthat connections whose paths share a common link in the network are assigned differentwavelengths.We derive an upper bound on the carried

  12. Dispersion, aberration and deconvolution in multi-wavelength fluorescence images

    Microsoft Academic Search

    B. A. SCALETTAR; J. R. SWEDLOW; J. W. SEDAT; D. A. AGARD

    1996-01-01

    Summary The wavelength dependence of the incoherent point spread function in a wide-field microscope was investigated experimentally. Dispersion in the sample and optics can lead to significant changes in the point spread function as wavelength is varied over the range commonly used in fluorescence microscopy. For a given sample, optical con- ditions can generally be optimized to produce a point

  13. Planarian Phototactic Assay Reveals Differential Behavioral Responses Based on Wavelength

    PubMed Central

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

    2014-01-01

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

  14. Hybrid all-optical networks: Routing and wavelength assignment

    Microsoft Academic Search

    Shivashis Saha; Chandra Has Nelapatla; Jitender S. Deogun

    2010-01-01

    next­ generation applications like cloud and grid computing. In this paper, we propose an ILP formulation and a heuristic based on genetic algorithm for routing and wavelength assignment prob­ lem in hybrid all-optical networks. The proposed model aims to minimize wavelength contentions by minimizing the overlapping paths in the hybrid networks. Experimental simulations show that the heuristic effectively minimizes the

  15. Two-wavelength laser interferometry using superheterodyne detection

    Microsoft Academic Search

    R. Daendliker; R. Thalmann; D. Prongue

    1988-01-01

    In two-wavelength interferometry, synthetic wavelengths are generated in order to reduce the sensitivity or to extend the range of unambiguity for interferometric measurements. Here a novel optoelectronic technique, called superheterodyne detection, is presented, which permits measurement of the phase difference of two optical frequencies that cannot be resolved by direct optoelectronic heterodyne detection. This technique offers the possibility for operation

  16. A four channel 10-nanometer spacing wavelength demultiplexer

    NASA Technical Reports Server (NTRS)

    Hendricks, H. D.

    1983-01-01

    Results on the development of an experimental four-channel fiber optics Wavelength Division Multiplexing (WDM) system with 10-nanometer channel spacing are presented. Data on WDM demultiplexers utilizing narrow band interference filters are reviewed. Results on studies of wavelength stability of semiconductor lasers for WDM are also presented.

  17. Lethal effects of short-wavelength visible light on insects

    PubMed Central

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

    2014-01-01

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

  18. Short-wavelength Yb:fiber laser analysis

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  19. Polarization-independent optical wavelength filter for channel dropping applications

    DOEpatents

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

    1996-01-01

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

  20. Polarization-independent optical wavelength filter for channel dropping applications

    DOEpatents

    Deri, R.J.; Patterson, F.

    1996-05-07

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

  1. A Study of Wavelength Calibration of NEWSIPS High-Dispersion Spectra

    E-print Network

    Myron A. Smith

    2001-04-03

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

  2. Wavelength tunable and amplitude-equilibrium dual-wavelength lasing sources with dual-pass Raman/Brillouin amplification configuration.

    PubMed

    Liu, Yan-ge; Wang, Dongning

    2008-03-17

    A simple technique for achieving wavelength tunable and amplitude-equilibrium dual-wavelength fiber laser source based on a dual-pass Raman/Brillouin amplification configuration is proposed and experimentally investigated. A stable room-temperature dual-wavelength lasing oscillations with average channel power of more than 1 mW and signal-to-noise ratio of more than 30 dB were obtained with only 250 mW Raman pump power. The dual-wavelength lasing oscillations with wavelength spacing of 0.076 nm were so stable that the maximum power fluctuations and wavelength shifts over more than 10 minutes of observation were less than 0.5 dB and 0.002 nm, respectively. The dual-wavelength lasing output can also be tuned in a range of ~35 nm from 1545.090 nm to 1580.078 nm with an amplitude-equilibrium of less than a peak power difference of 0.25 dB at the two wavelengths. PMID:18542451

  3. Astrochemistry at Millimetre and Submillimetre Wavelengths

    NASA Astrophysics Data System (ADS)

    Wirström, Eva, S.

    2009-12-01

    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 CO emission from the Orion nebula demonstrate that the water probably is localised to the photon-dominated region at the surface of the molecular cloud, at higher abundances than previously thought. Water is also observed in absorption from its ground-state towards the massive star-forming region Sgr B2. Curiously enough, a water abundance similar to the one reported for Orion is found in the low-excitation gas in one of the Galactic spiral arms. Ammonia absorption was also observed from diffuse spiral arm clouds along the same line-of-sight, but at about an order of magnitude lower abundance. The observed water and ammonia absorptions caused by the Sgr B2 cloud itself are successfully modelled without invoking a morphological component of hot gas. Two independent methods of analysis are applied to observations of methanol (CH3OH) and its 13C isotopologue in the cold envelopes of young stellar objects. Both methods indicate that methanol is mainly formed by hydrogenation of CO on cold dust grains. A study comparing the interstellar abundances of CH3SH (methyl mercaptan) and CH3OH unveil a possible trend of lower relative CH3SH abundances in more evolved objects. However, the significance of this trend, in relation to the chemical origin of these molecules, needs to be further investigated. In addition, searches for two pre-biotic molecules, namely vinyl acetylene (C2H3CCH) and amino acetonitrile (H2NCH2CN), resulting in improved upper abundance limits are presented. A comprehensive conclusion of this thesis is that in order to exploit the full capacity of high-quality observations there is a serious need for ! additional theoretical and laboratory investigations of processes like proton-exchange reactions, collision rates, freeze-out and desorption, all taking into account different isotopologues and spin-types.

  4. Multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain

    NASA Astrophysics Data System (ADS)

    Luo, Yiyang; Xia, Li; Sun, Qizhen; Li, Wei; Ran, Yanli; Liu, Deming

    2015-03-01

    In this paper, a multi-wavelength fiber laser based on self-seed light amplification and wavelength-dependent gain is proposed and demonstrated. A pumped erbium-doped fiber (EDF) in the linear cavity acts as the seed light source, which is also conducive to the gain equalization. A high power erbium-doped fiber amplifier (EDFA) is deployed for self-seed amplification, and a highly nonlinear fiber (HNLF) is incorporated in the ring cavity to alleviate the mode competition induced by the homogeneous gain broadening of EDF. In the experiments, 25-wavelength operation within 0.5 dB uniformity is achieved with the extinction ratio of ~42 dB using 500 m HNLF, and 38-wavelength operation within 3 dB uniformity is obtained with the extinction ratio of ~35 dB using 1000 m HNLF. Our proposed laser has more lasing wavelengths with a better uniformity and stability.

  5. Wavelength-Agile External-Cavity Diode Laser for DWDM

    NASA Technical Reports Server (NTRS)

    Pilgrim, Jeffrey S.; Bomse, David S.

    2006-01-01

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

  6. Laser-light-absorption studies at 1. 06. mu. m, 0. 53. mu. m, and 0. 35. mu. m wavelengths

    SciTech Connect

    Ze, F.; Campbell, E.M.; Turner, R.E.

    1981-10-01

    Results are presented of light absorption in a series of wavelength scaling experiments recently completed at LLNL. The Argus facility was used to do target studies at 1.06..mu..m, 0.53..mu..m and 0.35..mu..m. Box calorimeter scattered light measurements implied greatly improved laser light absorption for both high Z and low Z plasmas at laser wavelengths shorter than 1.06..mu..m. Furthermore, at the 0.35..mu..m laser wavelength, the inferred absorption is nearly 100% over a substantial range of incident laser intensities. Our results further show a dramatic decrease in the stimulated Brillouin scattered light at 0.35..mu..m relative to the values at 1.06..mu..m and 0.53..mu..m.

  7. Study on effect of optical wavelength on photo induced strain sensitivity in carbon nanotubes using fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Shivananju, B. N.; Asokan, S.; Misra, Abha

    2015-06-01

    In this work, the role of optical wavelength on the photo induced strain in carbon nanotubes (CNT) is probed using a Fiber Bragg Grating (FBG), upon exposure to infrared (IR) (21????mW?1) and visible (9????mW?1) radiations. The strain sensitivity in CNT is monitored over a smaller range (10?3 to 10?9 ?) by exposing to a low optical power varying in the range 10?3 to 10?6 W. In addition, the wavelength dependent response and recovery periods of CNT under IR (?rise = 150?ms, ?fall = 280?ms) and visible (?rise = 1.07?s, ?fall = 1.18?s) radiations are evaluated in detail. This study can be further extended to measure the sensitivity of nano–scale photo induced strains in nano materials and opens avenues to control mechanical actuation using various optical wavelengths.

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

    SciTech Connect

    Kaluza, M. C. [Blackett Laboratory, Imperial College London, London SW7 2BZ (United Kingdom); Institut fuer Optik und Quantenelektronik, Friedrich-Schiller-Universitaet, Max-Wien-Platz 1, 07743 Jena (Germany); Helmholtz-Institut Jena, Helmholtzweg 4, 07743 Jena (Germany); Mangles, S. P. D.; Najmudin, Z.; Dangor, A. E. [Blackett Laboratory, Imperial College London, London SW7 2BZ (United Kingdom); Thomas, A. G. R.; Krushelnick, K. [Blackett Laboratory, Imperial College London, London SW7 2BZ (United Kingdom); Center for Ultrafast Optical Science (CUOS), University of Michigan, Ann Arbor, Michigan 48109 (United States); Murphy, C. D. [Blackett Laboratory, Imperial College London, London SW7 2BZ (United Kingdom); Central Laser Facility, Rutherford Appleton Laboratory, Oxon OX11 0QX (United Kingdom); Clarendon Laboratory, University of Oxford, Oxford OX1 3PU (United Kingdom); Collier, J. L.; Divall, E. J.; Foster, P. S.; Hooker, C. J.; Langley, A. J.; Smith, J. [Central Laser Facility, Rutherford Appleton Laboratory, Oxon OX11 0QX (United Kingdom)

    2010-08-27

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

  9. Quantum dots based broad spectral photodetectors with wavelength detecting ability

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Wang, Yunpeng; Zhao, Dongxu; Zhao, Bin; Wang, Dengkui

    2015-06-01

    Board spectral photodetectors are required for varied scientific and industrial applications, yet the studies of such devices are limited. In this work a CdSe/ZnS quantum dots (QDs) based photodetector with broad spectral detecting ability was fabricated through a simple approach. Due to the discrete electronic states of QDs, the photodetector was more sensitive to incident wavelengths than incident power densities, and the photocurrent decreased monotonously with increasing incident wavelength, which could also realize the wavelength detection of incident light. This character provides a new way to achieve color or image sensing, and it could also broaden the photodetection and photosensing applications of QDs and semiconductor detectors.

  10. A three wavelength infrared focal plane array detector element

    Microsoft Academic Search

    Dong-Su Kim; Stephen R. Forrest; Michael J. Lange; Gregory H. Olsen; Marshall J. Cohen

    1994-01-01

    We have demonstrated a novel three wavelength InGaAs focal plane array pixel element for detection at wavelengths from 0.9-2.6 ?m, where each of three wavelength sensitive detectors are individually addressable. This device consists of successively smaller bandgap layers of InxGa1-xAs (x⩾0.53), separated by compositionally graded layers of InAsyP1-y to decrease defects induced by lattice mismatch strain with the InP substrate.

  11. Terahertz phase microscopy in the sub-wavelength regime

    NASA Astrophysics Data System (ADS)

    Yi, Minwoo; Lee, Kanghee; Song, Jin-Dong; Ahn, Jaewook

    2012-04-01

    Gouy phase shift is a well-known behavior that occurs when a propagating light is focused, but its behavior in the sub-wavelength confinement is not yet known. Here, we report the theoretical and experimental study of the aperture-size dependency of the Gouy phase shift in the sub-wavelength diffraction regime. In experiments carried out with laser-induced terahertz (THz) wave emission from various semiconductor apertures, we demonstrate the use of Guoy phase shit for sub-wavelength THz microscopy.

  12. Optical amplification at the 1.31 wavelength

    DOEpatents

    Cockroft, Nigel J. (Los Alamos, NM)

    1994-01-01

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

  13. Laser Transmission Welding of White Thermoplastics with Adapted Wavelengths

    NASA Astrophysics Data System (ADS)

    Mamuschkin, V.; Roesner, A.; Aden, M.

    Different types of laser sources can be used for polymer welding. By the principle of laser transmission welding the wavelength of the laser is one of the most important criteria when selecting a laser source as the optical properties of the polymers are depending on the wavelength. Up to date white material cannot be welded to each other. The results show that by analysis of the optical properties, especially the absorption and the scattering coefficient and adaption of the laser wavelength the process limits can be extended.

  14. Effect of graphene on plasmonic metasurfaces at infrared wavelengths

    SciTech Connect

    Ogawa, Shinpei, E-mail: Ogawa.Shimpei@eb.MitsubishiElectric.co.jp; Fujisawa, Daisuke; Ueno, Masashi [Advanced Technology R and D Center, Mitsubishi Electric Corporation, 8-1-1 Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661 (Japan)] [Advanced Technology R and D Center, Mitsubishi Electric Corporation, 8-1-1 Tsukaguchi-Honmachi, Amagasaki, Hyogo 661-8661 (Japan)

    2013-11-15

    Significant enhancement of infrared transmittance by the presence of a graphene layer on a plasmonic metasurface (PLM) has been demonstrated. PLMs with different configurations were fabricated, and their transmittance with and without graphene was compared. Selective enhancement by graphene occurred at the plasmon resonance wavelength. The degree of enhancement was found to depend on the width of the gap between the periodic metal regions in the PLM. A maximum enhancement of ?210% was achieved at a wavelength of 10 ?m. The ability to achieve such a drastic increase in transmittance at the plasmon resonant wavelength is expected to lead to improvements in the performance of energy collecting devices and optical sensors.

  15. Wavelength routing beyond the standard graph coloring approach

    NASA Astrophysics Data System (ADS)

    Blankenhorn, Thomas

    2004-04-01

    When lightpaths are routed in the planning stage of transparent optical networks, the textbook approach is to use algorithms that try to minimize the overall number of wavelengths used in the . We demonstrate that this method cannot be expected to minimize actual costs when the marginal cost of instlling more wavelengths is a declining function of the number of wavelengths already installed, as is frequently the case. We further demonstrate how cost optimization can theoretically be improved with algorithms based on Prim"s algorithm. Finally, we test this theory with simulaion on a series of actual network topologies, which confirm the theoretical analysis.

  16. Active Wavelength Control of an External Cavity Quantum Cascade Laser

    PubMed Central

    Tsai, Tracy; Wysocki, Gerard

    2012-01-01

    We present an active wavelength control system for grating-based external cavity lasers that increases the accuracy of predicting the lasing wavelength based on the grating equation and significantly improves scan-to-scan wavelength/frequency repeatability. The ultimate 3? precision of a frequency scan is determined by the scan-to-scan repeatability of 0.042 cm?1. Since this control method can be applied to any external cavity laser with little to no modification, such a precision provides an excellent opportunity for spectroscopic applications that target molecular absorption lines at standard atmospheric conditions. PMID:23483850

  17. Fiber optics for the future - wavelength division multiplexing

    NASA Technical Reports Server (NTRS)

    Spencer, J. L.

    1982-01-01

    Optical wavelength division multiplexing (WDM) systems, with signals transmitted on different wavelengths through a single fiber, can have increased information capacity and fault isolation properties over single wavelength optical systems. This paper describes a typical WDM system. The applicability of future standards to such a system are discussed. Also, a state-of-the-art survey of optical multimode components which could be used to implement the system are made. The components to be surveyed are sources, multiplexers, and detectors. Emphasis is given to the demultiplexer techniques which are the major developmental components in the WDM system.

  18. DPAL: A New Class of Lasers for CW Power Beaming at Ideal Photovoltaic Cell Wavelengths

    SciTech Connect

    Krupke, W F; Beach, R J; Payne, S A; Kanz, V K; Early, J T

    2003-09-15

    The new class of diode pumped alkali vapor lasers (DPALs) offers high efficiency cw laser beams at wavelengths which efficiently couple to photovoltaic (PV) cells: silicon cells at 895 nm (cesium), and GaAs cells at 795 nm (rubidium) and at 770 nm (potassium). DPAL electrical efficiencies of 25-30% are projected, enabling PV cell efficiencies {approx}40% (Si) and {approx}60% (GaAs). Near-diffraction-limited DPAL device power scaling into the multi-kilowatt regime from a single aperture is projected.

  19. Observations of the brightness temperature distribution of the quiet solar corona at decametric wavelengths

    NASA Technical Reports Server (NTRS)

    Sastry, Ch. V.

    1987-01-01

    The brightness temperature distribution of the quiet solar corona at a wavelength of 8.9 meters is measured by two types of radio telescope: (1) a 'T' type array with a resolution of 26'X38', and (2) a fan beam interferometer with an E-W resolution of 3'. It is found that the persistent bright regions do not have any angular structure on scales of 6' or less. The daily variations of the brightness temperature of different regions are studied and the possible interpretation discussed.

  20. Enhanced wavelength conversion and photon pair generation using slow light effects and electronic carrier sweepout in silicon photonics devices

    NASA Astrophysics Data System (ADS)

    Savanier, Marc; Kumar, Ranjeet; Mookherjea, Shayan

    2015-03-01

    Silicon photonics has drawn a lot of attention over the last decades, mainly in telecom-related application fields where the nonlinear optical properties of silicon are ignored or minimized. However, silicon's high ?(3) Kerr optical nonlinearity in sub-micron-scale high-confinement waveguides can enable significant improvements in traditional nonlinear devices, such as for wavelength conversion, and also enable some device applications in quantum optics or for quantum key distribution. In order to establish the viability of silicon photonics in practical applications, some big challenges are to improve the optical performance (e.g., optimize nonlinearity or minimize loss) and integration of optics with microelectronics. In this context, we discuss how electronic PIN diodes improve the performance of wavelength conversion in a microring resonator based four-wave mixing device, which achieves a continuous-wave four-wave mixing conversion efficiency of -21.3 dB at 100 mW pump power, with enough bandwidth for the wavelength conversion of a 10 Gbps signal. In the regime of quantum optics, we describe a coupled microring device that can serve as a tunable source of entangled photon pairs at telecommunications wavelengths, operating at room temperature with a low pump power requirement. By controlling either the optical pump wavelength, or the chip temperature, we show that the output bi-photon spectrum can be varied, with implications on the degree of frequency correlation of the generated quantum state.

  1. Optimizations of preprocessing and wavelength selection in predicting human total hemoglobin concentrations based on VIS/NIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yoon, Gilwon; Kim, Seonwoo; Kim, Yoen-Joo; Kim, Jongwon; Kim, Won Ky

    1998-04-01

    The importance and effects of data preprocessing and wavelength selection were investigated in predicting total hemoglobin concentrations form absorption spectra. Spectra of the 1 nm interval between 500-900nm were measured from the whole blood samples taken form 165 patients whose hemoglobin concentrations ranged between 7-17 g/dl. The concentrations were predicted using the partial least squares regression. A total of 18 different combinations of preprocessing were tested. The partial least squares regression analysis provided quite different results depending on preprocessing methods and a wide range of prediction accuracy was obtained. For example, the sum of squares of difference ranged from 6-18.6, R2 varied from 0.8333 to 0.9477 and the root mean squared errors were from 0.5504-0.966 g/dl. The best results was obtained from the data processed by linear regression baseline fitting, unit area correction, mean centering and variance scaling. Instead of using all wavelengths in the broad-band spectra, a discrete number of wavelengths were selected to predict the concentrations using our algorithm, which will be advantageous in developing compact and less expensive commercial devices. It proves that a careful selection of wavelengths can provide a comparable accuracy obtained from using the broad-band spectra. For our particular experimental data, the measurement form only three discrete wavelengths could provide excellent results.

  2. The Wavelength Dependence of High-Redshift Galaxy Structure in the Rest-Frame Ultraviolet

    E-print Network

    Bond, Nicholas A; de Mello, Duilia F; Teplitz, Harry I; Rafelski, Marc; Koekemoer, Anton M; Coe, Dan; Grogin, Norman; Gawiser, Eric; Ravindranath, Swara; Scarlata, Claudia

    2014-01-01

    We present the rest-frame UV wavelength dependence of the Petrosian-like half-light radius ($r_{50}$), and the concentration parameter for a sample of 198 star-forming galaxies at 0.5 < z < 1.5. We find a ~5% decrease in $r_{50}$ from 1500 \\AA\\ to 3000 \\AA, with half-light radii at 3000 \\AA\\ ranging from 0.6 kpc to 6 kpc. We also find a decrease in concentration of ~0.07 (1.9 < $C_{3000}$ < 3.9). The lack of a strong relationship between $r_{50}$ and wavelength is consistent with a model in which clumpy star formation is distributed over length scales comparable to the galaxy's rest-frame optical light. While the wavelength dependence of $r_{50}$ is independent of size at all redshifts, concentration decreases more sharply in the far-UV (~1500 \\AA) for large galaxies at z ~ 1. This decrease in concentration is caused by a flattening of the inner ~20% of the light profile in disk-like galaxies, indicating that the central regions have different UV colors than the rest of the galaxy. We interpret th...

  3. Visible-wavelength polarized-light emission with small-diameter InN nanowires.

    PubMed

    Bayerl, Dylan; Kioupakis, Emmanouil

    2014-07-01

    Group III nitrides are widely used in commercial visible-wavelength optoelectronic devices, but materials issues such as dislocations, composition fluctuations, and strain negatively impact their efficiency. Nitride nanostructures are a promising solution to overcome these issues and to improve device performance. We used first-principles calculations based on many-body perturbation theory to study the electronic and optical properties of small-diameter InN nanowires. We show that quantum confinement in 1 nm wide InN nanowires shifts optical emission to the visible range at green/cyan wavelengths and inverts the order of the top valence bands, leading to linearly polarized visible-light emission. Quantum confinement on this scale also leads to large exciton binding energies of 1.4 eV and electronic band gaps in excess of 3.7 eV. Our results indicate that strong quantum confinement in InN nanostructures is a promising approach to developing efficient visible-wavelength light emitters. PMID:24527880

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

    SciTech Connect

    Ferhanoglu, Onur; Urey, Hakan

    2011-07-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  6. Large-Aperture Wide-Bandwidth Anti-Reflection-Coated Silicon Lenses for Millimeter Wavelengths

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  7. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and wavelength bands. (a) The radio spectrum shall be...

  8. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and wavelength bands. (a) The radio spectrum shall be...

  9. 47 CFR 2.101 - Frequency and wavelength bands.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS; GENERAL RULES...Allocation, Assignment, and Use of Radio Frequencies § 2.101 Frequency and wavelength bands. (a) The radio spectrum shall be...

  10. Wavelength division multiplexing. [in fiber optics communication systems

    NASA Technical Reports Server (NTRS)

    Hendricks, H. D.

    1985-01-01

    Wavelength division multiplexing (WDM) represents an approach for expanding the communication capacity and for implementing special data techniques in a fiber optics system. This technology is implemented by adding optical sources of different wavelengths at optical transmitting locations. The present paper is concerned with some of the current efforts in WDM. WDM applications are related to long haul communications, local area data networks, spacecraft and aircraft data systems, fault tolerant computer networks, special sensor devices, high speed data processors, closed circuit and cable television, and submarine cable systems. Attention is given to the current state of wavelength division multiplexing applications, the availability and status of WDM components semiconductor lasers/transmitters, availability and status of fiber optic detectors/receivers, optical fibers/cables/connectors/taps/star couplers, wavelength multiplexers/demultiplexers, and future WDM for local area networks.

  11. Wavelength division multiplexing WDM, CWDM and DWDM applications

    NASA Astrophysics Data System (ADS)

    Vasile, Irina Bristena; Vasile, Alexandru; Luciana, Stan; Tache, Mihaela

    2007-05-01

    The fiber optics has become the most preferred media for this very large data traffic. TDM (Time Division Multiplexing) has been the most practical method to divide the significant capacity of a single fiber optics into several communication channels. This technology is still limited by the large complexity of high-flow modulation and multiplexing equipment. Presently, a complementary approach proves its potential: Wavelength-Division Multiplexing (WDM). The evolution of WDM allows now a very small spacing between channels wavelength, in nm, generating DWDM (Dense Wavelength Division Multiplexing). The networks with individual fibers including more than 100 independent optic channels, as well as those with bidirectional flow are already available on the market. CWDM (Coarse Wavelength Division Multiplexing) represents an economical application of a mature technology which may provide options where the capacity of fibers is limited.

  12. Ferroelectric bolometer measures RF absolute power at submillimeter wavelengths

    NASA Technical Reports Server (NTRS)

    Cohn, M.; Rodgers, J. D.

    1966-01-01

    Two ferroelectric bolometer sensing elements measure low rf absolute power at millimeter and submillimeter wavelengths. The sensing elements are mounted in sections of waveguide and connected in series in a standard temperature compensating bridge circuit.

  13. Short wavelength fluctuations and electron transport in TFTR

    NASA Astrophysics Data System (ADS)

    Wong, K. L.; Itoh, K.; Itoh, S.-I.; Fukuyama, A.; Yagi, M.

    2000-11-01

    Correlation between electron heat diffusivity and short wavelength ( k?i˜5) fluctuation amplitude was observed in the TFTR tokamak in the core of ERS plasmas (Phys. Lett. A 236 (1997) 339). These fluctuations propagate in the ion diamagnetic drift direction with wave number comparable to ?pe/ c. Further analysis of these data yields the ratios ?e/ ?i and ?e/ De, and their values are consistent with the picture that the electron transport is mainly induced by the short wavelength fluctuations in the plasma core where the long wavelength ( k?i˜1) fluctuations are absent. Although there is not enough information to identify these short wavelength modes, the values of ?e is found to be comparable to theoretical predictions based on the current diffusive ballooning mode theory (Plasma Phys. Control. Fusion 36 (1994) 279).

  14. Wavelength Assignment in WDM Rings to Minimize SONET ADMs

    E-print Network

    Ophir Frieder Abstract-- We study wavelength assignment for lightpaths over WDM rings to minimize Email: ophir@cs.iit.edu, Computer Science Department,Illinois Institute of Technology, Chicago, IL 60616

  15. Wavelength-Multiplexed Entanglement Distribution over 10 km of Fiber

    E-print Network

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

    2008-10-02

    We report the first experimental demonstration of wavelength-multiplexed entanglement distribution. 44 channels of highly-entangled photon-pairs from one single broadband source are distributed over 10 km of fiber.

  16. Optical modulation of quantum cascade laser with optimized excitation wavelength.

    PubMed

    Yang, Tao; Chen, Gang; Tian, Chao; Martini, Rainer

    2013-04-15

    The excitation wavelength for all-optical modulation of a 10.6 ?m mid-infrared (MIR) quantum cascade laser (QCL) was varied in order to obtain maximum modulation depth. Both amplitude and wavelength modulation experiments were conducted at 820 nm and 1550 nm excitation respectively, whereby the latter matches the interband transition in the QCL active region. Experimental results show that for continuous-wave mode-operated QCL, the efficiency of free carrier generation is doubled under 1550 nm excitation compared with 820 nm excitation, resulting in an increase of the amplitude modulation index from 19% to 36%. At the same time, the maximum wavelength shift is more than doubled from 1.05 nm to 2.80 nm. Furthermore, for the first time to our knowledge, we demonstrated the optical switching of a QCL operated in pulse mode by simple variation of the excitation wavelength. PMID:23595430

  17. Fast fiber-optic multi-wavelength pyrometer

    Microsoft Academic Search

    Tairan Fu; Peng Tan; Chuanhe Pang; Huan Zhao; Yi Shen

    2011-01-01

    A fast fiber-optic multi-wavelength pyrometer was developed for the ultraviolet-visible-near infrared spectra from 200 nm to 1700 nm using a CCD detector and an InGaAs detector. The pyrometer system conveniently and quickly provides the sufficient choices of multiple measurement wavelengths using optical diffraction, which avoids the use of narrow-band filters. Flexible optical fibers are used to transmit the radiation so

  18. Laser-Matter Interactions at SubMicron Laser Wavelengths

    Microsoft Academic Search

    Daniel Pasini

    1984-01-01

    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

  19. Wavelengths of spectral lines in mercury pencil lamps.

    PubMed

    Sansonetti, C J; Salit, M L; Reader, J

    1996-01-01

    The wavelengths of 19 spectral lines in the region 253-579 nm emitted by Hg pencil-type lamps were measured by Fourier-transform spectroscopy. Precise calibration of the spectra was obtained with wavelengths of (198)Hg as external standards. Our recommended values should be useful aswavelength-calibration standards for moderate-resolution spectrometers at an uncertainty level of 0.0001 nm. PMID:21068979

  20. Laser Wavelength Choices for Pico-Projector Applications

    Microsoft Academic Search

    Edward Buckley

    2011-01-01

    The rapid progress in laser light source development, particularly in the gallium-nitride material system, means that a wide range of wavelengths are now available for pico-projection applications intended to deliver 20 lm or less. In principle, this affords designers of pico-projection systems great flexibility in choosing laser wavelengths to optimize specific performance metrics. With the proliferation of laser-based pico-projectors, however,

  1. Pump wavelength-dependent spectral-hole burning in EDFAs

    Microsoft Academic Search

    Michael J. Yadlowsky

    1999-01-01

    Gain-difference spectra are used to show that 980-nm band pump wavelength changes can significantly effect spectral-hole burning (SHB) in erbium-doped fiber amplifiers (EDFAs). Gain measurements made using a number of different signal and pump wavelengths help to characterize the underlying inhomogeneous spectral properties of EDFAs and a framework for modeling these effects is presented. Despite the difficulty of obtaining the

  2. Tunable sampled-grating DBR lasers with integrated wavelength monitors

    Microsoft Academic Search

    Beck Mason; Steven P. DenBaars; Larry A. Coldren

    1998-01-01

    We report on the design and development of a wavelength monitor for use with tunable semiconductor lasers. The device is based on two-mode interference in an asymmetrically excited waveguide that is coupled to a Y-branch splitter. The monitoring range of the device is 30 nm. The wavelength monitor is capable of operating over an input power range of 34 dB,

  3. Deformation and shape measurement using multiple wavelength microscopic TV holography

    Microsoft Academic Search

    U. Paul Kumar

    2009-01-01

    Characterization of deformation and surface shape is an important parameter in quality testing of micro-objects in view of the functionality, reliability, and integrity of the components. Single-wavelength TV holography is widely used for deformation analysis. However, the single-wavelength TV holographic configuration suffers from overcrowding of fringes for large deformation that sets a limitation due to speckle decorrelation for quantitative fringe

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  5. Four-wave mixing wavelength conversion efficiency in semiconductor traveling-wave amplifiers measured to 65 nm of wavelength shift

    Microsoft Academic Search

    Jianhui Zhou; K. J. Vahala; M. A. Newkirk; B. I. Miller

    1994-01-01

    The efficiency of broadband optical wavelength conversion by four-wave mixing in semiconductor traveling-wave amplifiers is measured for wavelength shifts up to 65 nm using a tandem amplifier geometry. A quantity we call the relative conversion efficiency function, which determines the strength of the four-wave mixing nonlinearity, was extracted from the data. Using this quantity, gain requirements for lossless four-wave mixing

  6. 1024 × 1024 pixel mid-wavelength and long-wavelength infrared QWIP focal plane arrays for imaging applications

    Microsoft Academic Search

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

    2005-01-01

    Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024 × 1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE?T) of 17 mK at a 95 K operating temperature with f\\/2.5 optics at 300 K background and the LWIR detector array has

  7. Large-Scale Photonic Integrated Circuits

    Microsoft Academic Search

    R. Nagarajan; M. Kato; J. Pleumeekers; P. Evans; S. Hurtt; A. Dentai; M. Missey; A. Chen; A. Mathur; D. Lambert; P. Chavarkar; J. Back; R. Muthiah; S. Murthy; R. Salvatore; C. Joyner; J. Rossi; R. Schneider; M. Ziari; F. Kish; D. Welch

    2007-01-01

    We review our work in the area of large scale InP photonic integrated circuits (PIC). We will review dense wavelength division multiplexed (DWDM) transmitter and receiver PICs with up to 40 channels, and operating at data rates up to 40 Gbit\\/s.

  8. Drift wave transport scalings introduced by varying correlation length

    SciTech Connect

    Weiland, J.; Holod, I. [Department of Electromagnetics, Chalmers University of Technology and EURATOM-VR Association, 41296 Goeteborg (Sweden)

    2005-01-01

    Scalings of the correlation length of drift wave turbulence with magnetic current q, shear, elongation, and temperature ratio have been introduced into a drift wave transport model. The correlation length is calculated from linear scaling of the fastest growing mode. Such a procedure is supported by previous turbulence simulations with absorbing boundaries for short and long wavelengths. The resulting q and s scalings are now in better agreement with experimental scalings. In particular, the simulation results for transport barrier shots improve.

  9. Multi-wavelength fiber source with equal frequency spacing

    NASA Astrophysics Data System (ADS)

    Zhang, X. L.; Zhou, K. J.; Ngo, N. Q.; Tan, T. H.; Poon, W. C.

    2010-07-01

    A optical filter based on Sagnac interferometer was proposed to be acted as a comb filter with equal frequency spacing and good signal to noise ratio (SNR), which was composed of an 8.14 m stress-induced Hi-Bi (high-birefringence) PM (polarization-maintaining) fiber. Using this multi-wavelength Sagnac comb filter and a gain flattening Sagnac filter that made the output spectra flattening at different pump powers, a 25-channel multi-wavelength all-fiber source were successfully generated with channel spacing of 0.8 nm with respect to the center wavelength at 1550 nm and flattened gain about ±1 dB peak deviation. The channel spacing can be further reduced to 0.4 nm to produce a DWDM (dense wavelength division multiplexing) source, simply by increasing the Hi-Bi fiber to be 16.28 m. It can be used in many applications such as WDM (wavelength division multiplexing), optical amplifiers with a high SNR, narrow band filters and optical sensors.

  10. Magic wavelengths for optical cooling and trapping of lithium

    E-print Network

    Safronova, M S; Clark, Charles W

    2012-01-01

    Using first-principles calculations, we identify magic wavelengths for the 2s-2p and 2s-3p transitions in lithium. The ns and np atomic levels have the same ac Stark shifts at the corresponding magic wavelength, which facilitates state-insensitive optical cooling and trapping. Tune-out wavelengths for which the ground-state frequency-dependent polarizability vanishes are also calculated. Differences of these wavelengths between 6Li and 7Li are reported. Our approach uses high-precision, relativistic all-order methods in which all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Recommended values are provided for a large number of Li electric-dipole matrix elements. Static polarizabilities for the 2s, 2p, 3s, 3p, and 3d levels are compared with other theory and experiment where available. Uncertainties of all recommended values are estimated. The magic wavelengths for the uv 2s-3p transition are of particular interest for the pr...

  11. Effect of wavelength on cutaneous pigment using pulsed irradiation

    SciTech Connect

    Sherwood, K.A.; Murray, S.; Kurban, A.K.; Tan, O.T.

    1989-05-01

    Several reports have been published over the last two decades describing the successful removal of benign cutaneous pigmented lesions such as lentigines, cafe au lait macules' nevi, nevus of Ota, and lentigo maligna by a variety of lasers such as the excimer (351 nm), argon (488,514 nm), ruby (694 nm), Nd:YAG (1060 nm), and CO/sub 2/ (10,600 nm). Laser treatment has been applied to lesions with a range of pigment depths from superficial lentigines in the epidermis to the nevus of Ota in the reticular dermis. Widely divergent laser parameters of wavelength, pulse duration, energy density, and spotsizes have been used, but the laser parameters used to treat this range of lesions have been arbitrary, with little effort focused on defining optimal laser parameters for removal of each type. In this study, miniature black pig skin was exposed to five wavelengths (504, 590, 694, 720, and 750 nm) covering the absorption spectrum of melanin. At each wavelength, a range of energy densities was examined. Skin biopsies taken from laser-exposed sites were examined histologically in an attempt to establish whether optimal laser parameters exist for destroying pigment cells in skin. Of the five wavelengths examined, 504 nm produced the most pigment specific injury; this specificity being maintained even at the highest energy density of 7.0 J/cm2. Thus, for the destruction of melanin-containing cells in the epidermal compartment, 504 nm wavelength appears optimal.

  12. Highly efficient entanglement swapping and teleportation at telecom wavelength.

    PubMed

    Jin, Rui-Bo; Takeoka, Masahiro; Takagi, Utako; Shimizu, Ryosuke; Sasaki, Masahide

    2015-01-01

    Entanglement swapping at telecom wavelengths is at the heart of quantum networking in optical fiber infrastructures. Although entanglement swapping has been demonstrated experimentally so far using various types of entangled photon sources both in near-infrared and telecom wavelength regions, the rate of swapping operation has been too low to be applied to practical quantum protocols, due to limited efficiency of entangled photon sources and photon detectors. Here we demonstrate drastic improvement of the efficiency at telecom wavelength by using two ultra-bright entangled photon sources and four highly efficient superconducting nanowire single photon detectors. We have attained a four-fold coincidence count rate of 108 counts per second, which is three orders higher than the previous experiments at telecom wavelengths. A raw (net) visibility in a Hong-Ou-Mandel interference between the two independent entangled sources was 73.3 ± 1.0% (85.1 ± 0.8%). We performed the teleportation and entanglement swapping, and obtained a fidelity of 76.3% in the swapping test. Our results on the coincidence count rates are comparable with the ones ever recorded in teleportation/swapping and multi-photon entanglement generation experiments at around 800 nm wavelengths. Our setup opens the way to practical implementation of device-independent quantum key distribution and its distance extension by the entanglement swapping as well as multi-photon entangled state generation in telecom band infrastructures with both space and fiber links. PMID:25791212

  13. Highly efficient entanglement swapping and teleportation at telecom wavelength

    E-print Network

    Rui-Bo Jin; Masahiro Takeoka; Utako Takagi; Ryosuke Shimizu; Masahide Sasaki

    2014-10-01

    Entanglement swapping at telecom wavelengths is at the heart of quantum networking in optical fiber infrastructures. Although entanglement swapping has been demonstrated experimentally so far using various types of entangled photon sources both in near-infrared and telecom wavelength regions, the rate of swapping operation has been too low to be applied to practical quantum protocols, due to limited efficiency of entangled photon sources and photon detectors. Here we demonstrate drastic improvement of the efficiency at telecom wavelength by using two ultra-bright entangled photon sources and four highly efficient superconducting nanowire single photon detectors.We have attained a four-fold coincidence count rate of 108 counts per second, which is three orders higher than the previous experiments at telecom wavelengths. A raw (net) visibility in a Hong-Ou-Mandel interference between the two independent entangled sources was 73.3 $\\pm$ 1.0% (85.1 $\\pm$ 0.8%). We performed the teleportation and entanglement swapping, and obtained a fidelity of 76.3% in the swapping test.Our results on the coincidence count rates are comparable with the ones ever recorded in teleportation/swaping and multi-photon entanglement generation experiments at around 800\\,nm wavelengths. Our setup opens the way to practical implementation of device-independent quantum key distribution and its distance extension by the entanglement swapping as well as multi-photon entangled state generation in telecom band infrastructures with both space and fiber links.

  14. Recirculating photonic filter: A wavelength-selective true-time-delay device for optically controlled phased array sensors and wavelength code-division multiple access

    NASA Astrophysics Data System (ADS)

    Yegnanarayanan, Sivasubramaniam

    1999-10-01

    In this dissertation we propose a novel wavelength- selective photonic time-delay filter. This device consists of an optical phased-array waveguide grating in a recirculating feedback configuration: This all-optical tunable optical delay line device permits several novel applications in the optical processing of high frequency signals. The first application is as a true-time-delay generator for squint-free beam steering in optically-controlled microwave phased-array antennas where the optical carrier wavelength is used to select a desired time delay for the microwave signal. Time-delay beam steering ensure wide instantaneous bandwidth operation. The mapping of optical wavelength to the microwave beam direction permits a hardware compressive architecture for the optical control unit that can easily scale to large aperture antenna arrays. Prototype integrated optical chips consisting of optical filters and precision delay lines have demonstrated picosecond resolution time delays. Hybrid devices permit longer time-delays of several tens of nanoseconds through external fiber delay lines. Extension to optically controlled two-dimensional array beam steering using optical wavelength conversion between azimuth and elevation beam steering units is also explored. This overcomes optical/electrical/optical conversion losses in cascading individual beam steering units. A 2-element X-band optically controlled phased array transmitter is assembled in a compact test range to verify the wide bandwidth beam steering system. Such wavelength selective time delay filter devices can also transform optical pulses with wide spectral bandwidth into simultaneous wavelength and time coded waveforms. One application of such hybrid coded waveforms is in optical code-division multiple access (CDMA) communication. Their perfect delta-function autocorrelation and small cross-correlation properties result in significant improvements in the number of orthogonal codes and the number of simultaneous users compared to traditional incoherent CDMA. We demonstrate such hybrid encoding of picosecond pulses from a modelocked laser. The superior correlation properties of such encoded pulses have also been verified. Digital data transmission over a CDMA fiber link with matched filter decoding at the receiver is shown. Finally, we discuss the silicon-on-insulator (SOI) integrated optical technology for realizing passive and active devices such as discussed in this dissertation. This planar waveguide technology is attractive for the potential low cost silicon IC compatible fabrication and low waveguide losses above 1.2 ?m. This approach could transform the optical processing functions such as discussed here into real world application specific optical circuits. We present the design, fabrication and demonstration of filter devices in the silicon-on- insulator integrated optical waveguide technology wherein the filter can be actively controlled through free- carrier electro-optic tuning. Following the rapid progress in recent years in multiwavelength pulsed sources, optical filter components and high-speed high linearity photodetectors, optical processing devices such as discussed in this thesis could form the building block of systems performing complex signal processing functions such as sampling, synthesis and filtering of high-speed signals.

  15. Self-Q-switched Er–Yb double clad fiber laser with dual wavelength or tunable single wavelength operation by a Sagnac interferometer

    NASA Astrophysics Data System (ADS)

    Álvarez-Tamayo, R. I.; Durán-Sánchez, M.; Pottiez, O.; Ibarra-Escamilla, B.; Bello-Jiménez, M.; Kuzin, E. A.

    2015-07-01

    We report a self-Q-switched Erbium-Ytterbium-doped double cladding fiber ring laser with dual wavelength or tunable single wavelength operations. A Sagnac interferometer with a high birefringence fiber in the loop was used for the wavelength tuning of the single line operation and cavity loss adjustment for dual wavelength laser operation. Single wavelength laser operation for a pump power of 421?mW tunable in a range of 1561.4?nm to 1569.8?nm and dual wavelength laser operation at 1561.1?nm and 1571.4?nm with equal output powers are presented.

  16. Modelling of sub-wavelength THz sources as Gaussian apertures.

    PubMed

    Lin, Hungyen; Fumeaux, Christophe; Fischer, Bernd Michael; Abbott, Derek

    2010-08-16

    The THz emission point on a nonlinear electro-optical crystal for generating broadband THz radiation is modeled as a radiating Gaussian aperture. With the wavelengths of the infrared pump beam being much smaller than the wavelength components of the generated THz pulse, a THz sub-wavelength radiating aperture with Gaussian profile is effectively created. This paper comprehensively investigates Gaussian apertures in focused THz radiation generation in electro-optical crystals and illustrates the breakdown of the paraxial approximation at low THz frequencies. The findings show that the shape of the radiation pattern causes a reduction in detectable THz radiation and hence contributes significantly to low signal-to-noise ratio in THz radiation generation. Whilst we have demonstrated the findings on optical rectification in this paper, the model may apply without a loss of generality to other types of apertures sources in THz radiation generation. PMID:20721154

  17. Slot-grating flat lens for telecom wavelengths.

    PubMed

    Pugh, Jonathan R; Stokes, Jamie L; Lopez-Garcia, Martin; Gan, Choon-How; Nash, Geoff R; Rarity, John G; Cryan, Martin J

    2014-07-01

    We present a stand-alone beam-focusing flat lens for use in the telecommunications wavelength range. Light incident on the back surface of the lens propagates through a subwavelength aperture and is heavily diffracted on exit and partially couples into a surface plasmon polariton and a surface wave propagating along the surface of the lens. Interference between the diffracted wave and re-emission from a grating patterned on the surface produces a highly collimated beam. We show for the first time a geometry at which a lens of this type can be used at telecommunication wavelengths (?=1.55 ?m) and identify the light coupling and re-emission mechanisms involved. Measured beam profile results at varying incident wavelengths show excellent agreement with Lumerical FDTD simulation results. PMID:24978737

  18. The wavelength dependence of Martian atmospheric dust radiative properties

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.; Ockert-Bell, M. E.; Arvidson, R.; Shepard, M.

    1993-01-01

    One of the key radiative agents in the atmosphere of Mars is the suspended dust particles. A new analysis of two data sets of the Martian atmosphere is being carried out in order to better evaluate the radiative properties of the atmospheric dust particles. The properties of interest are the size distribution, optical constants, and other radiative properties, such as the single-scattering albedo and phase function. Of prime importance is the wavelength dependence of these radiative properties throughout the visible and near-infrared wavelengths. Understanding the wavelength dependence of absorption and scattering characteristics will provide a good definition of the influence that the atmospheric dust has on heating of the atmosphere.

  19. Freestanding GaN grating couplers at visible wavelengths

    NASA Astrophysics Data System (ADS)

    Liu, Qifa; Shi, Zheng; Zhu, Gangyi; Wang, Wei; Wang, Zhenhai; Wang, Yongjin

    2015-04-01

    A freestanding GaN grating coupler is proposed for planar photonic applications within the visible-wavelength spectrum. This freestanding device was produced by double-sided fabrication, combining GaN front patterning with Si substrate back releasing and GaN slab back thinning. Transverse-electric (TE) and transverse-magnetic (TM) light-wave conversion into and out of the membrane through grating coupling was determined by optical measurement. The maximum coupling efficiency is up to 69% for TE waves and 66% for TM waves at each particular wavelength according to the finite element method (FEM) simulation results. The experimental results were also supported by reflective simulation based on rigorous coupled-wave analysis (RCWA). This work opens the way for freestanding GaN planar photonic devices operating within the visible-wavelength range. It also provides the possibility of monolithic integration of planar photonic and light sources on III-nitride active platforms.

  20. Residual zonal flows in tokamaks and stellarators at arbitrary wavelengths

    E-print Network

    Monreal, P; Sánchez, E; Parra, F I; Bustos, A; Könies, A; Kleiber, R; Görler, T

    2015-01-01

    In the linear collisionless limit, a zonal potential perturbation in a toroidal plasma relaxes, in general, to a non-zero residual value. Expressions for the residual value in tokamak and stellarator geometries, and for arbitrary wavelengths, are derived. These expressions involve averages over the lowest order particle trajectories, that typically cannot be evaluated analytically. In this work, an efficient numerical method for the evaluation of such expressions is reported. It is shown that this method is faster than direct gyrokinetic simulations. Calculations of the residual value in stellarators are provided for much shorter wavelengths than previously available in the literature. Electrons must be treated kinetically in stellarators because, unlike in tokamaks, kinetic electrons modify the residual value even at long wavelengths. This effect, that had already been predicted theoretically, is confirmed by gyrokinetic simulations.

  1. Optimal excitation wavelengths for discrimination of nasopharyngeal carcinoma in vitro

    NASA Astrophysics Data System (ADS)

    Lin, Lisheng; Yang, Fuwen; Li, Buhong; Xie, Shusen

    2007-11-01

    Measurement of excitation-emission matrices (EEMs) for nasopharyngeal carcinoma (NPC) and normal nasopharyngeal tissues in vitro was employed to determine the optimal excitation wavelengths that contain the most diagnostic information for optical diagnosis. Pathologically confirmed normal nasopharyngeal and NPC tissues(n=47) were obtained from 25 patients undergoing surgical biopsy. The autofluorescence EEMs of tissue biopsies were recorded with a TCSPC spectrofluorimeter. Fluorescence excitation wavelengths varied from 260 to 500 nm, and the corresponding fluorescence emission spectra were recorded from a range starting 20 nm above the excitation wavelength and extending to 700 nm. The calibration for different EEMs measurements was performed for quantitative comparison. As a result, we find that the excitation-emission pair of 340-380 nm yields the best performance for discrimination of NPC tissues with the sensitivity and specificity of 77.2% and 88.0%, respectively

  2. Power and wavelength scaling using semiconductor disk laser-bismuth fiber MOPA systems

    NASA Astrophysics Data System (ADS)

    Heikkinen, Juuso; Gumenyuk, Regina; Rantamäki, Antti; Lyytikäinen, Jari; Leinonen, Tomi; Zolotovskii, Igor; Melkumov, Mikhail; Dianov, Evgeny M.; Okhotnikov, Oleg G.

    2015-03-01

    We present a master oscillator power amplifier (MOPA) system that comprises a mode-locked semiconductor disk laser (SDL) emitting at 1.33 ?m and a bismuth-doped fiber amplifier. The mode-locked SDL was fabricated by wafer bonding an InP-based gain section with a GaAs-based distributed Bragg reflector (DBR) using (3-Mercaptopropyl)-trimethoxysilane. The bismuth-doped fiber amplifier was pumped with a continuous wave SDL emitting at 1.18 ?m. The MOPA system produced pulses at a repetition rate of 827 MHz with a pulse energy of 0.62 nJ, which corresponds to an average output power of more than 0.5 W.

  3. Wavelength scaling of high-intensity illumination of an exploded foil

    Microsoft Academic Search

    J. A. Cobble; R. P. Johnson; R. J. Mason

    1998-01-01

    A preformed plasma simulating the corona of a fast ignitor target has been probed with 527 nm and 1054 nm lasers exceeding the critical power for ponderomotive electron cavitation. For both colors, the f number of the probe beam is increased as it propagates through the plasma. Transmission of the diffraction-limited beams is higher for the green than for the

  4. Wavelength scaling of high-intensity illumination of an exploded foil

    SciTech Connect

    Cobble, J.A.; Johnson, R.P.; Mason, R.J. [Los Alamos National Laboratory, P-24, E526, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, P-24, E526, Los Alamos, New Mexico 87545 (United States)

    1998-11-01

    A preformed plasma simulating the corona of a fast ignitor target has been probed with 527 nm and 1054 nm lasers exceeding the critical power for ponderomotive electron cavitation. For both colors, the {ital f} number of the probe beam is increased as it propagates through the plasma. Transmission of the diffraction-limited beams is higher for the green than for the 1 {mu}m case. {copyright} {ital 1998 American Institute of Physics.}

  5. Continuous blood oxygen saturation detection with single-wavelength photoacoustics

    NASA Astrophysics Data System (ADS)

    Peng, Qiwen; Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

    2015-03-01

    Blood oxygen saturation (SO2) reflects the oxygenation level in blood transport and tissue. Previous studies have shown the capability of non-invasive quantitative measurements of SO2 by multi-wavelength photoacoustic (PA) spectroscopy for diagnosis of brain, tumor hemodynamics and other pathophysiological phenomena. However, those multi-wavelength methods require a tunable laser or multiple lasers which are relatively expensive and bulky for filed measurement environment and applications. Besides, the operation of multiple wavelengths, calibration procedures and data processing gets system complicated, which reduces the feasibility and flexibility for continuous real-time monitoring. Here we report a newly proposed method by combining PA and scattered light signals wherein imposing a hypothesis that scattering intensity is linear to the concentrations of oxygenated hemoglobin and deoxygenated hemoglobin weighed by blood scattering coefficients. A rigorous theoretical relationship between PA and scattering signals is thus established, making it possible that SO2 can be measured with only one excitation wavelength. To verify the theory basis, both dual-ink phantoms and fresh porcine blood sample have been employed in the experiments. The phantom experiment is able to quantify the concentration of mixed red-green ink that is in precise agreement with pre-set values. The ex vivo experiment with fresh porcine blood was conducted and the results of the proposed single-wavelength method achieved high accuracy of 1% - 4% errors. These demonstrated that the proposed single-wavelength SO2 detection is able to provide non-invasive, accurate measurement of blood oxygenation, and herein create potential for applying it to real clinical applications with low cost and high flexibility.

  6. Analysis of calibration-free wavelength-scanned wavelength modulation spectroscopy for practical gas sensing using tunable diode lasers

    NASA Astrophysics Data System (ADS)

    Sun, K.; Chao, X.; Sur, R.; Goldenstein, C. S.; Jeffries, J. B.; Hanson, R. K.

    2013-12-01

    A novel strategy has been developed for analysis of wavelength-scanned, wavelength modulation spectroscopy (WMS) with tunable diode lasers (TDLs). The method simulates WMS signals to compare with measurements to determine gas properties (e.g., temperature, pressure and concentration of the absorbing species). Injection-current-tuned TDLs have simultaneous wavelength and intensity variation, which severely complicates the Fourier expansion of the simulated WMS signal into harmonics of the modulation frequency (fm). The new method differs from previous WMS analysis strategies in two significant ways: (1) the measured laser intensity is used to simulate the transmitted laser intensity and (2) digital lock-in and low-pass filter software is used to expand both simulated and measured transmitted laser intensities into harmonics of the modulation frequency, WMS-nfm (n = 1, 2, 3,…), avoiding the need for an analytic model of intensity modulation or Fourier expansion of the simulated WMS harmonics. This analysis scheme is valid at any optical depth, modulation index, and at all values of scanned-laser wavelength. The method is demonstrated and validated with WMS of H2O dilute in air (1 atm, 296 K, near 1392 nm). WMS-nfm harmonics for n = 1 to 6 are extracted and the simulation and measurements are found in good agreement for the entire WMS lineshape. The use of 1f-normalization strategies to realize calibration-free wavelength-scanned WMS is also discussed.

  7. Wavelength conversion by dynamically reconfiguring a nested photonic crystal cavity.

    PubMed

    Khorshidahmad, Amin; Kirk, Andrew G

    2010-04-12

    A dynamically reconfigurable nested photonic crystal cavity suitable for frequency conversion applications is proposed. Dynamic switching between two distinct cavities allows intermodal transition via spatially-uniform tuning of the refractive index. Exclusion of the initial resonant mode from the Eigen modes of the tuned cavity precludes the adiabatic wavelength conversion process. Multiple intermodal transitions are suppressed by the symmetry of the mode profiles of the two cavities. Over 90nm wavelength shift (from L-band to the S-band) is shown numerically. PMID:20588614

  8. Three Dimensional Imaging with Multiple Wavelength Speckle Interferometry

    SciTech Connect

    Bernacki, Bruce E.; Cannon, Bret D.; Schiffern, John T.; Mendoza, Albert

    2014-05-28

    We present the design, modeling, construction, and results of a three-dimensional imager based upon multiple-wavelength speckle interferometry. A surface under test is illuminated with tunable laser light in a Michelson interferometer configuration while a speckled image is acquired at each laser frequency step. The resulting hypercube is Fourier transformed in the frequency dimension and the beat frequencies that result map the relative offsets of surface features. Synthetic wavelengths resulting from the laser tuning can probe features ranging from 18 microns to hundreds of millimeters. Three dimensional images will be presented along with modeling results.

  9. Femtosecond laser color marking stainless steel surface with different wavelengths

    NASA Astrophysics Data System (ADS)

    Li, Guoqiang; Li, Jiawen; Hu, Yanlei; Zhang, Chenchu; Li, Xiaohong; Chu, Jiaru; Huang, Wenhao

    2015-03-01

    The femtosecond laser color marking stainless steel surfaces with different incident wavelengths were investigated theoretically and experimentally. It indicates that the spectral regions of the colors firstly increase and then reduce with increasing spatial periods of the ripples induced by laser irradiation. Additionally, the colors are gradually changed from blue to red due to the elongation of the diffracted light wavelengths. As a result, the color effects are distinctly different. This study offers a new controllable parameter to produce diverse colors, which may find a wide range of applications in the laser color marking, art designing and so on.

  10. A millimeter wavelength radiation source using a dual grating resonator

    SciTech Connect

    Killoran, J.H.; Hacker, F.L.; Walsh, J.E. (Dartmouth Coll., Hanover, NH (United States). Dept. of Physics)

    1994-10-01

    A novel means of producing coherent radiation by passing an electron through a dual-grating resonator is presented. The observed radiation is in accordance with the Smith-Purcell dispersion relation for a single grating. Feedback is provided by a second grating. Experiments carried out at beam energies from 30--55 KeV produced radiation at wavelengths from 6 to 0.75 mm. Power measurements were used to clarify the grating-beam interaction. Indications are that operation could be easily extended to shorter wavelengths to provide an inexpensive and compact radiation source in the far-infrared.

  11. Dual wavelength digital holography for 3D particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Grare, S.; Coëtmellec, S.,; Allano, D.; Grehan, G.; Brunel, M.; Lebrun, D.

    2015-02-01

    A multi-exposure digital in-line hologram of a moving particle field is recorded by two different wavelengths and at different times. As a result, during the reconstruction step, each hologram can be independently and accurately reconstructed for each wavelength. This procedure enables avoiding the superimposition of particles images that may be close to each other in multi-exposure holography. The feasibility is demonstrated by using a standard particle sizing reticle and shows the potential of this method for particle velocity measurement.

  12. Inversion of 2 wavelength Lidar data for cloud properties

    NASA Technical Reports Server (NTRS)

    Pal, S. R.; Carswell, A. I.

    1986-01-01

    The inversion of the lidar equation to derive quantitative properties of the atmosphere has continued to present considerable difficulty. The results of a study in which Klett's procedure was utilized for the analysis of cloud backscatter measurements made simulataneously at two ruby lidar wavelengths (694nm,347nmm) are presented. With one lidar system a cloud is probed at the two wavelength and the backscatter measured simulataneously by separate receivers. As a result two sigma profiles which should differ only because the wavlength dependence of the scattering. Experimental data presented to demonstrate the effects and the implications of the applications of the inversion method will be discussed.

  13. Förster energy transfer induced random lasing at unconventional excitation wavelengths

    NASA Astrophysics Data System (ADS)

    Shadak Alee, K.; Barik, Sabyasachi; Mujumdar, Sushil

    2013-11-01

    We experimentally demonstrate efficient lasing from a Rhodamine-nanoscatterer random laser when pumped with unconventional wavelengths, at which the absorption of Rhodamine is negligible. Förster-type energy transfer was realized by using Coumarin molecules as donors. Explicit time-resolved spectroscopy provided direct evidence for the nonradiative transfer with ˜48% efficiency. We obtained lasing at reduced thresholds by a factor of over 3 and increased amplification rates by a factor of ˜4 in the Förster regime, even in samples with sub-diffusive disorder strength. We characterize the efficacy of the Förster transfer induced lasing over a range of unconventional wavelengths for the Rh-based system.

  14. Micro-fading spectrometry: investigating the wavelength specificity of fading

    NASA Astrophysics Data System (ADS)

    Lerwill, Andrew; Brookes, Anna; Townsend, Joyce H.; Hackney, Stephen; Liang, Haida

    2015-02-01

    A modified microfading spectrometer incorporating a linear variable filter is used to investigate the wavelength dependence of fading of traditional watercolour pigments, dosimeters and fading standards at a higher spectral resolution and/or sampling than had previously been attempted. While the wavelength dependence of photochemical damage was largely found to correlate well with the absorption spectra of each material, exceptions were found in the case of Prussian blue and Prussian green pigments (the latter includes Prussian blue), for which an anti-correlation between the spectral colour change and the absorption spectrum was found.

  15. Thermal characterization of optical fibers using wavelength-sweeping interferometry.

    PubMed

    Perret, Luc; Pfeiffer, Pierre; Serio, Bruno; Twardowski, Patrice

    2010-06-20

    In this paper, we report a new method of thermal characterization of optical fibers using wavelength-sweeping interferometry and discuss its advantages compared to other techniques. The setup consists of two temperature-stabilized interferometers, a reference Michelson and a Mach-Zehnder, containing the fiber under test. The wavelength sweep is produced by an infrared tunable laser diode. We obtained the global phase shift coefficients of a large effective area fiber and gold-coated fiber optics with a 10(-7) accuracy. PMID:20563215

  16. Total absorption of light in sub-wavelength metallic waveguides

    NASA Astrophysics Data System (ADS)

    Ghossoub, Marc G.; Sinha, Sanjiv

    2013-12-01

    Resonance cavity modes enhance optical transmission through sub-wavelength metallic apertures but their role in absorption remains unclear. Here, we use full field simulation and a semi-analytical model to report absorption and transmission enhancement in transmission gratings under transverse electric illumination. The fundamental cavity mode of the sub-wavelength grating cavities is the major contributor to absorption. We demonstrate the possibility of tailoring such cavity resonances to induce total absorption in reflection gratings. Our method advances the understanding of transmittance and absorption enhancing mechanisms in metallic nanostructures which constitute fundamental components in energy harvesting, sensing, and spectroscopic applications.

  17. Three-dimensional blast-wave-driven Rayleigh-Taylor instability and the effects of long-wavelength modes

    SciTech Connect

    Kuranz, C. C.; Drake, R. P.; Grosskopf, M. J.; Budde, A.; Krauland, C.; Marion, D. C.; Visco, A. J.; Ditmar, J. R. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Robey, H. F.; Remington, B. A.; Miles, A. R.; Cooper, A. B. R.; Sorce, C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Plewa, T. [Department of Scientific Computing, Florida State University, Tallahassee, Florida 32306 (United States); Hearn, N. C. [ASC Flash Center, University of Chicago, Chicago, Illinois 60637 (United States); Killebrew, K. L. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States); Knauer, J. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York (United States); Arnett, D. [Steward Observatory, University of Arizona, Tucson, Arizona 85721 (United States); Donajkowski, T. [Jet Propulsion Laboratory, Pasadena, California 91109 (United States)

    2009-05-15

    This paper describes experiments exploring the three-dimensional (3D) Rayleigh-Taylor instability at a blast-wave-driven interface. This experiment is well scaled to the He/H interface during the explosion phase of SN1987A. In the experiments, {approx}5 kJ of energy from the Omega laser was used to create a planar blast wave in a plastic disk, which is accelerated into a lower-density foam. These circumstances induce the Richtmyer-Meshkov instability and, after the shock passes the interface, the system quickly becomes dominated by the Rayleigh-Taylor instability. The plastic disk has an intentional pattern machined at the plastic/foam interface. This perturbation is 3D with a basic structure of two orthogonal sine waves with a wavelength of 71 {mu}m and an amplitude of 2.5 {mu}m. Additional long-wavelength modes with a wavelength of either 212 or 424 {mu}m are added onto the single-mode pattern. The addition of the long-wavelength modes was motivated by the results of previous experiments where material penetrated unexpectedly to the shock front, perhaps due to an unintended structure. The current experiments and simulations were performed to explore the effects of this unintended structure; however, we were unable to reproduce the previous results.

  18. The Stability of Low Surface Brightness Disks Based on Multi-wavelength Modeling

    NASA Astrophysics Data System (ADS)

    MacLachlan, J. M.; Matthews, L. D.; Wood, K.; Gallagher, J. S.

    2011-11-01

    To investigate the structure and composition of the dusty interstellar medium (ISM) of low surface brightness (LSB) disk galaxies, we have used multi-wavelength photometry to construct spectral energy distributions for three low-mass, edge-on LSB galaxies (V rot = 88-105 km s-1). We use Monte Carlo radiation transfer codes that include the effects of transiently heated small grains and polycyclic aromatic hydrocarbon molecules to model and interpret the data. We find that, unlike the high surface brightness galaxies previously modeled, the dust disks appear to have scale heights equal to or exceeding their stellar scale heights. This result supports the findings of previous studies that low-mass disk galaxies have dust scale heights comparable to their stellar scale heights and suggests that the cold ISM of low-mass, LSB disk galaxies may be stable against fragmentation and gravitational collapse. This may help to explain the lack of observed dust lanes in edge-on LSB galaxies and their low current star formation rates. Dust masses are found in the range (1.16-2.38) × 106 M sun, corresponding to face-on (edge-on), V-band, optical depths 0.034 <~ ?face <~ 0.106 (0.69 <~ ?eq <~ 1.99).

  19. THE STABILITY OF LOW SURFACE BRIGHTNESS DISKS BASED ON MULTI-WAVELENGTH MODELING

    SciTech Connect

    MacLachlan, J. M.; Wood, K. [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS (United Kingdom); Matthews, L. D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-42, Cambridge, MA 02138 (United States); Gallagher, J. S., E-mail: jmm55@st-andrews.ac.uk [Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53706 (United States)

    2011-11-01

    To investigate the structure and composition of the dusty interstellar medium (ISM) of low surface brightness (LSB) disk galaxies, we have used multi-wavelength photometry to construct spectral energy distributions for three low-mass, edge-on LSB galaxies (V{sub rot} = 88-105 km s{sup -1}). We use Monte Carlo radiation transfer codes that include the effects of transiently heated small grains and polycyclic aromatic hydrocarbon molecules to model and interpret the data. We find that, unlike the high surface brightness galaxies previously modeled, the dust disks appear to have scale heights equal to or exceeding their stellar scale heights. This result supports the findings of previous studies that low-mass disk galaxies have dust scale heights comparable to their stellar scale heights and suggests that the cold ISM of low-mass, LSB disk galaxies may be stable against fragmentation and gravitational collapse. This may help to explain the lack of observed dust lanes in edge-on LSB galaxies and their low current star formation rates. Dust masses are found in the range (1.16-2.38) x 10{sup 6} M{sub sun}, corresponding to face-on (edge-on), V-band, optical depths 0.034 {approx}< {tau}{sub face} {approx}< 0.106 (0.69 {approx}< {tau}{sub eq} {approx}< 1.99).

  20. A highly stable and reliable wavelength monitor integrated laser module design

    Microsoft Academic Search

    Hideyuki Nasu; Tomohiro Takagi; Tatsuyuki Shinagawa; Mizuki Oike; Takehiko Nomura; Akihiko Kasukawa

    2004-01-01

    Three existing wavelength monitor integrated laser module designs are evaluated. The shortcomings of these designs are resolved by a unique design that eases alignment tasks and greatly enhances the wavelength stability and the wavelength tunability. For example, the wavelength drift over case temperature is 16 times smaller than the best result of previous reports. With the incorporation of thermal compensation,

  1. Blackbody radiation shifts and magic wavelengths for atomic clock research

    E-print Network

    Safronova, Marianna

    Blackbody radiation shifts and magic wavelengths for atomic clock research M. S. Safronova of interest to atomic clock development are reported. We also calculated the blackbody radiation shift The operation of atomic clocks is generally carried out at room temperature, whereas the definition

  2. Reflective silicon binary diffraction grating for visible wavelengths

    E-print Network

    Li, Jingjing

    on subwavelength resonant grating technology. Using a single lithography step we built a reflective binary grating that efficient subwavelength resonant devices for visible wavelengths can be built using silicon. © 2011 Optical with the resonantly scattered light can be used to control the phase front of the reflected light [5] and, therefore

  3. Enhancing the frequency response of cross-polarization wavelength conversion

    Microsoft Academic Search

    Chia Chien Wei; Ming Fang Huang; J. j. Chen

    2005-01-01

    This work presents a novel wavelength conversion scheme, differential cross-polarization modulation (DXPoM), using an extra birefringence delay to enhance the performance of the conventional cross-polarization modulation. Simulation and experimental results confirm that the predicted performance is enhanced. Using the proposed scheme improves rise time by over 300%, reduces timing jitter by 50%, and increases extinction ratio by 9%.

  4. Time Analysis of the Wavelength Shift in Fiber Bragg Gratings

    Microsoft Academic Search

    Paulo de Tarso Neves; Alexandre de Almeida Prado Pohl

    2007-01-01

    This paper presents the time analysis of the Bragg wavelength shift in fiber gratings based on the elastodynamics theory. The model is valuable for estimating an upper limit for the tuning speed when traction forces are applied to the free end of the grating. A comparison between the single-mode silica optical fiber and polymer optical fiber is performed, showing the

  5. Resonator design for a visible wavelength free-electron laser (*)

    SciTech Connect

    Bhowmik, A.; Lordi, N. (Rockwell International Corp., Canoga Park, CA (United States). Rocketdyne Div.); Ben-Zvi, I.; Gallardo, J. (Brookhaven National Lab., Upton, NY (United States))

    1990-01-01

    Design requirements for a visible wavelength free-electron laser being developed at the Accelerator Test Facility at Brookhaven National Laboratory are presented along with predictions of laser performance from 3-D numerical simulations. The design and construction of the optical resonator, its alignment and control systems are also described. 15 refs., 8 figs., 4 tabs.

  6. Semiconductor lasers beyond the fiber optics telecommunication wavelength

    Microsoft Academic Search

    Alexander Soibel; Kamjou Mansour; Andrew A. Shapiro; Gary D. Spiers; Siamak Forouhar

    2005-01-01

    Semiconductor lasers emitting at 1.55 microns are the cornerstone of the high bandwidth optical communications industry. Semiconductor lasers operating at this and other wavelengths are also used in the engineering, biology, chemistry and medical fields. The light emission in most semiconductor lasers is due to the optical transition between the valence and conduction bands of the semiconductor active material. This

  7. Estimation and discrimination of aerosols using multiple wavelength LWIR lidar

    Microsoft Academic Search

    Russell E. Warren; Richard G. Vanderbeek; Jeffrey L. Ahl

    2010-01-01

    This paper presents an overview of recent work by the Edgewood Chemical Biological Center (ECBC) in algorithm development for parameter estimation and classification of localized atmospheric aerosols using data from rapidly tuned multiple-wavelength range-resolved LWIR lidar. The motivation for this work is the need to detect, locate, and discriminate biological threat aerosols in the atmosphere from interferent materials such as

  8. Two-dimensional optical beam deflector operated by wavelength tuning

    NASA Astrophysics Data System (ADS)

    Toyoshima, Morio; Fidler, Franz; Pfennigbauer, Martin; Leeb, Walter R.

    2006-05-01

    A new method based on an optical delay line structure is proposed for two-dimensional raster optical beam steering. For one-dimensional beam steering, the laser beam to be deflected is split into N co-directional sub-beams of equal intensity with the aid of a plane-parallel plate. These sub-beams experience a relative time delay, which translates into a phase difference, thus forming a phased array. When the laser wavelength is tuned, the relative phase varies and the far-field interference footprint can be steered across a receive plane. By employing two plane-parallel plates in series, the described scheme can be extended to produce a two-dimensional N × N array of sub-beams, allowing two-dimensional beam steering via wavelength tuning. In this case, wavelength tuning over a larger range leads to a linear deflection which repeats itself in a raster-like fashion. One direction of deflection repeats itself multiple times as wavelength is scanned over larger range, that is, a raster effect. In this paper, the principle is theoretically derived and formulated, and the preliminary experimental results with four sub-beams are presented.

  9. Two-photon microscopy with wavelength switchable fiber laser excitation

    E-print Network

    Unruh, Jay R.; Price, E. Shane; Molla, Roque Gagliano; Stehno-Bittel, Lisa; Johnson, Carey K.; Hui, Rongqing

    2006-10-16

    Two-photon microscopy with wavelength switchable fiber laser excitation Jay R. Unruh,1 E. Shane Price,1 Roque Gagliano Molla,2 Lisa Stehno-Bittel,3 Carey K. Johnson,1 and Rongqing Hui2 1, Department of Chemistry, University of Kansas, Lawrence...

  10. A wavelength discrimination function for the hummingbird Archilochus alexandri

    Microsoft Academic Search

    Timothy H. Goldsmith; James S. Collins; Dan L. Perlman

    1981-01-01

    Free-flying black-chinned hummingbirds (Archilochus alexandri) at a site in southeastern Arizona were attracted to artificial feeders displaying narrow spectral bands of light (7 nm half band width). The birds were taught to discriminate between pairs of wavelengths of approximately equal brightness but with a spectral separation of 10 nm. After training, performance of the birds was not significantly changed by

  11. A Comparative Study of Limited Range Wavelength Conversion Policies for

    E-print Network

    Akar, Nail

    ) packet'' and ``(optical) packet switching'' to refer to a packet/burst and the data planes of OPS for supporting asynchronous IP networks with variable sized data packets. Therefore, we focus our attentionA Comparative Study of Limited Range Wavelength Conversion Policies for Asynchronous Optical Packet

  12. Wavelength-compensated Fourier and Fresnel transformers: a unified approach

    Microsoft Academic Search

    J. Lancis; G. Minguez-Vega; E. Tajahuerce; M. Fernandez-Alonso; V. Climent; P. Andres

    2002-01-01

    We recognize that one can adapt any dispersion-compensated broadband optical Fourier transformer to achieve wavelength compensation in the Fresnel diffraction region just by inserting a diffractive lens at the input plane and vice versa. This unification procedure is employed in a second stage in the design of a novel hybrid (diffractive-refractive) optical setup that provides, in a sequential way, nearly

  13. Multi-quantum-well nanowire heterostructures for wavelength-controlled

    E-print Network

    Wang, Zhong L.

    /Si core/shell nanowires have exhibited substantially higher performance as field-effect transistors3LETTERS Multi-quantum-well nanowire heterostructures for wavelength-controlled lasers FANG QIAN1 the first multi-quantum-well (MQW) core/shell nanowire heterostructures based on well-defined III

  14. Tunnel junction multiple wavelength light-emitting diodes

    DOEpatents

    Olson, J.M.; Kurtz, S.R.

    1992-11-24

    A multiple wavelength LED having a monolithic cascade cell structure comprising at least two p-n junctions, wherein each of said at least two p-n junctions have substantially different band gaps, and electrical connector means by which said at least two p-n junctions may be collectively energized; and wherein said diode comprises a tunnel junction or interconnect. 5 figs.

  15. Efficient Implementations of Heuristics for Routing and Wavelength Assignment

    E-print Network

    Resende, Mauricio G. C.

    networks is transmitted through optical fibers as optical signals. Each link operates at a speed efficient use of the huge capacity of optical fibers, as far as it permits the simultaneous transmission of different channels along the same fiber, each of them using a different wavelength. An all-optical point

  16. Efficient Wavelength Routing in Trees with Low--Degree Converters

    E-print Network

    Caragiannis, Ioannis

    converters of constant degree. 1. Introduction Optical fiber is rapidly becoming the standard transmission consists in first converting the optical signal to electronic and then back to optical on the desired announced [12, 25]. A wavelength converter is a device that allows the conversion of optical signals from o

  17. Design of Wavelength Converting Switches for Optical Burst Switching

    E-print Network

    nonblocking switch. I. INTRODUCTION THE transmission capacity of optical fibers has been increasing the electronic line cards needed to terminate the channels from just a sin- gle fiber. Optical burst switchingDesign of Wavelength Converting Switches for Optical Burst Switching Jeyashankher Ramamirtham

  18. Pupillary behavior in relation to wavelength and age.

    PubMed

    Lobato-Rincón, Luis-Lucio; Cabanillas-Campos, Maria Del Carmen; Bonnin-Arias, Cristina; Chamorro-Gutiérrez, Eva; Murciano-Cespedosa, Antonio; Sánchez-Ramos Roda, Celia

    2014-01-01

    Pupil light reflex can be used as a non-invasive ocular predictor of cephalic autonomic nervous system integrity. Spectral sensitivity of the pupil's response to light has, for some time, been an interesting issue. It has generally, however, only been investigated with the use of white light and studies with monochromatic wavelengths are scarce. This study investigates the effects of wavelength and age within three parameters of the pupil light reflex (amplitude of response, latency, and velocity of constriction) in a large sample of younger and older adults (N = 97), in mesopic conditions. Subjects were exposed to a single light stimulus at four different wavelengths: white (5600°K), blue (450 nm), green (510 nm), and red (600 nm). Data was analyzed appropriately, and, when applicable, using the General Linear Model (GLM), Randomized Complete Block Design (RCBD), Student's t-test and/or ANCOVA. Across all subjects, pupillary response to light had the greatest amplitude and shortest latency in white and green light conditions. In regards to age, older subjects (46-78 years) showed an increased latency in white light and decreased velocity of constriction in green light compared to younger subjects (18-45 years old). This study provides data patterns on parameters of wavelength-dependent pupil reflexes to light in adults and it contributes to the large body of pupillometric research. It is hoped that this study will add to the overall evaluation of cephalic autonomic nervous system integrity. PMID:24795595

  19. Absolute analytical prediction of photonic crystal guided mode resonance wavelengths

    SciTech Connect

    Hermannsson, Pétur Gordon; Vannahme, Christoph; Smith, Cameron L. C.; Kristensen, Anders, E-mail: anders.kristensen@nanotech.dtu.dk [Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads, Building 345E, DK-2800 Kgs. Lyngby (Denmark)

    2014-08-18

    A class of photonic crystal resonant reflectors known as guided mode resonant filters are optical structures that are widely used in the field of refractive index sensing, particularly in biosensing. For the purposes of understanding and design, their behavior has traditionally been modeled numerically with methods such as rigorous coupled wave analysis. Here it is demonstrated how the absolute resonance wavelengths of such structures can be predicted by analytically modeling them as slab waveguides in which the propagation constant is determined by a phase matching condition. The model is experimentally verified to be capable of predicting the absolute resonance wavelengths to an accuracy of within 0.75?nm, as well as resonance wavelength shifts due to changes in cladding index within an accuracy of 0.45?nm across the visible wavelength regime in the case where material dispersion is taken into account. Furthermore, it is demonstrated that the model is valid beyond the limit of low grating modulation, for periodically discontinuous waveguide layers, high refractive index contrasts, and highly dispersive media.

  20. FPGA IMPLEMENTATION OF MIMO SYMBOL-WAVELENGTH-SPACED

    E-print Network

    Petersen, Brent

    FPGA IMPLEMENTATION OF MIMO SYSTEM FOR SYMBOL-WAVELENGTH-SPACED ANTENNAS by Harshal Desai B on that separation. The system was implemented on a single Field Programmable Gate Array (FPGA) board. The adaptive to Troy Lavigne for providing valuable support and knowledge of FPGA technology and software. I would also