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Sample records for high contrast object

  1. Object-based high contrast travel time tomography

    CERN Document Server

    Lin, Yenting

    2013-01-01

    We consider travel time tomography problems involving detection of high contrast, discrete high velocity structures. This results in a discrete nonlinear inverse problem, for which traditional grid-based models and iterative linearized least-squares reconstruction algorithms are not suitable. This is because travel paths change significantly near the high contrast velocity structure, making it more difficult to inversely calculate the travel path and infer the velocity along the path. We propose a model-based approach to describe the high velocity structure using pre-defined elementary objects. Compared to a grid-based model, our approach has complexity that increases as a function of the number of objects, rather than increasing with the number of cells (usually very large). A new reconstruction algorithm is developed that provides estimates of the probability that a high velocity structure appears at any point in the region of interest. Simulation results show that our method can efficiently sample the mode...

  2. The SEEDS High-Contrast Imaging Survey of Exoplanets Around Young Stellar Objects

    Science.gov (United States)

    Uyama, Taichi; Hashimoto, Jun; Kuzuhara, Masayuki; Mayama, Satoshi; Akiyama, Eiji; Currie, Thayne; Livingston, John; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Henning, Thomas; Hodapp, Klaus W.; Ishii, Miki; Iye, Masanori; Janson, Markus; Kandori, Ryo; Knapp, Gillian R.; Kwon, Jungmi; Matsuo, Taro; Mcelwain, Michael W.; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takahashi, Yasuhiro H.; Takami, Michihiro; Takato, Naruhisa; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L.; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2017-03-01

    We present high-contrast observations of 68 young stellar objects (YSOs) that have been explored as part of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS) survey on the Subaru telescope. Our targets are very young (population of planets and brown dwarfs at the very youngest ages; these may be compared to the results of surveys targeting somewhat older stars. Our sample and the associated observational results will help enable detailed statistical analyses of giant planet formation.

  3. The SEEDS High Contrast Imaging Survey of Exoplanets around Young Stellar Objects

    CERN Document Server

    Uyama, Taichi; Kuzuhara, Masayuki; Mayama, Satoshi; Akiyama, Eiji; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D; Carson, Joseph C; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S; Henning, Thomas; Hodapp, Klaus W; Ishii, Miki; Iye, Masanori; Janson, Markus; Kandori, Ryo; Knapp, Gillian R; Kwon, Jungmi; Matsuo, Taro; Mcelwain, Michael W; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takahashi, Yasuhiro H; Takami, Michihiro; Takato, Naruhisa; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2016-01-01

    We present high-contrast observations of 68 young stellar objects (YSOs) taken as part of the SEEDS survey on the Subaru telescope. Our targets are very young ($<$10 Myr) stars, which often harbor protoplanetary disks where planets may be forming. We achieve typical contransts of $\\sim$$10^{-4}$-$10^{-5.5}$ at the angular distance of 1$\\arcsec$ from the central star, corresponding to typical mass sensitivities (assuming hot-start evolutionary models) of $\\sim$10 ${\\rm M_J}$ at 70 AU and $\\sim$6 ${\\rm M_J}$ at 140 AU. We have detected a stellar companion to HIP 79462 and confirmed the substellar objects GQ Lup b and ROXs 42B b. An additional six companion candidates await follow-up observations to check for common proper-motion. Our SEEDS YSO observations prove the population of planets and brown dwarfs at the very youngest ages, these may be compared to the results of surveys targeting somewhat older stars. We will present a detailed statistical analysis of our sample and its implications for giant planet ...

  4. High Contrast CRT.

    Science.gov (United States)

    1979-08-01

    r AD’ A076 235 WATKINS—JOHNSON Co SCOTYS VAL LEY CA F/S 9/5 N HIGH CONTRAST CRT.CU) AUG 79 6 A HOLNQUIST DAABO7—77—C—263 9 UNCLASSIFIED DEL.ET—TR—77...Air Force Systems Command A t t n : l) l . CA 2w) U I f iee ’ of \\ iva l Re ’~.ea r ch Andr ews AFI4 ( • ~~ii 4.~7 001 Washington , l ) .C. 20331

  5. Comparison of detectability of a simple object with low contrast displayed on a high-brightness color LCD and a monochrome LCD.

    Science.gov (United States)

    Takahashi, Keita; Morishita, Junji; Hiwasa, Takeshi; Hatanaka, Shiro; Sakai, Shuji; Hashimoto, Noriyuki; Nakamura, Yasuhiko; Toyofuku, Fukai; Higashida, Yoshiharu; Ohki, Masafumi

    2010-07-01

    The goal of this study was to investigate the effect of the different luminance settings of a high-brightness color liquid-crystal display (LCD) on the detectability of a simple grayscale object with low contrast by use of receiver operating characteristic (ROC) analysis. The detectability of a high-brightness color LCD with two maximum-luminance settings (500 and 170 cd/m(2)) was compared with the detectability of a monochrome LCD (500 cd/m(2)). The two LCDs used in this study were calibrated to the grayscale standard display function. The average areas under the ROC curve (AUCs) and the standard deviations for all thirteen observers for the 500 cd/m(2) color LCD, 500 cd/m(2) monochrome LCD, and 170 cd/m(2) color LCD were 0.937 +/- 0.040, 0.924 +/- 0.056, and 0.915 +/- 0.068, respectively. There were no statistically significant differences in the average AUCs among the three LCD monitor conditions. On the other hand, the total observation time for the 170 cd/m(2) color LCD was significantly shorter than that for the 500 cd/m(2) color and monochrome LCDs (p LCD provided a performance comparable to the monochrome LCD for detection of a simple grayscale object with low contrast.

  6. High-contrast imaging testbed

    Energy Technology Data Exchange (ETDEWEB)

    Baker, K; Silva, D; Poyneer, L; Macintosh, B; Bauman, B; Palmer, D; Remington, T; Delgadillo-Lariz, M

    2008-01-23

    Several high-contrast imaging systems are currently under construction to enable the detection of extra-solar planets. In order for these systems to achieve their objectives, however, there is considerable developmental work and testing which must take place. Given the need to perform these tests, a spatially-filtered Shack-Hartmann adaptive optics system has been assembled to evaluate new algorithms and hardware configurations which will be implemented in these future high-contrast imaging systems. In this article, construction and phase measurements of a membrane 'woofer' mirror are presented. In addition, results from closed-loop operation of the assembled testbed with static phase plates are presented. The testbed is currently being upgraded to enable operation at speeds approaching 500 hz and to enable studies of the interactions between the woofer and tweeter deformable mirrors.

  7. Object size, spatial-frequency content and retinal contrast

    Science.gov (United States)

    Rizzi, Alessandro

    2010-02-01

    Recent interest in HDR scene capture and display has stimulated measurements of the usable range of contrast information for human vision. These experiments have led to a model that calculates the retinal contrast image. A fraction of the light from each scene pixel is scattered to all retinal pixels. The amount of scattered light decreases with distance from the other pixels. By summing the light falling on each retinal pixel from all the scene pixels we can calculate the retinal image contrast. As objects, such as text letters, get smaller, their retinal contrast gets lower, even though the scene contrast is constant. This paper studies the Landolt C data, a commonly used test targets for measuring visual acuity, using three frameworks. First, it compares the visual acuity measurements with the receptor mosaic dimension. Second, discusses the Campbell and Robson's experiments and the limits of the Contrast Sensitivity Function (CSF). Third, the paper reports the calculated retinal stimulus after intraocular scatter of both Landolt C and Campbell and Robson's stimuli. These three different frameworks are useful in understanding limits of human vision. Each approach gives only one piece of the puzzle. Retinal contrast, CSF, and retinal cone spacing all influence our understanding of human vision limits. We have analyzed Landolt C and CSF using retinal contrast. Glare effect on Landolt C shows that retinal images are significantly different from target images. Veiling glare of the sine-wave stimuli used by Campbell and Robson to measure CSF, results in a retinal contrast decrease. This, above 3-4 cpd, correlates well with the data reported by them.

  8. Daylight illumination-color-contrast tables for full-form objects naturally illuminated objects

    CERN Document Server

    Nagel, M

    1978-01-01

    Daylight Illumination-Color-Contrast Tables for Full-form Objects is the result of a major computational project concerning the illumination, color, and contrast conditions in naturally illuminated objects. The project from which this two-chapter book is derived is originally conceived in support of the various remote sensing and image processing activities of the Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt, Oberpfaffenhofen, West Germany DFVLR, in particular, those depending on the quantitative photometric and colorimetric evaluation of photographs and other environmental

  9. Quantifying the perceived interest of objects in images: effects of size, location, blur, and contrast

    Science.gov (United States)

    Kadiyala, Vamsi; Pinneli, Srivani; Larson, Eric C.; Chandler, Damon M.

    2008-02-01

    This paper presents the results of two psychophysical experiments designed to investigate the effects of size, location, blur, and contrast on the perceived visual interest of objects within images. In the first experiment, digital composting was used to create images containing objects (humans, animals, and non-living objects) which varied in controlled increments of size, location, blur, and contrast. Ratings of perceived interest were then measured for each object. We found that: (1) As object size increases, perceived interest increases but exhibits diminished gains for larger sizes; (2) As an object moves from the center of the image toward the image's edge, perceived interest decreases nearly linearly with distance; (3) Blurring imposes a substantial initial decrease in perceived interest, but this drop is relatively lessened for highly blurred objects; (4) As an object's RMS contrast is increased, perceived interest increases nearly linearly. Furthermore, these trends were quite similar for all three categories (human, animal, non-living object). To determine whether these data can predict the perceived interest of objects in real, non-composited images, a second experiment was performed in which subjects rated the visual interest of each of 562 objects in 150 images. Based on these results, an algorithm is presented which, given a segmented image, attempts to generate an object-level interest map.

  10. Contrast discrimination at high contrasts reveals the influence of local light adaptation on contrast processing.

    Science.gov (United States)

    Kingdom, F A; Whittle, P

    1996-03-01

    Previous measurements of contrast discrimination threshold, delta C, as a function of pedestal contrast, C, for sine-wave gratings have shown a power law relationship between delta C and C at suprathreshold levels of C. However, these studies have rarely used contrasts greater than 50%. Whittle (1986), using incremental and decremental patches, found that delta C increased with C only up to about 50%. At higher contrasts it decreased. Since a periodic stimulus can be considered to be composed of increments and decrements, we thought we might find such an inverse U-shaped function for gratings if we used contrasts up to 100%. We tested this for both sine-wave and square-wave stimuli at spatial frequencies from 0.0625 to 8.0 c/deg. We found that for frequencies up to 0.5 c/deg, delta C in nearly all cases 'dipped down' after about C = 50% contrast. At 4.0 and 8.0 c/deg, however, no dip-down occurred. Additional experiments showed that the dip-down was unlikely to be due to cortical long-term adaptation and most likely an effect of localized light adaptation to the dark bars. We argue that the absence of dip-down at high spatial frequencies was mainly due to the attenuation of contrast by the optics of the eye. As for the results of Whittle (1986), a Weber's Law in W = (Lmax-Lmin)/Lmin describes the inverse U-shaped contrast discrimination function well. Two other contrast expressions also linearize the data on log-log plots. We show how some familiar notions about the physiological operation of localized light adaptation can easily account for the form of the contrast discrimination function. Finally we estimate the number of discriminable steps in contrast from detection threshold to maximum contrast for the various spatial frequencies tested.

  11. NASA High Contrast Imaging for Exoplanets

    Science.gov (United States)

    Lyon, Richard G.

    2008-01-01

    Described is NASA's ongoing program for the detection and characterization of exosolar planets via high-contrast imaging. Some of the more promising proposed techniques under assessment may enable detection of life outside our solar system. In visible light terrestrial planets are approximately 10(exp -10) dimmer than the parent star. Issues such as diffraction, scatter, wavefront, amplitude and polarization all contribute to a reduction in contrast. An overview of the techniques will be discussed.

  12. Homogenization of High-Contrast Brinkman Flows

    KAUST Repository

    Brown, Donald L.

    2015-04-16

    Modeling porous flow in complex media is a challenging problem. Not only is the problem inherently multiscale but, due to high contrast in permeability values, flow velocities may differ greatly throughout the medium. To avoid complicated interface conditions, the Brinkman model is often used for such flows [O. Iliev, R. Lazarov, and J. Willems, Multiscale Model. Simul., 9 (2011), pp. 1350--1372]. Instead of permeability variations and contrast being contained in the geometric media structure, this information is contained in a highly varying and high-contrast coefficient. In this work, we present two main contributions. First, we develop a novel homogenization procedure for the high-contrast Brinkman equations by constructing correctors and carefully estimating the residuals. Understanding the relationship between scales and contrast values is critical to obtaining useful estimates. Therefore, standard convergence-based homogenization techniques [G. A. Chechkin, A. L. Piatniski, and A. S. Shamev, Homogenization: Methods and Applications, Transl. Math. Monogr. 234, American Mathematical Society, Providence, RI, 2007, G. Allaire, SIAM J. Math. Anal., 23 (1992), pp. 1482--1518], although a powerful tool, are not applicable here. Our second point is that the Brinkman equations, in certain scaling regimes, are invariant under homogenization. Unlike in the case of Stokes-to-Darcy homogenization [D. Brown, P. Popov, and Y. Efendiev, GEM Int. J. Geomath., 2 (2011), pp. 281--305, E. Marusic-Paloka and A. Mikelic, Boll. Un. Mat. Ital. A (7), 10 (1996), pp. 661--671], the results presented here under certain velocity regimes yield a Brinkman-to-Brinkman upscaling that allows using a single software platform to compute on both microscales and macroscales. In this paper, we discuss the homogenized Brinkman equations. We derive auxiliary cell problems to build correctors and calculate effective coefficients for certain velocity regimes. Due to the boundary effects, we construct

  13. High-index-contrast subwavelength grating VCSEL

    DEFF Research Database (Denmark)

    Gilet, Philippe; Olivier, Nicolas; Grosse, Philippe

    2010-01-01

    In this article, we report our results on 980nm high-index-contrast subwavelength grating (HCG) VCSELs for optical interconnection applications. In our structure, a thin undoped HCG layer replaces a thick p-type Bragg mirror. The HCG mirror can feasibly achieve polarization-selective reflectivities...... close to 100%. The investigated structure consists of a HCG mirror with an underneath /4-thick oxide gap, four p-type GaAlAs/GaAs pairs for current spreading, three InGaAs/GaAs quantum wells, and an n-type GaAlAs/GaAs Bragg mirror. The HCG structure was defined by e-beam lithography and dry etching....... The current oxide aperture and the oxide gap underneath the HCG were simultaneously formed by the selective wet oxidation process. Compared to air-gap high contrast grating mirrors demonstrated elsewhere, our grating mirrors are particular since they are supported by thinner /4 aluminium oxide layer, and thus...

  14. High contrast laser marking of alumina

    Energy Technology Data Exchange (ETDEWEB)

    Penide, J. [Applied Physics Department, University of Vigo, EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Quintero, F., E-mail: fquintero@uvigo.es [Applied Physics Department, University of Vigo, EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Riveiro, A. [Applied Physics Department, University of Vigo, EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Fernández, A. [Department of Engineering Design, University of Vigo, Escuela de Ingeniería Industrial, Campus Universitario, Vigo E-36310 (Spain); Val, J. del [Applied Physics Department, University of Vigo, EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain); Comesaña, R. [Materials Engineering, Applied Mechanics and Construction Department, University of Vigo, EEI, Lagoas-Marcosende, Vigo E-36310 (Spain); Lusquiños, F.; Pou, J. [Applied Physics Department, University of Vigo, EEI, Lagoas-Marcosende, 9, Vigo 36310 (Spain)

    2015-05-01

    Highlights: • Laser marking of alumina using near infrared (NIR) lasers was experimentally analyzed. • Color change produced by NIR lasers is due to thermally induced oxygen vacancies. • Laser marking results obtained using NIR lasers and green laser are compared. • High contrast marks on alumina were achieved. - Abstract: Alumina serves as raw material for a broad range of advanced ceramic products. These elements should usually be identified by some characters or symbols printed directly on them. In this sense, laser marking is an efficient, reliable and widely implemented process in industry. However, laser marking of alumina still leads to poor results since the process is not able to produce a dark mark, yielding bad contrast. In this paper, we present an experimental study on the process of marking alumina by three different lasers working in two wavelengths: 1064 nm (Near-infrared) and 532 nm (visible, green radiation). A colorimetric analysis has been carried out in order to compare the resulting marks and its contrast. The most suitable laser operating conditions were also defined and are reported here. Moreover, the physical process of marking by NIR lasers is discussed in detail. Field Emission Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy were also employed to analyze the results. Finally, we propose an explanation for the differences of the coloration induced under different atmospheres and laser parameters. We concluded that the atmosphere is the key parameter, being the inert one the best choice to produce the darkest marks.

  15. Steady-State Contrast Response Functions Provide a Sensitive and Objective Index of Amblyopic Deficits

    Science.gov (United States)

    Baker, Daniel H.; Simard, Mathieu; Saint-Amour, Dave; Hess, Robert F.

    2015-01-01

    Purpose. Visual deficits in amblyopia are neural in origin, yet are difficult to characterize with functional magnetic resonance imagery (fMRI). Our aim was to develop an objective electroencephalography (EEG) paradigm that can be used to provide a clinically useful index of amblyopic deficits. Methods. We used steady-state visual evoked potentials (SSVEPs) to measure full contrast response functions in both amblyopic (n = 10, strabismic or mixed amblyopia, mean age: 44 years) and control (n = 5, mean age: 31 years) observers, both with and without a dichoptic mask. Results. At the highest target contrast, the ratio of amplitudes across the weaker and stronger eyes was highly correlated (r = 0.76) with the acuity ratio between the eyes. We also found that the contrast response function in the amblyopic eye had both a greatly reduced amplitude and a shallower slope, but that surprisingly dichoptic masking was weaker than in controls. The results were compared with the predictions of a computational model of amblyopia and suggest a modification to the model whereby excitatory (but not suppressive) signals are attenuated in the amblyopic eye. Conclusions. We suggest that SSVEPs offer a sensitive and objective measure of the ocular imbalance in amblyopia and could be used to assess the efficacy of amblyopia therapies currently under development. PMID:25634977

  16. High-contrast imaging with METIS

    Science.gov (United States)

    Kenworthy, Matthew A.; Absil, Olivier; Agócs, Tibor; Pantin, Eric; Quanz, Sascha; Stuik, Remko; Snik, Frans; Brandl, Bernhard

    2016-08-01

    The Mid-infrared E-ELT Imager and Spectrograph (METIS) for the European Extremely Large Telescope (E-ELT) consists of diffraction-limited imagers that cover 3 to 14 microns with medium resolution (R 5000) long slit spectroscopy, and an integral field spectrograph for high spectral resolution spectroscopy (R 100,000) over the L and M bands. One of the science cases that METIS addresses is the characterization of faint circumstellar material and exoplanet companions through imaging and spectroscopy. We present our approach for high contrast imaging with METIS, covering diffraction suppression with coronagraphs, the removal of slowly changing optical aberrations with focal plane wavefront sensing, interferometric imaging with sparse aperture masks, and observing strategies for both the imagers and IFU image slicers.

  17. Biphasic contrast medium injection in cardiac CT: moderate versus high concentration contrast material at identical iodine flux and iodine dose.

    NARCIS (Netherlands)

    Rutten, A.; Meijs, M.F.; Vos, A.M.C.; Seidensticker, P.R.; Prokop, M.

    2010-01-01

    OBJECTIVE: To prospectively investigate the influence of contrast material concentration on enhancement in cardiac CT by using a biphasic single-injection protocol. METHODS: Sixty-four-row multidetector cardiac CT angiography was performed in 159 patients randomised to a moderate or high contrast me

  18. Photonic crystal slabs for surface contrast enhancement in microscopy of transparent objects.

    Science.gov (United States)

    Nazirizadeh, Yousef; Becker, Tim; Reverey, Julia; Selhuber-Unkel, Christine; Rapoport, Daniel H; Lemmer, Uli; Gerken, Martina

    2012-06-18

    In optical microscopy the contrast of transparent objects achieved with conventional methods is often not satisfactory, for example for the automated recognition of cells. In this paper we present a nano-optical label-free approach for contrast enhancement based on photonic crystal slabs (PCS) as the specimen holder. Quasi-guided modes inside these structures cause an intrinsic color of the PCS, which strongly depends on the wavelength and the quality factor of the optical mode. Objects on the surface of the PCS experience a significant color and intensity contrast enhancement, as they change properties of the optical modes.

  19. Printed Multicolor High-Contrast Electrochromic Devices.

    Science.gov (United States)

    Chen, Bo-Han; Kao, Sheng-Yuan; Hu, Chih-Wei; Higuchi, Masayoshi; Ho, Kuo-Chuan; Liao, Ying-Chih

    2015-11-18

    In this study, electrochemical responses of inkjet-printed multicolored electrochromic devices (ECD) were studied to evaluate the feasibility of presenting multiple colors in one ECD. Metallo-supramolecular polymers (MEPE) solutions with two primary colors were inkjet-printed on flexible electrodes. By digitally controlling print dosages of each species, the colors of the printed EC thin film patterns can be adjusted directly without premixing or synthesizing new materials. The printed EC thin films were then laminated with a solid transparent thin film electrolyte and a transparent conductive thin film to form an ECD. After applying a dc voltage, the printed ECDs exhibited great contrast with a transmittance change (ΔT) of 40.1% and a high coloration efficiency of 445 cm(2) C(-1) within a short darkening time of 2 s. The flexible ECDs also showed the same darkening time of 2 s and still had a high ΔT of 30.1% under bending condition. This study demonstrated the feasibility to fabricate display devices with different color setups by an all-solution process and can be further extended to other types of displays.

  20. Preexposure to Objects That Contrast in Familiarity Improves Young Children's Lexical Knowledge Judgment

    Science.gov (United States)

    Hartin, Travis L.; Stevenson, Colleen M.; Merriman, William E.

    2016-01-01

    The ability to judge the limits of one's own knowledge may play an important role in knowledge acquisition. The current study tested the prediction that preschoolers would judge the limits of their lexical knowledge more accurately if they were first exposed to a few objects of contrasting familiarity. Such preexposure was hypothesized to increase…

  1. The ZIMPOL high contrast imaging polarimeter for SPHERE: polarimetric high contrast commissioning results

    Science.gov (United States)

    Roelfsema, Ronald; Bazzon, Andreas; Schmid, Hans Martin; Pragt, Johan; Govaert, Alain; Gisler, Daniel; Dominik, Carsten; Baruffolo, Andrea; Beuzit, Jean-Luc; Costille, Anne; Dohlen, Kjetil; Downing, Mark; Elswijk, Eddy; de Haan, Menno; Hubin, Norbert; Kasper, Markus; Keller, Christoph; Lizon, Jean-Louis; Mouillet, David; Pavlov, Alexey; Puget, Pascal; Salasnich, Bernardo; Sauvage, Jean-Francois; Wildi, Francois

    2016-07-01

    SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is a second generation VLT instrument aimed at the direct detection of exo-planets. It has received its first light in May 2014. ZIMPOL (Zurich Imaging Polarimeter) is the imaging polarimeter subsystem of the SPHERE instrument. It's capable of both high accuracy and high sensitivity polarimetry but can also be used as a classical imager. It is located behind an extreme AO system and a stellar coronagraph. ZIMPOL operates at visible wavelengths which is best suited to detect the very faint reflected and hence polarized visible light from extra solar planets. During the SPHERE fourth commissioning period (October 2014) we have made deep coronagraphic observations of the bright star alpha Gru (mR = 1.75) to assess the high contrast polarimetric performance of SPHERE-ZIMPOL. We have integrated on the target for a total time of about 45 minutes during the meridian transit in the Very Broad Band filter (600 - 900 nm) with a classical Lyot coronagraph with 3 λ/D radius focal mask. We reduce the data by a combination of Polarized Background subtraction, Polarimetric Differential Imaging (PDI) and Angular Differential Imaging (ADI). We reach contrasts of 10-6 and 10-7 at a radial distances of respectively 7 and 14 lambda/D from the PSF core. At these radial distances we are respectively a factor of 10 and 2 above the photon noise limit. We discuss our results by considering the temporal and spatial speckle behavior close to the PSF core in combination with low order polarimetric aberrations.

  2. CONTRAST

    DEFF Research Database (Denmark)

    Kristensen, Thomas Krogsgaard

    2007-01-01

    Dette er en afrapportering fra den årlige CONTRAST workshop, der i 2007 blev afholdt i Yaoundé, Cameroon.......Dette er en afrapportering fra den årlige CONTRAST workshop, der i 2007 blev afholdt i Yaoundé, Cameroon....

  3. Generation And Measurement Of High Contrast Ultrashort Intense Laser Pulses

    CERN Document Server

    Konoplev, O A

    2000-01-01

    In this thesis, the generation and measurement of high contrast, intense, ultrashort pulses have been studied. Various factors affecting the contrast and pulse shape of ultrashort light pulses from a chirped pulse amplification (CPA) laser system are identified. The level of contrast resulting from influence of these factors is estimated. Methods for improving and controlling the pulse shape and increasing the contrast are discussed. Ultrahigh contrast, 1-ps pulses were generated from a CPA system with no temporal structure up to eleven orders of magnitude. This is eight orders of magnitude higher contrast than the original pulse. This contrast boost was achieved using two techniques. One is the optical pulse cleaning based on the nonlinear birefringence of the chirping fiber and applied to the pulses before amplification. The other is the fast saturable absorber. The fast saturable absorber was placed after amplification and compression of the pulse. The measurements of high-contrast, ultrashort pulse with h...

  4. Evaluation of the dark-medium objective lens in counting asbestos fibers by phase-contrast microscopy.

    Science.gov (United States)

    Lee, Eun Gyung; Nelson, John H; Kashon, Michael L; Harper, Martin

    2015-06-01

    A Japanese round-robin study revealed that analysts who used a dark-medium (DM) objective lens reported higher fiber counts from American Industrial Hygiene Association (AIHA) Proficiency Analytical Testing (PAT) chrysotile samples than those using a standard objective lens, but the cause of this difference was not investigated at that time. The purpose of this study is to determine any major source of this difference by performing two sets of round-robin studies. For the first round-robin study, 15 AIHA PAT samples (five each of chrysotile and amosite generated by water-suspended method, and five chrysotile generated by aerosolization method) were prepared with relocatable cover slips and examined by nine laboratories. A second round-robin study was then performed with six chrysotile field sample slides by six out of nine laboratories who participated in the first round-robin study. In addition, two phase-shift test slides to check analysts' visibility and an eight-form diatom test plate to compare resolution between the two objectives were examined. For the AIHA PAT chrysotile reference slides, use of the DM objective resulted in consistently higher fiber counts (1.45 times for all data) than the standard objective (P-value counts between the two objectives were not significantly different. No statistically significant differences were observed in the visibility of blocks of the test slides between the two objectives. Also, the DM and standard objectives showed no pattern of differences in viewing the fine lines and/or dots of each species images on the eight-form diatom test plate. Among various potential factors that might affect the analysts' performance of fiber counts, this study supports the greater contrast caused by the different phase plate absorptions as the main cause of high counts for the AIHA PAT chrysotile slides using the DM objective. The comparison of fiber count ratios (DM/standard) between the AIHA PAT chrysotile samples and chrysotile field

  5. Reduced-Contrast Approximations for High-Contrast Multiscale Flow Problems

    KAUST Repository

    Chung, Eric T.

    2010-01-01

    In this paper, we study multiscale methods for high-contrast elliptic problems where the media properties change dramatically. The disparity in the media properties (also referred to as high contrast in the paper) introduces an additional scale that needs to be resolved in multiscale simulations. First, we present a construction that uses an integral equation to represent the highcontrast component of the solution. This representation involves solving an integral equation along the interface where the coefficients are discontinuous. The integral representation suggests some multiscale approaches that are discussed in the paper. One of these approaches entails the use of interface functions in addition to multiscale basis functions representing the heterogeneities without high contrast. In this paper, we propose an approximation for the solution of the integral equation using the interface problems in reduced-contrast media. Reduced-contrast media are obtained by lowering the variance of the coefficients. We also propose a similar approach for the solution of the elliptic equation without using an integral representation. This approach is simpler to use in the computations because it does not involve setting up integral equations. The main idea of this approach is to approximate the solution of the high-contrast problem by the solutions of the problems formulated in reduced-contrast media. In this approach, a rapidly converging sequence is proposed where only problems with lower contrast are solved. It was shown that this sequence possesses the convergence rate that is inversely proportional to the reduced contrast. This approximation allows choosing the reduced-contrast problem based on the coarse-mesh size as discussed in this paper. We present a simple application of this approach to homogenization of elliptic equations with high-contrast coefficients. The presented approaches are limited to the cases where there are sharp changes in the contrast (i.e., the high

  6. High Contrast Electroluminescent Numeric Readout Device.

    Science.gov (United States)

    1980-08-01

    approach was available only in separate chips one having npn and the other pnp devices. The first phase of the DMOS transistor development should be...proposed by the vendor. Further samples also failed to meet requirements and, therefore, a discrete transistor driver array was used in prototype...completed by September, high-voltage transistor arrays will be available by December, 1979. 3.2.1 Test Chip Layout Figure 5 shows the layout of the test

  7. In-line phase-contrast imaging for strong absorbing objects

    Energy Technology Data Exchange (ETDEWEB)

    De Caro, Liberato; Giannini, Cinzia [Istituto di Cristallografia, Consiglio Nazionale delle Ricerche (IC-CNR), via Amendola 122/O, I-70125 Bari (Italy); Cedola, Alessia; Bukreeva, Inna; Lagomarsino, Stefano [Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche (IFN-CNR), via Cinto Romano 42, I-00156 Roma (Italy)

    2008-11-21

    Phase-contrast imaging is one of the most important emerging x-ray imaging techniques. In this work we analyse, from a theoretical point of view, the in-line phase-contrast image formation under general assumptions. The approach is based on wave-optical theory (Fresnel/Kirchoff diffraction integrals) and on the formalism of the mutual coherence function for the evolution of the coherence wavefield properties. Our theoretical model can be applied to phase-contrast imaging realized both by using highly coherent synchrotron radiation and micro-focus x-ray laboratory sources. Thus, the model is suitable for widespread applications, ranging from material science to medical imaging of human body parts. However, it cannot be applied to polychromatic sources, although the validity of the model does not require particularly demanding characteristics of monochromaticity. In addition, for moderate phase gradients, a useful analytical formula of the phase-contrast visibility is derived, based on the a priori knowledge of source size and distance, pixel detector size, defocus distance, material/tissue dielectric susceptibility and characteristic scales of transversal and longitudinal non-uniformities of the material/tissue dielectric susceptibility. Comparisons both with experimental results published by other authors and with simulations based on a Fourier optics approach have been reported, to confirm the validity of the proposed analytical formula.

  8. Asymptotic expansions for high-contrast linear elasticity

    KAUST Repository

    Poveda, Leonardo A.

    2015-03-01

    We study linear elasticity problems with high contrast in the coefficients using asymptotic limits recently introduced. We derive an asymptotic expansion to solve heterogeneous elasticity problems in terms of the contrast in the coefficients. We study the convergence of the expansion in the H1 norm. © 2015 Elsevier B.V.

  9. High Contrast Vacuum Nuller Testbed (VNT) Contrast, Performance and Null Control

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Petrone, Peter; Mallik, Udayan; Madison, Timothy; Bolcar, Matthew R.

    2012-01-01

    Herein we report on our Visible Nulling Coronagraph high-contrast result of 109 contrast averaged over a focal planeregion extending from 14 D with the Vacuum Nuller Testbed (VNT) in a vibration isolated vacuum chamber. TheVNC is a hybrid interferometriccoronagraphic approach for exoplanet science. It operates with high Lyot stopefficiency for filled, segmented and sparse or diluted-aperture telescopes, thereby spanning the range of potential futureNASA flight telescopes. NASAGoddard Space Flight Center (GSFC) has a well-established effort to develop the VNCand its technologies, and has developed an incremental sequence of VNC testbeds to advance this approach and itsenabling technologies. These testbeds have enabled advancement of high-contrast, visible light, nulling interferometry tounprecedented levels. The VNC is based on a modified Mach-Zehnder nulling interferometer, with a W configurationto accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters.We give an overview of the VNT and discuss the high-contrast laboratory results, the optical configuration, criticaltechnologies and null sensing and control.

  10. Asymptotic expansions for high-contrast elliptic equations

    KAUST Repository

    Calo, Victor M.

    2014-03-01

    In this paper, we present a high-order expansion for elliptic equations in high-contrast media. The background conductivity is taken to be one and we assume the medium contains high (or low) conductivity inclusions. We derive an asymptotic expansion with respect to the contrast and provide a procedure to compute the terms in the expansion. The computation of the expansion does not depend on the contrast which is important for simulations. The latter allows avoiding increased mesh resolution around high conductivity features. This work is partly motivated by our earlier work in [Domain decomposition preconditioners for multiscale flows in high-contrast media, Multiscale Model Simul. 8 (2010) 1461-1483] where we design efficient numerical procedures for solving high-contrast problems. These multiscale approaches require local solutions and our proposed high-order expansion can be used to approximate these local solutions inexpensively. In the case of a large-number of inclusions, the proposed analysis can help to design localization techniques for computing the terms in the expansion. In the paper, we present a rigorous analysis of the proposed high-order expansion and estimate the remainder of it. We consider both high-and low-conductivity inclusions. © 2014 World Scientific Publishing Company.

  11. Transmission grating stretcher for contrast enhancement of high power lasers.

    Science.gov (United States)

    Tang, Yunxin; Hooker, Chris; Chekhlov, Oleg; Hawkes, Steve; Collier, John; Rajeev, P P

    2014-12-01

    We propose, for the first time, a transmission grating stretcher for high power lasers and demonstrate its superiority over conventional, reflective gold grating stretchers in terms of pulse temporal quality. We show that, compared to a conventional stretcher with the same stretching factor, the transmission-grating based stretcher yields more than an order of magnitude improvement in the contrast pedestal. We have also quantitatively characterized the roughness of the grating surfaces and estimated its impact on the contrast pedestal.

  12. Prediction of object detection, recognition, and identification [DRI] ranges at color scene images based on quantifying human color contrast perception

    Science.gov (United States)

    Pinsky, Ephi; Levin, Ilia; Yaron, Ofer

    2016-10-01

    We propose a novel approach to predict, for specified color imaging system and for objects with known characteristics, their detection, recognition, identification (DRI) ranges in a colored dynamic scene, based on quantifying the human color contrast perception. The method refers to the well established L*a*b*, 3D color space. The nonlinear relations of this space are intended to mimic the nonlinear response of the human eye. The metrics of L*a*b* color space is such that the Euclidian distance between any two colors in this space is approximately proportional to the color contrast as perceived by the human eye/brain. The result of this metrics leads to the outcome that color contrast of any two points is always greater (or equal) than their equivalent grey scale contrast. This meets our sense that looking on a colored image, contrast is superior to the gray scale contrast of the same image. Yet, color loss by scattering at very long ranges should be considered as well. The color contrast derived from the distance between the colored object pixels and to the nearby colored background pixels, as derived from the L*a*b* color space metrics, is expressed in terms of gray scale contrast. This contrast replaces the original standard gray scale contrast component of that image. As expected, the resulted DRI ranges are, in most cases, larger than those predicted by the standard gray scale image. Upon further elaboration and validation of this method, it may be combined with the next versions of the well accepted TRM codes for DRI predictions. Consistent prediction of DRI ranges implies a careful evaluation of the object and background color contrast reduction along the range. Clearly, additional processing for reconstructing the objects and background true colors and hence the color contrast along the range, will further increase the DRI ranges.

  13. Phase contrast imaging with coherent high energy X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Snigireva, I. [ESRF, Grenoble (France)

    1997-02-01

    X-ray imaging concern high energy domain (>6 keV) like a contact radiography, projection microscopy and tomography is used for many years to discern the features of the internal structure non destructively in material science, medicine and biology. In so doing the main contrast formation is absorption that makes some limitations for imaging of the light density materials and what is more the resolution of these techniques is not better than 10-100 {mu}m. It was turned out that there is now way in which to overcome 1{mu}m or even sub-{mu}m resolution limit except phase contrast imaging. It is well known in optics that the phase contrast is realised when interference between reference wave front and transmitted through the sample take place. Examples of this imaging are: phase contrast microscopy suggested by Zernike and Gabor (in-line) holography. Both of this techniques: phase contrast x-ray microscopy and holography are successfully progressing now in soft x-ray region. For imaging in the hard X-rays to enhance the contrast and to be able to resolve phase variations across the beam the high degree of the time and more importantly spatial coherence is needed. Because of this it was reasonable that the perfect crystal optics was involved like Bonse-Hart interferometry, double-crystal and even triple-crystal set-up using Laue and Bragg geometry with asymmetrically cut crystals.

  14. Image quality and high contrast improvements on VLT/NACO

    CERN Document Server

    Girard, Julien H V; Mawet, Dimitri; Kasper, Markus; Zins, Gérard; Neichel, Benoît; Kolb, Johann; Christiaens, Valentin; Tourneboeuf, Martin; 10.1117/12.925660

    2012-01-01

    NACO is the famous and versatile diffraction limited NIR imager and spectrograph with which ESO celebrated 10 years of Adaptive Optics at the VLT. Since two years a substantial effort has been put in to understanding and fixing issues that directly affect the image quality and the high contrast performances of the instrument. Experiments to compensate the non-common-path aberrations and recover the highest possible Strehl ratios have been carried out successfully and a plan is hereafter described to perform such measurements regularly. The drift associated to pupil tracking since 2007 was fixed in October 2011. NACO is therefore even better suited for high contrast imaging and can be used with coronagraphic masks in the image plane. Some contrast measurements are shown and discussed. The work accomplished on NACO will serve as reference for the next generation instruments on the VLT, especially those working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, possibly ...

  15. High Contrast Imaging Testbed for the Terrestrial Planet Finder Coronagraph

    Science.gov (United States)

    Lowmman, Andrew E.; Trauger, John T.; Gordon, Brian; Green, Joseph J.; Moody, Dwight; Niessner, Albert F.; Shi, Fang

    2004-01-01

    The Terrestrial Planet Finder (TPF) mission is planning to launch a visible coronagraphic space telescope in 2014. To achieve TPF science goals, the coronagraph must have extreme levels of wavefront correction (less than 1 Angstrom rms over controllable spatial frequencies) and stability to get the necessary suppression of diffracted starlight (approximately l0(exp -10)) contrast at an angular separation approximately 4 (lamda)/D). TPF Coronagraph's primary platform for experimentation is the High Contrast Imaging Testbed, which will provide laboratory validation of key technologies as well as demonstration of a flight-traceable approach to implementation. Precision wavefront control in the testbed is provided by a high actuator density deformable mirror. Diffracted light control is achieved through use of occulting or apodizing masks and stops. Contrast measurements will establish the technical feasibility of TPF requirements, while model and error budget validation will demonstrate implementation viability. This paper describes the current testbed design, development approach, and recent experimental results.

  16. T1 and susceptibility contrast at high fields

    Science.gov (United States)

    Neelavalli, Jaladhar

    Clinical imaging at high magnetic field strengths (≥ 3Tesla) is sought after primarily due to the increased signal strength available at these fields. This increased SNR can be used to perform: (a) high resolution imaging in the same time as at lower field strengths; (b) the same resolution imaging with much faster acquisition; and (c) functional MR imaging (fMRI), dynamic perfusion and diffusion imaging with increased sensitivity. However they are also associated with increased power deposition (SAR) due to increase in imaging frequency and longer T1 relaxation times. Longer T1s mean longer imaging times for generating good T1 contrast images. On the other hand for faster imaging, at high fields fast spin echo or magnetization prepared sequences are conventionally proposed which are, however, associated with high SAR values. Imaging with low SAR is more and more important as we move towards high fields and particularly for patients with metallic implants like pacemakers or deep brain stimulator. The SAR limit acceptable for these patients is much less than the limit acceptable for normal subjects. A new method is proposed for imaging at high fields with good contrast with simultaneous reduction in power deposition. Further, T1 based contrast optimization problem in FLASH imaging is considered for tissues with different T1s but same spin densities. The solution providing optimal imaging parameters is simplified for quick and easy computation in a clinical setting. The efficacy of the simplification is evaluated and practical limits under which the simplification can be applied are worked out. The phase difference due to variation in magnetic susceptibility property among biological tissues is another unique source of contrast which is different from the conventional T1, T2 and T2* contrast. This susceptibility based phase contrast has become more and more important at high fields, partly due to contrast generation issues due to longer T 1s and shorter T2s and

  17. Polarization-Independent Wideband High-Index-Contrast Grating Mirror

    DEFF Research Database (Denmark)

    Bekele, Dagmawi Alemayehu; Park, Gyeong Cheol; Malureanu, Radu

    2015-01-01

    Island-type two-dimensional high-index-contrast grating mirror based on a standard silicon-on-insulator wafer have been experimentally demonstrated. The measured spectra shows a bandwidth of ∼192 nm with a reflectivity over 99% as well as polarization independence. Numerical simulations show...... that the designed mirror has large tolerance to fabrication errors....

  18. Characterisation of a single photon counting pixel system for imaging of low-contrast objects

    CERN Document Server

    Mikulec, B; Dipasquale, G; Schwarz, C; Watt, J

    2001-01-01

    In the framework of the Medipix collaboration the PCC, a single photon counting pixel chip, has been developed with the aim of improving the contrast resolution in medical imaging applications. The PCC consists of a matrix of 64x64 square pixels with 170 mm side length, each pixel comprising a 15 bit counter and a pulse height discriminator. The chip has been bump bonded to equally segmented 200 mm thick SI-LEC GaAs detectors showing a very high absorption energy for X-rays used in diagnostics. An absolute calibration of the system with a radioactive source and a synchrotron beam are described resulting in the value of the test input capacitance of ~24.7 fF. Using this value a full characterisation of the system from electrical measurements is presented. The entire system can reach a minimum threshold of ~2100 e- with ~250e- rms noise. One of the characteristics of the PCC is the possibility to adjust the thresholds of all pixels on a pixel-by-pixel basis with 3-bit precision. The threshold distribution after...

  19. Object localization within turbid slab media using time-resolved transillumination contrast functions: a finite element approach

    Science.gov (United States)

    Piron, V.; L'Huillier, J. P.; Mansouri, C.

    2007-07-01

    In the last few years, the propagation of diffuse photons in scattering media has become an important field of interest. This is mainly due to the possibility offered by the low absorption of light in the range 700 to 900nm. Indeed, this property leads to a potential deep penetration. But a non negligible limitation appears: the scattering processes strongly reduce both the contrast and the resolution. In this paper, the time-dependent light propagation in highly scattering media containing an inclusion is solved by means of a finite element method, tacking into account Robin type air-tissue boundary conditions. This study is devoted to the depth localization of a tumor enclosed into a breast-like slab. The tissue is modeled by a rectangular meshed domain that mimics a breast compressed between two transparent plates. Cartesian coordinates are used in order to solve the time-dependent diffusion approximation. A short laser pulse of 1ps is considered. The transillumination technique is able to laterally detect the object when the source and detector are moved together on the same axis. In order to perform the localization of the inclusion in this study, the optical properties of the object were varied. Knowing the lateral position of the inclusion, we derive interesting temporal contrast functions based on the mean time of flight of photons. These functions allow to localize in depth the inclusion under the assumption that the object is very diffusing. To conclude, our study demonstrates the possibility to detect laterally and axially a tumor-like inclusion enclosed in breast-like tissues.

  20. The V-SHARK high contrast imager at LBT

    Science.gov (United States)

    Pedichini, F.; Ambrosino, F.; Centrone, M.; Farinato, J.; Li Causi, G.; Pinna, E.; Puglisi, A.; Stangalini, M.; Testa, V.

    2016-08-01

    In the framework of the SHARK project the visible channel is a novel instrument synergic to the NIR channel and exploiting the performances of the LBT XAO at visible wavelengths. The status of the project is presented together with the design study of this innovative instrument optimized for high contrast imaging by means of high frame rate. Its expected results will be presented comparing the simulations with the real data of the "Forerunner" experiment taken at 630nm.

  1. High-contrast self-imaging with ordered optical elements

    CERN Document Server

    Naqavi, Ali; Rossi, Markus

    2016-01-01

    Creating arbitrary light patterns finds applications in various domains including lithography, beam shaping, metrology, sensing and imaging. We study the formation of high-contrast light patterns that are obtained by transmission through an ordered optical element based on self-imaging.By applying the phase-space method, we explain phenomena such as the Talbot and the angular Talbot effects. We show that the image contrast is maximum when the source is either a plane wave or a point source, and it has a minimum for a source with finite spatial extent. We compare these regimes and address some of their fundamental differences. Specifically, we prove that increasing the source divergence reduces the contrast for the plane wave illumination but increases it for the point source. Also, we show that to achieve high contrast with a point source, tuning the source size and its distance to the element is crucial.We furthermore indicate and explore the possibility of realizing highly complex light patterns by using a ...

  2. Gd-HOPO Based High Relaxivity MRI Contrast Agents

    Energy Technology Data Exchange (ETDEWEB)

    Datta, Ankona; Raymond, Kenneth

    2008-11-06

    Tris-bidentate HOPO-based ligands developed in our laboratory were designed to complement the coordination preferences of Gd{sup 3+}, especially its oxophilicity. The HOPO ligands provide a hexadentate coordination environment for Gd{sup 3+} in which all he donor atoms are oxygen. Because Gd{sup 3+} favors eight or nine coordination, this design provides two to three open sites for inner-sphere water molecules. These water molecules rapidly exchange with bulk solution, hence affecting the relaxation rates of bulk water olecules. The parameters affecting the efficiency of these contrast agents have been tuned to improve contrast while still maintaining a high thermodynamic stability for Gd{sup 3+} binding. The Gd- HOPO-based contrast agents surpass current commercially available agents ecause of a higher number of inner-sphere water molecules, rapid exchange of inner-sphere water molecules via an associative mechanism, and a long electronic relaxation time. The contrast enhancement provided by these agents is at least twice that of commercial contrast gents, which are based on polyaminocarboxylate ligands.

  3. High Energy Emissions from Young Stellar Objects

    Indian Academy of Sciences (India)

    A. C. Das; Ashok Ambastha

    2012-03-01

    X-ray emissions from Young Stellar Objects (YSO) are detected by many X-ray missions that are providing important information about their properties. However, their emission processes are not fully understood. In this research note, we propose a model for the generation of emissions from a YSO on the basis of a simple interaction between the YSO and its surrounding circumstellar accretion disc containing neutral gas and charged dust. It is assumed that the YSO has a weak dipole type magnetic field and its field lines are threaded into the circumstellar disc. Considering the motion of ions and charged dust particles in the presence of neutral gas, we show that the sheared dust-neutral gas velocities can lead to a current along the direction of ambient magnetic field. Magnitude of this current can become large and is capable of generating an electric field along the magnetic field lines. It is shown how the particles can gain energy up to MeV range and above, which can produce high-energy radiations from the YSO.

  4. Optimal Phase Masks for High Contrast Imaging Applications

    Science.gov (United States)

    Ruane, Garreth J.

    2016-05-01

    Phase-only optical elements can provide a number of important functions for high-contrast imaging. This thesis presents analytical and numerical optical design methods for accomplishing specific tasks, the most significant of which is the precise suppression of light from a distant point source. Instruments designed for this purpose are known as coronagraphs. Here, advanced coronagraph designs are presented that offer improved theoretical performance in comparison to the current state-of-the-art. Applications of these systems include the direct imaging and characterization of exoplanets and circumstellar disks with high sensitivity. Several new coronagraph designs are introduced and, in some cases, experimental support is provided. In addition, two novel high-contrast imaging applications are discussed: the measurement of sub-resolution information using coronagraphic optics and the protection of sensors from laser damage. The former is based on experimental measurements of the sensitivity of a coronagraph to source displacement. The latter discussion presents the current state of ongoing theoretical work. Beyond the mentioned applications, the main outcome of this thesis is a generalized theory for the design of optical systems with one of more phase masks that provide precise control of radiation over a large dynamic range, which is relevant in various high-contrast imaging scenarios. The optimal phase masks depend on the necessary tasks, the maximum number of optics, and application specific performance measures. The challenges and future prospects of this work are discussed in detail.

  5. 1060-nm Tunable Monolithic High Index Contrast Subwavelength Grating VCSEL

    DEFF Research Database (Denmark)

    Ansbæk, Thor; Chung, Il-Sug; Semenova, Elizaveta

    2013-01-01

    We present the first tunable vertical-cavity surface-emitting laser (VCSEL) where the top distributed Bragg reflector has been completely substituted by an air-cladded high-index-contrast subwavelength grating (HCG) mirror. In this way, an extended cavity design can be realized by reducing...... the reflection at the semiconductor #x2013;air interface using an anti-reflective coating (ARC). We demonstrate how the ARC can be integrated in a monolithic structure by oxidizing AlGaAs with high Al-content. The HCG VCSEL has the potential to achieve polarization stable single-mode output with high tuning...

  6. Modeling the subjective quality of highly contrasted videos displayed on LCD with local backlight dimming.

    Science.gov (United States)

    Mantel, Claire; Bech, Søren; Korhonen, Jari; Forchhammer, Søren; Pedersen, Jesper Melgaard

    2015-02-01

    Local backlight dimming is a technology aiming at both saving energy and improving visual quality on television sets. As the rendition of the image is specified locally, the numerical signal corresponding to the displayed image needs to be computed through a model of the display. This simulated signal can then be used as input to objective quality metrics. The focus of this paper is on determining which characteristics of locally backlit displays influence quality assessment. A subjective experiment assessing the quality of highly contrasted videos displayed with various local backlight-dimming algorithms is set up. Subjective results are then compared with both objective measures and objective quality metrics using different display models. The first analysis indicates that the most significant objective features are temporal variations, power consumption (probably representing leakage), and a contrast measure. The second analysis shows that modeling of leakage is necessary for objective quality assessment of sequences displayed with local backlight dimming.

  7. Phase-contrast imaging of a soft biological object using X-pinch as X-ray source

    Science.gov (United States)

    Liu, R.; Wang, X. X.; Zou, X. B.; Zeng, N. G.; He, L. Y.

    2008-07-01

    The X-ray emission from an X-pinch was measured with diamond photoconducting detectors and a pinhole camera, and the results show that the X-ray source of the X-pinch is extremely small in size and high in brightness. As such, the X-pinch could be considered as an X-ray point source having a high spatial coherence that is required by a simplified scheme of X-ray phase-contrast imaging. The X-pinch was used as X-ray source for the phase-contrast imaging of a weakly X-ray-absorbing mosquito and an image with high contrast was obtained.

  8. What has driven the evolution of multiple cone classes in visual systems: object contrast enhancement or light flicker elimination?

    Science.gov (United States)

    Sabbah, Shai; Hawryshyn, Craig W

    2013-07-04

    Two competing theories have been advanced to explain the evolution of multiple cone classes in vertebrate eyes. These two theories have important, but different, implications for our understanding of the design and tuning of vertebrate visual systems. The 'contrast theory' proposes that multiple cone classes evolved in shallow-water fish to maximize the visual contrast of objects against diverse backgrounds. The competing 'flicker theory' states that multiple cone classes evolved to eliminate the light flicker inherent in shallow-water environments through antagonistic neural interactions, thereby enhancing object detection. However, the selective pressures that have driven the evolution of multiple cone classes remain largely obscure. We show that two critical assumptions of the flicker theory are violated. We found that the amplitude and temporal frequency of flicker vary over the visible spectrum, precluding its cancellation by simple antagonistic interactions between the output signals of cones. Moreover, we found that the temporal frequency of flicker matches the frequency where sensitivity is maximal in a wide range of fish taxa, suggesting that the flicker may actually enhance the detection of objects. Finally, using modeling of the chromatic contrast between fish pattern and background under flickering illumination, we found that the spectral sensitivity of cones in a cichlid focal species is optimally tuned to maximize the visual contrast between fish pattern and background, instead of to produce a flicker-free visual signal. The violation of its two critical assumptions substantially undermines support for the flicker theory as originally formulated. While this alone does not support the contrast theory, comparison of the contrast and flicker theories revealed that the visual system of our focal species was tuned as predicted by the contrast theory rather than by the flicker theory (or by some combination of the two). Thus, these findings challenge key

  9. Angular Differential Imaging: a Powerful High-Contrast Imaging Technique

    Energy Technology Data Exchange (ETDEWEB)

    Marois, C; Lafreniere, D; Doyon, R; Macintosh, B; Nadeau, D

    2005-11-07

    Angular differential imaging is a high-contrast imaging technique that reduces speckle noise from quasi-static optical aberrations and facilitates the detection of faint nearby companions. A sequence of images is acquired with an altitude/azimuth telescope, the instrument rotator being turned off. This keeps the instrument and telescope optics aligned, stabilizes the instrumental PSF and allows the field of view to rotate with respect to the instrument. For each image, a reference PSF obtained from other images of the sequence is subtracted. All residual images are then rotated to align the field and are median combined. Observed performances are reported for Gemini Altair/NIRI data. Inside the speckle dominated region of the PSF, it is shown that quasi-static PSF noise can be reduced by a factor {approx}5 for each image subtraction. The combination of all residuals then provides an additional gain of the order of the square root of the total number of images acquired. To our knowledge, this is the first time an acquisition strategy and reduction pipeline designed for speckle attenuation and high contrast imaging is demonstrated to significantly get better detection limits with longer integration times at all angular separations. A PSF noise attenuation of 100 was achieved from 2-hour long sequences of images of Vega, reaching a 5-sigma contrast of 20 magnitudes for separations greater than 7''. This technique can be used with currently available instruments to search for {approx} 1 M{sub Jup} exoplanets with orbits of radii between 50 and 300 AU around nearby young stars. The possibility of combining the technique with other high-contrast imaging methods is briefly discussed.

  10. Nomarski serial time-encoded amplified microscopy for high-speed contrast-enhanced imaging of transparent media

    OpenAIRE

    Fard, Ali M.; Mahjoubfar, Ata; Goda, Keisuke; Gossett, Daniel R.; Di Carlo, Dino; Jalali, Bahram

    2011-01-01

    High-speed high-contrast imaging modalities that enable image acquisition of transparent media without the need for chemical staining are essential tools for a broad range of applications; from semiconductor process monitoring to blood screening. Here we introduce a method for contrast-enhanced imaging of unstained transparent objects that is capable of high-throughput imaging. This method combines the Nomarski phase contrast capability with the ultrahigh frame rate and shutter speed of seria...

  11. Visible light metasurfaces based on gallium nitride high contrast gratings

    Science.gov (United States)

    Wang, Zhenhai; He, Shumin; Liu, Qifa; Wang, Wei

    2016-05-01

    We propose visible-light metasurfaces (VLMs) capable of serving as lens and beam deflecting element based on gallium nitride (GaN) high contrast gratings (HCGs). By precisely manipulating the wavefront of the transmitted light, we theoretically demonstrate an HCG focusing lens with transmissivity of 86.3%, and a VLM with beam deflection angle of 6.09° and transmissivity as high as 91.4%. The proposed all-dielectric metasurfaces are promising for GaN-based visible light-emitting diodes (LEDs), which would be robust and versatile for controlling the output light propagation and polarization, as well as enhancing the extraction efficiency of the LEDs.

  12. High Contrast Imaging with the JWST NIRCAM Coronagraph

    Science.gov (United States)

    Green, Joseph J.; Beichman, Charles; Basinger, Scott A.; Horner, Scott; Meyer, Michael; Redding, David C.; Rieke, Marcia; Trauger, John T.

    2005-01-01

    Relative to ground-based telescopes, the James Webb Space Telescope (JWST) will have a substantial sensitivity advantage in the 2.2-5pm wavelength range where brown dwarfs and hot Jupiters are thought to have significant brightness enhancements. To facilitate high contrast imaging within this band, the Near-Infrared Camera (NIRCAM) will employ a Lyot coronagraph with an array of band-limited image-plane occulting spots. In this paper, we provide the science motivation for high contrast imaging with NIRCAM, comparing its expected performance to that of the Keck, Gemini and 30 m (TMT) telescopes equipped with Adaptive Optics systems of different capabilities. We then describe our design for the NIRCAM coronagraph that enables imaging over the entire sensitivity range of the instrument while providing significant operational flexibility. We describe the various design tradeoffs that were made in consideration of alignment and aberration sensitivities and present contrast performance in the presence of JWST's expected optical aberrations. Finally we show an example of a that can provide 10-5 companion sensitivity at sub-arcsecond separations.

  13. Alternative Contrast Mechanisms in High Field MR Microscopy.

    Science.gov (United States)

    Engelhardt, Robert Thomas

    1995-01-01

    In high-field MR Microscopy, the T_1 relaxation times may become long and converge while the T_2 relaxation times may become short and converge. As a result, much of the contrast is due solely to differences in spin density. The use of T_{1rho} as an alternative contrast parameter in high-field MR Microscopy has been explored here. To this end, MR Microscopy experiments have been performed using 2.0 and 9.4 Tesla Bruker MRI systems. Spectroscopy experiments at 9.4 Tesla were performed on several phantoms (5.75% agar gel, 1.0 mM MnCl_2, 7.3% and 20% gelatin). Imaging experiments were performed on two, 17.5 day old, perfusion fixed, mouse embryos, embedded in 7.3% gelatin to minimize drying and susceptibility differences. The relaxation times, T_1, T _2, and T_{1rho }, the signal to noise ratios (SNR) and contrast to noise ratios (CNR), have been measured for several types of tissue. The T_{1rho} relaxation times were measured at four locking field strengths, 0.7, 0.9, 1.3 and 1.7 G. T_1 and T_2 imaging experiments were performed using a conventional spin warp imaging sequence. T_{1rho } imaging experiments were performed using a presaturating spin locking pulse, followed by a conventional spin warp imaging sequence. Muscle, diencephalon, lung and liver were chosen for the relaxation time measurements as they offered both good tissue specificity and size. Both static and locking field dispersion of T _{1rho} were observed in the selected mouse embryo tissues. The observed T _{1rho} relaxation times were generally longer than the T_2 relaxation times, increased with locking field strength, and were consistently shorter at 9.4 Tesla than at 2.0 Tesla. The static field dispersion of T_ {1rho} and T_2 are both believed to be due, in part, to diffusion losses through susceptibility induced gradients. The losses are much smaller in the T_{1rho} images, and decrease as the locking pulse is increased. Finally, under certain circumstances, T_{1rho }-weighting could produce

  14. High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM

    CERN Document Server

    Labadie, L; Femenia, B; Villo, Isidro; Diaz-Sanchez, A; Oscoz, A; Lopez, R; Perez-Prieto, J; Perez-Garrido, A; Hildebrandt, S R; Bejar-Sanchez, V; Piqueras, J; Rodriguez, L F; 10.1117/12.857998

    2010-01-01

    In this paper, we present an original observational approach, which combines, for the first time, traditional speckle imaging with image post-processing to obtain in the optical domain diffraction-limited images with high contrast (1e-5) within 0.5 to 2 arcseconds around a bright star. The post-processing step is based on wavelet filtering an has analogy with edge enhancement and high-pass filtering. Our I-band on-sky results with the 2.5-m Nordic Telescope (NOT) and the lucky imaging instrument FASTCAM show that we are able to detect L-type brown dwarf companions around a solar-type star with a contrast DI~12 at 2" and with no use of any coronographic capability, which greatly simplifies the instrumental and hardware approach. This object has been detected from the ground in J and H bands so far only with AO-assisted 8-10 m class telescopes (Gemini, Keck), although more recently detected with small-class telescopes in the K band. Discussing the advantage and disadvantage of the optical regime for the detecti...

  15. The Leiden EXoplanet Instrument (LEXI): a high-contrast high-dispersion spectrograph

    Science.gov (United States)

    Haffert, S. Y.; Wilby, M. J.; Keller, C. U.; Snellen, I. A. G.

    2016-08-01

    The Leiden EXoplanet Instrument (LEXI) will be the first instrument designed for high-contrast, high-dispersion integral field spectroscopy at optical wavelengths. High-contrast imaging (HCI) and high-dispersion spectroscopy (HDS) techniques are used to reach contrasts of 10-7. LEXI will be a bench-mounted, high dispersion integral field spectrograph that will record spectra in a small area around the star with high spatial resolution and high dynamic range. A prototype is being setup to The Leiden EXoplanet Instrument (LEXI) will be the first instrument designed for high-contrast, high-dispersion integral field spectroscopy at optical wavelengths. High-contrast imaging (HCI) and high-dispersion spectroscopy (HDS) techniques are used to reach contrasts of 10-7. LEXI will be a bench-mounted, high dispersion integral field spectrograph that will record spectra in a small area around the star with high spatial resolution and high dynamic range. A prototype is being setup to test the combination of HCI+HDS and its first light is expected in 2016.

  16. High-energy x-ray grating-based phase-contrast radiography of human anatomy

    Science.gov (United States)

    Horn, Florian; Hauke, Christian; Lachner, Sebastian; Ludwig, Veronika; Pelzer, Georg; Rieger, Jens; Schuster, Max; Seifert, Maria; Wandner, Johannes; Wolf, Andreas; Michel, Thilo; Anton, Gisela

    2016-03-01

    X-ray grating-based phase-contrast Talbot-Lau interferometry is a promising imaging technology that has the potential to raise soft tissue contrast in comparison to conventional attenuation-based imaging. Additionally, it is sensitive to attenuation, refraction and scattering of the radiation and thus provides complementary and otherwise inaccessible information due to the dark-field image, which shows the sub-pixel size granularity of the measured object. Until recent progress the method has been mainly limited to photon energies below 40 keV. Scaling the method to photon energies that are sufficient to pass large and spacious objects represents a challenging task. This is caused by increasing demands regarding the fabrication process of the gratings and the broad spectra that come along with the use of polychromatic X-ray sources operated at high acceleration voltages. We designed a setup that is capable to reach high visibilities in the range from 50 to 120 kV. Therefore, spacious and dense parts of the human body with high attenuation can be measured, such as a human knee. The authors will show investigations on the resulting attenuation, differential phase-contrast and dark-field images. The images experimentally show that X-ray grating-based phase-contrast radiography is feasible with highly absorbing parts of the human body containing massive bones.

  17. Double high refractive-index contrast grating VCSEL

    Science.gov (United States)

    Gebski, Marcin; Dems, Maciej; Wasiak, Michał; Sarzała, Robert P.; Lott, J. A.; Czyszanowski, Tomasz

    2015-03-01

    Distributed Bragg reflectors (DBRs) are typically used as the highly reflecting mirrors of vertical-cavity surface-emitting lasers (VCSELs). In order to provide optical field confinement, oxide apertures are often incorporated in the process of the selective wet oxidation of high aluminum-content DBR layers. This technology has some potential drawbacks such as difficulty in controlling the uniformity of the oxide aperture diameters across a large-diameter (≥ 6 inch) production wafers, high DBR series resistance especially for small diameters below about 5 μm despite elaborate grading and doping schemes, free carrier absorption at longer emission wavelengths in the p-doped DBRs, reduced reliability for oxide apertures placed close to the quantum wells, and low thermal conductivity for transporting heat away from the active region. A prospective alternative mirror is a high refractive index contrast grating (HCG) monolithically integrated with the VCSEL cavity. Two HCG mirrors potentially offer a very compact and simplified VCSEL design although the problems of resistance, heat dissipation, and reliability are not completely solved. We present an analysis of a double HCG 980 nm GaAs-based ultra-thin VCSEL. We analyze the optical confinement of such a structure with a total optical thickness is ~1.0λ including the optical cavity and the two opposing and parallel HCG mirrors.

  18. After-effects of TFT-LCD display polarity and display colour on the detection of low-contrast objects.

    Science.gov (United States)

    Mayr, Susanne; Buchner, Axel

    2010-07-01

    Participants performed a word-non-word discrimination task within a car control display emulated on a thin film transistor liquid-crystal display (TFT-LCD). The task simulated an information read-out from a TFT-LCD-based instrument panel. Subsequently, participants performed a low-contrast object detection task that simulated the detection of objects during night-time driving. In experiment 1, words/non-words were presented black-on-white (positive polarity) or white-on-black (negative polarity). In experiments 2 and 3, display colour was additionally manipulated. A positive polarity advantage in the discrimination task was consistently observed. In contrast, positive displays interfered more than negative displays with subsequent detection. The detrimental after-effect of positive polarity displays was strong with white and blue, reduced with amber and absent with red displays. Subjective measures showed a preference for blue over red, but a slight advantage for amber over blue. Implications for TFT-LCD design are derived from the results. STATEMENT OF RELEVANCE: When using TFT-LCDs as car instrument panels, positive polarity red TFT-LCDs are very likely to lead to good instrument readability while at the same time minimising - relative to other colours - the negative effects of an illuminated display on low-contrast object detection during night-time driving.

  19. Optimal parameters of monolithic high-index contrast grating VCSELs

    Science.gov (United States)

    Marciniak, Magdalena; Gebski, Marcin; Dems, Maciej; Czyszanowski, Tomasz

    2016-04-01

    Monolithic High refractive index Contrast Grating (MHCG) allows several-fold size reduction of epitaxial structure of VCSEL and facilitates VCSEL fabrication in all photonic material systems. MHCGs can be fabricated of material which refractive index is higher than 1.75 without the need of the combination of low and high refractive index materials. MHCGs have a great application potential in optoelectronic devices, especially in phosphide- and nitride-based VCSELs, which suffer from the lack of efficient monolithically integrated DBR mirrors. MHCGs can simplify the construction of VCSELs, reducing their epitaxial design to monolithic wafer with carrier confinement and active region inside and etched stripes on both surfaces in post processing. In this paper we present results of numerical analysis of MHCGs as a high reflective mirrors for broad range of refractive indices that corresponds to plethora of materials typically used in optoelectronics. Our calculations base on a three-dimensional, fully vectorial optical model. We investigate the reflectance of the MHCG mirrors of different design as the function of the refractive index and we show the optimal geometrical parameters of MHCG enabling nearly 100% reflectance and broad reflection stop-band. We show that MHCG can be designed based on most of semiconductors materials and for any incident light wavelength from optical spectrum.

  20. High contrast single molecule tracking in the pericellular coat

    Science.gov (United States)

    Scrimgeour, Jan; McLane, Louis T.; Curtis, Jennifer E.

    2014-03-01

    The pericellular coat is a robust, hydrated, polymer brush-like structure that can extend several micrometers into the extracellular space around living cells. By controlling access to the cell surface, acting as a filter and storage reservoir for proteins, and actively controlling tissue-immune system interactions, the cell coat performs many important functions at scales ranging from the single cell to whole tissues. The cell coat consists of a malleable backbone - the large polysaccharide hyaluronic acid (HA) - with its structure, material properties, and ultimately its bio-functionality tuned by a diverse set of HA binding proteins. These proteins add charge, cross-links and growth factor-like ligands to the coat To probe the dynamic behavior of this soft biomaterial we have used high contrast single molecule imaging, based on highly inclined laser illumination, to observe individual fluorescently labeled HA binding proteins within the cell coat. Our work focuses on the cell coat of living chondrocyte (cartilage) cells, and in particular the effect of the large, highly charged, protein aggrecan on the properties of the coat. Through single molecule imaging we observe that aggrecan is tightly tethered to HA, and plays an important role in cell coat extension and stiffening.

  1. Monolithic subwavelength high refractive-index-contrast grating VCSELs

    Science.gov (United States)

    Gebski, Marcin; Dems, Maciej; Lott, James A.; Czyszanowski, Tomasz

    2016-03-01

    In this paper we present optical design and simulation results of vertical-cavity surface-emitting lasers (VCSELs) that incorporate monolithic subwavelength high refractive-index-contrast grating (MHCG) mirrors - a new variety of HCG mirror that is composed of high index material surrounded only on one side by low index material. We show the impact of an MHCG mirror on the performance of 980 nm VCSELs designed for high bit rate and energy-efficient optical data communications. In our design, all or part of the all-semiconductor top coupling distributed Bragg reflector mirror is replaced by an undoped gallium-arsenide MHCG. We show how the optical field intensity distribution of the VCSEL's fundamental mode is controlled by the combination of the number of residual distributed Bragg reflector (DBR) mirror periods and the physical design of the topmost gallium-arsenide MHCG. Additionally, we numerically investigate the confinement factors of our VCSELs and show that this parameter for the MHCG DBR VCSELs may only be properly determined in two or three dimensions due to the periodic nature of the grating mirror.

  2. A triphenylamine-based benzoxazole derivative as a high-contrast piezofluorochromic material induced by protonation.

    Science.gov (United States)

    Xue, Pengchong; Chen, Peng; Jia, Junhui; Xu, Qiuxia; Sun, Jiabao; Yao, Boqi; Zhang, Zhenqi; Lu, Ran

    2014-03-11

    A triphenylamine-based benzoxazole derivative exhibits a low contrast piezofluorochromic behavior under external pressure, and a high-contrast fluorescence change induced by protonation can be observed.

  3. MEPHISTO - Mapping the Exoplanet Population via High-Contrast Observations

    Science.gov (United States)

    Apai, Daniel

    The surprising recent discovery of four large-separation super-Jupiters highlighted how little we know about the giant exoplanet population beyond 5 AU. The HR8799bcd system includes three 7-10 jupiter-mass planets at separations > 24 AU. This system is not simply the result of a scaled-up version of the Solar System formation, but suggests a qualitatively different way of super-jupiter formation, perhaps efficient only in initially massive disks. At the same time, these spectacular images demonstrated the opportunity high-contrast imaging has to offer in answering three fundamental questions: 1)How frequent are gas giants and super-Jupiters as a function of host star mass? 2)What are the planet mass and semi-major axis distributions? 3)How frequent are HR8799-like multiple super-jupiter systems? In addition to answering these questions, most large-separation giant planets discovered from ground-based observations today will also be ideal targets for JWST for in-depth spectroscopic characterization. To study the properties of the large-separation giant exoplanet population we developed new high-contrast imaging techniques that work in the 3-4 micron atmospheric window. These ground-based observations reach the most favorable contrasts and sensitivities to giant planets and also remain sensitive to few Gyr-old planets, in contrast to shorter- wavelength observations. We demonstrated the advantage of these techniques in technical papers, on-sky published surveys, on the HR8799bcd planets and by confirming the nature of the planet candidate around Beta Pictoris b (results in press in Science). Here we propose to utilize these well-tested, powerful techniques to significantly extend our sensitive imaging surveys to image all 138 known southern stars around which we are capable of detecting at least 5 Jupiter-mass planets on separations smaller than 70 AU, analogs to the HR8799bcd system. Our goal is to provide a statistically well sampled range of spectral type and

  4. An objective method for High Dynamic Range source content selection

    DEFF Research Database (Denmark)

    Narwaria, Manish; Mantel, Claire; Da Silva, Matthieu Perreira

    2014-01-01

    component of such validation studies is the selection of a challenging and balanced set of source (reference) HDR content. In order to facilitate this, we present an objective method based on the premise that a more challenging HDR scene encapsulates higher contrast, and as a result will show up more...

  5. Non-contrast enhanced MRI for evaluation of breast lesions: comparison of non-contrast enhanced high spectral and spatial resolution (HiSS) images vs. contrast enhanced fat-suppressed images

    Science.gov (United States)

    Medved, Milica; Fan, Xiaobing; Abe, Hiroyuki; Newstead, Gillian M.; Wood, Abbie M.; Shimauchi, Akiko; Kulkarni, Kirti; Ivancevic, Marko K.; Pesce, Lorenzo L.; Olopade, Olufunmilayo I.; Karczmar, Gregory S.

    2011-01-01

    RATIONALE AND OBJECTIVES To evaluate high spectral and spatial resolution (HiSS) MRI for diagnosis of breast cancer without injection of contrast media: to compare the performance of pre-contrast HiSS images to conventional contrast-enhanced fat-suppressed T1-weighted images, based on image quality and in the task of classifying benign and malignant breast lesions. MATERIALS AND METHODS Ten benign and 44 malignant lesions were imaged at 1.5T with HiSS (pre-contrast administration) and conventional fat-suppressed imaging (3–10 min post-contrast). This set of 108 images, after randomization, was evaluated by three experienced radiologists blinded to the imaging technique. BIRADS morphologic criteria (lesion shape; lesion margin; internal signal intensity pattern) and final assessment were used to measure reader performance. Image quality was evaluated based on boundary delineation and quality of fat suppression. An overall probability of malignancy was assigned to each lesion for HiSS and conventional images separately. RESULTS On boundary delineation and quality of fat-suppression, pre-contrast HiSS scored similarly to conventional post-contrast MRI. On benign vs. malignant lesion separation, there was no statistically significant difference in ROC performance between HiSS and conventional MRI, and HiSS met a reasonable non-inferiority condition. CONCLUSION Pre-contrast HiSS imaging is a promising approach for showing lesion morphology without blooming and other artifacts caused by contrast agents. HiSS images could be used to guide subsequent dynamic contrast-enhanced MRI scans, to maximize spatial and temporal resolution in suspicious regions. HiSS MRI without contrast agent injection may be particularly important for patients at risk for contrast-induced nephrogenic systemic fibrosis, or allergic reactions. PMID:21962476

  6. Influence of sinogram affirmed iterative reconstruction of CT data on image noise characteristics and low-contrast detectability: an objective approach.

    Directory of Open Access Journals (Sweden)

    Christian von Falck

    Full Text Available OBJECTIVES: To utilize a novel objective approach combining a software phantom and an image quality metric to systematically evaluate the influence of sinogram affirmed iterative reconstruction (SAFIRE of multidetector computed tomography (MDCT data on image noise characteristics and low-contrast detectability (LCD. MATERIALS AND METHODS: A low-contrast and a high-contrast phantom were examined on a 128-slice scanner at different dose levels. The datasets were reconstructed using filtered back projection (FBP and SAFIRE and virtual low-contrast lesions (-20HU were inserted. LCD was evaluated using the multiscale structural similarity index (MS-SIM*. Image noise texture and spatial resolution were objectively evaluated. RESULTS: The use of SAFIRE led to an improvement of LCD for all dose levels and lesions sizes. The relative improvement of LCD was inversely related to the dose level, declining from 208%(±37%, 259%(±30% and 309%(±35% at 25mAs to 106%(±6%, 119%(±9% and 123%(±8% at 200mAs for SAFIRE filter strengths of 1, 3 and 5 (p<0.05. SAFIRE reached at least the LCD of FBP at a relative dose of 50%. There was no statistically significant difference in spatial resolution. The use of SAFIRE led to coarser image noise granularity. CONCLUSION: A novel objective approach combining a software phantom and the MS-SSIM* image quality metric was used to analyze the detectability of virtual low-contrast lesions against the background of image noise as created using SAFIRE in comparison to filtered back-projection. We found, that image noise characteristics using SAFIRE at 50% dose were comparable to the use of FBP at 100% dose with respect to lesion detectability. The unfamiliar imaging appearance of iteratively reconstructed datasets may in part be explained by a different, coarser noise characteristic as demonstrated by a granulometric analysis.

  7. High-speed optical observations of contrast agent destruction

    NARCIS (Netherlands)

    Bouakaz, Ayache; Versluis, Michel; Jong, de Nico

    2005-01-01

    Ultrasound contrast agents are now available since a few years and used for diagnostic purposes. Improved diagnostic decisions have been made possible with new imaging methods that are mainly based on the nonlinear properties of gas microbubbles. Since it is well known that contrast agents are destr

  8. High Contrast Imaging in the Visible: First Experimental Results at the Large Binocular Telescope

    CERN Document Server

    Pedichini, F; Ambrosino, A; Puglisi, A; Pinna, E; Bailey, V; Carbonaro, L; Centrone, M; Christou, J; Esposito, S; Farinato, J; Fiore, F; Giallongo, E; Hill, J M; Hinz, P M; Sabatini, L

    2016-01-01

    In February 2014, the SHARK-VIS (System for High contrast And coronography from R to K at VISual bands) Forerunner, a high contrast experimental imager operating at visible wavelengths, was installed at LBT (Large Binocular Telescope). Here we report on the first results obtained by recent on-sky tests. These results show the extremely good performance of the LBT ExAO (Extreme Adaptive Optics) system at visible wavelengths, both in terms of spatial resolution and contrast achieved. Similarly to what was done by (Amara et al. 2012), we used the SHARK-VIS Forerunner data to quantitatively assess the contrast enhancement. This is done by injecting several different synthetic faint objects in the acquired data and applying the ADI (angular differential imaging) technique. A contrast of the order of $5 \\times 10^{-5}$ is obtained at 630 nm for angular separations from the star larger than 100 mas. These results are discussed in light of the future development of SHARK-VIS and compared to those obtained by other hi...

  9. Modeling the Subjective Quality of Highly Contrasted Videos Displayed on LCD With Local Backlight Dimming

    DEFF Research Database (Denmark)

    Mantel, Claire; Bech, Søren; Korhonen, Jari

    2015-01-01

    Local backlight dimming is a technology aiming at both saving energy and improving visual quality on television sets. As the rendition of the image is specified locally, the numerical signal corresponding to the displayed image needs to be computed through a model of the display. This simulated...... signal can then be used as input to objective quality metrics. The focus of this paper is on determining which characteristics of locally backlit displays influence quality assessment. A subjective experiment assessing the quality of highly contrasted videos displayed with various local backlight......-dimming algorithms is set up. Subjective results are then compared with both objective measures and objective quality metrics using different display models. The first analysis indicates that the most significant objective features are temporal variations, power consumption (probably representing leakage...

  10. High-Contrast NIR Polarization Imaging of MWC480

    Science.gov (United States)

    McElwain, M. W.; Kusakabe, N.; Hashimoto, J.; Kudo, T.; Kandori, R.; Miyama, S.; Morino, J.-I.; Suto, H.; Suzuki, R.; Tamura, M.; Grady, C. A.; Sitko, M. L.; Werren, C.; Day, A. N.; Beerman, C.; Iye, M.; Lynch, D. K.; Russell, R. W.; Brafford, S. M.

    2012-01-01

    One of the key predictions of modeling from the IR excess of Herbig Ae stars is that for protoplanetary disks, where significant grain growth and settling has occurred, the dust disk has flattened to the point that it can be partially or largely shadowed by the innermost material at or near the dust sublimation radius. When the self-shadowing has already started, the outer disk is expected to be detected in scattered light only in the exceptional cases that the scale height of the dust disk at the sublimation radius is smaller than usual. High-contrast imaging combined with the IR spectral energy distribution allow us to measure the degree of flattening of the disk, as well as to determine the properties of the outer disk. We present polarimetric differential imaging in H band obtained with Subaru/HiCIAO of one such system, MWC 480. The HiCIAO data were obtained at a historic minimum of the NIR excess. The disk is detected in scattered light from 0".2-1"0 (27.4-137 AU). Together with the marginal detection of the disk from 1998 February 24 by HST / NICMOS, our data constrain the opening half angle for the disk to lie between 1.3 <= Theta <=2.2 deg. When compared with similar measures in CO for the gas disk from the literature, the dust disk subtends only approx 30% of the gas disk scale height (H/R approx 0. 03). Such a dust disk is a factor of 5-7 flatter than transitional disks, which have structural signatures that giant planets have formed.

  11. Contrasting the edge- and surface-based theories of object recognition: behavioral evidence from macaques (Macaca mulatta).

    Science.gov (United States)

    Parron, Carole; Washburn, David

    2010-01-01

    This study assessed the contribution of edge and surface cues on object representation in macaques (Macaca mulatta). In Experiments 1 and 2, 5 macaques were trained to discriminate 4 simple volumetric objects (geons) and were subsequently tested for their ability to recognize line drawings, silhouettes, and light changes of these geons. Performance was above chance in all test conditions and was similarly high for the line drawings and silhouettes of geons, suggesting the use of the outline shape to recognize the original objects. In addition, transfer for the geons seen under new lighting was greater than for the other stimuli, stressing the importance of the shading information. Experiment 3, using geons filled with new textures, showed that a radical change in the surface cues does not prevent object recognition. It is concluded that these findings support a surface-based theory of object recognition in macaques, although it does not exclude the contribution of edge cues, especially when surface details are not available.

  12. Electrical Capacitance Volume Tomography with High-Contrast Dielectrics

    Science.gov (United States)

    Nurge, Mark

    2010-01-01

    The Electrical Capacitance Volume Tomography (ECVT) system has been designed to complement the tools created to sense the presence of water in nonconductive spacecraft materials, by helping to not only find the approximate location of moisture but also its quantity and depth. The ECVT system has been created for use with a new image reconstruction algorithm capable of imaging high-contrast dielectric distributions. Rather than relying solely on mutual capacitance readings as is done in traditional electrical capacitance tomography applications, this method reconstructs high-resolution images using only the self-capacitance measurements. The image reconstruction method assumes that the material under inspection consists of a binary dielectric distribution, with either a high relative dielectric value representing the water or a low dielectric value for the background material. By constraining the unknown dielectric material to one of two values, the inverse math problem that must be solved to generate the image is no longer ill-determined. The image resolution becomes limited only by the accuracy and resolution of the measurement circuitry. Images were reconstructed using this method with both synthetic and real data acquired using an aluminum structure inserted at different positions within the sensing region. The cuboid geometry of the system has two parallel planes of 16 conductors arranged in a 4 4 pattern. The electrode geometry consists of parallel planes of copper conductors, connected through custom-built switch electronics, to a commercially available capacitance to digital converter. The figure shows two 4 4 arrays of electrodes milled from square sections of copper-clad circuit-board material and mounted on two pieces of glass-filled plastic backing, which were cut to approximately square shapes, 10 cm on a side. Each electrode is placed on 2.0-cm centers. The parallel arrays were mounted with the electrode arrays approximately 3 cm apart. The open ends

  13. Digital differential interference contrast autofocus for high-resolution oil-immersion microscopy.

    Science.gov (United States)

    Shen, Feimo; Hodgson, Louis; Price, Jeffrey H; Hahn, Klaus M

    2008-07-01

    Continued advances in cellular fluorescent biosensors enable studying intracellular protein dynamics in individual, living cells. Autofocus is valuable in such studies to compensate for temperature drift, uneven substrate over multiple fields of view, and cell growth during long-term high-resolution time-lapse studies of hours to days. Observing cellular dynamics with the highest possible resolution and sensitivity motivates the use of high numerical aperture (NA) oil-immersion objectives, and control of fluorescence exposure to minimize phototoxicity. To limit phototoxicity, to maximize light throughput of the objective for biosensor studies, and because phase contrast is distorted by the meniscus in microtiter plates, we studied autofocus in differential interference contrast (DIC) microscopy with a 60x 1.45 NA oil objective after removing the analyzer from the fluorescent light path. Based on a study of the experimental DIC modulation transfer function, we designed a new bandpass digital filter for measuring image sharpness. Repeated tests of DIC autofocus with this digital filter on 225 fields-of-view resulted in a precision of 8.6 nm (standard deviation). Autofocus trials on specimens with thicknesses from 9.47 to 33.20 mum, controlled by cell plating density, showed that autofocus precision was independent of specimen thickness. The results demonstrated that the selected spatial frequencies enabled very high-precision autofocus for high NA DIC automated microscopy, thereby potentially removing the problems of meniscus distortion in phase contrast imaging of microtiter plates and rendering the toxicity of additional fluorescence exposure unnecessary. (c) 2008 International Society for Advancement of Cytometry

  14. High contrast imaging through adaptive transmittance control in the focal plane

    Science.gov (United States)

    Dhadwal, Harbans S.; Rastegar, Jahangir; Feng, Dake

    2016-05-01

    High contrast imaging, in the presence of a bright background, is a challenging problem encountered in diverse applications ranging from the daily chore of driving into a sun-drenched scene to in vivo use of biomedical imaging in various types of keyhole surgeries. Imaging in the presence of bright sources saturates the vision system, resulting in loss of scene fidelity, corresponding to low image contrast and reduced resolution. The problem is exacerbated in retro-reflective imaging systems where the light sources illuminating the object are unavoidably strong, typically masking the object features. This manuscript presents a novel theoretical framework, based on nonlinear analysis and adaptive focal plane transmittance, to selectively remove object domain sources of background light from the image plane, resulting in local and global increases in image contrast. The background signal can either be of a global specular nature, giving rise to parallel illumination from the entire object surface or can be represented by a mosaic of randomly orientated, small specular surfaces. The latter is more representative of real world practical imaging systems. Thus, the background signal comprises of groups of oblique rays corresponding to distributions of the mosaic surfaces. Through the imaging system, light from group of like surfaces, converges to a localized spot in the focal plane of the lens and then diverges to cast a localized bright spot in the image plane. Thus, transmittance of a spatial light modulator, positioned in the focal plane, can be adaptively controlled to block a particular source of background light. Consequently, the image plane intensity is entirely due to the object features. Experimental image data is presented to verify the efficacy of the methodology.

  15. Contrast enhanced ultrasound with quantitative perfusion analysis for objective characterization of pancreatic ductal adenocarcinoma: A feasibility study.

    Science.gov (United States)

    D'Onofrio, Mirko; Canestrini, Stefano; Crosara, Stefano; De Robertis, Riccardo; Pozzi Mucelli, Roberto

    2014-03-28

    The aim of this study was to determine whether contrast enhanced ultrasound (CEUS) quantitative perfusion analysis allows an objective characterization of ductal adenocarcinoma (ADK) of the pancreas. Patients with pancreatic ADK underwent CEUS. All examinations were performed on an Acuson S2000 system (Siemens, Erlangen, Germany) after the iv administration of 2.4 mL contrast agent (SonoVue(®), Bracco, Milan, Italy). All lesions were pathologically proved. An operator manually drew different regions of interest within the tumor and the adjacent parenchyma to allow the quantitative perfusion analysis. The mean values of peak of enhancement, time to peak and ascending curve were calculated and compared using the Student's t test. The quantitative perfusion analysis was possible in all lesions. The mean values of the peak of enhancement, time to peak and ascending curve were 17.19%, 7.97 s and 159.52% s within the tumor and 33.57%, 8.89 s and 355.29% s within the adjacent parenchyma. The peak of enhancement and the ascending curve values were significantly different within the tumor and the adjacent parenchyma. Thus, CEUS allows the quantitative perfusion analysis of pancreatic ductal adenocarcinoma.

  16. High Performance Object-Oriented Scientific Programming in Fortran 90

    Science.gov (United States)

    Norton, Charles D.; Decyk, Viktor K.; Szymanski, Boleslaw K.

    1997-01-01

    We illustrate how Fortran 90 supports object-oriented concepts by example of plasma particle computations on the IBM SP. Our experience shows that Fortran 90 and object-oriented methodology give high performance while providing a bridge from Fortran 77 legacy codes to modern programming principles. All of our object-oriented Fortran 90 codes execute more quickly thatn the equeivalent C++ versions, yet the abstraction modelling capabilities used for scentific programming are comparably powereful.

  17. Post-processing of high-contrast observations of exoplanets

    Directory of Open Access Journals (Sweden)

    Gladysz S.

    2011-07-01

    Full Text Available Post-processing of images delivered by the eXtreme Adaptive Optics (XAO instrumentation is a crucial step which can increase achievable contrast even by two orders of magnitude. In this communication I present a new class of algorithms for detection of extrasolar planets from a sequence of adaptive-optics-corrected images. In general, the methods discriminate between real sources and stellar PSF features based on statistics of recorded intensity. The methods are particularly useful in dealing with static speckles which are the greatest obstacle in detecting exoplanets.

  18. Measurements of high-contrast starshade performance in the field

    Science.gov (United States)

    Smith, Daniel; Warwick, Steven; Glassman, Tiffany M.; Novicki, Megan C.; Richards, Michael C.; Harness, Anthony; Patterson, Keith D.

    2016-07-01

    The external starshade is a method for the direct detection and spectral characterization of terrestrial planets around other stars, a key goal identified in ASTRO2010. In an effort to validate the starlight-suppression performance of the starshade, we have measured contrast better than 1×10-9 using 60 cm starshades at points just beyond the starshade tips. These measurements were made over a 50% spectral bandpass, using an incoherent light source (a white LED), and in challenging outdoor test environments. Our experimental setup is designed to provide starshade to telescope separation and telescope aperture size that are scaled as closely as possible to the flight system. The measurements confirm not only the overall starlight-suppression capability of the starshade concept but also the robustness of the setup to optical disturbances such as atmospheric effects at the test site. The spectral coverage is limited only by the optics and detectors in our test setup, not by the starshade itself. Here we describe our latest results as well as detailed comparisons of the measured results to model predictions. Plans and status of the next phase of ground testing are also discussed.

  19. Fat suppression techniques for obtaining high resolution dynamic contrast enhanced bilateral breast MR images at 7 tesla

    DEFF Research Database (Denmark)

    van der Velden, Tijl A; Schmitz, Alexander M Th; Gilhuijs, Kenneth G A

    2016-01-01

    OBJECTIVES: To compare water selective excitation (WSE) and Dixon fat suppression in the context of high-resolution dynamic contrast enhanced MRI of the breast at 7 tesla. METHODS: Ten healthy volunteers and one patient with a malignant breast lesion were scanned at 7 tesla. The MRI protocol...

  20. Subwavelength-thick Lenses with High Numerical Apertures and Large Efficiency Based on High Contrast Transmitarrays

    CERN Document Server

    Arbabi, Amir; Ball, Alexander J; Bagheri, Mahmood; Faraon, Andrei

    2014-01-01

    We report subwavelength-thick, polarization insensitive micro-lenses operating at telecom wavelength with focal spots as small as 0.57 wavelengths and measured focusing efficiency up to 82%. The lens design is based on high contrast transmitarrays that enable control of optical phase fronts with subwavelength spatial resolution. A rigorous method for ultra-thin lens design, and the trade-off between high efficiency and small spot size (or large numerical aperture) are discussed. The transmitarrays, composed of silicon nano-posts on glass, could be fabricated by high-throughput photo or nanoimprint lithography, thus enabling widespread adoption.

  1. A high precision technique to correct for residual atmospheric dispersion in high-contrast imaging systems

    CERN Document Server

    Pathak, P; Jovanovic, N; Lozi, J; Martinache, F; Minowa, Y; Kudo, T; Takami, H; Hayano, Y; Narita, N

    2016-01-01

    Direct detection and spectroscopy of exoplanets requires high contrast imaging. For habitable exoplanets in particular, located at small angular separation from the host star, it is crucial to employ small inner working angle (IWA) coronagraphs that efficiently suppress starlight. These coronagraphs, in turn, require careful control of the wavefront which directly impacts their performance. For ground-based telescopes, atmospheric refraction is also an important factor, since it results in a smearing of the PSF, that can no longer be efficiently suppressed by the coronagraph. Traditionally, atmospheric refraction is compensated for by an atmospheric dispersion compensator (ADC). ADC control relies on an a priori model of the atmosphere whose parameters are solely based on the pointing of the telescope, which can result in imperfect compensation. For a high contrast instrument like the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system, which employs very small IWA coronagraphs, refraction-induced sm...

  2. Hydrologic Model Development and Calibration: Contrasting a Single- and Multi-Objective Approach for Comparing Model Performance

    Science.gov (United States)

    Asadzadeh, M.; Maclean, A.; Tolson, B. A.; Burn, D. H.

    2009-05-01

    Hydrologic model calibration aims to find a set of parameters that adequately simulates observations of watershed behavior, such as streamflow, or a state variable, such as snow water equivalent (SWE). There are different metrics for evaluating calibration effectiveness that involve quantifying prediction errors, such as the Nash-Sutcliffe (NS) coefficient and bias evaluated for the entire calibration period, on a seasonal basis, for low flows, or for high flows. Many of these metrics are conflicting such that the set of parameters that maximizes the high flow NS differs from the set of parameters that maximizes the low flow NS. Conflicting objectives are very likely when different calibration objectives are based on different fluxes and/or state variables (e.g., NS based on streamflow versus SWE). One of the most popular ways to balance different metrics is to aggregate them based on their importance and find the set of parameters that optimizes a weighted sum of the efficiency metrics. Comparing alternative hydrologic models (e.g., assessing model improvement when a process or more detail is added to the model) based on the aggregated objective might be misleading since it represents one point on the tradeoff of desired error metrics. To derive a more comprehensive model comparison, we solved a bi-objective calibration problem to estimate the tradeoff between two error metrics for each model. Although this approach is computationally more expensive than the aggregation approach, it results in a better understanding of the effectiveness of selected models at each level of every error metric and therefore provides a better rationale for judging relative model quality. The two alternative models used in this study are two MESH hydrologic models (version 1.2) of the Wolf Creek Research basin that differ in their watershed spatial discretization (a single Grouped Response Unit, GRU, versus multiple GRUs). The MESH model, currently under development by Environment

  3. A generalized quantitative interpretation of dark-field contrast for highly concentrated microsphere suspensions

    Science.gov (United States)

    Gkoumas, Spyridon; Villanueva-Perez, Pablo; Wang, Zhentian; Romano, Lucia; Abis, Matteo; Stampanoni, Marco

    2016-10-01

    In X-ray grating interferometry, dark-field contrast arises due to partial extinction of the detected interference fringes. This is also called visibility reduction and is attributed to small-angle scattering from unresolved structures in the imaged object. In recent years, analytical quantitative frameworks of dark-field contrast have been developed for highly diluted monodisperse microsphere suspensions with maximum 6% volume fraction. These frameworks assume that scattering particles are separated by large enough distances, which make any interparticle scattering interference negligible. In this paper, we start from the small-angle scattering intensity equation and, by linking Fourier and real-space, we introduce the structure factor and thus extend the analytical and experimental quantitative interpretation of dark-field contrast, for a range of suspensions with volume fractions reaching 40%. The structure factor accounts for interparticle scattering interference. Without introducing any additional fitting parameters, we successfully predict the experimental values measured at the TOMCAT beamline, Swiss Light Source. Finally, we apply this theoretical framework to an experiment probing a range of system correlation lengths by acquiring dark-field images at different energies. This proposed method has the potential to be applied in single-shot-mode using a polychromatic X-ray tube setup and a single-photon-counting energy-resolving detector.

  4. High contrast two-photon imaging of fingermarks

    Science.gov (United States)

    Stoltzfus, Caleb R.; Rebane, Aleksander

    2016-04-01

    Optically-acquired fingermarks are widely used as evidence across law enforcement agencies as well as in the courts of law. A common technique for visualizing latent fingermarks on nonporous surfaces consists of cyanoacrylate fuming of the fingerprint material, followed by impregnation with a fluorescent dye, which under ultra violet (UV) illumination makes the fingermarks visible and thus accessible for digital recording. However, there exist critical circumstances, when the image quality is compromised due to high background scattering, high auto-fluorescence of the substrate material, or other detrimental photo-physical and photo-chemical effects such as light-induced damage to the sample. Here we present a novel near-infrared (NIR), two-photon induced fluorescence imaging modality, which significantly enhances the quality of the fingermark images, especially when obtained from highly reflective and/or scattering surfaces, while at the same time reducing photo-damage to sensitive forensic samples.

  5. Optimum angle-cut of collimator for dense objects in high-energy proton radiography

    Science.gov (United States)

    Xu, Hai-Bo; Zheng, Na

    2016-02-01

    The use of minus identity lenses with an angle-cut collimator can achieve high contrast images in high-energy proton radiography. This article presents the principles of choosing the angle-cut aperture of the collimator for different energies and objects. Numerical simulation using the Monte Carlo code Geant4 has been implemented to investigate the entire radiography for the French test object. The optimum angle-cut apertures of the collimators are also obtained for different energies. Supported by NSAF (11176001) and Science and Technology Developing Foundation of China Academy of Engineering Physics (2012A0202006)

  6. High functional load inhibits phonological contrast loss: a corpus study.

    Science.gov (United States)

    Wedel, Andrew; Kaplan, Abby; Jackson, Scott

    2013-08-01

    For nearly a century, linguists have suggested that diachronic merger is less likely between phonemes with a high functional load--that is, phonemes that distinguish many words in the language in question. However, limitations in data and computational power have made assessing this hypothesis difficult. Here we present the first larger-scale study of the functional load hypothesis, using data from sound changes in a diverse set of languages. Our results support the functional load hypothesis: phoneme pairs undergoing merger distinguish significantly fewer minimal pairs in the lexicon than unmerged phoneme pairs. Furthermore, we show that higher phoneme probability is positively correlated with merger, but that this effect is stronger for phonemes that distinguish no minimal pairs. Finally, within our dataset we find that minimal pair count and phoneme probability better predict merger than change in system entropy at the lexical or phoneme level.

  7. An Object Oriented and High Performance Platform for Aerothermodynamics Simulation

    OpenAIRE

    Lani, Andrea

    2008-01-01

    This thesis presents the author's contribution to the design and implementation of COOLFluiD,an object oriented software platform for the high performance simulation of multi-physics phenomena on unstructured grids. In this context, the final goal has been to provide a reliable tool for handling high speed aerothermodynamic applications. To this end, we introduce a number of design techniques that have been developed in order to provide the framework with flexibilityand reusability, allowing ...

  8. Collision phenomena involving highly-charged ions in astronomical objects

    Science.gov (United States)

    Chutjian, A.

    2001-01-01

    A description of the role of highly charged ions in various astronomical objects; includes the use of critical quantities such as cross sections for excitation, charge-exchange, X-ray emission, radiative recombination (RR) and dielectronic recombination (DR); and lifetimes, branching ratios, and A-values.

  9. Exploring Planetary System Evolution Through High-Contrast Imaging

    Science.gov (United States)

    Esposito, Thomas; Fitzgerald, Michael P.; Kalas, Paul; Graham, James R.; Millar-Blanchaer, Max; Gpies Team

    2015-01-01

    Direct imaging of circumstellar disks provides unique information about planetary system construction and evolution. Several hundred nearby main-sequence stars are known to host debris disks, which are produced by mutual collisions of orbiting planetesimals during a phase thought to coincide with terrestrial planet formation. Therefore, detection of the dust in such systems through scattered near-infrared starlight offers a view of the circumstellar environment during the epoch of planet assembly. We have used ground-based coronagraphic angular differential imaging (ADI) with Keck NIRC2 and Gemini Planet Imager (GPI) to investigate disk structures that may act as signposts of planets. ADI and its associated image processing algorithms (e.g., LOCI) are powerful tools for suppressing the stellar PSF and quasistatic speckles that can contaminate disk signal. However, ADI PSF-subtraction also attenuates disk surface brightness in a spatially- and parameter-dependent manner, thereby biasing photometry and compromising inferences regarding the physical processes responsible for the dust distribution. To account for this disk "self-subtraction," we developed a novel technique to forward model the disk structure and compute a self-subtraction map for a given ADI-processed image. Applying this method to NIRC2 near-IR imaging of the HD 32297 debris disk, we combined the high signal-to-noise ratio (S/N) of ADI data with unbiased photometry to measure midplane curvature in the edge-on disk and a break in the disk's radial brightness profile. Such a break may indicate the location of a planetesimal ring that is a source of the light-scattering micron-sized grains. For the HD 61005 debris disk, we examined similar data together with GPI 1.6-micron polarization data and detected the dust ring's swept-back morphology, brightness asymmetry, stellocentric offset, and inner clearing. To study the physical mechanism behind these features, we explored how eccentricity and mutual

  10. High-contrast all-glass volumetric photonic crystal

    Science.gov (United States)

    Filipkowski, A.; van Caloen, G.; Buczynski, R.; Kujawa, I.; Pysz, D.; Vermeulen, N.; Thienpont, H.; Stepien, R.

    2010-12-01

    In this work we designed and made a photonic crystal structure with a photonic band gap around 532 nm wavelength. The structure was to be made from two commercially available glasses. Both should have similar temperature coefficients (alpha), also melting and softening temperatures should be as close as possible in order to thermally process both glasses together. In addition the refractive indexes of chosen glasses should be as different as possible in order to facilitate a wide band gap. The pair of glasses that met those requirements is LLF1 and SF6 produced by Schott. For those two glasses we performed a series of computer simulations using MIT MPB software. After checking various structures the widest band gap for the 532 nm wavelength was found for the hexagonal structure of high dielectric constant rods in low index material with a linear fill factor of 0.12 and a lattice constant 3.75 μm. This structure was manufactured using the stack and draw method. The measurements of the final structure made by ESM show that it is regular, with diffusion between glasses at the manageable level. This assures that manufacture process is repeatable.

  11. Stochastic optimal phase retrieval algorithm for high-contrast imaging

    Science.gov (United States)

    Give'on, Amir; Kasdin, N. Jeremy; Vanderbei, Robert J.; Spergel, David N.; Littman, Michael G.; Gurfil, Pini

    2003-12-01

    The Princeton University Terrestrial Planet Finder (TPF) has been working on a novel method for direct imaging of extra solar planets using a shaped-pupil coronagraph. The entrance pupil of the coronagraph is optimized to have a point spread function (PSF) that provides the suppression level needed at the angular separation required for detection of extra solar planets. When integration time is to be minimized, the photon count at the planet location in the image plane is a Poisson distributed random process. The ultimate limitation of these high-dynamic-range imaging systems comes from scattering due to imperfections in the optical surfaces of the collecting system. The first step in correcting the wavefront errors is the estimation of the phase aberrations. The phase aberration caused by these imperfections is assumed to be a sum of two-dimensional sinusoidal functions. Its parameters are estimated using a global search with a genetic algorithm and a local optimization with the BFGS quasi-Newton method with a mixed quadratic and cubic line search procedure.

  12. High contrast ratio, high uniformity multiple quantum well spatial light modulators

    Energy Technology Data Exchange (ETDEWEB)

    Huang Yuyang; Yang Chen; Yang Hui [Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Liu, H C; Cui Guoxin; Bian Lifeng; Zhang Yaohui [Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China); Wasilewski, Z R; Buchanan, M; Laframboise, S R, E-mail: yhzhang2006@sinano.ac.c [Institute for Microstructural Sciences, National Research Council, Ottawa K1A 0R6 (Canada)

    2010-03-15

    Our latest research results on GaAs-AlGaAs multiple quantum well spatial light modulators are presented. The thickness uniformity of the epitaxial layers across the 3-inch wafer grown by our molecular beam epitaxy is better than 0.1% and the variation of cavity resonance wavelength within the wafer is only 0.9 nm. A contrast ratio (CR) of 102 by varying bias voltage from 0 to 6.7 V is achieved after fine tuning the cavity by etching an adjust layer. Both theoretical and experimental results demonstrate that incorporating an adjust layer is an effective tuning method for obtaining high CR. (semiconductor integrated circuits)

  13. Prospective randomized comparison of standard didactic lecture versus high-fidelity simulation for radiology resident contrast reaction management training.

    Science.gov (United States)

    Wang, Carolyn L; Schopp, Jennifer G; Petscavage, Jonelle M; Paladin, Angelisa M; Richardson, Michael L; Bush, William H

    2011-06-01

    The objective of our study was to assess whether high-fidelity simulation-based training is more effective than traditional didactic lecture to train radiology residents in the management of contrast reactions. This was a prospective study of 44 radiology residents randomized into a simulation group versus a lecture group. All residents attended a contrast reaction didactic lecture. Four months later, baseline knowledge was assessed with a written test, which we refer to as the "pretest." After the pretest, the 21 residents in the lecture group attended a repeat didactic lecture and the 23 residents in the simulation group underwent high-fidelity simulation-based training with five contrast reaction scenarios. Next, all residents took a second written test, which we refer to as the "posttest." Two months after the posttest, both groups took a third written test, which we refer to as the "delayed posttest," and underwent performance testing with a high-fidelity severe contrast reaction scenario graded on predefined critical actions. There was no statistically significant difference between the simulation and lecture group pretest, immediate posttest, or delayed posttest scores. The simulation group performed better than the lecture group on the severe contrast reaction simulation scenario (p = 0.001). The simulation group reported improved comfort in identifying and managing contrast reactions and administering medications after the simulation training (p ≤ 0.04) and was more comfortable than the control group (p = 0.03), which reported no change in comfort level after the repeat didactic lecture. When compared with didactic lecture, high-fidelity simulation-based training of contrast reaction management shows equal results on written test scores but improved performance during a high-fidelity severe contrast reaction simulation scenario.

  14. The TRENDS High-Contrast Imaging Survey. III. A Faint White Dwarf Companion Orbiting HD 114174

    CERN Document Server

    Crepp, Justin R; Howard, Andrew W; Marcy, Geoffrey W; Gianninas, Alexandros; Kilic, Mukremin; Wright, Jason T

    2013-01-01

    The nearby Sun-like star HD 114174 exhibits a strong and persistent Doppler acceleration indicating the presence of an unseen distant companion. We have acquired high-contrast imaging observations of this star using NIRC2 at Keck and report the direct detection of the body responsible for causing the "trend". HD 114174 B has a projected separation of 692+/-9 mas (18.1 AU) and is 10.75+/-0.12 magnitudes (contrast of 5x10{-5}) fainter than its host in the K-band, requiring aggressive point-spread function subtraction to identify. Our astrometric time baseline of 1.4 years demonstrates physical association through common proper motion. We find that the companion has absolute magnitude, M_J=13.97+/-0.11, and colors, J-K= 0.12+/-0.16 mag. These characteristics are consistent with an ~T3 dwarf, initially leading us to believe that HD 114174 B was a substellar object. However, a dynamical analysis that combines radial velocity measurements with available imaging data indicates a minimum mass of m=0.260+/-0.010Msun. ...

  15. Contrasting effects of feature-based statistics on the categorisation and basic-level identification of visual objects.

    Science.gov (United States)

    Taylor, Kirsten I; Devereux, Barry J; Acres, Kadia; Randall, Billi; Tyler, Lorraine K

    2012-03-01

    Conceptual representations are at the heart of our mental lives, involved in every aspect of cognitive functioning. Despite their centrality, a long-standing debate persists as to how the meanings of concepts are represented and processed. Many accounts agree that the meanings of concrete concepts are represented by their individual features, but disagree about the importance of different feature-based variables: some views stress the importance of the information carried by distinctive features in conceptual processing, others the features which are shared over many concepts, and still others the extent to which features co-occur. We suggest that previously disparate theoretical positions and experimental findings can be unified by an account which claims that task demands determine how concepts are processed in addition to the effects of feature distinctiveness and co-occurrence. We tested these predictions in a basic-level naming task which relies on distinctive feature information (Experiment 1) and a domain decision task which relies on shared feature information (Experiment 2). Both used large-scale regression designs with the same visual objects, and mixed-effects models incorporating participant, session, stimulus-related and feature statistic variables to model the performance. We found that concepts with relatively more distinctive and more highly correlated distinctive relative to shared features facilitated basic-level naming latencies, while concepts with relatively more shared and more highly correlated shared relative to distinctive features speeded domain decisions. These findings demonstrate that the feature statistics of distinctiveness (shared vs. distinctive) and correlational strength, as well as the task demands, determine how concept meaning is processed in the conceptual system.

  16. High level architecture evolved modular federation object model

    Institute of Scientific and Technical Information of China (English)

    Wang Wenguang; Xu Yongping; Chen Xin; Li Qun; Wang Weiping

    2009-01-01

    To improve the agility, dynamics, composability, reusability, and development efficiency restricted by monolithic federation object model (FOM), a modular FOM is proposed by high level architecture (HLA) evolved product development group. This paper reviews the state-of-the-art of HLA evolved modular FOM. In particular, related concepts, the overall impact on HLA standards, extension principles, and merging processes are discussed. Also permitted and restricted combinations, and merging rules are provided, and the influence on HLA interface specification is given. The comparison between modular FOM and base object model (BOM) is performed to illustrate the importance of their combination. The applications of modular FOM are summarized. Finally, the significance to facilitate compoable simulation both in academia and practice is presented and future directions are pointed out.

  17. High level architecture evolved modular federation object model

    CERN Document Server

    Wang, Wenguang; Chen, Xin; Li, Qun; Wang, Weiping

    2009-01-01

    To improve the agility, dynamics, composability, reusability, and development efficiency restricted by monolithic Federation Object Model (FOM), a modular FOM was proposed by High Level Architecture (HLA) Evolved product development group. This paper reviews the state-of-the-art of HLA Evolved modular FOM. In particular, related concepts, the overall impact on HLA standards, extension principles, and merging processes are discussed. Also permitted and restricted combinations, and merging rules are provided, and the influence on HLA interface specification is given. The comparison between modular FOM and Base Object Model (BOM) is performed to illustrate the importance of their combination. The applications of modular FOM are summarized. Finally, the significance to facilitate composable simulation both in academia and practice is presented and future directions are pointed out.

  18. Characterization of the Gaseous Companion k Andromedae B* New Keck and LBTI High-contrast Observations

    Science.gov (United States)

    Bonnefoy, M.; Currie, T.; Marleau, G.-D.; Schlieder, J. E.; Wisniewski, J.; Carson, J.; Covey, K. R.; Henning, T.; Biller, B.; Hinz, P.; Klahr, H.; Boyer, A. N. Marsh; Zimmerman, N.; Janson, M.; McElwain, M.; Mordasini, C.; Skemer, A.; Bailey, V.; Defrere, D.; Thalmann, C.; Skrutskie, M.; Allard, F.; Homeier, D.; Tamura, M.; Grady, C.

    2013-01-01

    Context. We previously reported the direct detection of a low mass companion at a projected separation of 55+/-2 astronomical units around the B9 type star kappa Andromedae. The properties of the system (mass ratio, separation) make it a benchmark for the understanding of the formation and evolution of gas giant planets and brown dwarfs on wide-orbits. Aims. We present new angular differential imaging (ADI) images of the system at 2.146 (K(sub s)), 3.776 (L'), 4.052 (NB 4.05) and 4.78 micrometers (M') obtained with Keck/NIRC2 and LBTI/LMIRCam, as well as more accurate near-infrared photometry of the star with the MIMIR instrument. We aim to determine the near-infrared spectral energy distribution (SED) of the companion and use it to characterize the object. Methods. We used analysis methods adapted to ADI to extract the companion flux. We compared the photometry of the object to reference young/old objects and to a set of seven PHOENIX-based atmospheric models of cool objects accounting for the formation of dust. We used evolutionary models to derive mass estimates considering a wide range of plausible initial conditions. Finally, we used dedicated formation models to discuss the possible origin of the companion. Results. We derive a more accurate J = 15.86 +/- 0.21, H = 14.95 +/- 0.13, K(sub s) = 14.32 +/- 0.09 mag for kappa And b. We redetect the companion in all our high contrast observations. We confirm previous contrasts obtained at K(sub s) and L' band. We derive NB 4.05 = 13.0 +/- 0.2 and M' = 13.3 +/- 0.3 mag and estimate Log(base 10)(L/solar luminosity) = -3.76 +/- 0.06. Atmospheric models yield T(sub eff) = 1900(+100/-200) K. They do not set constrains on the surface gravity. "Hot-start" evolutionary models predict masses of 14(+25/-2) Jupiter mass based on the luminosity and temperature estimates, and considering a conservative age range for the system (30(+120/-10) million years). "warm-start" evolutionary tracks constrain the mass to M greater than or

  19. TCM: A Vision-based Algorithm for Distinguishing Between Stationary and Moving Objects Irrespective of Depth Contrast from a UAS

    Directory of Open Access Journals (Sweden)

    Reuben Strydom

    2016-05-01

    Full Text Available This paper describes an airborne vision system that is capable of determining whether an object is moving or stationary in an outdoor environment. The proposed method, coined the Triangle Closure Method (TCM, achieves this goal by computing the aircraft’s egomotion and combining it with information about the directions connecting the object and the UAS, and the expansion of the object in the image. TCM discriminates between stationary and moving objects with an accuracy rate of up to 96%. The performance of the method is validated in outdoor field tests by implementation in real-time on a quadrotor UAS. We demonstrate that the performance of TCM is better than that of a traditional background subtraction technique, as well as a method that employs the Epipolar Constraint Method. Unlike background subtraction, TCM does not generate false alarms due to parallax when a stationary object is at a distance other than that of the background. It also prevents false negatives when the object is moving along an epipolar constraint. TCM is a reliable and computationally efficient scheme for detecting moving objects, which provides an additional safety layer for autonomous navigation.

  20. High frequency nonlinear scattering from a micrometer to submicrometer sized lipid encapsulated contrast agent

    NARCIS (Netherlands)

    Goertz, David E.; Frijlink, Martijn E.; de Jong, N.; van der Steen, A.F.W.

    2006-01-01

    An experimental lipid encapsulated contrast agent comprised substantially of micrometer to submicrometer diameter bubbles was evaluated for its capacity to produce nonlinear scattering in response to high transmit frequencies. Agent characterization experiments were conducted at transmit frequencies

  1. Noise reduction in muon tomography for detecting high density objects

    CERN Document Server

    Benettoni, M; Bonomi, G; Calvagno, G; Calvini, P; Checchia, P; Cortelazzo, G; Cossutta, L; Donzella, A; Furlan, M; Gonella, F; Pegoraro, M; Garola, A Rigoni; Ronchese, P; Squarcia, S; Subieta, M; Vanini, S; Viesti, G; Zanuttigh, P; Zenoni, A; Zumerle, G

    2013-01-01

    The muon tomography technique, based on multiple Coulomb scattering of cosmic ray muons, has been proposed as a tool to detect the presence of high density objects inside closed volumes. A new and innovative method is presented in this paper to handle the density fluctuations (noise) of reconstructed images, that are a known problem of this technique. The effectiveness of our method is evaluated using experimental data obtained with a muon tomography prototype located at Legnaro National Laboratories (LNL) of the Istituto Nazionale di Fisica Nucleare (INFN). The results reported in this paper, obtained with real cosmic ray data, show that with appropriate image filtering and muon momentum classification, the muon tomography technique can detect in short times high density materials, such as lead, when surrounded by light or medium density material. A comparison with algorithms published in literature is also presented.

  2. Noise reduction in muon tomography for detecting high density objects

    Science.gov (United States)

    Benettoni, M.; Bettella, G.; Bonomi, G.; Calvagno, G.; Calvini, P.; Checchia, P.; Cortelazzo, G.; Cossutta, L.; Donzella, A.; Furlan, M.; Gonella, F.; Pegoraro, M.; Rigoni Garola, A.; Ronchese, P.; Squarcia, S.; Subieta, M.; Vanini, S.; Viesti, G.; Zanuttigh, P.; Zenoni, A.; Zumerle, G.

    2013-12-01

    The muon tomography technique, based on multiple Coulomb scattering of cosmic ray muons, has been proposed as a tool to detect the presence of high density objects inside closed volumes. In this paper a new and innovative method is presented to handle the density fluctuations (noise) of reconstructed images, a well known problem of this technique. The effectiveness of our method is evaluated using experimental data obtained with a muon tomography prototype located at the Legnaro National Laboratories (LNL) of the Istituto Nazionale di Fisica Nucleare (INFN). The results reported in this paper, obtained with real cosmic ray data, show that with appropriate image filtering and muon momentum classification, the muon tomography technique can detect high density materials, such as lead, albeit surrounded by light or medium density material, in short times. A comparison with algorithms published in literature is also presented.

  3. High-Speed, Three Dimensional Object Composition Mapping Technology

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, M Y

    2001-02-14

    This document overviews an entirely new approach to determining the composition--the chemical-elemental, isotopic and molecular make-up--of complex, highly structured objects, moreover with microscopic spatial resolution in all 3 dimensions. The front cover depicts the new type of pulsed laser system at the heart of this novel technology under adjustment by Alexis Wynne, and schematically indicates two of its early uses: swiftly analyzing the 3-D composition governed structure of a transistor circuit with both optical and mass-spectrometric detectors, and of fossilized dinosaur and turtle bones high-speed probed by optical detection means. Studying the composition-cued 3-D micro-structures of advanced composite materials and the microscopic scale composition-texture of biological tissues are two near-term examples of the rich spectrum of novel applications enabled by this field-opening analytic tool-set.

  4. Towards Ultra-High Q Microresonators in High-Index Contrast AlGaAs-On-Insulator

    DEFF Research Database (Denmark)

    Pu, Minhao; Kamel, Ayman Nassar; Stassen, Erik

    2017-01-01

    We demonstrate an AlGaAs-on-insulator microresonator with intrinsic Q as high as 690,000. We optimized the fabrication and investigated the impact of waveguide dimension on the Q in such a high-index contrast platform.......We demonstrate an AlGaAs-on-insulator microresonator with intrinsic Q as high as 690,000. We optimized the fabrication and investigated the impact of waveguide dimension on the Q in such a high-index contrast platform....

  5. Ultra-high contrast frontend for high peak power fs-lasers at 1030 nm.

    Science.gov (United States)

    Liebetrau, Hartmut; Hornung, Marco; Seidel, Andreas; Hellwing, Marco; Kessler, Alexander; Keppler, Sebastian; Schorcht, Frank; Hein, Joachim; Kaluza, Malte C

    2014-10-01

    We present the results from a new frontend within a double-chirped pulse amplification architecture (DCPA) utilizing crossed-polarized wave generation (XPW) for generating ultra-high contrast, 150 μJ-level, femtosecond seed pulses at 1030 nm. These pulses are used in the high energy class diode-pumped laser system Polaris at the Helmholtz Institute in Jena. Within this frontend, laser pulses from a 75 MHz oscillator-pulse train are extracted at a repetition rate of 1 Hz, temporally stretched, amplified and then recompressed reaching a pulse energy of 2 mJ, a bandwidth of 12 nm and 112 fs pulse duration at a center wavelength of 1030 nm. These pulses are temporally filtered via XPW in a holographic-cut BaF₂ crystal, resulting in 150 μJ pulse energy with an efficiency of 13 %. Due to this non-linear filtering, the relative intensity of the amplified spontaneous emission preceding the main pulse is suppressed to 2×10⁻¹³. This is, to the best of our knowledge, the lowest value achieved in a high peak power laser system operating at 1030 nm center wavelength.

  6. High-Contrast Coronagraph Performance in the Presence of DM Actuator Defects

    Science.gov (United States)

    Sidick, Erkin; Shaklan, Stuart; Cady, Eric

    2015-01-01

    Deformable Mirrors (DMs) are critical elements in high contrast coronagraphs, requiring precision and stability measured in picometers to enable detection of Earth-like exoplanets. Occasionally DM actuators or their associated cables or electronics fail, requiring a wavefront control algorithm to compensate for actuators that may be displaced from their neighbors by hundreds of nanometers. We have carried out experiments on our High-Contrast Imaging Testbed (HCIT) to study the impact of failed actuators in partial fulfillment of the Terrestrial Planet Finder Coronagraph optical model validation milestone. We show that the wavefront control algorithm adapts to several broken actuators and maintains dark-hole contrast in broadband light.

  7. Thermoacoustic contrast of prostate cancer due to heating by very high frequency irradiation

    Science.gov (United States)

    Patch, S. K.; Hull, D.; Thomas, M.; Griep, SK; Jacobsohn, K.; See, WA

    2015-01-01

    Applying the thermoacoustic (TA) effect to diagnostic imaging was first proposed in the 1980s. The object under test is irradiated by high-power pulses of electromagnetic energy, which heat tissue and cause thermal expansion. Outgoing TA pressure pulses are detected by ultrasound transducers and reconstructed to provide images of the object. The TA contrast mechanism is strongly dependent upon the frequency of the irradiating electromagnetic pulse. When very high frequency (VHF) electromagnetic irradiation is utilized, TA signal production is driven by ionic content. Prostatic fluids contain high levels of ionic metabolites, including citrate, zinc, calcium, and magnesium. Healthy prostate glands produce more ionic metabolites than diseased glands. VHF pulses are therefore expected to generate stronger TA signal in healthy prostate glands than in diseased glands. A benchtop system for performing ex vivo TA computed tomography with VHF energy is described and images are presented. The system utilizes irradiation pulses of 700 ns duration exceeding 20 kW power. Reconstructions frequently visualize anatomic landmarks such as the urethra and verumontanum. TA reconstructions from three freshly excised human prostate glands with little, moderate, and severe cancerous involvement are compared with histology. TA signal strength is negatively correlated with percent cancerous involvement in this small sample size. For the 45 regions of interest analyzed, a reconstruction value of 0.4 mV provides 100% sensitivity but only 29% specificity. This sample size is far too small to draw sweeping conclusions, but the results warrant a larger volume study including comparison of TA images to the gold standard, histology.

  8. Phase contrast imaging using Betatron x-ray beams produced by a 100 TW high intensity laser system

    Science.gov (United States)

    Fourmaux, Sylvain; Corde, Sebastien; Ta Phuoc, Kim; Lassonde, Philippe; Martin, Francois; Malka, Victor; Rousse, Antoine; Kieffer, Jean

    2011-10-01

    Development of x-ray phase contrast imaging applications with a laboratory scale source have been limited by the long exposure time needed to obtain one image. We demonstrate, using the Betatron x-ray radiation produced when electrons are accelerated and wiggled in the laser-wakefield cavity, the potential of Betatron x-ray radiation for femtosecond phase contrast imaging. We characterize the x-ray source using a knife edge technique and nylon wires for calibration. We then show that high-quality phase contrast images of complex objects located in air, can be obtained with only a single laser shot. The Betatron x-ray source used in this demonstration experiment has a source diameter of 1.7 microns and produces a synchrotron spectrum with critical energy Ec = 12 . 3 + / - 2 . 5 keV and 109 photons per shot in the whole spectrum.

  9. A high-contrast coronagraph for earth-like exoplanet direct imaging: design and test

    CERN Document Server

    Liu, C C; Dou, J P; Zhu, Y T; Zhang, X; Zhao, G; Wu, Zh; Chen, R

    2014-01-01

    The high-contrast coronagraph for direct imaging earth-like exoplanet at the visible needs a contrast of 10^(-10) at a small angular separation of 4 lambda/D or less. Here we report our recent laboratory experiment that is close to the limits. The test of the high-contrast imaging coronagraph is based on our step-transmission apodized filter. To achieve the goal, we use a liquid crystal array (LCA) as a phase corrector to create a dark hole based on our dedicated focal dark algorithm. We have suppressed the diffracted and speckle noise near the star point image to a level of 1.68 x 10^(-9) at 4 lambda/D, which can be immediately used for the direct imaging of Jupiter like exoplanets. This demonstrates that high-contrast coronagraph telescope in space has the potentiality to detect and characterize earth-like planets.

  10. High-contrast Imaging of Intermediate-mass Giants with Long-term Radial Velocity Trends

    Science.gov (United States)

    Ryu, Tsuguru; Sato, Bun'ei; Kuzuhara, Masayuki; Narita, Norio; Takahashi, Yasuhiro H.; Uyama, Taichi; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Omiya, Masashi; Harakawa, Hiroki; Abe, Lyu; Ando, Hiroyasu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Currie, Thayne; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Hełminiak, Krzysztof G.; Henning, Thomas; Hodapp, Klaus W.; Ida, Shigeru; Ishii, Miki; Itoh, Yoichi; Iye, Masanori; Izumiura, Hideyuki; Janson, Markus; Kambe, Eiji; Kandori, Ryo; Knapp, Gillian R.; Kokubo, Eiichiro; Kwon, Jungmi; Matsuo, Taro; Mayama, Satoshi; McElwain, Michael W.; Mede, Kyle; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Takeda, Yoichi; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L.; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Yoshida, Michitoshi; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2016-07-01

    A radial velocity (RV) survey for intermediate-mass giants has been in operation for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct-imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations of six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to γ Hya B ({0.61}-0.14+0.12{M}⊙ ), HD 5608 B (0.10+/- 0.01{M}⊙ ), and HD 109272 B (0.28+/- 0.06{M}⊙ ). For the remaining targets (ι Dra, 18 Del, and HD 14067), we exclude companions more massive than 30-60 M Jup at projected separations of 1″-7″. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find that the Kozai mechanism can explain the high eccentricity of the inner planets ι Dra b, HD 5608 b, and HD 14067 b.

  11. Optical polarization of high-energy BL Lac objects

    CERN Document Server

    Hovatta, T; Blinov, D; Pavlidou, V; Nilsson, K; Kiehlmann, S; Angelakis, E; Ramazani, V Fallah; Liodakis, I; Myserlis, I; Panopoulou, G V; Pursimo, T

    2016-01-01

    We investigate the optical polarization properties of high-energy BL Lac objects using data from the RoboPol blazar monitoring program and the Nordic Optical Telescope. We wish to understand if there are differences in the BL Lac objects that are detected with the current-generation TeV instruments compared to those that have not yet been detected. The mean polarization fraction of the TeV-detected BL Lacs is 5% while the non-TeV sources show a higher mean polarization fraction of 7%. This difference in polarization fraction disappears when the dilution by the unpolarized light of the host galaxy is accounted for. The TeV sources show somewhat lower fractional polarization variability amplitudes than the non-TeV sources. Also the fraction of sources with a smaller spread in the Q/I - U/I -plane and a clumped distribution of points away from the origin, possibly indicating a preferred polarization angle, is larger in the TeV than in the non-TeV sources. These differences between TeV and non-TeV samples seems t...

  12. Subharmonic, non-linear fundamental and ultraharmonic imaging of microbubble contrast at high frequencies.

    Science.gov (United States)

    Daeichin, Verya; Bosch, Johan G; Needles, Andrew; Foster, F Stuart; van der Steen, Antonius; de Jong, Nico

    2015-02-01

    There is increasing use of ultrasound contrast agent in high-frequency ultrasound imaging. However, conventional contrast detection methods perform poorly at high frequencies. We performed systematic in vitro comparisons of subharmonic, non-linear fundamental and ultraharmonic imaging for different depths and ultrasound contrast agent concentrations (Vevo 2100 system with MS250 probe and MicroMarker ultrasound contrast agent, VisualSonics, Toronto, ON, Canada). We investigated 4-, 6- and 10-cycle bursts at three power levels with the following pulse sequences: B-mode, amplitude modulation, pulse inversion and combined pulse inversion/amplitude modulation. The contrast-to-tissue (CTR) and contrast-to-artifact (CAR) ratios were calculated. At a depth of 8 mm, subharmonic pulse-inversion imaging performed the best (CTR = 26 dB, CAR = 18 dB) and at 16 mm, non-linear amplitude modulation imaging was the best contrast imaging method (CTR = 10 dB). Ultraharmonic imaging did not result in acceptable CTRs and CARs. The best candidates from the in vitro study were tested in vivo in chicken embryo and mouse models, and the results were in a good agreement with the in vitro findings.

  13. High mechanical index post-contrast ultrasonography improves tissue structural display of hepatocellular carcinoma

    Institute of Scientific and Technical Information of China (English)

    CHEN Min-hua; YANG Wei; DAI Ying; WU Wei

    2005-01-01

    Background The advent of second generation agent-SonoVue and low mechanical index real-time contrast enhanced ultrasonography (CEUS) imaging have been shown to improve the diagnostic performance of ultrasonography in hepatocellular carcinoma (HCC). But no report has described the effect of high mechanical index (MI) post-CEUS. This study aimed to investigate the value of post-CEUS in displaying tissue structures of HCC. Methods Seventy-six HCCs in 65 patients were included in the study. Each patient underwent three scans, high-MI (MI: 0.15-1.6) pre-contrast ultrasound, low-MI (MI: 0.04-0.08) CEUS with contrast agent SonoVue, and high-MI post-contrast ultrasound, which was performed within 3 minutes after CEUS. The size, boundary, echogenicity, internal echotexture and posterior acoustic enhancement of the HCCs in the conventional scans before and after CEUS were evaluated. According to pathological evidence, diagnosis rates of pre-contrast, CEUS and post-contrast scans were determined and compared. The potential mechanism of post-contrast ultrasound imaging was also discussed. Results Compared with pre-contrast, post-contrast ultrasound showed improvement in image quality in most HCCs: twenty-six (34.2%) more lesions showed well defined margins and fourteen (18.4%) more nodules showed halo sign; twenty-three (30.3%) lesions demonstrated enlarged in sizes; changes in echogenicity were seen in 30 lesions (39.5%); eighteen (23.7%) more lesions showed heterogenecity and 20 (26.3%) more lesions showed "mosaic" or "nodule-in-nodule" sign; twelve (15.8%) more lesions showed posterior acoustic enhancement. Post-contrast ultrasound showed increased diagnostic accuracy of 93.4% (71/76), compare with 88.2% (67/76) of CEUS alone. Conclusions High-MI post-contrast ultrasound utilizes harmonic signals during the rupture of microbubbles, and significantly improves the display of echo-characteristics of HCCs in ultrasound images, which adds diagnostic values for CEUS. Post-contrast

  14. Efficient multi-keV X-ray generation from high-contrast laser plasma interaction

    Directory of Open Access Journals (Sweden)

    Zhang Z.

    2013-11-01

    Full Text Available Kα line emission from Mo was experimentally and theoretically studied using clean, ultrahigh-intensity femtosecond laser pulses. The absolute yields of Kα x-rays at 17 keV from Mo were measured as a function of the laser pulse contrast ratio and irradiation intensity. Significantly enhanced Kα yields were obtained by employing high contrast ratio at optimum irradiance. Conversion efficiencies of 4.28 × 10−5/sr, the highest values obtained to date, was demonstrated with contrast ratios in the range of 10−10 to 10−11.

  15. X-Ray CT of Highly-Attenuating Objects: 9- or 15- MV Spectra?

    Energy Technology Data Exchange (ETDEWEB)

    Stone, G; Trebes, J; Perry, R; Schneberk, D; Logan, C

    2005-08-29

    We imaged-highly attenuating test objects in three dimensions with 9-MV (at LLNL) and 15-MV (at Hill Air Force Base) x-ray spectra. While we used the same detector and motion control, there were differences that we could not control in the two radiography bays and in the sources. The results show better spatial resolution for the 9-MV spectrum and better contrast for the 15-MV spectrum. The 15-MV data contains a noise pattern that obfuscates the data. It is our judgment that if sufficient attention were given to design of the bay, beam dump, collimation, filtration and linac spot size; a 15-MV imaging system using a flat panel could be developed with spatial resolution of 5 lp/mm and contrastive performance better than we have demonstrated using a 9-MV spectrum.

  16. On filtration for high-energy phase-contrast x-ray imaging

    Science.gov (United States)

    Riess, Christian; Mohamed, Ashraf; Hinshaw, Waldo; Fahrig, Rebecca

    2015-03-01

    Phase-sensitive x-ray imaging promises unprecedented soft-tissue contrast and resolution. However, several practical challenges have to be overcome when using the setup in a clinical environment. The system design that is currently closest to clinical use is the grating-based Talbot-Lau interferometer (GBI).1-3 The requirements for patient imaging are low patient dose, fast imaging time, and high image quality. For GBI, these requirements can be met most successfully with a narrow energy width, high- ux spectrum. Additionally, to penetrate a human-sized object, the design energy of the system has to be well above 40 keV. To our knowledge, little research has been done so far to investigate optimal GBI filtration at such high x-ray energies. In this paper, we study different filtration strategies and their impact on high-energy GBI. Specifically, we compare copper filtration at low peak voltage with equal-absorption, equal-imaging time K-edge filtration of spectra with higher peak voltage under clinically realistic boundary conditions. We specifically focus on a design energy of 59 keV and investigate combinations of tube current, peak voltage, and filtration that lead to equal patient absorption. Theoretical considerations suggest that the K edge of tantalum might provide a transmission pocket at around 59 keV, yielding a well-shaped spectrum. Although one can observe a slight visibility benefit when using tungsten or tantalum filtration, experimental results indicate that visibility benefits most from a low x-ray tube peak voltage.

  17. Mathematical impairment associated with high-contrast abnormalities in change detection and magnocellular visual evoked response.

    Science.gov (United States)

    Jastrzebski, Nicola R; Crewther, Sheila G; Crewther, David P

    2015-10-01

    The cause of developmental dyscalculia, a specific deficit in acquisition of arithmetic skills, particularly of enumeration, has never been investigated with respect to the patency of the visual magnocellular system. Here, the question of dysfunction of the afferent magnocellular cortical input and its dorsal stream projections was tested directly using nonlinear analysis of the visual evoked potential (VEP) and through the psychophysical ability to rapidly detect visual change. A group of young adults with self-reported deficiencies of arithmetical ability, showed marked impairment in magnitude estimation and enumeration performance-though not in lexical decision reaction times when compared with an arithmetically capable group controlled for age and handedness. Multifocal nonlinear VEPs were recorded at low (24 %) and high (96 %) contrast. First- and second-order VEP kernels were comparable between groups at low contrast, but not at high contrast. The mathematically impaired group showed an abnormal lack of contrast saturation in the shortest latency first-order peak (N60) and a delayed P100 positivity in the first slice of the second-order kernel. Both features have previously been argued to be physiological markers of magnocellular function. Mathematically impaired participants also performed worse on a gap paradigm change detection for digit task showing increased reaction times for high-contrast stimuli but not for low-contrast stimuli compared with controls. The VEP results give direct evidence of abnormality in the occipital processing of magnocellular information in those with mathematical impairment. The anomalous high visual contrast physiological and psychophysical performance suggests an abnormality in the inhibitory processes that normally result in saturation of contrast gain in the magnocellular system.

  18. High dynamic range multi-channel cross-correlator for single-shot temporal contrast measurement

    Science.gov (United States)

    Kon, A.; Nishiuchi, M.; Kiriyama, H.; Ogura, K.; Mori, M.; Sakaki, H.; Kando, M.; Kondo, K.

    2016-05-01

    We have developed a multi-channel cross-correlator for high dynamic range (>1010), single-shot temporal contrast measurements. The correlator utilizes a third-order crosscorrelation technique and has a reference channel, to be normalized by the measured peak intensity, and four independent optical delay lines. The measurement results of the shot-to-shot temporal contrast clearly show the intensity fluctuations of short pre-pulses at -4.5 ps and -26 ps before main pulse.

  19. High-velocity molecular outflows hear massive young stellar objects

    Institute of Scientific and Technical Information of China (English)

    吴月芳; 李月兴; 杨传义; 雷成明; 孙金江; 吕静; 韩溥

    1999-01-01

    By mapping the 12CO J=1—0 lines in IRAS 05391-0217, 06114+1745 and 06291+0421, three new high-velocity bipolar molecular outflows are found. Parameters of these outflows are derived, which suggest that they are massive and energetic outflows with total kinetic energies of about 1038 J and mass loss rates about 10-5 M⊙/a. The driving sources are identified by analyzing the positions, intensities and color temperatures of the associated infrared sources. These outflows are most likely driven by single sources which correspond to massive young stellar objects. In these regions H2O masers have been detected located near the embedded infrared sources, which indicates that their exciting mechanism may be correlated with that of the CO outflows. The relationship between the parameters of outflows and central sources shows that high-velocity outflow and thermal radiation of a star are two basic correlated but different features in the evolution of young stars.

  20. High-reflectivity high-contrast grating focusing reflector on silicon-on-insulator wafer

    Science.gov (United States)

    Fang, Wenjing; Huang, Yongqing; Duan, Xiaofeng; Liu, Kai; Fei, Jiarui; Ren, Xiaomin

    2016-11-01

    A high-contrast grating (HCG) focusing reflector providing phase front control of reflected light and high reflectivity is proposed and fabricated. Basic design rules to engineer this category of structures are given in detail. A 1550 nm TM polarized incident light of 11.86 mm in focal length and 0.8320 in reflectivity is obtained in experiment. The wavelength dependence of the fabricated HCGs from 1530 nm to 1580 nm is also tested. The test results show that the focal length is in the range of 11.81-12 mm, which is close to the designed focal length of 15 mm. The reflectivity is almost above 0.56 within a bandwidth of 50 nm. At a distance of 11.86 mm, the light is focused to a round spot with the highest concentration, which is much smaller than the size of the incident beam. The FWHM of the reflected light beam decreases to 120 nm, and the intensity increases to 1.18. Project supported by the National Natural Science Foundation of China (Grant Nos. 61274044, 61574019 and 61020106007), the National Basic Research Program of China (Grant No. 2010CB327600), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20130005130001), the Natural Science Foundation of Beijing, China (Grant No. 4132069), the Key International Science and Technology Cooperation Project of China (Grant No. 2011RR000100), the 111 Project of China (Grant No. B07005), and the Program for Changjiang Scholars and Innovative Research Team in Universities of China (Grant No. IRT0609).

  1. High-Index Contrast Silicon Rich Silicon Nitride Optical Waveguides and Devices

    DEFF Research Database (Denmark)

    Philipp, Hugh Taylor

    2004-01-01

    This research focused on the realization of high-density integrated optical devices made with high-index contrast waveguides. The material platform used for to develop these devices was modeled after standard silicon on silicon technology. The high-index waveguide core material was silicon rich...... silicon nitride. This provided a sharp contrast with silica and made low-loss waveguide bending radii less than 25mm possible. An immediate consequence of such small bending radii is the ability to make practical ring resonator based devices with a large free spectral range. Several ring resonator based...

  2. High resolution tomography of objects with access to a single side

    Energy Technology Data Exchange (ETDEWEB)

    Thoe, R.S.

    1993-03-24

    The author is developing a technique which will enable one to obtain high-contrast, high-spatial resolution, three-dimensional images in opaque objects. The only constraint will be the radiation source and detector(s) will be located on the same side of the object. The goal is to obtain images with a spatial resolution of {approximately}1 mm at depths of 10 mm and {approximately}3 mm at depths of 30 mm in materials of moderate density (brass, steel, etc.). The author`s technique uses a highly-collimated beam of monochromatic gamma rays and a slit collimated high-resolution, high-efficiency, coaxial germanium spectrometer. If the geometry is well known, the spectrum of Compton scattered radiation can be used to map out the density as a function of depth. By scanning the object in two dimensions, a full three-dimensional image of the electron density can be reconstructed. The resolution is dependent on the incident beam collimation and the energy resolution of the spectrometer. For his system, the author anticipates a resolution of about 1 mm{sup 3}. The apparatus, reconstruction algorithms and current data verifying his predictions are presented here. Also included are the details on how the system can be modified to increase the efficiency by over two orders of magnitude. This system will have several advantages over conventional transmission radiographic and tomographic systems: (1) It requires the use of a high specific intensity isotopic source of modest activity (< 100 mCi). (2) It requires only a single high-resolution spectrometer used in conjunction with an array of low-resolution detectors (all readily available). (3) It allows for the recording of three-dimensional images of object even though both detector and source are located on the same side of the object.

  3. High-Contrast Imaging for Intermediate-Mass Giants with Long-Term Radial Velocity Trends

    CERN Document Server

    Ryu, Tsuguru; Kuzuhara, Masayuki; Narita, Norio; Takahashi, Yasuhiro H; Uyama, Taichi; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Omiya, Masashi; Harakawa, Hiroki; Abe, Lyu; Ando, Hiroyasu; Brandner, Wolfgang; Brandt, Timothy D; Carson, Joseph C; Currie, Thayne; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S; Hełminiak, Krzysztof G; Henning, Thomas; Hodapp, Klaus W; Ida, Shigeru; Ishii, Miki; Itoh, Yoichi; Iye, Masanori; Izumiura, Hideyuki; Janson, Markus; Kambe, Eiji; Kandori, Ryo; Knapp, Gillian R; Kokubo, Eiichiro; Kwon, Jungmi; Matsuo, Taro; Mayama, Satoshi; McElwain, Michael W; Mede, Kyle; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Takeda, Yoichi; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Yoshida, Michitoshi; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2016-01-01

    A radial velocity (RV) survey for intermediate-mass giants has been operated for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations or six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to $\\gamma$ Hya B ($0.61^{+0.12}_{-0.14} M_\\odot$), HD 5608 B ($0.10 \\pm 0.01 M_\\odot$), and HD 109272 B ($0.28 \\pm 0.06 M_\\odot$). For the remaining targets($\\iota$ Dra, 18 Del, and HD 14067) we exclude companions more massive than 30-60 $M_\\mathrm{Jup}$ at projected separations of 1arcsec-7arcsec. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find ...

  4. High-index-contrast grating reflector with beam steering ability for the transmitted beam

    DEFF Research Database (Denmark)

    Carletti, Luca; Malureanu, Radu; Mørk, Jesper

    2011-01-01

    High-index contrast grating mirrors providing wave front control of the transmitted light as well as high reflectivity over a broad bandwidth are suggested and both numerically and experimentally investigated. General design rules to engineer these structures for different applications are derived...

  5. Apodization in high-contrast long-slit spectroscopy. Closer, deeper, fainter, cooler

    Science.gov (United States)

    Vigan, A.; N'Diaye, M.; Dohlen, K.

    2013-07-01

    The spectroscopy of faint planetary-mass companions to nearby stars is one of the main challenges that new-generation high-contrast spectro-imagers are going to face. However, the high contrast ratio between main-sequence stars and young planets makes it difficult to extract a companion spectrum that is not biased by the signal from the star. In a previous work we demonstrated that coupling long-slit spectroscopy (LSS) and classical Lyot coronagraphy (CLC) to form a long-slit coronagraph (LSC) allows low-mass companions to be properly characterized when combined with an innovative a posteriori data analysis methods based on the spectral deconvolution (SD). However, the presence of a slit in the coronagraphic focal plane induces a complex distribution of energy in the Lyot pupil plane that cannot be easily masked with a binary Lyot stop, creating strong diffraction residuals at close angular separation. To alleviate this concern, we propose to use a pupil apodization to suppress diffraction, creating an apodized long-slit coronagraph (ALSC). We show that this concept allows looking at a closer separation from the star, at deeper contrast, which enables the characterization of fainter substellar companions. After describing how the apodization was optimized, we demonstrate its advantages with respect to the CLC in the context of SPHERE/IRDIS LSS mode at low resolution with a 0.12'' slit and 0.18'' coronagraphic mask. We performed different sets of simulations with and without aberrations, and with and without a slit to demonstrate that the apodization is a more appropriate concept for LSS, at the expense of a significantly reduced throughput (37%) compared to the LSC. Then we performed detailed end-to-end simulations of the LSC and the ALSC that include realistic levels of aberrations to obtain several datasets representing 1 h of integration time on stars of spectral type A0 to M0 located at 10 pc. We inserted the spectra of planetary companions at different

  6. Bi-species imposex monitoring in Galicia (NW Spain) shows contrasting achievement of the OSPAR Ecological Quality Objective for TBT.

    Science.gov (United States)

    Ruiz, J M; Carro, B; Albaina, N; Couceiro, L; Míguez, A; Quintela, M; Barreiro, R

    2017-01-30

    Imposex is decreasing worldwide after the total ban on tributyltin (TBT) from antifouling paints. In order to assess improvement in the NE Atlantic, the OSPAR Convention designed an Ecological Quality Objective (EcoQO) based on the VDSI (vas deferens sequence index, an agreed measure of imposex) in the rock snail Nucella lapillus; wherever this is not available, the mud snail Nassarius reticulatus was proposed as a proxy. We determined VDSI in Galician populations of rock (n≥34) and mud (n≥18) snails at regular intervals from pre-ban times until 2009 and 2011, respectively. While imposex in the former started decreasing in 2006 and by 2009 the EcoQO had been met in the area, VDSI in the latter was not significantly reduced until 2011 and values contradict such an achievement. This suggests that the OSPAR imposex bi-species scheme may not be of direct application in the current post-ban scenario.

  7. High contrast en bloc staining of neuronal tissue for field emission scanning electron microscopy

    Science.gov (United States)

    Tapia, Juan C.; Kasthuri, Narayanan; Hayworth, Kenneth; Schalek, Richard; Lichtman, Jeff W.; Smith, Stephen J; Buchanan, JoAnn

    2013-01-01

    Conventional heavy metal post staining methods on thin sections lend contrast but often cause contamination. To avoid this problem, we tested several en bloc staining techniques to contrast tissue in serial sections mounted on solid substrates for examination by Field Emission Scanning Electron Microscope (FESEM). Because FESEM section imaging requires that specimens have higher contrast and greater electrical conductivity than transmission electron microscope (TEM) samples, our technique utilizes osmium impregnation (OTO) to make the samples conductive while heavily staining membranes for segmentation studies. Combining this step with other classic heavy metal en bloc stains including uranyl acetate, lead aspartate, copper sulfate and lead citrate produced clean, highly contrasted TEM and SEM samples of insect, fish, and mammalian nervous system. This protocol takes 7–15 days to prepare resin embedded tissue, cut sections and produce serial section images. PMID:22240582

  8. Unveiling the High Energy Obscured Universe: Hunting Collapsed Objects Physics

    Science.gov (United States)

    Ubertini, P.; Bazzano, A.; Cocchi, M.; Natalucci, L.; Bassani, L.; Caroli, E.; Stephen, J. B.; Caraveo, P.; Mereghetti, S.; Villa, G.

    2005-01-01

    A large part of energy from space is coming from collapsing stars (SN, Hypernovae) and collapsed stars (black holes, neutron stars and white dwarfs). The peak of their energy release is in the hard-X and gamma-ray wavelengths where photons are insensitive to absorption and can travel from the edge the Universe or the central core of the Galaxy without loosing the primordial information of energy, time signature and polarization. The most efficient process to produce energetic photons is gravitational accretion of matter from a "normal" star onto a collapsed companion (LGxMcollxdMacc/dtx( 1Rdisc)-dMacc/dt x c2), exceeding by far the nuclear reaction capability to generate high energy quanta. Thus our natural laboratory for "in situ" investigations are collapsed objects in which matter and radiation co-exist in extreme conditions of temperature and density due to gravitationally bent geometry and magnetic fields. This is a unique opportunity to study the physics of accretion flows in stellar mass and super-massive Black Holes (SMBHs), plasmoids generated in relativistic jets in galactic microQSOs and AGNs, ionised plasma interacting at the touching point of weakly magnetized NS surface, GRB/Supernovae connection, and the mysterious origins of "dark" GRB and X-ray flash.

  9. Fabrication of High Contrast Gratings for the Spectrum Splitting Dispersive Element in a Concentrated Photovoltaic System.

    Science.gov (United States)

    Yao, Yuhan; Liu, He; Wu, Wei

    2015-07-18

    High contrast gratings are designed and fabricated and its application is proposed in a parallel spectrum splitting dispersive element that can improve the solar conversion efficiency of a concentrated photovoltaic system. The proposed system will also lower the solar cell cost in the concentrated photovoltaic system by replacing the expensive tandem solar cells with the cost-effective single junction solar cells. The structures and the parameters of high contrast gratings for the dispersive elements were numerically optimized. The large-area fabrication of high contrast gratings was experimentally demonstrated using nanoimprint lithography and dry etching. The quality of grating material and the performance of the fabricated device were both experimentally characterized. By analyzing the measurement results, the possible side effects from the fabrication processes are discussed and several methods that have the potential to improve the fabrication processes are proposed, which can help to increase the optical efficiency of the fabricated devices.

  10. Color Vision Changes and Effects of High Contrast Visor Use at Simulated Cabin Altitudes

    Science.gov (United States)

    2016-06-08

    4. Richalet JP, Duval-Arnould G, Darnaud B, Keromes A, Rutgers V. Modification of colour vision in the green/ red axis in acute and chronic...L ( red )] was evaluated, with the S cone showing the greatest decrease at 8,000 feet. High-contrast visor use at simulated altitudes did not...on which cone [S (blue), M (green), or L ( red )] was evaluated, with the S cone showing the greatest decrease at 8,000 feet. High-contrast visor use

  11. Characterization of phase and contrast of high peak power, ultrashort laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Sagisaka, Akito; Aoyama, Makoto; Matsuoka, Sinichi; Akahane, Yutaka; Nakano, Fumihiko; Yamakawa, Koichi [Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Energy Research Inst., Kizu, Kyoto (Japan)

    2000-03-01

    We fully characterize a high-peak power, ultrashort laser pulse in a Ti:sapphire chirped-pulse amplification laser system. The phase and contrast of the 20 fs pulse are determined by using frequency-resolved optical gating and high dynamic range cross-correlation techniques. The result of the phase measurement of the pulse indicate that the predominant phase distortion is quartic. The measured contrast of the pulse is of the order of 10{sup -6} limited by amplified spontaneous emission coming from the amplifiers. (author)

  12. Waveguide-mode interference lithography technique for high contrast subwavelength structures in the visible region

    CERN Document Server

    Kusaka, Kanta; Ohno, Seigo; Sakaki, Yozaburo; Nakayama, Kazuyuki; Moritake, Yuto; Ishihara, Teruya

    2014-01-01

    We explore possibilities of waveguide-mode interference lithography (WMIL) technique for high contrast subwavelength structures in the visible region. Selecting an appropriate waveguide-mode, we demonstrate high contrast resist mask patterns for the first time. TM1 mode in the waveguide is shown to be useful for providing a three-dimensional structure whose cross section is checkerboard pattern. Applying our WMIL technique, we demonstrate 1D, 2D and 3D subwavelength resist patterns that are widely used for the fabrication of metamteterials in the visible region. In addition to the resist patterns, we demonstrate a resonance at 1.9 eV for a split tube structure experimentally.

  13. Highly magnetic iron carbide nanoparticles as effective T(2) contrast agents.

    Science.gov (United States)

    Huang, Guoming; Hu, Juan; Zhang, Hui; Zhou, Zijian; Chi, Xiaoqin; Gao, Jinhao

    2014-01-21

    This paper reports that iron carbide nanoparticles with high air-stability and strong saturation magnetization can serve as effective T2 contrast agents for magnetic resonance imaging. Fe5C2 nanoparticles (~20 nm in diameter) exhibit strong contrast enhancement with an r2 value of 283.2 mM(-1) S(-1), which is about twice as high as that of spherical Fe3O4 nanoparticles (~140.9 mM(-1) S(-1)). In vivo experiments demonstrate that Fe5C2 nanoparticles are able to produce much more significant MRI contrast enhancement than conventional Fe3O4 nanoparticles in living subjects, which holds great promise in biomedical applications.

  14. Low-signal, coronagraphic wavefront estimation with Kalman filtering in the high contrast imaging testbed

    Science.gov (United States)

    Riggs, A. J. Eldorado; Cady, Eric J.; Prada, Camilo M.; Kern, Brian D.; Zhou, Hanying; Kasdin, N. Jeremy; Groff, Tyler D.

    2016-07-01

    For direct imaging and spectral characterization of cold exoplanets in reflected light, the proposed Wide-Field Infrared Survey Telescope (WFIRST) Coronagraph Instrument (CGI) will carry two types of coronagraphs. The High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Laboratory has been testing both coronagraph types and demonstrated their abilities to achieve high contrast. Focal plane wavefront correction is used to estimate and mitigate aberrations. As the most time-consuming part of correction during a space mission, the acquisition of probed images for electric field estimation needs to be as short as possible. We present results from the HCIT of narrowband, low-signal wavefront estimation tests using a shaped pupil Lyot coronagraph (SPLC) designed for the WFIRST CGI. In the low-flux regime, the Kalman filter and iterated extended Kalman filter provide faster correction, better achievable contrast, and more accurate estimates than batch process estimation.

  15. High-contrast Coherent Population Trapping based on Crossed Polarizers Method

    CERN Document Server

    Yano, Yuichiro

    2014-01-01

    We developed a method based on crossed polarizers to observe high-contrast coherent population trapping (CPT) resonance. Since crossed polarizers have a simple optical system, our method is suitable for chip-scale atomic clocks (CSACs). We calculated the Faraday rotation in CPT in a linearly polarized light field (lin || lin) using two pairs of lambda system models based on the density matrix and estimated the spectrum of the Faraday rotation. After that, we measured the contrast and linewidth with the crossed polarizers method. A comparison of the theoretical model and experiment data showed they were in good agreement. Moreover, the experimental results showed that a high contrast (88.4 %) and narrow linewidth (1.15 kHz) resonance could be observed using a Cs gas cell and D1-line vertical-cavity surfaceemitting laser (VCSEL).

  16. Domain Decomposition Preconditioners for Multiscale Flows in High-Contrast Media

    KAUST Repository

    Galvis, Juan

    2010-01-01

    In this paper, we study domain decomposition preconditioners for multiscale flows in high-contrast media. We consider flow equations governed by elliptic equations in heterogeneous media with a large contrast in the coefficients. Our main goal is to develop domain decomposition preconditioners with the condition number that is independent of the contrast when there are variations within coarse regions. This is accomplished by designing coarse-scale spaces and interpolators that represent important features of the solution within each coarse region. The important features are characterized by the connectivities of high-conductivity regions. To detect these connectivities, we introduce an eigenvalue problem that automatically detects high-conductivity regions via a large gap in the spectrum. A main observation is that this eigenvalue problem has a few small, asymptotically vanishing eigenvalues. The number of these small eigenvalues is the same as the number of connected high-conductivity regions. The coarse spaces are constructed such that they span eigenfunctions corresponding to these small eigenvalues. These spaces are used within two-level additive Schwarz preconditioners as well as overlapping methods for the Schur complement to design preconditioners. We show that the condition number of the preconditioned systems is independent of the contrast. More detailed studies are performed for the case when the high-conductivity region is connected within coarse block neighborhoods. Our numerical experiments confirm the theoretical results presented in this paper. © 2010 Society for Industrial and Applied Mathematics.

  17. Laser-matter interaction at high intensity and high temporal contrast; Interaction laser matiere a haut flux et fort contraste temporel

    Energy Technology Data Exchange (ETDEWEB)

    Doumy, G

    2006-01-15

    The continuous progress in the development of laser installations has already lead to ultra-short pulses capable of achieving very high focalized intensities (I > 10{sup 18} W/cm{sup 2}). At these intensities, matter presents new non-linear behaviours, due to the fact that the electrons are accelerated to relativistic speeds. The experimental access to this interaction regime on solid targets has long been forbidden because of the presence, alongside the femtosecond pulse, of a pedestal (mainly due to the amplified spontaneous emission (ASE) which occurs in the laser chain) intense enough to modify the state of the target. In this thesis, we first characterized, both experimentally and theoretically, a device which allows an improvement of the temporal contrast of the pulse: the Plasma Mirror. It consists in adjusting the focusing of the pulse on a dielectric target, so that the pedestal is mainly transmitted, while the main pulse is reflected by the overcritical plasma that it forms at the surface. The implementation of such a device on the UHI 10 laser facility (CEA Saclay - 10 TW - 60 fs) then allowed us to study the interaction between ultra-intense, high contrast pulses with solid targets. In a first part, we managed to generate and characterize dense plasmas resulting directly from the interaction between the main pulse and very thin foils (100 nm). This characterization was realized by using an XUV source obtained by high order harmonics generation in a rare gas jet. In a second part, we studied experimentally the phenomenon of high order harmonics generation on solid targets, which is still badly understood, but could potentially lead to a new kind of energetic ultra-short XUV sources. (author)

  18. High-School Student Discovers Strange Astronomical Object

    Science.gov (United States)

    2009-09-01

    A West Virginia high-school student analyzing data from a giant radio telescope has discovered a new astronomical object -- a strange type of neutron star called a rotating radio transient. Lucas Bolyard, a sophomore at South Harrison High School in Clarksburg, WV, made the discovery while participating in a project in which students are trained to scrutinize data from the National Science Foundation's giant Robert C. Byrd Green The project, called the Pulsar Search Collaboratory (PSC), is a joint project of the National Radio Astronomy Observatory (NRAO) and West Virginia University (WVU), funded by a grant from the National Science Foundation. Bolyard made the discovery in March, after he already had studied more than 2,000 data plots from the GBT and found nothing. "I was home on a weekend and had nothing to do, so I decided to look at some more plots from the GBT," he said. "I saw a plot with a pulse, but there was a lot of radio interference, too. The pulse almost got dismissed as interference," he added. Nonetheless, he reported it, and it went on a list of candidates for West Virginia University astronomers Maura McLaughlin and Duncan Lorimer to re-examine, scheduling new observations of the region of sky from which the pulse came. Disappointingly, the follow-up observations showed nothing, indicating that the object was not a normal pulsar. However, the astronomers explained to Bolyard that his pulse still might have come from a rotating radio transient. Confirmation didn't come until July. Bolyard was at the NRAO's Green Bank Observatory with fellow PSC students. The night before, the group had been observing with the GBT in the wee hours, and all were very tired. Then Lorimer showed Bolyard a new plot of his pulse, reprocessed from raw data, indicating that it is real, not interference, and that Bolyard is likely the discoverer of one of only about 30 rotating radio transients known. Suddenly, Bolyard said, he wasn't tired anymore. "That news made me full

  19. High speed optical object recognition processor with massive holographic memory

    Science.gov (United States)

    Chao, T.; Zhou, H.; Reyes, G.

    2002-01-01

    Real-time object recognition using a compact grayscale optical correlator will be introduced. A holographic memory module for storing a large bank of optimum correlation filters, to accommodate the large data throughput rate needed for many real-world applications, has also been developed. System architecture of the optical processor and the holographic memory will be presented. Application examples of this object recognition technology will also be demonstrated.

  20. 3D shape measurement of objects with high dynamic range of surface reflectivity.

    Science.gov (United States)

    Liu, Gui-hua; Liu, Xian-Yong; Feng, Quan-Yuan

    2011-08-10

    This paper presents a method that allows a conventional dual-camera structured light system to directly acquire the three-dimensional shape of the whole surface of an object with high dynamic range of surface reflectivity. To reduce the degradation in area-based correlation caused by specular highlights and diffused darkness, we first disregard these highly specular and dark pixels. Then, to solve this problem and further obtain unmatched area data, this binocular vision system was also used as two camera-projector monocular systems operated from different viewing angles at the same time to fill in missing data of the binocular reconstruction. This method involves producing measurable images by integrating such techniques as multiple exposures and high dynamic range imaging to ensure the capture of high-quality phase of each point. An image-segmentation technique was also introduced to distinguish which monocular system is suitable to reconstruct a certain lost point accurately. Our experiments demonstrate that these techniques extended the measurable areas on the high dynamic range of surface reflectivity such as specular objects or scenes with high contrast to the whole projector-illuminated field.

  1. High-contrast top-emitting organic light-emitting devices

    Institute of Scientific and Technical Information of China (English)

    Chen Shu-Fen; Chen Chun-Yan; Yang Yang; Xie Jun; Huang Wei; Shi Hong-Ying; Cheng Fan

    2012-01-01

    In this paper we report on a high-contrast top-emitting organic light-emitting device utilizing a moderate-reflection contrast-enhancement stack and a high refractive index anti-reflection layer.The contrast-enhancement stack consists of a thin metal anode layer,a dielectric bilayer,and a thick metal underlayer.The resulting device,with the optimized contrast-enhancement stack thicknesses of Ni (30 nm)/MgF2 (62 nm)/ZnS (16 nm)/Ni (20 nm) and the 25-nm-thick ZnS anti-reflection layer,achieves a luminous reflectance of 4.01% in the visible region and a maximum current efficiency of 0.99 cd/A (at 62.3 mA/cm2) together with a very stable chromaticity.The contrast ratio reaches 561∶1 at an on-state brightness of 1000 cd/m2 under an ambient illumination of 140 lx.In addition,the anti-reflection layer can als0 enhance the transmissivity of the cathode and improve light out-coupling by the effective restraint of microcavity effects.

  2. Tunable Resonant-Cavity-Enhanced Photodetector with Double High-Index-Contrast Grating Mirrors

    DEFF Research Database (Denmark)

    Learkthanakhachon, Supannee; Yvind, Kresten; Chung, Il-Sug

    2013-01-01

    In this paper, we propose a broadband-tunable resonant-cavity-enhanced photodetector (RCE-PD) structure with double high-index-contrast grating (HCG) mirrors and numerically investigate its characteristics. The detector is designed to operate at 1550-nm wavelength. The detector structure consists...

  3. Experiencing More Mathematics Anxiety than Expected? Contrasting Trait and State Anxiety in High Achieving Students

    Science.gov (United States)

    Roos, A.-L.; Bieg, M.; Goetz, T.; Frenzel, A. C.; Taxer, J.; Zeidner, M.

    2015-01-01

    This study examined mathematics anxiety among high and low achieving students (N = 237, grades 9 and 10) by contrasting trait (habitual) and state (momentary) assessments of anxiety. Previous studies have found that trait anxiety measures are typically rated higher than state measures. Furthermore, the academic self-concept has been identified to…

  4. Achievement Motivation in High School: Contrasting Theoretical Models in the Classroom.

    Science.gov (United States)

    Garcia-Celay, I. Montero; Tapia, J. Alonso

    1992-01-01

    Three models of achievement motivation in the classroom are contrasted. Results with 155 high school students suggest that the model of C. S. Dweck and E. S. Elliott offers a better explanation of the relationships among achievement motivation, attributions, emotional reactions, expectancies, and performance than do the other models. (SLD)

  5. The ZIMPOL high-contrast imaging polarimeter for SPHERE: design, manufacturing, and testing

    NARCIS (Netherlands)

    Roelfsema, R.; Schmid, H.M.; Pragt, J.; Gisler, D.; Waters, R.; Bazzon, A.; Baruffolo, A.; Beuzit, J.-L.; Boccaletti, A.; Charton, J.; Cumani, C.; Dohlen, K.; Downing, M.; Elswijk, E.; Feldt, M.; Groothuis, C.; de Haan, M.; Hanenburg, H.; Hubin, N.; Joos, F.; Kasper, M.; Keller, C.; Kragt, J.; Lizon, J.-L.; Mouillet, D.; Pavlov, A.; Rigal, F.; Rochat, S.; Salasnich, B.; Steiner, P.; Thalmann, C.; Venema, L.; Wildi, F.

    2010-01-01

    ZIMPOL is the high contrast imaging polarimeter subsystem of the ESO SPHERE instrument. ZIMPOL is dedicated to detect the very faint reflected and hence polarized visible light from extrasolar planets. ZIMPOL is located behind an extreme AO system (SAXO) and a stellar coronagraph. SPHERE is foreseen

  6. The ZIMPOL high-contrast imaging polarimeter for SPHERE: design, manufacturing, and testing

    NARCIS (Netherlands)

    Roelfsema, R.; Schmid, H.M.; Pragt, J.; Gisler, D.; Waters, R.; Bazzon, A.; Baruffolo, A.; Beuzit, J.-L.; Boccaletti, A.; Charton, J.; Cumani, C.; Dohlen, K.; Downing, M.; Elswijk, E.; Feldt, M.; Groothuis, C.; de Haan, M.; Hanenburg, H.; Hubin, N.; Joos, F.; Kasper, M.; Keller, C.; Kragt, J.; Lizon, J.-L.; Mouillet, D.; Pavlov, A.; Rigal, F.; Rochat, S.; Salasnich, B.; Steiner, P.; Thalmann, C.; Venema, L.; Wildi, F.

    2010-01-01

    ZIMPOL is the high contrast imaging polarimeter subsystem of the ESO SPHERE instrument. ZIMPOL is dedicated to detect the very faint reflected and hence polarized visible light from extrasolar planets. ZIMPOL is located behind an extreme AO system (SAXO) and a stellar coronagraph. SPHERE is foreseen

  7. Dynamical dispersion engineering in coupled vertical cavities employing a high-contrast grating

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Chung, Il-Sug

    2017-01-01

    strength. This can be implemented by employing a high-contrast grating (HCG) as the coupling reflector in a system of two coupled vertical cavities, and engineering both the HCG reflection phase and amplitude response. Several examples of HCG-based coupled cavities with novel features are discussed...

  8. Vortex Image Processing (VIP) package for high-contrast direct imaging

    Science.gov (United States)

    Gomez Gonzalez, C.; Absil, O.; Wertz, O.

    2016-05-01

    VIP is a Python instrument-agnostic toolbox featuring a flexible framework for reproducible and robust data reduction. VIP currently supports three high-contrast imaging observational techniques: angular, reference-star and multi-spectral differential imaging. The code can be downloaded from our git repository on Github: http://github.com/vortex-exoplanet/VIP

  9. Scientific Design of a High Contrast Integral Field Spectrograph for the Subaru Telescope

    Science.gov (United States)

    McElwain, Michael W.

    2012-01-01

    Ground based telescopes equipped with adaptive optics systems and specialized science cameras are now capable of directly detecting extrasolar planets. We present the scientific design for a high contrast integral field spectrograph for the Subaru Telescope. This lenslet based integral field spectrograph will be implemented into the new extreme adaptive optics system at Subaru, called SCExAO.

  10. High spatial resolution hard X-ray microscope using X-ray refractive lens and phase contrast imaging experiments

    CERN Document Server

    Kohmura, Y; Takeuchi, A; Takano, H; Suzuki, Y; Ishikawa, T; Ohigashi, T; Yokosuka, H

    2001-01-01

    A high spatial resolution X-ray microscope was constructed using an X-ray refractive lens as an objective. The spatial resolution was tested using 18 keV X-ray. A 0.4 mu m line and 0.4 mu m space tantalum test pattern was successfully resolved. Using the similar setup with the addition of a phase plate, a Zernike type phase-contrast microscopy experiment was carried out for the phase retrieval of the samples. Two-dimensional phase-contrast images were successfully taken for the first time in the hard X-ray region. Images of a gold mesh sample were analyzed and the validity of this method was indicated. An improvement of the lens, however, is required for the precise phase retrieval of the samples.

  11. High-Contrast Color-Stripe Pattern for Rapid Structured-Light Range Imaging

    CERN Document Server

    Je, Changsoo; Park, Rae-Hong

    2015-01-01

    For structured-light range imaging, color stripes can be used for increasing the number of distinguishable light patterns compared to binary BW stripes. Therefore, an appropriate use of color patterns can reduce the number of light projections and range imaging is achievable in single video frame or in "one shot". On the other hand, the reliability and range resolution attainable from color stripes is generally lower than those from multiply projected binary BW patterns since color contrast is affected by object color reflectance and ambient light. This paper presents new methods for selecting stripe colors and designing multiple-stripe patterns for "one-shot" and "two-shot" imaging. We show that maximizing color contrast between the stripes in one-shot imaging reduces the ambiguities resulting from colored object surfaces and limitations in sensor/projector resolution. Two-shot imaging adds an extra video frame and maximizes the color contrast between the first and second video frames to diminish the ambigui...

  12. High contrast, depth-resolved thermoreflectance imaging using a Nipkow disk confocal microscope.

    Science.gov (United States)

    Summers, J A; Yang, T; Tuominen, M T; Hudgings, J A

    2010-01-01

    We have developed a depth-resolved confocal thermal imaging technique that is capable of measuring the temperature distribution of an encapsulated or semi-obstructed device. The technique employs lock-in charge coupled device-based thermoreflectance imaging via a Nipkow disk confocal microscope, which is used to eliminate extraneous reflections from above or below the imaging plane. We use the confocal microscope to predict the decrease in contrast and dynamic range due to an obstruction for widefield thermoreflectance, and we demonstrate the ability of confocal thermoreflectance to maintain a high contrast and thermal sensitivity in the presence of large reflecting obstructions in the optical path.

  13. High-Contrast Imaging using Adaptive Optics for Extrasolar Planet Detection

    Energy Technology Data Exchange (ETDEWEB)

    Evans, Julia Wilhelmsen [Univ. of California, Davis, CA (United States)

    2006-01-01

    Direct imaging of extrasolar planets is an important, but challenging, next step in planetary science. Most planets identified to date have been detected indirectly--not by emitted or reflected light but through the effect of the planet on the parent star. For example, radial velocity techniques measure the doppler shift in the spectrum of the star produced by the presence of a planet. Indirect techniques only probe about 15% of the orbital parameter space of our solar system. Direct methods would probe new parameter space, and the detected light can be analyzed spectroscopically, providing new information about detected planets. High contrast adaptive optics systems, also known as Extreme Adaptive Optics (ExAO), will require contrasts of between 10-6 and 10-7 at angles of 4-24 λ/D on an 8-m class telescope to image young Jupiter-like planets still warm with the heat of formation. Contrast is defined as the intensity ratio of the dark wings of the image, where a planet might be, to the bright core of the star. Such instruments will be technically challenging, requiring high order adaptive optics with > 2000 actuators and improved diffraction suppression. Contrast is ultimately limited by residual static wavefront errors, so an extrasolar planet imager will require wavefront control with an accuracy of better than 1 nm rms within the low- to mid-spatial frequency range. Laboratory demonstrations are critical to instrument development. The ExAO testbed at the Laboratory for Adaptive Optics was designed with low wavefront error and precision optical metrology, which is used to explore contrast limits and develop the technology needed for an extrasolar planet imager. A state-of-the-art, 1024-actuator micro-electrical-mechanical-systems (MEMS) deformable mirror was installed and characterized to provide active wavefront control and test this novel technology. I present 6.5 x 10-8 contrast measurements with a prolate shaped pupil and

  14. High-index-contrast grating reflector with beam steering ability for the transmitted beam.

    Science.gov (United States)

    Carletti, Luca; Malureanu, Radu; Mørk, Jesper; Chung, Il-Sug

    2011-11-07

    High-index contrast grating mirrors providing wave front control of the transmitted light as well as high reflectivity over a broad bandwidth are suggested and both numerically and experimentally investigated. General design rules to engineer these structures for different applications are derived. Such grating mirrors would have a significant impact on low cost laser fabrication, since a more efficient integration of optoelectronic modules can be achieved by avoiding expensive external lens systems.

  15. Lyot-plane phase masks for improved high-contrast imaging with a vortex coronagraph

    CERN Document Server

    Ruane, Garreth J; Absil, Olivier; Mawet, Dimitri; Delacroix, Christian; Carlomagno, Brunella; Swartzlander, Grover A

    2015-01-01

    The vortex coronagraph is an optical instrument that precisely removes on-axis starlight allowing for high contrast imaging at small angular separation from the star, thereby providing a crucial capability for direct detection and characterization of exoplanets and circumstellar disks. Telescopes with aperture obstructions, such as secondary mirrors and spider support structures, require advanced coronagraph designs to provide adequate starlight suppression. We introduce a phase-only Lyot-plane optic to the vortex coronagraph that offers improved contrast performance on telescopes with complicated apertures. Potential solutions for the European Extremely Large Telescope (E-ELT) are described and compared. Adding a Lyot-plane phase mask relocates residual starlight away from a region of the image plane thereby reducing stellar noise and improving sensitivity to off-axis companions. The phase mask is calculated using an iterative phase retrieval algorithm. Numerically, we achieve a contrast on the order of $10^...

  16. Phase Quantization Study of Spatial Light Modulator for Extreme High contrast Imaging

    CERN Document Server

    Dou, Jiangpei

    2016-01-01

    Direct imaging of exoplanets by reflected starlight is extremely challenging due to the large luminosity ratio to the primary star. Wave front control is a critical technique to attenuate the speckle noise in order to achieve an extreme high contrast. We present the phase quantization study of spatial light modulator for wave front control to meet the contrast requirement of detection of a terrestrial planet in the habitable zone of a solar-type star. We perform the numerical simulation by employing the SLM with different phase accuracy and actuator numbers, which are related to the achievable contrast. We use an optimization algorithm to solve the quantization problems that is matched to the controllable phase step of the SLM. Two optical configurations are discussed with the SLM located before and after the coronagraph focal plane mask, respectively. The simulation result has constrained the specification for phase accuracy of SLM in above two optical configurations. Finally, we have demonstrated that the S...

  17. Survey of Experimental Results in High-Contrast Imaging for Future Exoplanet Missions

    Science.gov (United States)

    Lawson, P. R.; Belikov, R.; Cash, W.; Clampin, M.; Glassman, T.; Guyon, O.; Kasdin, N. J.; Kern, B. D.; Lyon, R.; Mawet, D.; Moody, D.; Samuele, R.; Serabyn, E.; Sirbu, D.; Trauger, J.

    2013-01-01

    We present and compare experimental results in high contrast imaging representing the state of the art in coronagraph and starshade technology. These experiments have been undertaken with the goal of demonstrating the capability of detecting Earth-like planets around nearby Sun-like stars. The contrast of an Earth seen in reflected light around a Sun-like star would be about 1.2 x 10(exp -10). Several of the current candidate technologies now yield raw contrasts of 1.0 x 10(exp -9) or better, and so should enable the detection of Earths, assuming a gain in sensitivity in post-processing of a factor of 10. We present results of coronagraph and starshade experiments conducted at visible and infrared wavelengths. Cross-sections of dark fields are directly compared as a function of field angle and bandwidth. The strength and differences of the techniques are compared.

  18. Generation of 25-TW Femtosecond Laser Pulses at 515 nm with Extremely High Temporal Contrast

    Directory of Open Access Journals (Sweden)

    Marco Hornung

    2015-12-01

    Full Text Available We report on the frequency doubling of femtosecond laser pulses at 1030 nm center wavelength generated from the fully diode-pumped laser system POLARIS. The newly generated pulses at a center wavelength of 515 nm have a pulse energy of 3 J with a pulse duration of 120 fs. On the basis of initially ultra-high contrast seed pulses we expect a temporal intensity contrast better 10 17 200 ps before the peak of the main pulse. We analyzed the temporal intensity contrast from milliseconds to femtoseconds with a dynamic range covering more than 20 orders of magnitude. The pulses were focussed with a f/2-focussing parabola resulting in a peak intensity exceeding 10 20 W / cm 2 . The peak power and intensity are to the best of our knowledge the highest values for 515 nm-laser-pulses achieved so far.

  19. High-order myopic coronagraphic phase diversity (COFFEE) for wave-front control in high-contrast imaging systems.

    Science.gov (United States)

    Paul, B; Mugnier, L M; Sauvage, J-F; Dohlen, K; Ferrari, M

    2013-12-30

    The estimation and compensation of quasi-static aberrations is mandatory to reach the ultimate performance of high-contrast imaging systems. COFFEE is a focal plane wave-front sensing method that consists in the extension of phase diversity to high-contrast imaging systems. Based on a Bayesian approach, it estimates the quasi-static aberrations from two focal plane images recorded from the scientific camera itself. In this paper, we present COFFEE's extension which allows an estimation of low and high order aberrations with nanometric precision for any coronagraphic device. The performance is evaluated by realistic simulations, performed in the SPHERE instrument framework. We develop a myopic estimation that allows us to take into account an imperfect knowledge on the used diversity phase. Lastly, we evaluate COFFEE's performance in a compensation process, to optimize the contrast on the detector, and show it allows one to reach the 10(-6) contrast required by SPHERE at a few resolution elements from the star. Notably, we present a non-linear energy minimization method which can be used to reach very high contrast levels (better than 10(7) in a SPHERE-like context).

  20. Mode decomposition methods for flows in high-contrast porous media. A global approach

    KAUST Repository

    Ghommem, Mehdi

    2014-01-01

    We apply dynamic mode decomposition (DMD) and proper orthogonal decomposition (POD) methods to flows in highly-heterogeneous porous media to extract the dominant coherent structures and derive reduced-order models via Galerkin projection. Permeability fields with high contrast are considered to investigate the capability of these techniques to capture the main flow features and forecast the flow evolution within a certain accuracy. A DMD-based approach shows a better predictive capability due to its ability to accurately extract the information relevant to long-time dynamics, in particular, the slowly-decaying eigenmodes corresponding to largest eigenvalues. Our study enables a better understanding of the strengths and weaknesses of the applicability of these techniques for flows in high-contrast porous media. Furthermore, we discuss the robustness of DMD- and POD-based reduced-order models with respect to variations in initial conditions, permeability fields, and forcing terms. © 2013 Elsevier Inc.

  1. 2008 OG$_{19}$: A highly elongated Trans-Neptunian Object

    CERN Document Server

    Fernández-Valenzuela, Estela; Duffard, René; Santos-Sanz, Pablo; Morales, Nicolás

    2015-01-01

    From two observing runs during the 2014 summer at Calar Alto Observatory in Almer\\'ia (Spain) and at Sierra Nevada Observatory in Granada (Spain), we were able to derive CCD photometry of the Trans-Neptunian Object 2008 OG$_{19}$. We analyzed the time series and obtained a double-peaked light curve with a peak to valley amplitude of (0.437 $\\pm$ 0.011) mag and a rotational period of (8.727$\\pm$ 0.003) h. This implies that this object is very elongated, closely resembling Varuna's case. The photometry also allowed us to obtain an absolute magnitude in R-band of (4.39 $\\pm$ 0.07) mag. From this result we estimated an equivalent diameter of 2008 OG$_{19}$ which is 619$^{+56}_{-113}$ km using an average albedo for Scattered Disk Objects. Finally we interpreted the results under the assumption of hydrostatic equilibrium and found a lower limit for the density of 544$^{+42}_{-4}$ kg$\\,$m$^{-3}$. However, a more likely density is (609 $\\pm$ 4) kg$\\,$m$^{-3}$ using an aspect angle of 60$^\\circ$, which corresponds to ...

  2. High-Resolution and Quantitative X-Ray Phase-Contrast Tomography for Mouse Brain Research

    Directory of Open Access Journals (Sweden)

    Yan Xi

    2015-01-01

    Full Text Available Imaging techniques for visualizing cerebral vasculature and distinguishing functional areas are essential and critical to the study of various brain diseases. In this paper, with the X-ray phase-contrast imaging technique, we proposed an experiment scheme for the ex vivo mouse brain study, achieving both high spatial resolution and improved soft-tissue contrast. This scheme includes two steps: sample preparation and volume reconstruction. In the first step, we use heparinized saline to displace the blood inside cerebral vessels and then replace it with air making air-filled mouse brain. After sample preparation, X-ray phase-contrast tomography is performed to collect the data for volume reconstruction. Here, we adopt a phase-retrieval combined filtered backprojection method to reconstruct its three-dimensional structure and redesigned the reconstruction kernel. To evaluate its performance, we carried out experiments at Shanghai Synchrotron Radiation Facility. The results show that the air-tissue structured cerebral vasculatures are highly visible with propagation-based phase-contrast imaging and can be clearly resolved in reconstructed cross-images. Besides, functional areas, such as the corpus callosum, corpus striatum, and nuclei, are also clearly resolved. The proposed method is comparable with hematoxylin and eosin staining method but represents the studied mouse brain in three dimensions, offering a potential powerful tool for the research of brain disorders.

  3. High-Resolution and Quantitative X-Ray Phase-Contrast Tomography for Mouse Brain Research.

    Science.gov (United States)

    Xi, Yan; Lin, Xiaojie; Yuan, Falei; Yang, Guo-Yuan; Zhao, Jun

    2015-01-01

    Imaging techniques for visualizing cerebral vasculature and distinguishing functional areas are essential and critical to the study of various brain diseases. In this paper, with the X-ray phase-contrast imaging technique, we proposed an experiment scheme for the ex vivo mouse brain study, achieving both high spatial resolution and improved soft-tissue contrast. This scheme includes two steps: sample preparation and volume reconstruction. In the first step, we use heparinized saline to displace the blood inside cerebral vessels and then replace it with air making air-filled mouse brain. After sample preparation, X-ray phase-contrast tomography is performed to collect the data for volume reconstruction. Here, we adopt a phase-retrieval combined filtered backprojection method to reconstruct its three-dimensional structure and redesigned the reconstruction kernel. To evaluate its performance, we carried out experiments at Shanghai Synchrotron Radiation Facility. The results show that the air-tissue structured cerebral vasculatures are highly visible with propagation-based phase-contrast imaging and can be clearly resolved in reconstructed cross-images. Besides, functional areas, such as the corpus callosum, corpus striatum, and nuclei, are also clearly resolved. The proposed method is comparable with hematoxylin and eosin staining method but represents the studied mouse brain in three dimensions, offering a potential powerful tool for the research of brain disorders.

  4. Novel Gd nanoparticles enhance vascular contrast for high-resolution magnetic resonance imaging.

    Directory of Open Access Journals (Sweden)

    Tot Bui

    Full Text Available BACKGROUND: Gadolinium (Gd, with its 7 unpaired electrons in 4f orbitals that provide a very large magnetic moment, is proven to be among the best agents for contrast enhanced MRI. Unfortunately, the most potent MR contrast agent based on Gd requires relatively high doses of Gd. The Gd-chelated to diethylene-triamine-penta-acetic acid (DTPA, or other derivatives (at 0.1 mmole/kg recommended dose, distribute broadly into tissues and clear through the kidney. These contrast agents carry the risk of Nephrogenic Systemic Fibrosis (NSF, particularly in kidney impaired subjects. Thus, Gd contrast agents that produce higher resolution images using a much lower Gd dose could address both imaging sensitivity and Gd safety. METHODOLOGY/PRINCIPAL FINDINGS: To determine whether a biocompatible lipid nanoparticle with surface bound Gd can improve MRI contrast sensitivity, we constructed Gd-lipid nanoparticles (Gd-LNP containing lipid bound DTPA and Gd. The Gd-LNP were intravenously administered to rats and MR images collected. We found that Gd in Gd-LNP produced a greater than 33-fold higher longitudinal (T(1 relaxivity, r(1, constant than the current FDA approved Gd-chelated contrast agents. Intravenous administration of these Gd-LNP at only 3% of the recommended clinical Gd dose produced MRI signal-to-noise ratios of greater than 300 in all vasculatures. Unlike current Gd contrast agents, these Gd-LNP stably retained Gd in normal vasculature, and are eliminated predominately through the biliary, instead of the renal system. Gd-LNP did not appear to accumulate in the liver or kidney, and was eliminated completely within 24 hrs. CONCLUSIONS/SIGNIFICANCE: The novel Gd-nanoparticles provide high quality contrast enhanced vascular MRI at 97% reduced dose of Gd and do not rely on renal clearance. This new agent is likely to be suitable for patients exhibiting varying degrees of renal impairment. The simple and adaptive nanoparticle design could accommodate

  5. Susceptibility Contrast in High Field MRI of Human Brain as a Function of Tissue Iron Content

    Science.gov (United States)

    Yao, Bing; Li, Tie-Qiang; van Gelderen, Peter; Shmueli, Karin; de Zwart, Jacco A.; Duyn, Jeff H.

    2009-01-01

    Magnetic susceptibility provides an important contrast mechanism for MRI. Increasingly, susceptibility-based contrast is being exploited to investigate brain tissue microstructure and to detect abnormal levels of brain iron as these have been implicated in a variety of neuro-degenerative diseases. However, it remains unclear to what extent magnetic susceptibility-related contrast at high field relates to actual brain iron concentrations. In this study, we performed susceptibility weighted imaging as a function of field strength on healthy brains in vivo and post-mortem brain tissues at 1.5T, 3T and 7T. Iron histology was performed on the tissue samples for comparison. The calculated susceptibility-related parameters R2* and signal frequency shift in four iron-rich regions (putamen, globus pallidus, caudate, and thalamus) showed an almost linear dependence (r=0.90 for R2*; r=0.83 for phase, p<0.01) on field strength, suggesting that potential ferritin saturation effects are not relevant to susceptibility-weighted contrast for field strengths up to 7T. The R2* dependence on the putative (literature-based) iron concentration was 0.048 Hz/Tesla/ppm. The histological data from brain samples confirmed the linear dependence of R2* on field strength and showed a slope against iron concentration of 0.0099 Hz/Tesla/ppm dry-weight, which is equivalent to 0.05 Hz/Tesla/ppm wet-weight and closely matched the calculated value in vivo. These results confirm the validity of using susceptibility-weighted contrast as an indicator of iron content in iron-rich brain regions. The absence of saturation effects opens the way to exploit the benefits of MRI at high field strengths for the detection of iron distributions with high sensitivity and resolution. PMID:19027861

  6. High-contrast imaging with an arbitrary aperture: active correction of aperture discontinuities

    Science.gov (United States)

    Pueyo, Laurent; Norman, Colin; Soummer, Rémi; Perrin, Marshall; N'Diaye, Mamadou; Choquet, Elodie

    2013-09-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for future Extremely Large Telescopes, even when the pupil features a missing segment" . We show that the converging non-linear mappings resulting from our Deformable Mirror shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and strut's while not amplifying the diffraction at the aperture edges beyond the Fresnel regime and illustrate the broadband properties of ACAD in the case of the pupil configuration corresponding to the Astrophysics Focused Telescope Assets. Since details about these telescopes are not yet available to the broader astronomical community, our test case is based on a geometry mimicking the actual one, to the best of our knowledge.

  7. Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, Gregory Elijah [The Ohio State Univ., Columbus, OH (United States)

    2013-01-01

    Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the cost of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic

  8. Image Formation in High Contrast Optical Systems: The Role of Polarization

    Science.gov (United States)

    Breckinridge, James B.

    2004-01-01

    To find evidence of life in the Universe outside our solar system is one of the most compelling and visionary adventures of the 21st century. The technologies to create the telescopes and instruments that will enable this discovery are now within the grasp of mankind. Direct imaging of a very faint planet around a neighboring bright star requires high contrast or a hypercontrast optical imaging system capable of controlling unwanted radiation within the system to one part in ten to the 11th. This paper identifies several physical phenomena that affect image quality in high contrast imaging systems. Polarization induced at curved metallic surfaces and by anisotropy in the deposition process (Smith-Purcell effect) along with beam shifts introduced by the Goos-Hachen effect are discussed. A typical configuration is analyzed, and technical risk mitigation concepts are discussed.

  9. High-contrast imager for Complex Aperture Telescopes (HiCAT): 1. Testbed design

    CERN Document Server

    N'Diaye, Mamadou; Pueyo, Laurent; Elliot, Erin; Perrin, Marshall D; Wallace, J Kent; Groff, Tyler; Carlotti, Alexis; Mawet, Dimitri; Sheckells, Matt; Shaklan, Stuart; Macintosh, Bruce; Kasdin, N Jeremy; Soummer, Rémi

    2014-01-01

    Searching for nearby habitable worlds with direct imaging and spectroscopy will require a telescope large enough to provide angular resolution and sensitivity to planets around a significant sample of stars. Segmented telescopes are a compelling option to obtain such large apertures. However, these telescope designs have a complex geometry (central obstruction, support structures, segmentation) that makes high-contrast imaging more challenging. We are developing a new high-contrast imaging testbed at STScI to provide an integrated solution for wavefront control and starlight suppression on complex aperture geometries. We present our approach for the testbed optical design, which defines the surface requirements for each mirror to minimize the amplitude-induced errors from the propagation of out-of-pupil surfaces. Our approach guarantees that the testbed will not be limited by these Fresnel propagation effects, but only by the aperture geometry. This approach involves iterations between classical ray-tracing o...

  10. High contrast imaging of exoplanets on ELTs using a super-Nyquist wavefront control scheme

    CERN Document Server

    Gerard, Benjamin L

    2016-01-01

    One of the key science goals for extremely large telescopes (ELTs) is the detailed characterization of already known directly imaged exoplanets. The typical adaptive optics (AO) Nyquist control region for ELTs is ~0.4 arcseconds, placing many already known directly imaged planets outside the DM control region and not allowing any standard wavefront control scheme to remove speckles that would allow higher SNR images/spectra to be acquired. This can be fixed with super-Nyquist wavefront control (SNWFC), using a sine wave phase plate to allow for wavefront control outside the central DM Nyquist region. We demonstrate that SNWFC is feasible through a simple, deterministic, non-coronagraphic, super-Nyquist speckle nulling technique in the adaptive optics laboratory at the National Research Council of Canada. We also present results in simulation of how SNWFC using the self coherent camera (SCC) can be used for high contrast imaging. This technique could be implemented on future high contrast imaging instruments t...

  11. Multiscale modeling of high contrast brinkman equations with applications to deformable porous media

    KAUST Repository

    Brown, Donald

    2013-06-18

    Simulating porous media flows has a wide range of applications. Often, these applications involve many scales and multi-physical processes. A useful tool in the analysis of such problems in that of homogenization as an averaged description is derived circumventing the need for complicated simulation of the fine scale features. In this work, we recall recent developments of homogenization techniques in the application of flows in deformable porous media. In addition, homogenization of media with high-contrast. In particular, we recall the main ideas of the homogenization of slowly varying Stokes flow and summarize the results of [4]. We also present the ideas for extending these techniques to high-contrast deformable media [3]. These ideas are connected by the modeling of multiscale fluid-structure interaction problems. © 2013 American Society of Civil Engineers.

  12. Focal plane wave-front sensing algorithm for high-contrast imaging

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star.A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical system.We derive an algorithm for the wave-front measurement directly from 3 focal plane images.The 3 images are achieved through a deformable mirror to provide specific phases for the optics system.We introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front,which is a critical procedure for wave-front sensing.The simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically,which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.

  13. High-dynamic-range cross-correlator for shot-to-shot measurement of temporal contrast

    Science.gov (United States)

    Kon, Akira; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Ogura, Koichi; Mori, Michiaki; Sakaki, Hironao; Kando, Masaki; Kondo, Kiminori

    2017-01-01

    The temporal contrast of an ultrahigh-intensity laser is a crucial parameter for laser plasma experiments. We have developed a multichannel cross-correlator (MCCC) for single-shot measurements of the temporal contrast in a high-power laser system. The MCCC is based on third-order cross-correlation, and has four channels and independent optical delay lines. We have experimentally demonstrated that the MCCC system achieves a high dynamic range of ˜1012 and a large temporal window of ˜1 ns. Moreover, we were able to measure the shot-to-shot fluctuations of a short-prepulse intensity at -26 ps and long-pulse (amplified spontaneous emission, ASE) intensities at -30, -450, and -950 ps before the arrival of the main pulse at the interaction point.

  14. Focal plane wave-front sensin8 algorithm for high-contrast imaging

    Institute of Scientific and Technical Information of China (English)

    DOU JiangPei; REN DeQing; ZHU YongTian; ZHANG Xi

    2009-01-01

    High-contrast imaging provided by a coronagraph is critical for the direction imaging of the Earth-like planet orbiting its bright parent star. A major limitation for such direct imaging is the speckle noise that is induced from the wave-front error of an optical system. We derive an algorithm for the wave-front measurement directly from 3 focal plane images. The 3 images are achieved through a deformable mirror to provide specific phases for the optics system. We introduce an extra amplitude modulation on one deformable mirror configuration to create an uncorrelated wave-front, which is a critical procedure for wave-front sensing. The simulation shows that the reconstructed wave-front is consistent with the original wave-front theoretically, which indicates that such an algorithm is a promising technique for the wave-front measurement for the high-contrast imaging.

  15. Propagation-based phase-contrast tomography for high-resolution lung imaging with laboratory sources

    Energy Technology Data Exchange (ETDEWEB)

    Krenkel, Martin, E-mail: mkrenke@gwdg.de; Töpperwien, Mareike; Salditt, Tim, E-mail: tsaldit@gwdg.de [Institute for X-Ray Physics, University of Göttingen, 37077 Göttingen (Germany); Dullin, Christian [Institute of Diagnostic and Interventional Radiology, University Medical Center Göttingen, 37075 Göttingen (Germany); Alves, Frauke [Institute of Diagnostic and Interventional Radiology, University Medical Center Göttingen, 37075 Göttingen (Germany); Department of Haematology and Medical Oncology, Medical Center Göttingen, 37075 Göttingen (Germany); Department of Molecular Biology of Neuronal Signals, Max-Planck-Institute of Experimental Medicine, 37075 Göttingen (Germany)

    2016-03-15

    We have performed high-resolution phase-contrast tomography on whole mice with a laboratory setup. Enabled by a high-brilliance liquid-metal-jet source, we show the feasibility of propagation-based phase contrast in local tomography even in the presence of strongly absorbing surrounding tissue as it is the case in small animal imaging of the lung. We demonstrate the technique by reconstructions of the mouse lung for two different fields of view, covering the whole organ, and a zoom to the local finer structure of terminal airways and alveoli. With a resolution of a few micrometers and the wide availability of the technique, studies of larger biological samples at the cellular level become possible.

  16. High-resolution breast tomography at high energy: a feasibility study of phase contrast imaging on a whole breast

    Science.gov (United States)

    Sztrókay, A.; Diemoz, P. C.; Schlossbauer, T.; Brun, E.; Bamberg, F.; Mayr, D.; Reiser, M. F.; Bravin, A.; Coan, P.

    2012-05-01

    Previous studies on phase contrast imaging (PCI) mammography have demonstrated an enhancement of breast morphology and cancerous tissue visualization compared to conventional imaging. We show here the first results of the PCI analyser-based imaging (ABI) in computed tomography (CT) mode on whole and large (>12 cm) tumour-bearing breast tissues. We demonstrate in this work the capability of the technique of working at high x-ray energies and producing high-contrast images of large and complex specimens. One entire breast of an 80-year-old woman with invasive ductal cancer was imaged using ABI-CT with monochromatic 70 keV x-rays and an area detector of 92×92 µm2 pixel size. Sagittal slices were reconstructed from the acquired data, and compared to corresponding histological sections. Comparison with conventional absorption-based CT was also performed. Five blinded radiologists quantitatively evaluated the visual aspects of the ABI-CT images with respect to sharpness, soft tissue contrast, tissue boundaries and the discrimination of different structures/tissues. ABI-CT excellently depicted the entire 3D architecture of the breast volume by providing high-resolution and high-contrast images of the normal and cancerous breast tissues. These results are an important step in the evolution of PCI-CT towards its clinical implementation.

  17. High-contrast imaging of mycobacterium tuberculosis using third-harmonic generation microscopy

    Science.gov (United States)

    Kim, Bo Ram; Lee, Eungjang; Park, Seung-Han

    2015-07-01

    Nonlinear optical microcopy has become an important tool in investigating biomaterials due to its various advantages such as label-free imaging capabilities. In particular, it has been shown that third-harmonic generation (THG) signals can be produced at interfaces between an aqueous medium (e.g. cytoplasm, interstitial fluid) and a mineralized lipidic surface. In this work, we have demonstrated that label-free high-contrast THG images of the mycobacterium tuberculosis can be obtained using THG microscopy.

  18. Contrast validation test for retrieval method of high frequency ground wave radar

    Institute of Scientific and Technical Information of China (English)

    WANG Hailong; GUO Peifang; HAN Shuzong; XIE Qiang; ZHOU Liangming

    2005-01-01

    In this paper, on the basis of the working principles of high frequency ground wave radar for retrieval of ocean wave and sea wind elements were used to systematically study the data obtained from contrast validation test in Zhoushan sea area of Zhejiang Province on Oct. 2000, to validate the accuracy of OSMAR2000for wave and wind parameters, and to analyze the possible error caused when using OSMAR2000 to retrieve ocean parameters.

  19. High Contrast Imaging and Wavefront Control with a PIAA Coronagraph: Laboratory System Validation

    CERN Document Server

    Guyon, Olivier; Martinache, Frantz; Totems, Julien; Tanaka, Shinichiro; Matsuo, Taro; Blain, Celia; Belikov, Ruslan

    2009-01-01

    The Phase-Induced Amplitude Apodization (PIAA) coronagraph is a high performance coronagraph concept able to work at small angular separation with little loss in throughput. We present results obtained with a laboratory PIAA system including active wavefront control. The system has a 94.3% throughput (excluding coating losses) and operates in air with monochromatic light. Our testbed achieved a 2.27e-7 raw contrast between 1.65 lambda/D (inner working angle of the coronagraph configuration tested) and 4.4 lambda/D (outer working angle). Through careful calibration, we were able to separate this residual light into a dynamic coherent component (turbulence, vibrations) at 4.5e-8 contrast and a static incoherent component (ghosts and/or polarization missmatch) at 1.6e-7 contrast. Pointing errors are controlled at the 1e-3 lambda/D level using a dedicated low order wavefront sensor. While not sufficient for direct imaging of Earth-like planets from space, the 2.27e-7 raw contrast achieved already exceeds requirem...

  20. High-Performance Neural Networks for Visual Object Classification

    CERN Document Server

    Cireşan, Dan C; Masci, Jonathan; Gambardella, Luca M; Schmidhuber, Jürgen

    2011-01-01

    We present a fast, fully parameterizable GPU implementation of Convolutional Neural Network variants. Our feature extractors are neither carefully designed nor pre-wired, but rather learned in a supervised way. Our deep hierarchical architectures achieve the best published results on benchmarks for object classification (NORB, CIFAR10) and handwritten digit recognition (MNIST), with error rates of 2.53%, 19.51%, 0.35%, respectively. Deep nets trained by simple back-propagation perform better than more shallow ones. Learning is surprisingly rapid. NORB is completely trained within five epochs. Test error rates on MNIST drop to 2.42%, 0.97% and 0.48% after 1, 3 and 17 epochs, respectively.

  1. Development of an Objective High Spatial Resolution Soil Moisture Index

    Science.gov (United States)

    Zavodsky, B.; Case, J.; White, K.; Bell, J. R.

    2015-12-01

    Drought detection, analysis, and mitigation has become a key challenge for a diverse set of decision makers, including but not limited to operational weather forecasters, climatologists, agricultural interests, and water resource management. One tool that is heavily used is the United States Drought Monitor (USDM), which is derived from a complex blend of objective data and subjective analysis on a state-by-state basis using a variety of modeled and observed precipitation, soil moisture, hydrologic, and vegetation and crop health data. The NASA Short-term Prediction Research and Transition (SPoRT) Center currently runs a real-time configuration of the Noah land surface model (LSM) within the NASA Land Information System (LIS) framework. The LIS-Noah is run at 3-km resolution for local numerical weather prediction (NWP) and situational awareness applications at select NOAA/National Weather Service (NWS) forecast offices over the Continental U.S. (CONUS). To enhance the practicality of the LIS-Noah output for drought monitoring and assessing flood potential, a 30+-year soil moisture climatology has been developed in an attempt to place near real-time soil moisture values in historical context at county- and/or watershed-scale resolutions. This LIS-Noah soil moisture climatology and accompanying anomalies is intended to complement the current suite of operational products, such as the North American Land Data Assimilation System phase 2 (NLDAS-2), which are generated on a coarser-resolution grid that may not capture localized, yet important soil moisture features. Daily soil moisture histograms are used to identify the real-time soil moisture percentiles at each grid point according to the county or watershed in which the grid point resides. Spatial plots are then produced that map the percentiles as proxies to the different USDM categories. This presentation will highlight recent developments of this gridded, objective soil moisture index, comparison to subjective

  2. Mode decomposition methods for flows in high-contrast porous media. Global-local approach

    KAUST Repository

    Ghommem, Mehdi

    2013-11-01

    In this paper, we combine concepts of the generalized multiscale finite element method (GMsFEM) and mode decomposition methods to construct a robust global-local approach for model reduction of flows in high-contrast porous media. This is achieved by implementing Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) techniques on a coarse grid computed using GMsFEM. The resulting reduced-order approach enables a significant reduction in the flow problem size while accurately capturing the behavior of fully-resolved solutions. We consider a variety of high-contrast coefficients and present the corresponding numerical results to illustrate the effectiveness of the proposed technique. This paper is a continuation of our work presented in Ghommem et al. (2013) [1] where we examine the applicability of POD and DMD to derive simplified and reliable representations of flows in high-contrast porous media on fully resolved models. In the current paper, we discuss how these global model reduction approaches can be combined with local techniques to speed-up the simulations. The speed-up is due to inexpensive, while sufficiently accurate, computations of global snapshots. © 2013 Elsevier Inc.

  3. Longitudinal proton probing of ultrafast and high-contrast laser-solid interactions

    Directory of Open Access Journals (Sweden)

    Albertazzi B.

    2013-11-01

    Full Text Available We have performed an experiment aimed at measuring self-generated magnetic fields produced in solids by high electron currents following high-intensity and high contrast short-pulse laser irradiation. This was done using longitudinal high resolution proton deflectometry. The experiment was performed at the Titan-JLF laser facility with a high-power short-pulse beam (700 fs, ∼  110 J split into two beams irradiating two solid targets. One beam is used for the generation of protons and the other beam for the generation of the ultra-high currents of electrons and of the associated magnetic fields. This capability allows us to study the spatio-temporal evolution of the magnetic fields and its dependence on the laser intensity and target material.

  4. Synthesis and evaluation of a high relaxivity manganese(II)-based MRI contrast agent.

    Science.gov (United States)

    Troughton, Jeffrey S; Greenfield, Matthew T; Greenwood, Jaclyn M; Dumas, Stéphane; Wiethoff, Andrea J; Wang, Jufeng; Spiller, Marga; McMurry, Thomas J; Caravan, Peter

    2004-10-04

    The manganese(II) ion has many favorable properties that lead to its potential use as an MRI contrast agent: high spin number, long electronic relaxation time, labile water exchange. The present work describes the design, synthesis, and evaluation of a novel Mn(II) complex (MnL1) based on EDTA and also contains a moiety that noncovalently binds the complex to serum albumin, the same moiety used in the gadolinium based contrast agent MS-325. Ultrafiltration albumin binding measurements (0.1 mM, pH 7.4, 37 degrees C) indicated that the complex binds well to plasma proteins (rabbit: 96 +/- 2% bound, human: 93 +/- 2% bound), and most likely to serum albumin (rabbit: 89 +/- 2% bound, human 98 +/- 2% bound). Observed relaxivities (+/- 5%) of the complex were measured (20 MHz, 37 degrees C, 0.1 mM, pH 7.4) in HEPES buffer (r(1) = 5.8 mM(-)(1) s(-)(1)), rabbit plasma (r(1) = 51 mM(-)(1) s(-)(1)), human plasma (r(1) = 46 mM(-)(1) s(-)(1)), 4.5% rabbit serum albumin (r(1) = 47 mM(-)(1) s(-)(1)), and 4.5% human serum albumin (r(1) = 48 mM(-)(1) s(-)(1)). The water exchange rate was near optimal for an MRI contrast agent (k(298) = 2.3 +/- 0.9 x 10(8) s(-)(1)). Variable temperature NMRD profiles indicated that the high relaxivity was due to slow tumbling of the albumin-bound complex and fast exchange of the inner sphere water. The concept of a high relaxivity Mn(II)-based contrast agent was validated by imaging at 1.5 T. In a rabbit model of carotid artery injury, MnL1 clearly delineated both arteries and veins while also distinguishing between healthy tissue and regions of vessel damage.

  5. Acceleration of objects to high velocity by electromagnetic forces

    Energy Technology Data Exchange (ETDEWEB)

    Post, Richard F

    2017-02-28

    Two exemplary approaches to the acceleration of projectiles are provided. Both approaches can utilize concepts associated with the Inductrack maglev system. Either of them provides an effective means of accelerating multi-kilogram projectiles to velocities of several kilometers per second, using launchers of order 10 meters in length, thus enabling the acceleration of projectiles to high velocities by electromagnetic forces.

  6. Topography improvements in MEMS DMs for high-contrast, high-resolution imaging Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This project will develop and demonstrate an innovative microfabrication process to substantially improve the surface quality achievable in high-resolution...

  7. Arterial enhancement at abdominal CT angiography: Low- versus high-osmolality contrast media

    Energy Technology Data Exchange (ETDEWEB)

    Rouviere, O.; Berger, P.; Pangaud, C.; Lyonnet, D. [Hopital E. Herriot, Lyon (France). Dept. of Vascular and Genitourinary Radiology; Ecochard, R. [Hospices Civils de Lyon (France). Dept of Biostatistics; Fontaine, B. [Laboratoire Guerbet, Roissy (France)

    2000-09-01

    Purpose: To evaluate the effects of contrast media pharmokinetic differences on aortic enhancement at abdominal CT angiography and to determine whether these effects are of clinical relevance. Material and Methods: Two hundred and twelve patients referred for abdominal CT angiography were included in the study. All abdominal CT angiograms were performed with the same parameters (collimation 3 mm, pitch ratio 1.7, scan delay 30 s) after i.v. injection of 120 ml of contrast medium at 3 ml/s. After randomization, patients received either iobitridol 300 (low-osmolar, 300 mg I/ml), iobitridol 350 (low-osmolar, 350 mg I/ml) or ioxithalamate 350 (high-osmolar, 350 mg I/ml). The time attenuation curves obtained with the three contrast media were compared. Results: The time attenuation curve obtained with ioxithalamate 350 was not parallel to those obtained with iobitridol 300 and iobitridol 350. Mean peak enhancements obtained with iobitridol 350 and ioxithalamate 350 were not significantly different but iobitridol 350 provided higher mean peak enhancement than iobitridol 300. Mean delays of the peak enhancements were the same with the three contrast media. After peak enhancement, the decrease of aortic opacification under a selected threshold of 200 HU was significantly slower with iobitridol 350 than with iobitridol 300 and ioxithalamate 350, whereas iobitridol 300 and ioxithalamate 350 showed no significant differences. Conclusion: For a given iodine concentration, low-osmolality contrast media provide longer aortic opacification and may be recommended for CT angiography when long acquisition times are needed.

  8. High-Contrast Imaging and Wavefront Control with a PIAA Coronagraph: Laboratory System Validation

    Science.gov (United States)

    Guyon, Olivier; Pluzhnik, Eugene; Martinache, Frantz; Totems, Julien; Tanaka, Shinichiro; Matsuo, Taro; Blain, Celia; Belikov, Ruslan

    2010-01-01

    The Phase-Induced Amplitude Apodization (PIAA) coronagraph is a high-performance coronagraph concept able to work at small angular separation with little loss in throughput. We present results obtained with a laboratory PIAA system including active wavefront control. The system has a 94.3% throughput (excluding coating losses) and operates in air with monochromatic light. Our testbed achieved a 2.27 × 10-7 raw contrast between 1.65λ/D (inner working angle of the coronagraph configuration tested) and 4.4λ/D (outer working angle). Through careful calibration, we were able to separate this residual light into a dynamic coherent component (turbulence, vibrations) at 4.5 × 10-8 contrast and a static incoherent component (ghosts and/or polarization mismatch) at 1.6 × 10-7 contrast. Pointing errors are controlled at the 10-3λ/D level using a dedicated low-order wavefront sensor. While not sufficient for direct imaging of Earthlike planets from space, the 2.27 × 10-7 raw contrast achieved already exceeds requirements for a ground-based extreme adaptive optics system aimed at direct detection of more massive exoplanets. We show that over a 4 hr period, averaged wavefront errors have been controlled to the 3.5 × 10-9 contrast level. This result is particularly encouraging for ground-based extreme-AO systems relying on long-term stability and absence of static wavefront errors to recover planets much fainter than the fast boiling speckle halo.

  9. Objectively measured habitual physical activity in a highly obesogenic environment.

    Science.gov (United States)

    McLure, S A; Summerbell, C D; Reilly, J J

    2009-05-01

    While the prevalence of overweight and obesity among children continues to grow nationally, prevalence in the North-East of England is among the highest in the UK. The objective of this study was to investigate the habitual physical activity levels in a particularly obesogenic environment in the North-East of England. Eight primary schools were selected using a stratified random sampling frame ranking average deprivation levels. Participating children (n = 246, mean age 10 years) wore an accelerometer (Actigraph, GT-256) over five consecutive days (weekend plus three weekdays). Total daily moderate-to-vigorous intensity physical activity was calculated using thresholds by Puyau and colleagues. Only 7% (17/246) of children were sufficiently active. Boys were more physically active than girls (766 +/- 268 vs. 641 +/- 202 counts/min, 95% CI for the difference 63-186 cpm.). Total physical activity was not influenced significantly by deprivation levels or weight status, and there were no significant differences in physical activity between school or weekend days. The North-East of England is a recognized 'hot spot' for paediatric obesity and the present study shows that low levels of habitual physical activity are typical. Choice of accelerometry threshold affects both the apparent amount of physical activity and the ability to detect groups with particularly low levels of physical activity.

  10. Ultrasonograpy of VX-2 Liver Tumor in Rabbit Treated by High Intensity Focused Ultrasound Combined with Microbubble Contrast Agent

    Science.gov (United States)

    Xiaojuan, Ji; Jinqing, Li; Zhibiao, Wang; Jianzhong, Zou; Wenzhi, Chen; Jin, Bai

    2007-05-01

    Objective: To assess the value of sonographic appearance and to investigate the sonographic character of VX-2 liver tumor in rabbit treated by high intensity focused ultrasound (HIFU) combined with microbubble contrast agent. Methods: Forty-five rabbits bearing VX-2 tumors were randomly averagely assigned into three groups. In group A irradiation was sustained until the target region became hyperechoic. In group B therapy was stopped as soon as hyperecho occurred, and in group C irradiation time was prolonged to ensure the occurrence of coagulation necrosis. Results: Exposure duration for tumors treated purely with HIFU was the longest, whilst the use of microbubble contrast agent combined with HIFU shortened the exposure duration significantly. The gross examination and ultrasonogram coagulation necrosis area measurements correlated strongly (r=0.986,P<0.05) in the microbubble-enhanced HIFU group. Conclusion: It was feasible to enhance HIFU therapy with microbubble contrast agent. The characteristic change in the ultrasound images made it possible to assess the enhanced HIFU therapeutic efficacy in order to adjust the treatment program.

  11. Hydrogels incorporating GdDOTA: towards highly efficient dual T1/T2 MRI contrast agents.

    Science.gov (United States)

    Courant, Thomas; Roullin, Valérie Gaëlle; Cadiou, Cyril; Callewaert, Maïté; Andry, Marie Christine; Portefaix, Christophe; Hoeffel, Christine; de Goltstein, Marie Christine; Port, Marc; Laurent, Sophie; Elst, Luce Vander; Muller, Robert; Molinari, Michaël; Chuburu, Françoise

    2012-09-03

    Do not tumble dry: Gadolinium-DOTA encapsulated into polysaccharide nanoparticles (GdDOTA NPs) exhibited high relaxivity (r(1) =101.7 s(-1) mM(-1) per Gd(3+) ion at 37 °C and 20 MHz). This high relaxation rate is due to efficient Gd loading, reduced tumbling of the Gd complex, and the hydrogel nature of the nanoparticles. The efficacy of the nanoparticles as a T(1)/T(2) dual-mode contrast agent was studied in C6 cells.

  12. High sensitivity contrast enhanced optical coherence tomography for functional in vivo imaging

    Science.gov (United States)

    Liba, Orly; SoRelle, Elliott D.; Sen, Debasish; de la Zerda, Adam

    2017-02-01

    In this study, we developed and applied highly-scattering large gold nanorods (LGNRs) and custom spectral detection algorithms for high sensitivity contrast-enhanced optical coherence tomography (OCT). We were able to detect LGNRs at a concentration as low as 50 pM in blood. We used this approach for noninvasive 3D imaging of blood vessels deep in solid tumors in living mice. Additionally, we demonstrated multiplexed imaging of spectrally-distinct LGNRs that enabled observations of functional drainage in lymphatic networks. This method, which we call MOZART, provides a platform for molecular imaging and characterization of tissue noninvasively at cellular resolution.

  13. High-Performance, Reliable Object-Based NVRAM Devices

    OpenAIRE

    Kang, Yangwook

    2014-01-01

    Non-volatile memory (NVRAM) storage devices are increasingly used in both consumer and enterprise systems, providing high performance and low energy consumption compared to hard drives. Unfortunately, an inflexible block interface and multiple I/O subsystems designed for slow hard drives make it difficult to utilize NVRAMs in a portable and efficient manner. For example, in the OS storage stack, I/O workloads are reshaped and throttled to generate a small number of concurrent I/O requests, th...

  14. The Subharmonic Behavior and Thresholds of High Frequency Ultrasound Contrast Agents

    Science.gov (United States)

    Allen, John

    2016-11-01

    Ultrasound contrast agents are encapsulated micro-bubbles used for diagnostic and therapeutic biomedical ultrasound. The agents oscillate nonlinearly about their equilibrium radii upon sufficient acoustic forcing and produce unique acoustic signatures that allow them to be distinguished from scattering from the surrounding tissue. The subharmonic response occurs below the fundamental and is associated with an acoustic pressure threshold. Subharmonic imaging using ultrasound contrast agents has been established for clinical applications at standard diagnostic frequencies typically below 20 MHz. However, for emerging applications of high frequency applications (above 20 MHz) subharmonic imaging is an area of on-going research. The effects of attenuation from tissue are more significant and the characterization of agents is not as well understood. Due to specificity and control production, polymer agents are useful for high frequency applications. In this study, we highlight novel measurement techniques to measure and characterize the mechanical properties of the shell of polymer contrast agents. The definition of the subharmonic threshold is investigated with respect to mono-frequency and chirp forcing waveforms which have been used to achieve optimal subharmonic content in the backscattered signal. Time frequency analysis using the Empirical Mode Decomposition (EMD) and the Hilbert-Huang transform facilitates a more sensitive and robust methodology for characterization of subharmonic content with respect to non-stationary forcing. A new definition of the subharmonic threshold is proposed with respect to the energy content of the associated adaptive basis decomposition. Additional studies with respect to targeted agent behavior and cardiovascular disease are discussed. NIH, ONR.

  15. High-index-contrast multilayer hollow waveguides for mid-IR laser delivery

    Science.gov (United States)

    Melzer, Jeffrey E.; Kendall, Wesley Y.; Harrington, James A.

    2016-03-01

    Hollow glass waveguides (HGWs) have been researched extensively for the efficient transmission of radiation over a broad spectral range spanning from the visible region to the far-IR. One such HGW film structure consists of a metallic substrate with overlaying multilayer dielectric thin film stack of alternating high and low refractive index films. The optical properties of such multilayer thin film stacks are well established and provide a method for developing photonic bandgap fibers with exceptionally low attenuation losses at a desired wavelength. Transmission losses can be minimized in multilayer waveguides through two main approaches; either maximizing the number of alternating layer pairs or maximizing the index contrast between adjacent films. In practice, it has been shown that for liquid-phase deposition-based procedures, the former approach leads to compounding surface and interface roughness, negating the low-loss advantage of a multilayer waveguide. Thus, this research focuses on maximizing index contrast between adjacent dielectrics in an attempt to minimize the number of films required to achieve acceptable transmission characteristics both in theory and in practice. In this study, multilayer waveguides are fabricated using three dielectric materials: silver iodide, lead sulfide, and cyclic olefin copolymer. Through exploitation of their high index contrast, these materials are used to develop low-film-count multilayer waveguides designed for enhanced transmission at both Er:YAG and CO2 laser wavelengths.

  16. A High Contrast Imaging Survey of SIM Lite Planet Search Targets

    CERN Document Server

    Tanner, Angelle M; Law, Nicholas M

    2010-01-01

    With the development of extreme high contrast ground-based adaptive optics instruments and space missions aimed at detecting and characterizing Jupiter- and terrestrial-mass planets, it is critical that each target star be thoroughly vetted to determine whether it is a viable target given both the instrumental design and scientific goals of the program. With this in mind, we have conducted a high contrast imaging survey of mature AFGKM stars with the PALAO/PHARO instrument on the Palomar 200 inch telescope. The survey reached sensitivities sufficient to detect brown dwarf companions at separations of > 50 AU. The results of this survey will be utilized both by future direct imaging projects such as GPI, SPHERE and P1640 and indirect detection missions such as SIM Lite. Out of 84 targets, all but one have no close-in (0.45-1") companions and 64 (76%) have no stars at all within the 25" field-of-view. The sensitivity contrasts in the Ks passband ranged from 4.5 to 10 for this set of observations. These stars we...

  17. High-sensitive Optical Pulse-Shape Characterization using a Beating-Contrast-Measurement Technique

    CERN Document Server

    Roncin, Vincent; Millaud, Audrey; Cramer, Romain; Jaouën, Yves; Simon, Jean-Claude

    2014-01-01

    Ultrahigh-speed optical transmission technology, such as optical time domain multiplexing or optical signal processing is a key point for increasing the communication capacity. The system performances are strongly related to pulse properties. We present an original method dedicated to short pulse-shape characterization with high repetition rate using standard optical telecommunications equipments. Its principle is based on temporal measurement of the contrast produced by the beating of two delayed optical pulses in a high bandwidth photo detector. This technique returns firstly reliable information on the pulse-shape, such as pulse width, shape and pedestal. Simulation and experimental results evaluate the high-sensitivity and the high-resolution of the technique allowing the measurement of pulse extinction ratio up to 20 dB with typical timing resolution of about 100 fs. The compatibility of the technique with high repetition rate pulse measurement offers an efficient tool for short pulse analysis.

  18. Highly monodisperse low-magnetization magnetite nanocubes as simultaneous T1-T2 MRI contrast agents

    Science.gov (United States)

    Sharma, V. K.; Alipour, A.; Soran-Erdem, Z.; Aykut, Z. G.; Demir, H. V.

    2015-06-01

    We report the first study of highly monodisperse and crystalline iron oxide nanocubes with sub-nm controlled size distribution (9.7 +/- 0.5 nm in size) that achieve simultaneous contrast enhancement in both T1- and T2-weighted magnetic resonance imaging (MRI). Here, we confirmed the magnetite structure of iron oxide nanocubes by X-ray diffraction (XRD), selected area electron diffraction (SAED) pattern, optical absorption and Fourier transformed infrared (FT-IR) spectra. These magnetite nanocubes exhibit superparamagnetic and paramagnetic behavior simultaneously by virtue of their finely controlled shape and size. The magnetic measurements reveal that the magnetic moment values are favorably much lower because of the small size and cubic shape of the nanoparticles, which results in an enhanced spin canting effect. As a proof-of-concept demonstration, we showed their potential as dual contrast agents for both T1- and T2-weighted MRI via phantom studies, in vivo imaging and relaxivity measurements. Therefore, these low-magnetization magnetite nanocubes, while being non-toxic and bio-compatible, hold great promise as excellent dual-mode T1 and T2 contrast agents for MRI.We report the first study of highly monodisperse and crystalline iron oxide nanocubes with sub-nm controlled size distribution (9.7 +/- 0.5 nm in size) that achieve simultaneous contrast enhancement in both T1- and T2-weighted magnetic resonance imaging (MRI). Here, we confirmed the magnetite structure of iron oxide nanocubes by X-ray diffraction (XRD), selected area electron diffraction (SAED) pattern, optical absorption and Fourier transformed infrared (FT-IR) spectra. These magnetite nanocubes exhibit superparamagnetic and paramagnetic behavior simultaneously by virtue of their finely controlled shape and size. The magnetic measurements reveal that the magnetic moment values are favorably much lower because of the small size and cubic shape of the nanoparticles, which results in an enhanced spin

  19. High energy x-ray phase contrast CT using glancing-angle grating interferometers

    Energy Technology Data Exchange (ETDEWEB)

    Sarapata, A., E-mail: adrian.sarapata@tum.de [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 and Department of Physics and Institute of Medical Engineering, Technische Universität München, 85748 Garching (Germany); Stayman, J. W.; Siewerdsen, J. H. [Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Finkenthal, M.; Stutman, D. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Pfeiffer, F. [Department of Physics and Institute of Medical Engineering, Technische Universität München, 85748 Garching (Germany)

    2014-02-15

    Purpose: The authors present initial progress toward a clinically compatible x-ray phase contrast CT system, using glancing-angle x-ray grating interferometry to provide high contrast soft tissue images at estimated by computer simulation dose levels comparable to conventional absorption based CT. Methods: DPC-CT scans of a joint phantom and of soft tissues were performed in order to answer several important questions from a clinical setup point of view. A comparison between high and low fringe visibility systems is presented. The standard phase stepping method was compared with sliding window interlaced scanning. Using estimated dose values obtained with a Monte-Carlo code the authors studied the dependence of the phase image contrast on exposure time and dose. Results: Using a glancing angle interferometer at high x-ray energy (∼45 keV mean value) in combination with a conventional x-ray tube the authors achieved fringe visibility values of nearly 50%, never reported before. High fringe visibility is shown to be an indispensable parameter for a potential clinical scanner. Sliding window interlaced scanning proved to have higher SNRs and CNRs in a region of interest and to also be a crucial part of a low dose CT system. DPC-CT images of a soft tissue phantom at exposures in the range typical for absorption based CT of musculoskeletal extremities were obtained. Assuming a human knee as the CT target, good soft tissue phase contrast could be obtained at an estimated absorbed dose level around 8 mGy, similar to conventional CT. Conclusions: DPC-CT with glancing-angle interferometers provides improved soft tissue contrast over absorption CT even at clinically compatible dose levels (estimated by a Monte-Carlo computer simulation). Further steps in image processing, data reconstruction, and spectral matching could make the technique fully clinically compatible. Nevertheless, due to its increased scan time and complexity the technique should be thought of not as

  20. High energy x-ray phase contrast CT using glancing-angle grating interferometers

    Science.gov (United States)

    Sarapata, A.; Stayman, J. W.; Finkenthal, M.; Siewerdsen, J. H.; Pfeiffer, F.; Stutman, D.

    2014-01-01

    Purpose: The authors present initial progress toward a clinically compatible x-ray phase contrast CT system, using glancing-angle x-ray grating interferometry to provide high contrast soft tissue images at estimated by computer simulation dose levels comparable to conventional absorption based CT. Methods: DPC-CT scans of a joint phantom and of soft tissues were performed in order to answer several important questions from a clinical setup point of view. A comparison between high and low fringe visibility systems is presented. The standard phase stepping method was compared with sliding window interlaced scanning. Using estimated dose values obtained with a Monte-Carlo code the authors studied the dependence of the phase image contrast on exposure time and dose. Results: Using a glancing angle interferometer at high x-ray energy (∼45 keV mean value) in combination with a conventional x-ray tube the authors achieved fringe visibility values of nearly 50%, never reported before. High fringe visibility is shown to be an indispensable parameter for a potential clinical scanner. Sliding window interlaced scanning proved to have higher SNRs and CNRs in a region of interest and to also be a crucial part of a low dose CT system. DPC-CT images of a soft tissue phantom at exposures in the range typical for absorption based CT of musculoskeletal extremities were obtained. Assuming a human knee as the CT target, good soft tissue phase contrast could be obtained at an estimated absorbed dose level around 8 mGy, similar to conventional CT. Conclusions: DPC-CT with glancing-angle interferometers provides improved soft tissue contrast over absorption CT even at clinically compatible dose levels (estimated by a Monte-Carlo computer simulation). Further steps in image processing, data reconstruction, and spectral matching could make the technique fully clinically compatible. Nevertheless, due to its increased scan time and complexity the technique should be thought of not as

  1. Ultra-High-Contrast Laser Acceleration of Relativistic Electrons in Solid Targets

    Energy Technology Data Exchange (ETDEWEB)

    Higginson, Drew Pitney [Univ. of California, San Diego, CA (United States)

    2013-01-01

    The cone-guided fast ignition approach to Inertial Con nement Fusion requires laser-accelerated relativistic electrons to deposit kilojoules of energy within an imploded fuel core to initiate fusion burn. One obstacle to coupling electron energy into the core is the ablation of material, known as preplasma, by laser energy proceeding nanoseconds prior to the main pulse. This causes the laser-absorption surface to be pushed back hundreds of microns from the initial target surface; thus increasing the distance that electrons must travel to reach the imploded core. Previous experiments have shown an order of magnitude decrease in coupling into surrogate targets when intentionally increasing the amount of preplasma. Additionally, for electrons to deposit energy within the core, they should have kinetic energies on the order of a few MeV, as less energetic electrons will be stopped prior to the core and more energetic electrons will pass through the core without depositing much energy. Thus a quantitative understanding of the electron energy spectrum and how it responds to varied laser parameters is paramount for fast ignition. For the rst time, this dissertation quantitatively investigates the acceleration of electrons using an ultra-high-contrast laser. Ultra-high-contrast lasers reduce the laser energy that reaches the target prior to the main pulse; drastically reducing the amount of preplasma. Experiments were performed in a cone-wire geometry relevant to fast ignition. These experiments irradiated the inner-tip of a Au cone with the laser and observed electrons that passed through a Cu wire attached to the outer-tip of the cone. The total emission of K x-rays is used as a diagnostic to infer the electron energy coupled into the wire. Imaging the x-ray emission allowed an e ective path-length of electrons within the wire to be determined, which constrained the electron energy spectrum. Experiments were carried out on the ultra-high-contrast Trident laser at Los

  2. High-Speed Jet Formation after Solid Object Impact

    Science.gov (United States)

    Gekle, Stephan; Gordillo, José Manuel; van der Meer, Devaraj; Lohse, Detlef

    2009-01-01

    A circular disc hitting a water surface creates an impact crater which after collapse leads to a vigorous jet. Upon impact an axisymmetric air cavity forms and eventually pinches off in a single point halfway down the cavity. Two fast sharp-pointed jets are observed shooting up- and downwards from the closure location, which by then has turned into a stagnation point surrounded by a locally hyperbolic flow pattern. This flow, however, is not the mechanism feeding the jets. Using high-speed imaging and numerical simulations we show that jetting is fed by the local flow around the base of the jet, which is forced by the colliding cavity walls. We show how the well-known theory of a collapsing void (using a line of sinks on the symmetry axis) can be continued beyond pinch-off to obtain a new and quantitative model for jet formation which agrees well with numerical and experimental data.

  3. Objective evaluation of the correction by non-rigid registration of abdominal organ motion in low-dose 4D dynamic contrast-enhanced CT

    Science.gov (United States)

    Piper, Jim; Ikeda, Yoshihiro; Fujisawa, Yasuko; Ohno, Yoshiharu; Yoshikawa, Takeshi; O'Neil, Alison; Poole, Ian

    2012-03-01

    We objectively evaluate a straightforward registration method for correcting respiration-induced movement of abdominal organs in CT perfusion studies by measuring the distributions of alignment errors between corresponding landmark pairs. We introduce the concept and describe the advantages of using the surface-normal component of distance between pairs of corresponding landmarks selected so that their surface normal is in one of the three coordinate axis directions, and show that such landmarks can be precisely placed with respect to the surface normal. Using a large population of landmark pairs on a substantial quantity of 4D dynamic contrast-enhanced CT volume data, we quantify the average alignment errors of abdominal organs that remain uncorrected by registration.

  4. Use of Relief Contrast(®) objective to improve sperm morphometric analysis by Isas(®) casa system in the ram.

    Science.gov (United States)

    Yániz, J L; Capistrós, S; Vicente-Fiel, S; Soler, C; Núñez de Murga, M; Santolaria, P

    2013-12-01

    The aim of this study was to develop a new method for morphometric assessment of the sperm head and acrosome in the ram. Ejaculates from 10 adult males were collected using an artificial vagina. For each ejaculate, 10 semen smears were prepared, air-dried and divided (in pairs) into the following five treatment groups: (i) washed in distilled water and allowed to dry without further processing (DRY); (ii) fixed in 50% methanol (MET); (iii) fixed in 2% glutaraldehyde (GLUT); (iv) fixed and stained with Hemacolor(®) (HEM) and (v) fixed and stained with SpermBlue(®) (SB). The prepared slides were examined with a 40 × Relief Contrast(®) objective (RC) and processed with ISAS(®) commercial software. The use of RC optics increased the contrast between acrosome and sperm head, allowing capture and morphometric analysis by ISAS of sperm heads and the acrosome, even in non-stained samples. MET and GLUT groups resulted in a lower number of acceptable, that is, correctly delineated, sperm heads than those in the SB, and SB and HEM groups, respectively (p  HEM≥ MET≥ SB> DRY. When studying the proportion of the sperm head covered by the acrosome, the relation between treatments was: MET> DRY = GLUT = SB> HEM. It was concluded that the new method for sperm morphometric assessment allows the simultaneous assessment of sperm head and acrosome in the ram by the first time, even in unprocessed semen smears.

  5. Photothermal Microscopy for High Sensitivity and High Resolution Absorption Contrast Imaging of Biological Tissues

    Directory of Open Access Journals (Sweden)

    Jun Miyazaki

    2017-04-01

    Full Text Available Photothermal microscopy is useful to visualize the distribution of non-fluorescence chromoproteins in biological specimens. Here, we developed a high sensitivity and high resolution photothermal microscopy with low-cost and compact laser diodes as light sources. A new detection scheme for improving signal to noise ratio more than 4-fold is presented. It is demonstrated that spatial resolution in photothermal microscopy is up to nearly twice as high as that in the conventional widefield microscopy. Furthermore, we demonstrated the ability for distinguishing or identifying biological molecules with simultaneous muti-wavelength imaging. Simultaneous photothermal and fluorescence imaging of mouse brain tissue was conducted to visualize both neurons expressing yellow fluorescent protein and endogenous non-fluorescent chromophores.

  6. High-speed Jet Formation after Solid Object Impact

    CERN Document Server

    Gekle, Stephan; van der Meer, Devaraj; Lohse, Detlef

    2008-01-01

    A circular disc impacting on a water surface creates a remarkably vigorous jet. Upon impact an axisymmetric air cavity forms and eventually pinches off in a single point halfway down the cavity. Immediately after closure two fast sharp-pointed jets are observed shooting up- and downwards from the closure location, which by then has turned into a stagnation point surrounded by a locally hyperbolic flow pattern. This flow, however, is {\\it not} the mechanism feeding the two jets. Using high-speed imaging and numerical simulations we show that jetting is fed by the local flow around the base of the jet, which is forced by the colliding cavity walls. Based on this insight, we then show how the analytical description of a collapsing void (using a line of sinks along the axis of symmetry) can be continued beyond the time of pinch-off to obtain a quantitative model for jet formation which is in good agreement with the numerical and experimental data.

  7. Are Compact High-Velocity Clouds Extragalactic Objects?

    CERN Document Server

    Maloney, P R; Maloney, Philip R.; Putman, Mary E.

    2003-01-01

    Compact high-velocity clouds (CHVCs) are the most distant of the HVCs in the Local Group model and would have HI volume densities of order 0.0003/cm^3. Clouds with these volume densities and the observed neutral hydrogen column densities will be largely ionized, even if exposed only to the extragalactic ionizing radiation field. Here we examine the implications of this process for models of CHVCs. We have modeled the ionization structure of spherical clouds (with and without dark matter halos) for a large range of densities and sizes, appropriate to CHVCs over the range of suggested distances, exposed to the extragalactic ionizing photon flux. Constant-density cloud models in which the CHVCs are at Local Group distances have total (ionized plus neutral) gas masses roughly 20-30 times larger than the neutral gas masses, implying that the gas mass alone of the observed population of CHVCs is about 40 billion solar masses. With a realistic (10:1) dark matter to gas mass ratio, the total mass in such CHVCs is a s...

  8. Fast Neutron Tomography of Low-Z Object in High-Z Material Shielding

    Science.gov (United States)

    Babai, Ruth Weiss; Sabo-Napadensky, Iris; Bar, Doron; Mor, Ilan; Tamim, Noam; Dangendorf, Volker; Tittelmeier, Kai; Bromberger, Benjamin; Weierganz, Mathias

    The technique and first results of Fast Neutron Tomography (FNCT) experiments are presented which are performed at the accelerator facility of PTB, Germany. A high-intensity neutron beam of broad spectral distribution with an average energy of 5.5 MeV, was produced by 11.5 MeV deuterons impinging upon a thick beryllium target. The capability of FNCT for high contrast imaging of low-Z materials embedded in thick high-Z shielding materials is demonstrated, which is superior to more conventional high-energy X-ray imaging techniques. For demonstrating the method special test objects were prepared: One consisted of an assembled polyethylene cylinder with holes of various diameters and directions drilled in its surface and inner parts. The plastic phantom was inserted into lead cylinders of different thicknesses. The detector system consisted of a plastic scintillator along with a dedicated optics, image-intensifier and a CCD camera. Two scintillator screens were compared: a bulk plastic scintillator screen and a fibres optical scintillator screen. The tomographic scans were taken in two geometrical configurations: cone beam and semi-fan beam configuration. The image quality favours the semi-fan beam configuration which on the other hand is more time consuming The obtained tomographic images and a comparison of the imaging quality between the different experimental conditions will be presented.

  9. Shaped Pupil Lyot Coronagraphs: High-Contrast Solutions for Restricted Focal Planes

    CERN Document Server

    Zimmerman, Neil T; Kasdin, N Jeremy; Carlotti, Alexis; Vanderbei, Robert J

    2016-01-01

    Coronagraphs of the apodized pupil and shaped pupil varieties use the Fraunhofer diffraction properties of amplitude masks to create regions of high contrast in the vicinity of a target star. Here we present a hybrid coronagraph architecture in which a binary, hard-edged shaped pupil mask replaces the gray, smooth apodizer of the apodized pupil Lyot coronagraph (APLC). For any contrast and bandwidth goal in this configuration, as long as the prescribed region of contrast is restricted to a finite area in the image, a shaped pupil is the apodizer with the highest transmission. We relate the starlight cancellation mechanism to that of the conventional APLC. We introduce a new class of solutions in which the amplitude profile of the Lyot stop, instead of being fixed as a padded replica of the telescope aperture, is jointly optimized with the apodizer. Finally, we describe shaped pupil Lyot coronagraph (SPLC) designs for the baseline architecture of the Wide-Field Infrared Survey Telescope-Astrophysics Focused Te...

  10. X-ray phase-contrast tomography for high-spatial-resolution zebrafish muscle imaging

    Science.gov (United States)

    Vågberg, William; Larsson, Daniel H.; Li, Mei; Arner, Anders; Hertz, Hans M.

    2015-11-01

    Imaging of muscular structure with cellular or subcellular detail in whole-body animal models is of key importance for understanding muscular disease and assessing interventions. Classical histological methods for high-resolution imaging methods require excision, fixation and staining. Here we show that the three-dimensional muscular structure of unstained whole zebrafish can be imaged with sub-5 μm detail with X-ray phase-contrast tomography. Our method relies on a laboratory propagation-based phase-contrast system tailored for detection of low-contrast 4-6 μm subcellular myofibrils. The method is demonstrated on 20 days post fertilization zebrafish larvae and comparative histology confirms that we resolve individual myofibrils in the whole-body animal. X-ray imaging of healthy zebrafish show the expected structured muscle pattern while specimen with a dystrophin deficiency (sapje) displays an unstructured pattern, typical of Duchenne muscular dystrophy. The method opens up for whole-body imaging with sub-cellular detail also of other types of soft tissue and in different animal models.

  11. High contrast Kr gas jet K alpha x-ray source for high energy density physics experiments.

    Science.gov (United States)

    Kugland, N L; Neumayer, P; Döppner, T; Chung, H-K; Constantin, C G; Girard, F; Glenzer, S H; Kemp, A; Niemann, C

    2008-10-01

    A high contrast 12.6 keV Kr K alpha source has been demonstrated on the petawatt-class Titan laser facility using strongly clustering Kr gas jet targets. The contrast ratio (K alpha to continuum) is 65, with a competitive ultrashort pulse laser to x-ray conversion efficiency of 10(-5). Filtered shadowgraphy indicates that the Kr K alpha and K beta x rays are emitted from a roughly 1x2 mm(2) emission volume, making this source suitable for area backlighting and scattering. Spectral calculations indicate a typical bulk electron temperature of 50-70 eV (i.e., mean ionization state 13-16), based on the observed ratio of K alpha to K beta. Kr gas jets provide a debris-free high energy K alpha source for time-resolved diagnosis of dense matter.

  12. VIP: Vortex Image Processing Package for High-contrast Direct Imaging

    Science.gov (United States)

    Gomez Gonzalez, Carlos Alberto; Wertz, Olivier; Absil, Olivier; Christiaens, Valentin; Defrère, Denis; Mawet, Dimitri; Milli, Julien; Absil, Pierre-Antoine; Van Droogenbroeck, Marc; Cantalloube, Faustine; Hinz, Philip M.; Skemer, Andrew J.; Karlsson, Mikael; Surdej, Jean

    2017-07-01

    We present the Vortex Image Processing (VIP) library, a python package dedicated to astronomical high-contrast imaging. Our package relies on the extensive python stack of scientific libraries and aims to provide a flexible framework for high-contrast data and image processing. In this paper, we describe the capabilities of VIP related to processing image sequences acquired using the angular differential imaging (ADI) observing technique. VIP implements functionalities for building high-contrast data processing pipelines, encompassing pre- and post-processing algorithms, potential source position and flux estimation, and sensitivity curve generation. Among the reference point-spread function subtraction techniques for ADI post-processing, VIP includes several flavors of principal component analysis (PCA) based algorithms, such as annular PCA and incremental PCA algorithms capable of processing big datacubes (of several gigabytes) on a computer with limited memory. Also, we present a novel ADI algorithm based on non-negative matrix factorization, which comes from the same family of low-rank matrix approximations as PCA and provides fairly similar results. We showcase the ADI capabilities of the VIP library using a deep sequence on HR 8799 taken with the LBTI/LMIRCam and its recently commissioned L-band vortex coronagraph. Using VIP, we investigated the presence of additional companions around HR 8799 and did not find any significant additional point source beyond the four known planets. VIP is available at http://github.com/vortex-exoplanet/VIP and is accompanied with Jupyter notebook tutorials illustrating the main functionalities of the library.

  13. High contrast switching of transmission due to electrohydrodynamic effect in stacked thin systems of liquid crystals.

    Science.gov (United States)

    Serak, Svetlana V; Hrozhyk, Uladzimir; Hwang, Jeoungyeon; Tabiryan, Nelson V; Steeves, Diane; Kimball, Brian R

    2016-10-20

    We study the opportunity of using electrohydrodynamic instabilities in a nematic liquid crystal mixture with negative dielectric anisotropy for controlling laser beams. Switching between naturally transparent and diffuse light scattering states is achieved by application of low frequency, low amplitude voltages. The specifics of diffuse light scattering state depending on the orientation and thickness of the liquid crystal layer are revealed. The switching occurs on a milliseconds time scale. Combination of thin, flexible liquid crystal cells allows polarization independent, high contrast, fast switching in a broad band of visible wavelengths.

  14. Ultrafast, high resolution, phase contrast imaging of impact response with synchrotron radiation

    Directory of Open Access Journals (Sweden)

    B. J. Jensen

    2012-03-01

    Full Text Available Understanding the dynamic response of materials at extreme conditions requires diagnostics that can provide real-time, in situ, spatially resolved measurements on the nanosecond timescale. The development of methods such as phase contrast imaging (PCI typically used at synchrotron sources offer unique opportunities to examine dynamic material response. In this work, we report ultrafast, high-resolution, dynamic PCI measurements of shock compressed materials with 3 μm spatial resolution using a single 60 ps synchrotron X-ray bunch. These results firmly establish the use of PCI to examine dynamic phenomena at ns to μs timescales.

  15. Iron oxide nanorods as high-performance magnetic resonance imaging contrast agents

    Science.gov (United States)

    Mohapatra, Jeotikanta; Mitra, Arijit; Tyagi, Himanshu; Bahadur, D.; Aslam, M.

    2015-05-01

    An efficient magnetic resonance imaging (MRI) contrast agent with a high R2 relaxivity value is achieved by controlling the shape of iron oxide to rod like morphology with a length of 30-70 nm and diameter of 4-12 nm. Fe3O4 nanorods of 70 nm length, encapsulated with polyethyleneimine show a very high R2 relaxivity value of 608 mM-1 s-1. The enhanced MRI contrast of nanorods is attributed to their higher surface area and anisotropic morphology. The higher surface area induces a stronger magnetic field perturbation over a larger volume more effectively for the outer sphere protons. The shape anisotropy contribution is understood by calculating the local magnetic field of nanorods and spherical nanoparticles under an applied magnetic field (3 Tesla). As compared to spherical geometry, the induced magnetic field of a rod is stronger and hence the stronger magnetic field over a large volume leads to a higher R2 relaxivity of nanorods.An efficient magnetic resonance imaging (MRI) contrast agent with a high R2 relaxivity value is achieved by controlling the shape of iron oxide to rod like morphology with a length of 30-70 nm and diameter of 4-12 nm. Fe3O4 nanorods of 70 nm length, encapsulated with polyethyleneimine show a very high R2 relaxivity value of 608 mM-1 s-1. The enhanced MRI contrast of nanorods is attributed to their higher surface area and anisotropic morphology. The higher surface area induces a stronger magnetic field perturbation over a larger volume more effectively for the outer sphere protons. The shape anisotropy contribution is understood by calculating the local magnetic field of nanorods and spherical nanoparticles under an applied magnetic field (3 Tesla). As compared to spherical geometry, the induced magnetic field of a rod is stronger and hence the stronger magnetic field over a large volume leads to a higher R2 relaxivity of nanorods. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00055f

  16. Absorbing Backside Anti-reflecting Layers for high contrast imaging in fluid cells

    CERN Document Server

    Ausserré, Dominique; Amra, Claude; Zerrad, Myriam

    2014-01-01

    The single Anti-Reflecting (AR) layer is a classical problem in optics. When all materials are pure dielectrics, the solution is the so-called lambda/4 layer. Here we examine the case of absorbing layers between non absorbing media. We find a solution for any layer absorption coefficient provided that the light goes from the higher towards the lower index medium, which characterizes backside layers. We describe these AR absorbing (ARA) layers through generalized index and thickness conditions. They are most often ultrathin, and have important applications for high contrast imaging in fluid cells.

  17. High-Relaxivity MRI Contrast Agents: Where Coordination Chemistry Meets Medical Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Werner, Eric J.; Datta, Ankona; Jocher, Christoph J.; Raymond, Kenneth N.

    2008-01-15

    The desire to improve and expand the scope of clinical magnetic resonance imaging (MRI) has prompted the search for contrast agents of higher efficiency. The development of better agents requires consideration of the fundamental coordination chemistry of the gadolinium(III) ion and the parameters that affect its efficacy as a proton relaxation agent. In optimizing each parameter, other practical issues such as solubility and in vivo toxicity must also be addressed, making the attainment of safe, high-relaxivity agents a challenging goal. Here we present recent advances in the field, with an emphasis on the hydroxypyridinone family of Gd{sup III} chelates.

  18. High-contrast grating resonators for label-free detection of disease biomarkers

    Science.gov (United States)

    Sun, Tianbo; Kan, Shu; Marriott, Gerard; Chang-Hasnain, Connie

    2016-06-01

    A label-free optical biosensor is described that employs a silicon-based high-contrast grating (HCG) resonator with a spectral linewidth of ~500 pm that is sensitive to ligand-induced changes in surface properties. The device is used to generate thermodynamic and kinetic data on surface-attached antibodies with their respective antigens. The device can detect serum cardiac troponin I, a biomarker of cardiac disease to 100 pg/ml within 4 mins, which is faster, and as sensitive as current enzyme-linked immuno-assays for cTnI.

  19. High contrast imaging with the JWST-NIRSpec Integral Field Unit

    Science.gov (United States)

    Ygouf, Marie; Beichman, Charles A.; Hodapp, Klaus W.; Roellig, Thomas L.; NIRCam GTO

    2017-06-01

    With its integral field unit, the near-infrared spectrograph NIRSpec on JWST will allow to measure high-resolution spectra into the 3-5 μm range with an increased sensitivity over ground-based systems. This capability will considerably extend our knowledge of brown dwarfs and bright exoplanets at large separations from their host star. But because there is not any coronagraph on NIRSpec, the performance in term of contrast at close separation will be extremely limited. In this communication, we explore possibilities to further push this limitation by comparing different observing strategies and associated post-processing techniques.

  20. A cross-stacked plasmonic nanowire network for high-contrast femtosecond optical switching

    Science.gov (United States)

    Lin, Yuanhai; Zhang, Xinping; Fang, Xiaohui; Liang, Shuyan

    2016-01-01

    We report an ultrafast optical switching device constructed by stacking two layers of gold nanowires into a perpendicularly crossed network, which works at a speed faster than 280 fs with an on/off modulation depth of about 22.4%. The two stacks play different roles in enhancing consistently the optical switching performance due to their different dependence on the polarization of optical electric fields. The cross-plasmon resonance based on the interaction between the perpendicularly stacked gold nanowires and its Fano-coupling with Rayleigh anomaly is the dominant mechanism for such a high-contrast optical switching device.

  1. Polarization-independent high-index contrast grating and its fabrication tolerances

    DEFF Research Database (Denmark)

    Ikeda, Kazuhiro; Takeuchi, Kazuma; Takayose, Kentaro

    2013-01-01

    A polarization-independent, high-index contrast grating (HCG) with a single layer of cross stripes allowing simple fabrication is proposed. Since the cross stripes structure can be suspended in air by selectively wet-etching the layer below, all the layers can be grown at once when implemented...... also investigated the fabrication tolerances of the structure and found that, assuming careful optimizations of electron beam lithography for the precise grating width and dry-etching for the vertical sidewall, the suggested polarization-independent HCG can be fabricated using standard technologies....

  2. Impedance matching vertical optical waveguide couplers for dense high index contrast circuits.

    Science.gov (United States)

    Sun, Rong; Beals, Mark; Pomerene, Andrew; Cheng, Jing; Hong, Ching-Yin; Kimerling, Lionel; Michel, Jurgen

    2008-08-04

    We designed and demonstrated a compact, high-index contrast (HIC) vertical waveguide coupler for TE single mode operation with the lowest coupling loss of 0.20 dB +/- 0.05 dB at 1550 nm. Our vertical coupler consists of a pair of vertically overlapping inverse taper structures made of SOI and amorphous silicon. The vertical coupler can suppress power oscillation observed in regular directional couplers and guarantees vertical optical impedance matching with great tolerance for fabrication and refractive index variations of the waveguide materials. The coupler furthermore shows excellent broadband coupling efficiencies between 1460 nm and 1570 nm.

  3. An iterative wavefront sensing algorithm for high-contrast imaging systems *

    Institute of Scientific and Technical Information of China (English)

    Jiang-Pei Dou; De-Qing Ren; Yong-Tian Zhu

    2011-01-01

    Wavefront sensing from multiple focal plane images is a promising technique for high-contrast imaging systems. However, the wavefront error of an optics system can be properly reconstructed only when it is very small. This paper presents an iterative optimization algorithm for the direct measurement of large static wavefront errors from only one focal plane image. We first measure the intensity of the pupil image to get the pupil function of the system and acquire the aberrated image on the focal plane with a phase error that will be measured. Then we induce a dynamic phase on the tested pupil function and calculate the associated intensity of the reconstructed image on the focal plane. The algorithm will then try to minimize the intensity difference between the reconstructed image and the aberrated test image in the focal plane, where the induced phase is a variable of the optimization algorithm.The simulation shows that the wavefront of an optical system can theoretically be reconstructed with high precision, which indicates that such an iterative algorithm may be an effective way to perform wavefront sensing for high-contrast imaging systems.

  4. A note on variational multiscale methods for high-contrast heterogeneous porous media flows with rough source terms

    KAUST Repository

    Calo, Victor M.

    2011-09-01

    In this short note, we discuss variational multiscale methods for solving porous media flows in high-contrast heterogeneous media with rough source terms. Our objective is to separate, as much as possible, subgrid effects induced by the media properties from those due to heterogeneous source terms. For this reason, enriched coarse spaces designed for high-contrast multiscale problems are used to represent the effects of heterogeneities of the media. Furthermore, rough source terms are captured via auxiliary correction equations that appear in the formulation of variational multiscale methods [23]. These auxiliary equations are localized and one can use additive or multiplicative constructions for the subgrid corrections as discussed in the current paper. Our preliminary numerical results show that one can capture the effects due to both spatial heterogeneities in the coefficients (such as permeability field) and source terms (e.g., due to singular well terms) in one iteration. We test the cases for both smooth source terms and rough source terms and show that with the multiplicative correction, the numerical approximations are more accurate compared to the additive correction. © 2010 Elsevier Ltd.

  5. Objective evaluation of acute adverse events and image quality of gadolinium-based contrast agents (gadobutrol and gadobenate dimeglumine) by blinded evaluation. Pilot study.

    Science.gov (United States)

    Semelka, Richard C; Hernandes, Mateus de A; Stallings, Clifton G; Castillo, Mauricio

    2013-01-01

    The purpose was to objectively evaluate a recently FDA-approved gadolinium-based contrast agent (GBCA) in comparison to our standard GBCA for acute adverse events and image quality by blinded evaluation. Evaluation was made of a recently FDA-approved GBCA, gadobutrol (Gadavist; Bayer), in comparison to our standard GBCA, gadobenate dimeglumine (MultiHance; Bracco), in an IRB- and HIPAA-compliant study. Both the imaging technologist and patient were not aware of the brand of the GBCA used. A total of 59 magnetic resonance studies were evaluated (59 patients, 31 men, 28 women, age range of 5-85 years, mean age of 52 years). Twenty-nine studies were performed with gadobutrol (22 abdominal and 7 brain studies), and 30 studies were performed with gadobenate dimeglumine (22 abdominal and 8 brain studies). Assessment was made of acute adverse events focusing on objective observations of vomiting, hives, and moderate and severe reactions. Adequacy of enhancement was rated as poor, fair and good by one of two experienced radiologists who were blinded to the type of agent evaluated. No patient experienced acute adverse events with either agent. The target minor adverse events of vomiting or hives, and moderate and severe reactions were not observed in any patient. Adequacy of enhancement was rated as good for both agents in all patients. Objective, blinded evaluation is feasible and readily performable for the evaluation of GBCAs. This proof-of-concept study showed that both GBCAs evaluated exhibited consistent good image quality and no noteworthy adverse events. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. Bifunctional Luminomagnetic Rare-Earth Nanorods for High-Contrast Bioimaging Nanoprobes

    Science.gov (United States)

    Gupta, Bipin Kumar; Singh, Satbir; Kumar, Pawan; Lee, Yean; Kedawat, Garima; Narayanan, Tharangattu N.; Vithayathil, Sajna Antony; Ge, Liehui; Zhan, Xiaobo; Gupta, Sarika; Martí, Angel A.; Vajtai, Robert; Ajayan, Pulickel M.; Kaipparettu, Benny Abraham

    2016-09-01

    Nanoparticles exhibiting both magnetic and luminescent properties are need of the hour for many biological applications. A single compound exhibiting this combination of properties is uncommon. Herein, we report a strategy to synthesize a bifunctional luminomagnetic Gd2‑xEuxO3 (x = 0.05 to 0.5) nanorod, with a diameter of ~20 nm and length in ~0.6 μm, using hydrothermal method. Gd2O3:Eu3+ nanorods have been characterized by studying its structural, optical and magnetic properties. The advantage offered by photoluminescent imaging with Gd2O3:Eu3+ nanorods is that this ultrafine nanorod material exhibits hypersensitive intense red emission (610 nm) with good brightness (quantum yield more than 90%), which is an essential parameter for high-contrast bioimaging, especially for overcoming auto fluorescent background. The utility of luminomagnetic nanorods for biological applications in high-contrast cell imaging capability and cell toxicity to image two human breast cancer cell lines T47D and MDA-MB-231 are also evaluated. Additionally, to understand the significance of shape of the nanostructure, the photoluminescence and paramagnetic characteristic of Gd2O3:Eu3+ nanorods were compared with the spherical nanoparticles of Gd2O3:Eu3+.

  7. The maturing of high contrast imaging and starlight suppression techniques for future NASA exoplanet characterization missions

    Science.gov (United States)

    Coulter, Daniel R.; Gallagher, David B.; Siegler, Nicholas; Shaklan, Stuart; Stapelfeldt, Karl; Traub, Wesley A.

    2016-07-01

    Over 3000 exoplanets and hundreds of exoplanetary systems have been detected to date and we are now rapidly moving toward an era where the focus is shifting from detection to direct imaging and spectroscopic characterization of these new worlds and their atmospheres. NASA is currently studying several exoplanet characterization mission concepts for the 2020 Decadal Survey ranging from probe class to flagships. Detailed and comprehensive exoplanet characterization, particularly of exo-Earths, leading to assessment of habitability, or indeed detection of life, will require significant advances beyond the current state-of-the-art in high contrast imaging and starlight suppression techniques which utilize specially shaped precision optical elements to block the light from the parent star while controlling scattering and diffraction thus revealing and enabling spectroscopic study of the orbiting exoplanets in reflected light. In this paper we describe the two primary high contrast starlight suppression techniques currently being pursued by NASA: 1) coronagraphs (including several design variations) and 2) free-flying starshades. These techniques are rapidly moving from the technology development phase to the design and engineering phase and we discuss the prospects and projected performance for future exoplanet characterization missions utilizing these techniques coupled with large aperture telescopes in space.

  8. High-contrast imager for Complex Aperture Telescopes (HiCAT): testbed design and coronagraph developments

    Science.gov (United States)

    N'Diaye, Mamadou; Choquet, E.; Pueyo, L.; Elliot, E.; Perrin, M. D.; Wallace, J.; Anderson, R. E.; Carlotti, A.; Groff, T. D.; Hartig, G. F.; Kasdin, J.; Lajoie, C.; Levecq, O.; Long, C.; Macintosh, B.; Mawet, D.; Norman, C. A.; Shaklan, S.; Sheckells, M.; Sivaramakrishnan, A.; Soummer, R.

    2014-01-01

    We present a new high-contrast imaging testbed designed to provide complete solutions for wavefront sensing and control and starlight suppression with complex aperture telescopes (NASA APRA; Soummer PI). This includes geometries with central obstruction, support structures, and/or primary mirror segmentation. Complex aperture telescopes are often associated with large telescope designs, which are considered for future space missions. However, these designs makes high-contrast imaging challenging because of additional diffraction features in the point spread function. We present a novel optimization approach for the testbed optical and opto-mechanical design that minimizes the impact of both phase and amplitude errors from the wave propagation of testbed optics surface errors. This design approach allows us to define the specification for the bench optics, which we then compare to the manufactured parts. We discuss the testbed alignment and first results. We also present our coronagraph design for different testbed pupil shapes (AFTA or ATLAST), which involves a new method for the optimization of Apodized Pupil Lyot Coronagraphs (APLC).

  9. High-contrast imager for complex aperture telescopes (HiCAT): 1. testbed design

    Science.gov (United States)

    N'Diaye, Mamadou; Choquet, Elodie; Pueyo, Laurent; Elliot, Erin; Perrin, Marshall D.; Wallace, J. Kent; Groff, Tyler; Carlotti, Alexis; Mawet, Dimitri; Sheckells, Matt; Shaklan, Stuart; Macintosh, Bruce; Kasdin, N. Jeremy; Soummer, Rémi

    2013-09-01

    Searching for nearby habitable worlds with direct imaging and spectroscopy will require a telescope large enough to provide angular resolution and sensitivity to planets around a significant sample of stars. Segmented telescopes are a compelling option to obtain such large apertures. However, these telescope designs have a complex geometry (central obstruction, support structures, segmentation) that makes high-contrast imaging more challenging. We are developing a new high-contrast imaging testbed at STScI to provide an integrated solution for wavefront control and starlight suppression on complex aperture geometries. We present our approach for the testbed optical design, which defines the surface requirements for each mirror to minimize the amplitude-induced errors from the propagation of out-of-pupil surfaces. Our approach guarantees that the testbed will not be limited by these Fresnel propagation effects, but only by the aperture geometry. This approach involves iterations between classical ray-tracing optical design optimization, and end-to-end Fresnel propagation with wavefront control (e.g. Electric Field Conjugation / Stroke Minimization). The construction of the testbed is planned to start in late Fall 2013.

  10. High-contrast imaging testbed for Complex Aperture Telescopes (HiCAT) for future space missions

    Science.gov (United States)

    Choquet, E.; N'Diaye, M.; Pueyo, L.; Elliot, E.; Perrin, M. D.; Wallace, J. K.; Anderson, R.; Carlotti, A.; Groff, T.; Hartig, G.; Kasdin, N. J.; Lajoie, C.; Levecq, O.; Long, C.; Mawet, D.; Macintosh, B.; Norman, C.; Shaklan, S.; Sheckells, M.; Sivaramakrishnan, An; Soummer, R.

    2014-03-01

    Searching for nearby habitable worlds with direct imaging and spectroscopy will require a telescope large enough to provide angular resolution and sensitivity to planets around a significant sample of stars. Segmented telescopes are a compelling option to obtain such large apertures. However, these designs have a complex geometry (central obstruction, support structures, segmentation) that makes high contrast imaging challenging. We are developing a new high-contrast imaging testbed at STScI to provide an integrated solution for wavefront control and starlight suppression on complex aperture geometries. We present a novel optimization approach for the testbed optical and opto-mechanical design that minimizes the impact of both phase and amplitude errors from the wave propagation of testbed optics surface errors. This design approach allows us to define the specification for the bench optics, which we then compare to the manufactured parts. We discuss the testbed alignment and first results. We also present our coronagraph design for different testbed pupil shapes (AFTA or ATLAST), which involves a new method for the optimization of Apodized Pupil Lyot Coronagraphs (APLC).

  11. High contrast imaging at the LBT: the LEECH exoplanet imaging survey

    CERN Document Server

    Skemer, Andrew J; Esposito, Simone; Skrutskie, Michael F; Defrere, Denis; Bailey, Vanessa; Leisenring, Jarron; Apai, Daniel; Biller, Beth; Bonnefoy, Mickael; Brandner, Wolfgang; Buenzli, Esther; Close, Laird; Crepp, Justin; De Rosa, Robert J; Desidera, Silvano; Eisner, Josh; Fortney, Jonathan; Henning, Thomas; Hofmann, Karl-Heinz; Kopytova, Taisiya; Maire, Anne-Lise; Males, Jared R; Millan-Gabet, Rafael; Morzinski, Katie; Oza, Apurva; Patience, Jenny; Rajan, Abhijith; Rieke, George; Schertl, Dieter; Schlieder, Joshua; Su, Kate; Vaz, Amali; Ward-Duong, Kimberly; Weigelt, Gerd; Woodward, Charles E; Zimmerman, Neil

    2014-01-01

    In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began its $\\sim$130-night campaign from the Large Binocular Telescope (LBT) atop Mt Graham, Arizona. This survey benefits from the many technological achievements of the LBT, including two 8.4-meter mirrors on a single fixed mount, dual adaptive secondary mirrors for high Strehl performance, and a cold beam combiner to dramatically reduce the telescope's overall background emissivity. LEECH neatly complements other high-contrast planet imaging efforts by observing stars at L' (3.8 $\\mu$m), as opposed to the shorter wavelength near-infrared bands (1-2.4 $\\mu$m) of other surveys. This portion of the spectrum offers deep mass sensitivity, especially around nearby adolescent ($\\sim$0.1-1 Gyr) stars. LEECH's contrast is competitive with other extreme adaptive optics systems, while providing an alternative survey strategy. Additionally, LEECH is characterizing known exoplanetary systems with observations from 3-5$\\mu$m in preparation for JWST.

  12. Teachable, high-content analytics for live-cell, phase contrast movies.

    Science.gov (United States)

    Alworth, Samuel V; Watanabe, Hirotada; Lee, James S J

    2010-09-01

    CL-Quant is a new solution platform for broad, high-content, live-cell image analysis. Powered by novel machine learning technologies and teach-by-example interfaces, CL-Quant provides a platform for the rapid development and application of scalable, high-performance, and fully automated analytics for a broad range of live-cell microscopy imaging applications, including label-free phase contrast imaging. The authors used CL-Quant to teach off-the-shelf universal analytics, called standard recipes, for cell proliferation, wound healing, cell counting, and cell motility assays using phase contrast movies collected on the BioStation CT and BioStation IM platforms. Similar to application modules, standard recipes are intended to work robustly across a wide range of imaging conditions without requiring customization by the end user. The authors validated the performance of the standard recipes by comparing their performance with truth created manually, or by custom analytics optimized for each individual movie (and therefore yielding the best possible result for the image), and validated by independent review. The validation data show that the standard recipes' performance is comparable with the validated truth with low variation. The data validate that the CL-Quant standard recipes can provide robust results without customization for live-cell assays in broad cell types and laboratory settings.

  13. High-contrast laser acceleration of relativistic electrons in solid cone-wire targets

    Energy Technology Data Exchange (ETDEWEB)

    Higginson, D. P. [Univ. of California-San Diego, La Jolla, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Link, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sawada, H. [Univ. of California-San Diego, La Jolla, CA (United States); Wilks, S. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chawla, S. R. [Univ. of California-San Diego, La Jolla, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chen, C. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jarrott, L. C. [Univ. of California-San Diego, La Jolla, CA (United States); Flippo, K. A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); McLean, H. S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Patel, P. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Perez, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Beg, F. N. [Univ. of California-San Diego, La Jolla, CA (United States); Bartal, T. [Univ. of California-San Diego, La Jolla, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wei, M. S. [General Atomics, San Diego, CA (United States)

    2015-12-31

    Optimization of electron coupling into small solid angles is of extreme importance to applications, such as Fast Ignition, that require maximum electron energy deposition within a small volume. To optimize this coupling, we use the ultra-high-contrast Trident laser, which remains below intensity of 1011 W/cm2 until < 0.1 ns before the main pulse, while still attaining high-energy, 75 J, and peak intensity of 5 x 1019 W/cm2. Using a cone-wire target, we find that the coupling into the 40 μm diameter wire is increased by a factor of 2.7x over the low-contrast Titan laser at similar peak intensity. Full-scale simulations are used to model the laser interaction and quantitatively reproduce the experimental results. These show that increase in coupling is due to both a closer interaction, as well as the reduction of laser filamentation and self-focusing.

  14. Properties and characterization of deeply-etched, high-index-contrast ridge waveguide structures

    Science.gov (United States)

    Seibert, Christopher S.

    In order to fill the need for more densely packed photonic integrated circuits (PICs) the higher optical confinement provided by high-index-contrast (HIC) ridge waveguide (RWG) structures is required. In order to realize the high index contrast (An) between the semiconductor waveguide core and the dielectric cladding, an oxygenenhanced non-selective wet thermal oxidation (OENSO) process developed at the University of Notre Dame has been applied to the fabrication of GaAs and InP based HIC RWGs. In this work, the unique characteristics of HIC RWGs as well as the interface between the semiconductor and the native oxide have been examined. Utilizing this process, passive single mode HIC RWG devices have been fabricated which exhibit record low propagation losses. Active diode laser devices are fabricated with improved performance over previous results. For the first time these devices have been modified for junction side down bonding to heatsinks and characterized under continuous wave (CW) excitation while mounted to a temperature controlled stage. Finally, the use of the OENSO process has been extended for use in the oxidation of InGaAs lattice matched to InP. As proof of the efficacy of this process for use in this new material system, a novel native-oxide confined quantum cascade laser operating at e=5.4 im has been demonstrated.

  15. High Relaxivity Gadolinium Hydroxypyridonate-Viral Capsid Conjugates: Nano-sized MRI Contrast Agents

    Energy Technology Data Exchange (ETDEWEB)

    Meux, Susan C.; Datta, Ankona; Hooker, Jacob M.; Botta, Mauro; Francis, Matthew B.; Aime, Silvio; Raymond, Kenneth N.

    2007-08-29

    High relaxivity macromolecular contrast agents based on the conjugation of gadolinium chelates to the interior and exterior surfaces of MS2 viral capsids are assessed. The proton nuclear magnetic relaxation dispersion (NMRD) profiles of the conjugates show up to a five-fold increase in relaxivity, leading to a peak relaxivity (per Gd{sup 3+} ion) of 41.6 mM{sup -1}s{sup -1} at 30 MHz for the internally modified capsids. Modification of the exterior was achieved through conjugation to flexible lysines, while internal modification was accomplished by conjugation to relatively rigid tyrosines. Higher relaxivities were obtained for the internally modified capsids, showing that (1) there is facile diffusion of water to the interior of capsids and (2) the rigidity of the linker attaching the complex to the macromolecule is important for obtaining high relaxivity enhancements. The viral capsid conjugated gadolinium hydroxypyridonate complexes appear to possess two inner-sphere water molecules (q = 2) and the NMRD fittings highlight the differences in the local motion for the internal ({tau}{sub RI} = 440 ps) and external ({tau}{sub RI} = 310 ps) conjugates. These results indicate that there are significant advantages of using the internal surface of the capsids for contrast agent attachment, leaving the exterior surface available for the installation of tissue targeting groups.

  16. High-resolution wide-field imaging of perfused capillaries without the use of contrast agent

    Directory of Open Access Journals (Sweden)

    Nelson DA

    2011-08-01

    Full Text Available Darin A Nelson1, Zvia Burgansky-Eliash1,2, Hila Barash1, Anat Loewenstein3, Adiel Barak4, Elisha Bartov2, Tali Rock2, Amiram Grinvald51Optical Imaging Ltd, Rehovot, Israel; 2Department of Ophthalmology, Edith Wolfson Medical Center, Holon, Israel; 3Department of Ophthalmology, Tel Aviv Medical Center & Sackler Faculty of Medicine, Tel Aviv University, Israel; 4Department of Ophthalmology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel; 5Department of Neurobiology, The Weizmann Institute of Science, Rehovot, IsraelPurpose: Assessment of capillary abnormalities facilitates early diagnosis, treatment, and follow-up of common retinal pathologies. Injected contrast agents like fluorescein are widely used to image retinal capillaries, but this highly effective procedure has a few disadvantages, such as untoward side effects, inconvenience of injection, and brevity of the time window for clear visualization. The retinal function imager (RFI is a tool for monitoring retinal functions, such as blood velocity and oximetry, based on intrinsic signals. Here we describe the clinical use of hemoglobin in red blood cells (RBCs as an intrinsic motion-contrast agent in the generation of detailed noninvasive capillary-perfusion maps (nCPMs.Patients and methods: Multiple series of nCPM images were acquired from 130 patients with diabetic retinopathy, vein occlusion, central serous retinopathy, age-related macular degeneration, or metabolic syndrome, as well as from 37 healthy subjects. After registration, pixel value distribution parameters were analyzed to locate RBC motion.Results: The RFI yielded nCPMs demonstrating microvascular morphology including capillaries in exquisite detail. Maps from the same subject were highly reproducible in repeated measurements, in as much detail and often better than that revealed by the very best fluorescein angiography. In patients, neovascularization and capillary nonperfusion areas were clearly observed. Foveal avascular

  17. Recursive Starlight and Bias Estimation for High-Contrast Imaging with an Extended Kalman Filter

    CERN Document Server

    Riggs, A J Eldorado; Groff, Tyler D

    2016-01-01

    For imaging faint exoplanets and disks, a coronagraph-equipped observatory needs focal plane wavefront correction to recover high contrast. The most efficient correction methods iteratively estimate the stellar electric field and suppress it with active optics. The estimation requires several images from the science camera per iteration. To maximize the science yield, it is desirable both to have fast wavefront correction and to utilize all the correction images for science target detection. Exoplanets and disks are incoherent with their stars, so a nonlinear estimator is required to estimate both the incoherent intensity and the stellar electric field. Such techniques assume a high level of stability found only on space-based observatories and possibly ground-based telescopes with extreme adaptive optics. In this paper, we implement a nonlinear estimator, the iterated extended Kalman filter (IEKF), to enable fast wavefront correction and a recursive, nearly-optimal estimate of the incoherent light. In Prince...

  18. Mode splitting in high-index-contrast grating with mini-scale finite size.

    Science.gov (United States)

    Wang, Zhixin; Ni, Liangfu; Zhang, Haiyang; Zhang, Hanxing; Jin, Jicheng; Peng, Chao; Hu, Weiwei

    2016-08-15

    The mode-splitting phenomenon within finite-size, mini-scale high-index-contrast gratings (HCGs) has been investigated theoretically and experimentally. The high-Q resonance splits into a series of in-plane modes due to the confinement of boundaries but can still survive even on a mini-scale footprint. Q factors up to ∼3300 and ∼2200 have been observed for the HCGs with footprints that are only 55  μm×300  μm and 27.5  μm×300  μm, which would be promising for realizing optical communication and sensing applications with compact footprint.

  19. Starlight Demonstration of the Dragonfly Instrument: an Integrated Photonic Pupil Remapping Interferometer for High Contrast Imaging

    CERN Document Server

    Jovanovic, N; Norris, B; Gross, S; Stewart, P; Charles, N; Lacour, S; Ams, M; Lawrence, J S; Lehmann, A; Niel, C; Robertson, J G; Marshall, G D; Ireland, M; Fuerbach, A; Withford, M J

    2012-01-01

    In the two decades since the first extra-solar planet was discovered, the detection and characterization of extra-solar planets has become one of the key endeavors in all of modern science. Recently direct detection techniques such as interferometry or coronography have received growing attention because they reveal the population of exoplanets inaccessible to Doppler or transit techniques, and moreover they allow the faint signal from the planet itself to be investigated. Next-generation stellar interferometers are increasingly incorporating photonic technologies due to the increase in fidelity of the data generated. Here, we report the design, construction and commissioning of a new high contrast imager; the integrated pupil-remapping interferometer; an instrument we expect will find application in the detection of young faint companions in the nearest star-forming regions. The laboratory characterisation of the instrument demonstrated high visibility fringes on all interferometer baselines in addition to s...

  20. Mathematical and computational modeling of a ferrofluid deformable mirror for high-contrast imaging

    Science.gov (United States)

    Lemmer, Aaron J.; Griffiths, Ian M.; Groff, Tyler D.; Rousing, Andreas W.; Kasdin, N. Jeremy

    2016-07-01

    Deformable mirrors (DMs) are an enabling and mission-critical technology in any coronagraphic instrument designed to directly image exoplanets. A new ferro fluid deformable mirror technology for high-contrast imaging is currently under development at Princeton, featuring a flexible optical surface manipulated by the local electromagnetic and global hydraulic actuation of a reservoir of ferro fluid. The ferro fluid DM is designed to prioritize high optical surface quality, high-precision/low-stroke actuation, and excellent low-spatial-frequency performance - capabilities that meet the unique demands of high-contrast coronagraphy in a space-based platform. To this end, the ferro-fluid medium continuously supports the DM face sheet, a configuration that eliminates actuator print-through (or, quilting) by decoupling the nominal surface figure from the geometry of the actuator array. The global pressure control allows independent focus actuation. In this paper we describe an analytical model for the quasi-static deformation response of the DM face sheet to both magnetic and pressure actuation. These modeling efforts serve to identify the key design parameters and quantify their contributions to the DM response, model the relationship between actuation commands and DM surface-profile response, and predict performance metrics such as achievable spatial resolution and stroke precision for specific actuator configurations. Our theoretical approach addresses the complexity of the boundary conditions associated with mechanical mounting of the face sheet, and makes use of asymptotic approximations by leveraging the three distinct length scales in the problem - namely, the low-stroke ( nm) actuation, face sheet thickness ( mm), and mirror diameter (cm). In addition to describing the theoretical treatment, we report the progress of computational multi physics simulations which will be useful in improving the model fidelity and in drawing conclusions to improve the design.

  1. High-contrast gratings for long-wavelength laser integration on silicon

    Science.gov (United States)

    Sciancalepore, Corrado; Descos, Antoine; Bordel, Damien; Duprez, Hélène; Letartre, Xavier; Menezo, Sylvie; Ben Bakir, Badhise

    2014-02-01

    Silicon photonics is increasingly considered as the most promising way-out to the relentless growth of data traffic in today's telecommunications infrastructures, driving an increase in transmission rates and computing capabilities. This is in fact challenging the intrinsic limit of copper-based, short-reach interconnects and microelectronic circuits in data centers and server architectures to offer enough modulation bandwidth at reasonable power dissipation. In the context of the heterogeneous integration of III-V direct-bandgap materials on silicon, optics with high-contrast metastructures enables the efficient implementation of optical functions such as laser feedback, input/output (I/O) to active/passive components, and optical filtering, while heterogeneous integration of III-V layers provides sufficient optical gain, resulting in silicon-integrated laser sources. The latest ensure reduced packaging costs and reduced footprint for the optical transceivers, a key point for the short reach communications. The invited talk will introduce the audience to the latest breakthroughs concerning the use of high-contrast gratings (HCGs) for the integration of III-V-on-Si verticalcavity surface-emitting lasers (VCSELs) as well as Fabry-Perot edge-emitters (EELs) in the main telecom band around 1.55 μm. The strong near-field mode overlap within HCG mirrors can be exploited to implement unique optical functions such as dense wavelength division multiplexing (DWDM): a 16-λ100-GHz-spaced channels VCSEL array is demonstrated. On the other hand, high fabrication yields obtained via molecular wafer bonding of III-V alloys on silicon-on-insulator (SOI) conjugate excellent device performances with cost-effective high-throughput production, supporting industrial needs for a rapid research-to-market transfer.

  2. Renal Arteries: Isotropic, High-Spatial-Resolution, Unenhanced MR Angiography with Three-dimensional Radial Phase Contrast1

    Science.gov (United States)

    Lum, Darren P.; Johnson, Kevin M.; Landgraf, Benjamin R.; Bley, Thorsten A.; Reeder, Scott B.; Schiebler, Mark L.; Grist, Thomas M.; Wieben, Oliver

    2011-01-01

    Purpose: To prospectively compare a new three-dimensional (3D) radial phase-contrast magnetic resonance (MR) angiographic method with contrast material–enhanced MR angiography for anatomic assessment of the renal arteries. Materials and Methods: An institutional review board approved this prospective HIPAA-compliant study. Informed consent was obtained. Twenty-seven subjects (mean age, 52.6 years ± 20.5 [standard deviation]) were imaged with respiratory-gated phase-contrast vastly undersampled isotropic projection reconstruction (VIPR) prior to contrast-enhanced MR angiographic acquisition with a 3.0-T clinical system. The imaging duration for phase-contrast VIPR was 10 minutes and provided magnitude and complex difference (“angiographic”) images with 3D volumetric (320 mm) coverage and isotropic high spatial resolution (1.25 mm3). Quantitative analysis consisted of comparing vessel diameters between the two techniques. Qualitative assessment included evaluation of the phase-contrast VIPR and contrast-enhanced MR angiographic techniques for artifacts, noise, and image quality. Bland-Altman analysis was used for comparison of quantitative measurements, and the Wilcoxon signed rank test was used for comparison of qualitative scores. Results: Phase-contrast VIPR images were successfully acquired in all subjects. The vessel diameters measured with phase-contrast VIPR were slightly greater than those measured with contrast-enhanced MR angiography (mean bias = 0.09 mm). Differences in mean artifact, quality scores for the proximal renal arteries, and overall image quality scores between phase-contrast VIPR and contrast-enhanced MR angiographic techniques were not statistically significant (P = .31 and .29, .27 and .39, and .43 and .69 for readers 1 and 2, respectively). The quality scores for the segmental renal arteries were higher for phase-contrast VIPR than for contrast-enhanced MR angiography (P contrast-enhanced MR angiography and were statistically

  3. Tobacco mosaic virus rods and spheres as supramolecular high-relaxivity MRI contrast agents

    Science.gov (United States)

    Bruckman, Michael A.; Hern, Stephen; Jiang, Kai; Flask, Chris A.; Yu, Xin; Steinmetz, Nicole F.

    2013-01-01

    To compensate for the low sensitivity of magnetic resonance imaging (MRI), nanoparticles have been developed to deliver high payloads of contrast agents to sites of disease. Here, we report the development of supramolecular MRI contrast agents using the plant viral nanoparticle tobacco mosaic virus (TMV). Rod-shaped TMV nanoparticles measuring 300×18 nm were loaded with up to 3,500 or 2,000 chelated paramagnetic gadolinium (III) ions selectively at the interior (iGd-TMV) or exterior (eGd-TMV) surface, respectively. Spatial control is achieved through targeting either tyrosine or carboxylic acid side chains on the solvent exposed exterior or interior TMV surface. The ionic T1 relaxivity per Gd ion (at 60 MHz) increases from 4.9 mM−1s−1 for free Gd(DOTA) to 18.4 mM−1s−1 for eGd-TMV and 10.7 mM−1s−1 for iGd-TMV. This equates to T1 values of ~ 30,000 mM−1s−1 and ~ 35,000 mM−1s−1 per eGd-TMV and iGd-TMV nanoparticle. Further, we show that interior-labeled TMV rods can undergo thermal transition to form 170 nm-sized spherical nanoparticles containing ~ 25,000 Gd chelates and a per particle relaxivity of almost 400,000 mM−1s−1 (15.2 mM−1s−1 per Gd). This work lays the foundation for the use of TMV as a contrast agent for MRI. PMID:23589767

  4. High Resolutions Obtained by Microspheres, and Phase Contrast Microscope with a Microsphere

    CERN Document Server

    Ben-Aryeh, Y

    2015-01-01

    High resolutions obtained in optical systems with microspheres are studied by Helmholtz equation and boundary conditions for the EM fields. The large lateral spatial wave vectors of the evanescent waves, which include information on the fine structures of the object, are converted at the microsphere surface to smaller spatial wave vectors. Due to reduction in the magnitudes of these spatial wave vectors a part of the EM waves propagate in the microsphere without decay, but preserve the fine structures which can be recovered in the image plane. A new method for measuring phase objects, like those of semi-transparent biological tissues, with high resolutions is described by an optical system composed of a combination of the microsphere with an interferometer.

  5. Combining high-dispersion spectroscopy (HDS) with high contrast imaging (HCI): Probing rocky planets around our nearest neighbors

    CERN Document Server

    Snellen, Ignas; Birkby, Jayne; Brandl, Bernhard; Brogi, Matteo; Keller, Christoph; Kenworthy, Matthew; Schwarz, Henriette; Stuik, Remko

    2015-01-01

    Aims: In this work, we discuss a way to combine High Dispersion Spectroscopy and High Contrast Imaging (HDS+HCI). For a planet located at a resolvable angular distance from its host star, the starlight can be reduced up to several orders of magnitude using adaptive optics and/or coronography. In addition, the remaining starlight can be filtered out using high-dispersion spectroscopy, utilizing the significantly different (or Doppler shifted) high-dispersion spectra of the planet and star. In this way, HDS+HCI can in principle reach contrast limits of ~1e-5 x 1e-5, although in practice this will be limited by photon noise and/or sky-background. Methods: We present simulations of HDS+HCI observations with the E-ELT, both probing thermal emission from a planet at infrared wavelengths, and starlight reflected off a planet atmosphere at optical wavelengths. For the infrared simulations we use the baseline parameters of the E-ELT and METIS instrument, with the latter combining extreme adaptive optics with an R=100,...

  6. High-Contrast 3.8 Micron Imaging of the Brown Dwarf/Planet-Mass Companion to GJ 758

    Science.gov (United States)

    Currie, Thayne M.; Bailey, Vanessa; Fabrycky, Daniel; Murray-Clay, Ruth; Rodigas, Timothy; Hinz, Phil

    2011-01-01

    We present L' band (3.8 Micron) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one - possibly two - faint comoving companions (GJ 7588 and "C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \\textit{possible} detection of the object identified by Thalmann et al as "GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 7588 has a H-L' color redder than nearly all known L-T8 dwarfs. 8ased on comparisons with the COND evolutionary models, GJ 7588 has Te approx. 560 K (+150 K, -90 K) and a mass ranging from approx.10-20 Mj if it is approx.1 Gyr old to approx. 25-40 Mj if it is 8.7 Gyr old. GJ 7588 is likely in a highly eccentric orbit, e approx. 0.73 (+0.12,-0.21), with a semimajor axis of approx. 44 AU (+32 AU, -14 AU). Though GJ 7588 is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.

  7. New circumstellar structure in the T Tauri system. A near-infrared high-contrast imaging study

    Science.gov (United States)

    Kasper, M.; Santhakumari, K. K. R.; Herbst, T. M.; Köhler, R.

    2016-09-01

    Aims: The immediate vicinity of T Tauri was observed with the new high-contrast imaging instrument SPHERE at the VLT to resolve remaining mysteries of the system, such as the putative small edge-on disk around T Tauri Sa and the assignment of the complex outflow patterns to the individual stars. Methods: We used SPHERE IRDIS narrow-band classical imaging in Paβ, Brγ, and the ν = 1-0 S(1) line of H2, as well as in the nearby continua to obtain high spatial resolution and high-contrast images over the near-infrared spectral range. Line maps were created by subtracting the nearby continuum. We also reanalyzed coronagraphic data taken with SPHERE's integral field spectrograph in J- and H-band with the goal of obtaining a precise extinction estimate to T Tauri Sb, and of verifying the recently reported claim of another stellar or substellar object in the system. Results: A previously unknown coiling structure is observed southwest of the stars in reflected light, which points to the vicinity of T Tauri N. We map the circumbinary emission from T Tauri S in J- and H-band scattered light for the first time, showing a morphology that differs significantly from that observed in K-band. Molecular Hydrogen emission is found southwest of the stars, near the coiling structure. We also detect the H2 emitting region T Tauri NW. The motion of T Tauri NW with respect to T Tauri N and S between previous images and our 2014 data provides strong evidence that the southeast-northwest outflow triggering T Tauri NW is likely to be associated with T Tauri S. We also present accurate relative photometry of the stars, which confirms that T Tauri Sa is brightening again. Our analysis rules out the presence of the recently proposed companion to T Tauri N with high confidence.

  8. High-contrast imaging of ɛ Eridani with ground-based instruments

    Science.gov (United States)

    Mizuki, T.; Yamada, T.; Carson, J. C.; Kuzuhara, M.; Nakagawa, T.; Nishikawa, J.; Sitko, M. L.; Kudo, T.; Kusakabe, N.; Hashimoto, J.; Abe, L.; Brander, W.; Brandt, T. D.; Egner, S.; Feldt, M.; Goto, M.; Grady, C. A.; Guyon, O.; Hayano, Y.; Hayashi, M.; Hayashi, S. S.; Henning, T.; Hodapp, K. W.; Ishii, M.; Iye, M.; Janson, M.; Kandori, R.; Knapp, G. R.; Kwon, J.; Matsuo, T.; McElwain, M. W.; Miyama, S.; Morino, J.; Moro-Martin, A.; Nishimura, T.; Pyo, T.; Serabyn, E.; Suenaga, T.; Suto, H.; Suzuki, R.; Takahashi, Y. H.; Takami, M.; Takato, N.; Terada, H.; Thalmann, C.; Turner, E. L.; Watanabe, M.; Wisniewski, J.; Takami, H.; Usuda, T.; Tamura, M.

    2016-11-01

    ɛ Eridani is one of the nearest solar-type stars. Its proximity and relatively young age allow high-contrast imaging observations to achieve sensitivities to planets at narrow separations down to an inner radius of 5 AU. Previous observational studies of the system report a dust disk with asymmetric morphology as well as a giant planet with large orbital eccentricity, which may require another massive companion to induce the peculiar morphology and to enhance the large orbital eccentricity. In this paper, we report results from deep high-contrastimaging observations to detect the previously reported planet and search for other unseen less massive companions with Subaru/HiCIAO, Gemini-South/NICI, and VLT/NACO. No positive detection was made, but high-contrast measurements with the CH4S narrow-band filter of HiCIAO achieved sensitivities at 14.7 mag differential magnitude level, at an angular separation of 1.0″. In terms of planetary mass, as determined by cooling evolutionary models, the highest sensitivities were achieved by the Lp broad-band filter of NACO, resulting in sensitivities corresponding to 1.8, 2.8, and 4.5 Mjup at the projected separation of 3 AU, if 200, 400, and 800 Myr is assumed for the age of the system, respectively. We also discuss origins of the dust disk from the detection sensitivity in the planetary mass and find that a less massive eccentric planet is preferred for disk stirring, which is consistent with the orbital parameters of ɛ Eri b claimed from the previous long-term radial velocity monitoring.

  9. Palladium nanosheets as highly stable and effective contrast agents for in vivo photoacoustic molecular imaging

    Science.gov (United States)

    Nie, Liming; Chen, Mei; Sun, Xiaolian; Rong, Pengfei; Zheng, Nanfeng; Chen, Xiaoyuan

    2014-01-01

    A stable and efficient contrast agent is highly desirable for photoacoustic (PA) imaging applications. Recently gold nanostructures have been widely reported and studied for PA imaging and photothermal therapy. However, the structures of the nonspherical gold nanoparticles are easily destroyed after laser irradiation and thus may fail to complete the intended tasks. In this study, we propose to apply palladium nanosheets (PNSs), with strong optical absorption in the near-infrared (NIR) region, as a new class of exogenous PA contrast agents. PA and ultrasound (US) images were acquired sequentially by a portable and fast photoacoustic tomography (PAT) system with a hand-held transducer. Significant and long-lasting imaging enhancement in SCC7 head and neck squamous cell carcinoma was successfully observed in mice by PAT over time after tail vein administration of PNSs. The morphology and functional perfusion of the tumors were delineated in PA images due to the nanoparticle accumulation. PAT of the main organs was also conducted ex vivo to trace the fate of PNSs, which was further validated by inductively coupled plasma atomic emission spectrometry (ICP-AES). No obvious toxic effect was observed by in vitro MTT assay and ex vivo histological examination 7 days after PNS administration. With the combination of a portable imaging instrument and signal specificity, PNSs might be applied as stable and effective agents for photoacoustic cancer detection, diagnosis and treatment guidance.

  10. Applications of focused MeV light ion beams for high resolution channeling contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Jamieson, D.N.; Breese, M.B.H.; Prawer, S.; Dooley, S.P.; Allen, M.G.; Bettiol, A.A.; Saint, A. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Ryan, C.G. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1993-12-31

    The technique of Nuclear Microscopy, utilizing a focused ion probe of typically MeV H{sup +} or He{sup +} ions, can produce images where the contrast depends on typical Ion Beam Analysis (lBA) processes. The probe forming lens system usually utilizes strong focusing, precision magnetic quadrupole lenses and the probe is scanned over the target to produce images. Originally, this imaging technique was developed to utilize backscattered particles with incident beam currents typically of a few nA, and the technique became known as Channeling Contrast Microscopy (CCM). Recently, the technique has been developed further to utilize the forward scattering of ions incident along a major crystal axis in thin crystals. This technique is known as Channeling Scanning Transmission Ion Microscopy (CSTIM). Since nearly all incident ions are detected, CSTIM is highly efficient and very low beam currents are sufficient for imaging, typically as low as a few fA. This allows probes as small as 50 nm to be used. In this paper we briefly review the recent applications of these emerging techniques to a variety of single crystal materials (authors). 13 refs., 5 figs.

  11. Characterization of the gaseous companion {\\kappa} Andromedae b: New Keck and LBTI high-contrast observations

    CERN Document Server

    Bonnefoy, M; Marleau, G -D; Schlieder, J E; Wisniewski, J; Carson, J; Covey, K R; Henning, T; Biller, B; Hinz, P; Klahr, H; Boyer, A N Marsh; Zimmerman, N; Janson, M; McElwain, M; Mordasini, C; Skemer, A; Bailey, V; Defrère, D; Thalmann, C; Skrutskie, M; Allard, F; Homeier, D; Tamura, M; Feldt, M; Cumming, A; Grady, C; Brandner, W; Kandori, R; Kuzuhara, M; Fukagawa, M; Kwon, J; Kudo, T; Hashimoto, J; Kusakabe, N; Abe, L; Brandt, T; Egner, S; Guyon, O; Hayano, Y; Hayashi, M; Hayashi, S; Hodapp, K; Ishii, M; Iye, M; Knapp, G; Matsuo, T; Mede, K; Miyama, M; Morino, J -I; Moro-Martin, A; Nishimura, T; Pyo, T; Serabyn, E; Suenaga, T; Suto, H; Suzuki, R; Takahashi,; Takami, M; Takato, N; Terada, H; Tomono, D; Turner, E; Watanabe, M; Yamada, T; Takami, H; Usuda, T

    2013-01-01

    We previously reported the direct detection of a low mass companion at a projected separation of 55+-2 AU around the B9 type star {\\kappa} Andromedae. The properties of the system (mass ratio, separation) make it a benchmark for the understanding of the formation and evolution of gas giant planets and brown dwarfs on wide-orbits. We present new angular differential imaging (ADI) images of the Kappa Andromedae system at 2.146 (Ks), 3.776 (L'), 4.052 (NB 4.05) and 4.78 {\\mu}m (M') obtained with Keck/NIRC2 and LBTI/LMIRCam, as well as more accurate near-infrared photometry of the star with the MIMIR instrument. We derive a more accurate J = 15.86 +- 0.21, H = 14.95 +- 0.13, Ks = 14.32 +- 0.09 mag for {\\kappa} And b. We redetect the companion in all our high contrast observations. We confirm previous contrasts obtained at Ks and L' band. We derive NB 4.05 = 13.0 +- 0.2 and M' = 13.3 +- 0.3 mag and estimate Log10(L/Lsun) = -3.76 +- 0.06. We build the 1-5 microns spectral energy distribution of the companion and co...

  12. High-contrast Imaging with Spitzer: Deep Observations of Vega, Fomalhaut, and epsilon Eridani

    CERN Document Server

    Janson, Markus; Carson, Joseph C; Thalmann, Christian; Lafreniere, David; Amara, Adam

    2014-01-01

    Stars with debris disks are intriguing targets for direct imaging exoplanet searches, both due to previous detections of wide planets in debris disk systems, as well as commonly existing morphological features in the disks themselves that may be indicative of a planetary influence. Here we present observations of three of the most nearby young stars, that are also known to host massive debris disks: Vega, Fomalhaut, and eps Eri. The Spitzer Space Telescope is used at a range of orientation angles for each star, in order to supply a deep contrast through angular differential imaging combined with high-contrast algorithms. The observations provide the opportunity to probe substantially colder bound planets (120--330 K) than is possible with any other technique or instrument. For Vega, some apparently very red candidate point sources detected in the 4.5 micron image remain to be tested for common proper motion. The images are sensitive to ~2 Mjup companions at 150 AU in this system. The observations presented he...

  13. PSF reconstruction for NICI, the high-contrast coronagraphicimager of GEMINI observatory

    Science.gov (United States)

    Hartung, M.; Gratadour, D.; Chun, M.; Hayward, T.

    2011-09-01

    It is more than a decade ago that PSF reconstruction from wavefront sensor (WFS) data has been described by Veran et al. (JOSA A, 1997) and successfully demonstrated at CFHT/PUEO. Nevertheless, even though adaptive optics (AO) has evolved into a mature technology, no breakthrough has been reached yet in terms of a broad use of WFS estimated PSFs in astronomical image data reduction. Reasons for this are certainly the lack of easy access to the needed AO data as well as the automatic supply of reconstructed PSFs along with the science exposures to eventually give the astronomical community a chance to exploit its potential. The key information are the covariance matrices of the WFS signal and the DM voltages in sync with the science exposures. Without active interaction from the user side with the observatory, we intend to automatically provide the user with these AO data together with the retrieved PSF for every taken science exposure. Typical applications for a WFS retrieved PSF are photometry and image sharpening by deconvolution. For the high-contrast imager NICI, the reconstructed PSF will be of particular use providing a fixed reference point to derive planet detection contrast curves completely in sync with the science exposure. We will compare how well the WFS estimated PSF matches the science image PSF at various AO guide stars, and will study the impact of system modeling errors.

  14. A High-precision Technique to Correct for Residual Atmospheric Dispersion in High-contrast Imaging Systems

    Science.gov (United States)

    Pathak, P.; Guyon, O.; Jovanovic, N.; Lozi, J.; Martinache, F.; Minowa, Y.; Kudo, T.; Takami, H.; Hayano, Y.; Narita, N.

    2016-12-01

    Direct detection and spectroscopy of exoplanets requires high-contrast imaging. For habitable exoplanets in particular, located at a small angular separation from the host star, it is crucial to employ small inner working angle (IWA) coronagraphs that efficiently suppress starlight. These coronagraphs, in turn, require careful control of the wavefront that directly impacts their performance. For ground-based telescopes, atmospheric refraction is also an important factor, since it results in a smearing of the point-spread function (PSF), that can no longer be efficiently suppressed by the coronagraph. Traditionally, atmospheric refraction is compensated for by an atmospheric dispersion compensator (ADC). ADC control relies on an a priori model of the atmosphere whose parameters are solely based on the pointing of the telescope, which can result in imperfect compensation. For a high-contrast instrument like the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system, which employs very small IWA coronagraphs, refraction-induced smearing of the PSF has to be less than 1 mas in the science band for optimum performance. In this paper, we present the first on-sky measurement and correction of residual atmospheric dispersion. Atmospheric dispersion is measured from the science image directly, using an adaptive grid of artificially introduced speckles as a diagnostic to feedback to the telescope’s ADC. With our current setup, we were able to reduce the initial residual atmospheric dispersion from 18.8 mas to 4.2 in broadband light (y- to H-band) and to 1.4 mas in the H-band only. This work is particularly relevant to the upcoming extremely large telescopes (ELTs) that will require fine control of their ADC to reach their full high-contrast imaging potential.

  15. Low-Cost High-Precision PIAA Optics for High Contrast Imaging with Exo-Planet Coronagraphs

    Science.gov (United States)

    Balasubramanian, Kunjithapatham; Shaklan, Stuart B.; Pueyo, Laurent; Wilson, Daniel W.; Guyon, Olivier

    2010-01-01

    PIAA optics for high contrast imaging present challenges in manufacturing and testing due to their large surface departures from aspheric profiles at the aperture edges. With smaller form factors and consequent smaller surface deformations (<50 microns), fabrication of these mirrors with diamond turning followed by electron beam lithographic techniques becomes feasible. Though such a design reduces the system throughput to approx.50%, it still provides good performance down to 2 lambda/D inner working angle. With new achromatic focal plane mask designs, the system performance can be further improved. We report on the design, expected performance, fabrication challenges, and initial assessment of such novel PIAA optics.

  16. PISCES High Contrast Integral Field Spectrograph Simulations and Data Reduction Pipeline

    Science.gov (United States)

    Llop Sayson, Jorge Domingo; Memarsadeghi, Nargess; McElwain, Michael W.; Gong, Qian; Perrin, Marshall; Brandt, Timothy; Grammer, Bryan; Greeley, Bradford; Hilton, George; Marx, Catherine

    2015-01-01

    The PISCES (Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies) is a lenslet array based integral field spectrograph (IFS) designed to advance the technology readiness of the WFIRST (Wide Field Infrared Survey Telescope)-AFTA (Astrophysics Focused Telescope Assets) high contrast Coronagraph Instrument. We present the end to end optical simulator and plans for the data reduction pipeline (DRP). The optical simulator was created with a combination of the IDL (Interactive Data Language)-based PROPER (optical propagation) library and Zemax (a MatLab script), while the data reduction pipeline is a modified version of the Gemini Planet Imager's (GPI) IDL pipeline. The simulations of the propagation of light through the instrument are based on Fourier transform algorithms. The DRP enables transformation of the PISCES IFS data to calibrated spectral data cubes.

  17. High-sensitivity phase-contrast tomography of rat brain in phosphate buffered saline

    Energy Technology Data Exchange (ETDEWEB)

    Pfeiffer, Franz [Department of Physics, Technical University Munich, 85748 Garching (Germany); David, Christian; Bunk, Oliver [Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Poitry-Yamate, Carole; Gruetter, Rolf [Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); Mueller, Bert [Biomaterials Science Center, University of Basel, 4031 Basel (Switzerland); Weitkamp, Timm, E-mail: franz.pfeiffer@ph.tum.d [European Synchrotron Radiation Facility, B.P. 220, 38043 Grenoble Cedex (France)

    2009-09-01

    We report advances and complementary results concerning a recently developed method for high-sensitivity grating-based x-ray phase-contrast tomography. In particular we demonstrate how the soft tissue sensitivity of the technique can be used to obtain in-vitro tomographic images of rat brain specimens. Contrary to our previous experiments with fixated specimen (chemically modified or formalin fixed), the present results on the rat's brain are closer to the in-vivo situation. The findings are particularly important from a clinical point of view, since a similar approach using three gratings can be implemented with more readily available x-ray sources, such as standard x-ray tubes.

  18. High-contrast imaging and interferometry mission concepts for the characterization of exoplanets

    Science.gov (United States)

    Lawson, P. R.

    2014-03-01

    This review paper describes space-based high-contrast imaging mission concepts that have been developed for NASA and ESA for the detection and characterization of exoplanets. This effort will be put in the context of other ground and space-based exoplanet missions. Concepts for coronagraphs, starshades, and interferometers are described along with their predicted science yield and technology challenges. This will include concepts for flagship and probe-scale missions that have been developed over the past 20 years. Particular emphasis will be placed on the current state of the art in starlight suppression technology and the technology gaps that must yet be filled. The coronagraph instrument for the AFTA-WFIRST mission will be described, and a roadmap for future mission and technology development will be presented.

  19. Demonstration of high contrast with an obscured aperture with the WFIRST-AFTA shaped pupil coronagraph

    CERN Document Server

    Cady, Eric; An, Xin; Balasubramanian, Kunjithapatham; Diaz, Rosemary; Kasdin, N Jeremy; Kern, Brian; Kuhnert, Andreas; Nemati, Bijan; Poberezhskiy, Ilya; Riggs, A J Eldorado; Zimmer, Robert; Zimmerman, Neil

    2015-01-01

    The coronagraph instrument on the WFIRST-AFTA mission study has two coronagraphic architectures, shaped pupil and hybrid Lyot, which may be interchanged for use in different observing scenarios. Each architecture relies on newly-developed mask components to function in the presence of the AFTA aperture, and so both must be matured to a high technology readiness level (TRL) in advance of the mission. A series of milestones were set to track the development of the technologies required for the instrument; in this paper, we report on completion of WFIRST-AFTA Coronagraph Milestone 2---a narrowband $10^{-8}$ contrast test with static aberrations for the shaped pupil---and the plans for the upcoming broadband Coronagraph Milestone 5.

  20. Numerical Investigation of Vertical Cavity Lasers With High-Contrast Gratings Using the Fourier Modal Method

    DEFF Research Database (Denmark)

    Taghizadeh, Alireza; Mørk, Jesper; Chung, Il-Sug

    2016-01-01

    , the scattering losses of several HCG-based vertical cavities with inplane heterostructures which have promising prospects for fundamental physics studies and on-chip laser applications, are investigated. This type of parametric study of 3D structures would be numerically very demanding using spatial......We explore the use of a modal expansion technique, Fourier modal method (FMM), for investigating the optical properties of vertical cavities employing high-contrast gratings (HCGs). Three techniques for determining the resonance frequency and quality factor (Q-factor) of a cavity mode are compared......, and the computational uncertainties in the resonance frequency and Qfactor calculations are analyzed. Moreover, a method for reducing a three-dimensional (3D) simulation to lower-dimensional simulations is suggested, which allows for very fast and approximate analysis of a 3D structure. By using the implemented FMM...

  1. High contrast XMT studies of in-situ electrochemical dissolution of broken dental tools

    Science.gov (United States)

    Mills, David; Mitchell, Alison; Khine, Sean; Davis, Graham

    2016-10-01

    Fracture of nickel-titanium (NiTi) endodontic files is an uncommon but potentially damaging occurrence during root canal preparation. If the broken portion of the file remains inside the tooth canal it can prevent complete preparation of the root canal with consequent negative impact on treatment outcomes. Removal of file fragment from the tooth canal is currently a mechanical process, which due to the limited working space and restricted view can lead to further problems including perforation of the tooth. Electrochemical dissolution is a relatively new method proposed to dissolve a fractured instrument, fully or partially within the canal, to enable its removal. In this article we explore the effects of electrochemical dissolution on the root canal environment using high contrast time delay integration (TDI) X-ray micro-tomography (XMT) designed specifically for dental research.

  2. A novel method to obtain electronic speckle pattern interferometry fringe patterns with high contrast

    Institute of Scientific and Technical Information of China (English)

    Mengwei Li; Chen Tang; Gao Wang; Hongwei Ren; Ke Tang; Tianyu Ye

    2009-01-01

    Traditional speckle fringe patterns of electronic speckle pattern interferometry(ESPI)are obtained by adding,subtracting,or multiplying the speckle patterns recorded before and after the deformation.However,these speckle fringe patterns are of limited visibility,especially for addition and multiplication fringe patterns.We propose a novel method to obtain speckle fringe patterns of ESPI from undeformed and deformed speckle patterns.The fringe pattern generated by our method is of high contrast and has better quality than subtraction fringe.The new method is simple and does not require more computational effort.The proposed method is tested on the experimentally obtained undeformed and deformed speckle patterns.The experimental results illustrate the performance of this approach.

  3. High-contrast GeTe4 waveguides for mid-infrared biomedical sensing applications

    Science.gov (United States)

    Mittal, Vinita; Wilkinson, James S.; Murugan, Ganapathy S.

    2014-03-01

    Realization of single-mode waveguides is essential for ultra-sensitive biosensing in the mid-infrared molecular "fingerprint" region for biomedical lab-on-chip applications. High contrast (Δn ≍ 1) germanium telluride (GeTe4) single mode rib waveguides were fabricated on zinc selenide (ZnSe) substrates for evanescent field based sensing to detect analytes at low concentration. Amorphous GeTe4 thin films were deposited by RF-sputtering and were found to transmit over the spectral range from 2μm - 20μm. Photolithography followed by reactive ion etching was carried out to etch the film, forming rib waveguide structures with minimum surface roughness and vertical sidewalls. It was found that films deposited at room temperature have average roughness of about 5nm. Optical constants were determined by IR-VASE ellipsometry.

  4. Positive focal shift of gallium nitride high contrast grating focusing reflectors

    Science.gov (United States)

    He, Shumin; Wang, Zhenhai; Liu, Qifa

    2016-09-01

    We design a type of metasurfaces capable of serving as a visible-light focusing reflector based on gallium nitride (GaN) high contrast gratings (HCGs). The wavefront of the reflected light is precisely manipulated by spatial variation of the grating periods along the subwavelength ridge array to achieve light focusing. Different from conventional negative focal shift effect, a positive focal shift is observed in such focusing reflectors. Detailed investigations of the influence of device size on the focusing performance, especially the focal length, are preformed via a finite element method . The results show that all performance parameters are greatly affected by the reflector size. A more concentrated focal point, or a better focusing capability, can be achieved by larger size. With increasing reflector size, the achieved focal length decreases and gradually approaches to the design, thus the corresponding positive focal shift decreases. Our results are helpful for understanding the visible-light control of the planar HCG-based focusing reflectors.

  5. Separation of scattering and intrinsic attenuation at Asama volcano (Japan): Evidence of high volcanic structural contrasts

    Science.gov (United States)

    Prudencio, Janire; Aoki, Yosuke; Takeo, Minoru; Ibáñez, Jesús M.; Del Pezzo, Edoardo; Song, WenZhan

    2017-03-01

    In this study we show 2D intrinsic- and scattering-Q images of Asama volcano obtained by analyzing 2320 waveforms from active data. Observed energy envelopes were fitted to the diffusion model and separate intrinsic- and scattering-Q images were produced using a back-projection method based on a Gaussian-type weighting function. Synthetic tests indicate robustness and reliability of the results. Areas of high scattering attenuation coincide with the volcanic edifice and the summit at which recent eruptions took place. The intrinsic dissipation pattern shows a strong contrast between the east and west side of the volcanic structure with the low values observed in the west interpreted as solidified magma bodies. Our results demonstrate a strong relationship between structural heterogeneities and attenuation processes in volcanic areas and confirm the effectiveness of the present technique, which can be used as an imaging tool complementary to conventional techniques.

  6. Erythrocytes and microbubble contrast agents, improve the therapeutic efficiency of high intensity focused ultrasound

    Science.gov (United States)

    Takegami, Kenji; Kaneko, Yukio; Watanabe, Toshiaki; Maruyama, Toshiyuki; Matsumoto, Yoichiro; Nagawa, Hirokazu

    2005-03-01

    Erythrocytes, an well as Levovist microbubble contrast agent, enhance the heating effect of high intensity focused ultrasound (HIFU) and increase the coagulation volume produced by HIFU irradiation. In vitro experiments used human plasma with various concentrations of human erythrocytes in combination with or without Levovist. In vivo experiments used eight Japan white rabbits with three levels of anaemia. Using a 2.17 MHz transducer, HIFU was applied for 60 seconds, and the temperature rise and the volume of coagulation necrosis was evaluated. There was a significant correlation between the HIFU-induced temperature rise and hematocrit, with a correlation coefficient of 0.998 (p=0.0001). Although the temperature rise was smaller at low hematocrit, it was significantly increased by adding Levovist to the suspension (panaemia group was significantly increased by using Levovist (p<0.01).

  7. PISCES High Contrast Integral Field Spectrograph Simulations and Data Reduction Pipeline

    Science.gov (United States)

    Llop Sayson, Jorge Domingo; Memarsadeghi, Nargess; McElwain, Michael W.; Gong, Qian; Perrin, Marshall; Brandt, Timothy; Grammer, Bryan; Greeley, Bradford; Hilton, George; Marx, Catherine

    2015-01-01

    The PISCES (Prototype Imaging Spectrograph for Coronagraphic Exoplanet Studies) is a lenslet array based integral field spectrograph (IFS) designed to advance the technology readiness of the WFIRST (Wide Field Infrared Survey Telescope)-AFTA (Astrophysics Focused Telescope Assets) high contrast Coronagraph Instrument. We present the end to end optical simulator and plans for the data reduction pipeline (DRP). The optical simulator was created with a combination of the IDL (Interactive Data Language)-based PROPER (optical propagation) library and Zemax (a MatLab script), while the data reduction pipeline is a modified version of the Gemini Planet Imager's (GPI) IDL pipeline. The simulations of the propagation of light through the instrument are based on Fourier transform algorithms. The DRP enables transformation of the PISCES IFS data to calibrated spectral data cubes.

  8. High-Performance, High-Index-Contrast Chalcogenide Glass Photonics on Silicon and Unconventional Non-planar Substrates

    CERN Document Server

    Zou, Yi; Lin, Hongtao; Li, Lan; Moreel, Loise; Zhou, Jie; Du, Qingyang; Ogbuu, Okechukwu; Danto, Sylvain; Musgraves, J David; Richardson, Kathleen; Dobson, Kevin D; Birkmire, Robert; Hu, Juejun

    2013-01-01

    This paper reports a versatile, roll-to-roll and backend compatible technique for the fabrication of high-index-contrast photonic structures on both silicon and plastic substrates. The fabrication technique combines low-temperature chalcogenide glass film deposition and resist-free single-step thermal nanoimprint to process low-loss (1.6 dB/cm), sub-micron single-mode waveguides with a smooth surface finish using simple contact photolithography. Using this approach, the first chalcogenide glass micro-ring resonators are fabricated by thermal nanoimprint. The devices exhibit an ultra-high quality-factor of 400,000 near 1550 nm wavelength, which represents the highest value reported in chalcogenide glass micro-ring resonators. Furthermore, sub-micron nanoimprint of chalcogenide glass films on non-planar plastic substrates is demonstrated, which establishes the method as a facile route for monolithic fabrication of high-index-contrast devices on a wide array of unconventional substrates.

  9. Dynamics and structure of self-generated magnetics fields on solids following high contrast, high intensity laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Albertazzi, B. [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); INRS-EMT, 1650 bd L. Boulet, J3X1S2, Varennes, Québec (Canada); Graduate School of Engineering, University of Osaka, Suita, Osaka 565-087 (Japan); Chen, S. N.; Fuchs, J., E-mail: julien.fuchs@polytechnique.fr [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Institute of Applied Physics, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation); Antici, P. [INRS-EMT, 1650 bd L. Boulet, J3X1S2, Varennes, Québec (Canada); Dept. SBAI, Universita di Roma “La Sapienza,” Via A. Scarpa 14, 00161 Rome (Italy); Böker, J.; Swantusch, M.; Willi, O. [Institut für Laser-und Plasmaphysik, Heinrich-Heine-Universität, Düsseldorf (Germany); Borghesi, M. [School of Mathematics and Physics, The Queen' s University, Belfast (United Kingdom); Breil, J.; Feugeas, J. L.; Nicolaï, Ph.; Tikhonchuk, V. T.; D' Humières, E. [CELIA, University of Bordeaux - CNRS - CEA, 33405 Talence (France); Dervieux, V.; Nakatsutsumi, M.; Romagnagni, L. [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Lancia, L. [Dept. SBAI, Universita di Roma “La Sapienza,” Via A. Scarpa 14, 00161 Rome (Italy); Shepherd, R. [LLNL, East Av., Livermore, California 94550 (United States); Sentoku, Y. [Department of Physics, University of Nevada, Reno, Nevada 89557-0058 (United States); Starodubtsev, M. [Institute of Applied Physics, 46 Ulyanov Street, 603950 Nizhny Novgorod (Russian Federation); and others

    2015-12-15

    The dynamics of self-generated magnetic B-fields produced following the interaction of a high contrast, high intensity (I > 10{sup 19 }W cm{sup −2}) laser beam with thin (3 μm thick) solid (Al or Au) targets is investigated experimentally and numerically. Two main sources drive the growth of B-fields on the target surfaces. B-fields are first driven by laser-generated hot electron currents that relax over ∼10–20 ps. Over longer timescales, the hydrodynamic expansion of the bulk of the target into vacuum also generates B-field induced by non-collinear gradients of density and temperature. The laser irradiation of the target front side strongly localizes the energy deposition at the target front, in contrast to the target rear side, which is heated by fast electrons over a much larger area. This induces an asymmetry in the hydrodynamic expansion between the front and rear target surfaces, and consequently the associated B-fields are found strongly asymmetric. The sole long-lasting (>30 ps) B-fields are the ones growing on the target front surface, where they remain of extremely high strength (∼8–10 MG). These B-fields have been recently put by us in practical use for focusing laser-accelerated protons [B. Albertazzi et al., Rev. Sci. Instrum. 86, 043502 (2015)]; here we analyze in detail their dynamics and structure.

  10. High-contrast fluorescence imaging in fixed and living cells using optimized optical switches.

    Directory of Open Access Journals (Sweden)

    Liangxing Wu

    Full Text Available We present the design, synthesis and characterization of new functionalized fluorescent optical switches for rapid, all-visible light-mediated manipulation of fluorescence signals from labelled structures within living cells, and as probes for high-contrast optical lock-in detection (OLID imaging microscopy. A triazole-substituted BIPS (TzBIPS is identified from a rational synthetic design strategy that undergoes robust, rapid and reversible, visible light-driven transitions between a colorless spiro- (SP and a far-red absorbing merocyanine (MC state within living cells. The excited MC-state of TzBIPS may also decay to the MC-ground state emitting near infra-red fluorescence, which is used as a sensitive and quantitative read-out of the state of the optical switch in living cells. The SP to MC transition for a membrane-targeted TzBIPS probe (C₁₂-TzBIPS is triggered at 405 nm at an energy level compatible with studies in living cells, while the action spectrum of the reverse transition (MC to SP has a maximum at 650 nm. The SP to MC transition is complete within the 790 ns pixel dwell time of the confocal microscope, while a single cycle of optical switching between the SP and MC states in a region of interest is complete within 8 ms (125 Hz within living cells, the fastest rate attained for any optical switch probe in a biological sample. This property can be exploited for real-time correction of background signals in living cells. A reactive form of TzBIPS is linked to secondary antibodies and used, in conjunction with an enhanced scope-based analysis of the modulated MC-fluorescence in immuno-stained cells, for high-contrast immunofluorescence microscopic analysis of the actin cytoskeleton.

  11. Collimated Propagation of Fast Electron Beams Accelerated by High-Contrast Laser Pulses in Highly Resistive Shocked Carbon

    Science.gov (United States)

    Vaisseau, X.; Morace, A.; Touati, M.; Nakatsutsumi, M.; Baton, S. D.; Hulin, S.; Nicolaï, Ph.; Nuter, R.; Batani, D.; Beg, F. N.; Breil, J.; Fedosejevs, R.; Feugeas, J.-L.; Forestier-Colleoni, P.; Fourment, C.; Fujioka, S.; Giuffrida, L.; Kerr, S.; McLean, H. S.; Sawada, H.; Tikhonchuk, V. T.; Santos, J. J.

    2017-05-01

    Collimated transport of ultrahigh intensity electron current was observed in cold and in laser-shocked vitreous carbon, in agreement with simulation predictions. The fast electron beams were created by coupling high-intensity and high-contrast laser pulses onto copper-coated cones drilled into the carbon samples. The guiding mechanism—observed only for times before the shock breakout at the inner cone tip—is due to self-generated resistive magnetic fields of ˜0.5 - 1 kT arising from the intense currents of fast electrons in vitreous carbon, by virtue of its specific high resistivity over the range of explored background temperatures. The spatial distribution of the electron beams, injected through the samples at different stages of compression, was characterized by side-on imaging of hard x-ray fluorescence.

  12. High-contrast 10-fs OPCPA-based Front-End for the Apollon-10PW laser

    OpenAIRE

    Dimitrios PAPADOPOULOS; Ramirez, Patricia; Pellegrina, A; Lebas, N.; Leblanc, Catherine; Cheriaux, Gilles; ZOU, J-P; Mennerat, G.; Monot, P.; Mathieu, F.; Audebert, P.; Georges, Patrick; Druon, Frédéric

    2015-01-01

    International audience; We present a high-contrast 10-fs Front-End for Ti:sapphire PW-lasers within the Apollon-10PW project. This injector uses OPCPA pumped at 100 Hz by Yb-based CPA chain. Combination of OPCPA and XPW permits a >10 12 contrast ratio.

  13. Diagnosis of the hypothenar hammer syndrome by high-resolution contrast-enhanced MR angiography

    Energy Technology Data Exchange (ETDEWEB)

    Winterer, J.T.; Ghanem, N.; Schaefer, O.; Lehnhardt, S.; Thuerl, C.; Laubenberger, J. [Department of Diagnostic Radiology, University of Freiburg, Hugstetter Strasse 55, 79106 Freiburg (Germany); Roth, M. [Center of Geriatric Medicine and Gerontology Freiburg, University of Freiburg, Hugstetter Strasse 55, 79106 Freiburg (Germany); Horch, R.E. [Department of Plastic and Hand Surgery, University of Freiburg, Hugstetter Strasse 55, 79106 Freiburg (Germany)

    2002-10-01

    Our objective was to describe the imaging features of hypothenar hammer syndrome using minimally invasive contrast-enhanced MR angiography in comparison with oscillography study. In five patients with hypothenar hammer syndrome Gd-BOPTA-enhanced elliptically reordered 3D pulse sequence MR was compared with oscillography findings and clinical symptoms focusing on angiographic appearance of vessel injury, distribution pattern of hand vasculature and joining branches between the radial and ulnar artery supply. All patients showed segmental occlusion at the site of trauma impact with varying involvement of the superficial palmar arch, common volar digital arteries. Embolic disease was present in 50% of patients and could be clearly identified with MRA. Good correspondence was found between angiographic appearance including the presence of collaterals, clinical symptoms and oscillography. Bilateral comparison was helpful in distinguishing between vessel variants and pathology. Bilateral Gd-BOPTA-enhanced MR angiography is a minimally invasive method to depict clearly the localization and extent of vessel injury in hypothenar hammer syndrome providing valuable information about distribution pattern of hand vasculature and presence of collaterals; however, no flow data can be obtained. (orig.)

  14. First application of liquid-metal-jet sources for small-animal imaging: High-resolution CT and phase-contrast tumor demarcation

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, Daniel H.; Lundstroem, Ulf; Burvall, Anna; Hertz, Hans M. [Department of Applied Physics, KTH Royal Institute of Technology/Albanova, 10691 Stockholm (Sweden); Westermark, Ulrica K.; Arsenian Henriksson, Marie [Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, 17177 Stockholm (Sweden)

    2013-02-15

    Purpose: Small-animal studies require images with high spatial resolution and high contrast due to the small scale of the structures. X-ray imaging systems for small animals are often limited by the microfocus source. Here, the authors investigate the applicability of liquid-metal-jet x-ray sources for such high-resolution small-animal imaging, both in tomography based on absorption and in soft-tissue tumor imaging based on in-line phase contrast. Methods: The experimental arrangement consists of a liquid-metal-jet x-ray source, the small-animal object on a rotating stage, and an imaging detector. The source-to-object and object-to-detector distances are adjusted for the preferred contrast mechanism. Two different liquid-metal-jet sources are used, one circulating a Ga/In/Sn alloy and the other an In/Ga alloy for higher penetration through thick tissue. Both sources are operated at 40-50 W electron-beam power with {approx}7 {mu}m x-ray spots, providing high spatial resolution in absorption imaging and high spatial coherence for the phase-contrast imaging. Results: High-resolution absorption imaging is demonstrated on mice with CT, showing 50 {mu}m bone details in the reconstructed slices. High-resolution phase-contrast soft-tissue imaging shows clear demarcation of mm-sized tumors at much lower dose than is required in absorption. Conclusions: This is the first application of liquid-metal-jet x-ray sources for whole-body small-animal x-ray imaging. In absorption, the method allows high-resolution tomographic skeletal imaging with potential for significantly shorter exposure times due to the power scalability of liquid-metal-jet sources. In phase contrast, the authors use a simple in-line arrangement to show distinct tumor demarcation of few-mm-sized tumors. This is, to their knowledge, the first small-animal tumor visualization with a laboratory phase-contrast system.

  15. Homogenization of two-phase flow: high contrast of phase permeability; Homogeneisation d'ecoulement diphasique: grand contraste de permeabilite d'une phase

    Energy Technology Data Exchange (ETDEWEB)

    Panasenko, G.P. [Saint-Etienne Universite, Equipe d' Analyse Numerique, UPRES EA 3058, 42 (France); Universite Pierre et Marie Curie, Lab. de Modelisation en Numerique, CNRS UMR 7607, 75 - Paris (France); Virnovsky, G. [R.F. - Rogaland Research, Stavanger (Norway)

    2003-01-01

    The steady-state two-phase flow non-linear equation is considered in the case when one of phases has low effective permeability in some periodic set, while on the complementary set it is high; the second phase has no contrast of permeabilities in different zones. A homogenization procedure gives the homogenized model with macroscopic effective permeability of the second phase depending on the gradient and on the second order derivatives of the macroscopic pressure of the first phase. This effect cannot be obtained by classical (one small parameter) homogenization. (author)

  16. The TRENDS High-Contrast Imaging Survey. VI. Discovery of a Mass, Age, and Metallicity Benchmark Brown Dwarf

    CERN Document Server

    Crepp, Justin R; Bechter, Eric B; Montet, Benjamin T; Johnson, John Asher; Piskorz, Danielle; Howard, Andrew W; Isaacson, Howard

    2016-01-01

    The mass and age of substellar objects are degenerate parameters leaving the evolutionary state of brown dwarfs ambiguous without additional information. Theoretical models are normally used to help distinguish between old, massive brown dwarfs and young, low mass brown dwarfs but these models have yet to be properly calibrated. We have carried out an infrared high-contrast imaging program with the goal of detecting substellar objects as companions to nearby stars to help break degeneracies in inferred physical properties such as mass, age, and composition. Rather than using imaging observations alone, our targets are pre-selected based on the existence of dynamical accelerations informed from years of stellar radial velocity (RV) measurements. In this paper, we present the discovery of a rare benchmark brown dwarf orbiting the nearby ($d=18.69\\pm0.19$ pc), solar-type (G9V) star HD 4747 ([Fe/H]=$-0.22\\pm0.04$) with a projected separation of only $\\rho=11.3\\pm0.2$ AU ($\\theta \\approx$ 0.6''). Precise Doppler m...

  17. High-resolution Z-contrast imaging and EELS study of functional oxide materials.

    Science.gov (United States)

    Klie, Robert F; Zhao, Yuan; Yang, Guang; Zhu, Yimei

    2008-08-01

    Functional complex-oxide materials show a wide variety of properties and behaviors that cannot be found in any other class of materials, including high-temperature superconductivity and colossal magneto resistance. Consequently, this group of oxide materials has become the focus of many experimental as well as theoretical studies, aiming at understanding the fundamental mechanisms and properties that govern these complex structures. Here, we will review our high-resolution Z-contrast imaging and electron energy-loss studies of two complex-oxide materials systems, more specifically low-angle tilt grain-boundaries in YBa(2)Cu(3)O(7) (YBCO), and the spin-state transition in LaCoO(3). It will be shown that the O K-edge pre-peak can be used to quantify the hole-concentration in the vicinity of the dislocation core in YBCO, as well as to determine the Co(3+) spin-state in LaCoO(3).

  18. Four shades of brown: tuning of electrochromic polymer blends toward high-contrast eyewear.

    Science.gov (United States)

    Österholm, Anna M; Shen, D Eric; Kerszulis, Justin A; Bulloch, Rayford H; Kuepfert, Michael; Dyer, Aubrey L; Reynolds, John R

    2015-01-28

    We report a straightforward strategy of accessing a wide variety of colors through simple predictive color mixing of electrochromic polymers (ECPs). We have created a set of brown ECP blends that can be incorporated as the active material in user-controlled electrochromic eyewear. Color mixing of ECPs proceeds in a subtractive fashion, and we acquire various hues of brown through the mixing of cyan and yellow primaries in combination with orange and periwinkle-blue secondary colors. Upon oxidation, all of the created blends exhibit a change in transmittance from ca. 10 to 70% in a few seconds. We demonstrate the attractiveness of these ECP blends as active materials in electrochromic eyewear by assembling user-controlled, high-contrast, fast-switching, and fully solution-processable electrochromic lenses with colorless transmissive states and colored states that correspond to commercially available sunglasses. The lenses were fabricated using a combination of inkjet printing and blade-coating to illustrate the feasibility of using soluble ECPs for high-throughput and large-scale processing.

  19. Implantation of high concentration noble gases in cubic zirconia and silicon carbide: A contrasted radiation tolerance

    Energy Technology Data Exchange (ETDEWEB)

    Velişa, Gihan, E-mail: gihan@tandem.nipne.ro [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania); Debelle, Aurélien; Thomé, Lionel; Mylonas, Stamatis [Centre de Sciences Nucléaires et de Sciences de la Matière, CNRS-IN2P3-Université Paris-Sud, Bât. 108, F-91405 Orsay (France); Vincent, Laetitia [Centre de Sciences Nucléaires et de Sciences de la Matière, CNRS-IN2P3-Université Paris-Sud, Bât. 108, F-91405 Orsay (France); Institut d’Electronique Fondamentale, Université Paris-Sud, UMR 8622, Bât. 220, 91405 Orsay (France); Boulle, Alexandre [Science des Procédés Céramiques et de Traitements de Surface, CNRS UMR 7315, Centre Européen de la Céramique, 12 rue Atlantis, 87068 Limoges (France); Jagielski, Jacek [Institute for Electronic Materials Technology, Wolczynska 133, 01-919 Warsaw (Poland); National Center for Nuclear Research, PL-05-400 Swierk/Otwock (Poland); Pantelica, Dan [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania)

    2014-08-01

    The modifications of the microstructure of yttria-stabilized cubic zirconia and silicon carbide single crystals implanted with high concentrations of noble gas ions and subsequently annealed at high temperature were characterized using RBS/C, XRD and TEM. It is found that the annealing behavior is strongly dependent on both the material and the implanted noble gases. Ar-implanted yttria-stabilized zirconia shows no significant microstructural modification upon annealing at 800 °C, e.g. dislocations are still present and the size of the Ar bubbles does not evolve. This is in strong contrast with previous observations on helium-implanted zirconia, where the formation of bubbles and elongated fractures were observed. In the case of SiC, thermal annealing at 1000 °C shows an enhanced damage recovery when He is implanted as compared to Ar implantation and the recrystallization of the matrix is accompanied with the release of noble gas atoms. This difference can be ascribed to different atomic radii, and thus mobility of implanted species.

  20. Metasurfaces based on Gallium Nitride High Contrast Gratings at Visible Range

    Science.gov (United States)

    Wang, Zhenhai; He, Shumin; Liu, Qifa; Wang, Wei; Wang, Yongjin; Zhu, Hongbo; Grünberg Research Centre Team

    2015-03-01

    Metasurfaces are currently attracting global attention due to their ability to achieve full control of light propagation. However, these metasurfaces have thus far been constructed mostly from metallic materials, which greatly limit the diffraction efficiencies because of the ohmic losses. Semiconducting metasurfaces offer one potential solution to the issue of losses. Besides, the use of semiconducting materials can broaden the applicability of metasurfaces, as they enable facile integration with electronics and mechanical systems and can benefit from mature semiconductor fabrication technologies. We have proposed visible-light metasurfaces (VLMs) capable of serving as lenses and beam deflecting elements based on gallium nitride (GaN) high contrast gratings (HCGs). By precisely manipulating the wave-fronts of the transmitted light, we theoretically demonstrate an HCG focusing lens with transmissivity of 83.0% and numerical aperture of 0.77, and a VLM with beam deflection angle of 6.03° and transmissivity as high as 93.3%. The proposed metasurfaces are promising for GaN-based visible light-emitting diodes (LEDs), which would be robust and versatile for controlling the output light propagation and polarization, as well as enhancing the extraction efficiency of the LEDs.

  1. Co-Immobilization of Proteins and DNA Origami Nanoplates to Produce High-Contrast Biomolecular Nanoarrays.

    Science.gov (United States)

    Hager, Roland; Burns, Jonathan R; Grydlik, Martyna J; Halilovic, Alma; Haselgrübler, Thomas; Schäffler, Friedrich; Howorka, Stefan

    2016-06-01

    The biofunctionalization of nanopatterned surfaces with DNA origami nanostructures is an important topic in nanobiotechnology. An unexplored challenge is, however, to co-immobilize proteins with DNA origami at pre-determined substrate sites in high contrast relative to the nontarget areas. The immobilization should, in addition, preferably be achieved on a transparent substrate to allow ultrasensitive optical detection. If successful, specific co-binding would be a step towards stoichiometrically defined arrays with few to individual protein molecules per site. Here, we successfully immobilize with high specificity positively charged avidin proteins and negatively charged DNA origami nanoplates on 100 nm-wide carbon nanoislands while suppressing undesired adsorption to surrounding nontarget areas. The arrays on glass slides achieve unprecedented selectivity factors of up to 4000 and allow ultrasensitive fluorescence read-out. The co-immobilization onto the nanoislands leads to layered biomolecular architectures, which are functional because bound DNA origami influences the number of capturing sites on the nanopatches for other proteins. The novel hybrid DNA origami-protein nanoarrays allow the fabrication of versatile research platforms for applications in biosensing, biophysics, and cell biology, and, in addition, represent an important step towards single-molecule protein arrays.

  2. Integrated laser with low-loss high index-contrast waveguides for OEICs

    Energy Technology Data Exchange (ETDEWEB)

    Welty, R J; Bond, T C; Behymer, E; Pocha, M; Loomis, G; Wolfe, J; Vernon, S

    2004-11-22

    Photonic integrated circuits require the ability to integrate both lasers and waveguides with low absorption and coupling loss. This technology is being developed at LLNL for digital logic gates for optical key generation circuits to facilitate secure communications. Here, we demonstrate an approach of integrating InGaAs DQW edge emitting lasers (EEL) with electron beam evaporated dielectric waveguides. The EELs are defined by electron cyclotron resonance etching (ECR). This approach results in highly anisotropic etched mirrors with smooth etched features (sidewall rms roughness = 28 {angstrom}, surface rms roughness = 10 {angstrom}). The mirror is etched to form both the laser cavity and define the waveguide mesa, which accommodates a dielectric stack, where the core is aligned with the active region of the laser to achieve maximum vertical mode overlapping. The waveguides are based on SiO{sub 2}/Ta{sub 2}O{sub 5}/SiO{sub 2} which yields a high index contrast of 0.6, resulting in low loss guides ({approx}2-3dB/cm). The design of the interface has taken into account the waveguide transmission loss, air gap spacing and tilt between the laser and waveguide. The critical feature for this deposition technique is its required high directionality or minimal sidewall deposition and corner effects. In the butt coupled EEL/waveguide system we have measured a slope efficiency to be as high as 0.45 W/A. We have in conclusion demonstrated a technology that allows direct coupling of a dielectric optical interconnect to a semiconductor laser monolithically fabricated on the semiconductor substrate.

  3. High contrast imaging of reversibly switchable fluorescent proteins via temporally unmixed Multispectral Optoacoustic Tomography (tuMSOT)

    CERN Document Server

    Stiel, Andre C; Jiang, Yuanyuan; Ntziachristos, Vasilis; Razansky, Daniel; Westmeyer, Gil G

    2014-01-01

    Photocontrol of reversibly switchable fluorescent proteins (RSFPs) was used to program optoacoustic signal time courses that were temporally unmixed to increase the proteins contrast-to-noise-ratios (CNRs) in optoacoustic imaging. In this way, two variants of the RSFP Dronpa with very similar optoacoustic spectra could be readily discriminated in the presence of highly absorbing blood. Addition of temporal unmixing to multispectral optoacoustic tomography (tuMSOT) in conjunction with synthetic or genetically controlled photochromic contrast agents and customized photoswitching schedules can increase the performance of multiplexed and high contrast molecular optoacoustic imaging.

  4. High-contrast visualization of graphene oxide on dye-sensitized glass, quartz, and silicon by fluorescence quenching.

    Science.gov (United States)

    Treossi, Emanuele; Melucci, Manuela; Liscio, Andrea; Gazzano, Massimo; Samorì, Paolo; Palermo, Vincenzo

    2009-11-04

    We present a novel approach for detecting and visualizing graphene oxide (GO) with high contrast on different substrates, including glass, quartz, and silicon. Visualization of GO sheets is accomplished through quenching the fluorescence of a thiophene dye, giving high optical contrast without the need to use interference methods. A comparison of fluorescence, AFM, and XRD measurements confirmed that even a single GO sheet can completely quench the fluorescence and thus be quickly visualized.

  5. High-resolution 3D non-contrast-enhanced, ECG-gated, multi-step MR angiography of the lower extremities: Comparison with contrast-enhanced MR angiography

    Energy Technology Data Exchange (ETDEWEB)

    Mohrs, Oliver K. [University of Heidelberg, Department of Diagnostic and Interventional Radiology, Heidelberg (Germany); Darmstadt Radiology, Department of Cardiovascular Imaging at Alice-Hospital, Darmstadt (Germany); Petersen, Steffen E. [The London Chest Hospital, Centre for Advanced Cardiovascular Imaging, William Harvey Research Institute, Barts and The London NIHR Biomedical Research Unit, London (United Kingdom); Heidt, Martin C. [Cardiovascular Center Darmstadt, Darmstadt (Germany); Schulze, Thomas; Schmitt, Peter [Siemens AG, Healthcare Sector, MR Application and Workflow Development, Erlangen (Germany); Bergemann, Sabine [Darmstadt Radiology, Department of Cardiovascular Imaging at Alice-Hospital, Darmstadt (Germany); Kauczor, Hans-Ulrich [University of Heidelberg, Department of Diagnostic and Interventional Radiology, Heidelberg (Germany)

    2011-02-15

    To determine the diagnostic value of non-contrast-enhanced, 3D-high-resolution, ECG-gated, multi-step MR angiography (non-ceMRA) of the lower extremities using a modified turbo-spin-echo technique in comparison to 1.0-molar contrast-enhanced MR angiography (ceMRA) in patients with suspected peripheral vascular disease (PVD). Fifty consecutive patients underwent non-ceMRA before ceMRA within the same session. We assessed examination time, image quality, localisation and severity of stenosis. Examination time was shorter for ceMRA (12 {+-} 4 min) compared with non-ceMRA (28 {+-} 6 min, p < 0.001). The image quality of the aorta-iliac, femoral and combined popliteal and lower leg arteries was inferior for non-ceMRA (2.8 {+-} 0.8/3.3 {+-} 0.8/3.3 {+-} 0.9) versus ceMRA (4.7 {+-} 0.8/4.8 {+-} 0.6/4.8 {+-} 0.7) on a 5-point scale with 5 for maximum quality (p < 0.01). CeMRA offered more assessable data sets than non-ceMRA (98% vs. 90%). For detecting stenosis >50% or occlusions of pelvic and femoral arteries using non-ceMRA the sensitivity, specificity, positive and negative predictive values were 94%, 86%, 67% and 98% and for popliteal and lower leg arteries 93%, 87%, 69% and 98%, respectively. We demonstrated that 3D non-ceMRA represents a very promising technique in patients with lower extremities PVD and could be used as an alternative if gadolinium-based contrast agents cannot be administered. (orig.)

  6. Laryngeal High-Speed Videoendoscopy: Sensitivity of Objective Parameters towards Recording Frame Rate

    OpenAIRE

    Anne Schützenberger; Melda Kunduk; Michael Döllinger; Christoph Alexiou; Denis Dubrovskiy; Marion Semmler; Anja Seger; Christopher Bohr

    2016-01-01

    The current use of laryngeal high-speed videoendoscopy in clinic settings involves subjective visual assessment of vocal fold vibratory characteristics. However, objective quantification of vocal fold vibrations for evidence-based diagnosis and therapy is desired, and objective parameters assessing laryngeal dynamics have therefore been suggested. This study investigated the sensitivity of the objective parameters and their dependence on recording frame rate. A total of 300 endoscopic high-sp...

  7. Real-time underwater object detection based on an electrically scanned high-resolution sonar

    DEFF Research Database (Denmark)

    Henriksen, Lars

    1994-01-01

    The paper describes an approach to real time detection and tracking of underwater objects, using image sequences from an electrically scanned high-resolution sonar. The use of a high resolution sonar provides a good estimate of the location of the objects, but strains the computers on board, beca...

  8. Microtopography of bare peat: an objective classification from high-resolution topographic survey data

    Science.gov (United States)

    Smith, Mark; Warburton, Jeff

    2017-04-01

    Peatlands globally are at risk of degradation through increased susceptibility to erosion as a result of climate change. For peatland restoration practices to be designed efficiently and evaluated effectively, quantification of eroded peat volumes is required alongside an understanding of the processes responsible for their degradation. Owing to the unique material properties of peat, fine-scale microtopographic expressions of surface processes are especially pronounced and present a potentially rich source of geomorphological information; providing valuable insights into the stability and dominant surface process regimes. Bare peat is highly responsive to changing environmental forces acting at the near surface and characteristic microtopographies emerge in response to rainfall, surface wash, wind action and fluctuations in surface temperature (both drying and freezing). Spatial and temporal variations in surface roughness reflect contrasts in the physical properties of the peat and key erosion processes acting in combination. We present the first conceptual framework to rigorously describe bare peat microtopography and use Structure-from-Motion (SfM) surveys to quantify roughness for different peat surfaces. Through application of a survey-grade structured-light hand-held 3D imager (Mantis Vision F5-Short Range) which can represent sub-millimetre topographic variability in field conditions, we present the most reliable field validation of SfM at the plot scale (classification system derived from decision tree analysis. After training on 66% of the data, the decision tree correctly classified 85% of plots into microtopographic types using 5 roughness metrics each of which quantified a different aspect of the surface variability. We show that through a combination of roughness metrics, microtopographic types can be identified objectively from high resolution survey data, aiding the interpretation of sediment budgets and providing a much-needed geomorphological

  9. The issues and tentative solutions for contrast-enhanced magnetic resonance imaging at ultra-high field strength.

    Science.gov (United States)

    Fries, Peter; Morelli, John N; Lux, Francois; Tillement, Olivier; Schneider, Günther; Buecker, Arno

    2014-01-01

    Magnetic resonance imaging (MRI) performed at ultra-high field strengths beyond 3 Tesla (T) has become increasingly prevalent in research and preclinical applications. As such, the inevitable clinical implementation of such systems lies on the horizon. The major benefit of ultra-high field MRI is the markedly increased signal-to-noise ratios achievable, enabling acquisition of MR images with simultaneously greater spatial and temporal resolution. However, at field strengths higher than 3 T, the efficacy of Gd(III)-based contrast agents is diminished due to decreased r1 relaxivity, somewhat limiting imaging of the vasculature and contrast-enhanced imaging of tumors. There have been extensive efforts to design new contrast agents with high r1 relaxivities based on macromolecular compounds or nanoparticles; however, the efficacy of these agents at ultra-high field strengths has not yet been proven. The aim of this review article is to provide an overview of the basic principles of MR contrast enhancement processes and to highlight the main factors influencing relaxivity. In addition, challenges and opportunities for contrast-enhanced MRI at ultra-high field strengths will be explored. Various approaches for the development of effective contrast agent molecules that are suitable for a broad spectrum of applied field strengths will be discussed in the context of the current literature.

  10. Determining contrast sensitivity functions for monochromatic light emitted by high-brightness LEDs

    Science.gov (United States)

    Ramamurthy, Vasudha; Narendran, Nadarajah; Freyssinier, Jean Paul; Raghavan, Ramesh; Boyce, Peter

    2004-01-01

    Light-emitting diode (LED) technology is becoming the choice for many lighting applications that require monochromatic light. However, one potential problem with LED-based lighting systems is uneven luminance patterns. Having a uniform luminance distribution is more important in some applications. One example where LEDs are becoming a viable alternative and luminance uniformity is an important criterion is backlighted monochromatic signage. The question is how much uniformity is required for these applications. Presently, there is no accepted metric that quantifies luminance uniformity. A recent publication proposed a method based on digital image analysis to quantify beam quality of reflectorized halogen lamps. To be able to employ such a technique to analyze colored beams generated by LED systems, it is necessary to have contrast sensitivity functions (CSFs) for monochromatic light produced by LEDs. Several factors including the luminance, visual field size, and spectral power distribution of the light affect the CSFs. Although CSFs exist for a variety of light sources at visual fields ranging from 2 degrees to 20 degrees, CSFs do not exist for red, green, and blue light produced by high-brightness LEDs at 2-degree and 10-degree visual fields and at luminances typical for backlighted signage. Therefore, the goal of the study was to develop a family of CSFs for 2-degree and 10-degree visual fields illuminated by narrow-band LEDs at typical luminances seen in backlighted signs. The details of the experiment and the results are presented in this manuscript.

  11. A mineralogical study in contrasts: highly mineralized whale rostrum and human enamel

    Science.gov (United States)

    Li, Zhen; Ai-Jawad, Maisoon; Siddiqui, Samera; Pasteris, Jill D.

    2015-11-01

    The outermost enamel of the human tooth and the rostrum of the whale Mesoplodon densirostris are two highly mineralized tissues that contain over 95 wt.% mineral, i.e., bioapatite. However, the same mineral type (carbonated hydroxylapatite) does not yield the same material properties, as revealed by Raman spectroscopy, scanning electron microscopy, electron microprobe analysis, and synchrotron X-ray diffraction analysis. Overall, the outermost enamel of a tooth has more homogeneous physical and chemical features than the rostrum. Chemical comparison of rostrum and enamel shows bioapatite in the rostrum to be enriched in Na, Mg, CO3, and S, whereas the outermost enamel shows only a slightly enriched Cl concentration. Morphologically, mineral rods (at tens of μm scale), crystallites and prisms (at μm and sub-μm scale), and platelets (at tens of nm scale) all demonstrate less organized texture in the rostrum than in enamel. Such contrasts between two mineralized tissues suggest distinct pathways of biomineralization, e.g., the nature of the equilibrium between mineral and body fluid. This study illustrates the remarkable flexibility of the apatite mineral structure to match its chemical and physical properties to specific biological needs within the same animal or between species.

  12. Complete sparing of high-contrast color input to motion perception in cortical color blindness.

    Science.gov (United States)

    Cavanagh, P; Hénaff, M A; Michel, F; Landis, T; Troscianko, T; Intriligator, J

    1998-07-01

    It is widely held that color and motion are processed by separate parallel pathways in the visual system, but this view is difficult to reconcile with the fact that motion can be detected in equiluminant stimuli that are defined by color alone. To examine the relationship between color and motion, we tested three patients who had lost their color vision following cortical damage (central achromatopsia). Despite their profound loss in the subjective experience of color and their inability to detect the motion of faint colors, all three subjects showed surprisingly strong responses to high-contrast, moving color stimuli--equal in all respects to the performance of subjects with normal color vision. The pathway from opponent-color detectors in the retina to the motion analysis areas must therefore be independent of the damaged color centers in the occipitotemporal area. It is probably also independent of the motion analysis area MT/V5, because the contribution of color to motion detection in these patients is much stronger than the color response of monkey area MT.

  13. Diffraction Analysis of 2-D Pupil Mapping for High-Contrast Imaging

    CERN Document Server

    Vanderbei, R J

    2005-01-01

    Pupil-mapping is a technique whereby a uniformly-illuminated input pupil, such as from starlight, can be mapped into a non-uniformly illuminated exit pupil, such that the image formed from this pupil will have suppressed sidelobes, many orders of magnitude weaker than classical Airy ring intensities. Pupil mapping is therefore a candidate technique for coronagraphic imaging of extrasolar planets around nearby stars. Unlike most other high-contrast imaging techniques, pupil mapping is lossless and preserves the full angular resolution of the collecting telescope. So, it could possibly give the highest signal-to-noise ratio of any proposed single-telescope system for detecting extrasolar planets. Prior analyses based on pupil-to-pupil ray-tracing indicate that a planet fainter than 10^{-10} times its parent star, and as close as about 2 lambda/D, should be detectable. In this paper, we describe the results of careful diffraction analysis of pupil mapping systems. These results reveal a serious unresolved issue....

  14. Multiscale finite element methods for high-contrast problems using local spectral basis functions

    KAUST Repository

    Efendiev, Yalchin

    2011-02-01

    In this paper we study multiscale finite element methods (MsFEMs) using spectral multiscale basis functions that are designed for high-contrast problems. Multiscale basis functions are constructed using eigenvectors of a carefully selected local spectral problem. This local spectral problem strongly depends on the choice of initial partition of unity functions. The resulting space enriches the initial multiscale space using eigenvectors of local spectral problem. The eigenvectors corresponding to small, asymptotically vanishing, eigenvalues detect important features of the solutions that are not captured by initial multiscale basis functions. Multiscale basis functions are constructed such that they span these eigenfunctions that correspond to small, asymptotically vanishing, eigenvalues. We present a convergence study that shows that the convergence rate (in energy norm) is proportional to (H/Λ*)1/2, where Λ* is proportional to the minimum of the eigenvalues that the corresponding eigenvectors are not included in the coarse space. Thus, we would like to reach to a larger eigenvalue with a smaller coarse space. This is accomplished with a careful choice of initial multiscale basis functions and the setup of the eigenvalue problems. Numerical results are presented to back-up our theoretical results and to show higher accuracy of MsFEMs with spectral multiscale basis functions. We also present a hierarchical construction of the eigenvectors that provides CPU savings. © 2010.

  15. The inner environment of Z~CMa: High-Contrast Imaging Polarimetry with NaCo

    CERN Document Server

    Canovas, H; Dougados, C; de Boer, J; Ménard, F; Casassus, S; Schreiber, M R; Cieza, L A; Caceres, C; Girard, J H

    2015-01-01

    Context. Z\\,CMa is a binary composed of an embedded Herbig Be and an FU Ori class star separated by $\\sim100$ au. Observational evidence indicate a complex environment in which each star has a circumstellar disk and drives a jet, and the whole system is embedded in a large dusty envelope. Aims. We aim to probe the circumbinary environment of Z\\,CMa in the inner 400 au in scattered light. Methods. We use high contrast imaging polarimetry with VLT/NaCo at $H$ and $K_s$ bands. Results. The central binary is resolved in both bands. The polarized images show three bright and complex structures: a common dust envelope, a sharp extended feature previously reported in direct light, and an intriguing bright clump located $0\\farcs3$ south of the binary, which appears spatially connected to the sharp extended feature. Conclusions.We detect orbital motion when compared to previous observations, and report a new outburst driven by the Herbig star. Our observations reveal the complex inner environment of Z\\,CMa with unprec...

  16. High-resolution patterning of silver conductive lines by adhesion contrast planography

    Science.gov (United States)

    Kusaka, Yasuyuki; Koutake, Masayoshi; Ushijima, Hirobumi

    2015-09-01

    We developed printed electronics compatible planographic printing methods that enable single-micrometer-order patterning with high rectangularity and thickness uniformity. Instead of conventional planographic printing methods where selective wetting is used for pattern generation, an adhesive latent image produced on a silicone surface is exploited for patterning in the proposed printing methodologies. We further investigated the fundamental mechanisms of the proposed methods by focusing on adhesion contrasts between the blanket, printing area, and non-printing area of a printing plate (PP) and determined that printing is feasible when a simple magnitude relation of adhesions is satisfied for thin layers of size ranging from approximately 50 nm to 100 nm. Latent image formation can be carried out via a simple ultraviolet exposure of the silicone surface, thereby enabling the rapid prototyping of printed device fabrications. The easily preparable, single material-based flat PPs developed in this study have the advantages of flexibility in pattern designs, washing process, fabrication cost, and pattern-rewriting capability compared with the conventional printing methods in which raised surfaces such as stamps or clichés are required for patterning.

  17. High seed dispersal ability of Pinus canariensis in stands of contrasting density inferred from genotypic data

    Directory of Open Access Journals (Sweden)

    Unai López de Heredia

    2015-04-01

    Full Text Available Aim of the study: Models that combine parentage analysis from molecular data with spatial information of seeds and seedlings provide a framework to describe and identify the factors involved in seed dispersal and recruitment of forest species. In the present study we used a spatially explicit method (the gene shadow model in order to assess primary and effective dispersal in Pinus canariensis. Area of study: Pinus canariensis is endemic to the Canary Islands (Spain. Sampling sites were a high density forest in southern slopes of Tenerife and a low density stand in South Gran Canaria. Materials and methods: We fitted models based on parentage analysis from seeds and seedlings collected in two sites with contrasting stand density, and then compared the resulting dispersal distributions. Main results: The results showed that: 1 P. canariensis has a remarkable dispersal ability compared to other pine species; 2 there is no discordance between primary and effective dispersals, suggesting limited secondary dispersal by animals and lack of Janzen-Connell effect; and 3 low stand densities enhance the extent of seed dispersal, which was higher in the low density stand. Research highlights: The efficient dispersal mechanism of P. canariensis by wind inferred by the gene shadow model is congruent with indirect measures of gene flow, and has utility in reconstructing past demographic events and in predicting future distribution ranges for the species.

  18. Broadband MEMS-tunable high-index-contrast subwavelength grating long-wavelength VCSEL

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Iakovlev, Vladimir; Sirbu, Alexei

    2010-01-01

    A widely-tunable single-mode 1.3 μm vertical-cavity surface-emitting laser structure incorporating a microelectromechanical system-tunable high-index-contrast subwavelength grating (HCG) mirror is suggested and numerically investigated. A linear tuning range of 100 nm and a wavelength tuning...... efficiency of 0.203 are predicted. The large tuning range and efficiency are attributed to the incorporation of the tuning air gap as part of the optical cavity and to the use of a short cavity structure. The short cavity length can be achieved by employing a HCG design of which the reflection mechanism does...... not rely on resonant coupling. The absence of resonance coupling leads to a 0.59 λ-thick penetration depth of the HCG and enables to use a 0.25 λ-thick tuning air gap underneath the HCG. This considerably reduces the effective cavity length, leading to larger tuning range and efficiency. The basic...

  19. Phase-contrast tomography of neuronal tissues: from laboratory- to high resolution synchrotron CT

    Science.gov (United States)

    Töpperwien, Mareike; Krenkel, Martin; Müller, Kristin; Salditt, Tim

    2016-10-01

    Assessing the three-dimensional architecture of neuronal tissues with sub-cellular resolution presents a significant analytical challenge. Overcoming the limitations associated with serial slicing, phase-contrast x-ray tomography has the potential to contribute to this goal. Even compact laboratory CT at an optimized liquid-metal jet micro- focus source combined with suitable phase-retrieval algorithms and preparation protocols can yield renderings with single cell sensitivity in millimeter sized brain areas of mouse. Here, we show the capabilities of the setup by imaging a Golgi-Cox impregnated mouse brain. Towards higher resolution we extend these studies at our recently upgraded waveguide-based cone-beam holo-tomography instrument GINIX at DESY. This setup allows high resolution recordings with adjustable field of view and resolution, down to the voxel sizes in the range of a few ten nanometers. The recent results make us confident that important issues of neuronal connectivity can be addressed by these methods, and that 3D (virtual) histology with nanoscale resolution will become an attractive modality for neuroscience research.

  20. High-Contrast Visualization of Upconversion Luminescence in Mice Using Time-Gating Approach.

    Science.gov (United States)

    Zheng, Xianlin; Zhu, Xingjun; Lu, Yiqing; Zhao, Jiangbo; Feng, Wei; Jia, Guohua; Wang, Fan; Li, Fuyou; Jin, Dayong

    2016-04-01

    Optical imaging through the near-infrared (NIR) window provides deep penetration of light up to several centimeters into biological tissues. Capable of emitting 800 nm luminescence under 980 nm illumination, the recently developed upconversion nanoparticles (UCNPs) suggest a promising optical contrast agent for in vivo bioimaging. However, presently they require high-power lasers to excite when applied to small animals, leading to significant scattering background that limits the detection sensitivity as well as a detrimental thermal effect. In this work, we show that the time-gating approach implementing pulsed illumination from a NIR diode laser and time-delayed imaging synchronized via an optical chopper offers detection sensitivity more than 1 order of magnitude higher than the conventional approach using optical band-pass filters (S/N, 47321/6353 vs 5339/58), when imaging UCNPs injected into Kunming mice. The pulsed laser illumination (70 μs ON in 200 μs period) also reduces the overall thermal accumulation to 35% of that under the continuous-wave mode. Technical details are given on setting up the time-gating unit comprising an optical chopper, a pinhole, and a microscopy eyepiece. Being generally compatible with any camera, this provides a convenient and low cost solution to NIR animal imaging using UCNPs as well as other luminescent probes.

  1. High-relaxivity contrast-enhanced magnetic resonance neuroimaging: a review

    Energy Technology Data Exchange (ETDEWEB)

    Giesel, Frederik L. [German Cancer Research Centre (DKFZ), Department of Radiology E010, Heidelberg (Germany); University of Heidelberg, Nuclear Medicine, Heidelberg (Germany); Mehndiratta, Amit [German Cancer Research Centre (DKFZ), Department of Radiology E010, Heidelberg (Germany); Harvard Medical School, Department of Radiology, Massachusetts General Hospital, Boston, MA (United States); Essig, Marco [German Cancer Research Centre (DKFZ), Department of Radiology E010, Heidelberg (Germany)

    2010-10-15

    Evaluation of brain lesions using magnetic resonance imaging (MRI) provides information that is critical for accurate diagnosis, prognosis, therapeutic intervention and monitoring response. Conventional contrast-enhanced MR neuroimaging using gadolinium (Gd) contrast agents primarily depicts disruption of the blood-brain barrier, demonstrating location and extent of disease, and also the morphological details at the lesion site. However, conventional imaging results do not always accurately predict tumour aggressiveness. Advanced functional MRI techniques such as dynamic contrast-enhanced perfusion-weighted imaging utilise contrast agents to convey physiological information regarding the haemodynamics and neoangiogenic status of the lesion that is often complementary to anatomical information obtained through conventional imaging. Most of the Gd contrast agents available have similar T1 and T2 relaxivities, and thus their contrast-enhancing capabilities are comparable. Exceptions are gadobenate-dimeglumine, Gd-EOB-DTPA, Gadobutrol and gadofosveset, which, owing to their transient-protein-binding capability, possess almost twice (and more) the T1 and T2 relaxivities as other agents at all magnetic field strengths. Numerous comparative studies have demonstrated the advantages of the increased relaxivity in terms of enhanced image contrast, image quality and diagnostic confidence. Here we summarise the benefits of higher relaxivity for the most common neuroimaging applications including MRI, perfusion-weighted imaging and MRA for evaluation of brain tumours, cerebrovascular disease and other CNS lesions. (orig.)

  2. Europium-engineered iron oxide nanocubes with high T1 and T2 contrast abilities for MRI in living subjects

    Science.gov (United States)

    Yang, Lijiao; Zhou, Zijian; Liu, Hanyu; Wu, Changqiang; Zhang, Hui; Huang, Guoming; Ai, Hua; Gao, Jinhao

    2015-04-01

    Magnetic resonance imaging (MRI) contrast agents with both positive (T1) and negative (T2) contrast abilities are needed in clinical diagnosis for fault-free accurate detection of lesions. We report a facile synthesis of europium-engineered iron oxide (EuIO) nanocubes as T1 and T2 contrast agents for MRI in living subjects. The Eu(iii) oxide-embedded iron oxide nanoparticles significantly increase the T1 relaxivity with an enhanced positive contrast effect. EuIO nanocubes with 14 nm in diameter showed a high r1 value of 36.8 mM-1 s-1 with respect to total metal ions (Fe + Eu), which is about 3 times higher than that of Fe3O4 nanoparticles with similar size. Moreover, both r1 and r2 values of EuIO nanocubes can be tuned by varying their sizes and Eu doping ratios. After citrate coating, EuIO nanocubes can provide enhanced T1 and T2 contrast effects in small animals, particularly in the cardiac and liver regions. This work may provide an insightful strategy to design MRI contrast agents with both positive and negative contrast abilities for biomedical applications.Magnetic resonance imaging (MRI) contrast agents with both positive (T1) and negative (T2) contrast abilities are needed in clinical diagnosis for fault-free accurate detection of lesions. We report a facile synthesis of europium-engineered iron oxide (EuIO) nanocubes as T1 and T2 contrast agents for MRI in living subjects. The Eu(iii) oxide-embedded iron oxide nanoparticles significantly increase the T1 relaxivity with an enhanced positive contrast effect. EuIO nanocubes with 14 nm in diameter showed a high r1 value of 36.8 mM-1 s-1 with respect to total metal ions (Fe + Eu), which is about 3 times higher than that of Fe3O4 nanoparticles with similar size. Moreover, both r1 and r2 values of EuIO nanocubes can be tuned by varying their sizes and Eu doping ratios. After citrate coating, EuIO nanocubes can provide enhanced T1 and T2 contrast effects in small animals, particularly in the cardiac and liver

  3. High-pitch dual-source CT coronary angiography with low volumes of contrast medium

    Energy Technology Data Exchange (ETDEWEB)

    Lembcke, Alexander; Hein, Patrick A.; Knobloch, Gesine; Durmus, Tahir; Hamm, Bernd [Charite - University Medicine Berlin, Department of Radiology, Berlin (Germany); Schwenke, Carsten [SCO:SSiS - Schwenke Consulting, Berlin (Germany); Huppertz, Alexander [Charite - University Medicine Berlin, Department of Radiology, Berlin (Germany); ISI - Imaging Science Institute Charite, Berlin (Germany)

    2014-01-15

    To assess the effect of lower volumes of contrast medium (CM) on image quality in high-pitch dual-source computed tomography coronary angiography (CTCA). One-hundred consecutive patients (body weight 65-85 kg, stable heart rate ≤65 bpm, cardiac index ≥2.5 L/min/m{sup 2}) referred for CTCA were prospectively enrolled. Patients were randomly assigned to one of five groups of different CM volumes (G{sub 30}, 30 mL; G{sub 40}, 40 mL; G{sub 50}, 50 mL; G{sub 60}, 60 mL; G{sub 70}, 70 mL; flow rate 5 mL/s each, iodine content 370 mg/mL). Attenuation within the proximal and distal coronary artery segments was analysed. Mean attenuation for men and women ranged from 345.0 and 399.1 HU in G{sub 30} to 478.2 and 571.8 HU in G{sub 70}. Mean attenuation values were higher in groups with higher CM volumes (P < 0.0001) and higher in women than in men (P < 0.0001). The proportions of segments with attenuation of at least 300 HU in G{sub 30}, G{sub 40}, G{sub 50}, G{sub 60} and G{sub 70} were 89 %, 95 %, 98 %, 98 % and 99 %. CM volume of 30 mL in women and 40 mL in men proved to be sufficient to guarantee attenuation of at least 300 HU. In selected patients high-pitch dual-source CTCA can be performed with CM volumes of 40 mL in men or 30 mL in women. (orig.)

  4. The effects of time, luminance, and high contrast targets: revisiting grating acuity in the domestic cat.

    Science.gov (United States)

    Clark, Daria L; Clark, Robert A

    2013-11-01

    Based on optical clarity and retinal cone density, the cat has a potential acuity of 20-30 cycles per degree (cpd), yet most behavioral studies estimate feline acuity between 3 and 9 cpd. Those studies, however, were limited by restrictive experimental conditions that may have inadvertently lowered the estimated grating acuity. Two domestic cats previously trained on a two-choice visual discrimination task were retrained on a grating detection/discrimination task with unlimited time, high luminance, high contrast targets, and adequate space to prevent poor accommodation from affecting the results. Initially, vertical gratings of increasing cpd were tested until failure. Then, horizontal gratings of increasing cpd were tested until failure. Finally, the finest horizontal grating resolved was confirmed with a third test requiring 24 correct out of 36 consecutive trials, yielding a binomial probability less than 0.02 of non-random occurrence. M1, a 7-year-old male gray tabby with +2.00 OU refraction, tested for a grating detection acuity of 15 cpd for both vertical and horizontal gratings (binomial probability = 0.009). F1, a 2-year-old female gray tabby with +0.25 OU refraction, tested for a grating orientation discrimination acuity of 20 cpd for both vertical and horizontal gratings (binomial probability = 0.004). These results demonstrate that a young cat with good focus is capable of discriminating 20 cpd, in close agreement with the physiologic maximum. Uncorrected focusing errors appear to degrade visual performance. Optimum experimental conditions resulted in better grating acuity measurements than previously reported, emphasizing the importance of environmental factors in feline behavioral testing.

  5. Multilevel markov chain monte carlo method for high-contrast single-phase flow problems

    KAUST Repository

    Efendiev, Yalchin R.

    2014-12-19

    In this paper we propose a general framework for the uncertainty quantification of quantities of interest for high-contrast single-phase flow problems. It is based on the generalized multiscale finite element method (GMsFEM) and multilevel Monte Carlo (MLMC) methods. The former provides a hierarchy of approximations of different resolution, whereas the latter gives an efficient way to estimate quantities of interest using samples on different levels. The number of basis functions in the online GMsFEM stage can be varied to determine the solution resolution and the computational cost, and to efficiently generate samples at different levels. In particular, it is cheap to generate samples on coarse grids but with low resolution, and it is expensive to generate samples on fine grids with high accuracy. By suitably choosing the number of samples at different levels, one can leverage the expensive computation in larger fine-grid spaces toward smaller coarse-grid spaces, while retaining the accuracy of the final Monte Carlo estimate. Further, we describe a multilevel Markov chain Monte Carlo method, which sequentially screens the proposal with different levels of approximations and reduces the number of evaluations required on fine grids, while combining the samples at different levels to arrive at an accurate estimate. The framework seamlessly integrates the multiscale features of the GMsFEM with the multilevel feature of the MLMC methods following the work in [26], and our numerical experiments illustrate its efficiency and accuracy in comparison with standard Monte Carlo estimates. © Global Science Press Limited 2015.

  6. Hippocampal NMDA receptors are involved in rats' spontaneous object recognition only under high memory load condition.

    Science.gov (United States)

    Sugita, Manami; Yamada, Kazuo; Iguchi, Natsumi; Ichitani, Yukio

    2015-10-22

    The possible involvement of hippocampal N-methyl-D-aspartate (NMDA) receptors in spontaneous object recognition was investigated in rats under different memory load conditions. We first estimated rats' object memory span using 3-5 objects in "Different Objects Task (DOT)" in order to confirm the highest memory load condition in object recognition memory. Rats were allowed to explore a field in which 3 (3-DOT), 4 (4-DOT), or 5 (5-DOT) different objects were presented. After a delay period, they were placed again in the same field in which one of the sample objects was replaced by another object, and their object exploration behavior was analyzed. Rats could differentiate the novel object from the familiar ones in 3-DOT and 4-DOT but not in 5-DOT, suggesting that rats' object memory span was about 4. Then, we examined the effects of hippocampal AP5 infusion on performance in both 2-DOT (2 different objects were used) and 4-DOT. The drug treatment before the sample phase impaired performance only in 4-DOT. These results suggest that hippocampal NMDA receptors play a critical role in spontaneous object recognition only when the memory load is high.

  7. Contrast Materials

    Science.gov (United States)

    ... Physician Resources Professions Site Index A-Z Contrast Materials What are contrast materials and how do they ... material? Pregnancy and contrast materials What are contrast materials and how do they work? Contrast materials, also ...

  8. High resolution laboratory grating-based x-ray phase-contrast CT

    Science.gov (United States)

    Viermetz, Manuel P.; Birnbacher, Lorenz J. B.; Fehringer, Andreas; Willner, Marian; Noel, Peter B.; Pfeiffer, Franz; Herzen, Julia

    2017-03-01

    Grating-based phase-contrast computed tomography (gbPC-CT) is a promising imaging method for imaging of soft tissue contrast without the need of any contrast agent. The focus of this study is the increase in spatial resolution without loss in sensitivity to allow visualization of pathologies comparable to the convincing results obtained at the synchrotron. To improve the effective pixel size a super-resolution reconstruction based on subpixel shifts involving a deconvolution of the image is applied on differential phase-contrast data. In our study we could achieve an effective pixel sizes of 28mm without any drawback in terms of sensitivity or the ability to measure quantitative data.

  9. Compressive Phase Contrast Tomography

    CERN Document Server

    Maia, F R N C; Marchesini, S; Padmore, H A; Parkinson, D Y; Pien, J; Schirotzek, A; Yang, C; 10.1117/12.861946

    2010-01-01

    When x-rays penetrate soft matter, their phase changes more rapidly than their amplitude. In- terference effects visible with high brightness sources creates higher contrast, edge enhanced images. When the object is piecewise smooth (made of big blocks of a few components), such higher con- trast datasets have a sparse solution. We apply basis pursuit solvers to improve SNR, remove ring artifacts, reduce the number of views and radiation dose from phase contrast datasets collected at the Hard X-Ray Micro Tomography Beamline at the Advanced Light Source. We report a GPU code for the most computationally intensive task, the gridding and inverse gridding algorithm (non uniform sampled Fourier transform).

  10. Evaluation of fast highly undersampled contrast-enhanced MR angiography (sparse CE-MRA) in intracranial applications - initial study

    Energy Technology Data Exchange (ETDEWEB)

    Gratz, Marcel; Quick, Harald H. [University of Duisburg-Essen, Erwin L. Hahn Institute for MR Imaging, Essen (Germany); University Hospital Essen, High Field and Hybrid MR Imaging, Essen (Germany); Schlamann, Marc [University Hospital Giessen and Marburg GmbH, Neuroradiology, Giessen (Germany); University Hospital Essen, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen (Germany); Goericke, Sophia [University Hospital Essen, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen (Germany); Maderwald, Stefan [University of Duisburg-Essen, Erwin L. Hahn Institute for MR Imaging, Essen (Germany)

    2017-03-15

    To assess the image quality of sparsely sampled contrast-enhanced MR angiography (sparse CE-MRA) providing high spatial resolution and whole-head coverage. Twenty-three patients scheduled for contrast-enhanced MR imaging of the head, (N = 19 with intracranial pathologies, N = 9 with vascular diseases), were included. Sparse CE-MRA at 3 Tesla was conducted using a single dose of contrast agent. Two neuroradiologists independently evaluated the data regarding vascular visibility and diagnostic value of overall 24 parameters and vascular segments on a 5-point ordinary scale (5 = very good, 1 = insufficient vascular visibility). Contrast bolus timing and the resulting arterio-venous overlap was also evaluated. Where available (N = 9), sparse CE-MRA was compared to intracranial Time-of-Flight MRA. The overall rating across all patients for sparse CE-MRA was 3.50 ± 1.07. Direct influence of the contrast bolus timing on the resulting image quality was observed. Overall mean vascular visibility and image quality across different features was rated good to intermediate (3.56 ± 0.95). The average performance of intracranial Time-of-Flight was rated 3.84 ± 0.87 across all patients and 3.54 ± 0.62 across all features. Sparse CE-MRA provides high-quality 3D MRA with high spatial resolution and whole-head coverage within short acquisition time. Accurate contrast bolus timing is mandatory. (orig.)

  11. Calibrating apodizer fabrication techniques for high-contrast coronagraphs on segmented and monolithic space telescopes

    Science.gov (United States)

    Sivaramakrishnan, Anand; Greenbaum, Alexandra Z.; Carr, G. Lawrence; Smith, Randy J.; Xi, Xiaoxiang; Zimmerman, Neil T.

    2013-09-01

    High contrast imaging can use pupil apodizers to suppress diffracted starlight from a bright source in order to observe its environs. Metallic half-tone dot transmissive apodizers were developed for the Gemini Planet Imager (GPI) and ESO SPHERE coronagraphs for use in the near-IR. Dot sizes on the scale of the wavelength of the light often result in unexpected variations in the optical transmission vs. superficial dot density relation. We measured 5 and 10 micron half-tone microdot screens' transmissions between 550 -1050 nm to prepare to fabricate apodizations that mitigate diffraction by segments gaps and spiders on future large space telescopes. We utilized slow test beams (f/40, f/80) to estimate the on-axis (far-field, or zero-order) transmission of test patches using a Fourier Transform Spectrograph on Beamline U10B at Brookhaven National Laboratory's National Synchrotron Light Source (BNL NSLS). We also modified our previous GPI IR characterization hardware and methods for this experiment. Our measurements show an internal consistency of 0.1% in transmission, a factor of 5 better than our near-IR GPI work on the NSLS U4IR beamline. The systematics of the set-up appeared to limit the absolute calibration for our f/40 data on the 50-patch, maximum Optical Density 3 (OD3), sample. Credible measurements of transmissions down to about 3% transmission were achieved for this sample. Future work on apodizers for obstructed and segmented primary mirror coronagraphs will require configurations that mimic the intended diffractive configurations closely in order to tune apodizer fabrication to any particular application, and measure chromatic effects in representative diffractive regimes. Further experimental refinements are needed to measure the densest test patches which possess transmissions less than a few percent. The new NSLS-II should provide much greater spectral stability of its synchrotron beam, which will improve measurement accuracy and reduce systematics.

  12. HIGH-CONTRAST NEAR-INFRARED POLARIZATION IMAGING OF MWC480

    Energy Technology Data Exchange (ETDEWEB)

    Kusakabe, N.; Hashimoto, J.; Kudo, T. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Grady, C. A. [Eureka Scientific, 2452 Delmer St., Suite 100, Oakland, CA 96402 (United States); Sitko, M. L.; Werren, C.; Day, A. N.; Beerman, L. C. [Department of Physics, University of Cincinnati, Cincinnati, OH 45221 (United States); Fukagawa, M. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1, Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Muto, T. [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551 (Japan); Wisniewski, J. P. [Department of Astronomy, University of Washington, Box 351580 Seattle, Washington, DC (United States); Min, M. [Astronomical Institute ' Anton Pannekoek' Science Park 904 1098 XH Amsterdam (Netherlands); Mayama, S. [Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies, Shonan International Village Hayama-cho, Miura-gun, Kanagawa (Japan); Lynch, D. K.; Russell, R. W. [The Aerospace Corporation, Los Angeles, CA 90009 (United States); Brafford, S. M. [Brafford and Phillips, Batavia, OH 45103 (United States); Kuzuhara, M. [Department of Earth and Planetary Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033 (Japan); Brandt, T. D. [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States); Abe, L. [Laboratoire Lagrange, UMR7293, Universite Le de Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d' fAzur, 06300 Nice (France); Brandner, W., E-mail: nb.kusakabe@nao.ac.jp [Max Planck Institute for Astronomy, 69117 Heidelberg, Koenigstuhl 17 (Germany); and others

    2012-07-10

    One of the key predictions of modeling from the IR excess of Herbig Ae stars is that for protoplanetary disks, where significant grain growth and settling has occurred, the dust disk has flattened to the point that it can be partially or largely shadowed by the innermost material at or near the dust sublimation radius. When the self-shadowing has already started, the outer disk is expected to be detected in scattered light only in the exceptional cases when the scale height of the dust disk at the sublimation radius is smaller than usual. High-contrast imaging combined with the IR spectral energy distribution allow us to measure the degree of flattening of the disk, as well as to determine the properties of the outer disk. We present polarimetric differential imaging in the H band obtained with Subaru/HiCIAO of one such system, MWC 480. The HiCIAO data were obtained at a historic minimum of the NIR excess. The disk is detected in scattered light from 0.''2 to 1.''0 (27.4-137 AU). Together with the marginal detection of the disk from 1998 February 24 by Hubble Space Telescope/NICMOS, our data constrain the opening half-angle for the disk to lie between 1.{sup 0}3 {<=}{theta} {<=} 2.{sup 0}2. When compared with similar measures in CO for the gas disk from the literature, the dust disk subtends only {approx}30% of the gas disk scale height (H/R {approx} 0.03). Such a dust disk is a factor of 5-7 flatter than transitional disks, which have structural signatures that giant planets have formed.

  13. The effect of laser contrast on generation of highly charged Fe ions by ultra-intense femtosecond laser pulses

    Science.gov (United States)

    Faenov, Anatoly Ya.; Alkhimova, Maria A.; Pikuz, Tatiana A.; Skobelev, Igor Yu.; Nishiuchi, Mamiko; Sakaki, Hironao; Pirozhkov, Alexander S.; Sagisaka, Akito; Dover, Nicholas P.; Kondo, Kotaro; Ogura, Koichi; Fukuda, Yuji; Kiriyama, Hiromitsu; Andreev, Alexander; Nishitani, Keita; Miyahara, Takumi; Watanabe, Yukinobu; Pikuz, Sergey A.; Kando, Masaki; Kodama, Ruosuke; Kondo, Kiminori

    2017-07-01

    Experimental studies on the formation of highly charged ions of medium-Z elements using femtosecond laser pulses with different contrast levels were carried out. Multiply charged Fe ions were generated by laser pulses with 35 fs duration and an intensity exceeding 1021 W/cm2. Using high-resolution X-ray spectroscopic methods, bulk electron temperature of the generated plasma has been identified. It is shown that the presence of a laser pre-pulse at a contrast level of 105-106 with respect to the main pulse drastically decreases the degree of Fe ionization. We conclude that an effective source of energetic, multiply charged moderate and high- Z ions based on femtosecond laser-plasma interactions can be created only using laser pulses of ultra-high contrast.

  14. High-resolution blood-pool-contrast-enhanced MR angiography in glioblastoma: tumor-associated neovascularization as a biomarker for patient survival. A preliminary study.

    Science.gov (United States)

    Puig, Josep; Blasco, Gerard; Daunis-I-Estadella, Josep; Alberich-Bayarri, Angel; Essig, Marco; Jain, Rajan; Remollo, Sebastián; Hernández, David; Puigdemont, Montserrat; Sánchez-González, Javier; Mateu, Gloria; Wintermark, Max; Pedraza, Salvador

    2016-01-01

    The objective of the study was to determine whether tumor-associated neovascularization on high-resolution gadofosveset-enhanced magnetic resonance angiography (MRA) is a useful biomarker for predicting survival in patients with newly diagnosed glioblastomas. Before treatment, 35 patients (25 men; mean age, 64 ± 14 years) with glioblastoma underwent MRI including first-pass dynamic susceptibility contrast (DSC) perfusion and post-contrast T1WI sequences with gadobutrol (0.1 mmol/kg) and, 48 h later, high-resolution MRA with gadofosveset (0.03 mmol/kg). Volumes of interest for contrast-enhancing lesion (CEL), non-CEL, and contralateral normal-appearing white matter were obtained, and DSC perfusion and DWI parameters were evaluated. Prognostic factors were assessed by Kaplan-Meier survival and Cox proportional hazards model. Eighteen (51.42 %) glioblastomas were hypervascular on high-resolution MRA. Hypervascular glioblastomas were associated with higher CEL volume and lower Karnofsky score. Median survival rates for patients with hypovascular and hypervascular glioblastomas treated with surgery, radiotherapy, and chemotherapy were 15 and 9.75 months, respectively (P contrast-enhanced MRA of newly diagnosed glioblastoma seems to be a useful biomarker that correlates with worse survival.

  15. Robust Design by Antioptimization for Parameter Tolerant GaAs/AlOx High Contrast Grating Mirror for VCSEL Application

    CERN Document Server

    Chevallier, Christyves; Fressengeas, Nicolas; Jacquet, Joel

    2013-01-01

    A GaAs/AlOx high contrast grating structure design which exhibits a 99.5% high reflectivity for a 425nm large bandwidth is reported. The high contrast grating (HCG) structure has been designed in order to enhance the properties of mid-infrared VCSEL devices by replacing the top Bragg mirror of the cavity. A robust optimization algorithm has been implemented to design the HCG structure not only as an efficient mirror but also as a robust structure against the imperfections of fabrication. The design method presented here can be easily adapted for other HCG applications at different wavelengths.

  16. Contrast-enhanced ultra-high-field liver MRI: A feasibility trial

    Energy Technology Data Exchange (ETDEWEB)

    Umutlu, Lale, E-mail: Lale.Umutlu@uk-essen.de [Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen (Germany); Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); Bitz, Andreas K.; Maderwald, Stefan; Orzada, Stephan; Kinner, Sonja; Kraff, Oliver; Brote, Irina; Ladd, Susanne C.; Schroeder, Tobias; Forsting, Michael; Antoch, Gerald; Ladd, Mark E. [Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen (Germany); Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); Quick, Harald H. [Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany); Institute of Medical Physics, University Nuernberg-Erlangen (Germany); Lauenstein, Thomas C. [Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen (Germany); Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany)

    2013-05-15

    The aim of this study was to investigate the feasibility of dynamic contrast-enhanced 7 T MRI of the liver using an eight-channel radiofrequency (RF) transmit/receive body-coil. 16 healthy subjects were examined on a 7 T MR system utilizing a custom-built eight-channel RF body-coil suitable for RF-shimming. The following data were acquired: (1) steady state free precession imaging, (2) T2w turbo spin echo imaging, (3) T1w in and opposed-phase imaging, (4) T1w 3D FLASH images pre-contrast and in arterial, portal-venous and venous phase and (5) a fat-saturated pre- and post-contrast 2D FLASH sequence. Visual evaluation of (1) the delineation of liver vasculature, (2) the overall image quality, and (3) artifact presence and consequent image impairment was performed. SNR of the liver parenchyma was measured for the contrast-enhanced 2D and 3D FLASH sequences. For statistical analysis, a Wilcoxon-Rank Test was used. Best delineation of non-enhanced liver vasculature and overall image quality was found for 2D FLASH MRI, with only slight improvement in vessel conspicuity after the application of contrast media. T2-weighted TSE imaging remained strongly impaired, falling short of diagnostic relevance and precluding a clinical application. Our results demonstrate the feasibility and diagnostic potential of dedicated contrast-enhanced 7 T liver MRI as well as the potential for non-contrast-enhanced angiographic application.

  17. One-step patterning of double tone high contrast and high refractive index inorganic spin-on resist

    Science.gov (United States)

    Zanchetta, E.; Della Giustina, G.; Brusatin, G.

    2014-09-01

    A direct one-step and low temperature micro-fabrication process, enabling to realize large area totally inorganic TiO2 micro-patterns from a spin-on resist, is presented. High refractive index structures (up to 2 at 632 nm) without the need for transfer processes have been obtained by mask assisted UV lithography, exploiting photocatalytic titania properties. A distinctive feature not shared by any of the known available resists and boosting the material versatility, is that the system behaves either as a positive or as negative tone resist, depending on the process parameters and on the development chemistry. In order to explain the resist double tone behavior, deep comprehension of the lithographic process parameters optimization and of the resist chemistry and structure evolution during the lithographic process, generally uncommon in literature, is reported. Another striking property of the presented resist is that the negative tone shows a high contrast up to 19, allowing to obtain structures resolution down to 2 μm wide. The presented process and material permit to directly fabricate different titania geometries of great importance for solar cells, photo-catalysis, and photonic crystals applications.

  18. Depiction of normal gastrointestinal anatomy with MDCT: Comparison of low- and high-attenuation oral contrast media

    Energy Technology Data Exchange (ETDEWEB)

    Erturk, Sukru Mehmet [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115 (United States)], E-mail: mehmeterturk@superonline.com; Mortele, Koenraad J.; Oliva, Maria-Raquel; Ichikawa, Tomoaki; Silverman, Stuart G. [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115 (United States); Cantisani, Vito; Pagliara, Elisa [Department of Radiological Sciences, Policlinico Umberto I, University La Sapienza, Rome (Italy); Ros, Pablo R. [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115 (United States)

    2008-04-15

    Purpose: To compare low- and high-attenuation oral contrast media for depiction of normal gastrointestinal anatomy with multidetector-row computed tomography (MDCT). Materials and methods: A prospective, randomized study of 90 consecutive patients without known or suspected gastrointestinal disease was conducted after the approval of our Institutional Review Board. All patients underwent IV contrast-enhanced abdominal and pelvic CT scans after oral administration of 900 ml of either low- or high-attenuation barium sulphate suspension. Using a five-point scale, two radiologists independently graded distention and wall visualization of stomach, duodenum, jejunum, and ileum. The degree of distention and wall visualization was compared using Mann-Whitney U-test. Results: Duodenal, jejunal and ileal distention (p < 0.05, <0.001, <0.001, respectively) and wall visualization (p < 0.05, <0.01, <0.05, respectively) scores with low-attenuation contrast medium were significantly higher than those with high-attenuation barium sulphate preparation, for reader 1. Duodenal and jejunal wall visualization scores with low-attenuation contrast medium (p < 0.05, <0.01, respectively) were significantly higher than those with high-attenuation contrast medium, for reader 2. Interobserver agreement was fair to good for both distention ({kappa}-range: 0.41-0.74) and wall visualization ({kappa}-range: 0.48-0.71). Conclusion: MDCT with low-attenuation contrast medium provides distention and wall visualization of the GI tract that is equal or better than high-attenuation contrast medium.

  19. Europium-engineered iron oxide nanocubes with high T1 and T2 contrast abilities for MRI in living subjects.

    Science.gov (United States)

    Yang, Lijiao; Zhou, Zijian; Liu, Hanyu; Wu, Changqiang; Zhang, Hui; Huang, Guoming; Ai, Hua; Gao, Jinhao

    2015-04-21

    Magnetic resonance imaging (MRI) contrast agents with both positive (T1) and negative (T2) contrast abilities are needed in clinical diagnosis for fault-free accurate detection of lesions. We report a facile synthesis of europium-engineered iron oxide (EuIO) nanocubes as T1 and T2 contrast agents for MRI in living subjects. The Eu(iii) oxide-embedded iron oxide nanoparticles significantly increase the T1 relaxivity with an enhanced positive contrast effect. EuIO nanocubes with 14 nm in diameter showed a high r1 value of 36.8 mM(-1) s(-1) with respect to total metal ions (Fe + Eu), which is about 3 times higher than that of Fe3O4 nanoparticles with similar size. Moreover, both r1 and r2 values of EuIO nanocubes can be tuned by varying their sizes and Eu doping ratios. After citrate coating, EuIO nanocubes can provide enhanced T1 and T2 contrast effects in small animals, particularly in the cardiac and liver regions. This work may provide an insightful strategy to design MRI contrast agents with both positive and negative contrast abilities for biomedical applications.

  20. Self-rated social skills predict visual perception: impairments in object discrimination requiring transient attention associated with high autistic tendency.

    Science.gov (United States)

    Laycock, Robin; Cross, Alana Jade; Dalle Nogare, Felicity; Crewther, Sheila Gillard

    2014-02-01

    Autism is usually defined by impairments in the social domain but has also been linked to deficient dorsal visual stream processing. However, inconsistent findings make the nature of this relationship unclear and thus, we examined the role of stimulus-driven transient attention, presumably activated by the dorsal stream in autistic tendency. Contrast thresholds for object discrimination were compared between groups with high and low self-rated autistic tendency utilizing the socially based Autism Spectrum Quotient (AQ). Visual stimuli were presented with either abrupt or with ramped contrast onsets/offsets in order to manipulate the demands of transient attention. Larger impairments in performance of abrupt compared with ramped object presentation were established in the high AQ group. Furthermore, self-reported social skills predicted abrupt task performance, suggesting an important visual perception deficiency in autism-related traits. Autism spectrum disorder may be associated with reduced utilization of the dorsal stream to rapidly activate attention prior to ventral stream processing when stimuli are transient. © 2013 International Society for Autism Research, Wiley Periodicals, Inc.

  1. A High-Fidelity Solar System Model and High-Contrast Integral Field Spectrograph Prototype for Exoplanet Observations

    Science.gov (United States)

    Wilkins, A. N.; McElwain, M. W.; Roberge, A.; Nesvold, E.; Stark, C. C.; Kuchner, M. J.; Robinson, T.; Meadows, V. S.; Straughn, A. N.; Turnbull, M. C.; Gong, Q.; Woodgate, B.; Brandt, T.; Staplefelt, K.; Heap, S.; Hilton, G.

    2014-03-01

    As the possibility of discovering habitable, Earth-like planets around Sun-like stars improves, the need for both accurate model representations of such systems and advanced, dedicated high-contrast instrumentation in order to characterize and understand such systems becomes ever more pressing. We present a model and an instrument to address this need. The signals of habitability will be buried within spectral information like needles in haystacks, so we present a complete model of the Solar System we call "Hackstacks" that can be readily placed at various distances and inclinations to simulate an exoplanetary system with a known habitable planet. The Haystacks data product is a three-dimensional spectral cube. The spatial x-y plane spans 150 AU in both directions, centered on the Sun. The spectral zdimension is divided into four hundred slices ranging from 0.3 µm to 2.5 µm, evenly spaced in wavelength, yielding R ~ 200 in the V-band. In the model, we include the Solar System planets, inner (exo)zodiacal dust, outer Kuiper Belt dust, and extragalactic background, all sourced from a combination of observations and models. This makes the Haystacks model the most comprehensive, robust, and detailed model available for prediction of noise levels, confusion, and the ability to measure biomarkers in a directly observed system. The final data cubes are available for download by the public. Any user who accesses our NASA-hosted webpage simply inputs a desire wavelength range, a distance, and an inclination, and they are provided with the corresponding spectral cube. We demonstrate the power of such data cubes with several simulations of observations with various telescopes and instruments using the PROPER suite of algorithms, and present preliminary results on detectability and necessary instrument/telescope capabilities. In order to both detect and analyze an Earth-like planet in another system, we need an instrument dedicated to such a task, with high-contrast imaging

  2. High-resolution contrast-enhanced optical coherence tomography in mice retinae

    Science.gov (United States)

    Sen, Debasish; SoRelle, Elliott D.; Liba, Orly; Dalal, Roopa; Paulus, Yannis M.; Kim, Tae-Wan; Moshfeghi, Darius M.; de la Zerda, Adam

    2016-06-01

    Optical coherence tomography (OCT) is a noninvasive interferometric imaging modality providing anatomical information at depths of millimeters and a resolution of micrometers. Conventional OCT images limit our knowledge to anatomical structures alone, without any contrast enhancement. Therefore, here we have, for the first time, optimized an OCT-based contrast-enhanced imaging system for imaging single cells and blood vessels in vivo inside the living mouse retina at subnanomolar sensitivity. We used bioconjugated gold nanorods (GNRs) as exogenous OCT contrast agents. Specifically, we used anti-mouse CD45 coated GNRs to label mouse leukocytes and mPEG-coated GNRs to determine sensitivity of GNR detection in vivo inside mice retinae. We corroborated OCT observations with hyperspectral dark-field microscopy of formalin-fixed histological sections. Our results show that mouse leukocytes that otherwise do not produce OCT contrast can be labeled with GNRs leading to significant OCT intensity equivalent to a 0.5 nM GNR solution. Furthermore, GNRs injected intravenously can be detected inside retinal blood vessels at a sensitivity of ˜0.5 nM, and GNR-labeled cells injected intravenously can be detected inside retinal capillaries by enhanced OCT contrast. We envision the unprecedented resolution and sensitivity of functionalized GNRs coupled with OCT to be adopted for longitudinal studies of retinal disorders.

  3. Peripheral Vasculature: High-Temporal- and High-Spatial-Resolution Three-dimensional Contrast-enhanced MR Angiography1

    Science.gov (United States)

    Haider, Clifton R.; Glockner, James F.; Stanson, Anthony W.; Riederer, Stephen J.

    2009-01-01

    Purpose: To prospectively evaluate the feasibility of performing high-spatial-resolution (1-mm isotropic) time-resolved three-dimensional (3D) contrast material–enhanced magnetic resonance (MR) angiography of the peripheral vasculature with Cartesian acquisition with projection-reconstruction–like sampling (CAPR) and eightfold accelerated two-dimensional (2D) sensitivity encoding (SENSE). Materials and Methods: All studies were approved by the institutional review board and were HIPAA compliant; written informed consent was obtained from all participants. There were 13 volunteers (mean age, 41.9; range, 27–53 years). The CAPR sequence was adapted to provide 1-mm isotropic spatial resolution and a 5-second frame time. Use of different receiver coil element sizes for those placed on the anterior-to-posterior versus left-to-right sides of the field of view reduced signal-to-noise ratio loss due to acceleration. Results from eight volunteers were rated independently by two radiologists according to prominence of artifact, arterial to venous separation, vessel sharpness, continuity of arterial signal intensity in major arteries (anterior and posterior tibial, peroneal), demarcation of origin of major arteries, and overall diagnostic image quality. MR angiographic results in two patients with peripheral vascular disease were compared with their results at computed tomographic angiography. Results: The sequence exhibited no image artifact adversely affecting diagnostic image quality. Temporal resolution was evaluated to be sufficient in all cases, even with known rapid arterial to venous transit. The vessels were graded to have excellent sharpness, continuity, and demarcation of the origins of the major arteries. Distal muscular branches and the communicating and perforating arteries were routinely seen. Excellent diagnostic quality rating was given for 15 (94%) of 16 evaluations. Conclusion: The feasibility of performing high-diagnostic-quality time-resolved 3D

  4. Research On The Classification Of High Resolution Image Based On Object-oriented And Class Rule

    Science.gov (United States)

    Li, C. K.; Fang, W.; Dong, X. J.

    2015-06-01

    With the development of remote sensing technology, the spatial resolution, spectral resolution and time resolution of remote sensing data is greatly improved. How to efficiently process and interpret the massive high resolution remote sensing image data for ground objects, which with spatial geometry and texture information, has become the focus and difficulty in the field of remote sensing research. An object oriented and rule of the classification method of remote sensing data has presents in this paper. Through the discovery and mining the rich knowledge of spectrum and spatial characteristics of high-resolution remote sensing image, establish a multi-level network image object segmentation and classification structure of remote sensing image to achieve accurate and fast ground targets classification and accuracy assessment. Based on worldview-2 image data in the Zangnan area as a study object, using the object-oriented image classification method and rules to verify the experiment which is combination of the mean variance method, the maximum area method and the accuracy comparison to analysis, selected three kinds of optimal segmentation scale and established a multi-level image object network hierarchy for image classification experiments. The results show that the objectoriented rules classification method to classify the high resolution images, enabling the high resolution image classification results similar to the visual interpretation of the results and has higher classification accuracy. The overall accuracy and Kappa coefficient of the object-oriented rules classification method were 97.38%, 0.9673; compared with object-oriented SVM method, respectively higher than 6.23%, 0.078; compared with object-oriented KNN method, respectively more than 7.96%, 0.0996. The extraction precision and user accuracy of the building compared with object-oriented SVM method, respectively higher than 18.39%, 3.98%, respectively better than the object-oriented KNN method 21

  5. Risk of contrast-medium-induced nephropathy in high-risk patients undergoing MDCT - A pooled analysis of two randomized trials

    Energy Technology Data Exchange (ETDEWEB)

    Thomsen, Henrik S. [University of Copenhagen, Department of Diagnostic Radiology, Copenhagen University Hospital Herlev, and Department of Diagnostic Sciences, Faculty of Health Sciences, Herlev (Denmark); Morcos, Sameh K. [University of Sheffield, Department of Diagnostic Imaging, Northern General Hospital, Sheffield (United Kingdom)

    2009-04-15

    The incidence of contrast-medium-induced nephropathy (CIN) following intravenous (IV) CM administration of contrast media to renally impaired patients undergoing multidetector computed tomography (MDCT) is not well characterized. Our objective was to investigate the incidence of CIN in patients with glomerular filtration rate (GFR) <60 ml/min undergoing contrast-enhanced MDCT examinations and to compare the rates of CIN following the IV administration of low-osmolar contrast media (LOCM, iopamidol and iomeprol) and an iso-osmolar contrast medium (IOCM, iodixanol). A total of 301 adult patients with moderate-to-severe renal failure received a similar IV contrast dose (40 gI). Serum creatinine (SCr) was measured at screening, baseline and 48-72 {+-} 6 h after the MDCT examination. Primary CIN outcome was an increase in SCr {>=}0.5 mg/dl ({>=}44.2 {mu}mol/l) from baseline. The CIN rates were 2.3% in the total population, 0.6% when GFR >40 ml/min, 4.6% when GFR <40 ml/min and 7.8% in patients with GFR <30 ml/min. The incidence of CIN was significantly higher after iodixanol than after LOCM (seven patients, 4.7% following IOCM, no CIN cases following the LOCM; p = 0.007). Significant differences in favor of the LOCM were also observed in patients with GFR <40 ml/min and GFR <30 ml/min. Following the IV administration of nonionic contrast agents in patients with moderate-to-severe renal insufficiency, the risk of significant CIN seems to be low. The IOCM iodixanol caused a higher rate of CIN than the LOCM iopamidol and iomeprol, especially in high-risk patients. Differences in osmolality between these LOCM and iodixanol do not play a role in the genesis of CIN. (orig.)

  6. Estimates of the Planet Yield from Ground-Based High-Contrast Imaging Observations as a Function of Stellar Mass

    CERN Document Server

    Crepp, Justin R

    2011-01-01

    We use Monte Carlo simulations to estimate the number of extrasolar planets that are directly detectable in the solar-neighborhood using current and forthcoming high-contrast imaging instruments. Our calculations take into account the important factors that govern the likelihood for imaging a planet, including the statistical properties of nearby stars, correlations between star and planet properties, observational effects, and selection criteria. We consider several different ground-based surveys and express the resulting yields as a function of stellar mass. Selecting targets based on their youth and visual brightness, we find that strong correlations between star mass and planet properties are required to reproduce high-contrast imaging results to date. Using the most recent empirical findings for the occurrence rate of planets from RV surveys, our simulations indicate that extrapolation of the Doppler planet population to separations accessible to high-contrast instruments provides excellent agreement bet...

  7. Tracking Neptune's Migration History through High-Perihelion Resonant Trans-Neptunian Objects

    CERN Document Server

    Kaib, Nathan A

    2016-01-01

    Recently, Sheppard et al. (2016) presented the discovery of 7 new trans-Neptunian objects with perihelia beyond 40 AU with moderate eccentricities and semimajor axes over 50 AU. Like the handful of previously known bodies on similar orbits, these objects' semimajor axes are just beyond the Kuiper belt edge and clustered around mean motion resonances (MMRs) with Neptune. The objects likely obtained their observed orbits while trapped in a MMR, where the Kozai-Lidov mechanism can raise their perihelia. This mechanism generates a high-perihelion population and also weakens Neptune's dynamical influence over these objects. Here we numerically model the production of this population under a variety of different migration scenarios for Neptune, varying both migration speed and migration smoothness. We find that high-perihelion objects near Neptunian MMRs constrain the nature of Neptune's migration. In particular, the population near the 3:1 MMR (near 62 AU) is especially useful due to its large population and short...

  8. Improved dosimetry in prostate brachytherapy using high resolution contrast enhanced magnetic resonance imaging: a feasibility study

    Science.gov (United States)

    Morancy, Tye; Kaplan, Irving; Qureshi, Muhammad M.; Hirsch, Ariel E.; Rofksy, Neil M.; Holupka, Edward; Oismueller, Renee; Hawliczek, Robert; Helbich, Thomas H.; Bloch, B. Nicolas

    2014-01-01

    Purpose To assess detailed dosimetry data for prostate and clinical relevant intra- and peri-prostatic structures including neurovascular bundles (NVB), urethra, and penile bulb (PB) from postbrachytherapy computed tomography (CT) versus high resolution contrast enhanced magnetic resonance imaging (HR-CEMRI). Material and methods Eleven postbrachytherapy prostate cancer patients underwent HR-CEMRI and CT imaging. Computed tomography and HR-CEMRI images were randomized and 2 independent expert readers created contours of prostate, intra- and peri-prostatic structures on each CT and HR-CEMRI scan for all 11 patients. Dosimetry data including V100, D90, and D100 was calculated from these contours. Results Mean V100 values from CT and HR-CEMRI contours were as follows: prostate (98.5% and 96.2%, p = 0.003), urethra (81.0% and 88.7%, p = 0.027), anterior rectal wall (ARW) (8.9% and 2.8%, p < 0.001), left NVB (77.9% and 51.5%, p = 0.002), right NVB (69.2% and 43.1%, p = 0.001), and PB (0.09% and 11.4%, p = 0.005). Mean D90 (Gy) derived from CT and HR-CEMRI contours were: prostate (167.6 and 150.3, p = 0.012), urethra (81.6 and 109.4, p = 0.041), ARW (2.5 and 0.11, p = 0.003), left NVB (98.2 and 58.6, p = 0.001), right NVB (87.5 and 55.5, p = 0.001), and PB (11.2 and 12.4, p = 0.554). Conclusions Findings of this study suggest that HR-CEMRI facilitates accurate and meaningful dosimetric assessment of prostate and clinically relevant structures, which is not possible with CT. Significant differences were seen between CT and HR-CEMRI, with volume overestimation of CT derived contours compared to HR-CEMRI. PMID:25834576

  9. A multiscale restriction-smoothed basis method for high contrast porous media represented on unstructured grids

    Science.gov (United States)

    Møyner, Olav; Lie, Knut-Andreas

    2016-01-01

    A wide variety of multiscale methods have been proposed in the literature to reduce runtime and provide better scaling for the solution of Poisson-type equations modeling flow in porous media. We present a new multiscale restricted-smoothed basis (MsRSB) method that is designed to be applicable to both rectilinear grids and unstructured grids. Like many other multiscale methods, MsRSB relies on a coarse partition of the underlying fine grid and a set of local prolongation operators (multiscale basis functions) that map unknowns associated with the fine grid cells to unknowns associated with blocks in the coarse partition. These mappings are constructed by restricted smoothing: Starting from a constant, a localized iterative scheme is applied directly to the fine-scale discretization to compute prolongation operators that are consistent with the local properties of the differential operators. The resulting method has three main advantages: First of all, both the coarse and the fine grid can have general polyhedral geometry and unstructured topology. This means that partitions and good prolongation operators can easily be constructed for complex models involving high media contrasts and unstructured cell connections introduced by faults, pinch-outs, erosion, local grid refinement, etc. In particular, the coarse partition can be adapted to geological or flow-field properties represented on cells or faces to improve accuracy. Secondly, the method is accurate and robust when compared to existing multiscale methods and does not need expensive recomputation of local basis functions to account for transient behavior: Dynamic mobility changes are incorporated by continuing to iterate a few extra steps on existing basis functions. This way, the cost of updating the prolongation operators becomes proportional to the amount of change in fluid mobility and one reduces the need for expensive, tolerance-based updates. Finally, since the MsRSB method is formulated on top of a cell

  10. Contrasting the Chromosomal Organization of Repetitive DNAs in Two Gryllidae Crickets with Highly Divergent Karyotypes.

    Science.gov (United States)

    Palacios-Gimenez, Octavio M; Carvalho, Carlos Roberto; Ferrari Soares, Fernanda Aparecida; Cabral-de-Mello, Diogo C

    2015-01-01

    A large percentage of eukaryotic genomes consist of repetitive DNA that plays an important role in the organization, size and evolution. In the case of crickets, chromosomal variability has been found using classical cytogenetics, but almost no information concerning the organization of their repetitive DNAs is available. To better understand the chromosomal organization and diversification of repetitive DNAs in crickets, we studied the chromosomes of two Gryllidae species with highly divergent karyotypes, i.e., 2n(♂) = 29,X0 (Gryllus assimilis) and 2n = 9, neo-X1X2Y (Eneoptera surinamensis). The analyses were performed using classical cytogenetic techniques, repetitive DNA mapping and genome-size estimation. Conserved characteristics were observed, such as the occurrence of a small number of clusters of rDNAs and U snDNAs, in contrast to the multiple clusters/dispersal of the H3 histone genes. The positions of U2 snDNA and 18S rDNA are also conserved, being intermingled within the largest autosome. The distribution and base-pair composition of the heterochromatin and repetitive DNA pools of these organisms differed, suggesting reorganization. Although the microsatellite arrays had a similar distribution pattern, being dispersed along entire chromosomes, as has been observed in some grasshopper species, a band-like pattern was also observed in the E. surinamensis chromosomes, putatively due to their amplification and clustering. In addition to these differences, the genome of E. surinamensis is approximately 2.5 times larger than that of G. assimilis, which we hypothesize is due to the amplification of repetitive DNAs. Finally, we discuss the possible involvement of repetitive DNAs in the differentiation of the neo-sex chromosomes of E. surinamensis, as has been reported in other eukaryotic groups. This study provided an opportunity to explore the evolutionary dynamics of repetitive DNAs in two non-model species and will contribute to the understanding of

  11. Contrasting the Chromosomal Organization of Repetitive DNAs in Two Gryllidae Crickets with Highly Divergent Karyotypes.

    Directory of Open Access Journals (Sweden)

    Octavio M Palacios-Gimenez

    Full Text Available A large percentage of eukaryotic genomes consist of repetitive DNA that plays an important role in the organization, size and evolution. In the case of crickets, chromosomal variability has been found using classical cytogenetics, but almost no information concerning the organization of their repetitive DNAs is available. To better understand the chromosomal organization and diversification of repetitive DNAs in crickets, we studied the chromosomes of two Gryllidae species with highly divergent karyotypes, i.e., 2n(♂ = 29,X0 (Gryllus assimilis and 2n = 9, neo-X1X2Y (Eneoptera surinamensis. The analyses were performed using classical cytogenetic techniques, repetitive DNA mapping and genome-size estimation. Conserved characteristics were observed, such as the occurrence of a small number of clusters of rDNAs and U snDNAs, in contrast to the multiple clusters/dispersal of the H3 histone genes. The positions of U2 snDNA and 18S rDNA are also conserved, being intermingled within the largest autosome. The distribution and base-pair composition of the heterochromatin and repetitive DNA pools of these organisms differed, suggesting reorganization. Although the microsatellite arrays had a similar distribution pattern, being dispersed along entire chromosomes, as has been observed in some grasshopper species, a band-like pattern was also observed in the E. surinamensis chromosomes, putatively due to their amplification and clustering. In addition to these differences, the genome of E. surinamensis is approximately 2.5 times larger than that of G. assimilis, which we hypothesize is due to the amplification of repetitive DNAs. Finally, we discuss the possible involvement of repetitive DNAs in the differentiation of the neo-sex chromosomes of E. surinamensis, as has been reported in other eukaryotic groups. This study provided an opportunity to explore the evolutionary dynamics of repetitive DNAs in two non-model species and will contribute to the

  12. Tandem-pulsed acousto-optics: an analytical framework of modulated high-contrast speckle patterns

    NARCIS (Netherlands)

    Resink, S.G.; Steenbergen, W.

    2015-01-01

    Recently we presented acousto-optic (AO) probing of scattering media using addition or subtraction of speckle patterns due to tandem nanosecond pulses. Here we present a theoretical framework for ideal (polarized, noise-free) speckle patterns with unity contrast that links ultrasound-induced optical

  13. Evaluation of fast highly undersampled contrast-enhanced MR angiography (sparse CE-MRA) in intracranial applications - initial study.

    Science.gov (United States)

    Gratz, Marcel; Schlamann, Marc; Goericke, Sophia; Maderwald, Stefan; Quick, Harald H

    2017-03-01

    To assess the image quality of sparsely sampled contrast-enhanced MR angiography (sparse CE-MRA) providing high spatial resolution and whole-head coverage. Twenty-three patients scheduled for contrast-enhanced MR imaging of the head, (N = 19 with intracranial pathologies, N = 9 with vascular diseases), were included. Sparse CE-MRA at 3 Tesla was conducted using a single dose of contrast agent. Two neuroradiologists independently evaluated the data regarding vascular visibility and diagnostic value of overall 24 parameters and vascular segments on a 5-point ordinary scale (5 = very good, 1 = insufficient vascular visibility). Contrast bolus timing and the resulting arterio-venous overlap was also evaluated. Where available (N = 9), sparse CE-MRA was compared to intracranial Time-of-Flight MRA. The overall rating across all patients for sparse CE-MRA was 3.50 ± 1.07. Direct influence of the contrast bolus timing on the resulting image quality was observed. Overall mean vascular visibility and image quality across different features was rated good to intermediate (3.56 ± 0.95). The average performance of intracranial Time-of-Flight was rated 3.84 ± 0.87 across all patients and 3.54 ± 0.62 across all features. Sparse CE-MRA provides high-quality 3D MRA with high spatial resolution and whole-head coverage within short acquisition time. Accurate contrast bolus timing is mandatory. • Sparse CE-MRA enables fast vascular imaging with full brain coverage. • Volumes with sub-millimetre resolution can be acquired within 10 seconds. • Reader's ratings are good to intermediate and dependent on contrast bolus timing. • The method provides an excellent overview and allows screening for vascular pathologies.

  14. High-resolution short-exposure small-animal laboratory x-ray phase-contrast tomography

    Science.gov (United States)

    Larsson, Daniel H.; Vågberg, William; Yaroshenko, Andre; Yildirim, Ali Önder; Hertz, Hans M.

    2016-12-01

    X-ray computed tomography of small animals and their organs is an essential tool in basic and preclinical biomedical research. In both phase-contrast and absorption tomography high spatial resolution and short exposure times are of key importance. However, the observable spatial resolutions and achievable exposure times are presently limited by system parameters rather than more fundamental constraints like, e.g., dose. Here we demonstrate laboratory tomography with few-ten μm spatial resolution and few-minute exposure time at an acceptable dose for small-animal imaging, both with absorption contrast and phase contrast. The method relies on a magnifying imaging scheme in combination with a high-power small-spot liquid-metal-jet electron-impact source. The tomographic imaging is demonstrated on intact mouse, phantoms and excised lungs, both healthy and with pulmonary emphysema.

  15. Pair-Wise, Deformable Mirror, Image Plane-Based Diversity Electric Field Estimation for High Contrast Coronagraphy

    Science.gov (United States)

    Give'on, Amir; Kern, Brian D.; Shaklan, Stuart

    2011-01-01

    In this paper we describe the complex electric field reconstruction from image plane intensity measurements for high contrast coronagraphic imaging. A deformable mirror (DM) surface is modied with pairs of complementary shapes to create diversity in the image plane of the science camera where the intensity of the light is measured. Along with the Electric Field Conjugation correction algorithm, this estimation method has been used in various high contrast imaging testbeds to achieve the best contrasts to date both in narrow and in broad band light. We present the basic methodology of estimation in easy to follow list of steps, present results from HCIT and raise several open quations we are confronted with using this method.

  16. High-contrast imager for Complex Aperture Telescopes (HiCAT): 2. Design overview and first light results

    CERN Document Server

    N'Diaye, Mamadou; Egron, Sylvain; Pueyo, Laurent; Leboulleux, Lucie; Levecq, Olivier; Perrin, Marshall D; Elliot, Erin; Wallace, J Kent; Hugot, Emmanuel; Marcos, Michel; Ferrari, Marc; Long, Chris A; Anderson, Rachel; DiFelice, Audrey; Soummer, Rémi

    2014-01-01

    We present a new high-contrast imaging testbed designed to provide complete solutions in wavefront sensing, control and starlight suppression with complex aperture telescopes. The testbed was designed to enable a wide range of studies of the effects of such telescope geometries, with primary mirror segmentation, central obstruction, and spiders. The associated diffraction features in the point spread function make high-contrast imaging more challenging. In particular the testbed will be compatible with both AFTA-like and ATLAST-like aperture shapes, respectively on-axis monolithic, and on-axis segmented telescopes. The testbed optical design was developed using a novel approach to define the layout and surface error requirements to minimize amplitude-induced errors at the target contrast level performance. In this communication we compare the as-built surface errors for each optic to their specifications based on end-to-end Fresnel modeling of the testbed. We also report on the testbed optical and optomechani...

  17. Experimental Realisation of High-sensitivity Laboratory X-ray Grating-based Phase-contrast Computed Tomography.

    Science.gov (United States)

    Birnbacher, Lorenz; Willner, Marian; Velroyen, Astrid; Marschner, Mathias; Hipp, Alexander; Meiser, Jan; Koch, Frieder; Schröter, Tobias; Kunka, Danays; Mohr, Jürgen; Pfeiffer, Franz; Herzen, Julia

    2016-04-04

    The possibility to perform high-sensitivity X-ray phase-contrast imaging with laboratory grating-based phase-contrast computed tomography (gbPC-CT) setups is of great interest for a broad range of high-resolution biomedical applications. However, achieving high sensitivity with laboratory gbPC-CT setups still poses a challenge because several factors such as the reduced flux, the polychromaticity of the spectrum, and the limited coherence of the X-ray source reduce the performance of laboratory gbPC-CT in comparison to gbPC-CT at synchrotron facilities. In this work, we present our laboratory X-ray Talbot-Lau interferometry setup operating at 40 kVp and describe how we achieve the high sensitivity yet unrivalled by any other laboratory X-ray phase-contrast technique. We provide the angular sensitivity expressed via the minimum resolvable refraction angle both in theory and experiment, and compare our data with other differential phase-contrast setups. Furthermore, we show that the good stability of our high-sensitivity setup allows for tomographic scans, by which even the electron density can be retrieved quantitatively as has been demonstrated in several preclinical studies.

  18. Reconstruction of High Resolution 3D Objects from Incomplete Images and 3D Information

    Directory of Open Access Journals (Sweden)

    Alexander Pacheco

    2014-05-01

    Full Text Available To this day, digital object reconstruction is a quite complex area that requires many techniques and novel approaches, in which high-resolution 3D objects present one of the biggest challenges. There are mainly two different methods that can be used to reconstruct high resolution objects and images: passive methods and active methods. This methods depend on the type of information available as input for modeling 3D objects. The passive methods use information contained in the images and the active methods make use of controlled light sources, such as lasers. The reconstruction of 3D objects is quite complex and there is no unique solution- The use of specific methodologies for the reconstruction of certain objects it’s also very common, such as human faces, molecular structures, etc. This paper proposes a novel hybrid methodology, composed by 10 phases that combine active and passive methods, using images and a laser in order to supplement the missing information and obtain better results in the 3D object reconstruction. Finally, the proposed methodology proved its efficiency in two complex topological complex objects.

  19. Optimum segmentation of simple objects in high-resolution remote sensing imagery in coastal areas

    Institute of Scientific and Technical Information of China (English)

    CHEN Jianyu; PAN Delu; MAO Zhihua

    2006-01-01

    The optimum segmentation of ground objects in a landscape is essential for interpretation of high-resolution remotely sensed imagery and detection of objects; and it is also a technical foundation to efficiently use spatial information in remote sensing imagery. Landscapes are complex system composed of a large number of heterogeneous components. There are many explicit homogeneous image objects that have similar spectral character and yet differ from surrounding objects in high-resolution remote sensing imagery. Thereby, a new concept of Distinctive Feature of fractal is put forward and used in deriving Distinctive Feature curve of fractal evolution in multiscale segmentation.Through distinguishing the extremum condition of Distinctive Feature curve and the inclusion relationship of fractals in multiscale representation the Scalar Order is built. This can help to determinate the optimum scale in image segmentation for simple-objects, and the potential meaningful image-object fitting the intrinsic scale of the dominant landscape object can be obtained. Based on the application in high-resolution remote sensing imagery in coastal areas, a satisfactory result was acquired.

  20. Stochastic parallel gradient descent based adaptive optics used for high contrast imaging coronagraph

    CERN Document Server

    Dong, Bing; Zhang, Xi

    2011-01-01

    An adaptive optics (AO) system based on stochastic parallel gradient descent (SPGD) algorithm is proposed to reduce the speckle noises in the optical system of stellar coronagraph in order to further improve the contrast. The principle of SPGD algorithm is described briefly and a metric suitable for point source imaging optimization is given. The feasibility and good performance of SPGD algorithm is demonstrated by experimental system featured with a 140-actuators deformable mirror (DM) and a Hartmann- Shark wavefront sensor. Then the SPGD based AO is applied to a liquid crystal array (LCA) based coronagraph. The LCA can modulate the incoming light to generate a pupil apodization mask in any pattern. A circular stepped pattern is used in our preliminary experiment and the image contrast shows improvement from 10^-3 to 10^-4.5 at angular distance of 2{\\lambda}/D after corrected by SPGD based AO.

  1. Artificial incoherent speckles enable precision astrometry and photometry in high-contrast imaging

    CERN Document Server

    Jovanovic, Nemanja; Martinache, Frantz; Pathak, Prashant; Hagelberg, Janis; Kudo, Tomoyuki

    2015-01-01

    State-of-the-art coronagraphs employed on extreme adaptive optics enabled instruments, are constantly improving the contrast detection limit for companions at ever closer separations to the host star. In order to constrain their properties and ultimately compositions, it is important to precisely determine orbital parameters and contrasts with respect to the stars they orbit. This can be difficult in the post coronagraphic image plane, as by definition the central star has been occulted by the coronagraph. We demonstrate the flexibility of utilizing the deformable mirror in the adaptive optics system in SCExAO to generate a field of speckles for the purposes of calibration. Speckles can be placed up to $22.5~\\lambda/D$ from the star, with any position angle, brightness and abundance required. Most importantly, we show that a fast modulation of the added speckle phase, between $0$ and $\\pi$, during a long science integration renders these speckles effectively incoherent with the underlying halo. We quantitativ...

  2. Topology Optimization Using Multiscale Finite Element Method for High-Contrast Media

    DEFF Research Database (Denmark)

    Lazarov, Boyan Stefanov

    2014-01-01

    The focus of this paper is on the applicability of multiscale finite element coarse spaces for reducing the computational burden in topology optimization. The coarse spaces are obtained by solving a set of local eigenvalue problems on overlapping patches covering the computational domain....... The approach is relatively easy for parallelization, due to the complete independence of the subproblems, and ensures contrast independent convergence of the iterative state problem solvers. Several modifications for reducing the computational cost in connection to topology optimization are discussed...

  3. The High Energy Solar Physics mission (HESP): Scientific objectives and technical description

    Science.gov (United States)

    Crannell, Carol; Dennis, Brian; Davis, John; Emslie, Gordon; Haerendel, Gerhard; Hudson, High; Hurford, Gordon; Lin, Robert; Ling, James; Pick, Monique

    1991-01-01

    The High Energy Solar Physics mission offers the opportunity for major breakthroughs in the understanding of the fundamental energy release and particle acceleration processes at the core of the solar flare problem. The following subject areas are covered: the scientific objectives of HESP; what we can expect from the HESP observations; the high energy imaging spectrometer (HEISPEC); the HESP spacecraft; and budget and schedule.

  4. Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

    NARCIS (Netherlands)

    De Hoop, A.T.; Jiang, L.

    2009-01-01

    The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwell's equations numerically to b

  5. High contrast imaging with an arbitrary aperture: active correction of aperture discontinuities: fundamental limits and practical trade- offs

    Science.gov (United States)

    Pueyo, Laurent; Norman, Colin; Soummer, Rémi; Perrin, Marshall; N'Diaye, Mamadou; Choquet, Élodie; Hoffmann, Jordan; Carlotti, Alexis; Mawet, Dimitri

    2014-08-01

    We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and / or segment gaps. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for future Extremely Large Telescopes, even when the pupil features a "missing segment" . Because the converging non-linear mappings resulting from our Deformable Mirror shapes damps near-field diffraction artifacts in the vicinity of the discontinuities this solution is particularly appealing in terms of spectral bandwidth. We present preliminary results that illustrate the performances of ACAD in the presence of diffraction for apertures for with secondary support structures of varying width and argue that the ultimate contrast achieved can by combining ACAD with modern wavefront control algorithms.

  6. Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph

    CERN Document Server

    Lovis, C; Mouillet, D; Pepe, F; Wildi, F; Astudillo-Defru, N; Beuzit, J -L; Bonfils, X; Cheetham, A; Conod, U; Delfosse, X; Ehrenreich, D; Figueira, P; Forveille, T; Martins, J H C; Quanz, S; Santos, N C; Schmid, H -M; Ségransan, D; Udry, S

    2016-01-01

    Context. The temperate Earth-mass planet Proxima b is the closest exoplanet to Earth and represents what may be our best ever opportunity to search for life outside the Solar System. Aims. We aim at directly detecting Proxima b and characterizing its atmosphere by spatially resolving the planet and obtaining high-resolution reflected-light spectra. Methods. We propose to develop a coupling interface between the SPHERE high-contrast imager and the new ESPRESSO spectrograph, both installed at ESO VLT. The angular separation of 37 mas between Proxima b and its host star requires the use of visible wavelengths to spatially resolve the planet on a 8.2-m telescope. At an estimated planet-to-star contrast of ~10^-7 in reflected light, Proxima b is extremely challenging to detect with SPHERE alone. The use of the high-contrast/high-resolution technique can overcome present limitations by combining a ~10^3-10^4 contrast enhancement from SPHERE to a ~10^4 gain from ESPRESSO. Results. We find that significant but realis...

  7. 80-nm-tunable high-index-contrast subwavelength grating long-wavelength VCSEL: Proposal and numerical simulations

    DEFF Research Database (Denmark)

    Chung, Il-Sug; Mørk, Jesper; Sirbu, Alexei;

    2010-01-01

    A widely-tunable single-mode long wavelength vertical-cavity surface-emitting laser structure employing a MEMStunable high-index-contrast subwavelength grating (HCG) is suggested and numerically investigated. A very large 80- nm linear tuning range was obtained as the HCG was actuated by -220...

  8. Plant tissues in 3D via X-ray tomography: simple contrasting methods allow high resolution imaging.

    Directory of Open Access Journals (Sweden)

    Yannick M Staedler

    Full Text Available Computed tomography remains strongly underused in plant sciences despite its high potential in delivering detailed 3D phenotypical information because of the low X-ray absorption of most plant tissues. Existing protocols to study soft tissues display poor performance, especially when compared to those used on animals. More efficient protocols to study plant material are therefore needed. Flowers of Arabidopsis thaliana and Marcgravia caudata were immersed in a selection of contrasting agents used to treat samples for transmission electron microscopy. Grayscale values for floral tissues and background were measured as a function of time. Contrast was quantified via a contrast index. The thick buds of Marcgravia were scanned to determine which contrasting agents best penetrate thick tissues. The highest contrast increase with cytoplasm-rich tissues was obtained with phosphotungstate, whereas osmium tetroxide and bismuth tatrate displayed the highest contrast increase with vacuolated tissues. Phosphotungstate also displayed the best sample penetration. Furthermore, infiltration with phosphotungstate allowed imaging of all plants parts at a high resolution of 3 µm, which approaches the maximum resolution of our equipment: 1.5 µm. The high affinity of phosphotungstate for vasculature, cytoplasm-rich tissue, and pollen causes these tissues to absorb more X-rays than the surrounding tissues, which, in turn, makes these tissues appear brighter on the scan data. Tissues with different brightness can then be virtually dissected from each other by selecting the bracket of grayscale to be visualized. Promising directions for the future include in silico phenotyping and developmental studies of plant inner parts (e.g., ovules, vasculature, pollen, and cell nuclei via virtual dissection as well as correlations of quantitative phenotypes with omics datasets. Therefore, this work represents a crucial improvement of previous methods, allowing new directions of

  9. Plant tissues in 3D via X-ray tomography: simple contrasting methods allow high resolution imaging.

    Science.gov (United States)

    Staedler, Yannick M; Masson, David; Schönenberger, Jürg

    2013-01-01

    Computed tomography remains strongly underused in plant sciences despite its high potential in delivering detailed 3D phenotypical information because of the low X-ray absorption of most plant tissues. Existing protocols to study soft tissues display poor performance, especially when compared to those used on animals. More efficient protocols to study plant material are therefore needed. Flowers of Arabidopsis thaliana and Marcgravia caudata were immersed in a selection of contrasting agents used to treat samples for transmission electron microscopy. Grayscale values for floral tissues and background were measured as a function of time. Contrast was quantified via a contrast index. The thick buds of Marcgravia were scanned to determine which contrasting agents best penetrate thick tissues. The highest contrast increase with cytoplasm-rich tissues was obtained with phosphotungstate, whereas osmium tetroxide and bismuth tatrate displayed the highest contrast increase with vacuolated tissues. Phosphotungstate also displayed the best sample penetration. Furthermore, infiltration with phosphotungstate allowed imaging of all plants parts at a high resolution of 3 µm, which approaches the maximum resolution of our equipment: 1.5 µm. The high affinity of phosphotungstate for vasculature, cytoplasm-rich tissue, and pollen causes these tissues to absorb more X-rays than the surrounding tissues, which, in turn, makes these tissues appear brighter on the scan data. Tissues with different brightness can then be virtually dissected from each other by selecting the bracket of grayscale to be visualized. Promising directions for the future include in silico phenotyping and developmental studies of plant inner parts (e.g., ovules, vasculature, pollen, and cell nuclei) via virtual dissection as well as correlations of quantitative phenotypes with omics datasets. Therefore, this work represents a crucial improvement of previous methods, allowing new directions of research to be

  10. A systematic comparison of different object-based classification techniques using high spatial resolution imagery in agricultural environments

    Science.gov (United States)

    Li, Manchun; Ma, Lei; Blaschke, Thomas; Cheng, Liang; Tiede, Dirk

    2016-07-01

    Geographic Object-Based Image Analysis (GEOBIA) is becoming more prevalent in remote sensing classification, especially for high-resolution imagery. Many supervised classification approaches are applied to objects rather than pixels, and several studies have been conducted to evaluate the performance of such supervised classification techniques in GEOBIA. However, these studies did not systematically investigate all relevant factors affecting the classification (segmentation scale, training set size, feature selection and mixed objects). In this study, statistical methods and visual inspection were used to compare these factors systematically in two agricultural case studies in China. The results indicate that Random Forest (RF) and Support Vector Machines (SVM) are highly suitable for GEOBIA classifications in agricultural areas and confirm the expected general tendency, namely that the overall accuracies decline with increasing segmentation scale. All other investigated methods except for RF and SVM are more prone to obtain a lower accuracy due to the broken objects at fine scales. In contrast to some previous studies, the RF classifiers yielded the best results and the k-nearest neighbor classifier were the worst results, in most cases. Likewise, the RF and Decision Tree classifiers are the most robust with or without feature selection. The results of training sample analyses indicated that the RF and adaboost. M1 possess a superior generalization capability, except when dealing with small training sample sizes. Furthermore, the classification accuracies were directly related to the homogeneity/heterogeneity of the segmented objects for all classifiers. Finally, it was suggested that RF should be considered in most cases for agricultural mapping.

  11. High-contrast subcutaneous vein detection and localization using multispectral imaging

    Science.gov (United States)

    Wang, Fengtao; Behrooz, Ali; Morris, Michael; Adibi, Ali

    2013-05-01

    Multispectral imaging has shown promise in subcutaneous vein detection and localization in human subjects. While many limitations of single-wavelength methods are addressed in multispectral vein detection methods, their performance is still limited by artifacts arising from background skin reflectance and optimality of postprocessing algorithms. We propose a background removal technique that enhances the contrast and performance of multispectral vein detection. We use images acquired at visible wavelengths as reference for removing skin reflectance background from subcutaneous structures in near-infrared images. Results are validated by experiments on human subjects.

  12. Production of Structural Colors with High Contrast and Wide Viewing Angles from Assemblies of Polypyrrole Black Coated Polystyrene Nanoparticles.

    Science.gov (United States)

    Yang, Xiaoming; Ge, Dengteng; Wu, Gaoxiang; Liao, Zhiwei; Yang, Shu

    2016-06-29

    Structural color with wide viewing angles has enormous potential applications in pigment, ink formulation, displays, and sensors. However, colors obtained from colloidal assemblies with low refractive index contrast or without black additives typically appear pale. Here, we prepare polypyrrole (PPy) black coated polystyrene (PS) nanoparticles and demonstrate well-defined colors with high color contrast and wide viewing angles under ambient light. Depending on the loading of pyrrole during polymerization, PPy nanogranules of different sizes and coverages are grafted to the surface of PS nanoparticles. The bumpy particles can self-assemble into quasi-amorphous arrays, resulting in low angle dependent structure colors under ambient light. The color can be tuned by the size of the PS nanoparticles, and the presence of the PPy black on PS nanoparticles enhances the color contrast by suppressing incoherent and multiple scattering.

  13. Object-Based Forest Cover Monitoring Using GAOFEN-2 High Resolution Satellite Images

    Science.gov (United States)

    Li, S. M.; Li, Z. Y.; Chen, E. X.; Liu, Q. W.

    2016-10-01

    Forest cover monitoring is an important part of forest management in local or regional area. The structure and tones of forest can be identified in high spatial remote sensing images. When forests cover change, the spectral characteristics of forests is also changed. In this paper a method on object-based forest cover monitoring with data transformation from time series of high resolution images is put forward. First the NDVI difference image and the composite of PC3,PC4, PC5 of the stacked 8 layers of time series of high resolution satellites are segmented into homogeneous objects. With development of the object-based ruleset classification system, the spatial extent of deforestation and afforestation can be identified over time across the landscape. Finally the change accuracy is achieved with reference data.

  14. Highly stable polymer coated nano-clustered silver plates: a multimodal optical contrast agent for biomedical imaging.

    Science.gov (United States)

    Ray, Aniruddha; Mukundan, Ananya; Xie, Zhixing; Karamchand, Leshern; Wang, Xueding; Kopelman, Raoul

    2014-11-07

    Here, we present a new optical contrast agent based on silver nanoplate clusters embedded inside of a polymer nano matrix. Unlike nanosphere clusters, which have been well studied, nanoplate clusters have unique properties due to the different possible orientations of interaction between the individual plates, resulting in a significant broadening of the absorption spectra. These nanoclusters were immobilized inside of a polymer cladding so as to maintain their stability and optical properties under in vivo conditions. The polymer-coated silver nanoplate clusters show a lower toxicity compared to the uncoated nanoparticles. At high nanoparticle concentrations, cell death occurs mostly due to apoptosis. These nanoparticles were used for targeted fluorescence imaging in a rat glioma cell line by incorporating a fluorescent dye into the matrix, followed by conjugation of a tumor targeting an F3 peptide. We further used these nanoparticles as photoacoustic contrast agents in vivo to enhance the contrast of the vasculature structures in a rat ear model. We observed a contrast enhancement of over 90% following the nanoparticle injection. It is also shown that these NPs can serve as efficient contrast agents, with specific targeting abilities for broadband multimodal imaging that are usable for diagnostic applications and that extend into use as therapeutic agents as well.

  15. Highly stable polymer coated nano-clustered silver plates: a multimodal optical contrast agent for biomedical imaging

    Science.gov (United States)

    Ray, Aniruddha; Mukundan, Ananya; Xie, Zhixing; Karamchand, Leshern; Wang, Xueding; Kopelman, Raoul

    2014-11-01

    Here, we present a new optical contrast agent based on silver nanoplate clusters embedded inside of a polymer nano matrix. Unlike nanosphere clusters, which have been well studied, nanoplate clusters have unique properties due to the different possible orientations of interaction between the individual plates, resulting in a significant broadening of the absorption spectra. These nanoclusters were immobilized inside of a polymer cladding so as to maintain their stability and optical properties under in vivo conditions. The polymer-coated silver nanoplate clusters show a lower toxicity compared to the uncoated nanoparticles. At high nanoparticle concentrations, cell death occurs mostly due to apoptosis. These nanoparticles were used for targeted fluorescence imaging in a rat glioma cell line by incorporating a fluorescent dye into the matrix, followed by conjugation of a tumor targeting an F3 peptide. We further used these nanoparticles as photoacoustic contrast agents in vivo to enhance the contrast of the vasculature structures in a rat ear model. We observed a contrast enhancement of over 90% following the nanoparticle injection. It is also shown that these NPs can serve as efficient contrast agents, with specific targeting abilities for broadband multimodal imaging that are usable for diagnostic applications and that extend into use as therapeutic agents as well.

  16. Asymmetric-detection time-stretch optical microscopy (ATOM) for ultrafast high-contrast cellular imaging in flow

    CERN Document Server

    Wong, Terence T W; Ho, Kenneth K Y; Tang, Matthew Y H; Robles, Joseph D F; Wei, Xiaoming; Chan, Antony C S; Tang, Anson H L; Lam, Edmund Y; Wong, Kenneth K Y; Chan, Godfrey C F; Shum, Ho Cheung; Tsia, Kevin K

    2013-01-01

    Accelerating imaging speed in optical microscopy is often realized at the expense of image contrast, image resolution, and detection sensitivity- a common predicament for advancing high-speed and high-throughput cellular imaging. We here demonstrate a new imaging approach, called asymmetric-detection time-stretch optical microscopy (ATOM), which can deliver ultrafast label-free high-contrast flow imaging with well delineated cellular morphological resolution and in-line optical image amplification to overcome the compromised imaging sensitivity at high speed. We show that ATOM can separately reveal the enhanced phase-gradient and absorption contrast in microfluidic live-cell imaging at a flow speed as high as ~10 m/s, corresponding to an imaging throughput of ~100,000 cells/sec. ATOM could thus be the enabling platform to meet the pressing need for intercalating optical microscopy in cellular assay, e.g. imaging flow cytometry- permitting high-throughput access to the morphological information of the individu...

  17. Asymmetric-detection time-stretch optical microscopy (ATOM) for ultrafast high-contrast cellular imaging in flow

    Science.gov (United States)

    Wong, Terence T. W.; Lau, Andy K. S.; Ho, Kenneth K. Y.; Tang, Matthew Y. H.; Robles, Joseph D. F.; Wei, Xiaoming; Chan, Antony C. S.; Tang, Anson H. L.; Lam, Edmund Y.; Wong, Kenneth K. Y.; Chan, Godfrey C. F.; Shum, Ho Cheung; Tsia, Kevin K.

    2014-01-01

    Accelerating imaging speed in optical microscopy is often realized at the expense of image contrast, image resolution, and detection sensitivity – a common predicament for advancing high-speed and high-throughput cellular imaging. We here demonstrate a new imaging approach, called asymmetric-detection time-stretch optical microscopy (ATOM), which can deliver ultrafast label-free high-contrast flow imaging with well delineated cellular morphological resolution and in-line optical image amplification to overcome the compromised imaging sensitivity at high speed. We show that ATOM can separately reveal the enhanced phase-gradient and absorption contrast in microfluidic live-cell imaging at a flow speed as high as ~10 m/s, corresponding to an imaging throughput of ~100,000 cells/sec. ATOM could thus be the enabling platform to meet the pressing need for intercalating optical microscopy in cellular assay, e.g. imaging flow cytometry – permitting high-throughput access to the morphological information of the individual cells simultaneously with a multitude of parameters obtained in the standard assay. PMID:24413677

  18. High contrast optical imaging methods for image guided laser ablation of dental caries lesions

    Science.gov (United States)

    LaMantia, Nicole R.; Tom, Henry; Chan, Kenneth H.; Simon, Jacob C.; Darling, Cynthia L.; Fried, Daniel

    2014-02-01

    Laser based methods are well suited for automation and can be used to selectively remove dental caries to minimize the loss of healthy tissues and render the underlying enamel more resistant to acid dissolution. The purpose of this study was to determine which imaging methods are best suited for image-guided ablation of natural non-cavitated carious lesions on occlusal surfaces. Multiple caries imaging methods were compared including near-IR and visible reflectance and quantitative light fluorescence (QLF). In order for image-guided laser ablation to be feasible, chemical and physical modification of tooth surfaces due to laser irradiation cannot greatly reduce the contrast between sound and demineralized dental hard tissues. Sound and demineralized surfaces of 48 extracted human molar teeth with non-cavitated lesions were examined. Images were acquired before and after laser irradiation using visible and near-IR reflectance and QLF at several wavelengths. Polarization sensitive-optical coherence tomography was used to confirm that lesions were present. The highest contrast was attained at 1460-nm and 1500-1700-nm, wavelengths coincident with higher water absorption. The reflectance did not decrease significantly after laser irradiation for those wavelengths.

  19. Patients at high risk of adverse events from intravenous contrast media after computed tomography examination

    Energy Technology Data Exchange (ETDEWEB)

    Reddan, Donal [University College Galway Hospitals, Unit 7, Merlin Park Hospital, Galway (Ireland)]. E-mail: donal.reddan@mailn.hse.ie

    2007-05-15

    Adverse reactions to iodinated contrast media (CM) may occur and require prompt recognition and treatment. Although adverse reactions to radiocontrast agents cannot be eliminated, an important first step toward reducing their incidence is to identify patients at greatest risk. Prior to examinations using CM, patients should be adequately assessed by obtaining thorough medical histories and using simple screening tests. Studies have demonstrated that patients with a history of asthma, allergy, hyperthyroidism, and previous reaction to CM are at risk for severe reactions to iodinated CM. Renal adverse reactions reportedly occur more frequently in patients with pre-existing chronic kidney disease, especially those with diabetic nephropathy. Patients with congestive heart failure, dehydration, older age, and those who use nephrotoxic medications are also at risk for developing contrast-associated nephropathy. The occurrence of adverse events may be further increased in patients with multiple risk factors. As the number of patients undergoing computed tomography procedures continues to increase, it is essential for physicians to be able to identify patients at risk for adverse events of CM. Patient-related risk factors are discussed and simple tools for risk stratification presented.

  20. Techniques for High Contrast Imaging in Multi-Star Systems I: Super-Nyquist Wavefront Control

    CERN Document Server

    Thomas, Sandrine J; Bendek, Eduardo

    2015-01-01

    Extra-solar planets direct imaging is now a reality with the deployment and commissioning of the first generation of specialized ground-based instruments (GPI, SPHERE, P1640 and SCExAO). These systems allow of planets $ 10 ^ 7 $ times fainter than their host star. For space-based missions (EXCEDE, EXO-C, EXO-S, WFIRST), various teams have demonstrated laboratory contrasts reaching $ 10 ^ { -10 } $ within a few diffraction limits from the star. However, all of these current and future systems are designed to detect faint planets around a single host star or unresolved multiples, while most non M-dwarf stars such as Alpha Centauri belong to multi-star systems. Direct imaging around binaries/multiple systems at a level of contrast allowing Earth-like planet detection is challenging because the region of interest is contaminated by the hosts star companion as well as the host Generally, the light leakage is caused by both diffraction and aberrations in the system. Moreover, the region of interest usually falls ou...

  1. {sup 18}F-FDG PET/contrast enhanced CT in the standard surveillance of high risk colorectal cancer patients

    Energy Technology Data Exchange (ETDEWEB)

    Jiménez Londoño, Germán Andrés, E-mail: gjimenez91@yahoo.com [Department of Nuclear Medicine, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); García Vicente, Ana María [Department of Nuclear Medicine, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); Sánchez Pérez, Victoria [Department of Oncology, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); Jiménez Aragón, Fátima [Department of Radiology, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); León Martin, Alberto [Investigation Unit, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); Cano Cano, Juana María [Department of Oncology, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); Domínguez Ferreras, Esther [Department of Radiology, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); Gómez López, Ober Van [Department of Nuclear Medicine, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); Espinosa Arranz, Javier [Department of Oncology, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain); Soriano Castrejón, Ángel María [Department of Nuclear Medicine, Hospital General Universitario de Ciudad Real, Ciudad Real (Spain)

    2014-12-15

    Highlights: • We assessed the accuracy of FDG-PET/contrast enhanced CT (FDG-PET/ceCT) in the detection of unsuspected recurrence of colorectal cancer. In regard to our knowledge, no previous experience has been reported about the combined acquisition and interpretation of a FDG-PET/ceCT in the surveillance of colorectal cancer. • We designed a prospective study and performed an individual and combined assessment of both techniques (PET and ceCT), in a patient-based analysis and a lesion-based analysis. • The value of PET and ceCT was found to be similar in the detection of unsuspected recurrence of CRC in a patient-based analysis. The most interesting of our result, is that the combined assessment of PET/ceCT improves the accuracy in the lesion-based analysis. - Abstract: Objective: To assess the accuracy of FDG-PET/contrast enhanced CT (FDG-PET/ceCT) in the detection of unsuspected recurrence of colorectal cancer (CRC) in patients with high risk of relapse. Methods: Thirty-three patients (14 females and 19 males, mean age: 62, range: 41–78), with CRC in complete remission, were prospectively included. All patients underwent FDG-PET/ceCT (58 studies). FDG-PET/ceCT was requested in the surveillance setting, and performed following a standardized protocol. A portal venous phase CT scan was performed after the injection of iodinated contrast agent. An individual and combined assessment of both techniques (PET and ceCT) was performed. Concordant and discordant findings of PET, ceCT and FDG-PET/ceCT were compared in a patient-based and a lesion-based analysis. The final diagnosis, recurrence or disease free status (DFS), were established by histopathology or clinical/radiological follow-up of at least 6 months. Results: Seven out of 33 patients had a confirmed recurrence and the rest of patients had a DFS. In a patient-based analysis the sensitivity and specificity of PET, ceCT and PET/ceCT was of 86% and 88%, 86% and 92%, 86% and 85%, respectively. Attending to

  2. High-contrast X-ray micro-tomography of low attenuation samples using large area hybrid semiconductor pixel detector array of 10 × 5 Timepix chips

    Science.gov (United States)

    Karch, J.; Krejci, F.; Bartl, B.; Dudak, J.; Kuba, J.; Kvacek, J.; Zemlicka, J.

    2016-01-01

    State-of-the-art hybrid pixel semiconductor detectors provide excellent imaging properties such as unlimited dynamic range, high spatial resolution, high frame rate and energy sensitivity. Nevertheless, a limitation in the use of these devices for imaging has been the small sensitive area of a few square centimetres. In the field of microtomography we make use of a large area pixel detector assembled from 50 Timepix edgeless chips providing fully sensitive area of 14.3 × 7.15 cm2. We have successfully demonstrated that the enlargement of the sensitive area enables high-quality tomographic measurements of whole objects with high geometrical magnification without any significant degradation in resulting reconstructions related to the chip tilling and edgeless sensor technology properties. The technique of micro-tomography with the newly developed large area detector is applied for samples formed by low attenuation, low contrast materials such a seed from Phacelia tanacetifolia, a charcoalified wood sample and a beeswax seal sample.

  3. High-sensitivity and cost-effective system for infrared imaging of concealed objects in dynamic mode

    Science.gov (United States)

    Gordiyenko, E.; Yefremenko, V.; Pearson, J.; Bader, S. D.; Novosad, V.

    2005-05-01

    Novel, cost-efficient, and highly-sensitive IR imaging systems play an important role in homeland security functions. Technical limitations in the areas of sensitivity, contrast ratio, bandwidth and cost continue to constrain imaging capabilities. We have designed and prototyped a compact computer-piloted high sensitivity infrared imaging system. The device consists of infrared optics, cryostat, low-noise pre-amplifier, Analog-to-Digital hardware, feedback electronics, and unique image processing software. Important advantages of the developed system are: (i) Eight electronic channels are available for simultaneous registration of IR and visible images in multiple spectral ranges, (ii) Capability of real-time analysis such as comparing the "sensed" image with "reference" images from a database, (iii) High accuracy temperature measurement of multiple points on the image by referencing the radiation intensity from the object to a black body model, (iv) Image generation by real-time integration of images from multiple sensors operating from the visible to the terahertz range. The device was tested with a liquid-nitrogen-cooled, single-pixel HgCdTe detector for imaging in 8-12 microns range. The demonstrated examples of infrared imaging of concealed objects in static and dynamic modes include a hammer (metal head and wooden handle), plastic imitator of handguns hidden under clothes, powder in an envelope, and revealing complex wall structures under decorative plaster.

  4. High-resolution blood-pool-contrast-enhanced MR angiography in glioblastoma: tumor-associated neovascularization as a biomarker for patient survival. A preliminary study

    Energy Technology Data Exchange (ETDEWEB)

    Puig, Josep; Blasco, Gerard; Remollo, Sebastian; Hernandez, David; Pedraza, Salvador [Hospital Universitari Dr Josep Trueta, Research Unit of Diagnostic Imaging Institute (IDI), Department of Radiology [Girona Biomedical Research Institute] IDIBGI, Girona (Spain); Daunis-i-Estadella, Josep; Mateu, Gloria [University of Girona, Department of Computer Science, Applied Mathematics and Statistics, Girona (Spain); Alberich-Bayarri, Angel [La Fe Polytechnics and University Hospital, Biomedical Imaging Research Group (GIBI230), La Fe Health Research Institute, Valencia (Spain); Essig, Marco [University of Manitoba, Department of Radiology, Winnipeg (Canada); Jain, Rajan [NYU School of Medicine, Division of Neuroradiology, Department of Radiology, New York, NY (United States); Puigdemont, Montserrat [Hospital Universitari Dr Josep Trueta, Catalan Institute of Oncology (ICO), Hospital Cancer Registry, Girona (Spain); Sanchez-Gonzalez, Javier [Philips Healthcare Iberica, Madrid (Spain); Wintermark, Max [Stanford University, Department of Radiology, Neuroradiology Division, Palo Alto, CA (United States)

    2016-01-15

    The objective of the study was to determine whether tumor-associated neovascularization on high-resolution gadofosveset-enhanced magnetic resonance angiography (MRA) is a useful biomarker for predicting survival in patients with newly diagnosed glioblastomas. Before treatment, 35 patients (25 men; mean age, 64 ± 14 years) with glioblastoma underwent MRI including first-pass dynamic susceptibility contrast (DSC) perfusion and post-contrast T1WI sequences with gadobutrol (0.1 mmol/kg) and, 48 h later, high-resolution MRA with gadofosveset (0.03 mmol/kg). Volumes of interest for contrast-enhancing lesion (CEL), non-CEL, and contralateral normal-appearing white matter were obtained, and DSC perfusion and DWI parameters were evaluated. Prognostic factors were assessed by Kaplan-Meier survival and Cox proportional hazards model. Eighteen (51.42 %) glioblastomas were hypervascular on high-resolution MRA. Hypervascular glioblastomas were associated with higher CEL volume and lower Karnofsky score. Median survival rates for patients with hypovascular and hypervascular glioblastomas treated with surgery, radiotherapy, and chemotherapy were 15 and 9.75 months, respectively (P < 0.001). Tumor-associated neovascularization was the best predictor of survival at 5.25 months (AUC = 0.794, 81.2 % sensitivity, 77.8 % specificity, 76.5 % positive predictive value, 82.4 % negative predictive value) and yielded the highest hazard ratio (P < 0.001). Tumor-associated neovascularization detected on high-resolution blood-pool-contrast-enhanced MRA of newly diagnosed glioblastoma seems to be a useful biomarker that correlates with worse survival. (orig.)

  5. Object crowding.

    Science.gov (United States)

    Wallace, Julian M; Tjan, Bosco S

    2011-05-25

    Crowding occurs when stimuli in the peripheral fields become harder to identify when flanked by other items. This phenomenon has been demonstrated extensively with simple patterns (e.g., Gabors and letters). Here, we characterize crowding for everyday objects. We presented three-item arrays of objects and letters, arranged radially and tangentially in the lower visual field. Observers identified the central target, and we measured contrast energy thresholds as a function of target-to-flanker spacing. Object crowding was similar to letter crowding in spatial extent but was much weaker. The average elevation in threshold contrast energy was in the order of 1 log unit for objects as compared to 2 log units for letters and silhouette objects. Furthermore, we examined whether the exterior and interior features of an object are differentially affected by crowding. We used a circular aperture to present or exclude the object interior. Critical spacings for these aperture and "donut" objects were similar to those of intact objects. Taken together, these findings suggest that crowding between letters and objects are essentially due to the same mechanism, which affects equally the interior and exterior features of an object. However, for objects defined with varying shades of gray, it is much easier to overcome crowding by increasing contrast.

  6. Contributions of low and high spatial frequency processing to impaired object recognition circuitry in schizophrenia.

    Science.gov (United States)

    Calderone, Daniel J; Hoptman, Matthew J; Martínez, Antígona; Nair-Collins, Sangeeta; Mauro, Cristina J; Bar, Moshe; Javitt, Daniel C; Butler, Pamela D

    2013-08-01

    Patients with schizophrenia exhibit cognitive and sensory impairment, and object recognition deficits have been linked to sensory deficits. The "frame and fill" model of object recognition posits that low spatial frequency (LSF) information rapidly reaches the prefrontal cortex (PFC) and creates a general shape of an object that feeds back to the ventral temporal cortex to assist object recognition. Visual dysfunction findings in schizophrenia suggest a preferential loss of LSF information. This study used functional magnetic resonance imaging (fMRI) and resting state functional connectivity (RSFC) to investigate the contribution of visual deficits to impaired object "framing" circuitry in schizophrenia. Participants were shown object stimuli that were intact or contained only LSF or high spatial frequency (HSF) information. For controls, fMRI revealed preferential activation to LSF information in precuneus, superior temporal, and medial and dorsolateral PFC areas, whereas patients showed a preference for HSF information or no preference. RSFC revealed a lack of connectivity between early visual areas and PFC for patients. These results demonstrate impaired processing of LSF information during object recognition in schizophrenia, with patients instead displaying increased processing of HSF information. This is consistent with findings of a preference for local over global visual information in schizophrenia.

  7. Cascade Boosting-Based Object Detection from High-Level Description to Hardware Implementation

    Directory of Open Access Journals (Sweden)

    Khattab K

    2009-01-01

    Full Text Available Object detection forms the first step of a larger setup for a wide variety of computer vision applications. The focus of this paper is the implementation of a real-time embedded object detection system while relying on high-level description language such as SystemC. Boosting-based object detection algorithms are considered as the fastest accurate object detection algorithms today. However, the implementation of a real time solution for such algorithms is still a challenge. A new parallel implementation, which exploits the parallelism and the pipelining in these algorithms, is proposed. We show that using a SystemC description model paired with a mainstream automatic synthesis tool can lead to an efficient embedded implementation. We also display some of the tradeoffs and considerations, for this implementation to be effective. This implementation proves capable of achieving 42 fps for images as well as bringing regularity in time consuming.

  8. Cloud object store for checkpoints of high performance computing applications using decoupling middleware

    Energy Technology Data Exchange (ETDEWEB)

    Bent, John M.; Faibish, Sorin; Grider, Gary

    2016-04-19

    Cloud object storage is enabled for checkpoints of high performance computing applications using a middleware process. A plurality of files, such as checkpoint files, generated by a plurality of processes in a parallel computing system are stored by obtaining said plurality of files from said parallel computing system; converting said plurality of files to objects using a log structured file system middleware process; and providing said objects for storage in a cloud object storage system. The plurality of processes may run, for example, on a plurality of compute nodes. The log structured file system middleware process may be embodied, for example, as a Parallel Log-Structured File System (PLFS). The log structured file system middleware process optionally executes on a burst buffer node.

  9. Cloud object store for archive storage of high performance computing data using decoupling middleware

    Energy Technology Data Exchange (ETDEWEB)

    Bent, John M.; Faibish, Sorin; Grider, Gary

    2015-06-30

    Cloud object storage is enabled for archived data, such as checkpoints and results, of high performance computing applications using a middleware process. A plurality of archived files, such as checkpoint files and results, generated by a plurality of processes in a parallel computing system are stored by obtaining the plurality of archived files from the parallel computing system; converting the plurality of archived files to objects using a log structured file system middleware process; and providing the objects for storage in a cloud object storage system. The plurality of processes may run, for example, on a plurality of compute nodes. The log structured file system middleware process may be embodied, for example, as a Parallel Log-Structured File System (PLFS). The log structured file system middleware process optionally executes on a burst buffer node.

  10. Cloud object store for archive storage of high performance computing data using decoupling middleware

    Science.gov (United States)

    Bent, John M.; Faibish, Sorin; Grider, Gary

    2015-06-30

    Cloud object storage is enabled for archived data, such as checkpoints and results, of high performance computing applications using a middleware process. A plurality of archived files, such as checkpoint files and results, generated by a plurality of processes in a parallel computing system are stored by obtaining the plurality of archived files from the parallel computing system; converting the plurality of archived files to objects using a log structured file system middleware process; and providing the objects for storage in a cloud object storage system. The plurality of processes may run, for example, on a plurality of compute nodes. The log structured file system middleware process may be embodied, for example, as a Parallel Log-Structured File System (PLFS). The log structured file system middleware process optionally executes on a burst buffer node.

  11. Objects cloaking in LWIR region by using a high efficiency infrared pixel

    Directory of Open Access Journals (Sweden)

    Arab

    2016-12-01

    Full Text Available This article, introduces a new pixel which can emit infrared wavelengths from its surface and can be used for the purpose of cloaking objects from thermal cameras. This pixel can simulate the temperatures between 0 and 100ºC emited from an infrared radiation in LWIR (8-12 micrometres region. Nanocomposite material is used in the pixel structure and this has increased its capacities like ZT factor %40-50 better than the commercial material like Bi2Te3. Technical aspects of the pixel such as the emission wavelengths, rate of temperature changing, thermal contrast, ZT factor and so on are discussed in this paper and were determined by using thermography, non-contact thermometry, radiometry, four probe ac method and temperature differential

  12. High resolution 3D MRI of mouse mammary glands with intra-ductal injection of contrast media.

    Science.gov (United States)

    Markiewicz, Erica; Fan, Xiaobing; Mustafi, Devkumar; Zamora, Marta; Roman, Brian B; Jansen, Sanaz A; Macleod, Kay; Conzen, Suzanne D; Karczmar, Gregory S

    2015-01-01

    The purpose of this study was to use high resolution three-dimensional (3D) magnetic resonance imaging (MRI) to study mouse mammary gland ductal architecture based on intra-ductal injection of contrast agents. Female FVB/N mice age 12-20 weeks (n=12), were used in this study. A 34G, 45° tip Hamilton needle with a 25μL Hamilton syringe was inserted into the tip of the nipple. Approximately 20-25μL of a Gadodiamide/Trypan blue/saline solution was injected slowly over one minute into the nipple and duct. To prevent washout of contrast media from ducts due to perfusion, and maximize the conspicuity of ducts on MRI, mice were sacrificed one minute after injection. High resolution 3D T1-weighted images were acquired on a 9.4T Bruker scanner after sacrifice to eliminate motion artifacts and reduce contrast media leakage from ducts. Trypan blue staining was well distributed throughout the ductal tree. MRI showed the mammary gland ductal structure clearly. In spoiled gradient echo T1-weighted images, the signal-to-noise ratio of regions identified as enhancing mammary ducts following contrast injection was significantly higher than that of muscle (pcontrast media (pcontrast agents to measure metabolism or target receptors in normal ducts and ducts with in situ cancers.

  13. Pupil remapping for high contrast astronomy: results from an optical testbed

    CERN Document Server

    Kotani, T; Perrin, G; Robertson, G; Tuthill, P

    2009-01-01

    The direct imaging and characterization of Earth-like planets is among the most sought-after prizes in contemporary astrophysics, however current optical instrumentation delivers insufficient dynamic range to overcome the vast contrast differential between the planet and its host star. New opportunities are offered by coherent single mode fibers, whose technological development has been motivated by the needs of the telecom industry in the near infrared. This paper presents a new vision for an instrument using coherent waveguides to remap the pupil geometry of the telescope. It would (i) inject the full pupil of the telescope into an array of single mode fibers, (ii) rearrange the pupil so fringes can be accurately measured, and (iii) permit image reconstruction so that atmospheric blurring can be totally removed. Here we present a laboratory experiment whose goal was to validate the theoretical concepts underpinning our proposed method. We successfully confirmed that we can retrieve the image of a simulated ...

  14. Dark-field hyperlens for high-contrast sub-wavelength imaging

    DEFF Research Database (Denmark)

    Repän, Taavi; Zhukovsky, Sergei; Lavrinenko, Andrei

    2016-01-01

    By now superresolution imaging using hyperbolic metamaterial (HMM) structures – hyperlenses – has been demonstrated both theoretically and experimentally. The hyperlens operation relies on the fact that HMM allows propagation of waves with very large transverse wavevectors, which would be evanesc......By now superresolution imaging using hyperbolic metamaterial (HMM) structures – hyperlenses – has been demonstrated both theoretically and experimentally. The hyperlens operation relies on the fact that HMM allows propagation of waves with very large transverse wavevectors, which would...... structure exhibits a cut-off for waves with small transverse wavevectors (low-k waves). This allows the structure to filter out the background illumination, which is contained in low-k waves. We numerically demonstrate that our device achieves superresolution imaging while providing the strong contrast...

  15. High contrast ultrasonic imaging of resin-rich regions in graphite/epoxy composites using entropy

    Science.gov (United States)

    Hughes, Michael S.; McCarthy, John E.; Bruillard, Paul. J.; Marsh, Jon N.; Wickline, Samuel A.

    2016-02-01

    This study compares different approaches for imaging a near-surface resin-rich defect in a thin graphite/epoxy plate using backscattered ultrasound. The specimen was created by cutting a circular hole in the second ply; this region filled with excess resin from the graphite/epoxy sheets during the curing process. Backscat-tered waveforms were acquired using a 4 in. focal length, 5MHz center frequency broadband transducer, scanned on a 100 × 100 grid of points that were 0.03 × 0.03 in. apart. The specimen was scanned with the defect side closest to the transducer. Consequently, the reflection from the resin-rich region cannot be gated from the large front-wall echo. At each point in the grid 256 waveforms were averaged together and subsequently used to produce peak-to-peak, Signal Energy (sum of squared digitized waveform values), as well as entropy images of two different types (a Renyi entropy, and a joint entropy). As the figure shows, all of the entropy images exhibit better border delineation and defect contrast than the either the peak-to-peak or Signal Energy. The best results are obtained using the joint entropy of the backscattered waveforms with a reference function. Two different references are examined. The first is a reflection of the insonifying pulse from a stainless steel reflector. The second is an approximate optimum obtained from an iterative parametric search. The joint entropy images produced using this reference exhibit three times the contrast obtained in previous studies.

  16. High numerical aperture microendoscope objective for a fiber confocal reflectance microscope

    Science.gov (United States)

    Kester, Robert T.; Tkaczyk, Tomasz S.; Descour, Michael R.; Christenson, Todd; Richards-Kortum, Rebecca

    2007-03-01

    A disposable high numerical aperture microendoscope objective has been designed, fabricated, and tested for use with a fiber confocal reflectance microscope. The objective uses high precision LIGA fabricated components to integrate imaging components and hydraulic suction lines into a housing that measures only 3.85 mm in outer diameter and 14.65 mm in length. The hydraulics are used to translate tissue through the focal plane for three dimensional imaging. This device is diffraction limited for λ = 850 nm, has a numerical aperture of 1.0, a field of view of 250 µm, and a working distance of 450 µm. The objective is intended for in vivo imaging of precancerous cells.

  17. The ISON international campaigns for monitoring of faint high altitude objects

    Science.gov (United States)

    Molotov, Igor; Agapov, Vladimir; Rumyantsev, Vasiliy; Biryukov, Vadim; Schildknecht, Thomas; Bakhtigaraev, Nail; Ibrahimov, Mansur; Papushev, Pavel; Minikulov, Nasredin; Andrievsky, Sergei

    The research of the space debris fragments at high orbits is one of the main directions of the International Scientific Optical Network (ISON) activities. Therefore the dedicated ISON subsystem for high altitude faint space debris observations is arranged with the aim of detection and continuous tracking of as large number of unknown high altitude faint objects as possible. The subsystem includes the number of large telescopes that are able to detect the objects down to 20m-21m and the middle-size telescopes for the observations of the space objects of 15m-18m. The 1-m ZIMLAT in Zimmerwald, Switzerland, 1.5-m AZT-33IK in Mondy, Siberia, 64-cm AT- 64 in Nauchniy, Crimea, 60-cm RK-600 in Mayaki near Odessa, Ukraine, 60-cm Zeiss-600 in Maidanak, Uzbekistan, 70-cm AZT-8 in Gissar, Tajikistan are regularly participating in ISON observing campaigns in collaboration with 1-m Zeiss-1000 ESA space debris telescope in Teide, Canaries islands. 2.6-m ZTSh in Nauchniy, Crimea, 2-m Zeiss-2000 in Terskol, North Caucasus, 1-m Zeiss-1000 in Simeiz, Crimea, 1-m Zeiss-1000 in Arkhyz, North Caucasus are joining during few nights per month. The 60-cm Zeiss-600 in Arkhyz, 70-cm AZT-8 in Evpatoria, Crimea, 60-cm Zeiss-600 in Tarija, Bolivia, 80-cm RK-800 in Mayaki, 80-cm K-800 in Terskol, 50-cm in Ussuriysk, Far East will be added to the subsystem during 2008. The observing campaigns are coordinates by the Center on space debris data collection, processing and analysis of the KIAM RAS in cooperation with the AIUB space debris team. 353 faint objects are discovered in GEO region surveys during the last 3 years (about 100000 measurements were collected for this time), including objects with high AMR. Results are publishing monthly by KIAM in High Geocentric Orbit Space Debris Circular. We will discuss the most interesting of obtained results. Many of discovered fragments are associated with space debris clouds appeared as a result of known or suspected fragmentations occurred in GEO region

  18. Equilibrium-phase high spatial resolution contrast-enhanced MR angiography at 1.5T in preoperative imaging for perforator flap breast reconstruction.

    Directory of Open Access Journals (Sweden)

    Bas Versluis

    Full Text Available OBJECTIVES: The aim was (i to evaluate the accuracy of equilibrium-phase high spatial resolution (EP contrast-enhanced magnetic resonance angiography (CE-MRA at 1.5T using a blood pool contrast agent for the preoperative evaluation of deep inferior epigastric artery perforator branches (DIEP, and (ii to compare image quality with conventional first-pass CE-MRA. METHODS: Twenty-three consecutive patients were included. All patients underwent preoperative CE-MRA to determine quality and location of DIEP. First-pass imaging after a single bolus injection of 10 mL gadofosveset trisodium was followed by EP imaging. MRA data were compared to intra-operative findings, which served as the reference standard. RESULTS: There was 100% agreement between EP CE-MRA and surgical findings in identifying the single best perforator branch. All EP acquisitions were of diagnostic quality, whereas in 10 patients the quality of the first-pass acquisition was qualified as non-diagnostic. Both signal- and contrast-to-noise ratios were significantly higher for EP imaging in comparison with first-pass acquisitions (p<0.01. CONCLUSIONS: EP CE-MRA of DIEP in the preoperative evaluation of patients undergoing a breast reconstruction procedure is highly accurate in identifying the single best perforator branch at 1.5Tesla (T. Besides accuracy, image quality of EP imaging proved superior to conventional first-pass CE-MRA.

  19. Comparison of native high-resolution 3D and contrast-enhanced MR angiography for assessing the thoracic aorta.

    Science.gov (United States)

    von Knobelsdorff-Brenkenhoff, Florian; Gruettner, Henriette; Trauzeddel, Ralf F; Greiser, Andreas; Schulz-Menger, Jeanette

    2014-06-01

    To omit risks of contrast agent administration, native magnetic resonance angiography (MRA) is desired for assessing the thoracic aorta. The aim was to evaluate a native steady-state free precession (SSFP) three-dimensional (3D) MRA in comparison with contrast-enhanced MRA as the gold standard. Seventy-six prospective patients with known or suspicion of thoracic aortic disease underwent MRA at 1.5 T using (i) native 3D SSFP MRA with ECG and navigator gating and high isotropic spatial resolution (1.3 × 1.3 × 1.3 mm(3)) and (ii) conventional contrast-enhanced ECG-gated gradient-echo 3D MRA (1.3 × 0.8 × 1.8 mm(3)). Datasets were compared at nine aortic levels regarding image quality (score 0-3: 0 = poor, 3 = excellent) and aortic diameters, as well as observer dependency and final diagnosis. Statistical tests included paired t-test, correlation analysis, and Bland-Altman analysis. Native 3D MRA was acquired successfully in 70 of 76 subjects (mean acquisition time 8.6 ± 2.7 min), while irregular breathing excluded 6 of 76 subjects. Aortic diameters agreed close between both methods at all aortic levels (r = 0.99; bias ± SD -0.12 ± 1.2 mm) with low intra- and inter-observer dependency (intraclass correlation coefficient 0.99). Native MRA studies resulted in the same final diagnosis as the contrast-enhanced MRA. The mean image quality score was superior with native compared with contrast-enhanced MRA (2.4 ± 0.6 vs. 1.6 ± 0.5; P contrast-enhanced MRA to assess the thoracic aorta. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.

  20. HIGH-RESOLUTION SPECTROSCOPY OF Ne II EMISSION FROM YOUNG STELLAR OBJECTS

    NARCIS (Netherlands)

    Sacco, G. G.; Flaccomio, E.; Pascucci, I.; Lahuis, F.; Ercolano, B.; Kastner, J. H.; Micela, G.; Stelzer, B.; Sterzik, M.

    2012-01-01

    Constraining the spatial and thermal structure of the gaseous component of circumstellar disks is crucial for understanding star and planet formation. Models predict that the [Ne II] line at 12.81 mu m detected in young stellar objects (YSOs) with Spitzer traces disk gas and its response to high-ene

  1. Mauna Kea Spectrographic Explorer (MSE): a conceptual design for multi-object high resolution spectrograph

    Science.gov (United States)

    Zhang, Kai; Zhu, Yongtian; Hu, Zhongwen

    2016-08-01

    The Maunakea Spectroscopic Explorer (MSE) project will transform the CFHT 3.6m optical telescope into a 10m class dedicated multi-object spectroscopic facility, with an ability to simultaneously measure thousands of objects with a spectral resolution range spanning 2,000 to 40,000. MSE will develop two spectrographic facilities to meet the science requirements. These are respectively, the Low/Medium Resolution spectrographs (LMRS) and High Resolution spectrographs (HRS). Multi-object high resolution spectrographs with total of 1,156 fibers is a big challenge, one that has never been attempted for a 10m class telescope. To date, most spectral survey facilities work in single order low/medium resolution mode, and only a few Wide Field Spectrographs (WFS) provide a cross-dispersion high resolution mode with a limited number of orders. Nanjing Institute of Astronomical Optics and Technology (NIAOT) propose a conceptual design with the use of novel image slicer arrays and single order immersed Volume Phase Holographic (VPH) grating for the MSE multi-object high resolution spectrographs. The conceptual scheme contains six identical fiber-link spectrographs, each of which simultaneously covers three restricted bands (λ/30, λ/30, λ/15) in the optical regime, with spectral resolution of 40,000 in Blue/Visible bands (400nm / 490nm) and 20,000 in Red band (650nm). The details of the design is presented in this paper.

  2. HIGH-RESOLUTION SPECTROSCOPY OF Ne II EMISSION FROM YOUNG STELLAR OBJECTS

    NARCIS (Netherlands)

    Sacco, G. G.; Flaccomio, E.; Pascucci, I.; Lahuis, F.; Ercolano, B.; Kastner, J. H.; Micela, G.; Stelzer, B.; Sterzik, M.

    2012-01-01

    Constraining the spatial and thermal structure of the gaseous component of circumstellar disks is crucial for understanding star and planet formation. Models predict that the [Ne II] line at 12.81 mu m detected in young stellar objects (YSOs) with Spitzer traces disk gas and its response to high-ene

  3. Interqubit coupling mediated by a high-excitation-energy quantum object

    NARCIS (Netherlands)

    Ashhab, S.; Niskanen, A.O.; Harrabi, K.; Nakamura, Y.; Picot, T.; De Groot, P.C.; Harmans, C.J.P.M.; Mooij, J.E.; Nori, F.

    2008-01-01

    We consider a system composed of two qubits and a high excitation energy quantum object used to mediate coupling between the qubits. We treat the entire system quantum mechanically and analyze the properties of the eigenvalues and eigenstates of the total Hamiltonian. After reproducing well known re

  4. Continuously tunable photonic fractional Hilbert transformer using a high-contrast germanium-doped silica-on-silicon microring resonator.

    Science.gov (United States)

    Shahoei, Hiva; Dumais, Patrick; Yao, Jianping

    2014-05-01

    We propose and experimentally demonstrate a continuously tunable fractional Hilbert transformer (FHT) based on a high-contrast germanium-doped silica-on-silicon (SOS) microring resonator (MRR). The propagation loss of a high-contrast germanium-doped SOS waveguide can be very small (0.02 dB/cm) while the lossless bend radius can be less than 1 mm. These characteristics lead to the fabrication of an MRR with a high Q-factor and a large free-spectral range (FSR), which is needed to implement a Hilbert transformer (HT). The SOS MRR is strongly polarization dependent. By changing the polarization direction of the input signal, the phase shift introduced at the center of the resonance spectrum is changed. The tunable phase shift at the resonance wavelength can be used to implement a tunable FHT. A germanium-doped SOS MRR with a high-index contrast of 3.8% is fabricated. The use of the fabricated MRR for the implementation of a tunable FHT with tunable orders at 1, 0.85, 0.95, 1.05, and 1.13 for a Gaussian pulse with the temporal full width at half-maximum of 80 ps is experimentally demonstrated.

  5. Soluble urokinase plasminogen activator receptor is in contrast to high-sensitive C-reactive-protein associated with coronary artery calcifications in healthy middle-aged subjects

    DEFF Research Database (Denmark)

    Sørensen, Mette Hjortdal; Gerke, Oke; Eugen-Olsen, Jesper;

    2014-01-01

    OBJECTIVE: The main objective of this study was to investigate the association between two markers of low-grade inflammation; soluble urokinase plasminogen activator receptor (suPAR) and high-sensitive C-reactive protein (hs-CRP); and coronary artery calcification (CAC) score detected by cardiac...... computed tomography (CT) scan. DESIGN: A cross sectional study of 1126 randomly sampled middle-aged men and women. METHODS: CAC score was measured by a non-contrast cardiac CT scan and total 10-year cardiovascular mortality risk was estimated using the Systematic Coronary Risk Evaluation (SCORE). Plasma...... samples were analysed for suPAR and hs-CRP. The association of suPAR and hs-CRP to CAC was evaluated by logistic regression analyses adjusting for categorised SCORE. The additive effect of suPAR to SCORE was evaluated by comparing area under curve (AUC) and net reclassification improvement (NRI). RESULTS...

  6. Optimized Si/SiO2 high contrast grating mirror design for mid-infrared wavelength range: robustness enhancement

    CERN Document Server

    Chevallier, Christyves; Jacquet, Joel; Fressengeas, Nicolas; 10.1016/j.optlastec.2011.09.010

    2011-01-01

    A high reflectivity and polarization selective high contrast grating mirror has been designed with the use of an automated optimization algorithm. Through a precise study of the tolerance of the different lengths of the structure, the robustness with respect to the fabrication errors has been enhanced to high tolerance values between 5 % and 210 %. This adjustment of the dimensions of the structure leads to a 250 nm large bandwidth mirror well adapted for a VCSEL application at \\lambda = 2.65 $\\mu$m and can easily be scaled for other wavelengths.

  7. A new high-perihelion a ~ 700 AU object in the distant Solar System

    Science.gov (United States)

    Bannister, Michele T.; Chen, Ying-Tung; Jakubik, Marian; Kaib, Nathan A.; Kavelaars, JJ; Shankman, Cory; Benecchi, Susan D.; Fraser, Wesley Cristopher; Schwamb, Megan Elizabeth; Wang, Shiang-Yu; Alexandersen, Mike; Gladman, Brett; Gwyn, Stephen D. J.; Petit, Jean-Marc; Volk, Kathryn

    2016-10-01

    We report the discovery of a trans-Neptunian object (TNO) plausibly diffusing out of the inner Oort Cloud reservoir. This TNO is on an orbit with q ~ 50 AU, a ~ 700 AU, the largest semi-major axis yet detected for an orbit with perihelion q beyond the q ≤ 38 zone of strong influence of Neptune, exceeding the semi-major axes of (90377) Sedna, 2012 VP113 and 2010 GB174. Such objects are rarely observed. Trans-Neptunian objects with these high orbital perihelia have no confirmed formation mechanism in the present planetary architecture of the Solar System. The orbit of this new TNO can be formed by inward diffusion of objects from a Galactic-tide-dominated population with a ~ 1000-2000 AU; the formation mechanism is highly inefficient, and would require on the order of a hundred times more objects in that population than in the a ~ 700 AU population. We also report colour and light curve measurements of the new TNO with Gemini North and Subaru-HSC. The longitude of the ascending node and argument of perihelion of this TNO's orbit have implications for the hypothesis of a ninth planet.

  8. Approximating the volume of unions and intersections of high-dimensional geometric objects

    CERN Document Server

    Bringmann, Karl

    2008-01-01

    We consider the computation of the volume of the union of high-dimensional geometric objects. While showing that this problem is #P-hard already for very simple bodies (i.e., axis-parallel boxes), we give a fast FPRAS for all objects where one can: (1) test whether a given point lies inside the object, (2) sample a point uniformly, (3) calculate the volume of the object in polynomial time. All three oracles can be weak, that is, just approximate. This implies that Klee's measure problem and the hypervolume indicator can be approximated efficiently even though they are #P-hard and hence cannot be solved exactly in time polynomial in the number of dimensions unless P=NP. Our algorithm also allows to approximate efficiently the volume of the union of convex bodies given by weak membership oracles. For the analogous problem of the intersection of high-dimensional geometric objects we prove #P-hardness for boxes and show that there is no multiplicative polynomial-time $2^{d^{1-\\epsilon}}$-approximation for certain...

  9. Transient analysis of electromagnetic wave interactions on high-contrast scatterers using volume electric field integral equation

    KAUST Repository

    Sayed, Sadeed Bin

    2014-07-01

    A marching on-in-time (MOT)-based time domain volume electric field integral equation (TD-VEFIE) solver is proposed for accurate and stable analysis of electromagnetic wave interactions on high-contrast scatterers. The stability is achieved using band-limited but two-sided (non-causal) temporal interpolation functions and an extrapolation scheme to cast the time marching into a causal form. The extrapolation scheme is designed to be highly accurate for oscillating and exponentially decaying fields, hence it accurately captures the physical behavior of the resonant modes that are excited inside the dielectric scatterer. Numerical results demonstrate that the resulting MOT scheme maintains its stability as the number of resonant modes increases with the contrast of the scatterer.

  10. Object-based classification of earthquake damage from high-resolution optical imagery using machine learning

    Science.gov (United States)

    Bialas, James; Oommen, Thomas; Rebbapragada, Umaa; Levin, Eugene

    2016-07-01

    Object-based approaches in the segmentation and classification of remotely sensed images yield more promising results compared to pixel-based approaches. However, the development of an object-based approach presents challenges in terms of algorithm selection and parameter tuning. Subjective methods are often used, but yield less than optimal results. Objective methods are warranted, especially for rapid deployment in time-sensitive applications, such as earthquake damage assessment. Herein, we used a systematic approach in evaluating object-based image segmentation and machine learning algorithms for the classification of earthquake damage in remotely sensed imagery. We tested a variety of algorithms and parameters on post-event aerial imagery for the 2011 earthquake in Christchurch, New Zealand. Results were compared against manually selected test cases representing different classes. In doing so, we can evaluate the effectiveness of the segmentation and classification of different classes and compare different levels of multistep image segmentations. Our classifier is compared against recent pixel-based and object-based classification studies for postevent imagery of earthquake damage. Our results show an improvement against both pixel-based and object-based methods for classifying earthquake damage in high resolution, post-event imagery.

  11. Updating Object for GIS Database Information Using High Resolution Satellite Images: a Case Study Zonguldak

    Science.gov (United States)

    Alkan, M.; Arca, D.; Bayik, Ç.; Marangoz, A. M.

    2011-09-01

    Nowadays Geographic Information Systems (GIS) uses Remote Sensing (RS) data for a lot of applications. One of the application areas is the updating of the GIS database using high resolution imagery. In this context high resolution satellite imagery data is very important for many applications areas today's and future. And also, high resolution satellite imagery data will be used in many applications for different purposes. Information systems needs to high resolution imagery data for updating. Updating is very important component for the any of the GIS systems. One of this area will be updated and kept alive GIS database information. High resolution satellite imagery is used with different data base which serve map information via internet and different aims of information systems applications in future topographic and cartographic information systems will very important in our country in this sense use of the satellite images will be unavoidable. In this study explain to how is acquired to satellite images and how is use this images in information systems for object and roads. Firstly, pan-sharpened two of the IKONOS's images have been produced by fusion of high resolution PAN and MS images using PCI Geomatica v9.1 software package. Automatic object extraction has been made using eCognition v4.0.6. On the other hand, these objects have been manually digitized from high resolution images using ArcGIS v9.3. software package. Application section of in this study, satellite images data will be compared each other and GIS objects and road database. It is also determined which data is useful in Geographic Information Systems. Finally, this article explains that integration of remote sensing technology and GIS applications.

  12. Multilocus sequence analysis of nectar pseudomonads reveals high genetic diversity and contrasting recombination patterns.

    Directory of Open Access Journals (Sweden)

    Sergio Alvarez-Pérez

    Full Text Available The genetic and evolutionary relationships among floral nectar-dwelling Pseudomonas 'sensu stricto' isolates associated to South African and Mediterranean plants were investigated by multilocus sequence analysis (MLSA of four core housekeeping genes (rrs, gyrB, rpoB and rpoD. A total of 35 different sequence types were found for the 38 nectar bacterial isolates characterised. Phylogenetic analyses resulted in the identification of three main clades [nectar groups (NGs 1, 2 and 3] of nectar pseudomonads, which were closely related to five intrageneric groups: Pseudomonas oryzihabitans (NG 1; P. fluorescens, P. lutea and P. syringae (NG 2; and P. rhizosphaerae (NG 3. Linkage disequilibrium analysis pointed to a mostly clonal population structure, even when the analysis was restricted to isolates from the same floristic region or belonging to the same NG. Nevertheless, signatures of recombination were observed for NG 3, which exclusively included isolates retrieved from the floral nectar of insect-pollinated Mediterranean plants. In contrast, the other two NGs comprised both South African and Mediterranean isolates. Analyses relating diversification to floristic region and pollinator type revealed that there has been more unique evolution of the nectar pseudomonads within the Mediterranean region than would be expected by chance. This is the first work analysing the sequence of multiple loci to reveal geno- and ecotypes of nectar bacteria.

  13. High-contrast active cavitation imaging technique based on multiple bubble wavelet transform.

    Science.gov (United States)

    Lu, Shukuan; Xu, Shanshan; Liu, Runna; Hu, Hong; Wan, Mingxi

    2016-08-01

    In this study, a unique method that combines the ultrafast active cavitation imaging technique with multiple bubble wavelet transform (MBWT) for improving cavitation detection contrast was presented. The bubble wavelet was constructed by the modified Keller-Miksis equation that considered the mutual effect among bubbles. A three-dimensional spatial model was applied to simulate the spatial distribution of multiple bubbles. The effects of four parameters on the signal-to-noise ratio (SNR) of cavitation images were evaluated, including the following: initial radii of bubbles, scale factor in the wavelet transform, number of bubbles, and the minimum inter-bubble distance. And the other two spatial models and cavitation bubble size distributions were introduced in the MBWT method. The results suggested that in the free-field experiments, the averaged SNR of images acquired by the MBWT method was improved by 7.16 ± 0.09 dB and 3.14 ± 0.14 dB compared with the values of images acquired by the B-mode and single bubble wavelet transform (SBWT) methods. In addition, in the tissue experiments, the averaged cavitation-to-tissue ratio of cavitation images acquired by the MBWT method was improved by 4.69 ± 0.25 dB and 1.74± 0.29 dB compared with that of images acquired by B-mode and SBWT methods.

  14. High-frequency subharmonic pulsed-wave Doppler and color flow imaging of microbubble contrast agents.

    Science.gov (United States)

    Needles, A; Goertz, D E; Karshafian, R; Cherin, E; Brown, A S; Burns, P N; Foster, F S

    2008-07-01

    A recent study has shown the feasibility of subharmonic (SH) flow imaging at a transmit frequency of 20 MHz. This paper builds on these results by examining the performance of SH flow imaging as a function of transmit pressure. Further, we also investigate the feasibility of SH pulsed-wave Doppler (PWD) imaging. In vitro flow experiments were performed with a 1-mm-diameter wall-less vessel cryogel phantom using the ultrasound contrast agent Definity and an imaging frequency of 20 MHz. The phantom results show that there is an identifiable pressure range where accurate flow velocity and power estimates can be made with SH imaging at 10 MHz (SH10), above which velocity estimates are biased by radiation force effects and unstable bubble behavior, and below which velocity and power estimates are degraded by poor SNR. In vivo validation of SH PWD was performed in an arteriole of a rabbit ear, and blood velocity estimates compared well with fundamental (F20) mode PWD. The ability to suppress tissue signals using SH signals may enable the use of higher frame rates and improve sensitivity to microvascular flow or slow velocities near large vessel walls by reducing or eliminating the need for clutter filters.

  15. Effects of differential wavefront sensor bias drifts on high contrast imaging

    CERN Document Server

    Sadakuni, Naru; Palmer, David W; Poyneer, Lisa A; Max, Claire E; Savransky, Dmitry; Thomas, Sandrine J; Cardwell, Andrew; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; Rantakyrö, Fredrik; Serio, Andrew

    2014-01-01

    The Gemini Planet Imager (GPI) is a new facility, extreme adaptive optics (AO), coronagraphic instrument, currently being integrated onto the 8-meter Gemini South telescope, with the ultimate goal of directly imaging extrasolar planets. To achieve the contrast required for the desired science, it is necessary to quantify and mitigate wavefront error (WFE). A large source of potential static WFE arises from the primary AO wavefront sensor (WFS) detector's use of multiple readout segments with independent signal chains including on-chip preamplifiers and external amplifiers. Temperature changes within GPI's electronics cause drifts in readout segments' bias levels, inducing an RMS WFE of 1.1 nm and 41.9 nm over 4.44 degrees Celsius, for magnitude 4 and 11 stars, respectively. With a goal of $<$2 nm of static WFE, these are significant enough to require remedial action. Simulations imply a requirement to take fresh WFS darks every 2 degrees Celsius of temperature change, for a magnitude 6 star; similarly, for...

  16. A general tool for evaluating high-contrast coronagraphic telescope performance error budgets

    Science.gov (United States)

    Marchen, Luis F.; Shaklan, Stuart B.

    2009-08-01

    This paper describes a general purpose Coronagraph Performance Error Budget (CPEB) tool that we have developed under the NASA Exoplanet Exploration Program. The CPEB automates many of the key steps required to evaluate the scattered starlight contrast in the dark hole of a space-based coronagraph. It operates in 3 steps: first, a CodeV or Zemax prescription is converted into a MACOS optical prescription. Second, a Matlab program calls ray-trace code that generates linear beam-walk and aberration sensitivity matrices for motions of the optical elements and line-ofsight pointing, with and without controlled coarse and fine-steering mirrors. Third, the sensitivity matrices are imported by macros into Excel 2007 where the error budget is created. Once created, the user specifies the quality of each optic from a predefined set of PSDs. The spreadsheet creates a nominal set of thermal and jitter motions and combines them with the sensitivity matrices to generate an error budget for the system. The user can easily modify the motion allocations to perform trade studies.

  17. Tracking Neptune’s Migration History through High-perihelion Resonant Trans-Neptunian Objects

    Science.gov (United States)

    Kaib, Nathan A.; Sheppard, Scott S.

    2016-11-01

    Recently, Sheppard et al. presented the discovery of seven new trans-Neptunian objects with moderate eccentricities, perihelia beyond 40 au, and semimajor axes beyond 50 au. Like the few previously known objects on similar orbits, these objects’ semimajor axes are just beyond the Kuiper Belt edge and clustered around Neptunian mean motion resonances (MMRs). These objects likely obtained their observed orbits while trapped within MMRs, when the Kozai–Lidov mechanism raised their perihelia and weakened Neptune’s dynamical influence. Using numerical simulations that model the production of this population, we find that high-perihelion objects near Neptunian MMRs can constrain the nature and timescale of Neptune’s past orbital migration. In particular, the population near the 3:1 MMR (near 62 au) is especially useful due to its large population and short dynamical evolution timescale. If Neptune finishes migrating within ∼100 Myr or less, we predict that over 90% of high-perihelion objects near the 3:1 MMR will have semimajor axes within 1 au of each other, very near the modern resonance’s center. On the other hand, if Neptune’s migration takes ∼300 Myr, we expect ∼50% of this population to reside in dynamically fossilized orbits over ∼1 au closer to the Sun than the modern resonance. We highlight 2015 KH162 as a likely member of this fossilized 3:1 population. Under any plausible migration scenario, nearly all high-perihelion objects in resonances beyond the 4:1 MMR (near 76 au) reach their orbits well after Neptune stops migrating and compose a recently generated, dynamically active population.

  18. The SPEED Project: SPEEDing up Research and Development towards High-contrast Imaging Instruments for the E-ELT

    Science.gov (United States)

    Martinez, P.; Preis, O.; Gouvret, C.; Dejongue, J.; Daban, J.-B.; Spang, A.; Martinache, F.; Beaulieu, M.; Janin-Potiron, P.; Abe, L.; Fantei-Cujolle, Y.; Ottogalli, S.; Mattei, D.; Carbillet, M.

    2015-03-01

    An overview is presented of the Segmented Pupil Experiment for Exoplanet Detection (SPEED) testbench. This is an advanced facility in development at the Lagrange Laboratory that will address several of the most critical issues affecting high-contrast imaging for the next generation of optical/near-infrared telescopes. The SPEED testbed can be used to investigate practical solutions for broadband coronography on asymmetric, unfriendly apertures, enabling algorithmic or optical approaches to be developed to minimise segment effects and pupil discontinuity.

  19. Photonic heterostructure High Contrast Grating as a novel polarization control and light confinement system in HCG VCSEL

    Science.gov (United States)

    Gebski, M.; Dems, M.; Chen, J.; Qijie, W.; Dao Hua, Z.; Czyszanowski, T.

    2014-05-01

    In this paper we present results of computer optical simulations of VCSEL with modified high refractive index contrast grating (HCG) as a top mirror. We consider the HCG of two different designs which determine the lateral aperture. Such HCG mirror provides selective guiding effect. We show that proper design of aperture of HCG results in almost sixfold increase in cavity Q-factor for zero order mode and a discrimination of higher order modes.

  20. Monitoring Rates and Heterogeneity of High-Pressure Germination of Bacillus Spores by Phase-Contrast Microscopy of Individual Spores

    Science.gov (United States)

    2014-01-01

    SECURITY CLASSIFICATION OF: The germination of multiple individual Bacillus subtilis spores by a high pressure (HP) of 140-150 (unless noted...otherwise) megaPascals (MPa) that activates spore germinant receptors (GRs) was monitored by phase contrast microscopy in a diamond anvil cell. Major...conclusions were that: i) >95% of spores germinated in 40 min; ii) individual spore’s HP germination kinetics were very similar to those for nutrient

  1. Lumazine Synthase Protein Nanoparticle-Gd(III)-DOTA Conjugate as a T1 contrast agent for high-field MRI.

    Science.gov (United States)

    Song, YoungKyu; Kang, Young Ji; Jung, Hoesu; Kim, Hansol; Kang, Sebyung; Cho, HyungJoon

    2015-10-23

    With the applications of magnetic resonance imaging (MRI) at higher magnetic fields increasing, there is demand for MRI contrast agents with improved relaxivity at higher magnetic fields. Macromolecule-based contrast agents, such as protein-based ones, are known to yield significantly higher r1 relaxivity at low fields, but tend to lose this merit when used as T1 contrast agents (r1/r2 = 0.5 ~ 1), with their r1 decreasing and r2 increasing as magnetic field strength increases. Here, we developed and characterized an in vivo applicable magnetic resonance (MR) positive contrast agent by conjugating Gd(III)-chelating agent complexes to lumazine synthase isolated from Aquifex aeolicus (AaLS). The r1 relaxivity of Gd(III)-DOTA-AaLS-R108C was 16.49 mM(-1)s(-1) and its r1/r2 ratio was 0.52 at the magnetic field strength of 7 T. The results of 3D MR angiography demonstrated the feasibility of vasculature imaging within 2 h of intravenous injection of the agent and a significant reduction in T1 values were observed in the tumor region 7 h post-injection in the SCC-7 flank tumor model. Our findings suggest that Gd(III)-DOTA-AaLS-R108C could serve as a potential theranostic nanoplatform at high magnetic field strength.

  2. Can the evaluation of a simple test object be used to predict the performance of a contrast-detail analysis in digital mammography?

    Science.gov (United States)

    Bosmans, H.; Lemmens, K.; Jacobs, J.; Vandenbroucke, D.; Zanca, F.; Michielsen, K.; Verbrugge, B.; Smans, K.; Marchal, G.

    2009-02-01

    The purpose was to find the correlation between a Figure of Merit (FoM) calculated from a new (simple) test object for Quality Control in digital mammography and CDMAM threshold thicknesses. The FoM included the signal difference to noise ratio, modulation transfer function of the complete system (including scatter and grid) and normalized noise power spectrum. The pre-programmed exposure settings for clinical work were used, as was done for the CDMAM acquisitions. The FoM is calculated from 2 images only (an image from the QC test object and an image of a corresponding homogeneous plate imaged with the same exposure settings). This FoM was evaluated in frequencies that match with the diameters of the gold disks in the CDMAM phantom. Computerized CDMAM analysis uses 16 images per system. The software program "cdcom" (www.euref.org) was used for the 4-AFC experiment. All matrices were averaged, smoothed with a Gaussian filter and psychometric curves were fitted through the correctly detected fractions to obtain the threshold thickness with a detectability of 62.5% for all diameters. Images have been acquired on 10 different systems (2 computed radiography (CR) systems, 6 direct radiology (DR) systems and 2 photon counting systems). The reproducibility of the QC metrics from images of the new phantom was assessed. The standard error on the mean of the FoM was for the highest frequency 8.1% for a CR system and 5.6% for a DR system. The main component in this error is due to the NNPS and the limited number of independent pixels used in this analysis. Parameters calculated from both phantoms are sensitive to variation in mean glandular dose levels. Present results show a weak correlation (R2=0.60) between the FoM at 5lp/mm and CDMAM threshold values for the 0.1mm objects when all system data are pooled. If evaluated for separate systems, the correlation holds promise for automated, periodic performance evaluations of digital mammography systems with the simplified

  3. Solving A Kind of High Complexity Multi-Objective Problems by A Fast Algorithm

    Institute of Scientific and Technical Information of China (English)

    Zeng San-you; Ding Li-xin; Kang Li-shan

    2003-01-01

    A fast algorithm is proposed to solve a kind of high complexity multi-objective problems in this paper. It takes advantages of both the orthogonal design method to search evenly, and the statistical optimal method to speed up the computation. It is very suitable for solving high complexity problems, and quickly yields solutions which converge to the Pareto-optimal set with high precision and uniform distribution. Some complicated multi objective problems are solved by the algorithm and the results show that the algorithm is not only fast but also superior to other MCGAS and MOEAs, such as the currently efficient algorithm SPEA, in terms of the precision, quantity and distribution of solutions.

  4. Long-Lasting and Efficient Tumor Imaging Using a High Relaxivity Polysaccharide Nanogel Magnetic Resonance Imaging Contrast Agent.

    Science.gov (United States)

    Chan, Minnie; Lux, Jacques; Nishimura, Tomoki; Akiyoshi, Kazunari; Almutairi, Adah

    2015-09-14

    Clinically approved small-molecule magnetic resonance imaging (MRI) contrast agents are all rapidly cleared from the body and offer weak signal enhancement. To avoid repeated administration of contrast agent and improve signal-to-noise ratios, agents with stronger signal enhancement and better retention in tumors are needed. Therefore, we focused on hydrogels because of their excellent water accessibility and biodegradability. Gadolinium (Gd)-chelating cross-linkers were incorporated into self-assembled pullulan nanogels to both impart magnetic properties and to stabilize this material that has been extensively studied for medical applications. We show that these Gd-chelating pullulan nanogels (Gd-CHPOA) have the highest reported relaxivity for any hydrogel-based particles and accumulate in the 4T1 tumors in mice at high levels 4 h after injection. This combination offers high signal enhancement and lasts up to 7 days to delineate the tumor clearly for longer imaging time scales. Importantly, this long-term accumulation does not cause any damage or toxicity in major organs up to three months after injection. Our work highlights the clinical potential of Gd-CHPOA as a tumor-imaging MRI contrast agent, permitting tumor identification and assessment with a high signal-to-background ratio.

  5. Experimental verification of beam quality in high-contrast imaging with orthogonal bremsstrahlung photon beams.

    Science.gov (United States)

    Sarfehnia, Arman; Jabbari, Keyvan; Seuntjens, Jan; Podgorsak, Ervin B

    2007-07-01

    Since taken with megavoltage, forward-directed bremsstrahlung beams, the image quality of current portal images is inferior to that of diagnostic quality images produced by kilovoltage beams. In this paper, the beam quality of orthogonal bremsstrahlung beams defined as the 90 degrees component of the bremsstrahlung distribution produced from megavoltage electron pencil beams striking various targets is presented, and the suitability of their use for improved radiotherapy imaging is evaluated. A 10 MeV electron beam emerging through the research port of a Varian Clinac-18 linac was made to strike targets of carbon, aluminum, and copper. PDD and attenuation measurements of both the forward and orthogonal beams were carried out, and the results were also used to estimate the effective and mean energy of the beams. The mean energy of a spectrum produced by a carbon target dropped by 83% from 1296 keV in the forward direction to 217 keV in the orthogonal direction, while for an aluminum target it dropped by 77% to 412 keV, and for a copper target by 65% to 793 keV. An in-depth Monte Carlo study of photon yield and electron contamination was also performed. Photon yield and effective energy are lower for orthogonal beams than for forward beams, and the differences are more pronounced for targets of lower atomic number. Using their relatively low effective energy, orthogonal bremsstrahlung beams produced by megavoltage electrons striking low atomic number targets yield images with a higher contrast in comparison with forward bremsstrahlung beams.

  6. Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions

    Science.gov (United States)

    Rymaruk, Matthew J.; Thompson, Kate L.; Derry, Matthew J.; Warren, Nicholas J.; Ratcliffe, Liam P. D.; Williams, Clive N.; Brown, Steven L.; Armes, Steven P.

    2016-07-01

    We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral

  7. High-throughput Imaging of Self-luminous Objects through a Single Optical Fiber

    CERN Document Server

    Barankov, Roman

    2015-01-01

    Imaging through a single optical fiber offers attractive possibilities in many applications such as microendoscopy or remote sensing. However, the direct transmission of an image through an optical fiber is difficult because spatial information is scrambled upon propagation. We demonstrate an image transmission strategy where spatial information is first converted to spectral information. Our strategy is based on a principle of spread-spectrum encoding, borrowed from wireless communications, wherein object pixels are converted into distinct spectral codes that span the full bandwidth of the object spectrum. Image recovery is performed by numerical inversion of the detected spectrum at the fiber output. We provide a simple demonstration of spread-spectrum encoding using Fabry-Perot etalons. Our technique enables the 2D imaging of self-luminous (i.e. incoherent) objects with high throughput in principle independent of pixel number. Moreover, it is insensitive to fiber bending, contains no moving parts, and open...

  8. LAPACK++: A design overview of object-oriented extensions for high performance linear algebra

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J.J. [Oak Ridge National Lab., TN (United States). Mathematical Sciences Section]|[Univ. of Tennessee, Knoxville, TN (United States). Computer Science Dept.; Pozo, R. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Computer Science; Walker, D.W. [Oak Ridge National Lab., TN (United States). Mathematical Sciences Section

    1993-12-31

    LAPACK++ is an object-oriented C++ extension of the LAPACK (Linear Algebra PACKage) library for solving the common problems of numerical linear algebra: linear systems, linear least squares, and eigenvalue problems on high-performance computer architectures. The advantages of an object-oriented approach include the ability to encapsule various matrix representations, hide their implementation details, reduce the number of subroutines, simplify their calling sequences, and provide an extendible software framework that can incorporate future extensions of LAPACK such as ScaLAPACK++ for distributed memory architectures. The authors present an overview of the object-oriented design of the matrix and decomposition classes in C++ and discuss its impact on elegance, generality, and performance.

  9. LAPACK++: A design overview of object-oriented extensions for high performance linear algebra

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J.J. [Oak Ridge National Lab., TN (United States). Mathematical Sciences Section]|[Univ. of Tennessee, Knoxville (United States). Dept. of Computer Science; Pozo, R. [Univ. of Tennessee, Knoxville (United States). Dept. of Computer Science; Walker, D.W. [Oak Ridge National Lab., TN (United States). Mathematical Sciences Section

    1993-12-31

    LAPACK++ is an object-oriented C++ extension of the LAPACK (Linear Algebra PACKage) library for solving the common problems of numerical linear algebra: linear systems, linear least squares, and eigenvalue problems on high-performance computer architectures. The advantages of an object-oriented approach include the ability to encapsulate various matrix representations, hide their implementation details, reduce the number of subroutines, simplify their calling sequences, and provide an extendible software framework that can incorporate future extensions of LAPACK, such as ScaLAPACK++ for distributed memory architectures. The authors present an overview of the object-oriented design of the matrix and decomposition classes in C++ and discuss its impact on elegance, generality, and performance.

  10. How high is visual short-term memory capacity for object layout?

    Science.gov (United States)

    Sanocki, Thomas; Sellers, Eric; Mittelstadt, Jeff; Sulman, Noah

    2010-05-01

    Previous research measuring visual short-term memory (VSTM) suggests that the capacity for representing the layout of objects is fairly high. In four experiments, we further explored the capacity of VSTM for layout of objects, using the change detection method. In Experiment 1, participants retained most of the elements in displays of 4 to 8 elements. In Experiments 2 and 3, with up to 20 elements, participants retained many of them, reaching a capacity of 13.4 stimulus elements. In Experiment 4, participants retained much of a complex naturalistic scene. In most cases, increasing display size caused only modest reductions in performance, consistent with the idea of configural, variable-resolution grouping. The results indicate that participants can retain a substantial amount of scene layout information (objects and locations) in short-term memory. We propose that this is a case of remote visual understanding, where observers' ability to integrate information from a scene is paramount.

  11. High-contrast imager for Complex Aperture Telescopes (HiCAT). 4. Status and wavefront control development

    Science.gov (United States)

    Leboulleux, Lucie; N'Diaye, Mamadou; Riggs, A. J. E.; Egron, Sylvain; Mazoyer, Johan; Pueyo, Laurent; Choquet, Elodie; Perrin, Marshall D.; Kasdin, Jeremy; Sauvage, Jean-François; Fusco, Thierry; Soummer, Rémi

    2016-07-01

    Segmented telescopes are a possible approach to enable large-aperture space telescopes for the direct imaging and spectroscopy of habitable worlds. However, the increased complexity of their aperture geometry, due to their central obstruction, support structures and segment gaps, makes high-contrast imaging very challenging. The High-contrast imager for Complex Aperture Telescopes (HiCAT) was designed to study and develop solutions for such telescope pupils using wavefront control and starlight suppression. The testbed design has the flexibility to enable studies with increasing complexity for telescope aperture geometries starting with off-axis telescopes, then on-axis telescopes with central obstruction and support structures (e.g. the Wide Field Infrared Survey Telescope [WFIRST]), up to on-axis segmented telescopes e.g. including various concepts for a Large UV, Optical, IR telescope (LUVOIR), such as the High Definition Space Telescope (HDST). We completed optical alignment in the summer of 2014 and a first deformable mirror was successfully integrated in the testbed, with a total wavefront error of 13nm RMS over a 18mm diameter circular pupil in open loop. HiCAT will also be provided with a segmented mirror conjugated with a shaped pupil representing the HDST configuration, to directly study wavefront control in the presence of segment gaps, central obstruction and spider. We recently applied a focal plane wavefront control method combined with a classical Lyot coronagraph on HiCAT, and we found limitations on contrast performance due to vibration effect. In this communication, we analyze this instability and study its impact on the performance of wavefront control algorithms. We present our Speckle Nulling code to control and correct for wavefront errors both in simulation mode and on testbed mode. This routine is first tested in simulation mode without instability to validate our code. We then add simulated vibrations to study the degradation of contrast

  12. Microstructured Air Cavities as High-Index Contrast Substrates with Strong Diffraction for Light-Emitting Diodes.

    Science.gov (United States)

    Moon, Yoon-Jong; Moon, Daeyoung; Jang, Jeonghwan; Na, Jin-Young; Song, Jung-Hwan; Seo, Min-Kyo; Kim, Sunghee; Bae, Dukkyu; Park, Eun Hyun; Park, Yongjo; Kim, Sun-Kyung; Yoon, Euijoon

    2016-05-11

    Two-dimensional high-index-contrast dielectric gratings exhibit unconventional transmission and reflection due to their morphologies. For light-emitting devices, these characteristics help guided modes defeat total internal reflections, thereby enhancing the outcoupling efficiency into an ambient medium. However, the outcoupling ability is typically impeded by the limited index contrast given by pattern media. Here, we report strong-diffraction, high-index-contrast cavity engineered substrates (CESs) in which hexagonally arranged hemispherical air cavities are covered with a 80 nm thick crystallized alumina shell. Wavelength-resolved diffraction measurements and Fourier analysis on GaN-grown CESs reveal that the high-index-contrast air/alumina core/shell patterns lead to dramatic excitation of the low-order diffraction modes. Large-area (1075 × 750 μm(2)) blue-emitting InGaN/GaN light-emitting diodes (LEDs) fabricated on a 3 μm pitch CES exhibit ∼39% enhancement in the optical power compared to state-of-the-art, patterned-sapphire-substrate LEDs, while preserving all of the electrical metrics that are relevant to LED devices. Full-vectorial simulations quantitatively demonstrate the enhanced optical power of CES LEDs and show a progressive increase in the extraction efficiency as the air cavity volume is expanded. This trend in light extraction is observed for both lateral- and flip-chip-geometry LEDs. Measurements of far-field profiles indicate a substantial beaming effect for CES LEDs, despite their few-micron-pitch pattern. Near-to-far-field transformation simulations and polarization analysis demonstrate that the improved extraction efficiency of CES LEDs is ascribed to the increase in emissions via the top escape route and to the extraction of transverse-magnetic polarized light.

  13. The Nonlinear Statistics of High-contrast Patches in Natural Images

    DEFF Research Database (Denmark)

    Lee, Ann; Pedersen, Kim Steenstrup; Mumford, David

    2003-01-01

    of natural images, not just marginals, and the need to understand the intrinsic dimensionality and nature of the data. We believe that object-like structures in the world and the sensor properties of the probing device generate observations that are concentrated along predictable shapes in state space. Our......Recently, there has been a great deal of interest in modeling the non-Gaussian structures of natural images. However, despite the many advances in the direction of sparse coding and multi-resolution analysis, the full probability distribution of pixel values in a neighborhood has not yet been...... study of natural image statistics accounts for local geometries (such as edges) in natural scenes, but does not impose such strong assumptions on the data as independent components or sparse coding by linear change of bases....

  14. Interaction between High-Level and Low-Level Image Analysis for Semantic Video Object Extraction

    Directory of Open Access Journals (Sweden)

    Andrea Cavallaro

    2004-06-01

    Full Text Available The task of extracting a semantic video object is split into two subproblems, namely, object segmentation and region segmentation. Object segmentation relies on a priori assumptions, whereas region segmentation is data-driven and can be solved in an automatic manner. These two subproblems are not mutually independent, and they can benefit from interactions with each other. In this paper, a framework for such interaction is formulated. This representation scheme based on region segmentation and semantic segmentation is compatible with the view that image analysis and scene understanding problems can be decomposed into low-level and high-level tasks. Low-level tasks pertain to region-oriented processing, whereas the high-level tasks are closely related to object-level processing. This approach emulates the human visual system: what one “sees” in a scene depends on the scene itself (region segmentation as well as on the cognitive task (semantic segmentation at hand. The higher-level segmentation results in a partition corresponding to semantic video objects. Semantic video objects do not usually have invariant physical properties and the definition depends on the application. Hence, the definition incorporates complex domain-specific knowledge and is not easy to generalize. For the specific implementation used in this paper, motion is used as a clue to semantic information. In this framework, an automatic algorithm is presented for computing the semantic partition based on color change detection. The change detection strategy is designed to be immune to the sensor noise and local illumination variations. The lower-level segmentation identifies the partition corresponding to perceptually uniform regions. These regions are derived by clustering in an N-dimensional feature space, composed of static as well as dynamic image attributes. We propose an interaction mechanism between the semantic and the region partitions which allows to

  15. High spatial resolution image object classification for terrestrial oil spill contamination mapping in West Siberia

    Science.gov (United States)

    Hese, S.; Schmullius, C.

    2009-04-01

    This work is a part of the OSCaR pilot study (Oil Spill Contamination mapping in Russia). A synergetic concept for an object based and multi temporal mapping and classification system for terrestrial oil spill pollution using a test area in West Siberia is presented. An object oriented image classification system is created to map contaminated soils, vegetation and changes in the oil exploration well infrastructure in high resolution data. Due to the limited spectral resolution of Quickbird data context information and image object structure are used as additional features building a structural object knowledge base for the area. The distance of potentially polluted areas to industrial land use and infrastructure objects is utilized to classify crude oil contaminated surfaces. Additionally the potential of Landsat data for dating of oil spill events using change indicators is tested with multi temporal Landsat data from 1987, 1995 and 2001. OSCaR defined three sub-projects: (1) high resolution mapping of crude oil contaminated surfaces, (2) mapping of industrial infrastructure change, (3) dating of oil spill events using multi temporal Landsat data. Validation of the contamination mapping results has been done with field data from Russian experts provided by the Yugra State University in Khanty-Mansiyskiy. The developed image object structure classification system has shown good results for the severely polluted areas with good overall classification accuracy. However it has also revealed the need for direct mapping of hydrocarbon substances. Oil spill event dating with Landsat data was very much limited by the low spatial resolution of Landsat TM 5 data, small scale character of oil spilled surfaces and limited information about oil spill dates.

  16. High-resolution motion compensated MRA in patients with congenital heart disease using extracellular contrast agent at 3 Tesla

    Directory of Open Access Journals (Sweden)

    Dabir Darius

    2012-10-01

    Full Text Available Abstract Background Using first-pass MRA (FP-MRA spatial resolution is limited by breath-hold duration. In addition, image quality may be hampered by respiratory and cardiac motion artefacts. In order to overcome these limitations an ECG- and navigator-gated high-resolution-MRA sequence (HR-MRA with slow infusion of extracellular contrast agent was implemented at 3 Tesla for the assessment of congenital heart disease and compared to standard first-pass-MRA (FP-MRA. Methods 34 patients (median age: 13 years with congenital heart disease (CHD were prospectively examined on a 3 Tesla system. The CMR-protocol comprised functional imaging, FP- and HR-MRA, and viability imaging. After the acquisition of the FP-MRA sequence using a single dose of extracellular contrast agent the motion compensated HR-MRA sequence with isotropic resolution was acquired while injecting the second single dose, utilizing the timeframe before viability imaging. Qualitative scores for image quality (two independent reviewers as well as quantitative measurements of vessel sharpness and relative contrast were compared using the Wilcoxon signed-rank test. Quantitative measurements of vessel diameters were compared using the Bland-Altman test. Results The mean image quality score revealed significantly better image quality of the HR-MRA sequence compared to the FP-MRA sequence in all vessels of interest (ascending aorta (AA, left pulmonary artery (LPA, left superior pulmonary vein (LSPV, coronary sinus (CS, and coronary ostia (CO; all p  Conclusions An ECG- and navigator-gated HR-MRA-protocol with infusion of extracellular contrast agent at 3 Tesla is feasible. HR-MRA delivers significantly better image quality and vessel sharpness compared to FP-MRA. It may be integrated into a standard CMR-protocol for patients with CHD without the need for additional contrast agent injection and without any additional examination time.

  17. A multi-dimensional model for localization of highly variable objects

    Science.gov (United States)

    Ruppertshofen, Heike; Bülow, Thomas; von Berg, Jens; Schmidt, Sarah; Beyerlein, Peter; Salah, Zein; Rose, Georg; Schramm, Hauke

    2012-02-01

    In this work, we present a new type of model for object localization, which is well suited for anatomical objects exhibiting large variability in size, shape and posture, for usage in the discriminative generalized Hough transform (DGHT). The DGHT combines the generalized Hough transform (GHT) with a discriminative training approach to automatically obtain robust and efficient models. It has been shown to be a strong tool for object localization capable of handling a rather large amount of shape variability. For some tasks, however, the variability exhibited by different occurrences of the target object becomes too large to be represented by a standard DGHT model. To be able to capture such highly variable objects, several sub-models, representing the modes of variability as seen by the DGHT, are created automatically and are arranged in a higher dimensional model. The modes of variability are identified on-the-fly during training in an unsupervised manner. Following the concept of the DGHT, the sub-models are jointly trained with respect to a minimal localization error employing the discriminative training approach. The procedure is tested on a dataset of thorax radiographs with the target to localize the clavicles. Due to different arm positions, the posture and arrangement of the target and surrounding bones differs strongly, which hampers the training of a good localization model. Employing the new model approach the localization rate improves by 13% on unseen test data compared to the standard model.

  18. General Tool for Evaluating High-Contrast Coronagraphic Telescope Performance Error Budgets

    Science.gov (United States)

    Marchen, Luis F.

    2011-01-01

    The Coronagraph Performance Error Budget (CPEB) tool automates many of the key steps required to evaluate the scattered starlight contrast in the dark hole of a space-based coronagraph. The tool uses a Code V prescription of the optical train, and uses MATLAB programs to call ray-trace code that generates linear beam-walk and aberration sensitivity matrices for motions of the optical elements and line-of-sight pointing, with and without controlled fine-steering mirrors (FSMs). The sensitivity matrices are imported by macros into Excel 2007, where the error budget is evaluated. The user specifies the particular optics of interest, and chooses the quality of each optic from a predefined set of PSDs. The spreadsheet creates a nominal set of thermal and jitter motions, and combines that with the sensitivity matrices to generate an error budget for the system. CPEB also contains a combination of form and ActiveX controls with Visual Basic for Applications code to allow for user interaction in which the user can perform trade studies such as changing engineering requirements, and identifying and isolating stringent requirements. It contains summary tables and graphics that can be instantly used for reporting results in view graphs. The entire process to obtain a coronagraphic telescope performance error budget has been automated into three stages: conversion of optical prescription from Zemax or Code V to MACOS (in-house optical modeling and analysis tool), a linear models process, and an error budget tool process. The first process was improved by developing a MATLAB package based on the Class Constructor Method with a number of user-defined functions that allow the user to modify the MACOS optical prescription. The second process was modified by creating a MATLAB package that contains user-defined functions that automate the process. The user interfaces with the process by utilizing an initialization file where the user defines the parameters of the linear model

  19. Robust design of Si/Si3N4 high contrast grating mirror for mid-infrared VCSEL application

    CERN Document Server

    Chevallier, Christyves; Genty, Frédéric; Jacquet, Joel

    2012-01-01

    A Si/Si3N4 high contrast grating mirror has been designed for a VCSEL integration in mid-infrared ({\\lambda} = 2.65 $\\mu$m). The use of an optimization algorithm which maximizes a VCSEL mirror quality factor allowed the adjustment of the grating parameters while keeping large and shallow grating pattern. The robustness with respect to fabrication error has been enhanced thanks to a precise study of the grating dimension tolerances. The final mirror exhibits large high reflectivity bandwidth with a polarization selectivity and several percent of tolerance on the grating dimensions.

  20. Object-directed imitation in children with high-functioning autism: testing the social motivation hypothesis.

    Science.gov (United States)

    Nielsen, Mark; Slaughter, Virginia; Dissanayake, Cheryl

    2013-02-01

    Children with autism show clear deficits in copying others' bodily oriented actions whereas their capacity for replicating others' object-directed actions appears relatively spared. One explanation is that unlike bodily oriented actions, object-directed actions have tangible, functional outcomes and hence rely far less on social motivations for their production. To investigate this, we compared the performance of a group of children with high-functioning autism (HFA) and a group of typically developing (TD) children on two distinct object-directed tasks that are considered highly social: overimitation and synchronic imitation. Our findings were surprising. The HFA children copied all of a modeling adult's actions, including those that had no function or purpose (i.e. they overimitated), and they entered into extended bouts repeating an arbitrary action along with the adult who had a similar object to play with (i.e. they engaged in synchronic imitation). Moreover, they did so at rates indistinguishable from the TD children. This work demonstrates that the capacity and propensity for overimitation and synchronic imitation are intact in children with HFA, and questions whether socially based imitation should be considered an autism-specific deficit.

  1. High-contrast imager for Complex Aperture Telescopes (HiCAT): APLC/shaped-pupil hybrid coronagraph designs

    Science.gov (United States)

    N'Diaye, Mamadou; Choquet, Elodie; Carlotti, Alexis; Pueyo, Laurent; Egron, Sylvain; Leboulleux, Lucie; Levecq, Olivier; Perrin, Marshall D.; Wallace, J. Kent; Long, Chris; Lajoie, Rachel; Lajoie, Charles-Philippe; Eldorado Riggs, A. J.; Zimmerman, Neil T.; Groff, Tyler Dean; Kasdin, N. Jeremy; Vanderbei, Robert J.; Mawet, Dimitri; Macintosh, Bruce; Shaklan, Stuart; Soummer, Remi

    2015-01-01

    HiCAT is a high-contrast imaging testbed designed to provide complete solutions in wavefront sensing, control and starlight suppression with complex aperture telescopes. Primary mirror segmentation, central obstruction and spiders in the pupil of an on-axis telescope introduces additional diffraction features in the point spread function, which make high-contrast imaging very challenging. The testbed alignment was completed in the summer of 2014, exceeding specifications with a total wavefront error of 12nm rms with a 18mm pupil. Two deformable mirrors are to be installed for wavefront control in the fall of 2014. In this communication, we report on the first testbed results using a classical Lyot coronagraph. We have developed novel coronagraph designs combining an Apodized Pupil Lyot Coronagraph (APLC) with shaped-pupil type optimizations. We present the results of these new APLC-type solutions with two-dimensional shaped-pupil apodizers for the HiCAT geometry. These solutions render the system quasi-insensitive to jitter and low-order aberrations, while improving the performance in terms of inner working angle, bandpass and contrast over a classical APLC.

  2. Combined T2 and T1 measurements for improved perfusion and permeability studies in high field using dynamic contrast enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Bazelaire, Cedric de [Saint Louis Hospital, Radiology Department, Paris, Cedex 10 (France); Beth Israel Deaconess Medical Center and Harvard Medical School, Department of Radiology, Cambridge, MA (United States); Rofsky, Neil M.; Duhamel, Guillaume; Zhang, Jingbo; Alsop, David C. [Beth Israel Deaconess Medical Center and Harvard Medical School, Department of Radiology, Cambridge, MA (United States); Michaelson, M.D. [Massachusetts General Hospital, Department of Hematology/Oncology, Boston, MA (United States); George, Daniel [Dana Farber Cancer Institute, Department of Adult Oncology, Boston, MA (United States)

    2006-09-15

    This study analyzed the T2* effect of extracellularly distributed gadolinium contrast agents in arterial blood during tumor studies using T1-weighted sequences at high field strength. A saturation-prepared dual echo sequence with echo times of 1.5 and 3.5 ms was employed at 3 T to simultaneously characterize T1 and T2* of arterial blood during bolus administration of Gd-DTPA in 28 patients with body tumors. T2* effect and T1 effect of Gd-DTPA on image intensity of whole blood were calibrated in human blood samples with different concentrations of contrast agent. T2* was used to estimate concentration near the peak of the bolus. T1 was used to measure lower concentrations when T2* was not significant. T2* was measurable on calibration curves for Gd-DTPA concentrations higher than 4 mM. This concentration was exceeded in 18 patients. The mean signal intensity reduction because of T2* effect was estimated at 22{+-}14% of the T2* compensated signal. Using T2* measurements reduced underestimations of peak arterial Gd-DTPA concentration (59{+-}38%) and overestimation of permeability K{sup trans} (58%). The T2* effect of gadolinium contrast agents should therefore be accounted for when performing tumors study with T1-weighted sequences at high field strength. (orig.)

  3. Contrasted sensitivity of DMSP production to high light exposure in two Arctic under-ice blooms

    NARCIS (Netherlands)

    Galindo, Virginie; Levasseur, Maurice; Mundy, Christopher John; Gosselin, Michel; Scarratt, Michael; Papakyriakou, Tim; Stefels, Jacqueline; Gale, Matthew A.; Tremblay, Jean-Eric; Lizotte, Martine

    In polar regions, low-light acclimated phytoplankton thriving under sea ice may be suddenly exposed to high irradiance when ice pack breaks or surface currents carry them into adjacent ice-free areas. Here we experimentally determined how rapid shifts in light regime affect the phytoplankton and the

  4. VCSELs with a high-index-contrast grating for mode-division multiplexing

    DEFF Research Database (Denmark)

    Ran, Qijiang; Mørk, Jesper

    2013-01-01

    to excite a specific transverse mode, while its transmission phase is kept spatially constant. This laser can provide the selective excitation of a specific transverse mode, leading to a high coupling efficiency to a few mode fiber. Compared to the phase plate approach in current SDM systems, the HCG...

  5. A Simplified Method for Upscaling Composite Materials with High Contrast of the Conductivity

    KAUST Repository

    Ewing, R.

    2009-01-01

    A large class of industrial composite materials, such as metal foams, fibrous glass materials, mineral wools, and the like, are widely used in insulation and advanced heat exchangers. These materials are characterized by a substantial difference between the thermal properties of the highly conductive materials (glass or metal) and the insulator (air) as well as low volume fractions and complex network-like structures of the highly conductive components. In this paper we address the important issue for the engineering practice of developing fast, reliable, and accurate methods for computing the macroscopic (upscaled) thermal conductivities of such materials. We assume that the materials have constant macroscopic thermal conductivity tensors, which can be obtained by upscaling techniques based on the postprocessing of a number of linearly independent solutions of the steady-state heat equation on representative elementary volumes (REVs). We propose, theoretically justify, and computationally study a numerical method for computing the effective conductivities of materials for which the ratio δ of low and high conductivities satisfies δ ≪ 1. We show that in this case one needs to solve the heat equation in the region occupied by the highly conductive media only. Further, we prove that under certain conditions on the microscale geometry the proposed method gives an approximation that is O(δ)-close to the upscaled conductivity. Finally, we illustrate the accuracy and the limitations of the method on a number of numerical examples. © 2009 Society for Industrial and Applied Mathematics.

  6. Repeated, long-distance migrations by a philopatric predator targeting highly contrasting ecosystems

    Science.gov (United States)

    Lea, James S. E.; Wetherbee, Bradley M.; Queiroz, Nuno; Burnie, Neil; Aming, Choy; Sousa, Lara L.; Mucientes, Gonzalo R.; Humphries, Nicolas E.; Harvey, Guy M.; Sims, David W.; Shivji, Mahmood S.

    2015-06-01

    Long-distance movements of animals are an important driver of population spatial dynamics and determine the extent of overlap with area-focused human activities, such as fishing. Despite global concerns of declining shark populations, a major limitation in assessments of population trends or spatial management options is the lack of information on their long-term migratory behaviour. For a large marine predator, the tiger shark Galeocerdo cuvier, we show from individuals satellite-tracked for multiple years (up to 1101 days) that adult males undertake annually repeated, round-trip migrations of over 7,500 km in the northwest Atlantic. Notably, these migrations occurred between the highly disparate ecosystems of Caribbean coral reef regions in winter and high latitude oceanic areas in summer, with strong, repeated philopatry to specific overwintering insular habitat. Partial migration also occurred, with smaller, immature individuals displaying reduced migration propensity. Foraging may be a putative motivation for these oceanic migrations, with summer behaviour showing higher path tortuosity at the oceanic range extremes. The predictable migratory patterns and use of highly divergent ecosystems shown by male tiger sharks appear broadly similar to migrations seen in birds, reptiles and mammals, and highlight opportunities for dynamic spatial management and conservation measures of highly mobile sharks.

  7. Contrasted sensitivity of DMSP production to high light exposure in two Arctic under-ice blooms

    NARCIS (Netherlands)

    Galindo, Virginie; Levasseur, Maurice; Mundy, Christopher John; Gosselin, Michel; Scarratt, Michael; Papakyriakou, Tim; Stefels, Jacqueline; Gale, Matthew A.; Tremblay, Jean-Eric; Lizotte, Martine

    2016-01-01

    In polar regions, low-light acclimated phytoplankton thriving under sea ice may be suddenly exposed to high irradiance when ice pack breaks or surface currents carry them into adjacent ice-free areas. Here we experimentally determined how rapid shifts in light regime affect the phytoplankton and the

  8. High-contrast Near-infrared Imaging Polarimetry of the Protoplanetary Disk around RY TAU

    NARCIS (Netherlands)

    Takami, M.; Karr, J.L.; Hashimoto, J.; Kim, H.; Wisniewski, J.; Henning, T.; Grady, C.A.; Kandori, R.; Hodapp, K.W.; Kudo, T.; Kusakabe, N.; Chou, M.-Y.; Itoh, Y.; Momose, M.; Mayama, S.; Currie, T.; Follette, K.B.; Kwon, J.; Abe, L.; Brandner, W.; Brandt, T.D.; Carson, J.; Egner, S.E.; Feldt, M.; Guyon, O.; Hayano, Y.; Hayashi, M.; Hayashi, S.; Ishii, M.; Iye, M.; Janson, M.; Knapp, G.R.; Kuzuhara, M.; McElwain, M.W.; Matsuo, T.; Miyama, S.; Morino, J.-I.; Moro-Martin, A.; Nishimura, T.; Pyo, T.-S.; Serabyn, E.; Suto, H.; Suzuki, R.; Takato, N.; Terada, H.; Thalmann, C.; Tomono, D.; Turner, E.L.; Watanabe, M.; Yamada, T.; Takami, H.; Usuda, T.; Tamura, M.

    2013-01-01

    We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at the H band at a high resolution (~0.''05) for the first time, using Subaru/HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distri

  9. The coronagraphic Modal Wavefront Sensor: a hybrid focal-plane sensor for the high-contrast imaging of circumstellar environments

    CERN Document Server

    Wilby, Michael J; Snik, Frans; Korkiakoski, Visa; Pietrow, Alexander G M

    2016-01-01

    The raw coronagraphic performance of current high-contrast imaging instruments is limited by the presence of a quasi-static speckle (QSS) background, resulting from instrumental non-common path errors (NCPEs). Rapid development of efficient speckle subtraction techniques in data reduction has enabled final contrasts of up to 10-6 to be obtained, however it remains preferable to eliminate the underlying NCPEs at the source. In this work we introduce the coronagraphic Modal Wavefront Sensor (cMWS), a new wavefront sensor suitable for real-time NCPE correction. This pupil-plane optic combines the apodizing phase plate coronagraph with a holographic modal wavefront sensor, to provide simultaneous coronagraphic imaging and focal-plane wavefront sensing using the science point spread function. We first characterise the baseline performance of the cMWS via idealised closed-loop simulations, showing that the sensor successfully recovers diffraction-limited coronagraph performance over an effective dynamic range of +/...

  10. Polaritonic-to-Plasmonic Transition in Optically Resonant Bismuth Nanospheres for High-Contrast Switchable Ultraviolet Meta-Filters

    CERN Document Server

    Cuadrado, Alexander; Serna, Rosalia

    2015-01-01

    In the quest aimed at unveiling alternative plasmonic elements overcoming noble metals for selected applications in photonics, we investigate by numerical simulations the near ultraviolet-to-near infrared optical response of solid and liquid Bi nanospheres embedded in a dielectric matrix. We also determine the resulting transmission contrast upon reversible solid-liquid phase transition to evaluate their potential for switchable optical filtering. The optical response of the solid (liquid) Bi nanospheres is ruled by localized polaritonic (plasmonic) resonances tunable by controlling the diameter. For a selected diameter between 20 nm and 50 nm, both solid and liquid nanospheres present a dipolar resonance inducing a strong peak extinction in the near ultraviolet, however at different photon energies. This enables a high transmission contrast at selected near ultraviolet photon energies. It is estimated that a two-dimensional assembly of 20 nm solid Bi nanospheres with a surface coverage of 28% will totally ex...

  11. Low-stress and high-stress singing have contrasting effects on glucocorticoid response

    Directory of Open Access Journals (Sweden)

    Daisy eFancourt

    2015-09-01

    Full Text Available Performing music in public is widely recognised as a potentially stress-inducing activity. However, despite the interest in music performance as an acute psychosocial stressor, there has been relatively little research on the effects of public performance on the endocrine system. This study examined the impact of singing in a low-stress performance situation and a high-stress live concert on levels of glucocorticoids (cortisol and cortisone in 15 professional singers. The results showed a significant decrease in both cortisol and cortisone across the low-stress condition, suggesting that singing in itself is a stress-reducing (and possibly health-promoting activity, but significant increases across the high-stress condition. This is the first study to demonstrate that singing affects glucocorticoid responses and that these responses are modulated by the conditions of performance.

  12. Measuring the 3D shape of high temperature objects using blue sinusoidal structured light

    Science.gov (United States)

    Zhao, Xianling; Liu, Jiansheng; Zhang, Huayu; Wu, Yingchun

    2015-12-01

    The visible light radiated by some high temperature objects (less than 1200 °C) almost lies in the red and infrared waves. It will interfere with structured light projected on a forging surface if phase measurement profilometry (PMP) is used to measure the shapes of objects. In order to obtain a clear deformed pattern image, a 3D measurement method based on blue sinusoidal structured light is proposed in this present work. Moreover, a method for filtering deformed pattern images is presented for correction of the unwrapping phase. Blue sinusoidal phase-shifting fringe pattern images are projected on the surface by a digital light processing (DLP) projector, and then the deformed patterns are captured by a 3-CCD camera. The deformed pattern images are separated into R, G and B color components by the software. The B color images filtered by a low-pass filter are used to calculate the fringe order. Consequently, the 3D shape of a high temperature object is obtained by the unwrapping phase and the calibration parameter matrixes of the DLP projector and 3-CCD camera. The experimental results show that the unwrapping phase is completely corrected with the filtering method by removing the high frequency noise from the first harmonic of the B color images. The measurement system can complete the measurement in a few seconds with a relative error of less than 1 : 1000.

  13. High-contrast single-particle tracking by selective focal plane illumination microscopy.

    Science.gov (United States)

    Ritter, Jörg G; Veith, Roman; Siebrasse, Jan-Peter; Kubitscheck, Ulrich

    2008-05-12

    Wide-field single molecule microscopy is a versatile tool for analyzing dynamics and molecular interactions in biological systems. In extended three-dimensional systems, however, the method suffers from intrinsic out-of-focus fluorescence. We constructed a high-resolution selective plane illumination microscope (SPIM) to efficiently solve this problem. The instrument is an optical sectioning microscope featuring the high speed and high sensitivity of a video microscope. We present theoretical calculations and quantitative measurements of the illumination light sheet thickness yielding 1.7 microm (FWHM) at 543 nm, 2.0 microm at 633 nm, and a FWHM of the axial point spread function of 1.13 microm. A direct comparison of selective plane and epi-illumination of model samples with intrinsic background fluorescence illustrated the clear advantage of SPIM for such samples. Single fluorescent quantum dots in aqueous solution are readily visualized and tracked proving the suitability of our setup for the study of fast and dynamic processes in spatially extended biological specimens.

  14. Contrasting vulnerability of drained tropical and high-latitude peatlands to fluvial loss of stored carbon

    Science.gov (United States)

    Evans, Chris D.; Page, Susan E.; Jones, Tim; Moore, Sam; Gauci, Vincent; Laiho, Raija; Hruška, Jakub; Allott, Tim E. H.; Billett, Michael F.; Tipping, Ed; Freeman, Chris; Garnett, Mark H.

    2014-11-01

    Carbon sequestration and storage in peatlands rely on consistently high water tables. Anthropogenic pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of peat-forming vegetation and exposure of previously anaerobic peat to aerobic decomposition. This can shift peatlands from net CO2 sinks to large CO2 sources, releasing carbon held for millennia. Peatlands also export significant quantities of carbon via fluvial pathways, mainly as dissolved organic carbon (DOC). We analyzed radiocarbon (14C) levels of DOC in drainage water from multiple peatlands in Europe and Southeast Asia, to infer differences in the age of carbon lost from intact and drained systems. In most cases, drainage led to increased release of older carbon from the peat profile but with marked differences related to peat type. Very low DOC-14C levels in runoff from drained tropical peatlands indicate loss of very old (centuries to millennia) stored peat carbon. High-latitude peatlands appear more resilient to drainage; 14C measurements from UK blanket bogs suggest that exported DOC remains young (hydraulic conductivity and temperature, as well as the extent of disturbance associated with drainage, notably land use changes in the tropics. Data from the UK Peak District, an area where air pollution and intensive land management have triggered Sphagnum loss and peat erosion, suggest that additional anthropogenic pressures may trigger fluvial loss of much older (>500 year) carbon in high-latitude systems. Rewetting at least partially offsets drainage effects on DOC age.

  15. Atomic physics of relativistic high contrast laser-produced plasmas in experiments on Leopard laser facility at UNR

    Science.gov (United States)

    Safronova, A. S.; Kantsyrev, V. L.; Faenov, A. Y.; Safronova, U. I.; Wiewior, P.; Renard-Le Galloudec, N.; Esaulov, A. A.; Weller, M. E.; Stafford, A.; Wilcox, P.; Shrestha, I.; Ouart, N. D.; Shlyaptseva, V.; Osborne, G. C.; Chalyy, O.; Paudel, Y.

    2012-06-01

    The results of the recent experiments focused on study of x-ray radiation from multicharged plasmas irradiated by relativistic (I > 1019 W/cm2) sub-ps laser pulses on Leopard laser facility at NTF/UNR are presented. These shots were done under different experimental conditions related to laser pulse and contrast. In particular, the duration of the laser pulse was 350 fs or 0.8 ns and the contrast was varied from high (10-7) to moderate (10-5). The thin laser targets (from 4 to 750 μm) made of a broad range of materials (from Teflon to iron and molybden to tungsten and gold) were utilized. Using the x-ray diagnostics including the high-precision spectrometer with resolution R ˜ 3000 and a survey spectrometer, we have observed unique spectral features that are illustrated in this paper. Specifically, the observed L-shell spectra for Fe targets subject to high intensity lasers (˜1019 W/cm2) indicate electron beams, while at lower intensities (˜1016 W/cm2) or for Cu targets there is much less evidence for an electron beam. In addition, K-shell Mg features with dielectronic satellites from high-Rydberg states, and the new K-shell F features with dielectronic satellites including exotic transitions from hollow ions are highlighted.

  16. High-Contrast Electro-Optic Modulation of a Photonic Crystal Nanocavity by Electrical Gating of Graphene

    CERN Document Server

    Gan, Xuetao; Gao, Yuanda; Mak, Kin Fai; Yao, Xinwen; Li, Luozhou; Szep, Attila; Walker, Dennis; Hone, James; Heinz, Tony F; Englund, Dirk

    2012-01-01

    We demonstrate a high-contrast electro-optic modulation of a photonic crystal nanocavity integrated with an electrically gated monolayer graphene. A high quality (Q) factor air-slot nanocavity design is employed for high overlap between the optical field and graphene sheet. Tuning of graphene's Fermi level up to 0.8 eV enables efficient control of its complex dielectric constant, which allows modulation of the cavity reflection in excess of 10 dB for a swing voltage of only 1.5 V. We also observe a controllable resonance wavelength shift close to 2 nm around a wavelength of 1570 nm and a Q factor modulation in excess of three. These observations allow cavity-enhanced measurements of the graphene complex dielectric constant under different chemical potentials, in agreement with a theoretical model of the graphene dielectric constant under gating. This graphene-based nanocavity modulation demonstrates the feasibility of high-contrast, low-power frequency-selective electro-optic nanocavity modulators in graphene...

  17. Facile Preparation of a New Gadofullerene-Based Magnetic Resonance Imaging Contrast Agent with High 1H Relaxivity

    Science.gov (United States)

    Shu, Chunying; Corwin, Frank D.; Zhang, Jianfei; Chen, Zhijian; Reid, Jonathan E.; Sun, Minghao; Xu, Wei; Sim, Jae Hyun; Wang, Chunru; Fatouros, Panos P.; Esker, Alan R.; Gibson, Harry W.; Dorn, Harry C.

    2009-01-01

    A new magnetic resonance imaging (MRI) contrast agent based on the trimetallic nitride templated (TNT) metallofullerene, Gd3N@C80, was synthesized by a facile method in high yield. The observed longitudinal and transverse relaxivities, r1 and r2, for water hydrogens in the presence of the water-soluble gadofullerene 2, Gd3N@C80(OH)~26(CH2CH2COOM)~16 (M = Na or H), are 207 and 282 mM-1s-1 (per C80 cage) at 2.4 T, respectively; these values are 50 times larger than those of Gd3+ poly(aminocarboxylate) complexes, such as commercial Omniscan® and Magnevist®. This high 1H relaxivity for this new hydroxylated and carboxylated gadofullerene derivative provides high signal enhancement at significantly lower Gd concentration as demonstrated by in vitro and in vivo MRI studies. Dynamic light scattering data reveal a unimodal size distribution with an average hydrodynamic radius of ca. 78 nm in pure water (pH = 7), which is significantly different from other hydroxylated or carboxylated fullerene and metallofullerene derivatives reported to date. Agarose gel infusion results indicate that the gadofullerene 2 displayed diffusion properties different from that of commercial Omniscan® and those of PEG5000 modified Gd3N@C80. The reactive carboxyl functionality present on this highly efficient contrast agent may also serve as a precursor for biomarker tissue-targeting purposes. PMID:19445504

  18. The architecture of the LkCa 15 transitional disk revealed by high-contrast imaging

    CERN Document Server

    Thalmann, C; Hodapp, K; Janson, M; Grady, C A; Min, M; Ovelar, M de Juan; Carson, J; Brandt, T; Bonnefoy, M; McElwain, M W; Leisenring, J; Dominik, C; Henning, T; Tamura, M

    2014-01-01

    We present four new epochs of Ks-band images of the young pre-transitional disk around LkCa 15, and perform extensive forward modeling to derive the physical parameters of the disk. We find indications of strongly anisotropic scattering (Henyey-Greenstein g = 0.67 [-0.11,+0.18]) and a significantly tapered gap edge ('round wall'), but see no evidence that the inner disk, whose existence is predicted by the spectral energy distribution, shadows the outer regions of the disk visible in our images. We marginally confirm the existence of an offset between the disk center and the star along the line of nodes; however, the magnitude of this offset (x = 27 [-20,+19] mas) is notably lower than that found in our earlier H-band images (Thalmann et al. 2010). Intriguingly, we also find, at high significance, an offset of y = 69 [-25, +49] mas perpendicular to the line of nodes. If confirmed by future observations, this would imply a highly elliptical -- or otherwise asymmetric -- disk gap with an effective eccentricity ...

  19. A K-alpha x-ray source using high energy and high repetition rate laser system for phase contrast imaging.

    Science.gov (United States)

    Serbanescu, Cristina; Fourmaux, Sylvain; Kieffer, Jean-Claude; Kincaid, Russell; Krol, Andrzej

    2009-01-01

    K-alpha x-ray sources from laser produced plasmas provide completely new possibilities for x-ray phase-contrast imaging applications. By tightly focusing intense femtosecond laser pulses onto a solid target K-alpha x-ray pulses are generated through the interaction of energetic electrons created in the plasma with the bulk target. In this paper, we present a continuous and efficient Mo K-alpha x-ray source produced by a femtosecond laser system operating at 100 Hz repetition rate with maximum pulse energy of 110 mJ before compression. The source has an x-ray conversion efficiency of greater than 10(-5) into K-alpha line emission. In preparation for phase contrast imaging applications, the size of the resultant K-alpha x-ray emission spot has been also characterized. The source exhibits sufficient spatial coherence to observe phase contrast. We observe a relatively small broadening of the K-alpha source size compared to the size of the laser beam itself. Detailed characterization of the source including the x-ray spectrum and the x-ray average yield along with phase contrast images of test objects will be presented.

  20. Object oriented classification of high resolution data for inventory of horticultural crops

    Science.gov (United States)

    Hebbar, R.; Ravishankar, H. M.; Trivedi, S.; Subramoniam, S. R.; Uday, R.; Dadhwal, V. K.

    2014-11-01

    High resolution satellite images are associated with large variance and thus, per pixel classifiers often result in poor accuracy especially in delineation of horticultural crops. In this context, object oriented techniques are powerful and promising methods for classification. In the present study, a semi-automatic object oriented feature extraction model has been used for delineation of horticultural fruit and plantation crops using Erdas Objective Imagine. Multi-resolution data from Resourcesat LISS-IV and Cartosat-1 have been used as source data in the feature extraction model. Spectral and textural information along with NDVI were used as inputs for generation of Spectral Feature Probability (SFP) layers using sample training pixels. The SFP layers were then converted into raster objects using threshold and clump function resulting in pixel probability layer. A set of raster and vector operators was employed in the subsequent steps for generating thematic layer in the vector format. This semi-automatic feature extraction model was employed for classification of major fruit and plantations crops viz., mango, banana, citrus, coffee and coconut grown under different agro-climatic conditions. In general, the classification accuracy of about 75-80 per cent was achieved for these crops using object based classification alone and the same was further improved using minimal visual editing of misclassified areas. A comparison of on-screen visual interpretation with object oriented approach showed good agreement. It was observed that old and mature plantations were classified more accurately while young and recently planted ones (3 years or less) showed poor classification accuracy due to mixed spectral signature, wider spacing and poor stands of plantations. The results indicated the potential use of object oriented approach for classification of high resolution data for delineation of horticultural fruit and plantation crops. The present methodology is applicable at

  1. Improving Success Ratio of Object Search in Highly-Dynamic Mobile P2P Networks

    Science.gov (United States)

    Takeshita, Kei; Sasabe, Masahiro; Nakano, Hirotaka

    Mobile Ad Hoc Networks (MANETs) are temporal and infrastructure-independent wireless networks that consist of mobile nodes. For instance, a MANET can be used as an emergent network for communication among people when a disaster occurred. Since there is no central server in the network, each node has to find out its desired information (objects) by itself. Constructing a mobile Peer-to-Peer (P2P) network over the MANET can support the object search. Some researchers proposed construction schemes of mobile P2P networks, such as Ekta and MADPastry. They integrated DHT-based application-layer routing and network-layer routing to increase search efficiency. Furthermore, MADPastry proposed a clustering method which groups the overlay nodes according to their physical distance. However, it has also been pointed out that the search efficiency deteriorates in highly dynamic environments where nodes quickly move around. In this paper, we focus on route disappearances in the network layer which cause the deterioration of search efficiency. We describe the detail of this problem and evaluate quantitatively it through simulation experiments. We extend MADPastry by introducing a method sharing objects among nodes in a cluster. Through simulation experiments, we show that the proposed method can achieve up to 2.5 times larger success rate of object search than MADPastry.

  2. Evaluation of the therapeutic efficacy of high-intensity focused ultrasound ablation of hepatocellular carcinoma by three-dimensional sonography with a perflubutane-based contrast agent

    Energy Technology Data Exchange (ETDEWEB)

    Numata, Kazushi, E-mail: kz-numa@urahp.yokohama-cu.ac.j [Gastroenterological Center, Yokohama City University Medical Center, 4-57 Urafune-cho, Minami-ku, Yokohama, Kanagawa 232-0024 (Japan); Fukuda, Hiroyuki; Ohto, Masao; Itou, Ryu [Department of Internal Medicine, Naruto General Hospital, 167 Naruto, Sanbu, Chiba 289-1326 (Japan); Nozaki, Akito; Kondou, Masaaki; Morimoto, Manabu [Gastroenterological Center, Yokohama City University Medical Center, 4-57 Urafune-cho, Minami-ku, Yokohama, Kanagawa 232-0024 (Japan); Karasawa, Eii [Department of Gastroenterology, International University of Health and Welfare Atami Hospital, 13-1 Higashi Kaigan-cho, Atami, Shizuoka 413-0012 (Japan); Tanaka, Katsuaki [Gastroenterological Center, Yokohama City University Medical Center, 4-57 Urafune-cho, Minami-ku, Yokohama, Kanagawa 232-0024 (Japan)

    2010-08-15

    Objective: We performed contrast-enhanced three-dimensional sonography (CE 3D US) with a perflubutane-based contrast agent to immediately evaluate the completeness of ablation of small hepatocellular carcinoma (HCC) lesions by extracorporeal high-intensity focused ultrasound (HIFU). Subjects and methods: Twenty-one HCC lesions were treated by a single ultrasound-guided HIFU ablation session, and CE 3D US was performed before, immediately after, and 1 week, and 1 month after HIFU, and contrast-enhanced CT (CE CT) or contrast-enhanced MRI (CE MRI) was performed before HIFU, 1 week and 1 month after HIFU, and during the follow-up period. Results: Immediately and 1 month after HIFU, 17 lesions were evaluated as adequately ablated by CE 3D US, and the other 4 lesions as residual tumors. One month after HIFU, 18 were evaluated as adequately ablated by CE CT or CE MRI, and the other 3 as residual tumors. The evaluation by CE 3D US immediately after HIFU and by CE CT or CE MRI 1 month after HIFU was concordant with 20 lesions. The kappa value for agreement between the findings of CE 3D US and other modalities by two blinded observers was 0.83. When the 1-month CE CT or CE MRI findings were used as the reference standard, the sensitivity, specificity, and accuracy of CE 3D US immediately after HIFU for the diagnosis of the adequate ablation were 100%, 75%, and 95%, respectively. Conclusion: CE 3D US appears to be a useful method for immediate evaluation of therapeutic efficacy of HIFU ablation of HCC lesions.

  3. Retooling Laser Speckle Contrast Analysis Algorithm to Enhance Non-Invasive High Resolution Laser Speckle Functional Imaging of Cutaneous Microcirculation

    Science.gov (United States)

    Gnyawali, Surya C.; Blum, Kevin; Pal, Durba; Ghatak, Subhadip; Khanna, Savita; Roy, Sashwati; Sen, Chandan K.

    2017-01-01

    Cutaneous microvasculopathy complicates wound healing. Functional assessment of gated individual dermal microvessels is therefore of outstanding interest. Functional performance of laser speckle contrast imaging (LSCI) systems is compromised by motion artefacts. To address such weakness, post-processing of stacked images is reported. We report the first post-processing of binary raw data from a high-resolution LSCI camera. Sharp images of low-flowing microvessels were enabled by introducing inverse variance in conjunction with speckle contrast in Matlab-based program code. Extended moving window averaging enhanced signal-to-noise ratio. Functional quantitative study of blood flow kinetics was performed on single gated microvessels using a free hand tool. Based on detection of flow in low-flow microvessels, a new sharp contrast image was derived. Thus, this work presents the first distinct image with quantitative microperfusion data from gated human foot microvasculature. This versatile platform is applicable to study a wide range of tissue systems including fine vascular network in murine brain without craniotomy as well as that in the murine dorsal skin. Importantly, the algorithm reported herein is hardware agnostic and is capable of post-processing binary raw data from any camera source to improve the sensitivity of functional flow data above and beyond standard limits of the optical system. PMID:28106129

  4. Max CAPR: High-Resolution 3D Contrast-Enhanced MR Angiography With Acquisition Times Under 5 Seconds

    Science.gov (United States)

    Haider, Clifton R.; Borisch, Eric A.; Glockner, James F.; Mostardi, Petrice M.; Rossman, Phillip J.; Young, Phillip M.; Riederer, Stephen J.

    2011-01-01

    High temporal and spatial resolution is desired in imaging of vascular abnormalities having short arterial-to-venous transit times. Methods that exploit temporal correlation to reduce the observed frame time demonstrate temporal blurring, obfuscating bolus dynamics. Previously, a Cartesian acquisition with projection reconstruction-like (CAPR) sampling method has been demonstrated for three-dimensional contrast-enhanced angiographic imaging of the lower legs using two-dimensional sensitivity-encoding acceleration and partial Fourier acceleration, providing 1mm isotropic resolution of the calves, with 4.9-sec frame time and 17.6-sec temporal footprint. In this work, the CAPR acquisition is further undersampled to provide a net acceleration approaching 40 by eliminating all view sharing. The tradeoff of frame time and temporal footprint in view sharing is presented and characterized in phantom experiments. It is shown that the resultant 4.9-sec acquisition time, three-dimensional images sets have sufficient spatial and temporal resolution to clearly portray arterial and venous phases of contrast passage. It is further hypothesized that these short temporal footprint sequences provide diagnostic quality images. This is tested and shown in a series of nine contrast-enhanced MR angiography patient studies performed with the new method. PMID:20715291

  5. High-contrast linear optical pulse compression using a temporal hologram.

    Science.gov (United States)

    Li, Bo; Fernández-Ruiz, Maria R; Lou, Shuqin; Azaña, José

    2015-03-01

    Temporal holograms can be realized by temporal amplitude-only modulation devices and used for generation and processing of complex (amplitude and phase) time-domain signals. Based on the temporal hologram concept, we numerically and experimentally demonstrate a novel design for linear optical pulse compression using temporal modulation of continuous-wave light combined with dispersion. The newly introduced scheme overcomes the undesired background problem that is intrinsic to designs based on temporal zone plates, while also offering an energy efficiency of ~25%. This pulse compression scheme can ideally provide an arbitrarily high time-bandwidth product using a low peak-power modulation driving signal, though in practice it is limited by the achievable modulation bandwidth and dispersion amount.

  6. High-Contrast Near-Infrared Imaging Polarimetry of the Protoplanetary Disk around RY Tau

    CERN Document Server

    Takami, Michihiro; Hashimoto, Jun; Kim, Hyosun; Wisnewski, John; Henning, Thomas; Grady, Carol A; Kandori, Ryo; Hodapp, Klaus W; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Chou, Mei-Yin; Itoh, Yoichi; Momose, Munetake; Mayama, Satoshi; Currie, Thayne; Follette, Katherine B; Kwon, Jungmi; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D; Carson, Joseph; Egner, Sebastian E; Feldt, Markus; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko; Ishii, Miki; Iye, Masanori; Janson, Markus; Knapp, Gillian R; Kuzuhara, Masayuki; McElwain, Michael W; Matsuo, Taro; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suto, Hiroshi; Suzuki, Ryuji; Takato, Naruhisa; Terada, Hiroshi; Thalmann, Christian; Tomono, Daigo; Turner, Edwin L; Watanabe, Makoto; Yamada, Toru; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2013-01-01

    We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at H-band at a high resolution (~0".05) for the first time, using Subaru-HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distribution of bright emission with an angular scale similar to the disk observed at millimeter wavelengths. This distribution is offset toward the blueshifted jet, indicating the presence of a geometrically thick disk or a remnant envelope, and therefore the earliest stage of the Class II evolutionary phase. We perform comparisons between the observed PI distribution and disk models with: (1) full radiative transfer code, using the spectral energy distribution (SED) to constrain the disk parameters; and (2) monochromatic simulations of scattered light which explore a wide range of parameters space to constrain the disk and dust parameters. We show that these models cannot consistently explain the observed PI distribution, S...

  7. Applications of Three Dithienylpyrroles-Based Electrochromic Polymers in High-Contrast Electrochromic Devices

    Directory of Open Access Journals (Sweden)

    Yuh-Shan Su

    2017-03-01

    Full Text Available Three dithienylpyrroles (1-(4-(methylthiophenyl-2,5-di(thiophen-2-yl-pyrrole (MPS, 1-(4-methoxyphenyl-2,5-di(thiophen-2-yl-pyrrole (MPO, and 4-(2,5-di(thiophen-2-yl-pyrrol-1-ylbenzonitrile (ANIL were synthesized and their corresponding polydithienylpyrroles (PSNS were electrosynthesized using electrochemical polymerization. Spectroelectrochemical studies indicated that poly(1-(4-(methylthiophenyl-2,5-di(thiophen-2-yl-pyrrole (PMPS film was green, dark green, and brown in the neutral, oxidation, and highly oxidized state, respectively. The incorporation of a MPS unit into the PSNS backbone gave rise to a darker color than those of the MPO and ANIL units in the highly oxidized state. The PMPS film showed higher ΔTmax (54.47% at 940 nm than those of the PMPO (43.87% at 890 nm and PANIL (44.63% at 950 nm films in an ionic liquid solution. Electrochromic devices (ECDs employing PMPS, PMPO, and PANIL as anodic layers and poly(3,4-(2,2-diethypropylenedioxythiophene(PProDOT-Et2 as a cathodic layer were constructed. PMPO/PProDOT-Et2 ECD showed the highest ΔTmax (41.13% and coloration efficiency (674.67 cm2·C−1 at 626 nm, whereas PMPS/PProDOT-Et2 ECD displayed satisfactory ΔTmax (32.51% and coloration efficiency (637.25 cm2·C−1 at 590 nm. Repeated cyclic voltammograms of PMPS/PProDOT-Et2, PMPO/PProDOT-Et2, and PANIL/PProDOT-Et2 ECDs indicated that ECDs had satisfactory redox stability.

  8. HESS J1943+213: a non-classical high-frequency-peaked BL Lac object

    CERN Document Server

    Straal, Samayra M; van Leeuwen, Joeri; Clarke, Tracy E; Dubner, Gloria; Frey, Sandor; Giacani, Elsa; Paragi, Zsolt

    2016-01-01

    HESS J1943+213 is an unidentified TeV source that is likely a high-frequency-peaked BL Lac (HBL) object but also compatible with a pulsar wind nebula (PWN) nature. Each of these enormously different astronomical interpretations is supported by some of the observed unusual characteristics. In order to finally classify and understand this object we took a three-pronged approach, through time-domain, high angular resolution, and multi-frequency radio studies. First, our deep time-domain observations with the Arecibo telescope failed to uncover the putative pulsar powering the proposed PWN. We conclude with ~70% certainty that HESS J1943+213 does not host a pulsar. Second, long-baseline interferometry of the source with e-MERLIN at 1.5- and 5- GHz, shows only a core, a point source at ~ 1 - 100 milli-arcsecond resolution. Its 2013 flux density is about one-third lower than detected in 2011 observations with similar resolution. This radio variability of the core strengthens the HBL object hypothesis. More evidence...

  9. Laryngeal High-Speed Videoendoscopy: Sensitivity of Objective Parameters towards Recording Frame Rate

    Directory of Open Access Journals (Sweden)

    Anne Schützenberger

    2016-01-01

    Full Text Available The current use of laryngeal high-speed videoendoscopy in clinic settings involves subjective visual assessment of vocal fold vibratory characteristics. However, objective quantification of vocal fold vibrations for evidence-based diagnosis and therapy is desired, and objective parameters assessing laryngeal dynamics have therefore been suggested. This study investigated the sensitivity of the objective parameters and their dependence on recording frame rate. A total of 300 endoscopic high-speed videos with recording frame rates between 1000 and 15 000 fps were analyzed for a vocally healthy female subject during sustained phonation. Twenty parameters, representing laryngeal dynamics, were computed. Four different parameter characteristics were found: parameters showing no change with increasing frame rate; parameters changing up to a certain frame rate, but then remaining constant; parameters remaining constant within a particular range of recording frame rates; and parameters changing with nearly every frame rate. The results suggest that (1 parameter values are influenced by recording frame rates and different parameters have varying sensitivities to recording frame rate; (2 normative values should be determined based on recording frame rates; and (3 the typically used recording frame rate of 4000 fps seems to be too low to distinguish accurately certain characteristics of the human phonation process in detail.

  10. Nitrogen retention in contrasting temperate forests exposed to high nitrogen deposition

    Science.gov (United States)

    Staelens, J.; Adriaenssens, S.; Wuyts, K.; Verheyen, K.; Boeckx, P. F.

    2011-12-01

    A better understanding of factors affecting nitrogen (N) retention is needed to assess the impact of changing anthropogenic N emissions and climatic conditions on N cycling and N loss by terrestrial ecosystems. Retention of N has been demonstrated for a wide range of forests, including ecosystems exposed to chronically enhanced N deposition, but it is still unclear which factors determine this N retention capacity. Therefore, we examined the possible effects of forest type on N retention using stable N isotopes. The study was carried out in adjacent equal-aged deciduous (pedunculate oak (Quercus robur L.)) and coniferous (Scots pine (Pinus sylvestris L.)) stands with a similar stand history and growing on a well-drained sandy soil in a region with enhanced N deposition (Belgium). The N input-output budgets and gross soil N transformation rates differed significantly between the two stands. The forest floor was exposed to a high inorganic N input from atmospheric deposition, which was nearly twice as high in the pine stand (33 ± 2 kg N ha-1 yr-1; mean ± standard error) as in the oak stand (18 ± 1 kg N ha-1 yr-1). The N input was reflected in the soil solution under the rooting zone, but the mean nitrate concentration was eight times higher under pine (19 ± 5 mg N L-1) than under oak (2.3 ± 0.9 mg N L-1). Gross N dynamics in the mineral topsoil were determined by in situ 15N labelling of undisturbed soil cores combined with numerical data analysis. Gross N mineralization was two times faster in the oak soil while nitrate production was two times faster in the pine soil, indicating a dominant effect of vegetation cover on soil N cycling. The higher gross nitrification, particularly due to oxidation of organic N, in the pine soil compared to the oak soil, combined with negligible nitrate immobilization, was in line with the higher nitrate leaching under the pine forest. On a larger spatial and temporal scale, the fate of dissolved inorganic N within these forests

  11. Grating-based X-ray phase-contrast tomography of atherosclerotic plaque at high photon energies

    Energy Technology Data Exchange (ETDEWEB)

    Hetterich, Holger; Fill, Sandra [Klinikum der Ludwig-Maximilians-Univ., Muenchen (Germany). Inst. fuer Klinische Radiologie; Herzen, Julia [Technische Univ. Muenchen, Garching (Germany). Physik-Dept. und Inst. fuer Medizintechnik; Helmholtz-Zentrum Geesthacht, Geesthacht (Germany). Zentrum fuer Materialforschung] [and others

    2013-10-01

    Background: Tissue characterization of atherosclerosis by absorption-based imaging methods is limited due to low soft-tissue contrast. Grating-based phase-contrast computed tomography (PC-CT) may become an alternative for plaque assessment if the phase signal can be retrieved at clinically applicable photon energies. The aims of this feasibility study were (i) to characterize arterial vessels at low and high photon energies, (ii) to extract qualitative features and (iii) quantitative phase-contrast Hounsfield units (HU-phase) of plaque components at 53 keV using histopathology as gold standard. Materials and methods: Five human carotid artery specimens underwent grating-based PC-CT using synchrotron radiation of either 23 keV or 53 keV and histological work-up. Specimens without advanced atherosclerosis were used to extract signal criteria of vessel layers. Diseased specimens were screened for important plaque components including fibrous tissue (FT), lipid (LIP), necrotic core (NEC), intraplaque hemorrhage (IPH), inflammatory cell infiltration (INF) and calcifications (CA). Qualitative features as well as quantitative HU-phase were analyzed. Results: Thirty-three regions in 6 corresponding PC-CT scans and histology sections were identified. Healthy samples had the same signal characteristics at 23 keV and 53 keV with bright tunica intima and adventitia and dark media. Plaque components showed differences in signal intensity and texture at 53 keV. Quantitative analysis demonstrated the highest HU-phase of soft plaque in dense FT. Less organized LIP, NEC and INF were associated with lower HU-phase values. The highest HU-phase were measured in CA. Conclusion: PC-CT of atherosclerosis is feasible at high, clinically relevant photon energies and provides detailed information about plaque structure including features of high risk vulnerable plaques. (orig.)

  12. HIGH-CONTRAST NEAR-INFRARED IMAGING POLARIMETRY OF THE PROTOPLANETARY DISK AROUND RY TAU

    Energy Technology Data Exchange (ETDEWEB)

    Takami, Michihiro; Karr, Jennifer L.; Kim, Hyosun; Chou, Mei-Yin [Institute of Astronomy and Astrophysics, Academia Sinica. P.O. Box 23-141, Taipei 10617, Taiwan (China); Hashimoto, Jun; Kandori, Ryo; Kusakabe, Nobuhiko; Kwon, Jungmi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Wisniewski, John [H. L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States); Henning, Thomas; Brandner, Wolfgang [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Hodapp, Klaus W. [Institute for Astronomy, University of Hawaii, 640 North A' ohoku Place, Hilo, HI 96720 (United States); Kudo, Tomoyuki [Subaru Telescope, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Itoh, Yoichi [Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2 Nishigaichi, Sayo, Hyogo 679-5313 (Japan); Momose, Munetake [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512 (Japan); Mayama, Satoshi [The Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (SOKENDAI), Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193 (Japan); Currie, Thayne [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON (Canada); Follette, Katherine B. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson AZ 85721 (United States); Abe, Lyu, E-mail: hiro@asiaa.sinica.edu.tw [Laboratoire Lagrange (UMR 7293), Universite de Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d' Azur, 28 Avenue Valrose, F-06108 Nice Cedex 2 (France); and others

    2013-08-01

    We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at the H band at a high resolution ({approx}0.''05) for the first time, using Subaru/HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distribution of bright emission with an angular scale similar to the disk observed at millimeter wavelengths. This distribution is offset toward the blueshifted jet, indicating the presence of a geometrically thick disk or a remnant envelope, and therefore the earliest stage of the Class II evolutionary phase. We perform comparisons between the observed PI distribution and disk models with (1) full radiative transfer code, using the spectral energy distribution (SED) to constrain the disk parameters; and (2) monochromatic simulations of scattered light which explore a wide range of parameters space to constrain the disk and dust parameters. We show that these models cannot consistently explain the observed PI distribution, SED, and the viewing angle inferred by millimeter interferometry. We suggest that the scattered light in the near-infrared is associated with an optically thin and geometrically thick layer above the disk surface, with the surface responsible for the infrared SED. Half of the scattered light and thermal radiation in this layer illuminates the disk surface, and this process may significantly affect the thermal structure of the disk.

  13. Strong coupling and high contrast all optical modulation in atomic cladding waveguides

    CERN Document Server

    Stern, Liron; Mazurski, Noa; Levy, Uriel

    2016-01-01

    In recent years we are witnessing a flourish in research aimed to facilitate alkali vapors in guided wave configurations. Owing to the significant reduction in device dimensions, the increase in density of states, the interaction with surfaces and primarily the high intensities carried along the structure, a rich world of light vapor interactions can be studied, and new functionalities, e.g. low power nonlinear light-matter interactions can be achieved. One immense remaining challenge is to study the effects of quantum coherence and shifts in such nano-scale waveguides, characterized by ultra-small mode areas and fast dynamics. Here, we construct a serpentine silicon-nitride wave guide, having atomic vapor as its cladding. The unprecedented mode volume of 5e-13 m^3 supported over a length of 17 mm is used to demonstrate efficient linear and non-linear spectroscopy. Fascinating and important phenomena such as van der Waals shifts, dynamical stark shifts, and coherent effects such as strong coupling (in the for...

  14. Feasible optimal deformable mirror shaping algorithm for high-contrast imaging

    Science.gov (United States)

    Give'on, Amir; Kasdin, N. Jeremy; Vanderbei, Robert J.; Spergel, David N.; Littman, Michael G.; Gurfil, Pini

    2003-12-01

    The Princeton University Terrestrial Planet Finder (TPF) group has been working on a novel method for direct imaging of extra solar planets using a shaped-pupil coronagraph. The entrance pupil of the coronagraph is optimized to have a point spread function (PSF) that provides the suppression level needed at the angular separation required for detection of extra solar planets. When integration time is to be minimized, the photon count at the planet location in the image plane is a Poisson distributed random process. The ultimate limitation of these high-dynamic-range imaging systems comes from scattering due to imperfections in the optical surfaces of the collecting system. The first step in correcting the wavefront errors is the estimation of the phase aberrations. The phase aberration caused by these imperfections is assumed to be a sum of two-dimensional sinusoidal functions. Assuming one uses a deformable mirror to correct these aberrations, we propose an algorithm that optimally decreases the scattering level in specified localized areas in the image plane independent of the choice of influence function of the deformable mirror.

  15. High-Contrast Near-Infrared Imaging Polarimetry of the Protoplanetary Disk around RY Tau

    Science.gov (United States)

    Takami, Michihiro; Karr, Jennifer L.; Hashimoto, Jun; Kim, Hyosun; Wisenewski, John; Henning, Thomas; Grady, Carol; Kandori, Ryo; Hodapp, Klaus W.; Kudo, Tomoyuki; hide

    2013-01-01

    We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at H-band at a high resolution (approx. 0.05) for the first time, using Subaru-HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distribution of bright emission with an angular scale similar to the disk observed at millimeter wavelengths. This distribution is offset toward the blueshifted jet, indicating the presence of a geometrically thick disk or a remnant envelope, and therefore the earliest stage of the Class II evolutionary phase. We perform comparisons between the observed PI distribution and disk models with: (1) full radiative transfer code, using the spectral energy distribution (SED) to constrain the disk parameters; and (2) monochromatic simulations of scattered light which explore a wide range of parameters space to constrain the disk and dust parameters. We show that these models cannot consistently explain the observed PI distribution, SED, and the viewing angle inferred by millimeter interferometry. We suggest that the scattered light in the near-infrared is associated with an optically thin and geometrically thick layer above the disk surface, with the surface responsible for the infrared SED. Half of the scattered light and thermal radiation in this layer illuminates the disk surface, and this process may significantly affect the thermal structure of the disk.

  16. High-density speckle contrast optical tomography (SCOT) for three dimensional tomographic imaging of the small animal brain.

    Science.gov (United States)

    Dragojević, Tanja; Varma, Hari M; Hollmann, Joseph L; Valdes, Claudia P; Culver, Joseph P; Justicia, Carles; Durduran, Turgut

    2017-06-01

    High-density speckle contrast optical tomography (SCOT) utilizing tens of thousands of source-detector pairs, was developed for in vivo imaging of blood flow in small animals. The reduction in cerebral blood flow (CBF) due to local ischemic stroke in a mouse brain was transcanially imaged and reconstructed in three dimensions. The reconstructed volume was then compared with corresponding magnetic resonance images demonstrating that the volume of reduced CBF agrees with the infarct zone at twenty-four hours. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Facile Preparation of a New Gadofullerene-Based Magnetic Resonance Imaging Contrast Agent with High 1H Relaxivity

    OpenAIRE

    Shu, Chunying; Corwin, Frank D.; Zhang, Jianfei; Chen, Zhijian; Reid, Jonathan E.; Sun, Minghao; Xu, Wei; Sim, Jae Hyun; Wang, Chunru; Fatouros, Panos P.; Alan R Esker; Gibson, Harry W.; Dorn, Harry C.

    2009-01-01

    A new magnetic resonance imaging (MRI) contrast agent based on the trimetallic nitride templated (TNT) metallofullerene, Gd3N@C80, was synthesized by a facile method in high yield. The observed longitudinal and transverse relaxivities, r1 and r2, for water hydrogens in the presence of the water-soluble gadofullerene 2, Gd3N@C80(OH)~26(CH2CH2COOM)~16 (M = Na or H), are 207 and 282 mM-1s-1 (per C80 cage) at 2.4 T, respectively; these values are 50 times larger than those of Gd3+ poly(aminocarbo...

  18. A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams.

    Science.gov (United States)

    Opachich, Y P; Koch, J A; Haugh, M J; Romano, E; Lee, J J; Huffman, E; Weber, F A; Bowers, J W; Benedetti, L R; Wilson, M; Prisbrey, S T; Wehrenberg, C E; Baumann, T F; Lenhardt, J M; Cook, A; Arsenlis, A; Park, H-S; Remington, B A

    2016-07-01

    A multi-wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ∼10.3% accuracy with ∼30 μm spatial resolution. The system description, performance, and measurement results collected using a 17.8 mg/cc carbon based JX-6 (C20H30) aerogel are discussed in this manuscript.

  19. Very high energy observations of the BL Lac objects 3C 66A and OJ 287

    CERN Document Server

    Lindner, T; Kildea, J; Ball, J; Bramel, D A; Carson, J; Covault, C E; Driscoll, D; Fortin, P; Gingrich, D M; Jarvis, A; Müller, C; Mukherjee, R; Ong, R A; Ragan, K; Scalzo, R A; Williams, D A; Zweerink, J

    2007-01-01

    Using the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), we have observed the BL Lac objects 3C 66A and OJ 287. These are members of the class of low-frequency-peaked BL Lac objects (LBLs) and are two of the three LBLs predicted by Costamante and Ghisellini to be potential sources of very high energy (>100 GeV) gamma-ray emission. The third candidate, BL Lacertae, has recently been detected by the MAGIC collaboration. Our observations have not produced detections; we calculate a 99% CL upper limit of flux from 3C 66A of 0.15 Crab flux units and from OJ 287 our limit is 0.52 Crab. These limits assume a Crab-like energy spectrum with an effective energy threshold of 185 GeV.

  20. Moving Object Detection Using Scanning Camera on a High-Precision Intelligent Holder

    Directory of Open Access Journals (Sweden)

    Shuoyang Chen

    2016-10-01

    Full Text Available During the process of moving object detection in an intelligent visual surveillance system, a scenario with complex background is sure to appear. The traditional methods, such as “frame difference” and “optical flow”, may not able to deal with the problem very well. In such scenarios, we use a modified algorithm to do the background modeling work. In this paper, we use edge detection to get an edge difference image just to enhance the ability of resistance illumination variation. Then we use a “multi-block temporal-analyzing LBP (Local Binary Pattern” algorithm to do the segmentation. In the end, a connected component is used to locate the object. We also produce a hardware platform, the core of which consists of the DSP (Digital Signal Processor and FPGA (Field Programmable Gate Array platforms and the high-precision intelligent holder.

  1. Acrylic-based 1×2 Y-Branch POF coupler with high index contrast waveguide taper

    Science.gov (United States)

    Ehsan, A. A.; Abd Rahman, M. K.

    2011-01-01

    An acrylic-based 1x2 Y-Branch POF coupler consists of input POF waveguide, a middle high index contrast waveguide taper and output POF waveguides has been developed. The optical device is based on a 1x2 Y-branch coupler design with a middle high index contrast waveguide taper. Device modeling has been performed using non-sequential ray tracing with an insertion loss of 4.68 dB and coupling ratio of 50:50. Low cost acrylic material has been used for the device substrate. This middle waveguide taper region is constructed on the acrylic block itself without using any additional optical waveguiding medium injected into the engraved taper region. Fabrication of the devices is done by producing the device structures on an acrylic block using high speed CNC machining tool. Input and output POF fibers are inserted in to this device structure in such a way that they are passively aligned to the middle waveguide taper structure. The measured insertion loss is 7.5 dB and with a splitting ratio of 50:50.

  2. The Subaru Coronagraphic Extreme Adaptive Optics system: enabling high-contrast imaging on solar-system scales

    CERN Document Server

    Jovanovic, N; Guyon, O; Clergeon, C; Singh, G; Kudo, T; Garrel, V; Newman, K; Doughty, D; Lozi, J; Males, J; Minowa, Y; Hayano, Y; Takato, N; Morino, J; Kuhn, J; Serabyn, E; Norris, B; Tuthill, P; Schworer, G; Stewart, P; Close, L; Huby, E; Perrin, G; Lacour, S; Gauchet, L; Vievard, S; Murakami, N; Oshiyama, F; Baba, N; Matsuo, T; Nishikawa, J; Tamura, M; Lai, O; Marchis, F; Duchene, G; Kotani, T; Woillez, J

    2015-01-01

    The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument is a multipurpose high-contrast imaging platform designed for the discovery and detailed characterization of exoplanetary systems and serves as a testbed for high-contrast imaging technologies for ELTs. It is a multi-band instrument which makes use of light from 600 to 2500nm allowing for coronagraphic direct exoplanet imaging of the inner 3 lambda/D from the stellar host. Wavefront sensing and control are key to the operation of SCExAO. A partial correction of low-order modes is provided by Subaru's facility adaptive optics system with the final correction, including high-order modes, implemented downstream by a combination of a visible pyramid wavefront sensor and a 2000-element deformable mirror. The well corrected NIR (y-K bands) wavefronts can then be injected into any of the available coronagraphs, including but not limited to the phase induced amplitude apodization and the vector vortex coronagraphs, both of which offer an inner worki...

  3. Spatio-temporal experiments of volume elastic objects with high speed digital holographic interferometry

    Science.gov (United States)

    Pérez López, C.; Hernández Montes, M. S.; Mendoza Santoyo, F.; Gutiérrez Hernandez, D. A.

    2011-08-01

    The optical non-destructive digital holographic interferometry (DHI) technique has proven to be a powerful tool in measuring vibration phenomena with a spatial resolution ranging from a few hundreds of nanometers to tens of micrometers. With the aid of high speed digital cameras it is possible to achieve simultaneously spatial and temporal resolution, and thus capable of measuring the entire object mechanical oscillation trajectory from one to several cycles. It is important to mention that due to faster computers with large data storage capacity there is an increasing interest in applying numerical simulation methods to mimic different real life objects for example, in the field of modern elastic materials and biological systems. The complex algorithms involved cannot render significant results mainly due to the rather large number of variables. In order to test these numerical simulations some experiments using optical techniques have been designed and reported. This is very important for example in measurements of the dynamic elastic properties of materials. In this work we present some preliminary results from experiments that use DHI to measure vibrations of an elastic spherical object subject to a mechanical excitation that induces resonant vibration modes in its volume. We report on the spatial and temporal effects that by their nature have a non-linear mechanical response. The use of a high speed CMOS camera in DHI assures the measurement of this nonlinear behavior as a sum of linear effects that happen during very short time lapses and with very small displacement amplitudes. We conclude by stating that complex numerical models may be compared to results using DHI, thus proposing an alternative method to prove and verify the mathematical models vs. real measurements on volumetric elastic objects.

  4. Innovative activity of high-technology companies as assessment and forecasting object

    Directory of Open Access Journals (Sweden)

    A. E. Sklyarov

    2016-01-01

    Full Text Available Innovation activities, as well as innovations, are closely related meanings, and like many others economical definitions, have a broad range of meanings. Main characteristics and attributes of innovation involves new or significantly improved product, that’s being used, or in other words, found its application, and innovative activities – activities focused on realization of innovations. In this article, innovations are mainly considered in terms of high-technology production, evidence from Russian space industry. There are 5 basic stages of lifecycle of innovative project in considered industry: initiation, development, realization, expansion, consumption. Practically, third or fourth, or even both of these stages, often missing because there is no need of them. R&D activities, or even further serial production, based on previous developments, is an innovation activity, because these activities are stages of innovative projects lifecycle itself. Then it seems legit, to draw a conclusion, that in terms of high-technology production, company’s primary activity equals innovative activity. Basic characteristics of innovative activity of high-technology companies as assessment and forecasting object involves high level of uncertainty at every stage of projects lifecycle, high dependency on funding level of this activity, and high level and erratic structure of risk. All the above mentioned, means that assessment and forecasting of innovative activity of high-technology companies, needs development of its own methodological tools for each industry.

  5. Pulsed x-ray imaging of high-density objects using a ten picosecond high-intensity laser driver

    Science.gov (United States)

    Rusby, D. R.; Brenner, C. M.; Armstrong, C.; Wilson, L. A.; Clarke, R.; Alejo, A.; Ahmed, H.; Butler, N. M. H.; Haddock, D.; Higginson, A.; McClymont, A.; Mirfayzi, S. R.; Murphy, C.; Notley, M.; Oliver, P.; Allott, R.; Hernandez-Gomez, C.; Kar, S.; McKenna, P.; Neely, D.

    2016-10-01

    Point-like sources of X-rays that are pulsed (sub nanosecond), high energy (up to several MeV) and bright are very promising for industrial and security applications where imaging through large and dense objects is required. Highly penetrating X-rays can be produced by electrons that have been accelerated by a high intensity laser pulse incident onto a thin solid target. We have used a pulse length of 10ps to accelerate electrons to create a bright x-ray source. The bremsstrahlung temperature was measured for a laser intensity from 8.5-12×1018 W/cm2. These x-rays have sequentially been used to image high density materials using image plate and a pixelated scintillator system.

  6. High contrast imaging with an arbitrary aperture: active correction of aperture discontinuities: fundamental limits and practical trades offs

    Science.gov (United States)

    Pueyo, Laurent; Norman, Colin Arthur; Soummer, Remi; Perrin, Marshall D.; N'Diaye, Mamadou; Choquet, Elodie

    2015-01-01

    In a recent paper we discussed a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach, named Active Compensation of Aperture Discontinuities (ACAD) relies on two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum. In particular we showed that broadband high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies for a variety of telescope pupil geometries. In this paper we first focus on the fundamental limits and practical trade-offs associated with ACAD. In a first part we will study the fundamental limits and practical tradeoffs associated with ACAD, regardless of the downstream coronagraphic architecture. The mathematical techniques to finding ACAD DM shapes require to solve a complex differential equation. We will first discuss the scaling laws underlying this non-linear solution and their impact of DM placement and geometry wishing the optical design of an instrument. We will then consider the sensitivity to low order aberrations: in principle an ACAD solution that comprises large strokes will be more sensitive to these aberrations than one with smaller strokes. As a consequence, we will quantify this sensitive both using analytical models and numerical simulations. We will present diffractive end to end simulations and quantify the ultimate contrast and bandwidth achievable with ACAD, which can be reached by superposing using a classical linear wavefront control algorithms on top of the Monge Ampere solution. Finally, recent work has shown that coronagraph designs can also accommodate for secondary support structures and/or segments gaps, at a

  7. High-angle triple-axis specimen holder for three-dimensional diffraction contrast imaging in transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hata, S., E-mail: hata.satoshi.207@m.kyushu-u.ac.jp [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Miyazaki, H. [Mel-Build, Nishi-ku, Fukuoka 819-0052 (Japan); Miyazaki, S. [FEI Company Japan Ltd., Minato-ku, Tokyo 108-0075 (Japan); Mitsuhara, M. [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Tanaka, M.; Kaneko, K.; Higashida, K. [Department of Materials Science and Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan); Ikeda, K.; Nakashima, H. [Department of Electrical and Materials Science, Kyushu University, Kasuga, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Matsumura, S. [Department of Applied Physics and Nuclear Engineering, Kyushu University, Nishi-ku, Fukuoka 819-0395 (Japan); Barnard, J.S. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Sharp, J.H. [Department of Materials Science and Engineering, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD (United Kingdom); Midgley, P.A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2011-07-15

    Electron tomography requires a wide angular range of specimen-tilt for a reliable three-dimensional (3D) reconstruction. Although specimen holders are commercially available for tomography, they have several limitations, including tilting capability in only one or two axes at most, e.g. tilt-rotate. For amorphous specimens, the image contrast depends on mass and thickness only and the single-tilt holder is adequate for most tomographic image acquisitions. On the other hand, for crystalline materials where image contrast is strongly dependent on diffraction conditions, current commercially available tomography holders are inadequate, because they lack tilt capability in all three orthogonal axes needed to maintain a constant diffraction condition over the whole tilt range. We have developed a high-angle triple-axis (HATA) tomography specimen holder capable of high-angle tilting for the primary horizontal axis with tilting capability in the other (orthogonal) horizontal and vertical axes. This allows the user to trim the specimen tilt to obtain the desired diffraction condition over the whole tilt range of the tomography series. To demonstrate its capabilities, we have used this triple-axis tomography holder with a dual-axis tilt series (the specimen was rotated by 90{sup o} ex-situ between series) to obtain tomographic reconstructions of dislocation arrangements in plastically deformed austenitic steel foils. -- Highlights: {yields} A double tilt-rotate specimen holder for diffraction contrast imaging in electron tomography. {yields} Precise alignment of a diffraction condition for tilt-series acquisition of TEM/STEM images. {yields} Complete visualization of 3D dislocation arrangements by dual-axis STEM tomography.

  8. Objective climate classification as a framework for assessing projected climate change in High Mountain Asia

    Science.gov (United States)

    Forsythe, Nathan; Fowler, Hayley; Pritchard, David; Blenkinsop, Stephen

    2016-04-01

    This study builds upon foundational work by Forsythe et al (2015, doi: 10.5194/esd-6-311-2015) which used principal component analysis (PCA) and k-means clustering to derive objective present climate classifications over High Mountain Asia and adjacent regions (60E to 100E, 20N to 40N) based on global meteorological reanalyses' estimates of the drivers of water resources availability and variability (precipitation, surface shortwave radiation, daily mean near surface air temperature and its diurnal range). This study refines Forsythe et al (2015) by testing the potential for spatially disaggregating coarse global reanalyses (and climate model outputs) using iterative classification and regression processing to achieve a 5km (0.05 decimal degree) horizontal resolution in order better capture the severe topographic range and gradients of the HMA domain. This spatial refinement should allow for better intercomparability of resultant classifications derived from datasets with different native resolutions. This intercomparability is critical because the second stage of this assesses climate change projections from a range regional climate model experiments - UK Hadley Centre RQUMP 25km South Asia perturbed physics ensemble, CORDEX South Asia domain and (pending dataset availability) NextData EC-Earth 15km high resolution HMA domain - using derived objective classifications as a framework for aggregation. By establishing sub-regional units of relative homogeneity, the objective classification approach allows twofold assessment of project future climate scenarios, i.e. change can be quantified not only as perturbation of key variables (e.g. precipitation, temperature, etc) but also in terms of the spatial descriptors (areal extent, surface elevation range and mean, latitudinal and longitudinal bounds) of the identified climate zones. It is expected that this novel approach, and in particular the very high target spatial resolution, will yield important insights into the

  9. Sub-GHz-resolution C-band Nyquist-filtering interleaver on a high-index-contrast photonic integrated circuit.

    Science.gov (United States)

    Zhuang, Leimeng; Zhu, Chen; Corcoran, Bill; Burla, Maurizio; Roeloffzen, Chris G H; Leinse, Arne; Schröder, Jochen; Lowery, Arthur J

    2016-03-21

    Modern optical communications rely on high-resolution, high-bandwidth filtering to maximize the data-carrying capacity of fiber-optic networks. Such filtering typically requires high-speed, power-hungry digital processes in the electrical domain. Passive optical filters currently provide high bandwidths with low power consumption, but at the expense of resolution. Here, we present a passive filter chip that functions as an optical Nyquist-filtering interleaver featuring sub-GHz resolution and a near-rectangular passband with 8% roll-off. This performance is highly promising for high-spectral-efficiency Nyquist wavelength division multiplexed (N-WDM) optical super-channels. The chip provides a simple two-ring-resonator-assisted Mach-Zehnder interferometer, which has a sub-cm2 footprint owing to the high-index-contrast Si3N4/SiO2 waveguide, while manifests low wavelength-dependency enabling C-band (> 4 THz) coverage with more than 160 effective free spectral ranges of 25 GHz. This device is anticipated to be a critical building block for spectrally-efficient, chip-scale transceivers and ROADMs for N-WDM super-channels in next-generation optical communication networks.

  10. OBJECTS GROUPING FOR SEGMENTATION OF ROADS NETWORK IN HIGH RESOLUTION IMAGES OF URBAN AREAS

    Directory of Open Access Journals (Sweden)

    M. Maboudi

    2016-06-01

    Full Text Available Updated road databases are required for many purposes such as urban planning, disaster management, car navigation, route planning, traffic management and emergency handling. In the last decade, the improvement in spatial resolution of VHR civilian satellite sensors – as the main source of large scale mapping applications – was so considerable that GSD has become finer than size of common urban objects of interest such as building, trees and road parts. This technological advancement pushed the development of “Object-based Image Analysis (OBIA” as an alternative to pixel-based image analysis methods. Segmentation as one of the main stages of OBIA provides the image objects on which most of the following processes will be applied. Therefore, the success of an OBIA approach is strongly affected by the segmentation quality. In this paper, we propose a purpose-dependent refinement strategy in order to group road segments in urban areas using maximal similarity based region merging. For investigations with the proposed method, we use high resolution images of some urban sites. The promising results suggest that the proposed approach is applicable in grouping of road segments in urban areas.

  11. Characterization of High Proper Motion Objects from the Wide-field Infrared Survey Explorer

    CERN Document Server

    Luhman, K L

    2014-01-01

    We present an analysis of high proper motion objects that we have found in a recent study and in this work with multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE). Using photometry and proper motions from 2MASS and WISE, we have identified the members of this sample that are likely to be late type, nearby, or metal poor. We have performed optical and near-infrared spectroscopy on 41 objects, from which we measure spectral types that range from M4-T2.5. This sample includes 11 blue L dwarfs and five subdwarfs; the latter were also classified as such in the recent study by Kirkpatrick and coworkers. Based on their spectral types and photometry, several of our spectroscopic targets may have distances of <20 pc with the closest at ~12 pc. The tangential velocities implied by the spectrophotometric distances and proper motions indicate that four of the five subdwarfs are probably members of the Galactic halo while several other objects, including the early-T dwarf WISE J210529.08-623558....

  12. Search for ionized jets towards high-mass young stellar objects

    CERN Document Server

    Guzmán, Andrés E; Brooks, Kate J; Voronkov, Maxim A

    2012-01-01

    We are carrying out multi-frequency radio continuum observations, using the Australia Telescope Compact Array, to systematically search for collimated ionized jets towards high-mass young stellar objects (HMYSOs). Here we report observations at 1.4, 2.4, 4.8 and 8.6 GHz, made with angular resolutions of about 7, 4, 2, and 1 arcsec, respectively, towards six objects of a sample of 33 southern HMYSOs thought to be in very early stages of evolution. The objects in the sample were selected from radio and infrared catalogs by having positive radio spectral indices and being luminous (L_bol > 20,000 L_sun), but underluminous in radio emission compared to that expected from its bolometric luminosity. This criteria makes the radio sources good candidates for being ionized jets. As part of this systematic search, two ionized jets have been discovered: one previously published and the other reported here. The rest of the observed candidates correspond to three hypercompact hii regions and two ultracompact hii regions. ...

  13. Characterization of high proper motion objects from the wide-field infrared survey explorer

    Energy Technology Data Exchange (ETDEWEB)

    Luhman, K. L. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Sheppard, Scott S., E-mail: kluhman@astro.psu.edu [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015 (United States)

    2014-06-01

    We present an analysis of high proper motion objects that we have found in a recent study and in this work with multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE). Using photometry and proper motions from the Two Micron All-Sky Survey and WISE, we have identified the members of this sample that are likely to be late-type, nearby, or metal-poor. We have performed optical and near-infrared spectroscopy on 41 objects, from which we measure spectral types that range from M4-T2.5. This sample includes 11 blue L dwarfs and 5 subdwarfs; the latter were also classified as such in the recent study by Kirkpatrick and coworkers. Based on their spectral types and photometry, several of our spectroscopic targets may have distances of <20 pc with the closest at ∼12 pc. The tangential velocities implied by the spectrophotometric distances and proper motions indicate that four of the five subdwarfs are probably members of the Galactic halo while several other objects, including the early-T dwarf WISE J210529.08–623558.7, may belong to the thick disk.

  14. Objects Grouping for Segmentation of Roads Network in High Resolution Images of Urban Areas

    Science.gov (United States)

    Maboudi, M.; Amini, J.; Hahn, M.

    2016-06-01

    Updated road databases are required for many purposes such as urban planning, disaster management, car navigation, route planning, traffic management and emergency handling. In the last decade, the improvement in spatial resolution of VHR civilian satellite sensors - as the main source of large scale mapping applications - was so considerable that GSD has become finer than size of common urban objects of interest such as building, trees and road parts. This technological advancement pushed the development of "Object-based Image Analysis (OBIA)" as an alternative to pixel-based image analysis methods. Segmentation as one of the main stages of OBIA provides the image objects on which most of the following processes will be applied. Therefore, the success of an OBIA approach is strongly affected by the segmentation quality. In this paper, we propose a purpose-dependent refinement strategy in order to group road segments in urban areas using maximal similarity based region merging. For investigations with the proposed method, we use high resolution images of some urban sites. The promising results suggest that the proposed approach is applicable in grouping of road segments in urban areas.

  15. Three-photon luminescence of gold nanorods and its applications for high contrast tissue and deep in vivo brain imaging.

    Science.gov (United States)

    Wang, Shaowei; Xi, Wang; Cai, Fuhong; Zhao, Xinyuan; Xu, Zhengping; Qian, Jun; He, Sailing

    2015-01-01

    Gold nanoparticles can be used as contrast agents for bio-imaging applications. Here we studied multi-photon luminescence (MPL) of gold nanorods (GNRs), under the excitation of femtosecond (fs) lasers. GNRs functionalized with polyethylene glycol (PEG) molecules have high chemical and optical stability, and can be used as multi-photon luminescent nanoprobes for deep in vivo imaging of live animals. We have found that the depth of in vivo imaging is dependent upon the transmission and focal capability of the excitation light interacting with the GNRs. Our study focused on the comparison of MPL from GNRs with two different aspect ratios, as well as their ex vivo and in vivo imaging effects under 760 nm and 1000 nm excitation, respectively. Both of these wavelengths were located at an optically transparent window of biological tissue (700-1000 nm). PEGylated GNRs, which were intravenously injected into mice via the tail vein and accumulated in major organs and tumor tissue, showed high image contrast due to distinct three-photon luminescence (3PL) signals upon irradiation of a 1000 nm fs laser. Concerning in vivo mouse brain imaging, the 3PL imaging depth of GNRs under 1000 nm fs excitation could reach 600 μm, which was approximately 170 μm deeper than the two-photon luminescence (2PL) imaging depth of GNRs with a fs excitation of 760 nm.

  16. Observers' Judgments of the Effects of Glare on Their Visual Acuity for High and Low Contrast Stimuli.

    Science.gov (United States)

    Sewall, Ashley A Stafford; Borzendowski, Stephanie A Whetsel; Tyrrell, Richard A; Stephens, Benjamin R; Rosopa, Patrick J

    2016-07-01

    Disability glare refers to a reduction in the ability to discern a stimulus that is positioned near another stimulus that has a much higher luminance. While it is common for drivers to report that they have been "blinded" by oncoming headlights, it is unclear whether observers can accurately judge when they are visually disabled by glare. This experiment sought to quantify the accuracy with which observers can judge when a glare source reduces their visual acuity. Seventeen observers estimated their disability glare threshold (DGT)-the luminance of a glare source that would be just sufficient to impair their ability to discern the orientation of a Landolt C that was surrounded by the glare source. These estimated DGTs were compared to the participant's actual DGTs. Participants consistently underestimated the intensity of glare that was required to impair their acuity. On average, estimates of glare threshold were 88% lower than actual glare threshold intensities. Participants' judgments were affected by stimulus size but not stimulus contrast. These results suggest that observers can exaggerate the debilitating effects of glare and that they can fail to appreciate that high contrast stimuli are more robust to glare. A driver who believes that even the lowest intensities of headlight glare can visually impair an oncoming driver may be reluctant to use high beam headlamps, despite their significant visibility advantages.

  17. Robust high-contrast companion detection from interferometric observations. The CANDID algorithm and an application to six binary Cepheids

    CERN Document Server

    Gallenne, A; Kervella, P; Monnier, J D; Schaefer, G H; Baron, F; Breitfelder, J; Bouquin, J B Le; Roettenbacher, R M; Gieren, W; Pietrzynski, G; McAlister, H; Brummelaar, T ten; Sturmann, J; Sturmann, L; Turner, N; Ridgway, S; Kraus, S

    2015-01-01

    Long-baseline interferometry is an important technique to spatially resolve binary or multiple systems in close orbits. By combining several telescopes together and spectrally dispersing the light, it is possible to detect faint components around bright stars. Aims. We provide a rigorous and detailed method to search for high-contrast companions around stars, determine the detection level, and estimate the dynamic range from interferometric observations. We developed the code CANDID (Companion Analysis and Non-Detection in Interferometric Data), a set of Python tools that allows us to search systematically for point-source, high-contrast companions and estimate the detection limit. The search pro- cedure is made on a N x N grid of fit, whose minimum needed resolution is estimated a posteriori. It includes a tool to estimate the detection level of the companion in the number of sigmas. The code CANDID also incorporates a robust method to set a 3{\\sigma} detection limit on the flux ratio, which is based on an a...

  18. HIGHLY IMPORTANT OBJECTIVES FOR INNOVATION IN ROMANIA WITHIN THE EUROPEAN CONTEXT

    Directory of Open Access Journals (Sweden)

    Popa Ion

    2013-07-01

    Full Text Available Romania, as a country with a low R&D level, in order to converge to the living standards of western economies, is doomed to foster private investments in applied research and experimental development. Thus, it is critical to study what are the main objectives for innovation at organizational level. This paper investigates the most important objectives for innovation in Romania and in the European Union, aiming to find out what are the main challenges innovative enterprises have to face. The general approach is focused on the analysis of the frequency with which these objectives occur, both at general and structural levels. Therefore we have extracted the most important three highly important objectives for innovation, both in Romania and EU: improving the quality of goods or services, the need to increase the range of goods or services and the entering new markets or increase the market share. All these three are positively correlated with the size (number of employees of the organization. One of our findings underlines that there are fewer objectives in EU then in Romania, both at general and structural levels. Such a situation suggesting that the differences derive from two main sources: Romania has more needs, thus the enterprises target more goals, and there is a lack of managerial know-how that leads to non-prioritized objectives for innovation. Also, we identified an asymmetry, consisting in the fact that in EU, medium sized enterprises are more likely to act as the small ones, as opposed to the Romanian context. R&D and innovation component should be in the center of the Romanian strategy for convergence and competitiveness strengthening, treating differently the SMEs in order to foster innovation in a sustainable manner, through the encouragement of private enterprises to engage in partnerships for R&D an innovation. Also there is a critical need for governmental intervention in building facilities for the modern business infrastructures

  19. AIUB Efforts to Survey, Track, and Characterize Small-Size Objects at High Altitudes

    Science.gov (United States)

    Schildknecht, T.; Früh, C.; Herzog, J.; Hinze, A.; Vananti, A.

    2010-09-01

    Since more than a decade the Astronomical Institute of the University of Bern (AIUB) is investigating the small-size space debris environment in high-altitude orbit regions. Originally the efforts concentrated on statistical optical surveys with the primary goal to derive fluxes as input data for statistical environment models. It became, however, obvious that important characteristics of the debris population could not be determined by this technique. The sparse surveys did not yield orbital elements for the debris objects, and it was very difficult to assess the total number of objects for a given region. One essential task of the space debris research is to find and understand the sources of debris, which in turn will enable to devise efficient mitigation measures - a prerequisite for the sustainable use of outer space. In order to understand the nature and eventually the origin of small-size debris objects, observations allowing to derive orbital parameters and physical characteristics like size, shape and material are required. This paper discusses the AIUB activities to build-up and maintain an orbit catalogue of small-size debris. AIUB uses its dedicated 0.3m robotic telescope ZimSMART-2 to constantly survey the GEO, the GTO and the MEO region. The data from this telescope is fused with observations from AIUB's 1-meter ZIMLAT telescope and ESA's 1-meter telescope in Tenerife and shared with international partners. The resulting catalogue of orbital elements enables physical characterization of the debris objects trough photometry, light curve and reflectance spectroscopy observations.

  20. Sheet-like and plume-like thermal flow in a spherical convection experiment with high viscosity contrast.

    Science.gov (United States)

    Futterer, Birgit; Zaussinger, Florian; Plesa, Ana-Catalina; Krebs, Andreas; Egbers, Christoph; Breuer, Doris

    2013-04-01

    We introduce our spherical experiments on electro-hydrodynamical driven Rayleigh-Bénard convection that have been performed either with temperature-independent properties of the fluid, called 'GeoFlow I', or with temperature-dependent properties, called 'GeoFlow II'. To set up a self-gravitating force field with radial directed buoyancy, we use a high voltage potential between the inner and outer boundaries and a dielectric insulating liquid and perform the experiment in the microgravity conditions of the ISS [1, 2]. We further run numerical simulations in a 3D spherical geometry to reproduce the results obtained in the GeoFlow experiments. In the experiment the used optical method for flow visualization as delivered by the Optical Diagnostics Module ODM of the Fluid Science Laboratory, is the so called Wollaston-Prism shearing interferometry WSI, which produces fringe pattern images. For the numerical simulations we compute from the temperature field a fringe pattern of convection to compare it then to the experiment data. In this work, we present the flow imaging techniques and their numerical analogues, which were used to compare experimental results with numerical solutions. An important finding is the difference in the flow pattern between our two experiments. We see a sheet-like thermal flow, if the physical properties of the fluid are not varying with temperature - a result from 'GeoFlow I'. In this case the convection patterns have been successfully reproduced by 3D numerical simulations using both the RESPECT [3] and GAIA [4] codes. If we use a liquid with varying (electro-hydrodynamic) volume expansion and temperature-dependent viscosity (GeoFlow II), for which the viscosity contrast measured in the experiment is 2, the structures change significantly and are plume-like. This result is not expected, since the viscosity contrast seems to be too small for this type of solution according to numerical simulations. However, using a viscosity contrast of two

  1. Design of LCPG-type polarization-independent shutter with diffractive efficiency and high contrast at wavelength 532 nm

    Science.gov (United States)

    Kavosh Tehrani, Masoud; Sajad Mousavi Fard, Sayed

    2017-02-01

    We have designed liquid crystal (LC) shutter of LCPG type with high diffractive efficiency and transmission rate of more than 99.747% for modulation of non-polar light with wavelength 532 nm and high contrast in this article. Compared to other similar cases, the advantages of this design include maximization of transmission percent of diffractive element (particularly first-order diffraction) and minimization of light leakage rate caused by zero-order, and other unwanted diffractive orders. The conditions have been prepared for using diffractive elements (gratings) with shorter periods and acquisition of diffraction orders with greater diffraction angles by benefitting from suitable compounds of LC in the given design. Similarly, required measures have been taken for the deletion of adverse effects caused by reflection from optic surfaces so that very appropriate status is prepared for the function of LCPG shutter.

  2. A method for high-energy, low-dose mammography using edge illumination x-ray phase-contrast imaging

    Science.gov (United States)

    Diemoz, Paul C.; Bravin, Alberto; Sztrókay-Gaul, Anikó; Ruat, Marie; Grandl, Susanne; Mayr, Doris; Auweter, Sigrid; Mittone, Alberto; Brun, Emmanuel; Ponchut, Cyril; Reiser, Maximilian F.; Coan, Paola; Olivo, Alessandro

    2016-12-01

    Since the breast is one of the most radiosensitive organs, mammography is arguably the area where lowering radiation dose is of the uttermost importance. Phase-based x-ray imaging methods can provide opportunities in this sense, since they do not require x-rays to be stopped in tissue for image contrast to be generated. Therefore, x-ray energy can be considerably increased compared to those usually exploited by conventional mammography. In this article we show how a novel, optimized approach can lead to considerable dose reductions. This was achieved by matching the edge-illumination phase method, which reaches very high angular sensitivity also at high x-ray energies, to an appropriate image processing algorithm and to a virtually noise-free detection technology capable of reaching almost 100% efficiency at the same energies. Importantly, while proof-of-concept was obtained at a synchrotron, the method has potential for a translation to conventional sources.

  3. Slit-scanning microscope with a high-NA objective lens for analysis of synaptic function

    Science.gov (United States)

    Sakurai, Takashi; Wakazono, Yoshihiko; Yamamoto, Seiji; Terakawa, Susumu

    2004-07-01

    By employing the total internal reflection fluorescence (TIRF) microscope with an ultra high NA (1.65) objective lens, we demonstrated detailed dynamics of exocytosis in various types of secretory vesicles. However, the TIRF microscopy could be applied to observations only on the plasma membrane and its immediate vicinity. To observe the vesicles in the deeper region of cytoplasm, we modified the TIRF optics to project a slit beam thinner than 1 μm in width to the cell. The slit beam illumination spotted single secretory vesicles inside the cell better and their movement and exocytosis easier. By scanning the slit beam, a fluorescence microscopy was possible at a high signal-to-noise ratio useful for measurement and analysis of single exocytosis in neurons and endocrine cells.

  4. Generation of Highly Inclined Trans-Neptunian Objects by Planet Nine

    CERN Document Server

    Batygin, Konstantin

    2016-01-01

    The trans-Neptunian region of the solar system exhibits an intricate dynamical structure, much of which can be explained by an instability-driven orbital history of the giant planets. However, the origins of a highly inclined, and in certain cases retrograde, population of trans-Neptunian objects remain elusive within the framework of this evolutionary picture. In this work, we show that the existence of a distant, Neptune-like planet that resides on an eccentric and mildly inclined orbit fully accounts for the anomalous component the trans-Neptunian orbital distribution. Adopting the same parameters for Planet Nine as those previously invoked to explain the clustering of distant Kuiper belt orbits in physical space, we carry out a series of numerical experiments which elucidate the physical process though which highly inclined Kuiper belt objects with semi-major axes smaller than 100 AU are generated. The identified dynamical pathway demonstrates that enigmatic members of the Kuiper belt such as Drac and Nik...

  5. A laboratory measurement method for pressure sensitive adhesives in agglomeration deinking of mixed office waste paper: The high-low scanning contrast method

    Directory of Open Access Journals (Sweden)

    Guolin Tong

    2012-11-01

    Full Text Available A simple measurement method for pressure sensitive adhesives (PSA in an agglomeration deinking system of mixed office waste paper was studied. This method was based on the different scanning performance of ink and PSA specks in hot-pressed and oven-dried handsheets with the change of contrast values that had been selected and set in the image analysis software. The numbers of ink specks per square meter (NPM were well recognized at both low and high contrast values and exhibited a very good linear relationship within a range of contrast values. The PSA specks, on the other hand, could not be recognized at the low contrast values and could only be recognized at high contrast values. The NPM value of the ink specks was found to have the highest values at the high contrast values and could be accurately predicted by its NPM value at the low contrast values. Thus, the NPM value of the PSA specks could be easily calculated by the total NPM of the handsheet at the high contrast value minus the projected NPM of the ink specks from its low contrast conditions. Compared to the dye method, which was also used on the measurement of microstickies, this method is suggested as a simple and quick laboratory tool to measure the relative quantity of PSA in the mixed office waste paper with minimum interference from the residual toner ink.

  6. Atmospheric characterization of Proxima b by coupling the SPHERE high-contrast imager to the ESPRESSO spectrograph

    Science.gov (United States)

    Lovis, C.; Snellen, I.; Mouillet, D.; Pepe, F.; Wildi, F.; Astudillo-Defru, N.; Beuzit, J.-L.; Bonfils, X.; Cheetham, A.; Conod, U.; Delfosse, X.; Ehrenreich, D.; Figueira, P.; Forveille, T.; Martins, J. H. C.; Quanz, S. P.; Santos, N. C.; Schmid, H.-M.; Ségransan, D.; Udry, S.

    2017-02-01

    Context. The temperate Earth-mass planet Proxima b is the closest exoplanet to Earth and represents what may be our best ever opportunity to search for life outside the Solar System. Aims: We aim at directly detecting Proxima b and characterizing its atmosphere by spatially resolving the planet and obtaining high-resolution reflected-light spectra. Methods: We propose to develop a coupling interface between the SPHERE high-contrast imager and the new ESPRESSO spectrograph, both installed at ESO VLT. The angular separation of 37 mas between Proxima b and its host star requires the use of visible wavelengths to spatially resolve the planet on a 8.2-m telescope. At an estimated planet-to-star contrast of 10-7 in reflected light, Proxima b is extremely challenging to detect with SPHERE alone. However, the combination of a 103-104 contrast enhancement from SPHERE to the high spectral resolution of ESPRESSO can reveal the planetary spectral features and disentangle them from the stellar ones. Results: We find that significant but realistic upgrades to SPHERE and ESPRESSO would enable a 5σ detection of the planet and yield a measurement of its true mass and albedo in 20-40 nights of telescope time, assuming an Earth-like atmospheric composition. Moreover, it will be possible to probe the O2 bands at 627, 686 and 760 nm, the water vapour band at 717 nm, and the methane band at 715 nm. In particular, a 3.6σ detection of O2 could be made in about 60 nights of telescope time. Those would need to be spread over three years considering optimal observability conditions for the planet. Conclusions: The very existence of Proxima b and the SPHERE-ESPRESSO synergy represent a unique opportunity to detect biosignatures on an exoplanet in the near future. It is also a crucial pathfinder experiment for the development of extremely large telescopes and their instruments, in particular the E-ELT and its high-resolution visible and near-IR spectrograph.

  7. High-Density Three-Dimension Graphene Macroscopic Objects for High-Capacity Removal of Heavy Metal Ions

    Science.gov (United States)

    Li, Weiwei; Gao, Song; Wu, Liqiong; Qiu, Shengqiang; Guo, Yufen; Geng, Xiumei; Chen, Mingliang; Liao, Shutian; Zhu, Chao; Gong, Youpin; Long, Mingsheng; Xu, Jianbao; Wei, Xiangfei; Sun, Mengtao; Liu, Liwei

    2013-01-01

    The chemical vapor deposition (CVD) fabrication of high-density three-dimension graphene macroscopic objects (3D-GMOs) with a relatively low porosity has not yet been realized, although they are desirable for applications in which high mechanical and electrical properties are required. Here, we explore a method to rapidly prepare the high-density 3D-GMOs using nickel chloride hexahydrate (NiCl2·6H2O) as a catalyst precursor by CVD process at atmospheric pressure. Further, the free-standing 3D-GMOs are employed as electrolytic electrodes to remove various heavy metal ions. The robust 3D structure, high conductivity (~12 S/cm) and large specific surface area (~560 m2/g) enable ultra-high electrical adsorption capacities (Cd2+ ~ 434 mg/g, Pb2+ ~ 882 mg/g, Ni2+ ~ 1,683 mg/g, Cu2+ ~ 3,820 mg/g) from aqueous solutions and fast desorption. The current work has significance in the studies of both the fabrication of high-density 3D-GMOs and the removal of heavy metal ions. PMID:23821107

  8. In an animal model nephrogenic systemic fibrosis cannot be induced by intraperitoneal injection of high-dose gadolinium based contrast agents

    Energy Technology Data Exchange (ETDEWEB)

    Langer, R.D., E-mail: rlanger@uaeu.ac.ae [Faculty of Medicine and Health Sciences (FMHS), United Arab Emirates University, Al Ain (United Arab Emirates); Lorke, D.E. [Florida International University, Miami, FL (United States); Neidl van Gorkom, K.F. [Faculty of Medicine and Health Sciences (FMHS), United Arab Emirates University, Al Ain (United Arab Emirates); Petroianu, G. [Florida International University, Miami, FL (United States); Azimullah, S.; Nurulain, S.M.; Singh, S. [Faculty of Medicine and Health Sciences (FMHS), United Arab Emirates University, Al Ain (United Arab Emirates); Fuchsjäger, M. [Al Ain Hospital, MUV-VAMED, Al Ain (United Arab Emirates)

    2012-10-15

    Aim and objective: Nephrogenic systemic fibrosis (NSF) has been reported in humans to be most likely induced by gadolinium based contrast agents (GBCA), namely by gadodiamide, gadopentetate dimeglumine, and gadoversetamide, rarely by other GBCA. The pathogenesis of NSF remains unclear; different hypotheses are under discussion. The objective of the study is to assess if in the animal model human-like NSF changes can be induced by high-dose, intraperitoneal GBCA injections over four weeks. Materials and methods: After approval by the institutional animal ethics committee, six rats each were randomly assigned to groups, and treated with seven different GBCA. Intraperitoneal (IP) injections – proven in the animal model to be effective – were chosen to prolong the animals’ exposure to the respective GBCA. GBCA doses of previous intravenous (IV) animal studies were applied. After five weeks all rats were sacrificed. Sham controls were treated with IP saline injections, employing the same regimen. Results: No findings comparable with human NSF were observed in all animals after IP treatment with all seven GBCA at daily doses of 2.5 and 5.0 mmol/kg body weight (BW). No histopathological abnormalities of all examined organs were noted. Weight loss was stated in weeks three and four with GBCA injections at doses of 5.0 mmol/kg BW, but rats regained weight after cessation of GBCA treatment. Conclusions: NSF-comparable pathological findings could not be induced by high dose intraperitoneal injection of seven GBCA.

  9. High-contrast imager for complex aperture telescopes (HiCAT): 3. first lab results with wavefront control

    Science.gov (United States)

    N'Diaye, Mamadou; Mazoyer, Johan; Choquet, Élodie; Pueyo, Laurent; Perrin, Marshall D.; Egron, Sylvain; Leboulleux, Lucie; Levecq, Olivier; Carlotti, Alexis; Long, Chris A.; Lajoie, Rachel; Soummer, Rémi

    2015-09-01

    HiCAT is a high-contrast imaging testbed designed to provide complete solutions in wavefront sensing, control and starlight suppression with complex aperture telescopes. The pupil geometry of such observatories includes primary mirror segmentation, central obstruction, and spider vanes, which make the direct imaging of habitable worlds very challenging. The testbed alignment was completed in the summer of 2014, exceeding specifications with a total wavefront error of 12nm rms over a 18mm pupil. The installation of two deformable mirrors for wavefront control is to be completed in the winter of 2015. In this communication, we report on the first testbed results using a classical Lyot coronagraph. We also present the coronagraph design for HiCAT geometry, based on our recent development of Apodized Pupil Lyot Coronagraph (APLC) with shaped-pupil type optimizations. These new APLC-type solutions using two-dimensional shaped-pupil apodizer render the system quasi-insensitive to jitter and low-order aberrations, while improving the performance in terms of inner working angle, bandpass and contrast over a classical APLC.

  10. Digital adaptive coronagraphy using SLMs: promising prospects of a novel approach, including high-contrast imaging of multiple stars systems

    Science.gov (United States)

    Kühn, Jonas; Patapis, Polychronis

    2016-07-01

    We introduce a new technological framework for high-contrast coronagraphy, namely digital adaptive coronagraphy (DAC) using spatial light modulators (SLMs), taking advantage of recent advances in this technology. We present proof-of-principle experimental results in the visible, using a transmissive twisted nematic liquid crystal SLM display to show that SLMs can be successfully implemented as focal-plane phase-mask coronagraphs (4QPM, 8OPM,...), and that the technology is essentially in place to address realistic instrumental configurations. We explore a specific application where SLM-based adaptive coronagraphy might be particularly competitive, which is direct imaging of multiple stars systems, by simultaneously nulling multiple point sources in the field. Using a simple approach to compute a brightness-weighted synthetized coronagraphic phase map, we show that in the case of binaries the contrast gain over using a regular phase map can exceed 4 stellar magnitudes for a 1:1 binaries down to separation as close as 1 λ/D. Thanks to video-rate update frequency of the SLM, the technique is in principle compatible with sky rotation in the case of altitude-azimuth telescope mounts, and can address multiple target configurations with no actual mechanical or hardware change.

  11. Contrast sensitivity test and conventional and high frequency audiometry: information beyond that required to prescribe lenses and headsets

    Science.gov (United States)

    Comastri, S. A.; Martin, G.; Simon, J. M.; Angarano, C.; Dominguez, S.; Luzzi, F.; Lanusse, M.; Ranieri, M. V.; Boccio, C. M.

    2008-04-01

    In Optometry and in Audiology, the routine tests to prescribe correction lenses and headsets are respectively the visual acuity test (the first chart with letters was developed by Snellen in 1862) and conventional pure tone audiometry (the first audiometer with electrical current was devised by Hartmann in 1878). At present there are psychophysical non invasive tests that, besides evaluating visual and auditory performance globally and even in cases catalogued as normal according to routine tests, supply early information regarding diseases such as diabetes, hypertension, renal failure, cardiovascular problems, etc. Concerning Optometry, one of these tests is the achromatic luminance contrast sensitivity test (introduced by Schade in 1956). Concerning Audiol