WorldWideScience

Sample records for high contrast ratios

  1. 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)

  2. 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

  3. Dual energy contrast enhanced breast imaging optimization using contrast to noise ratio

    Science.gov (United States)

    Arvanitis, C. D.; Royle, G.; Speller, R.

    2007-03-01

    The properties of dual energy contrast enhanced breast imaging have been analyzed by imaging a 4 cm breast equivalent phantom consisting of adipose and glandular equivalent plastics. This phantom had superimposed another thin plastic which incorporated a 2 mm deep cylinder filled with iodinated contrast media. The iodine projected thicknesses used for this study was 3 mg/cm2. Low and high energy spectra that straddle the iodine K-edge were used. Critical parameters such as the energy spectra and exposure are discussed, along with post processing by means of nonlinear energy dependent function. The dual energy image was evaluated using the relative contrast to noise ratio of a 2.5 mm x 2.5 mm region of the image at the different iodine concentrations incorporating different breast composition with respect to the noniodinated areas. Optimum results were achieved when the low and high-energy images were used in such a way that relative contrast to noise ratio of the iodine with respect to the background tissue was maximum. A figure of merit suggests that higher noise levels can be tolerated at the benefit of lower exposure. Contrast media kinetics of a phantom incorporating a water flow of 20.4 ml/min through the plastic cylinder suggests that time domain imaging could be performed with this approach. The results suggest that optimization of dual energy contrast enhanced mammography has the potential to lead to the development of perfusion digital mammography.

  4. K(alpha) x-ray emission characterization of 100 Hz, 15 mJ femtosecond laser system with high contrast ratio.

    Science.gov (United States)

    Fourmaux, S; Serbanescu, C; Kincaid, R E; Krol, A; Kieffer, J C

    2008-12-12

    We report K(alpha) x-ray production with a high energy (110 mJ per pulse at 800 nm before compression/15 mJ at 400 nm after compression), high repetition rate (100 Hz), and high pulse contrast (better than 10(-9) at 400 nm) laser system. To develop laser-based x-ray sources for biomedical imaging requires to use high-energy and high-power ultra-fast laser system where compression is achieved under vacuum. Using this type of laser system, we demonstrate long-term stability of the x-ray yield, conversion efficiency higher than 1.5 x 10(-5) with a Mo target, and the x-ray spot size close to the optical focal spot. This high-repetition K(alpha) x-ray source can be very useful for x-ray phase-contrast imaging.

  5. The contrasting effects of ad libitum and restricted feeding of a diet very high in saturated fats on sex ratio and metabolic hormones in mice.

    Science.gov (United States)

    Alexenko, Andrei P; Mao, Jiude; Ellersieck, Mark R; Davis, Angela M; Whyte, Jeffrey J; Rosenfeld, Cheryl S; Roberts, R Michael

    2007-10-01

    Skewing of the sex ratio towards males occurs among pups born to mice fed a very high saturated fat (VHF) diet. In the present study, we tested whether the fat content of the VHF diet rather than the number of calories consumed is responsible for this effect. Eight-week-old NIH Swiss mice were placed on the VHF diet either ad libitum (VHF) or in a restricted manner (VHF-R). The VHF-R mice gained weight at a similar rate to controls fed a standard chow diet. Mice were bred at 15 wk and subsequently at 26 wk and 35 wk of age. Overall, the VHF, VHF-R, and control groups delivered 244, 242, and 274 pups, respectively, with male proportions of 0.60, 0.43, and 0.48, respectively. The pup sex ratios of the VHF group (favoring males) and VHF-R group (favoring females) each differed from 0.5 (P fat consumed. Since males fed the VHF diet had neither more Y-sperm nor sired more sons than daughters, the dietary effects are manifested exclusively through the female.

  6. Fungal/bacterial ratios in grassland with contrasting nitrogen management

    NARCIS (Netherlands)

    Vries, de F.T.; Hoffland, E.; Eekeren, van N.J.M.; Brussaard, L.; Bloem, J.

    2006-01-01

    It is frequently hypothesised that high soil fungal/bacterial ratios are indicative for more sustainable agricultural systems. Increased F / B ratios have been reported in extensively managed grasslands. To determine the shifts in fungal/bacterial biomass ratio as influenced by grassland management

  7. Contrast-to-noise ratio optimization for a prototype phase-contrast computed tomography scanner

    Energy Technology Data Exchange (ETDEWEB)

    Müller, Mark, E-mail: mark-mueller@ph.tum.de; Yaroshenko, Andre; Velroyen, Astrid; Tapfer, Arne [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Bech, Martin [Medical Radiation Physics, Lund University, Barngatan 2:1, 221 85 Lund (Sweden); Pauwels, Bart; Bruyndonckx, Peter; Sasov, Alexander [Bruker microCT, Kartuizersweg 3B, B-2550 Kontich (Belgium); Pfeiffer, Franz [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Institut für diagnostische und interventionelle Radiologie, Klinikum rechts der Isar, Technische Universität München, 81675 München (Germany); Institute for Advanced Study, Technische Universität München, 85748 Garching (Germany)

    2015-12-15

    In the field of biomedical X-ray imaging, novel techniques, such as phase-contrast and dark-field imaging, have the potential to enhance the contrast and provide complementary structural information about a specimen. In this paper, a first prototype of a preclinical X-ray phase-contrast CT scanner based on a Talbot-Lau interferometer is characterized. We present a study of the contrast-to-noise ratios for attenuation and phase-contrast images acquired with the prototype scanner. The shown results are based on a series of projection images and tomographic data sets of a plastic phantom in phase and attenuation-contrast recorded with varying acquisition settings. Subsequently, the signal and noise distribution of different regions in the phantom were determined. We present a novel method for estimation of contrast-to-noise ratios for projection images based on the cylindrical geometry of the phantom. Analytical functions, representing the expected signal in phase and attenuation-contrast for a circular object, are fitted to individual line profiles of the projection data. The free parameter of the fit function is used to estimate the contrast and the goodness of the fit is determined to assess the noise in the respective signal. The results depict the dependence of the contrast-to-noise ratios on the applied source voltages, the number of steps of the phase stepping routine, and the exposure times for an individual step. Moreover, the influence of the number of projection angles on the image quality of CT slices is investigated. Finally, the implications for future imaging purposes with the scanner are discussed.

  8. Contrast-to-noise ratio optimization for a prototype phase-contrast computed tomography scanner.

    Science.gov (United States)

    Müller, Mark; Yaroshenko, Andre; Velroyen, Astrid; Bech, Martin; Tapfer, Arne; Pauwels, Bart; Bruyndonckx, Peter; Sasov, Alexander; Pfeiffer, Franz

    2015-12-01

    In the field of biomedical X-ray imaging, novel techniques, such as phase-contrast and dark-field imaging, have the potential to enhance the contrast and provide complementary structural information about a specimen. In this paper, a first prototype of a preclinical X-ray phase-contrast CT scanner based on a Talbot-Lau interferometer is characterized. We present a study of the contrast-to-noise ratios for attenuation and phase-contrast images acquired with the prototype scanner. The shown results are based on a series of projection images and tomographic data sets of a plastic phantom in phase and attenuation-contrast recorded with varying acquisition settings. Subsequently, the signal and noise distribution of different regions in the phantom were determined. We present a novel method for estimation of contrast-to-noise ratios for projection images based on the cylindrical geometry of the phantom. Analytical functions, representing the expected signal in phase and attenuation-contrast for a circular object, are fitted to individual line profiles of the projection data. The free parameter of the fit function is used to estimate the contrast and the goodness of the fit is determined to assess the noise in the respective signal. The results depict the dependence of the contrast-to-noise ratios on the applied source voltages, the number of steps of the phase stepping routine, and the exposure times for an individual step. Moreover, the influence of the number of projection angles on the image quality of CT slices is investigated. Finally, the implications for future imaging purposes with the scanner are discussed.

  9. Measurement of Contrast Ratios for 3D Display

    Science.gov (United States)

    2000-07-01

    stereoscopic, autostereoscopic , 3D , display ABSTRACT 3D image display devices have wide applications in medical and entertainment areas. Binocular (stereoscopic...and system crosstalk. In many 3D display systems viewer’ crosstalk is an important issue for good performance, especial in autostereoscopic display...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO 11343 TITLE: Measurement of Contrast Ratios for 3D Display

  10. High-Ratio Gear Train

    Science.gov (United States)

    Lefever, A. E.

    1982-01-01

    Proposed arrangement of two connected planetary differentials results in gear ratio many times that obtainable in conventional series gear assembly of comparable size. Ratios of several thousand would present no special problems. Selection of many different ratios is available with substantially similar gear diameters. Very high gear ratios would be obtained from small mechanism.

  11. 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.

  12. Holes at High Blowing Ratios

    Directory of Open Access Journals (Sweden)

    Phillip M. Ligrani

    1996-01-01

    Full Text Available Experimental results are presented which describe the development and structure of flow downstream of a single row of holes with compound angle orientations producing film cooling at high blowing ratios. This film cooling configuration is important because similar arrangements are frequently employed on the first stage of rotating blades of operating gas turbine engines. With this configuration, holes are spaced 6d apart in the spanwise direction, with inclination angles of 24 degrees, and angles of orientation of 50.5 degrees. Blowing ratios range from 1.5 to 4.0 and the ratio of injectant to freestream density is near 1.0. Results show that spanwise averaged adiabatic effectiveness, spanwise-averaged iso-energetic Stanton number ratios, surveys of streamwise mean velocity, and surveys of injectant distributions change by important amounts as the blowing ratio increases. This is due to injectant lift-off from the test surface just downstream of the holes.

  13. Optical design for excellent contrast ratio in a reflective horizontal-switching liquid crystal cell

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyung-Mi; Ji, Seung-Hoon; Lee, Gi-Dong [Department of Electronics Engineering, Dong-A University, Busan 604-714 (Korea, Republic of); Lee, Joun-Ho [LG.Philips LCD, 642-3 Jinpyung-dong, Gumi-city, Kyungbuk 730-350 (Korea, Republic of); Lee, Seung Hee [Research Center for Advanced Materials Development, School of Advanced Materials Engineering, Chonbuk National University, Chonju, Chonbuk 561-756 (Korea, Republic of)], E-mail: gdlee@dau.ac.kr, E-mail: lsh1@chonbuk.ac.kr

    2008-06-07

    In this paper, we propose an optical configuration for a reflective liquid crystal (LC) cell with a single polarizer that can show an excellent contrast ratio by effectively eliminating phase dispersion. The proposed configuration consists of a half-wave retarder, two A-plates, a quarter-wave LC cell and a reflector; the configuration was designed on a Poincare sphere with the trigonometric method. From the calculation, we confirm that this configuration can show a high contrast ratio as compared with the conventional configuration due to the excellent dark state.

  14. Signal-to-noise ratio, contrast-to-noise ratio and pharmacokinetic modeling considerations in dynamic contrast-enhanced magnetic resonance imaging.

    Science.gov (United States)

    Li, Xin; Huang, Wei; Rooney, William D

    2012-11-01

    With advances in magnetic resonance imaging (MRI) technology, dynamic contrast-enhanced (DCE)-MRI is approaching the capability to simultaneously deliver both high spatial and high temporal resolutions for clinical applications. However, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) considerations and their impacts regarding pharmacokinetic modeling of the time-course data continue to represent challenges in the design of DCE-MRI acquisitions. Given that many acquisition parameters can affect the nature of DCE-MRI data, minimizing tissue-specific data acquisition discrepancy (among sites and scanner models) is as important as synchronizing pharmacokinetic modeling approaches. For cancer-related DCE-MRI studies where rapid contrast reagent (CR) extravasation is expected, current DCE-MRI protocols often adopt a three-dimensional fast low-angle shot (FLASH) sequence to achieve spatial-temporal resolution requirements. Based on breast and prostate DCE-MRI data acquired with different FLASH sequence parameters, this paper elucidates a number of SNR and CNR considerations for acquisition optimization and pharmacokinetic modeling implications therein. Simulations based on region of interest data further indicate that the effects of intercompartmental water exchange often play an important role in DCE time-course data modeling, especially for protocols optimized for post-CR SNR.

  15. 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.

  16. 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.

  17. 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

  18. 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...

  19. Practical method and device for enhancing pulse contrast ratio for lasers and electron accelerators

    Science.gov (United States)

    Zhang, Shukui; Wilson, Guy

    2014-09-23

    An apparatus and method for enhancing pulse contrast ratios for drive lasers and electron accelerators. The invention comprises a mechanical dual-shutter system wherein the shutters are placed sequentially in series in a laser beam path. Each shutter of the dual shutter system has an individually operated trigger for opening and closing the shutter. As the triggers are operated individually, the delay between opening and closing first shutter and opening and closing the second shutter is variable providing for variable differential time windows and enhancement of pulse contrast ratio.

  20. 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.

  1. Extreme Contrast Ratio Imaging of Sirius with a Charge Injection Device

    CERN Document Server

    Batcheldor, D; Bahr, C; Jenne, J; Ninkov, Z; Bhaskaran, S; Chapman, T

    2015-01-01

    The next fundamental steps forward in understanding our place in the universe could be a result of advances in extreme contrast ratio (ECR) imaging and point spread function (PSF) suppression. For example, blinded by quasar light we have yet to fully understand the processes of galaxy formation and evolution, and there is an ongoing race to obtain a direct image of an exoearth lost in the glare of its host star. To fully explore the features of these systems we must perform observations in which contrast ratios of at least one billion can be regularly achieved with sub 0.1" inner working angles. Here we present the details of a latest generation 32-bit charge injection device (CID) that could conceivably achieve contrast ratios on the order of one billion. We also demonstrate some of its ECR imaging abilities for astronomical imaging. At a separation of two arc minutes, we report a direct contrast ratio of Delta(m_v)=18.3, log(CR)=7.3, or 1 part in 20 million, from observations of the Sirius field. The atmosp...

  2. 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 ...

  3. 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.

  4. Contrast ratio of veneering and core ceramics as a function of thickness.

    Science.gov (United States)

    Antonson, S A; Anusavice, K J

    2001-01-01

    The recent development of several dental ceramic products has raised questions concerning the relative translucency potential of these materials. The objective of this study was to test the hypothesis that the contrast ratio of dental core and veneering ceramics is a linear function of ceramic thickness. Four groups of disk-shaped core ceramic specimens and four groups of veneering ceramic specimens (15 mm in diameter and 0.70, 1.10, 1.25, or 1.50 mm in thickness) were prepared for analysis. Five disks were randomly assigned to each of the eight groups. Four core ceramics were selected for study: (1) tetrasilicic fluormica glass ceramic, (2) quadruple-chain silicate glass ceramic, (3) barium silicate glass ceramic, and (4) sintered alumina. The four veneering ceramics included two feldspathic body porcelains, one fine-grained veneering porcelain, and one ultralow-fusing porcelain. There were significant differences among the mean contrast ratio values of these materials. The most translucent group of the core materials was tetrasilicic fluormica glass ceramic, and the least translucent material was sintered alumina. The most translucent group among the veneering ceramics was one of the feldspathic ceramics (Ceramco), and the least translucent material for all thicknesses was the ultralow-fusing veneering ceramic (Duceram LFC). The mean contrast ratio values were significantly different at a thickness of 1.50 mm of the four core ceramic groups and among the four veneering ceramic groups. The results of this study indicate that the tetrasilicic fluormica glass ceramic is generally the most translucent core ceramic for thicknesses of 0.70, 1.10, and 1.25 mm, and Ceramco porcelain is the most translucent veneering ceramic. However, for a thickness of 1.50 mm, the quadruple-chain silicate glass ceramic was the most translucent core ceramic. The relationship between contrast ratio and thickness was linear for all ceramics except Vita VMK 68.

  5. 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.

  6. Search for novel contrast materials in dual-energy x-ray breast imaging using theoretical modeling of contrast-to-noise ratio.

    Science.gov (United States)

    Karunamuni, R; Maidment, A D A

    2014-08-01

    Contrast-enhanced (CE) dual-energy (DE) x-ray breast imaging uses a low- and high-energy x-ray spectral pair to eliminate soft-tissue signal variation and thereby increase the detectability of exogenous imaging agents. Currently, CEDE breast imaging is performed with iodinated contrast agents. These compounds are limited by several deficiencies, including rapid clearance and poor tumor targeting ability. The purpose of this work is to identify novel contrast materials whose contrast-to-noise ratio (CNR) is comparable or superior to that of iodine in the mammographic energy range. A monoenergetic DE subtraction framework was developed to calculate the DE signal intensity resulting from the logarithmic subtraction of the low- and high-energy signal intensities. A weighting factor is calculated to remove the dependence of the DE signal on the glandularity of the breast tissue. Using the DE signal intensity and weighting factor, the CNR for materials with atomic numbers (Z) ranging from 1 to 79 are computed for energy pairs between 10 and 50 keV. A group of materials with atomic numbers ranging from 42 to 63 were identified to exhibit the highest levels of CNR in the mammographic energy range. Several of these materials have been formulated as nanoparticles for various applications but none, apart from iodine, have been investigated as CEDE breast imaging agents. Within this group of materials, the necessary dose fraction to the LE image decreases as the atomic number increases. By reducing the dose to the LE image, the DE subtraction technique will not provide an anatomical image of sufficient quality to accompany the contrast information. Therefore, materials with Z from 42 to 52 provide nearly optimal values of CNR with energy pairs and dose fractions that provide good anatomical images. This work is intended to inspire further research into new materials for optimized CEDE breast functional imaging.

  7. Optical constants of electrochromic films and contrast ratio of reflective electrochromic devices.

    Science.gov (United States)

    Jaing, Cheng-Chung; Tang, Chien-Jen; Chan, Chih-Chao; Lee, Kun-Hsien; Kuo, Chien-Cheng; Chen, Hsi-Chao; Lee, Cheng-Chung

    2014-02-01

    This study investigates the optical constants of WO3 electrochromic films and NiO ion-storage films in bleached and colored states and that of a Ta2O5 film used as an ion conductor. These thin films were all prepared by electron-beam evaporation and characterized using a spectroscopic ellipsometer. The spectra obtained using a spectrophotometer and those calculated from the optical constants agreed closely. An all-solid thin-film reflective electrochromic device was fabricated and discussed. Its mean contrast ratio of reflectance in the range of 400-700 nm was 37.91.

  8. Modeling the effects of distortion, contrast, and signal-to-noise ratio on stereophotogrammetric range mapping

    Science.gov (United States)

    Sellar, R. Glenn; Deen, Robert G.; Huffman, William C.; Willson, Reginald G.

    2016-09-01

    Stereophotogrammetry typically employs a pair of cameras, or a single moving camera, to acquire pairs of images from different camera positions, in order to create a three dimensional `range map' of the area being observed. Applications of this technique for building three-dimensional shape models include aerial surveying, remote sensing, machine vision, and robotics. Factors that would be expected to affect the quality of the range maps include the projection function (distortion) of the lenses and the contrast (modulation) and signal-to-noise ratio (SNR) of the acquired image pairs. Basic models of the precision with which the range can be measured assume a pinhole-camera model of the geometry, i.e. that the lenses provide perspective projection with zero distortion. Very-wide-angle or `fisheye' lenses, however (for e.g. those used by robotic vehicles) typically exhibit projection functions that differ significantly from this assumption. To predict the stereophotogrammetric range precision for such applications, we extend the model to the case of an equidistant lens projection function suitable for a very-wide-angle lens. To predict the effects of contrast and SNR on range precision, we perform numerical simulations using stereo image pairs acquired by a stereo camera pair on NASA's Mars rover Curiosity. Contrast is degraded and noise is added to these data in a controlled fashion and the effects on the quality of the resulting range maps are assessed.

  9. Noise of Embedded High Aspect Ratio Nozzles

    Science.gov (United States)

    Bridges, James E.

    2011-01-01

    A family of high aspect ratio nozzles were designed to provide a parametric database of canonical embedded propulsion concepts. Nozzle throat geometries with aspect ratios of 2:1, 4:1, and 8:1 were chosen, all with convergent nozzle areas. The transition from the typical round duct to the rectangular nozzle was designed very carefully to produce a flow at the nozzle exit that was uniform and free from swirl. Once the basic rectangular nozzles were designed, external features common to embedded propulsion systems were added: extended lower lip (a.k.a. bevel, aft deck), differing sidewalls, and chevrons. For the latter detailed Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) simulations were made to predict the thrust performance and to optimize parameters such as bevel length, and chevron penetration and azimuthal curvature. Seventeen of these nozzles were fabricated at a scale providing a 2.13 inch diameter equivalent area throat." ! The seventeen nozzles were tested for far-field noise and a few data were presented here on the effect of aspect ratio, bevel length, and chevron count and penetration. The sound field of the 2:1 aspect ratio rectangular jet was very nearly axisymmetric, but the 4:1 and 8:1 were not, the noise on their minor axes being louder than the major axes. Adding bevel length increased the noise of these nozzles, especially on their minor axes, both toward the long and short sides of the beveled nozzle. Chevrons were only added to the 2:1 rectangular jet. Adding 4 chevrons per wide side produced some decrease at aft angles, but increased the high frequency noise at right angles to the jet flow. This trend increased with increasing chevron penetration. Doubling the number of chevrons while maintaining their penetration decreased these effects. Empirical models of the parametric effect of these nozzles were constructed and quantify the trends stated above." Because it is the objective of the Supersonics Project that

  10. 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.

  11. Enhanced contrast ratio of homogeneously aligned liquid crystal displays by controlling the surface-anchoring strength

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Young Jin; Woo, Chang Woo; Oh, Sang Hoon; Mukherjee, Amrita; Lee, Seung Hee [Department of BIN Fusion Technology and Department of Polymer Nano-Science and Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Baek, Ji Ho; Kim, Kyeong Jin; Yang, Myung Su, E-mail: lsh1@chonbuk.ac.kr [Panel Performance Department, LG Display Co., Ltd., Paju, Gyeonggi-do 413-811 (Korea, Republic of)

    2011-08-17

    The dark state of homogeneously aligned liquid crystal displays (LCDs) associated with the in-plane switching of a LC director depends on their molecular ordering. We propose a new approach to reduce the light leakage in the dark state of homogeneously aligned LCDs. A very small amount of reactive mesogen (RM) is mixed with the LC material and polymerized at room temperature and also at a low temperature (-20 {sup 0}C) to strengthen the surface-anchoring energy. The contrast ratio of the low-temperature cured cell is improved by about 50% over that of the pure LC cell and the room temperature cured RM-mixed LC cell due to an enhanced order parameter.

  12. Extreme Contrast Ratio Imaging of Sirius with a Charge Injection Device

    Science.gov (United States)

    Batcheldor, D.; Foadi, R.; Bahr, C.; Jenne, J.; Ninkov, Z.; Bhaskaran, S.; Chapman, T.

    2016-02-01

    The next fundamental steps forward in understanding our place in the universe could be a result of advances in extreme contrast ratio (ECR) imaging and point-spread function (PSF) suppression. For example, blinded by quasar light we have yet to fully understand the processes of galaxy and star formation and evolution, and there is an ongoing race to obtain a direct image of an exo-Earth lost in the glare of its host star. To fully explore the features of these systems, we must perform observations in which contrast ratios (CRs) of at least one billion can be regularly achieved with sub 0.″1 inner working angles. Here, we present the details of a latest-generation 32-bit charge injection device (CID) that could conceivably achieve CRs on the order of one billion. We also demonstrate some of its ECR imaging abilities for astronomical imaging. At a separation of two arcminutes, we report a direct CR of {{Δ }}{m}v=18.3,{log}({CR})=7.3, or 1 part in 20 million, from observations of the Sirius field. The atmospheric conditions present during the collection of this data prevented less modest results, and we expect to be able to achieve higher CRs, with improved inner working angles, simply by operating a CID at a world-class observing site. However, CIDs do not directly provide any PSF suppression. Therefore, combining CID imaging with a simple PSF suppression technique like angular differential imaging could provide a cheap and easy alternative to the complex ECR techniques currently being employed.

  13. 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.

  14. 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....

  15. 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...

  16. 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

  17. Sedimentary Sulphur:Iron Ratio Indicates Vivianite Occurrence: A Study from Two Contrasting Freshwater Systems.

    Directory of Open Access Journals (Sweden)

    Matthias Rothe

    Full Text Available An increasing number of studies constrain the importance of iron for the long-term retention of phosphorus (P under anoxic conditions, i.e. the formation of reduced iron phosphate minerals such as vivianite (Fe3(PO42⋅8H2O. Much remains unknown about vivianite formation, the factors controlling its occurrence, and its relevance for P burial during early sediment diagenesis. To study the occurrence of vivianite and to assess its relevance for P binding, surface sediments of two hydrologically contrasting waters were analysed by heavy-liquid separation and subsequent powder X-ray diffraction. In Lake Arendsee, vivianite was present in deeper sediment horizons and not in the uppermost layers with a sharp transition between vivianite and non-vivianite bearing layers. In contrast, in lowland river Lower Havel vivianite was present in the upper sediment layers and not in deeper horizons with a gradual transition between non-vivianite and vivianite bearing layers. In both waters, vivianite occurrence was accompanied by the presence of pyrite (FeS2. Vivianite formation was favoured by an elevated iron availability through a lower degree of sulphidisation and was present at a molar ratio of total sulphur to reactive iron smaller than 1.1, only. A longer lasting burden of sediments by organic matter, i.e. due to eutrophication, favours the release of sulphides, and the formation of insoluble iron sulphides leading to a lack of available iron and to less or no vivianite formation. This weakening in sedimentary P retention, representing a negative feedback mechanism (P release in terms of water quality, could be partly compensated by harmless Fe amendments.

  18. 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

  19. 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

  20. High Aspect Ratio Semiconductor Heterojunction Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Redwing, Joan [Pennsylvania State Univ., University Park, PA (United States). Dept. of Material Science and Engineering; Mallouk, Tom [Pennsylvania State Univ., University Park, PA (United States). Dept. of Chemistry; Mayer, Theresa [Pennsylvania State Univ., University Park, PA (United States). Dept. of Electrical Engineering; Dickey, Elizabeth [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering; Wronski, Chris [Pennsylvania State Univ., University Park, PA (United States). Dept. of Electrical Engineering

    2013-05-17

    The project focused on the development of high aspect ratio silicon heterojunction (HARSH) solar cells. The solar cells developed in this study consisted of high density vertical arrays of radial junction silicon microwires/pillars formed on Si substrates. Prior studies have demonstrated that vertical Si wire/pillar arrays enable reduced reflectivity and improved light trapping characteristics compared to planar solar cells. In addition, the radial junction structure offers the possibility of increased carrier collection in solar cells fabricated using material with short carrier diffusion lengths. However, the high junction and surface area of radial junction Si wire/pillar array devices can be problematic and lead to increased diode leakage and enhanced surface recombination. This study investigated the use of amorphous hydrogenated Si in the form of a heterojunction-intrinsic-thin layer (HIT) structure as a junction formation method for these devices. The HIT layer structure has widely been employed to reduce surface recombination in planar crystalline Si solar cells. Consequently, it was anticipated that it would also provide significant benefits to the performance of radial junction Si wire/pillar array devices. The overall goals of the project were to demonstrate a HARSH cell with a HIT-type structure in the radial junction Si wire/pillar array configuration and to develop potentially low cost pathways to fabricate these devices. Our studies demonstrated that the HIT structure lead to significant improvements in the open circuit voltage (Voc>0.5) of radial junction Si pillar array devices compared to devices fabricated using junctions formed by thermal diffusion or low pressure chemical vapor deposition (LPCVD). In addition, our work experimentally demonstrated that the radial junction structure lead to improvements in efficiency compared to comparable planar devices for devices fabricated using heavily doped Si that had reduced carrier diffusion

  1. Shape matters: synthesis and biomedical applications of high aspect ratio magnetic nanomaterials

    OpenAIRE

    Raluca M Fratila; Rivera-Fernández, Sara; Fuente, Jesús M. de la

    2015-01-01

    High aspect ratio magnetic nanomaterials possess anisotropic properties that make them attractive for biological applications. Their elongated shape enables multivalent interactions with receptors through the introduction of multiple targeting units on their surface, thus enhancing cell internalization. Moreover, due to their magnetic anisotropy, high aspect ratio nanomaterials can outperform their spherical analogues as contrast agents for magnetic resonance imaging (MRI) applications. In th...

  2. 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.

  3. 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.

  4. 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.

  5. Injection Molding of High Aspect Ratio Nanostructures

    DEFF Research Database (Denmark)

    Matschuk, Maria; Larsen, Niels Bent

    We present a process for injection molding of 40 nm wide and >100 nm high pillars (pitch: 200 nm). We explored the effects of mold coatings and injection molding conditions on the replication quality of nanostructures in cyclic olefin copolymer. We found that optimization of molding parameters...

  6. 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.

  7. New microangiography system development providing improved small vessel imaging, increased contrast-to-noise ratios, and multiview 3D reconstructions

    Science.gov (United States)

    Kuhls, Andrew T.; Patel, Vikas; Ionita, Ciprian; Noël, Peter B.; Walczak, Alan M.; Rangwala, Hussain S.; Hoffmann, Kenneth R.; Rudin, Stephen

    2006-03-01

    A new microangiographic system (MA) integrated into a c-arm gantry has been developed allowing precise placement of a MA at the exact same angle as the standard x-ray image intensifier (II) with unchanged source and object position. The MA can also be arbitrarily moved about the object and easily moved into the field of view (FOV) in front of the lower resolution II when higher resolution angiographic sequences are needed. The benefits of this new system are illustrated in a neurovascular study, where a rabbit is injected with contrast media for varying oblique angles. Digital subtraction angiographic (DSA) images were obtained and compared using both the MA and II detectors for the same projection view. Vessels imaged with the MA appear sharper with smaller vessels visualized. Visualization of ~100 μm vessels was possible with the MA whereas not with the II. Further, the MA could better resolve vessel overlap. Contrast to noise ratios (CNR) were calculated for vessels of varying sizes for the MA versus the II and were found to be similar for large vessels, approximately double for medium vessels, and infinitely better for the smallest vessels. In addition, a 3D reconstruction of selected vessel segments was performed, using multiple (three) projections at oblique angles, for each detector. This new MA/II integrated system should lead to improved diagnosis and image guidance of neurovascular interventions by enabling initial guidance with the low resolution large FOV II combined with use of the high resolution MA during critical parts of diagnostic and interventional procedures.

  8. 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.

  9. 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.

  10. Large eddy simulation of a high aspect ratio combustor

    Science.gov (United States)

    Kirtas, Mehmet

    The present research investigates the details of mixture preparation and combustion in a two-stroke, small-scale research engine with a numerical methodology based on large eddy simulation (LES) technique. A major motivation to study such small-scale engines is their potential use in applications requiring portable power sources with high power density. The investigated research engine has a rectangular planform with a thickness very close to quenching limits of typical hydrocarbon fuels. As such, the combustor has a high aspect ratio (defined as the ratio of surface area to volume) that makes it different than the conventional engines which typically have small aspect ratios to avoid intense heat losses from the combustor in the bulk flame propagation period. In most other aspects, this engine involves all the main characteristics of traditional reciprocating engines. A previous experimental work has identified some major design problems and demonstrated the feasibility of cyclic combustion in the high aspect ratio combustor. Because of the difficulty of carrying out experimental studies in such small devices, resolving all flow structures and completely characterizing the flame propagation have been an enormously challenging task. The numerical methodology developed in this work attempts to complement these previous studies by providing a complete evolution of flow variables. Results of the present study demonstrated strengths of the proposed methodology in revealing physical processes occuring in a typical operation of the high aspect ratio combustor. For example, in the scavenging phase, the dominant flow structure is a tumble vortex that forms due to the high velocity reactant jet (premixed) interacting with the walls of the combustor. Since the scavenging phase is a long process (about three quarters of the whole cycle), the impact of the vortex is substantial on mixture preparation for the next combustion phase. LES gives the complete evolution of this flow

  11. 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...

  12. 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

  13. 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....

  14. High/variable mixture ratio O2/H2 engine

    Science.gov (United States)

    Adams, A.; Parsley, R. C.

    1988-01-01

    Vehicle/engine analysis studies have identified the High/Dual Mixture Ratio O2/H2 Engine cycle as a leading candidate for an advanced Single Stage to Orbit (SSTO) propulsion system. This cycle is designed to allow operation at a higher than normal O/F ratio of 12 during liftoff and then transition to a more optimum O/F ratio of 6 at altitude. While operation at high mixture ratios lowers specific impulse, the resultant high propellant bulk density and high power density combine to minimize the influence of atmospheric drag and low altitude gravitational forces. Transition to a lower mixture ratio at altitude then provides improved specific impulse relative to a single mixture ratio engine that must select a mixture ratio that is balanced for both low and high altitude operation. This combination of increased altitude specific impulse and high propellant bulk density more than offsets the compromised low altitude performance and results in an overall mission benefit. Two areas of technical concern relative to the execution of this dual mixture ratio cycle concept are addressed. First, actions required to transition from high to low mixture ratio are examined, including an assessment of the main chamber environment as the main chamber mixture ratio passes through stoichiometric. Secondly, two approaches to meet a requirement for high turbine power at high mixture ratio condition are examined. One approach uses high turbine temperature to produce the power and requires cooled turbines. The other approach incorporates an oxidizer-rich preburner to increase turbine work capability via increased turbine mass flow.

  15. Evidence for positive, but not negative, behavioral contrast with wheel-running reinforcement on multiple variable-ratio schedules.

    Science.gov (United States)

    Belke, Terry W; Pierce, W David

    2016-12-01

    Rats responded on a multiple variable-ratio (VR) 10 VR 10 schedule of reinforcement in which lever pressing was reinforced by the opportunity to run in a wheel for 30s in both the changed (manipulated) and unchanged components. To generate positive contrast, the schedule of reinforcement in the changed component was shifted to extinction; to generate negative contrast, the schedule was shifted to VR 3. With the shift to extinction in the changed component, wheel-running and local lever-pressing rates increased in the unchanged component, a result supporting positive contrast; however, the shift to a VR 3 schedule in the changed component showed no evidence of negative contrast in the unaltered setting, only wheel running decreased in the unchanged component. Changes in wheel-running rates across components were consistent in showing a compensation effect, depending on whether the schedule manipulation increased or decreased opportunities for wheel running in the changed component. These findings are the first to demonstrate positive behavioral contrast on a multiple schedule with wheel running as reinforcement in both components.

  16. 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.

  17. 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 ...

  18. 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.

  19. 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.

  20. Quality assurance in MRI breast screening: comparing signal-to-noise ratio in dynamic contrast-enhanced imaging protocols

    Science.gov (United States)

    Kousi, Evanthia; Borri, Marco; Dean, Jamie; Panek, Rafal; Scurr, Erica; Leach, Martin O.; Schmidt, Maria A.

    2016-01-01

    MRI has been extensively used in breast cancer staging, management and high risk screening. Detection sensitivity is paramount in breast screening, but variations of signal-to-noise ratio (SNR) as a function of position are often overlooked. We propose and demonstrate practical methods to assess spatial SNR variations in dynamic contrast-enhanced (DCE) breast examinations and apply those methods to different protocols and systems. Four different protocols in three different MRI systems (1.5 and 3.0 T) with receiver coils of different design were employed on oil-filled test objects with and without uniformity filters. Twenty 3D datasets were acquired with each protocol; each dataset was acquired in under 60 s, thus complying with current breast DCE guidelines. In addition to the standard SNR calculated on a pixel-by-pixel basis, we propose other regional indices considering the mean and standard deviation of the signal over a small sub-region centred on each pixel. These regional indices include effects of the spatial variation of coil sensitivity and other structured artefacts. The proposed regional SNR indices demonstrate spatial variations in SNR as well as the presence of artefacts and sensitivity variations, which are otherwise difficult to quantify and might be overlooked in a clinical setting. Spatial variations in SNR depend on protocol choice and hardware characteristics. The use of uniformity filters was shown to lead to a rise of SNR values, altering the noise distribution. Correlation between noise in adjacent pixels was associated with data truncation along the phase encoding direction. Methods to characterise spatial SNR variations using regional information were demonstrated, with implications for quality assurance in breast screening and multi-centre trials.

  1. 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...

  2. Image fusion in dual energy computed tomography for detection of various anatomic structures - Effect on contrast enhancement, contrast-to-noise ratio, signal-to-noise ratio and image quality

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Jijo, E-mail: jijopaul1980@gmail.com [Department of Diagnostic Radiology, Goethe University Hospital, Theodor-Stern-Kai 7, 60590 Frankfurt am Main (Germany); Department of Biophysics, Goethe University, Max von Laue-Str.1, 60438 Frankfurt am Main (Germany); Bauer, Ralf W. [Department of Diagnostic Radiology, Goethe University Hospital, Theodor-Stern-Kai 7, 60590 Frankfurt am Main (Germany); Maentele, Werner [Department of Biophysics, Goethe University, Max von Laue-Str.1, 60438 Frankfurt am Main (Germany); Vogl, Thomas J. [Department of Diagnostic Radiology, Goethe University Hospital, Theodor-Stern-Kai 7, 60590 Frankfurt am Main (Germany)

    2011-11-15

    Objective: The purpose of this study was to evaluate image fusion in dual energy computed tomography for detecting various anatomic structures based on the effect on contrast enhancement, contrast-to-noise ratio, signal-to-noise ratio and image quality. Material and methods: Forty patients underwent a CT neck with dual energy mode (DECT under a Somatom Definition flash Dual Source CT scanner (Siemens, Forchheim, Germany)). Tube voltage: 80-kV and Sn140-kV; tube current: 110 and 290 mA s; collimation-2 x 32 x 0.6 mm. Raw data were reconstructed using a soft convolution kernel (D30f). Fused images were calculated using a spectrum of weighting factors (0.0, 0.3, 0.6 0.8 and 1.0) generating different ratios between the 80- and Sn140-kV images (e.g. factor 0.6 corresponds to 60% of their information from the 80-kV image, and 40% from the Sn140-kV image). CT values and SNRs measured in the ascending aorta, thyroid gland, fat, muscle, CSF, spinal cord, bone marrow and brain. In addition, CNR values calculated for aorta, thyroid, muscle and brain. Subjective image quality evaluated using a 5-point grading scale. Results compared using paired t-tests and nonparametric-paired Wilcoxon-Wilcox-test. Results: Statistically significant increases in mean CT values noted in anatomic structures when increasing weighting factors used (all P {<=} 0.001). For example, mean CT values derived from the contrast enhanced aorta were 149.2 {+-} 12.8 Hounsfield Units (HU), 204.8 {+-} 14.4 HU, 267.5 {+-} 18.6 HU, 311.9 {+-} 22.3 HU, 347.3 {+-} 24.7 HU, when the weighting factors 0.0, 0.3, 0.6, 0.8 and 1.0 were used. The highest SNR and CNR values were found in materials when the weighting factor 0.6 used. The difference CNR between the weighting factors 0.6 and 0.3 was statistically significant in the contrast enhanced aorta and thyroid gland (P = 0.012 and P = 0.016, respectively). Visual image assessment for image quality showed the highest score for the data reconstructed using the

  3. Fabrication of high-aspect ratio SU-8 micropillar arrays

    DEFF Research Database (Denmark)

    Amato, Letizia; Keller, Stephan S.; Heiskanen, Arto

    2012-01-01

    SU-8 is the preferred photoresist for development and fabrication of high aspect ratio (HAR) three dimensional patterns. However, processing of SU-8 is a challenging task, especially when the film thickness as well as the aspect ratio is increasing and the size of the features is close to the res...

  4. 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.

  5. Evaluation and comparison of contrast to noise ratio and signal to noise ratio according to change of reconstruction on breast PET/CT

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Young Jae [Dept. of Nuclear Medicine, Seoul National University Hospital, Seoul (Korea, Republic of); Lee, Eul Kyu [Dept. of Radiology, Inje Paik University Hospital Jeo-dong, Seoul (Korea, Republic of); Kim, Ki Won [Dept. of Radiology, Kyung Hee University Hospital at Gang-dong, Seoul (Korea, Republic of); Jeong, Hoi Woun [Dept. of Radiological Technology, The Baekseok Culture University, Cheonan (Korea, Republic of); Lyu, Kwang Yeul; Park, Hoon Hee; Son, Jin Hyun; Min, Jung Whan [Dept. of Radiological Technology, The Shingu University, Sungnam (Korea, Republic of)

    2017-03-15

    The purpose of this study was to measure contrast to noise ratio (CNR) and signal to noise ratio (SNR) according to change of reconstruction from region of interest (ROI) in breast positron emission tomography- computed tomography (PET-CT), and to analyze the CNR and SNR statically. We examined images of breast PET-CT of 100 patients in a University-affiliated hospital, Seoul, Korea. Each patient's image of breast PET-CT were calculated by using Image J. Differences of CNR and SNR among four reconstruction algorithms were tested by SPSS Statistics21 ANOVA test for there was statistical significance (p<0.05). We have analysis socio-demographical variables, CNR and SNR according to reconstruction images, 95% confidence according to CNR and SNR of reconstruction and difference in a mean of CNR and SNR. SNR results, with the quality of distributions in the order of PSF{sub T}OF, Iterative and Iterative-TOF, FBP-TOF. CNR, with the quality of distributions in the order of PSF{sub T}OF, Iterative and Iterative-TOF, FBP-TOF. CNR and SNR of PET-CT reconstruction methods of the breast would be useful to evaluate breast diseases.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Efficiency of nonstandard and high contact ratio involute spur gears

    Science.gov (United States)

    Anderson, N. E.; Loewenthal, S. H.

    1986-01-01

    A power loss prediction was extended to include involute spur gears of nonstandard proportions. The method is used to analyze the effects of modified addendum, tooth thickness, and gear center distance in addition to the parameters previously considered which included gear diameter, pitch, pressure angle, face width, oil viscosity, speed, and torque. Particular emphasis was placed on high contact ratio gearing (contact ratios greater than two). Despite their higher sliding velocities, high contact ratio gears are designed to levels of efficiency comparable to those of conventional gears while retaining their advantages through proper selection of gear geometry.

  11. Optimization of Contrast-to-Tissue Ratio by Adaptation of Transmitted Ternary Signal in Ultrasound Pulse Inversion Imaging

    Directory of Open Access Journals (Sweden)

    Sébastien Ménigot

    2013-01-01

    Full Text Available Ultrasound contrast imaging has provided more accurate medical diagnoses thanks to the development of innovating modalities like the pulse inversion imaging. However, this latter modality that improves the contrast-to-tissue ratio (CTR is not optimal, since the frequency is manually chosen jointly with the probe. However, an optimal choice of this command is possible, but it requires precise information about the transducer and the medium which can be experimentally difficult to obtain, even inaccessible. It turns out that the optimization can become more complex by taking into account the kind of generators, since the generators of electrical signals in a conventional ultrasound scanner can be unipolar, bipolar, or tripolar. Our aim was to seek the ternary command which maximized the CTR. By combining a genetic algorithm and a closed loop, the system automatically proposed the optimal ternary command. In simulation, the gain compared with the usual ternary signal could reach about 3.9 dB. Another interesting finding was that, in contrast to what is generally accepted, the optimal command was not a fixed-frequency signal but had harmonic components.

  12. Scattering and extinction from high-aspect-ratio trenches

    DEFF Research Database (Denmark)

    Roberts, Alexander Sylvester; Søndergaard, Thomas; Chirumamilla, Manohar;

    2015-01-01

    We construct a semi-analytical model describing the scattering, extinction and absorption properties of a high aspect-ratio trench in a metallic film. We find that these trenches act as highly efficient scatterers of free waves. In the perfect conductor limit, which for many metals is approached...

  13. Computation of compressible flows with high density ratio and pressure ratio

    Institute of Scientific and Technical Information of China (English)

    CHEN Rong-san

    2008-01-01

    The WENO method, RKDG method, RKDG method with original ghost fluid method, and RKDG method with modified ghost fluid method are applied to single-medium and two-medium air-air, air-liquid compressible flows with high density and pressure ratios. We also provide a numerical comparison and analysis for the above methods. Numerical results show that, compared with the other methods, the RKDG method with modified ghost fluid method can obtain high resolution results and the correct position of the shock, and the computed solutions are converged to the physical solutions as the mesh is refined.

  14. Interpreting high [O III]/Hbeta ratios with maturing starbursts

    CERN Document Server

    Stanway, E R; Greis, S M L; Davies, L J M; Wilkins, S M; Bremer, M N

    2014-01-01

    Star forming galaxies at high redshift show ubiquitously high ionization parameters, as measured by the ratio of optical emission lines. We demonstrate that local (z < 0.2) sources selected as Lyman break analogues also manifest high line ratios with a typical [O III]/H beta = 3.36(+0.14,-0.04) - comparable to all but the highest ratios seen in star forming galaxies at z ~ 2-4. We argue that the stellar population synthesis code BPASS can explain the high ionization parameters required through the ageing of rapidly formed star populations, without invoking any AGN contribution. Binary stellar evolution pathways prolong the age interval over which a starburst is likely to show elevated line ratios, relative to those predicted by single stellar evolution codes. As a result, model galaxies at near-Solar metallicities and with ages of up to ~100 Myr after a starburst typically have a line ratio [O III]/H beta~3, consistent with those seen in Lyman break galaxies and local sources with similar star formation de...

  15. Is China’s Investment Ratio Too High?

    Institute of Scientific and Technical Information of China (English)

    张汉亚

    2007-01-01

    In recent years,overseas observers have reached a consensus upon attributing China’s sustained rapid economic growth primarily to high investment.This consensus opinion has also struck a resonant chord among a large number of domestic researchers who acknowledge the tremendous contribution of continued high fixed asset investment to China’s economic growth,and often wonder whether"the investment ratio is too high"and"the economy is overheating".In this article,renowned economist Zhang Hanya elaborates upon the real economic meaning of"investment ratio",and sets out reasonable criteria for the"investment/consumption ratio".His explanations help us to clarify our understanding and judgments regarding the related issues.

  16. 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

  17. Study of High Capacitance Ratios CPW MEMS Shunt Switches

    Institute of Scientific and Technical Information of China (English)

    Jianhai Sun; Dafu Cui

    2006-01-01

    This paper describes a fixed-fixed beam ohmic switch in series with a fixed capacitor as a replacement for a capacitive switch. In this switch, a metal plate deposited on the dielectric ensures perfectly contact with the dielectric layer in the down state. The area size of the metal plate directly influences the capacitance ratio of the switch, as the area size of the metal cap decreases, the capacitance ratio dramatically rises up. The down/up capacitance ratio can exceed 800 times over the conventional designs using the same materials and the equal size. Measurement results show that high capacitance ratio of the switches has a large effect on the isolation, and can actually improve the performance of the switches.

  18. 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.

  19. Cross section to multiplicity ratios at very high energy

    Energy Technology Data Exchange (ETDEWEB)

    Block, M.M. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Stodolsky, L. [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut), Föhringer Ring 6, 80805 München (Germany)

    2014-06-27

    Recent data from the LHC makes it possible to examine an old speculation that at very high energy the total multiplicity and the cross section in elementary particle interactions vary in parallel with energy. Using fits incorporating the new data, it appears that the ratios of the total, elastic, and inelastic cross sections to the average multiplicity N can in fact approach constants at very high energy. The approach to the limit is however quite slow for the total and inelastic cross sections and is not yet reached at LHC energies. The elastic ratio σ{sup el}/N at 7 TeV, however, is not far from its asymptotic value.

  20. 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...

  1. The Effects of Cation Ratios on Root Lamella Suberization in Rice (Oryza sativa L. with Contrasting Salt Tolerance

    Directory of Open Access Journals (Sweden)

    M. R. Momayezi

    2012-01-01

    Full Text Available Rice is an important produced cereal in the world. We evaluated the effect of salt compositions including NaCl and Na2SO4 on suberin lamellae as a major barrier to radial ion and water movements in two rice genotypes representing contrasting salt tolerance levels under salinity stress. Two rice genotypes, Fajr as salt tolerant and Khazar as salt sensitive, were transplanted in sand culture under glasshouse condition. Rice seedlings were treated with five salt compositions including NaCl, Na2SO4, 1 : 1, 1 : 2, and 2 : 1 molar ratios for 40 days. It was proven that suberin lamellae in endodermis of root cell wall were thickened with Na2SO4 treatment. The results demonstrated that the number of passage cells was higher in Fajr genotype than that in Khazar genotype under saline condition. Calcium concentration in root tissue decreased as the SO42- concentration in root media increased. It can be concluded that Fajr genotype is able to keep some passage cells open to maintain Ca2+ uptake. The Ca2+/Na+ ratio in shoot tissue can be also a reliable index for the early recognition of salt stress in these rice genotypes.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. High-aspect ratio magnetic nanocomposite polymer cilium

    Science.gov (United States)

    Rahbar, M.; Tseng, H. Y.; Gray, B. L.

    2014-03-01

    This paper presents a new fabrication technique to achieve ultra high-aspect ratio artificial cilia micro-patterned from flexible highly magnetic rare earth nanoparticle-doped polymers. We have developed a simple, inexpensive and scalable fabrication method to create cilia structures that can be actuated by miniature electromagnets, that are suitable to be used for lab-on-a chip (LOC) and micro-total-analysis-system (μ-TAS) applications such as mixers and flow-control elements. The magnetic cilia are fabricated and magnetically polarized directly in microfluidic channels or reaction chambers, allowing for easy integration with complex microfluidic systems. These cilia structures can be combined on a single chip with other microfluidic components employing the same permanently magnetic nano-composite polymer (MNCP), such as valves or pumps. Rare earth permanent magnetic powder, (Nd0.7Ce0.3)10.5Fe83.9B5.6, is used to dope polydimethylsiloxane (PDMS), resulting in a highly flexible M-NCP of much higher magnetization and remanence [1] than ferromagnetic polymers typically employed in magnetic microfluidics. Sacrificial poly(ethylene-glycol) (PEG) is used to mold the highly magnetic polymer into ultra high-aspect ratio artificial cilia. Cilia structures with aspect ratio exceeding 8:0.13 can be easily fabricated using this technique and are actuated using miniature electromagnets to achieve a high range of motion/vibration.

  11. High lift generation of low-aspect-ratio wings

    Science.gov (United States)

    Devoria, Adam; Mohseni, Kamran

    2016-11-01

    The time-averaged flow field in the center-span of low-aspect-ratio rectangular wings is experimentally measured. It is shown that lift stall is preceded by shedding of strong trailing-edge vorticity. The induced downwash of the tip vortices delays the growth of the attached boundary layer as well as leading-edge separation. Reattached flow occurs for sufficiently low aspect ratios and results in a smooth merging of the flow at the trailing edge thus assisting in satisfying a Kutta condition there. As a consequence, the strength of vorticity shed from the trailing edge is decreased and allows for continued lift generation at high angles of attack. When the reattachment point passes beyond the trailing edge, a strong shear layer is generated there and represents negative lift, leading to stall with a slight increase in angle of attack or aspect ratio.

  12. Formation of High Aspect Ratio Microcoil Using Dipping Method

    Science.gov (United States)

    Noda, Daiji; Yamashita, Shuhei; Matsumoto, Yoshifumi; Setomoto, Masaru; Hattori, Tadashi

    Coils are used in many electronic devices as inductors in mobile units such as mobile phone, digital cameras, etc. Inductance and quality factor of coils are very important value of the performance. Therefore, the requests for coils are small size, high inductance, low power consumption, etc. However, coils are unsuitable for miniaturization because of its structure. Therefore, we have proposed and developed the microcoils of high aspect ratio with the dipping method and an X-ray lithography technique. In dipping method, centrifugal force and highly viscous photoresist solution were key points to evenly apply resist in the form of thick film on metal bar. The film thickness of resist on bar was achieved about 50 μm after single coating. Using these techniques, we succeeded in creating threaded groove structure with 10 μm lines and spaces on 1 mm brass bar. In this case, the aspect ratio was achieved five. It is very expected the high performance microcoil with high aspect ratio lines could be manufactured in spite of the miniature size.

  13. Iodine potassium iodide improves the contrast-to-noise ratio of micro-computed tomography images of the human middle ear.

    Science.gov (United States)

    Rohani, S A; Ghomashchi, S; Umoh, J; Holdsworth, D W; Agrawal, S K; Ladak, H M

    2016-12-01

    High-resolution imaging of middle-ear geometry is necessary for finite-element modeling. Although micro-computed tomography (microCT) is widely used because of its ability to image bony structures of the middle ear, it is difficult to visualize soft tissues - including the tympanic membrane and the suspensory ligaments/tendons - because of lack of contrast. The objective of this research is to quantitatively evaluate the efficacy of iodine potassium iodide (IKI) solution as a contrast agent. Six human temporal bones were used in this experiment, which were obtained in right-left pairs, from three cadaveric heads. All bones were fixed using formaldehyde. Three bones (one from each pair) were stained in IKI solution for 2 days, whereas the other three were not stained. Samples were scanned using a microCT system at a resolution of 20 μm. Eight soft tissues in the middle ear were segmented: anterior mallear ligament, incudomallear joint, lateral mallear ligament, posterior incudal ligament, stapedial annular ligament, stapedius muscle, tympanic membrane and tensor tympani muscle. Contrast-to-noise ratios (CNRs) of each soft tissue were calculated for each temporal bone. Combined CNRs of the soft tissues in unstained samples were 6.1 ± 3.0, whereas they were 8.1 ± 2.7 in stained samples. Results from Welch's t-test indicate significant difference between the two groups at a 95% confidence interval. Results for paired t-tests for each of the individual soft tissues also indicated significant improvement of contrast in all tissues after staining. Relatively large soft tissues in the middle ear such as the tympanic membrane and the tensor tympani muscle were impacted by staining more than smaller tissues such as the stapedial annular ligament. The increase in contrast with IKI solution confirms its potential application in automatic segmentation of the middle-ear soft tissues.

  14. 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

  15. Shape matters: synthesis and biomedical applications of high aspect ratio magnetic nanomaterials.

    Science.gov (United States)

    Fratila, Raluca M; Rivera-Fernández, Sara; de la Fuente, Jesús M

    2015-05-14

    High aspect ratio magnetic nanomaterials possess anisotropic properties that make them attractive for biological applications. Their elongated shape enables multivalent interactions with receptors through the introduction of multiple targeting units on their surface, thus enhancing cell internalization. Moreover, due to their magnetic anisotropy, high aspect ratio nanomaterials can outperform their spherical analogues as contrast agents for magnetic resonance imaging (MRI) applications. In this review, we first describe the two main synthetic routes for the preparation of anisotropic magnetic nanomaterials: (i) direct synthesis (in which the anisotropic growth is directed by tuning the reaction conditions or by using templates) and (ii) assembly methods (in which the high aspect ratio is achieved by assembly from individual building blocks). We then provide an overview of the biomedical applications of anisotropic magnetic nanomaterials: magnetic separation and detection, targeted delivery and magnetic resonance imaging.

  16. Shape matters: synthesis and biomedical applications of high aspect ratio magnetic nanomaterials

    Science.gov (United States)

    Fratila, Raluca M.; Rivera-Fernández, Sara; de La Fuente, Jesús M.

    2015-04-01

    High aspect ratio magnetic nanomaterials possess anisotropic properties that make them attractive for biological applications. Their elongated shape enables multivalent interactions with receptors through the introduction of multiple targeting units on their surface, thus enhancing cell internalization. Moreover, due to their magnetic anisotropy, high aspect ratio nanomaterials can outperform their spherical analogues as contrast agents for magnetic resonance imaging (MRI) applications. In this review, we first describe the two main synthetic routes for the preparation of anisotropic magnetic nanomaterials: (i) direct synthesis (in which the anisotropic growth is directed by tuning the reaction conditions or by using templates) and (ii) assembly methods (in which the high aspect ratio is achieved by assembly from individual building blocks). We then provide an overview of the biomedical applications of anisotropic magnetic nanomaterials: magnetic separation and detection, targeted delivery and magnetic resonance imaging.

  17. Aeroelastic stability analysis of high aspect ratio aircraft wings

    OpenAIRE

    Banerjee, J. R.; Liu, X.; Kassem, H. I.

    2014-01-01

    Free vibration and flutter analyses of two types of high aspect ratio aircraft wings are presented. The wing is idealised as an assembly of bending-torsion coupled beams using the dynamic stiffness method leading to a nonlinear eigenvalue problem. This problem is solved using the Wattrick-Williams algorithm yielding natural frequencies and mode shapes. The flutter analysis is carried out using the normal mode method in conjunction with generalised coordinates and two-dimensional unsteady aero...

  18. High-performance metasurface polarizers with extinction ratios exceeding 12000.

    Science.gov (United States)

    Kurosawa, Hiroyuki; Choi, Bongseok; Sugimoto, Yoshimasa; Iwanaga, Masanobu

    2017-02-20

    High-performance ultrathin polarizers have been experimentally demonstrated employing stacked complementary (SC) metasurfaces, which were produced using nanoimprint lithography. It is experimentally determined that the metasurface polarizers composed of Ag and Au have large extinction ratios exceeding 17000 and 12000, respectively, in spite of the subwavelength thickness. It is also shown that the ultrathin polarizers of the SC structures are optimized at telecommunication wavelengths.

  19. 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.

  20. Experimental Investigation of a High Pressure Ratio Aspirated Fan Stage

    Science.gov (United States)

    Merchant, Ali; Kerrebrock, Jack L.; Adamczyk, John J.; Braunscheidel, Edward

    2004-01-01

    The experimental investigation of an aspirated fan stage designed to achieve a pressure ratio of 3.4:1 at 1500 ft/sec is presented in this paper. The low-energy viscous flow is aspirated from diffusion-limiting locations on the blades and flowpath surfaces of the stage, enabling a very high pressure ratio to be achieved in a single stage. The fan stage performance was mapped at various operating speeds from choke to stall in a compressor facility at fully simulated engine conditions. The experimentally determined stage performance, in terms of pressure ratio and corresponding inlet mass flow rate, was found to be in good agreement with the three-dimensional viscous computational prediction, and in turn close to the design intent. Stage pressure ratios exceeding 3:1 were achieved at design speed, with an aspiration flow fraction of 3.5 percent of the stage inlet mass flow. The experimental performance of the stage at various operating conditions, including detailed flowfield measurements, are presented and discussed in the context of the computational analyses. The sensitivity of the stage performance and operability to reduced aspiration flow rates at design and off design conditions are also discussed.

  1. Injection molding of high aspect ratio sub-100 nm nanostructures

    DEFF Research Database (Denmark)

    Matschuk, Maria; Larsen, Niels B

    2013-01-01

    with FDTS. Reduced adhesion forces are consistent with lowered friction that reduces the risk of fracturing the nanoscopic pillars during demolding. Optimized mold surface chemistry and associated injection molding conditions permitted the fabrication of square arrays of 40 nm wide and 107 nm high (aspect......We have explored the use of mold coatings and optimized processing conditions to injection mold high aspect ratio nanostructures (height-to-width >1) in cyclic olefin copolymer (COC). Optimizing the molding parameters on uncoated nickel molds resulted in slight improvements in replication quality...

  2. High aspect ratio transmission line circuits micromachined in silicon

    Science.gov (United States)

    Todd, Shane Truman

    The performance of complimentary metal-oxide-semiconductor (CMOS) monolithic microwave integrated circuits (MMICs) fabricated on silicon has improved dramatically. The scaling down of silicon transistors has increased the maximum frequency of transistors to the point where silicon MMICs have become a viable alternative to compound semiconductor MMICs in certain applications. A fundamental problem still exists in silicon MMICs however in that transmission lines fabricated on silicon can suffer from high loss due to the finite conductivity of the silicon substrate. A novel approach for creating low-loss transmission lines on silicon is presented in this work. Low-loss transmission lines are created on low resistivity silicon by using a micromachining method that combines silicon deep reactive ion etching (DRIE), thermal oxidation, electroplating, and planarization. Two types of high aspect ratio transmission lines are created with this method including high aspect ratio coplanar waveguide (hicoplanar) and semi-rectangular coaxial (semicoaxial). Transmission lines with impedances ranging from 20--80 O have been fabricated with minimum measured loss lower than 1 dB/cm at 67 GHz. Low-loss dielectrics are created for the high aspect ratio transmission lines using the mesa merging method. The mesa merging method works by creating silicon mesa arrays using DRIE and then converting and merging the mesa arrays into a solid oxide dielectric using thermal oxidation. The transmission lines are designed so that the fields penetrate the low-loss oxide dielectric and are isolated from the lossy silicon substrate. The mesa merging method has successfully created large volume oxide with depth up to 65 microm and width up to 240 microm in short oxidation times. Other advantages of the high aspect ratio transmission lines are demonstrated including low-loss over a wide impedance range, high isolation, and high coupling for coupled-line circuits. Transmission line models have been

  3. Rapid homogeneous endothelialization of high aspect ratio microvascular networks.

    Science.gov (United States)

    Naik, Nisarga; Hanjaya-Putra, Donny; Haller, Carolyn A; Allen, Mark G; Chaikof, Elliot L

    2015-08-01

    Microvascularization of an engineered tissue construct is necessary to ensure the nourishment and viability of the hosted cells. Microvascular constructs can be created by seeding the luminal surfaces of microfluidic channel arrays with endothelial cells. However, in a conventional flow-based system, the uniformity of endothelialization of such an engineered microvascular network is constrained by mass transfer of the cells through high length-to-diameter (L/D) aspect ratio microchannels. Moreover, given the inherent limitations of the initial seeding process to generate a uniform cell coating, the large surface-area-to-volume ratio of microfluidic systems demands long culture periods for the formation of confluent cellular microconduits. In this report, we describe the design of polydimethylsiloxane (PDMS) and poly(glycerol sebacate) (PGS) microvascular constructs with reentrant microchannels that facilitates rapid, spatially homogeneous endothelial cell seeding of a high L/D (2 cm/35 μm; > 550:1) aspect ratio microchannels. MEMS technology was employed for the fabrication of a monolithic, elastomeric, reentrant microvascular construct. Isotropic etching and PDMS micromolding yielded a near-cylindrical microvascular channel array. A 'stretch - seed - seal' operation was implemented for uniform incorporation of endothelial cells along the entire microvascular area of the construct yielding endothelialized microvascular networks in less than 24 h. The feasibility of this endothelialization strategy and the uniformity of cellularization were established using confocal microscope imaging.

  4. 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.

  5. High aspect ratio channels in glass and porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Liang, H.D. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Nanoscience and Nanotechnology Initiative (NNI), National University of Singapore, Singapore 117411 (Singapore); Dang, Z.Y. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Wu, J.F. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583 (Singapore); Kan, J.A. van; Qureshi, S. [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Ynsa, M.D.; Torres-Costa, V. [Department of Applied Physics, Universidad Autónoma de Madrid, Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Centro de Micro-Análisis de Materiales (CMAM), Universidad Autónoma de Madrid, Campus de Cantoblanco Edif. 22, Faraday 3, E-28049 Madrid (Spain); Maira, A. [Department of Applied Physics, Universidad Autónoma de Madrid, Madrid, Campus de Cantoblanco, 28049 Madrid (Spain); Venkatesan, T.V. [Nanoscience and Nanotechnology Initiative (NNI), National University of Singapore, Singapore 117411 (Singapore); Breese, M.B.H., E-mail: phymbhb@nus.edu.sg [Centre for Ion Beam Applications (CIBA), Department of Physics, National University of Singapore, Singapore 117542 (Singapore)

    2017-03-01

    We have developed a micromachining process to produce high-aspect-ratio channels and holes in glass and porous silicon. Our process utilizes MeV proton beam irradiation of silicon using direct writing with a focused beam, followed by electrochemical etching. To increase throughput we have also developed another process for large area ion irradiation based on a radiation-resistant gold surface mask, allowing many square inches to be patterned. We present a study of the achievable channel width, depth and period and sidewall verticality for a range of channels which can be over 100 μm deep or 100 nm wide with aspect ratios up to 80. This process overcomes the difficulty of machining glass on a micro- and nanometer scale which has limited many areas of applications in different fields such as microelectronics and microfluidics.

  6. High aspect ratio channels in glass and porous silicon

    Science.gov (United States)

    Liang, H. D.; Dang, Z. Y.; Wu, J. F.; van Kan, J. A.; Qureshi, S.; Ynsa, M. D.; Torres-Costa, V.; Maira, A.; Venkatesan, T. V.; Breese, M. B. H.

    2017-03-01

    We have developed a micromachining process to produce high-aspect-ratio channels and holes in glass and porous silicon. Our process utilizes MeV proton beam irradiation of silicon using direct writing with a focused beam, followed by electrochemical etching. To increase throughput we have also developed another process for large area ion irradiation based on a radiation-resistant gold surface mask, allowing many square inches to be patterned. We present a study of the achievable channel width, depth and period and sidewall verticality for a range of channels which can be over 100 μm deep or 100 nm wide with aspect ratios up to 80. This process overcomes the difficulty of machining glass on a micro- and nanometer scale which has limited many areas of applications in different fields such as microelectronics and microfluidics.

  7. Small, high pressure ratio compressor: Aerodynamic and mechanical design

    Science.gov (United States)

    Bryce, C. A.; Erwin, J. R.; Perrone, G. L.; Nelson, E. L.; Tu, R. K.; Bosco, A.

    1973-01-01

    The Small, High-Pressure-Ratio Compressor Program was directed toward the analysis, design, and fabrication of a centrifugal compressor providing a 6:1 pressure ratio and an airflow rate of 2.0 pounds per second. The program consists of preliminary design, detailed areodynamic design, mechanical design, and mechanical acceptance tests. The preliminary design evaluate radial- and backward-curved blades, tandem bladed impellers, impeller-and diffuser-passage boundary-layer control, and vane, pipe, and multiple-stage diffusers. Based on this evaluation, a configuration was selected for detailed aerodynamic and mechanical design. Mechanical acceptance test was performed to demonstrate that mechanical design objectives of the research package were met.

  8. 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.

  9. 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

  10. High aspect ratio 3D nanopatterning using Proton Beam Writing

    Science.gov (United States)

    van Kan, Jeroen A.

    2009-03-01

    Proton beam writing (PBW) is a new direct write lithography using MeV protons, and is unique because of its ability to fabricate 3D structures of high aspect ratio structures directly in resist material like PMMA, SU-8 and HSQ. The introduction by CIBA, Singapore of a dedicated PBW facility, capable of writing at the micro- and nano- scale has facilitated high aspect ratio nanostructuring. PBW has demontrated high aspect ratio walls in HSQ down to the 20nm level. In recent experiments details down to sub 20 nm have been achieved in PMMA. Monte-Carlo calculations have shown that structuring down to the nanometer level is feasible. All this is possible because of the virtual absence of proximity effects (unwanted resist exposure by stray secondary electrons). The design and performance of this unique nanoprobe facility will be discussed. Two potential fields of application (eg nanofluidics and nanowire integration) of PBW will be discussed. Currently nanofluidics devices have typically only one critical dimension below 100 nm. Here we will introduce PBW as a powerful technique to fabricate molds for replication of PDMS nanofluidic circuits down to the sub 100 nm level in two dimensions. Initial chips with dimension down to 150 nm have successfully been used to study DNA folding in quasi-1d nanochannels in tandem with fluorescence imaging. Since the size of these PDMS nanochannels is not limited by the PDMS or PBW further miniaturization down to the sub 100 nm level is a realistic goal and initial results will be discussed. Nanowires are a potential building block for nano-electronic devices, and one critical problem is the integration of nanowires to form contacts. Porous alumina templates and high energy ion-tracks have been used for the production of nanowire templates in a random orientation. Since PBW is the only true 3D direct write nanolithographic technique it can be used to fabricate nanowire templates in a controlled manner.

  11. Dielectric spectroscopy of high aspect ratio graphene-polyurethane nanocomposites

    Science.gov (United States)

    Jan, Rahim; Habib, Amir; Abbassi, Hina; Amir, Shahid

    2015-03-01

    High aspect ratio graphene nanosheets (GNS), prepared via liquid exfoliation, are homogeneously dispersed in thermoplastic polyurethane (TPU). Dielectric spectroscopy results are reported for these nanocomposites (up to 0.55 vol. % GNS) in the frequency range of 100 Hz to 5 MHz. The as-prepared GNS increased the AC conductivity 10-1000 times across the given frequency range. The dielectric constant is increased 5-6 times at 100 Hz for the maximum loading of GNS when compared with the pristine TPU, with subsequently high dielectric loss making them a suitable candidate for high energy dissipation applications such as EMI shielding. The temperature effects on the dielectric characteristics of 0.55 vol. % GNS/TPU nanocomposites beyond 400 K are more pronounced due to the interfacial and orientation polarization. Mechanical characteristics evaluation of GNS/TPU composites shows a marked increase in the ultimate tensile strength without compromising their ductility and stiffness. [Figure not available: see fulltext.

  12. Anomalous dynamic behaviour of optically trapped high aspect ratio nanowires

    CERN Document Server

    Toe, Wen Jun; Angstmann, Christopher; Gao, Qiang; Tan, Hark Hoe; Jagadish, Chennupati; Henry, Bruce; Reece, Peter J

    2015-01-01

    We investigate the dynamics of high aspect ratio nanowires trapped axially in a single gradient force optical tweezers. A power spectrum analysis of the Brownian dynamics reveals a broad spectral resonance of the order of a kHz with peak properties that are strongly dependent on the input trapping power. Modelling of the dynamical equations of motion of the trapped nanowire that incorporate non-conservative effects through asymmetric coupling between translational and rotational degrees of freedom provides excellent agreement with the experimental observations. An associated observation of persistent cyclical motion around the equilibrium trapping position using winding analysis provides further evidence for the influence of non-conservative forces.

  13. High Aspect-Ratio Neural Probes using Conventional Blade Dicing

    Science.gov (United States)

    Goncalves, S. B.; Ribeiro, J. F.; Silva, A. F.; Correia, J. H.

    2016-10-01

    Exploring deep neural circuits has triggered the development of long penetrating neural probes. Moreover, driven by brain displacement, the long neural probes require also a high aspect-ratio shafts design. In this paper, a simple and reproducible method of manufacturing long-shafts neural probes using blade dicing technology is presented. Results shows shafts up to 8 mm long and 200 µm wide, features competitive to the current state-of-art, being its outline simply accomplished by a single blade dicing program. Therefore, conventional blade dicing presents itself as a viable option to manufacture long neural probes.

  14. High frequency wide-band transformer uses coax to achieve high turn ratio and flat response

    Science.gov (United States)

    De Parry, T.

    1966-01-01

    Center-tap push-pull transformer with toroidal core helically wound with a single coaxial cable creates a high frequency wideband transformer. This transformer has a high-turn ratio, a high coupling coefficient, and a flat broadband response.

  15. 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

  16. 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

  17. 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

  18. High extinction ratio bandgap of photonic crystals in LNOI wafer

    Science.gov (United States)

    Zhang, Shao-Mei; Cai, Lu-Tong; Jiang, Yun-Peng; Jiao, Yang

    2017-02-01

    A high-extinction-ratio bandgap of air-bridge photonic crystal slab, in the near infrared, is reported. These structures were patterned in single-crystalline LiNbO3 film bonded to SiO2/LiNbO3 substrate by focused ion beam. To improve the vertical confinement of light, the SiO2 layer was removed by 3.6% HF acid. Compared with photonic crystals sandwiched between SiO2 and air, the structures suspending in air own a robust photonic bandgap and high transmission efficiency at valence band region. The measured results are in good agreement with numerically computed transmission spectra by finite-difference time-domain method. The air-bridge photonic crystal waveguides were formed by removing one line holes. We reveal experimentally the guiding characteristics and calculate the theoretical results for photonic crystal waveguides in LiNbO3 film.

  19. High pressure ratio cryocooler with integral expander and heat exchanger

    Science.gov (United States)

    Crunkleton, J. A.; Smith, J. L., Jr.; Iwasa, Y.

    A new 1 W, 4.2 K cryocooler is under development that is intended to miniaturize helium temperature refrigeration systems using a high-pressure-ratio Collins-type cycle. The configuration resulted from optimization studies of a saturated vapor compression (SCV) cycle that employs miniature parallel-plate heat exchangers. The basic configuration is a long displacer in a close-fitting, thin-walled cylinder. The displacer-to-cylinder gap is the high-pressure passage of the heat exchanger, and the low-pressure passage is formed by a thin tube over the OD of the cylinder. A solenoid-operated inlet valve admits 40 atm helium to the displacer-to-cylinder gap at room temperature, while the solenoid-operated exhaust valve operates at 4 atm. The single-stage cryocooler produces 1 W of refrigeration at 40 K without precooling and at 20 K with liquid nitrogen precooling.

  20. Contrasting Sr isotope ratios in plagioclase from different formations of the mid-Miocene Columbia River Basalt Group

    Science.gov (United States)

    Starkel, W. A.; Wolff, J.; Eckberg, A.; Ramos, F.

    2008-12-01

    Many early Columbia River Basalt flows of the Steens and Imnaha Formations are characterized by abundant, texturally complex, coarse plagioclase phenocrysts. In Imnaha lavas, the feldspars typically have more radiogenic 87Sr/86Sr than whole rock and matrix, and may exhibit complex isotopic zoning that is not correlated with An content. Imnaha plagioclase grains are interpreted as variably-contaminated crystals produced when high-crystallinity mid-crustal basaltic intrusions exchanged interstitial melt with adjacent partly-melted crustal rock; this isotopically variable debris was then remobilized by subsequent intrusion of mantle-derived basalt and brought to the surface as an isotopically heterogeneous mixture. In contrast, plagioclase grains in the texturally very similar Steens lavas are isotopically near-homogeneous and 87Sr/86Sr is not significantly displaced from that of the bulk rock. This is consistent with magma- crust interaction at low degrees of crustal melting during the early stages of the Columbia River flood basalt episode, where Steens and Imnaha lavas were erupted from distinct magma systems hosted by different types of crust that exerted different degrees of isotopic leverage on the mantle-derived magmas [1]. Thermal input to the Steens system declined at the same time as the Imnaha magmatic flux increased to ultimately produce the huge outpouring of Grande Ronde lavas, which are mixtures of mantle- and crust-derived liquids, the latter produced during high degrees of crustal melting during the time of peak magmatic flux. [1] Wolff et al. (2008) Nature Geoscience 1, 177-180.

  1. Noise Measurements of High Aspect Ratio Distributed Exhaust Systems

    Science.gov (United States)

    Bridges, James E.

    2015-01-01

    This paper covers far-field acoustic measurements of a family of rectangular nozzles with aspect ratio 8, in the high subsonic flow regime. Several variations of nozzle geometry, commonly found in embedded exhaust systems, are explored, including bevels, slants, single broad chevrons and notches, and internal septae. Far-field acoustic results, presented previously for the simple rectangular nozzle, showed that increasing aspect ratio increases the high frequency noise, especially directed in the plane containing the minor axis of the nozzle. Detailed changes to the nozzle geometry generally made little difference in the noise, and the differences were greatest at low speed. Having an extended lip on one broad side (bevel) did produce up to 3 decibels more noise in all directions, while extending the lip on the narrow side (slant) produced up to 2 decibels more noise, primarily on the side with the extension. Adding a single, non-intrusive chevron, made no significant change to the noise, while inverting the chevron (notch) produced up to 2decibels increase in the noise. Having internal walls (septae) within the nozzle, such as would be required for structural support or when multiple fan ducts are aggregated, reduced the noise of the rectangular jet, but could produce a highly directional shedding tone from the septae trailing edges. Finally, a nozzle with both septae and a beveled nozzle, representative of the exhaust system envisioned for a distributed electric propulsion aircraft with a common rectangular duct, produced almost as much noise as the beveled nozzle, with the septae not contributing much reduction in noise.

  2. High transformer ratio of multi-channel dielectric wakefield structures

    Science.gov (United States)

    Shchelkunov, Sergey V.; Marshall, Thomas C.; Sotnikov, Gennadij V.; Hirshfield, Jay L.

    2016-09-01

    Dielectric wakefield (DWA) accelerator concepts are receiving attention on account of their promising performance, mechanical simplicity, and anticipated low cost. Interest in DWA physics directed toward an advanced high-gradient accelerator has been enhanced by a finding that some dielectrics can withstand very high fields (>1 GV/m) for the short times during the passage of charged bunches along dielectric-lined channels. In a two-channel structure, a drive bunch train propagates in a first channel, and in the second adjacent channel where a high gradient wakefield develops, a witness bunch is accelerated. Compared with single-channel DWA's, a two-beam accelerator delivers a high transformer ratio, and thereby reduces the number of drive beam sections needed to achieve a given final test beam energy. An overview of multi-channel DWA structures will be given, with an emphasis on two-channel structures, presenting their advantages and drawbacks, and potential impact on the field. Studies aimed to examine charging rate and charge distribution in a thin walled dielectric wakefield accelerator from a passing charge bunch and the physics of conductivity and discharge phenomena in dielectric materials useful for such accelerator applications are presented in a separate paper in the EAAC-2015 conference proceedings.

  3. High transformer ratio of multi-channel dielectric wakefield structures

    Energy Technology Data Exchange (ETDEWEB)

    Shchelkunov, Sergey V., E-mail: sergey.shchelkunov@gmail.com [Omega-P R& D, Inc, CT 06511 (United States); Yale University, CT (United States); Marshall, Thomas C. [Omega-P R& D, Inc, CT 06511 (United States); Sotnikov, Gennadij V. [NSC Kharkov Institute of Physics and Technology, Kharkov (Ukraine); Hirshfield, Jay L. [Omega-P R& D, Inc, CT 06511 (United States)

    2016-09-01

    Dielectric wakefield (DWA) accelerator concepts are receiving attention on account of their promising performance, mechanical simplicity, and anticipated low cost. Interest in DWA physics directed toward an advanced high-gradient accelerator has been enhanced by a finding that some dielectrics can withstand very high fields (>1 GV/m) for the short times during the passage of charged bunches along dielectric-lined channels. In a two-channel structure, a drive bunch train propagates in a first channel, and in the second adjacent channel where a high gradient wakefield develops, a witness bunch is accelerated. Compared with single-channel DWA's, a two-beam accelerator delivers a high transformer ratio, and thereby reduces the number of drive beam sections needed to achieve a given final test beam energy. An overview of multi-channel DWA structures will be given, with an emphasis on two-channel structures, presenting their advantages and drawbacks, and potential impact on the field. Studies aimed to examine charging rate and charge distribution in a thin walled dielectric wakefield accelerator from a passing charge bunch and the physics of conductivity and discharge phenomena in dielectric materials useful for such accelerator applications are presented in a separate paper in the EAAC-2015 conference proceedings.

  4. Comparison between pulsed laser and frequency-domain photoacoustic modalities: Signal-to-noise ratio, contrast, resolution, and maximum depth detectivity

    Science.gov (United States)

    Lashkari, Bahman; Mandelis, Andreas

    2011-09-01

    In this work, a detailed theoretical and experimental comparison between various key parameters of the pulsed and frequency-domain (FD) photoacoustic (PA) imaging modalities is developed. The signal-to-noise ratios (SNRs) of these methods are theoretically calculated in terms of transducer bandwidth, PA signal generation physics, and laser pulse or chirp parameters. Large differences between maximum (peak) SNRs were predicted. However, it is shown that in practice the SNR differences are much smaller. Typical experimental SNRs were 23.2 dB and 26.1 dB for FD-PA and time-domain (TD)-PA peak responses, respectively, from a subsurface black absorber. The SNR of the pulsed PA can be significantly improved with proper high-pass filtering of the signal, which minimizes but does not eliminate baseline oscillations. On the other hand, the SNR of the FD method can be enhanced substantially by increasing laser power and decreasing chirp duration (exposure) correspondingly, so as to remain within the maximum permissible exposure guidelines. The SNR crossover chirp duration is calculated as a function of transducer bandwidth and the conditions yielding higher SNR for the FD mode are established. Furthermore, it was demonstrated that the FD axial resolution is affected by both signal amplitude and limited chirp bandwidth. The axial resolution of the pulse is, in principle, superior due to its larger bandwidth; however, the bipolar shape of the signal is a drawback in this regard. Along with the absence of baseline oscillation in cross-correlation FD-PA, the FD phase signal can be combined with the amplitude signal to yield better axial resolution than pulsed PA, and without artifacts. The contrast of both methods is compared both in depth-wise (delay-time) and fixed delay time images. It was shown that the FD method possesses higher contrast, even after contrast enhancement of the pulsed response through filtering.

  5. 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.

  6. 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.

  7. Improving acousto-optical interaction by high aspect ratio electrodes

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard

    In recent years experiments have shown that optical waves in waveguides can be modulated by mechanical stresses from surface acoustic waves (SAW), which have most of their energy density concentrated at the surface. In these experiments the SAWs are generated in piezoelectric materials...... by conventional interdigital transducers consisting of thin electrodes deposited at the surface. In this work the finite element method is employed to investigate if the acousto-optical interaction can be enhanced by generating the SAWs by interdigital transducers consisting of high aspect ratio electrodes....... With a periodic model it is first shown that these tall electrodes introduce several new confined SAW modes with slow phase velocities because of mechanical energy storage in the electrodes. The periodic model is then extended to a finite model by using perfectly matched layers at the substrate borders...

  8. The Dynamic Behaviour of Gears with High Transmission Ratio

    Directory of Open Access Journals (Sweden)

    Ivana Atanasovska

    2012-06-01

    Full Text Available This paper describes the dynamic behaviour of helical gears with new standpoint for calculation of influence variables: mesh teeth stiffness, contact lines lengths and load distribution during mesh period. Nonlinear contact Finite Element Analysis and the new iteration procedure are used for calculation of meshed teeth deformations, stiffness and contact loads. The normal load distribution calculated with this procedure is used for evaluation of nonlinear dynamic analytical model of helical gears motion. Described investigation is especially important for gear pairs with high value of transmission ratio, often used in large transport machines. The presented models and results can be used for helical gears modeling when standard procedures don’t cover the requirements.

  9. Comparison of contrast-to-noise ratios of transmission and dark-field signal in grating-based X-ray imaging for healthy murine lung tissue

    Energy Technology Data Exchange (ETDEWEB)

    Schwab, Felix [Ludwig Maximilians-Univ. Hospital Munich (Germany). Inst. for Clinical Radiology; Schleede, Simone; Hahn, Dieter [Technische Univ. Muenchen, Garching (Germany). Dept. of Physics and Inst. of Medical Engineering] [and others

    2013-10-01

    Purpose: An experimental comparison of the contrast-to-noise ratio (CNR) between transmission and dark-field signals in grating-based X-ray imaging for ex-vivo murine lung tissue. Materials and Methods: Lungs from three healthy mice were imaged ex vivo using a laser-driven compact synchrotron X-ray source. Background noise of transmission and dark-field signal was quantified by measuring the standard deviation in a region of interest (ROI) placed in a homogeneous area outside the specimen. Image contrast was quantified by measuring the signal range in rectangular ROIs placed in central and peripheral lung parenchyma. The relative contrast gain (RCG) of dark-field over transmission images was calculated as CNRDF / CNRT. Results: In all images, there was a trend for contrast-to-noise ratios of dark-field images (CNRDF) to be higher than for transmission images (CNRT) for all ROIs (median 61 vs. 38, p = 0.10), but the difference was statistically significant only for peripheral ROIs (61 vs. 32, p = 0.03). Median RCG was >1 for all ROIs (1.84). RCG values were significantly smaller for central ROIs than for peripheral ROIs (1.34 vs. 2.43, p = 0.03). Conclusion: The contrast-to-noise ratio of dark-field images compares more favorably to the contrast-to-noise ratio of transmission images for peripheral lung regions as compared to central regions. For any specific specimen, a calculation of the RCG allows comparing which X-ray modality (dark-field or transmission imaging) produces better contrast-to-noise characteristics in a well-defined ROI. (orig.)

  10. Influence of x-ray energy spectrum, contrasting detail and detector on the signal-to-noise ratio (SNR) and detective quantum efficiency (DQE) in projection radiography

    Energy Technology Data Exchange (ETDEWEB)

    Sandborg, Michael; Carlsson, G.A. (Linkoeping Univ. (Sweden). Dept. of Radiation Physics)

    1992-06-01

    A lower limit to patient irradiation in diagnostic radiology is set by the fundamental stochastics of the energy imparted to the image receptor (quantum noise). Image quality is investigated here and expressed in terms of the signal-to-noise ratio due to quantum noise. The Monte Carlo method is used to calculate signal-to-noise ratios (SNR{sub {Delta}S}) and detective quantum efficiencies (DQE{sub {Delta}S}) in imaging thin contrasting details of air, fat, bone and iodine within a water phantom using x-ray spectra (40-140 kV) and detectors of CsI, BaFCl and Gd{sub 2}O{sub 2}S. The atomic composition of the contrasting detail influences considerably the values of SNR{sub {Delta}S} due to the different modulations of the energy spectra of primary photons passing beside and through the contrasting detail. (author).

  11. Photoimageable Polyimide: A Dielectric Material For High Aspect Ratio Structures

    Science.gov (United States)

    Cech, Jay M.; Oprysko, Modest M.; Young, Peter L.; Li, Kin

    1986-07-01

    Polyimide has been identified as a useful material for microelectronic packaging because of its low dielectric constant and high temperature stability. Difficulties involved with reactive ion etching (RIE), a conventional technique for patterning thick polyimide films (thickness greater than 5 microns) with vertical walls, can be overcome by using photimageable polyimide precursors. The processing steps are similar to those used with negative photoresists. EM Chemical's HTR-3 photosensitive polyimide has been spun on up to a thickness of 12 microns. Exposure with a dose of 780 mJcm-2 of ultraviolet light, followed by spin development produces clean patterns as small as 5 microns corresponding to an aspect ratio of 2.4. When the patterned precursor is heated, an imidization reaction occurs converting the patterned film to polyimide. Baking to ca. 400 degrees C results in substantial loss in the thickness and in line width. However, shrinkage occurs reproducibly so useful rules for mask design can be formulated. Near vertical wall structures can be fabricated by taking advantage of the optical and shrinkage properties of the polyimide precursor. After development, an undercut wall profile can be produced since the bottom of the film receives less exposure and is hence more soluble in the developer. During heating, lateral shrinkage pulls the top of the film inward producing a vertical wall since the bottom is fixed to the substrate by adhesion. As a result, fully cured polyimide structures with straight walls and aspect ratios greater than one can be obtained. Dielectric properties of the fully imidized films were investigated with capacitor test structures. A relative dielectric constant of 3.3 and a loss tangent of .002 were measured at 20 kHz. It was also found that the dielectric constant increases as a linear function of relative humidity.

  12. A high pressure ratio DC compressor for tactical cryocoolers

    Science.gov (United States)

    Chen, Weibo; Cameron, Benjamin H.; Zagarola, Mark V.; Narayanan, Sri R.

    2016-05-01

    A high pressure ratio DC compressor is a critical component for many cryocooler cycles. Prior research has focused on the adaptation of commercial compressor technology (scroll, screw, linear with rectification valves, and regenerative) for use in cryogenic applications where long-life and oil-free (i.e., volatile contamination free) are unique requirements. In addition, many cryocooler applications are for cooling imaging instruments making low vibration an additional requirement. Another candidate compressor technology has emerged from the fuel cell industry. Proton Exchange Membranes (PEMs) are used in fuel cells to separate reactants and transport protons, and these capabilities may be used in cryocoolers to compress hydrogen from low to high pressure. A particular type of PEM utilizing an anhydrous membrane forms the basis of a solid-state cryocooler. Creare has been investigating the use of PEM compressors for low temperature Joule-Thomson and dilution cryocoolers. These cryocoolers have no moving parts, can operate at temperatures down to nominally 23 K, produce no vibration, and are low cost. Our work on the cycle optimization, cryocooler design, and development and demonstration of the compressor technology is the subject of this paper.

  13. Comparing CO2 flux data from eddy covariance methods with bowen ratio energy balance methods from contrasting soil management

    Science.gov (United States)

    Measuring CO2 fluxes from contrasting soil management practices is important for understanding the role of agriculture in source-sink relationship with CO2 flux. There are several micrometeorological methods for measuring CO2 emissions, however all are expensive and thus do not easily lend themselve...

  14. High signal-to-noise ratio quantum well bolometer materials

    Science.gov (United States)

    Wissmar, Stanley; Höglund, Linda; Andersson, Jan; Vieider, Christian; Savage, Susan; Ericsson, Per

    2006-09-01

    Novel single crystalline high-performance temperature sensing materials (quantum well structures) have been developed for the manufacturing of uncooled infrared bolometers. SiGe/Si and AlGaAs/GaAs quantum wells are grown epitaxially on standard Si and GaAs substrates respectively. The former use holes as charge carriers utilizing the discontinuities in the valence band structure, whereas the latter operate in a similar manner with electrons in the conduction band. By optimizing parameters such as the barrier height (by variation of the germanium/aluminium content respectively) and the fermi level E f (by variation of the quantum well width and doping level) these materials provide the potential to engineer layer structures with a very high temperature coefficient of resistance, TCR, as compared with conventional thin film materials such as vanadium oxide and amorphous silicon. In addition, the high quality crystalline material promises very low 1/f-noise characteristics promoting an outstanding signal to noise ratio and well defined and uniform material properties, A comparison between the two (SiGe/Si and AlGaAs/GaAs) quantum well structures and their fundamental theoretical limits are discussed and compared to experimental results. A TCR of 2.0%/K and 4.5%/K have been obtained experimentally for SiGe/Si and AlGaAs/GaAs respectively. The noise level for both materials is measured as being several orders of magnitude lower than that of a-Si and VOx. These uncooled thermistor materials can be hybridized with read out circuits by using conventional flip-chip assembly or wafer level adhesion bonding. The increased bolometer performance so obtained can either be exploited for increasing the imaging system performance, i. e. obtaining a low NETD, or to reduce the vacuum packaging requirements for low cost applications (e.g. automotive).

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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...

  20. 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.

  1. New microangiography system development providing improved small vessel imaging, increased contrast to noise ratios, and multi-view 3D reconstructions.

    Science.gov (United States)

    Kuhls, Andrew T; Patel, Vikas; Ionita, Ciprian; Noël, Peter B; Walczak, Alan M; Rangwala, Hussain S; Hoffmann, Kenneth R; Rudin, Stephen

    2006-01-01

    A new microangiographic system (MA) integrated into a c-arm gantry has been developed allowing precise placement of a MA at the exact same angle as the standard x-ray image intensifier (II) with unchanged source and object position. The MA can also be arbitrarily moved about the object and easily moved into the field of view (FOV) in front of the lower resolution II when higher resolution angiographic sequences are needed. The benefits of this new system are illustrated in a neurovascular study, where a rabbit is injected with contrast media for varying oblique angles. Digital subtraction angiographic (DSA) images were obtained and compared using both the MA and II detectors for the same projection view. Vessels imaged with the MA appear sharper with smaller vessels visualized. Visualization of ~100 μm vessels was possible with the MA whereas not with the II. Further, the MA could better resolve vessel overlap. Contrast to noise ratios (CNR) were calculated for vessels of varying sizes for the MA versus the II and were found to be similar for large vessels, approximately double for medium vessels, and infinitely better for the smallest vessels. In addition, a 3D reconstruction of selected vessel segments was performed, using multiple (three) projections at oblique angles, for each detector. This new MA/II integrated system should lead to improved diagnosis and image guidance of neurovascular interventions by enabling initial guidance with the low resolution large FOV II combined with use of the high resolution MA during critical parts of diagnostic and interventional procedures.

  2. Contrast-to-noise ratio with different settings in a CBCT machine in presence of different root-end filling materials: an in vitro study.

    Science.gov (United States)

    Demirturk Kocasarac, Husniye; Helvacioglu Yigit, Dilek; Bechara, Boulos; Sinanoglu, Alper; Noujeim, Marcel

    2016-01-01

    To compare the contrast-to-noise ratio (CNR) of multiple acquisition settings for four types of retrograde filling materials in CBCT images taken for endodontic surgery follow-up. 20 maxillary central incisors were endodontically treated and obturated with 4 different root-end filling materials: amalgam, mineral trioxide aggregate, SuperEBA(™) (Harry J Bosworth Company, Skokie, IL) and Biodentine™ (Septodont, Saint-Maur-des-Faussés, France). Teeth were placed in a skull and scanned, one by one, with the Planmeca ProMax(®) 3D Max (Planmeca, Helsinki, Finland); at different voltages: 66, 76, 84 and 96 kVp; with low, normal and high resolution and high definition (HD); with and without metal artefact reduction (MAR). Images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the CNR. The dose-area product was registered, and the effective dose calculated. No statistically significant difference was noted between the four materials. 84 and 96 kVp with low resolution and the use of MAR-generated images that have statistically better CNR than 66 and 76 kVp with HD, normal and high resolutions and without MAR. The use of low resolution also generated the smallest value of effective dose. The best setting for radiographic follow-up in an endodontic surgery with retrograde filling on the Planmeca ProMax is 96 kVp with low resolution and high MAR; this setting produced one of the lowest effective doses.

  3. Aerodynamic Properties of Rough Surfaces with High Aspect-Ratio Roughness Elements: Effect of Aspect Ratio and Arrangements

    Science.gov (United States)

    Sadique, Jasim; Yang, Xiang I. A.; Meneveau, Charles; Mittal, Rajat

    2017-05-01

    We examine the effect of varying roughness-element aspect ratio on the mean velocity distributions of turbulent flow over arrays of rectangular-prism-shaped elements. Large-eddy simulations (LES) in conjunction with a sharp-interface immersed boundary method are used to simulate spatially-growing turbulent boundary layers over these rough surfaces. Arrays of aligned and staggered rectangular roughness elements with aspect ratio >1 are considered. First the temporally- and spatially-averaged velocity profiles are used to illustrate the aspect-ratio effects. For aligned prisms, the roughness length (z_o) and the friction velocity (u_*) increase initially with an increase in the roughness-element aspect ratio, until the values reach a plateau at a particular aspect ratio. The exact value of this aspect ratio depends on the coverage density. Further increase in the aspect ratio changes neither z_o, u_* nor the bulk flow above the roughness elements. For the staggered cases, z_o and u_* continue to increase for the surface coverage density and the aspect ratios investigated. To model the flow response to variations in roughness aspect ratio, we turn to a previously developed phenomenological volumetric sheltering model (Yang et al., in J Fluid Mech 789:127-165, 2016), which was intended for low to moderate aspect-ratio roughness elements. Here, we extend this model to account for high aspect-ratio roughness elements. We find that for aligned cases, the model predicts strong mutual sheltering among the roughness elements, while the effect is much weaker for staggered cases. The model-predicted z_o and u_* agree well with the LES results. Results show that the model, which takes explicit account of the mutual sheltering effects, provides a rapid and reliable prediction method of roughness effects in turbulent boundary-layer flows over arrays of rectangular-prism roughness elements.

  4. 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.

  5. 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.

  6. 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.

  7. 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...

  8. 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.

  9. Long-term dynamics of high mass ratio multiples

    Science.gov (United States)

    Li, Gongjie

    This thesis presents a series of studies on the dynamics of high mass ratio multiples, with applications to planetary systems orbiting stars and stellar systems orbiting supermassive black holes (SMBHs). Almost two thousand exoplanetary systems have recently been discovered, and their configurations gave rise to new puzzles to planetary formation theories. We studied the dynamics of planetary systems aiming to understand how the configuration of planetary system is sculptured and to probe the origin of planetary systems. First, we discussed hierarchical three-body dynamics, which can be applied to planets that are orbiting a star while perturbed by a planet or a star that is farther away. The perturbation from the farther object can flip the planetary orbits and produce counter orbiting hot Jupiters, which cannot be formed in the classical planetary formation theory. In addition, we have studied the scatter encounter of planetary systems in clusters, which produce eccentric and inclined planets. Moreover, we investigated the obliquity variation of planets, which can be applied to exoplanetary systems. The obliquity variation is important to the habitability of the exoplanets. The long term dynamics is also important to stellar systems orbiting SMBHs. SMBHs are common in the center of galaxies and lead to rich dynamical interactions with nearby stars. At the same time, dynamical features of the nearby stars reveal important properties of the SMBHs. The aforementioned hierarchical three-body dynamics can be applied to stars near SMBH binaries, which are natural consequences of galaxy mergers. We found that the distribution of stars surrounding one of the SMBHs results in a shape of torus due to the perturbation from the other SMBH, and the dynamical interactions contribute to an enhancement of tidal disruption rates, which can help identify the SMBH binaries. In addition, we investigated the heating of stars near SMBHs, where the heating of stars due to gravitational

  10. 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...

  11. Assessment of monocyte to high density lipoprotein cholesterol ratio and lymphocyte-to-monocyte ratio in patients with metabolic syndrome.

    Science.gov (United States)

    Vahit, Demir; Mehmet, Kadri Akboga; Samet, Yilmaz; Hüseyin, Ede

    2017-07-01

    We aimed to investigate the relationships between metabolic syndrome (MS) and monocyte to high density lipoprotein cholesterol ratio (MHR) and lymphocyte-to-monocyte ratio (LMR). 762 patients (n = 371 MS present and n = 391 MS absent) were enrolled. MHR was significantly higher [13.9 (10.5-18.1) vs 11.1 (8.0-14.8); p MHR [OR: 1.052 (95% CI: 1.018-1.088); p = 0.003] and C-reactive protein [OR: 1.048 (95% CI: 1.032-1.065); p MHR may be novel and useful indicators of MS.

  12. 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.

  13. Low power very high frequency resonant converter with high step down ratio

    DEFF Research Database (Denmark)

    Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

    2013-01-01

    This paper presents the design of a resonant converter with a switching frequency in the very high frequency range (30-300MHz), a large step down ratio and low output power. This gives the designed converters specifications which are far from previous results. The class E inverter and rectifier...

  14. High-Temperature CO2 Sorption on Hydrotalcite Having a High Mg/Al Molar Ratio.

    Science.gov (United States)

    Kim, Suji; Jeon, Sang Goo; Lee, Ki Bong

    2016-03-09

    Hydrotalcites having a Mg/Al molar ratio between 3 and 30 have been synthesized as promising high-temperature CO2 sorbents. The existence of NaNO3 in the hydrotalcite structure, which originates from excess magnesium nitrate in the precursor, markedly increases CO2 sorption uptake by hydrotalcite up to the record high value of 9.27 mol kg(-1) at 240 °C and 1 atm CO2.

  15. 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

  16. A low volumetric exchange ratio allows high autotrophic nitrogen removal in a sequencing batch reactor.

    Science.gov (United States)

    De Clippeleir, Haydée; Vlaeminck, Siegfried E; Carballa, Marta; Verstraete, Willy

    2009-11-01

    Sequencing batch reactors (SBRs) have several advantages, such as a lower footprint and a higher flexibility, compared to biofilm based reactors, such as rotating biological contactors. However, the critical parameters for a fast start-up of the nitrogen removal by oxygen-limited autotrophic nitrification/denitrification (OLAND) in a SBR are not available. In this study, a low critical minimum settling velocity (0.7 m h(-1)) and a low volumetric exchange ratio (25%) were found to be essential to ensure a fast start-up, in contrast to a high critical minimum settling velocity (2 m h(-1)) and a high volumetric exchange ratio (40%) which yielded no successful start-up. To prevent nitrite accumulation, two effective actions were found to restore the microbial activity balance between aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB). A daily biomass washout at a critical minimum settling velocity of 5 m h(-1) removed small aggregates rich in AerAOB activity, and the inclusion of an anoxic phase enhanced the AnAOB to convert the excess nitrite. This study showed that stable physicochemical conditions were needed to obtain a competitive nitrogen removal rate of 1.1 g N L(-1) d(-1).

  17. 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.

  18. Maintaining high-Q in an optical microresonator coated with high-aspect-ratio gold nanorods

    Science.gov (United States)

    Ganta, D.; Dale, E. B.; Rosenberger, A. T.

    2013-10-01

    We report methods to coat fused-silica microresonators with solution-grown high-aspect-ratio (AR) gold nanorods (NRs). Microresonators coated using our method maintain an optical quality factor (Q) greater than 107 after coating. The more successful method involves silanization of the surface of the microresonator with 3-mercaptopropylmethyldimethoxysilane (MPMDMS), to enable the adhesion of gold NRs. The high-AR NR-coated microresonator combines the field enhancement of localized surface plasmon resonances with the cavity-enhanced evanescent components of high-Q whispering-gallery modes, making it useful for plasmonic sensing applications in the infrared. By coating with NRs having a different aspect ratio, the enhancement regime can be selected within a wide range of wavelengths.

  19. High-performance deployable structures for the support of high-concentration ratio solar array modules

    Science.gov (United States)

    Mobrem, M.

    1985-01-01

    A study conducted on high-performance deployable structures for the support of high-concentration ratio solar array modules is discussed. Serious consideration is being given to the use of high-concentration ratio solar array modules or applications such as space stations. These concentrator solar array designs offer the potential of reduced cost, reduced electrical complexity, higher power per unit area, and improved survivability. Arrays of concentrators, such as the miniaturized Cassegrainian concentrator modules, present a serious challenge to the structural design because their mass per unit area (5.7 kg/square meters) is higher than that of flexible solar array blankets, and the requirement for accurate orientation towards the Sun (plus or minus 0.5 degree) requires structures with improved accuracy potentials. In addition, use on a space station requires relatively high structural natural frequencies to avoid deleterious interactions with control systems and other large structural components. The objective here is to identify and evaluate conceptual designs of structures suitable for deploying and accurately supporting high-concentration ratio solar array modules.

  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. 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....

  2. 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.

  3. 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.

  4. Likelihood ratio based verification in high dimensional spaces

    NARCIS (Netherlands)

    Hendrikse, Anne; Veldhuis, Raymond; Spreeuwers, Luuk

    2013-01-01

    The increase of the dimensionality of data sets often lead to problems during estimation, which are denoted as the curse of dimensionality. One of the problems of Second Order Statistics (SOS) estimation in high dimensional data is that the resulting covariance matrices are not full rank, so their i

  5. Likelihood ratio based verification in high dimensional spaces

    NARCIS (Netherlands)

    Hendrikse, A.J.; Veldhuis, Raymond N.J.; Spreeuwers, Lieuwe Jan

    The increase of the dimensionality of data sets often lead to problems during estimation, which are denoted as the curse of dimensionality. One of the problems of Second Order Statistics (SOS) estimation in high dimensional data is that the resulting covariance matrices are not full rank, so their

  6. 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....

  7. 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.

  8. Correlation between dynamic contrast-enhanced MRI and histopathology in the measurement of tumor and breast volume and their ratio in breast cancer patients: a prospective study

    Institute of Scientific and Technical Information of China (English)

    LIU Qian; YE Jing-ming; XU Ling; DUAN Xue-ning; ZHAO Jian-xin; LIU Yin-hua

    2012-01-01

    Background Earlier studies have examined the association between the diameter of primary tumors measured by magnetic resonance imaging (MRI) and histopathology in breast cancer patients.However,the diameter does not completely describe the dimensions of the breast tumor or its volumetric proportion relative to the whole breast.The association between breast tumor volume/breast volume ratios measured by these two techniques has not been reported.Methods Seventy-three patients were recruited from female patients with primary breast tumors admitted to our center between January and December 2010.They were divided into two groups.Group A (n=46) underwent modified radical mastectomy (MRM),and Group B (n=27) underwent preoperative neoadjuvant chemotherapy before MRM.They were examined by dynamic-contrast enhanced MRI (DCE-MRI) to measure breast volumes (BVs),tumor volumes (TVs),and tumor volume/breast volume ratios (TV/BV).These measurements were compared with histopathology results after MRM,and the associations between MRI and pathology were analyzed by linear regression and Bland-Altman analysis.Results For Group A,the correlation coefficients for BVs,TVs,and TV/BV ratios measured by the two techniques were 0.938,0.921,and 0.897 (all P <0.001),respectively.For Group B,the correlation coefficients for BVs,TVs,and TV/BV ratios were 0.936,0.902,and 0.869 (all P<0.01),respectively.The results suggest statistically significant correlations between these parameters measured by the two techniques for both groups.Conclusion For these patients,BVs,TVs,and TV/BV ratios measured by DCE-MRI significantly correlated with those determined by histopathology.

  9. High yield polyol synthesis of round- and sharp-end silver nanowires with high aspect ratio

    Energy Technology Data Exchange (ETDEWEB)

    Nekahi, A.; Marashi, S.P.H., E-mail: pmarashi@aut.ac.ir; Fatmesari, D. Haghshenas

    2016-12-01

    Long silver nanowires (average length of 28 μm, average aspect ratio of 130) with uniform diameter along their length were produced by polyol synthesis of AgNO{sub 3} in ethylene glycol in the presence of PVP as preferential growth agent. Nanowires were produced with no addition of chloride salts such as NaCl or CuCl{sub 2} (or other additives such as Na{sub 2}S) which are usually used for lowering reduction rate of Ag ions by additional etchant of O{sub 2}/Cl{sup −}. Lower reduction rate was obtained by increasing the injection time of PVP and AgNO{sub 3} solutions, which was the significant factor in the formation of nanowires. Therefore, there was enough time for reduced Ag atoms to be deposited preferentially in the direction of PVP chains, resulting in high yield (the fraction of nanowires in the products) of nanowires (more than 95%) with high aspect ratio. The produced nanowires had both round- and sharp-ends with pentagonal cross section. Higher energy level of Ag atoms in borders of MTPs, which increases the dissolution rate of precipitated atoms, in addition to partial melting of MTPs at high synthesis temperatures, leads to the curving of the surfaces of exposed (111) crystalline planes in some MTPs and the formation of round-end silver nanowires. - Highlights: • Long silver nanowires with high aspect ratio of 130 were produced. • More than 95% nanowires were produced in products. • The produced nanowires had round- and sharp-ends with pentagonal cross section. • Additives were needed neither for high yield synthesis nor for round-end nanowires. • Melting and etching of MTPs in high energy borders resulted to round-end nanowires.

  10. Hot punching of high-aspect-ratio 3D polymeric microstructures for drug delivery

    DEFF Research Database (Denmark)

    Petersen, Ritika Singh; Keller, Stephan Sylvest; Boisen, Anja

    2015-01-01

    Hot punching: a highly versatile method of fabricating high-aspect-ratio 3D microstructures for drug delivery with good replication fidelity and yield.......Hot punching: a highly versatile method of fabricating high-aspect-ratio 3D microstructures for drug delivery with good replication fidelity and yield....

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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).

  16. High aspect ratio MEMS capacitor for high frequency impedance matching applications

    DEFF Research Database (Denmark)

    Yalcinkaya, Arda Deniz; Jensen, Søren; Hansen, Ole

    2003-01-01

    We present a microelectromechanical tunable capacitor with a low control voltage, a wide tuning range and adequate electrical quality factor. The device is fabricated in a single-crystalline silicon layer using deep reactive ion etching (DRIE) for obtaining high-aspect ratio (> 20) parallel comb-...... response and it was found that the device is a suitable passive component to be used in impedance matching applications, band-pass filtering or voltage controlled oscillators in the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands.......We present a microelectromechanical tunable capacitor with a low control voltage, a wide tuning range and adequate electrical quality factor. The device is fabricated in a single-crystalline silicon layer using deep reactive ion etching (DRIE) for obtaining high-aspect ratio (> 20) parallel comb......-drive structures with vertical sidewalls. The process sequence for fabrication of the devices uses only one lithographic masking step and can be completed in a short time. The fabricated device was characterized with respect to electrical quality factor, tuning range, self-resonance frequency and transient...

  17. 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...

  18. 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...

  19. Dielectrophoretically structured piezoelectric composites with high aspect ratio piezoelectric particles inclusions

    NARCIS (Netherlands)

    Ende, D.A. van den; Kempen, S.E. van; Wu, X.; Groen, W.A.; Randall, C.A.; Zwaag, S. van der

    2012-01-01

    Piezoelectric composites were prepared by dielectrophoretic alignment of high aspect ratio piezoelectric particles in a thermosetting polymer matrix. A high level of alignment was achieved in the cured composite from a resin containing randomly oriented high aspect ratio particles. Upon application

  20. 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

  1. Large-Area High Aspect Ratio Plasmonic Interference Lithography Utilizing a Single High-k Mode.

    Science.gov (United States)

    Chen, Xi; Yang, Fan; Zhang, Cheng; Zhou, Jing; Guo, L Jay

    2016-04-26

    Plasmonic lithography, which utilizes subwavelength confinement of surface plasmon polartion (SPP) waves, has the capability of breaking the diffraction limit and delivering high resolution. However, all previously reported results suffer from critical issues, such as shallow pattern depth and pattern nonuniformity even over small exposure areas, which limit the application of the technology. In this work, periodic patterns with high aspect ratios and a half-pitch of about 1/6 of the wavelength were achieved with pattern uniformity in square centimeter areas. This was accomplished by designing a special mask and photoresist (PR) system to select a single high spatial frequency mode and incorporating the PR into a waveguide configuration to ensure uniform light exposure over the entire depth of the photoresist layer. In addition to the experimental progress toward large-scale applications of plasmonic interference lithography, the general criteria of designing such an exposure system is also discussed, which can be used for nanoscale fabrication in this fashion for various applications with different requirements for wavelength, pitch, aspect ratio, and structure.

  2. Intensity ratio measurements for density sensitive lines of highly charged Fe ions

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Safdar, E-mail: safdaruetian@gmail.com; Shimizu, Erina [Institute for Laser Science, The University of Electro-Communications (Japan); Sakaue, Hiroyuki A.; Kato, Daiji; Murakami, Izumi [National Institute for Fusion Science (Japan); Yamamoto, Norimasa [Chubu University (Japan); Hara, Hirohisa; Watanabe, Tetsuya [The Graduate University of Advanced Studies (SOKENDAI) (Japan); Nakamura, Nobuyuki, E-mail: n-nakamu@ils.uec.ac.jp [Institute for Laser Science, The University of Electro-Communications (Japan)

    2015-11-15

    Intensity ratio of density sensitive emission lines emitted from Fe ions in the extreme ultraviolet region is important for astrophysics applications. We report high-resolution intensity ratio measurements for Fe ions performed at Tokyo EBIT laboratory by employing a flat-field grazing incidence spectrometer. The experimental intensity ratios of Fe X and Fe XII are plotted as a function of electron density for different electron beam currents. The experimental results are compared with the predicted intensity ratios from the model calculations.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Seasonal changes in H/V spectral ratio at high-latitude seismic stations

    Science.gov (United States)

    Lee, R. F.; Abbott, R. E.; Knox, H. A.; Pancha, A.

    2014-12-01

    We present results demonstrating seasonal variations in the Horizontal-to-Vertical Spectral Ratio (HVSR) at high-latitude seismic stations. We analyze data from two sites at Poker Flat Research Range, near Fairbanks, Alaska. From the first site, we analyze 3 stations installed by Sandia National Labs (SNL) in a valley with marshy summer conditions. We also analyze the PASSCAL Instrument Center station PIC2, which is installed on rock approximately 3.2 km from the SNL stations. These stations continuously record data at 125 (SNL) and 200 (PIC2) samples per second. Seasonal changes in HVSR at high frequencies (> 20 Hz) appear to be caused by impedance contrasts between frozen and thawed ground. Thawed active layers are known to have slower shear-wave velocities than frozen layers or bedrock. An estimate of active layer thickness at each station is obtained from the quarter-wavelength approximation. We verify the accuracy of this technique by obtaining ground-truth measurements at the sites for both thickness and shear-wave velocity. We use physical probing for the thickness measurements and active-source Refraction-Microtremor (ReMi) surveys for the shear-wave velocities. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000

  8. 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

  9. 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)

  10. 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.

  11. Highly sensitive glucose biosensor based on Au-Ni coaxial nanorod array having high aspect ratio.

    Science.gov (United States)

    Hsu, Che-Wei; Wang, Gou-Jen

    2014-06-15

    An effective glucose biosensor requires a sufficient amount of GOx immobilizing on the electrode surface. An electrode of a 3D nanorod array, having a larger surface-to-volume ratio than a 2D nanostructure, can accommodate more GOx molecules to immobilize onto the surface of the nanorods. In this study, a highly sensitive Au-Ni coaxial nanorod array electrode fabricated through the integration of nano electroforming and immersion gold (IG) method for glucose detection was developed. The average diameter of the as-synthesized Ni nanorods and that of the Au-Ni nanorods were estimated to be 150 and 250 nm, respectively; both had a height of 30 μm. The aspect ratio was 120. Compared to that of a flat Au electrode, the effective sensing area was enhanced by 79.8 folds. Actual glucose detections demonstrated that the proposed Au-Ni coaxial nanorod array electrode could operate in a linear range of 27.5 μM-27.5mM with a detection limit of 5.5μM and a very high sensitivity of 769.6 μA mM(-1)cm(-2). Good selectivity of the proposed sensing device was verified by sequential injections of uric acid (UA) and ascorbic acid (AA). Long-term stability was examined through successive detections over a period of 30 days.

  12. A wearable, highly stable, strain and bending sensor based on high aspect ratio graphite nanobelts

    Science.gov (United States)

    Alaferdov, A. V.; Savu, R.; Rackauskas, T. A.; Rackauskas, S.; Canesqui, M. A.; de Lara, D. S.; Setti, G. O.; Joanni, E.; de Trindade, G. M.; Lima, U. B.; de Souza, A. S.; Moshkalev, S. A.

    2016-09-01

    A simple and scalable method was developed for the fabrication of wearable strain and bending sensors, based on high aspect ratio (length/thickness ˜103) graphite nanobelt thin films deposited by a modified Langmuir-Blodgett technique onto flexible polymer substrates. The sensing mechanism is based on the changes in contact resistance between individual nanobelts upon substrate deformation. Very high sensor response stability for more than 5000 strain-release cycles and a device power consumption as low as 1 nW were achieved. The device maximum stretchability is limited by the metal electrodes and the polymer substrate; the maximum strain that could be applied to the polymer used in this work was 40%. Bending tests carried out for various radii of curvature demonstrated distinct sensor responses for positive and negative curvatures. The graphite nanobelt thin flexible films were successfully tested for acoustic vibration and heartbeat sensing.

  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. High on/off ratio ns laser pulses for a triggered single-photon source

    CERN Document Server

    Jin, Gang; He, Jun; Wang, Junmin

    2016-01-01

    852nm nano-second laser pulse chain with a high on/off ratio is generated via chopping a continuous-wave laser beam by using of a Mach-Zehnder-type electro-optic intensity modulator (MZ-EOIM). Detailed analysis and dependence of the on/off ratio on the splitting ratio, the co-splitting ratio, and the arms loss of MZ-EIOM are presented. By optimizing the polarization of incident laser beam and stabilizing MZ-EOIM temperature, the static on/off ratio of 12600:1 is achieved. Also the dynamic on/off ratios versus the pulse repetition rate and the pulse duty cycle are measured and discussed. This high on/off ratio ns pulsed laser system has served as the excitation pulse source for a triggered single-photon source based on trapped single cesium atom, which reveals a representative anti-bunching.

  18. 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)

  19. 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

  20. 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...

  1. High-Aspect Ratio Bio-Metallic Nanocomposites for Cellular Interactions

    Science.gov (United States)

    Deodhar, Sneha; Huckaby, Justin; Delahoussaye, Miles; DeCoster, Mark A.

    2014-08-01

    We synthesized high aspect ratio composites with biological and metal components. Scanning electron microscopy (SEM) and Transmission Electron Microscopy (TEM) revealed linear morphology and smooth surface texture. SEM, TEM and light microscopy showed that composites have scalable dimensions from nano- to micro-, with diameters as low as 60 nm, lengths exceeding 150 pm, and average aspect ratio of 100. The structures are stable, remaining intact for over one year in dried form and in liquid, and did not aggregate, in contrast to metal nanoparticles such as iron and copper. Many metal nanoparticles are toxic to cells, limiting their use for biological applications. The bio-metallic composites characterized here showed lower toxicity compared to their precursor metal nanoparticles in brain tumor cell cultures. Due to these more biocompatible properties, we tested the ability of the composites to interact with cells. Zeta potential analysis indicated that composites carry a net negative charge (-24.3 ± 2.2 mV), while the starting metal nanoparticles measured (43.3 ± 2.4 mV). We labeled the composites with poly-l-lysine fluorescein isothiocyanate (PLL-FITC), which shifted the potential to 3.5 ± 2.9 mV. It was observed by fluorescence microscopy that composites smaller than cells were internalized by some cells and larger composites remained outside. Cells became fluorescent over time due to leakage of PLL-FITC from the composites which lost fluorescence over time. Higher biocompatibility, low aggregation, and ability to control size distribution of the linear composites may make them ideal vehicles to deliver drugs or other materials to cells, and may be used as a scaffolding material for cells.

  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. 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.

  9. 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

  10. 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.

  11. HIGH-GRADIENT, HIGH-TRANSFORMER-RATIO, DIELECTRIC WAKE FIELD ACCELERATOR

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2012-04-12

    The Phase I work reported here responds to DoE'ss stated need "...to develop improved accelerator designs that can provide very high gradient (>200 MV/m for electrons...) acceleration of intense bunches of particles." Omega-P's approach to this goal is through use of a ramped train of annular electron bunches to drive a coaxial dielectric wakefield accelerator (CDWA) structure. This approach is a direct extension of the CDWA concept from acceleration in wake fields caused by a single drive bunch, to the more efficient acceleration that we predict can be realized from a tailored (or ramped) train of several drive bunches. This is possible because of a much higher transformer ratio for the latter. The CDWA structure itself has a number of unique features, including: a high accelerating gradient G, potentially with G > 1 GeV/m; continuous energy coupling from drive to test bunches without transfer structures; inherent transverse focusing forces for particles in the accelerated bunch; highly stable motion of high charge annular drive bunches; acceptable alignment tolerances for a multi-section system. What is new in the present approach is that the coaxial dielectric structure is now to be energized by-not one-but by a short train of ramped annular-shaped drive bunches moving in the outer coaxial channel of the structure. We have shown that this allows acceleration of an electron bunch traveling along the axis in the inner channel with a markedly higher transformer ratio T than for a single drive bunch. As described in this report, the structure will be a GHz-scale prototype with cm-scale transverse dimensions that is expected to confirm principles that can be applied to the design of a future THz-scale high gradient (> 500 MV/m) accelerator with mm-scale transverse dimensions. We show here a new means to significantly increase the transformer ratio T of the device, and thereby to significantly improve its suitability as a flexible and effective component in

  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. Research and development on transonic compressor of high pressure ratio turbocharger for vehicle internal combustion engines

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The pressure ratio required for a turbocharger centrifugal compressor increases with internal combustion engine power density. High pressure ratio causes a transonic flow field at the impeller inducer. Transonic flow narrows the stable flow range and de-teriorates stage efficiency. In this work, an advanced high pressure ratio transonic compressor was designed. The experimental results show that the maximum pressure ratio of this turbocharger is about 4.2, the maximum efficiency is above 80% and the stable flow range at the designed rotating speed is up to 34%. A turbocharger with this transonic compressor has been applied to some vehicle research actually, and improved power density by 40%.

  14. 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

  15. 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.

  16. 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^...

  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. Dynamic contrast-enhanced magnetic resonance imaging parameters correlate with advanced revised-ISS and angiopoietin-1/angiopoietin-2 ratio in patients with multiple myeloma.

    Science.gov (United States)

    Terpos, Evangelos; Matsaridis, Dimitris; Koutoulidis, Vassilis; Zagouri, Flora; Christoulas, Dimitrios; Fontara, Sophia; Panourgias, Evangelia; Gavriatopoulou, Maria; Kastritis, Efstathios; Dimopoulos, Meletios A; Moulopoulos, Lia A

    2017-08-01

    The aim of the study was to assess the value of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in patients with newly diagnosed multiple myeloma (MM) who were treated with novel anti-myeloma agents. We studied 60 previously untreated MM patients at diagnosis, 14 with smoldering MM (SMM) and 5 with MGUS. All patients underwent MRI of the thoracolumbar spine and pelvis before the administration of any kind of therapy, and DCE-MRI was performed. The MRI perfusion parameters evaluated were wash-in (WIN), washout (WOUT), time-to-peak (TTPK), time-to-maximum slope (TMSP), and the WIN/TMSP ratio. The following serum levels of angiogenic cytokines were measured on the day of MRI: VEGF, angiogenin (Ang), angiopoietin-1 (Angp-1), and -2 (Angp-2). Symptomatic MM patients had increased WIN compared to SMM (p ISS. Patients with R-ISS-3 had lower TTPK median value (23 s, range 18-29 s) compared to patients with R-ISS-2 (48 s, range 27-68 s) and patients with R-ISS-1 MM (54 s, range 42-76 s; p ANOVA = 0.01). A subset of patients with low TTPK (lower quartile) had shorter time to progression compared to all other patients. These data suggest that certain DCE-MRI parameters correlate with R-ISS and adverse prognostic features of angiogenesis, such as the ratio of Angp-1/Angp-2.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  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-aspect-ratio photoresist processing for fabrication of high resolution and thick micro-windings

    Science.gov (United States)

    Anthony, Ricky; Laforge, Elias; Casey, Declan P.; Rohan, James F.; O'Mathuna, Cian

    2016-10-01

    DC winding losses remain a major roadblock in realizing high efficiency micro-magnetic components (inductors/transformers). This paper reports an optimized photoresist process using negative tone and acrylic based THB-151N (from JSR Micro), to achieve one of the highest aspect ratio (17:1) and resolution (~5 µm) resist patterns for fabrication of thick (~80 µm) micro-winding using UV lithography. The process was optimized to achieve photoresist widths from 5 µm to 20 µm with resist thickness of ~85 µm in a single spin step. Unlike SU-8, this resist can be readily removed and shows a near-vertical (~91°) electroplated Cu side-wall profile. Moreover, the high resolution compared to available resist processes enables a further reduction in the footprint area and can potentially increase the number of winding thereby increasing the inductance density for micro-magnetic components. Resistance measurements of electroplated copper winding of air-core micro-inductors within the standard 0402 size (0.45 mm2 footprint area) suggested a 42% decrease in resistance (273 mΩ-159 mΩ) with the increase in electroplated Cu thickness (from 50 µm to 80 µm). Reduction of the spacings (from 10 µm to 5 µm) enabled further miniaturisation of the device footprint area (from 0.60 mm2 to 0.45 mm2) without significant increase in resistance.

  7. Mechanical Properties of Recycled Aggregate Concrete at Low and High Water/Binder Ratios

    Directory of Open Access Journals (Sweden)

    Gai-Fei Peng

    2013-01-01

    Full Text Available This paper presents an experimental research on mechanical properties of recycled aggregate concrete (RAC at low and high water/binder (W/B ratios. Concrete at two W/B ratios (0.255 and 0.586 was broken into recycled concrete aggregates (RCA. A type of thermal treatment was employed to remove mortar attached to RCA. The RAC at a certain (low or high W/B ratio was prepared with RCA made from demolished concrete of the same W/B ratio. Tests were conducted on aggregate to measure water absorption and crushing values and on both RAC and natural aggregate concrete (NAC to measure compressive strength, tensile splitting strength, and fracture energy. The mechanical properties of RAC were lower than those of NAC at an identical mix proportion. Moreover, the heating process caused a decrease in compressive strength and fracture energy in the case of low W/B ratio but caused an increase in those properties in the case of high W/B ratio. The main type of flaw in RCA from concrete at a low W/B ratio should be microcracks in gravel, and the main type of flaw in RCA from concrete at a high W/B ratio should be attached mortar.

  8. 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.

  9. 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

  10. 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.

  11. 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...

  12. 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...

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Relationship Model Between Nightlight Data and Floor Area Ratio from High Resolution Images

    Science.gov (United States)

    Yan, M.; Xu, L.

    2017-09-01

    It is a hotpot that extraction the floor area ratio from high resolution remote sensing images. It is a development trend of using nightlight data to survey the urban social and economic information. This document aims to provide a conference relationship model for VIIRS/NPP nightlight data and floor Area Ratio from High Resolution ZY-3 Images. It shows that there is a lineal relationship between the shadow and the floor area ratio, and the R2 is 0.98. It shows that there is a quadratic polynomial relationship between the floor area ratio and the nightlight, and the R2 is 0.611. We can get a conclusion that, VIIRS/NPP nightlights data may show the floor area ratio in an extent at level of administrative street.

  3. 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...

  4. Flow visualization study in high aspect ratio cooling channels for rocket engines

    Science.gov (United States)

    Meyer, Michael L.; Giuliani, James E.

    1993-11-01

    The structural integrity of high pressure liquid propellant rocket engine thrust chambers is typically maintained through regenerative cooling. The coolant flows through passages formed either by constructing the chamber liner from tubes or by milling channels in a solid liner. Recently, Carlile and Quentmeyer showed life extending advantages (by lowering hot gas wall temperatures) of milling channels with larger height to width aspect ratios (AR is greater than 4) than the traditional, approximately square cross section, passages. Further, the total coolant pressure drop in the thrust chamber could also be reduced, resulting in lower turbomachinery power requirements. High aspect ratio cooling channels could offer many benefits to designers developing new high performance engines, such as the European Vulcain engine (which uses an aspect ratio up to 9). With platelet manufacturing technology, channel aspect ratios up to 15 could be formed offering potentially greater benefits. Some issues still exist with the high aspect ratio coolant channels. In a coolant passage of circular or square cross section, strong secondary vortices develop as the fluid passes through the curved throat region. These vortices mix the fluid and bring lower temperature coolant to the hot wall. Typically, the circulation enhances the heat transfer at the hot gas wall by about 40 percent over a straight channel. The effect that increasing channel aspect ratio has on the curvature heat transfer enhancement has not been sufficiently studied. If the increase in aspect ratio degrades the secondary flow, the fluid mixing will be reduced. Analysis has shown that reduced coolant mixing will result in significantly higher wall temperatures, due to thermal stratification in the coolant, thus decreasing the benefits of the high aspect ratio geometry. A better understanding of the fundamental flow phenomena in high aspect ratio channels with curvature is needed to fully evaluate the benefits of this

  5. Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin: the effect of local biogenic emissions

    Science.gov (United States)

    Seco, R.; Peñuelas, J.; Filella, I.; Llusià, J.; Molowny-Horas, R.; Schallhart, S.; Metzger, A.; Müller, M.; Hansel, A.

    2011-12-01

    Atmospheric volatile organic compounds (VOCs) are involved in ozone and aerosol generation, thus having implications for air quality and climate. VOCs and their emissions by vegetation also have important ecological roles as they can protect plants from stresses and act as communication cues between plants and between plants and animals. In spite of these key environmental and biological roles, the reports on seasonal and daily VOC mixing ratios in the literature for Mediterranean natural environments are scarce. We conducted seasonal (winter and summer) measurements of VOC mixing ratios in an elevated (720 m a.s.l.) holm oak Mediterranean forest site near the metropolitan area of Barcelona (NE Iberian Peninsula). Methanol was the most abundant compound among all the VOCs measured in both seasons. While aromatic VOCs showed almost no seasonal variability, short-chain oxygenated VOCs presented higher mixing ratios in summer, presumably due to greater emission by vegetation and increased photochemistry, both enhanced by the high temperatures and solar radiation in summer. Isoprenoid VOCs showed the biggest seasonal change in mixing ratios: they increased by one order of magnitude in summer, as a result of the vegetation's greater physiological activity and emission rates. The maximum diurnal concentrations of ozone increased in summer too, most likely due to more intense photochemical activity and the higher levels of VOCs in the air. The daily variation of VOC mixing ratios was mainly governed by the wind regime of the mountain, as the majority of the VOC species analyzed followed a very similar diel cycle. Mountain and sea breezes that develop after sunrise advect polluted air masses to the mountain. These polluted air masses had previously passed over the urban and industrial areas surrounding the Barcelona metropolitan area, where they were enriched in NOx and in VOCs of biotic and abiotic origin. Moreover, these polluted air masses receive additional biogenic

  6. Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin: the effect of local biogenic emissions

    Directory of Open Access Journals (Sweden)

    R. Seco

    2011-12-01

    Full Text Available Atmospheric volatile organic compounds (VOCs are involved in ozone and aerosol generation, thus having implications for air quality and climate. VOCs and their emissions by vegetation also have important ecological roles as they can protect plants from stresses and act as communication cues between plants and between plants and animals. In spite of these key environmental and biological roles, the reports on seasonal and daily VOC mixing ratios in the literature for Mediterranean natural environments are scarce.

    We conducted seasonal (winter and summer measurements of VOC mixing ratios in an elevated (720 m a.s.l. holm oak Mediterranean forest site near the metropolitan area of Barcelona (NE Iberian Peninsula. Methanol was the most abundant compound among all the VOCs measured in both seasons. While aromatic VOCs showed almost no seasonal variability, short-chain oxygenated VOCs presented higher mixing ratios in summer, presumably due to greater emission by vegetation and increased photochemistry, both enhanced by the high temperatures and solar radiation in summer. Isoprenoid VOCs showed the biggest seasonal change in mixing ratios: they increased by one order of magnitude in summer, as a result of the vegetation's greater physiological activity and emission rates. The maximum diurnal concentrations of ozone increased in summer too, most likely due to more intense photochemical activity and the higher levels of VOCs in the air.

    The daily variation of VOC mixing ratios was mainly governed by the wind regime of the mountain, as the majority of the VOC species analyzed followed a very similar diel cycle. Mountain and sea breezes that develop after sunrise advect polluted air masses to the mountain. These polluted air masses had previously passed over the urban and industrial areas surrounding the Barcelona metropolitan area, where they were enriched in NOx and in VOCs of biotic and abiotic origin. Moreover, these

  7. High-speed microprobe for roughness measurements in high-aspect-ratio microstructures

    Science.gov (United States)

    Doering, Lutz; Brand, Uwe; Bütefisch, Sebastian; Ahbe, Thomas; Weimann, Thomas; Peiner, Erwin; Frank, Thomas

    2017-03-01

    Cantilever-type silicon microprobes with an integrated tip and a piezoresistive signal read out have successfully proven to bridge the gap between scanning force microscopy and stylus profilometry. Roughness measurements in high-aspect-ratio microstructures (HARMS) with depths down to 5 mm and widths down to 50 µm have been demonstrated. To improve the scanning speed up to 15 mm s‑1, the wear of the tip has to be reduced. The atomic layer deposition (ALD) technique with alumina (Al2O3) has been tested for this purpose. Repeated wear measurements with coated and uncoated microprobe cantilevers have been carried out on a roughness standard at a speed of 15 mm s‑1. The tip shape and the wear have been measured using a new probing tip reference standard containing rectangular silicon grooves with widths from 0.3 µm to 3 µm. The penetration depth of the microprobe allows one to measure the wear of the tip as well as the tip width and the opening angle of the tip. The roughness parameters obtained on the roughness standard during wear experiments agree well with the reference values measured with a calibrated stylus instrument, nevertheless a small amount of wear still is observable. Further research is necessary in order to obtain wear resistant microprobe tips for non-destructive inspection of microstructures in industry and microform measurements, for example in injection nozzles.

  8. 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.

  9. Microstructure and Property of High Carbonic-Chromium Cast Steel with Different Hot Deformation Ratio

    Institute of Scientific and Technical Information of China (English)

    XU Tao; WANG Jiu-liang; ZHANG Run-jun; CHAO Guo-hua; LIU Jian-hua

    2004-01-01

    The microstructure and properties of high carbonic-chromium cast steel subjected to different hot deformation ratios were studied. The experimental results show that the microstructure and properties of high carbonic-chromium cast steel are obviously improved after hot deformation, and the best mechanical properties of the cast steel can be obtained under hot deformation ratio of 40 %-50 %, which leads to the morphology change of eutectic carbide and the precipitation of granular carbides.

  10. Ultra-high aspect ratio replaceable AFM tips using deformation-suppressed focused ion beam milling

    DEFF Research Database (Denmark)

    Savenko, Alexey; Yildiz, Izzet; Petersen, Dirch Hjorth;

    2013-01-01

    Fabrication of ultra-high aspect ratio exchangeable and customizable tips for atomic force microscopy (AFM) using lateral focused ion beam (FIB) milling is presented. While on-axis FIB milling does allow high aspect ratio (HAR) AFM tips to be defined, lateral milling gives far better flexibility...... FIB milling strategies for obtaining sharper tips are discussed. Finally, assembly of the HAR tips on a custom-designed probe as well as the first AFM scanning is shown....

  11. 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.

  12. Investigation of High Molar Ratio Potassium Solution Used in Zinc-Rich Coatings

    Institute of Scientific and Technical Information of China (English)

    LI Sheng; WU Hang; YAN Rui

    2004-01-01

    High molar ratio potassium silicate solution used in zinc-rich water-base coatings was prepared by adding the nanosize SiO2 to the low molar ratio potassium silicate solution, and its microstructure was investigated by SEM and IR.Furthermore, the zinc-rich coatings was prepared by adding the zinc powders to this type of solution, and the properties of the coatings were evaluated. The test results show that the high molar ratio potassium silicate solution is the bonder of zinc-rich inorganic coatings with excellent property.

  13. 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.

  14. 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...

  15. 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.

  16. 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.

  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. Synthesis of high aspect ratio ZnO nanowires with an inexpensive handcrafted electrochemical setup

    Science.gov (United States)

    Taheri, Ali; Saramad, Shahyar; Setayeshi, Saeed

    2016-12-01

    In this work, high aspect ratio zinc oxide nanowires are synthesized using templated one-step electrodeposition technique. Electrodeposition of the nanowires is done using a handcrafted electronic system. Nuclear track-etched polycarbonate membrane is used as a template to form the high aspect ratio nanowires. The result of X-ray diffraction and scanning electron microscopy shows that nanowires with a good crystallinity and an aspect ratio of more than 30 can be achieved in a suitable condition. The height of electrodeposited nanowires reaches to about 11 μm. Based on the obtained results, high aspect ratio ZnO nanowires can be formed using inexpensive electrodeposition setup with an acceptable quality.

  19. 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.

  20. 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.

  1. Simultaneous generation of ions and high-order harmonics from thin conjugated polymer foil irradiated with ultrahigh contrast laser

    Energy Technology Data Exchange (ETDEWEB)

    Choi, I. W.; Kim, I J.; Pae, K. H.; Nam, K. H.; Lee, C.-L.; Yun, H.; Kim, H. T.; Lee, S. K.; Yu, T. J.; Sung, J. H.; Lee, J. [Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Pirozhkov, A. S.; Ogura, K.; Orimo, S.; Daido, H. [Quantum Beam Science Directorate, Japan Atomic Energy Agency, Kizugawa, Kyoto 619-0215 (Japan)

    2011-10-31

    We report the manufacturing of an (ultra-)thin foil target made of conjugated polymer, poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT), and the simultaneous observation of laser-accelerated ions and second harmonic radiation, when irradiated with ultrahigh-contrast laser pulse at a maximum intensity of 4 x 10{sup 19 }W/cm{sup 2}. Maximum proton energy of 8 MeV is achieved along the target normal direction. Strong second harmonic with over 6% energy ratio compared to fundamental is emitted along the specular direction. Two-dimensional particle-in-cell simulations confirm the simultaneous generation of protons and high-order harmonics, which demonstrates the feasibility of applications requiring particle and radiation sources at once, effectively using the same laser and target.

  2. Orbital Differential Imaging: A New High-Contrast Post-Processing Technique For Direct Imaging of Exoplanets

    CERN Document Server

    Males, Jared R; Bendek, Eduardo

    2015-01-01

    Current post-processing techniques in high contrast imaging depend on some source of diversity between the exoplanet signal and the residual star light at that location. The two main techniques are angular differential imaging (ADI), which makes use of parallactic sky rotation to separate planet from star light, and spectral differential imaging (SDI), which makes use of differences in the spectrum of planet and star light and the wavelength dependence of the point spread function (PSF). Here we introduce our technique for exploiting another source of diversity: orbital motion. Given repeated observations of an exoplanetary system with sufficiently short orbital periods, the motion of the planets allows us to discriminate them from the PSF. In addition to using powerful PSF subtraction algorithms, such an observing strategy enables temporal filtering. Once an orbit is determined, the planet can be ``de-orbited'' to further increase the signal-to-noise ratio. We call this collection of techniques Orbital Diffe...

  3. 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.

  4. 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.

  5. 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...

  6. Fabrication of high aspect ratio nanocell lattices by ion beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Osamu [School of Environmental Science and Technology, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan); Nitta, Noriko, E-mail: nitta.noriko@kochi-tech.ac.jp [School of Environmental Science and Technology, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan); Center for Nanotechnology, Research Institute, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan); Taniwaki, Masafumi [School of Environmental Science and Technology, Kochi University of Technology, Tosayamada, Kami, Kochi 782-8502 (Japan)

    2016-11-01

    Highlights: • Nanocell lattice with a high aspect ratio on InSb semiconductor surface was fabricated by ion beam irradiation. • The fabrication technique consisting of top-down and bottom-up processes was performed in FIB. • High aspect ratio of 2 was achieved in nanocell lattice with a 100 nm interval. • The intermediate-flux irradiation is favorable for fabrication of nanocell with a high aspect ratio. - Abstract: A high aspect ratio nanocell lattice was fabricated on the InSb semiconductor surface using the migration of point defects induced by ion beam irradiation. The fabrication technique consisting of the top-down (formation of voids and holes) and bottom-up (growth of voids and holes into nanocells) processes was performed using a focused ion beam (FIB) system. A cell aspect ratio of 2 (cell height/cell diameter) was achieved for the nanocell lattice with a 100 nm dot interval The intermediate-flux ion irradiation during the bottom-up process was found to be optimal for the fabrication of a high aspect ratio nanocell.

  7. 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...

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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

  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 Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak.

    Science.gov (United States)

    Thome, K E; Bongard, M W; Barr, J L; Bodner, G M; Burke, M G; Fonck, R J; Kriete, D M; Perry, J M; Schlossberg, D J

    2016-04-29

    Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

  15. 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

  16. Alcohol intake and triglycerides/high-density lipoprotein cholesterol ratio in men with hypertension.

    Science.gov (United States)

    Wakabayashi, Ichiro

    2013-07-01

    The triglycerides/high-density lipoprotein cholesterol (TG/HDL-C) ratio has been proposed to be a good predictor of cardiovascular disease. The relationship between alcohol consumption and TG/HDL-C ratio in patients with hypertension is unknown. Subjects were normotensive and hypertensive men aged 35-60 years who were divided by daily ethanol intake into non-, light (<22g/day), heavy (≥22 but <44g/day), and very heavy (≥44g/day) drinkers. The TG/HDL-C ratio was significantly higher in the hypertensive group than in the normotensive group. Both in the normotensive and hypertensive groups, TG/HDL-C ratio was significantly lower in light, heavy, and very heavy drinkers than in nondrinkers and was lowest in light drinkers. In the hypertensive group, odds ratios (ORs) for high TG/HDL-C ratio (≥3.75) in light, heavy, and very heavy drinkers vs. nondrinkers were significantly lower (P < 0.01) than a reference level of 1.00 (light drinkers: OR = 0.49, 95% confidence interval (CI) = 0.40-0.59; heavy drinkers: OR = 0.59, 95% CI = 0.52-0.67; very heavy drinkers: OR = 0.70, 95% CI = 0.61-0.80) and were significantly lower than the corresponding ORs in the normotensive group. The ORs for hypertension in subjects with vs. subjects without high TG/HDL-C ratio were significantly higher than the reference level in all the alcohol groups and were significantly lower in light, heavy, and very heavy drinkers than in nondrinkers. The results suggest that there is an inverted J-shaped relationship between alcohol and TG/HDL-C ratio in individuals with hypertension and that alcohol weakens the positive association between TG/HDL-C ratio and hypertension.

  17. A continuous flow isotope ratio mass spectrometry method for high precision determination of dissolved gas ratios and isotopic composition

    DEFF Research Database (Denmark)

    Charoenpong, C. N.; Bristow, L. A.; Altabet, M. A.

    2014-01-01

    Dissolved gas ratios and isotopic compositions provide essential information about the biological and physical mechanisms influencing N-2, O-2, and Ar in aquatic systems. Current methods available are either limited by overall cost, labor-intensive sample collection and analysis, or insufficient ...

  18. The effect of tip speed ratio on a vertical axis wind turbine at high Reynolds numbers

    Science.gov (United States)

    Parker, Colin M.; Leftwich, Megan C.

    2016-05-01

    This work visualizes the flow surrounding a scaled model vertical axis wind turbine at realistic operating conditions. The model closely matches geometric and dynamic properties—tip speed ratio and Reynolds number—of a full-size turbine. The flow is visualized using particle imaging velocimetry (PIV) in the midplane upstream, around, and after (up to 4 turbine diameters downstream) the turbine, as well as a vertical plane behind the turbine. Time-averaged results show an asymmetric wake behind the turbine, regardless of tip speed ratio, with a larger velocity deficit for a higher tip speed ratio. For the higher tip speed ratio, an area of averaged flow reversal is present with a maximum reverse flow of -0.04U_∞. Phase-averaged vorticity fields—achieved by syncing the PIV system with the rotation of the turbine—show distinct structures form from each turbine blade. There were distinct differences in results by tip speed ratios of 0.9, 1.3, and 2.2 of when in the cycle structures are shed into the wake—switching from two pairs to a single pair of vortices being shed—and how they convect into the wake—the middle tip speed ratio vortices convect downstream inside the wake, while the high tip speed ratio pair is shed into the shear layer of the wake. Finally, results show that the wake structure is much more sensitive to changes in tip speed ratio than to changes in Reynolds number.

  19. Behavior of High Water-cement Ratio Concrete under Biaxial Compression after Freeze-thaw Cycles

    Institute of Scientific and Technical Information of China (English)

    SHANG Huaishuai; SONG Yupu; OU Jinping

    2008-01-01

    The high water-cement ratio concrete specimens under biaxial compression that completed in a triaxial testing machine were experimentally studied.Strength and deformations of plain concrete specimens after 0,25,50 cycles of freeze-thaw.Influences of freeze-thaw cycles and stress ratio on the peak stress and deformation of this point were analyzed aecording to the experimental results.Based on the test data,the failure criterion expressed in terms of principal stress after difierent cycles of freeze-thaw,and the failure criterion with consideration of the influence of freeze-thaw cycle and sffess ratio were proposed respectively.

  20. Wafer-scale fabrication of high-aspect ratio nanochannels based on edge-lithography technique.

    Science.gov (United States)

    Xie, Quan; Zhou, Qing; Xie, Fei; Sang, Jianming; Wang, Wei; Zhang, Haixia Alice; Wu, Wengang; Li, Zhihong

    2012-03-01

    This paper introduced a wafer-scale fabrication approach for the preparation of nanochannels with high-aspect ratio (the ratio of the channel depth to its width). Edge lithography was used to pattern nanogaps in an aluminum film, which was functioned as deep reactive ion etching mask thereafter to form the nanochannel. Nanochannels with aspect ratio up to 172 and width down to 44 nm were successfully fabricated on a 4-inch Si wafer with width nonuniformity less than 13.6%. A microfluidic chip integrated with nanometer-sized filters was successfully fabricated by utilizing the present method for geometric-controllable nanoparticle packing.

  1. 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...

  2. 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.

  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. Measurement of the Ratio of High Energy Neutron in the Pulse Nuclear Reactor

    Institute of Scientific and Technical Information of China (English)

    MAO; Guo-shu; DING; You-qian; YANG; Lei; MA; Peng; YU; Zhen-hua

    2012-01-01

    <正>In the production of radioisotopes and neutron activation analysis, the fast neutron densities are very important to estimate the yields of the radioisotopes. In order to determine the fast neutron flux ratio, different foils are used to measure the thermal neutron flux and the fast neutron flux. In this paper 238U was used as only a monitor to measure the ratio of high energy neutron (>6 MeV). By measuring the

  5. Performance of AC/graphite capacitors at high weight ratios of AC/graphite

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan); Yoshio, Masaki [Advanced Research Center, Department of Applied Chemistry, Saga University, 1341 Yoga-machi, Saga 840-0047 (Japan)

    2008-03-01

    The effect of negative to positive electrode materials' weight ratio on the electrochemical performance of both activated carbon (AC)/AC and AC/graphite capacitors has been investigated, especially in the terms of capacity and cycle-ability. The limited capacity charge mode has been proposed to improve the cycle performance of AC/graphite capacitors at high weight ratios of AC/graphite. (author)

  6. Physical Delivery of Macromolecules using High-Aspect Ratio Nanostructured Materials.

    Science.gov (United States)

    Lee, Kunwoo; Lingampalli, Nithya; Pisano, Albert P; Murthy, Niren; So, Hongyun

    2015-10-28

    There is great need for the development of an efficient delivery method of macromolecules, including nucleic acids, proteins, and peptides, to cell cytoplasm without eliciting toxicity or changing cell behavior. High-aspect ratio nanomaterials have addressed many challenges present in conventional methods, such as cell membrane passage and endosomal degradation, and have shown the feasibility of efficient high-throughput macromolecule delivery with minimal perturbation of cells. This review describes the recent advances of in vitro and in vivo physical macromolecule delivery with high-aspect ratio nanostructured materials and summarizes the synthesis methods, material properties, relevant applications, and various potential directions.

  7. Modeling and characterization of dielectrophoretically structured piezoelectric composites using piezoceramic particle inclusions with high aspect ratios

    NARCIS (Netherlands)

    Ende, D.A. van den; Maier, R.A.; Neer, P.L.M.J. van; Zwaag, S. van der; Randall, C.A.; Groen, W.A.

    2013-01-01

    In this work, the piezoelectric properties at high electric fields of dielectrophoretically aligned PZT - polymer composites containing high aspect ratio particles (such as short fibers) are presented. Polarization and strain as a function of electric field are evaluated. The properties of the compo

  8. A Four-Phase High Voltage Conversion Ratio Bidirectional DC-DC Converter for Battery Applications

    Directory of Open Access Journals (Sweden)

    Li-Kun Xue

    2015-06-01

    Full Text Available This study presents a four-phase interleaved high voltage conversion ratio bidirectional DC-DC converter circuit based on coupled inductors and switched capacitors, which can eliminate the defects of conventional high voltage conversion ratio bidirectional DC-DC converters in terms of high-voltage/current stress, less efficiency and low-power limitation. Parallel channels are used to reduce current stress at the low-voltage side and series connected switched capacitors are used to enlarge voltage conversion ratio, reduce voltage stress and achieve auto current sharing. This paper proposes the operation principle, feature analysis and optimization design considerations. On this basis the objectives of high voltage conversion ratio, low voltage/current stress, high power density, high efficiency and high-power applications can be achieved. Some experimental results based on a 500 W prototype converter (24 V to 48 V at low-voltage side, 400 V at high-voltage side are given to verify the theoretical analysis and the effectiveness of the proposed converter.

  9. Raised mortality from lung cancer and high sex ratios of births associated with industrial pollution.

    Science.gov (United States)

    Lloyd, O L; Smith, G; Lloyd, M M; Holland, Y; Gailey, F

    1985-07-01

    Geographical and temporal associations were shown between high mortality from lung cancer and a high sex ratio of births both in the town of Bathgate (Scotland) and in the area of that town which was most exposed to polluted air from a local steel foundry. These findings constituted a replication of a similar association in an adjacent town.

  10. Growth of high aspect ratio ZnO nanorods by solution process: Effect of polyethyleneimine

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Han-Seok; Vaseem, Mohammad; Kim, Sang Gon; Im, Yeon-Ho [School of Semiconductor and Chemical Engineering, Dept. of BIN Fusion Technology, BK 21 Centre for Future Energy Materials and Devices, and Nanomaterials Processing Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Hahn, Yoon-Bong, E-mail: ybhahn@chonbuk.ac.kr [School of Semiconductor and Chemical Engineering, Dept. of BIN Fusion Technology, BK 21 Centre for Future Energy Materials and Devices, and Nanomaterials Processing Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2012-05-15

    High aspect ratio ZnO nanorods were grown vertically on ZnO seed layer deposited silicon, glass and polyimide substrates by a solution process at low-temperature using zinc nitrate hexahydrate and hexamethylenetetramine. We studied the effect of polyethlyeneimine (PEI) on the growth of ZnO nanorods. It was found that PEI has a prominent effect on controlling the aspect ratio of ZnO nanorods in solution. The morphological and photoluminescence properties of the ZnO nanorods were also examined with varying the growth temperature (60-90 Degree-Sign C). - Graphical abstract: With addition of polyehyleneimine (PEI) high aspect-ratio ZnO nanorods were grown. It is believed that during ZnO nanorods growth, protonized form of linear PEI molecules inhibits the lateral growth by being adsorbed on non-polar lateral planes. Thus the vertical growth is favored. Highlights: Black-Right-Pointing-Pointer A controlled growth of high aspect ratio ZnO nanorods on different substrates. Black-Right-Pointing-Pointer A prominent effect of polyethlyeneimine (PEI) on controlling the aspect ratio of ZnO nanorods in solution. Black-Right-Pointing-Pointer Precursor concentration and growth temperature effect for various aspect ratio ZnO nanorods.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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....

  1. 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.

  2. 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.

  3. Jet noise of high aspect-ratio rectangular nozzles with application to pneumatic high-lift devices

    Science.gov (United States)

    Munro, Scott Edward

    Circulation control wings are a type of pneumatic high-lift device that have been extensively researched as to their aerodynamic benefits. However, there has been little research into the possible airframe noise reduction benefits. The key element of noise is the jet noise associated with the jet sheet emitted from the blowing slot. This jet sheet is essentially a high aspect-ratio rectangular jet. This study directly compared far-field noise emissions from a state-of-the-art circulation control wing high lift configuration, and a conventional wing also configured for high lift. Results indicated that a circulation control wing had a significant acoustic advantage over a conventional wing for identical lift performance. A high aspect-ratio nozzle was fabricated to study the general characteristics of high aspect-ratio jets with aspect ratios from 100 to 3000. The results of this study provided the basic elements in understanding how to reduce the noise from a circulation control wing. High aspect-ratio nozzle results showed that the jet noise of this type of jet was proportional to the 8th power of the jet velocity. It was also found that the jet noise was proportional to the slot height to the 3/2 power and slot width to the 1/2 power. Fluid dynamic experiments were also performed on the high aspect-ratio nozzle. Single hot-wire experiments indicated that the jet exhaust from the high aspect-ratio nozzle was similar to a 2-d turbulent jet. Two-wire space-correlation experiments were performed to attempt to find a relationship between the slot height of the jet and the length-scale of the flow noise generating turbulence structure. The turbulent eddy convection velocity was also calculated, and was found to vary with the local centerline velocity, and also as a function of the frequency of the eddy.

  4. Centimeter-deep tissue fluorescence microscopic imaging with high signal-to-noise ratio and picomole sensitivity

    CERN Document Server

    Cheng, Bingbing; Wei, Ming-Yuan; Pei, Yanbo; DSouza, Francis; Nguyen, Kytai T; Hong, Yi; Tang, Liping; Yuan, Baohong

    2015-01-01

    Fluorescence microscopic imaging in centimeter-deep tissue has been highly sought-after for many years because much interesting in vivo micro-information, such as microcirculation, tumor angiogenesis, and metastasis, may deeply locate in tissue. In this study, for the first time this goal has been achieved in 3-centimeter deep tissue with high signal-to-noise ratio (SNR) and picomole sensitivity under radiation safety thresholds. These results are demonstrated not only in tissue-mimic phantoms but also in actual tissues, such as porcine muscle, ex vivo mouse liver, ex vivo spleen, and in vivo mouse tissue. These results are achieved based on three unique technologies: excellent near infrared ultrasound-switchable fluorescence (USF) contrast agents, a sensitive USF imaging system, and an effective correlation method. Multiplex USF fluorescence imaging is also achieved. It is useful to simultaneously image multiple targets and observe their interactions. This work opens the door for future studies of centimeter...

  5. Thermo-mechanical properties of high aspect ratio silica nanofiber filled epoxy composites

    Science.gov (United States)

    Ren, Liyun

    The optimization of thermo-mechanical properties of polymer composites at low filler loadings is of great interest in both engineering and scientific fields. There have been several studies on high aspect ratio fillers as novel reinforcement phase for polymeric materials. However, facile synthesis method of high aspect ratio nanofillers is limited. In this study, a scalable synthesis method of high aspect ratio silica nanofibers is going to be presented. I will also demonstrate that the inclusion of high aspect ratio silica nanofibers in epoxy results in a significant improvement of epoxy thermo-mechanical properties at low filler loadings. With silica nanofiber concentration of 2.8% by volume, the Young's modulus, ultimate tensile strength and fracture toughness of epoxy increased ~23, ~28 and ~50%, respectively, compared to unfilled epoxy. At silica nanofiber volume concentration of 8.77%, the thermal expansion coefficient decreased by ˜40% and the thermal conductivity was improved by ˜95% at room temperature. In the current study, the influence of nano-sized silica filler aspect ratio on mechanical and thermal behavior of epoxy nanocomposites were studied by comparing silica nanofibers to spherical silica nanoparticles (with aspect ratio of one) at various filler loadings. The significant reinforcement of composite stiffness is attributed to the variation of the local stress state in epoxy due to the high aspect ratio of the silica nanofiber and the introduction of a tremendous amount of interfacial area between the nanofillers and the epoxy matrix. The fracture mechanisms of silica nanofiber filled epoxy were also investigated. The existence of high aspect ratio silica nanofiber promotes fracture energy dissipation by crack deflection, crack pinning as well as debonding with fiber pull-out leading to enhanced fracture toughness. High aspect ratio fillers also provide significant reduction of photon scattering due to formation of a continuous fiber network

  6. A high voltage ratio and low ripple interleaved DC-DC converter for fuel cell applications.

    Science.gov (United States)

    Chang, Long-Yi; Chao, Kuei-Hsiang; Chang, Tsang-Chih

    2012-01-01

    This paper proposes a high voltage ratio and low ripple interleaved boost DC-DC converter, which can be used to reduce the output voltage ripple. This converter transfers the low DC voltage of fuel cell to high DC voltage in DC link. The structure of the converter is parallel with two voltage-doubler boost converters by interleaving their output voltages to reduce the voltage ripple ratio. Besides, it can lower the current stress for the switches and inductors in the system. First, the PSIM software was used to establish a proton exchange membrane fuel cell and a converter circuit model. The simulated and measured results of the fuel cell output characteristic curve are made to verify the correctness of the established simulation model. In addition, some experimental results are made to validate the effectiveness in improving output voltage ripple of the proposed high voltage ratio interleaved boost DC-DC converters.

  7. Development of high-aspect-ratio microchannel heat exchanger based on multi-tool milling process

    Institute of Scientific and Technical Information of China (English)

    潘敏强; 李金恒; 汤勇

    2008-01-01

    A high-aspect-ratio microchannel heat exchanger based on multi-tool milling process was developed. Several slotting cutters were stacked together for simultaneously machining several high-aspect-ratio microchannels with manifold structures. On the basis of multi-tool milling process, the structural design of the manifold side height, microchannel length, width, number, and interval were analyzed. The heat transfer performances of high-aspect-ratio microchannel heat exchangers with two different manifolds were investigated by experiments, and the influencing factors were analyzed. The results indicate that the magnitude of heat transfer area per unit volume dominates the heat transfer performances of plate-type micro heat exchanger, while the velocity distribution between microchannels has little effects on the heat transfer performances.

  8. Fabrication of high aspect ratio nanogrid transparent electrodes via capillary assembly of Ag nanoparticles

    Science.gov (United States)

    Kang, Juhoon; Park, Chang-Goo; Lee, Su-Han; Cho, Changsoon; Choi, Dae-Geun; Lee, Jung-Yong

    2016-05-01

    In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%.In this report, we describe the fabrication of periodic Ag nanogrid electrodes by capillary assembly of silver nanoparticles (AgNPs) along patterned nanogrid templates. By assembling the AgNPs into these high-aspect-ratio nanogrid patterns, we can obtain high-aspect-ratio nanogratings, which can overcome the inherent trade-off between the optical transmittance and the sheet resistance of transparent electrodes. The junction resistance between the AgNPs is effectively reduced by photochemical welding and post-annealing. The fabricated high-aspect-ratio nanogrid structure with a line width of 150 nm and a height of 450 nm has a sheet resistance of 15.2 Ω sq-1 and an optical transmittance of 85.4%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01896c

  9. Fabrication of High Aspect Ratio SU-8 Structures for Integrated Spectrometers

    DEFF Research Database (Denmark)

    Anhøj, Thomas Aarøe

    2007-01-01

    of photolithography. Successful fabrication of re ection gratings requires a high degree of precision in the photolithographic process. The fabrication process has thus been optimized by optimizing the photolithographic process for fabrication of high aspect ratio structures, i.e. structures with details...... that are small compared to the height of the structure. A decisive factor is the ability of the process to separate closely- spaced structures. The primary measure of quality is thus the aspect ratio of the narrowest trench which it is possible to resolve in the lithographic process. The optimization...

  10. 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+.

  11. 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.

  12. 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).

  13. 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.

  14. 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).

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  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

    orders of magnitude or higher, we can reproduce the patterns obtained in the GeoFlow II experiment, implying that non-linear effects shift the effective viscosity ratio. Hence, the GeoFlow II experiment gives the possibility to study flows under high viscosity contrasts and is a promising candidate as reference experiment. REFERENCES [1] B. Futterer, C. Egbers, N. Dahley, S. Koch, L. Jehring (2010). Acta Astronautica 66. [2] B. Futterer, N. Dahley, S. Koch, N. Scurtu, C. Egbers (2012). Acta Astronautica 71. [3] R. Hollerbach, R., (2000). International Journal for Numerical Methods in Fluids 32. [4] C. Huettig, K. Stemmer, (2008). PEPI.

  1. Optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits.

    Science.gov (United States)

    Ozkan, Fahri; Tuna, M Cihat; Baylar, Ahmet; Ozturk, Mualla

    2014-01-01

    Oxygen is an important component of water quality and its ability to sustain life. Water aeration is the process of introducing air into a body of water to increase its oxygen saturation. Water aeration can be accomplished in a variety of ways, for instance, closed-conduit aeration. High-speed flow in a closed conduit involves air-water mixture flow. The air flow results from the subatmospheric pressure downstream of the gate. The air entrained by the high-speed flow is supplied by the air vent. The air entrained into the flow in the form of a large number of bubbles accelerates oxygen transfer and hence also increases aeration efficiency. In the present work, the optimum air-demand ratio for maximum aeration efficiency in high-head gated circular conduits was studied experimentally. Results showed that aeration efficiency increased with the air-demand ratio to a certain point and then aeration efficiency did not change with a further increase of the air-demand ratio. Thus, there was an optimum value for the air-demand ratio, depending on the Froude number, which provides maximum aeration efficiency. Furthermore, a design formula for aeration efficiency was presented relating aeration efficiency to the air-demand ratio and Froude number.

  2. 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

  3. 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...

  4. 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.

  5. 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...

  6. Cylindrospermopsis raciborskii dominates under very low and high nitrogen-to-phosphorus ratios.

    Science.gov (United States)

    Chislock, Michael F; Sharp, Katherine L; Wilson, Alan E

    2014-02-01

    In freshwater ecosystems, a variety of factors mediate phytoplankton community structure, including herbivore community structure, light availability, temperature, mixing, and absolute and relative nutrient concentrations (total nitrogen (TN), total phosphorus (TP)). Ecological stoichiometry examines how the nutrient content of organisms and their environment may mediate population-, community-, and ecosystem-level processes. The manipulation of N:P ratios is a widely regarded tool for managing phytoplankton species composition given that nitrogen-fixing cyanobacteria should dominate algal communities under relatively low N:P (nitrogen. However, due to the physiological expense of nitrogen fixation, diazotrophs should be outcompeted by non-nitrogen fixing phytoplankton under higher N:P when other environmental factors are similar. We tested this hypothesis in a field experiment using 2500-L limnocorrals installed in a eutrophic lake (ambient N:P ∼40:1 (by atoms); TN ∼1360 μgL(-1); TP ∼75 μgL(-1)). At the start of the experiment, we randomly assigned limnocorrals among the ambient (40:1) and low (7:1) or high (122:1) N:P treatments (n = 4 replicates/treatment), which were established by adding P or N at the start of the experiment, respectively. The phytoplankton community in the enclosures at the start of the experiment was diverse (i.e., 18 phytoplankton genera) and dominated by chlorophytes (including Coelastrum and Scenedesmus (30% and 13% of total biomass, respectively)) and cyanobacteria (including Anabaena and Cylindrospermopsis (23% and 17% of total biomass, respectively)). In contrast to predictions based on ecological stoichiometry, the phytoplankton community in all N:P treatments increased in abundance and was almost entirely composed of the nitrogen-fixing cyanobacterium, Cylindrospermopsis raciborskii, by the conclusion of the study. Moreover, concentrations of the cyanobacterial neurotoxin, saxitoxin, were enhanced under the two highest N

  7. 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.

  8. 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.

  9. 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

  10. Cryogenic Etching of High Aspect Ratio 400 nm Pitch Silicon Gratings.

    Science.gov (United States)

    Miao, Houxun; Chen, Lei; Mirzaeimoghri, Mona; Kasica, Richard; Wen, Han

    2016-10-01

    The cryogenic process and Bosch process are two widely used processes for reactive ion etching of high aspect ratio silicon structures. This paper focuses on the cryogenic deep etching of 400 nm pitch silicon gratings with various etching mask materials including polymer, Cr, SiO2 and Cr-on-polymer. The undercut is found to be the key factor limiting the achievable aspect ratio for the direct hard masks of Cr and SiO2, while the etch selectivity responds to the limitation of the polymer mask. The Cr-on-polymer mask provides the same high selectivity as Cr and reduces the excessive undercut introduced by direct hard masks. By optimizing the etching parameters, we etched a 400 nm pitch grating to ≈ 10.6 μm depth, corresponding to an aspect ratio of ≈ 53.

  11. Nano-scaled graphene platelets with a high length-to-width aspect ratio

    Science.gov (United States)

    Zhamu, Aruna; Guo, Jiusheng; Jang, Bor Z.

    2010-09-07

    This invention provides a nano-scaled graphene platelet (NGP) having a thickness no greater than 100 nm and a length-to-width ratio no less than 3 (preferably greater than 10). The NGP with a high length-to-width ratio can be prepared by using a method comprising (a) intercalating a carbon fiber or graphite fiber with an intercalate to form an intercalated fiber; (b) exfoliating the intercalated fiber to obtain an exfoliated fiber comprising graphene sheets or flakes; and (c) separating the graphene sheets or flakes to obtain nano-scaled graphene platelets. The invention also provides a nanocomposite material comprising an NGP with a high length-to-width ratio. Such a nanocomposite can become electrically conductive with a small weight fraction of NGPs. Conductive composites are particularly useful for shielding of sensitive electronic equipment against electromagnetic interference (EMI) or radio frequency interference (RFI), and for electrostatic charge dissipation.

  12. 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.

  13. 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

  14. Fast ion energy flux enhancement from ultra thin foils irradiated by intense and high contrast short laser pulses

    NARCIS (Netherlands)

    Andreev, A.; Levy, A.; Ceccotti, T.; Thaury, C.; Platonov, K.; Loch, R.A.; Martin, Ph.

    2008-01-01

    Recent significant improvements of the contrast ratio of chirped pulse amplified pulses allows us to extend the applicability domain of laser accelerated protons to very thin targets. In this framework, we propose an analytical model particularly suitable to reproducing ion laser acceleration

  15. Early high ratio platelet transfusion in trauma resuscitation and its outcomes

    Science.gov (United States)

    Peralta, Ruben; Vijay, Adarsh; El-Menyar, Ayman; Consunji, Rafael; Afifi, Ibrahim; Mahmood, Ismail; Asim, Mohammed; Latifi, Rifat; Al-Thani, Hassan

    2016-01-01

    Introduction: The optimal ratio of platelets (PLTs) to packed red blood cell (PRBC) in trauma patients requiring massive transfusion protocol (MTP) is still controversial. This report aims to describe the effect of attaining a high PLT:PRBC ratio (≥1:1.5) within 4 h postinjury on the outcomes of trauma patients receiving MTP. Methods: Over a 24-month period, records of all adult patients with traumatic injury who received MTP were retrospectively reviewed. Data were analyzed with respect to PLT:PRBC ratio ([high-MTP ≥1:1.5] [HMTP] vs. [low-MTP 4 and 24 h). Baseline demographic, clinical characteristics, complications, and outcomes were compared according to HMTP and LMTP. Results: Of the total 3244 trauma patients, PLT:PRBC ratio was attainable in 58 (1.2%) patients who fulfilled the inclusion criteria. The mean age was 32.3 ± 10.7 years; the majority were males (89.6%) with high mean Injury Severity Score (ISS): 31.9 ± 11.5 and Revise Trauma Score (RTS): 5.1 ± 2.2. There was no significant association between age, gender, type of injury, presenting hemoglobin, International Normalized Ratio, ISS, and RTS. The rate of ventilator–associated pneumonia (38.9% vs. 10.8%; P = 0.02) and wound infection (50% vs. 10.8%; P = 0.002) were significantly higher in the HMTP group. However, HMTP was associated with lower rate of multiple organ failure (MOF) (42.1% vs. 87.2%, P = 0.001) and mortality (36.8% vs. 84.6%, P = 0.001) within the first 30 days postinjury. Conclusions: Our study revealed that early attainment of high PLT/PRBC ratio within 4 h postinjury is significantly associated with lower MOF and mortality in trauma patients. PMID:28149824

  16. Different methods to alter surface morphology of high aspect ratio structures

    Energy Technology Data Exchange (ETDEWEB)

    Leber, M., E-mail: moritz.leber@utah.edu [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT (United States); Shandhi, M.M.H. [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT (United States); Hogan, A. [Blackrock Microsystems, Salt Lake City, UT (United States); Solzbacher, F. [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT (United States); Bhandari, R.; Negi, S. [Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT (United States); Blackrock Microsystems, Salt Lake City, UT (United States)

    2016-03-01

    Graphical abstract: Surface engineering of high aspect ratio silicon structures. - Highlights: • Multiple roughening techniques for high aspect ratio devices were investigated. • Modification of surface morphology of high aspect ratio silicon devices (1:15). • Decrease of 76% in impedance proves significant increase in surface area. - Abstract: In various applications such as neural prostheses or solar cells, there is a need to alter the surface morphology of high aspect ratio structures so that the real surface area is greater than geometrical area. The change in surface morphology enhances the devices functionality. One of the applications of altering the surface morphology is of neural implants such as the Utah electrode array (UEA) that communicate with single neurons by charge injection induced stimulation or by recording electrical neural signals. For high selectivity between single cells of the nervous system, the electrode surface area is required to be as small as possible, while the impedance is required to be as low as possible for good signal to noise ratios (SNR) during neural recording. For stimulation, high charge injection and charge transfer capacities of the electrodes are required, which increase with the electrode surface. Traditionally, researchers have worked with either increasing the roughness of the existing metallization (platinum grey, black) or other materials such as Iridium Oxide and PEDOT. All of these previously investigated methods lead to more complicated metal deposition processes that are difficult to control and often have a critical impact on the mechanical properties of the metal films. Therefore, a modification of the surface underneath the electrode's coating will increase its surface area while maintaining the standard and well controlled metal deposition process. In this work, the surfaces of the silicon micro-needles were engineered by creating a defined microstructure on the electrodes surface using several

  17. Film Cooling from Two Staggered Rows of Compound Angle Holes at High Blowing Ratios

    Directory of Open Access Journals (Sweden)

    Phillip M. Ligrani

    1996-01-01

    Full Text Available Experimental results are presented which describe the development and structure of flow downstream of two staggered rows of film-cooling holes with compound angle orientations at high blowing ratios. These film cooling configurations are important because they are frequently employed on the first stage of rotating blades of operating gas turbine engines. With this configuration, holes are spaced 3d apart in the spanwise direction, with inclination angles of 24 degrees, and angles of orientation of 50.5 degrees. Blowing ratios range from 0.5 to 4.0 and the ratio of injectant to freestream density is near 1.0. Results show that spanwise averaged adiabatic effectiveness, spanwise-averaged iso-energetic Stanton number ratios, surveys of streamwise mean velocity, and surveys of injectant distributions change by important amounts as the blowing ratio increases. This is due to injectant lift-off from the test surface just downstream of the holes which becomes more pronounced as blowing ratio increases.

  18. Highly Manufacturable Deep (Sub-Millimeter) Etching Enabled High Aspect Ratio Complex Geometry Lego-Like Silicon Electronics

    KAUST Repository

    Ghoneim, Mohamed T.

    2017-02-01

    A highly manufacturable deep reactive ion etching based process involving a hybrid soft/hard mask process technology shows high aspect ratio complex geometry Lego-like silicon electronics formation enabling free-form (physically flexible, stretchable, and reconfigurable) electronic systems.

  19. 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,...

  20. Laser thermal annealing of Ge, optimized for highly activated dopants and diode ION/IOFF ratios

    DEFF Research Database (Denmark)

    Shayesteh, M.; O'Connell, D.; Gity, F.;

    2014-01-01

    The authors compared the influence of laser thermal annealing (LTA) and rapid thermal annealing (RTA) on dopant activation and electrical performance of phosphorus and arsenic doped n+/p junction. High carrier concentration above 1020 cm-3 as well as an ION/IOFF ratio of approximately 105 and ide...

  1. Improving surface acousto-optical interaction by high aspect ratio electrodes

    DEFF Research Database (Denmark)

    Dühring, Maria Bayard; Laude, Vincent; Khelif, Abdelkrim

    2009-01-01

    The acousto-optical interaction of an optical wave confined inside a waveguide and a surface acoustic wave launched by an interdigital transducer (IDT) at the surface of a piezoelectric material is considered. The IDT with high aspect ratio electrodes supports several acoustic modes that are stro...

  2. Dense high-aspect ratio 3D carbon pillars on interdigitated microelectrode arrays

    DEFF Research Database (Denmark)

    Amato, Letizia; Heiskanen, Arto; Hansen, Rasmus

    2015-01-01

    In this work we present high-aspect ratio carbon pillars (1.4 μm in diameter and ∼11 μm in height) on top of interdigitated electrode arrays to be used for electrochemical applications. For this purpose, different types of 2D and 3D pyrolysed carbon structures were fabricated and characterised...

  3. 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.

  4. 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. ...

  5. 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.

  6. 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.

  7. 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...

  8. 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.

  9. High Yield Synthesis of Aspect Ratio Controlled Graphenic Materials from Anthracite Coal in Supercritical Fluids.

    Science.gov (United States)

    Sasikala, Suchithra Padmajan; Henry, Lucile; Yesilbag Tonga, Gulen; Huang, Kai; Das, Riddha; Giroire, Baptiste; Marre, Samuel; Rotello, Vincent M; Penicaud, Alain; Poulin, Philippe; Aymonier, Cyril

    2016-05-24

    This paper rationalizes the green and scalable synthesis of graphenic materials of different aspect ratios using anthracite coal as a single source material under different supercritical environments. Single layer, monodisperse graphene oxide quantum dots (GQDs) are obtained at high yield (55 wt %) from anthracite coal in supercritical water. The obtained GQDs are ∼3 nm in lateral size and display a high fluorescence quantum yield of 28%. They show high cell viability and are readily used for imaging cancer cells. In an analogous experiment, high aspect ratio graphenic materials with ribbon-like morphology (GRs) are synthesized from the same source material in supercritical ethanol at a yield of 6.4 wt %. A thin film of GRs with 68% transparency shows a surface resistance of 9.3 kΩ/sq. This is apparently the demonstration of anthracite coal as a source for electrically conductive graphenic materials.

  10. Short term reproducibility of a high contrast 3-D isotropic optic nerve imaging sequence in healthy controls

    Science.gov (United States)

    Harrigan, Robert L.; Smith, Alex K.; Mawn, Louise A.; Smith, Seth A.; Landman, Bennett A.

    2016-03-01

    The optic nerve (ON) plays a crucial role in human vision transporting all visual information from the retina to the brain for higher order processing. There are many diseases that affect the ON structure such as optic neuritis, anterior ischemic optic neuropathy and multiple sclerosis. Because the ON is the sole pathway for visual information from the retina to areas of higher level processing, measures of ON damage have been shown to correlate well with visual deficits. Increased intracranial pressure has been shown to correlate with the size of the cerebrospinal fluid (CSF) surrounding the ON. These measures are generally taken at an arbitrary point along the nerve and do not account for changes along the length of the ON. We propose a high contrast and high-resolution 3-D acquired isotropic imaging sequence optimized for ON imaging. We have acquired scan-rescan data using the optimized sequence and a current standard of care protocol for 10 subjects. We show that this sequence has superior contrast-to-noise ratio to the current standard of care while achieving a factor of 11 higher resolution. We apply a previously published automatic pipeline to segment the ON and CSF sheath and measure the size of each individually. We show that these measures of ON size have lower short- term reproducibility than the population variance and the variability along the length of the nerve. We find that the proposed imaging protocol is (1) useful in detecting population differences and local changes and (2) a promising tool for investigating biomarkers related to structural changes of the ON.

  11. Patterned growth of high aspect ratio silicon wire arrays at moderate temperature

    Science.gov (United States)

    Morin, Christine; Kohen, David; Tileli, Vasiliki; Faucherand, Pascal; Levis, Michel; Brioude, Arnaud; Salem, Bassem; Baron, Thierry; Perraud, Simon

    2011-04-01

    High aspect ratio silicon wire arrays with excellent pattern fidelity over wafer-scale area were grown by chemical vapor deposition at moderate temperature, using a gas mixture of silane and hydrogen chloride. An innovative two-step process was developed for in situ doping of silicon wires by diborane. This process led to high p-type doping levels, up to 10 18-10 19 cm -3, without degradation of the silicon wire array pattern fidelity.

  12. A 3-dimensional in vitro model of epithelioid granulomas induced by high aspect ratio nanomaterials

    Directory of Open Access Journals (Sweden)

    Hurt Robert H

    2011-05-01

    Full Text Available Abstract Background The most common causes of granulomatous inflammation are persistent pathogens and poorly-degradable irritating materials. A characteristic pathological reaction to intratracheal instillation, pharyngeal aspiration, or inhalation of carbon nanotubes is formation of epithelioid granulomas accompanied by interstitial fibrosis in the lungs. In the mesothelium, a similar response is induced by high aspect ratio nanomaterials, including asbestos fibers, following intraperitoneal injection. This asbestos-like behaviour of some engineered nanomaterials is a concern for their potential adverse health effects in the lungs and mesothelium. We hypothesize that high aspect ratio nanomaterials will induce epithelioid granulomas in nonadherent macrophages in 3D cultures. Results Carbon black particles (Printex 90 and crocidolite asbestos fibers were used as well-characterized reference materials and compared with three commercial samples of multiwalled carbon nanotubes (MWCNTs. Doses were identified in 2D and 3D cultures in order to minimize acute toxicity and to reflect realistic occupational exposures in humans and in previous inhalation studies in rodents. Under serum-free conditions, exposure of nonadherent primary murine bone marrow-derived macrophages to 0.5 μg/ml (0.38 μg/cm2 of crocidolite asbestos fibers or MWCNTs, but not carbon black, induced macrophage differentiation into epithelioid cells and formation of stable aggregates with the characteristic morphology of granulomas. Formation of multinucleated giant cells was also induced by asbestos fibers or MWCNTs in this 3D in vitro model. After 7-14 days, macrophages exposed to high aspect ratio nanomaterials co-expressed proinflammatory (M1 as well as profibrotic (M2 phenotypic markers. Conclusions Induction of epithelioid granulomas appears to correlate with high aspect ratio and complex 3D structure of carbon nanotubes, not with their iron content or surface area. This model

  13. 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.

  14. Design and Analyses of High Aspect Ratio Nozzles for Distributed Propulsion Acoustic Measurements

    Science.gov (United States)

    Dippold, Vance F., III

    2016-01-01

    A series of three convergent round-to-rectangular high-aspect ratio nozzles were designed for acoustics measurements. The nozzles have exit area aspect ratios of 8:1, 12:1, and 16:1. With septa inserts, these nozzles will mimic an array of distributed propulsion system nozzles, as found on hybrid wing-body aircraft concepts. Analyses were performed for the three nozzle designs and showed that the flow through the nozzles was free of separated flow and shocks. The exit flow was mostly uniform with the exception of a pair of vortices at each span-wise end of the nozzle.

  15. Proton beam writing and electroplating for the fabrication of high aspect ratio Au microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Yue Weisheng [Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Ren Yaping [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore); Kan, Jeroen Anton van; Chiam, S.-Y. [Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Jian, Linke; Moser, Herbert O. [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore); Osipowicz, Thomas [Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore 117542 (Singapore)], E-mail: phyto@nus.edu.sg; Watt, Frank [Centre for Ion Beam Applications, Department of Physics, National University of Singapore, Singapore 117542 (Singapore)

    2009-07-01

    We present an approach to fabricate tall high aspect ratio Au microstructures by means of proton beam direct writing. Combining proton beam direct writing and electroplating, we successfully produced gold structures with sub-micrometer lateral dimensions, structure heights in excess of 11 {mu}m, and aspect ratios over 28. Sidewall quality of the Au structures was improved by lowering the process temperature to 20 deg. C when developing PMMA patterns with GG developer. The application of such structures as X-ray masks for deep X-ray lithography with synchrotron radiation was demonstrated.

  16. Electro-mechanical power coupling system for PHEV with high price-performance ratio

    Institute of Scientific and Technical Information of China (English)

    Federmann Florian; Yue CHENG; Xin LI; Bo ZHANG; Jia-jia XIE; Yang YU

    2014-01-01

    The price-performance ratio of PHEV determines its market penetration.Besides en-gine and battery,the power coupling system including traction motor and automatic transmission is a key influence factor of system performance and costs.This article introduces an electro-me-chanical power coupling system for PHEV with high price-performance ratio,which integrates an electro-mechanical CVT and a flat traction motor.As an example,a PHEV system is configured to conform the vehicle dynamic specifications.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. 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...

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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).

  10. 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.

  11. 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.

  12. 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.

  13. A review on non-linear aeroelasticity of high aspect-ratio wings

    Science.gov (United States)

    Afonso, Frederico; Vale, José; Oliveira, Éder; Lau, Fernando; Suleman, Afzal

    2017-02-01

    Current economic constraints and environmental regulations call for design of more efficient aircraft configurations. An observed trend in aircraft design to reduce the lift induced drag and improve fuel consumption and emissions is to increase the wing aspect-ratio. However, a slender wing is more flexible and subject to higher deflections under the same operating conditions. This effect may lead to changes in dynamic behaviour and in aeroelastic response, potentially resulting in instabilities. Therefore, it is important to take into account geometric non-linearities in the design of high aspect-ratio wings, as well as having accurate computational codes that couple the aerodynamic and structural models in the presence of non-linearities. Here, a review on the state-of-the-art on non-linear aeroelasticity of high aspect-ratio wings is presented. The methodologies employed to analyse high aspect-ratio wings are presented and their applications discussed. Important observations from the state-of-the-art studies are drawn and the current challenges in the field are identified.

  14. Design and implementation of a high dimming ratio LED drive controller

    Institute of Scientific and Technical Information of China (English)

    徐孝如; 吴晓波; 赵梦恋; 严晓浪

    2009-01-01

    This paper presents a high dimming ratio light emitting diode (LED) drive controller chip with digital mode dimming (DMD). The chip is composed of a boost power converter and a dimming control block. A novel constant on time (COT) control strategy is proposed for boost converter to achieve high dimming ratio. In addition, a fast enough load transient response of the converter power stage ensures its high dimming ratio. The COT control circuit operates mainly based on two current-capacitor timers and a finite state machine (FSM). The LED drive con-troller chip is designed and fabricated in 1.5μm bipolar CMOS-DMOS (BCD) process with a die area of 1.31 × 1.43 mm2. Experimental results show that the proposed LED drive system works well. And, as expected, the minimum LED dimming on time of 1.0μs and the corresponding dimming ratio of 1000 : 1 at 1 kHz dimming frequency are successfully achieved.

  15. 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.

  16. 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.

  17. Immiscible multicomponent lattice Boltzmann model for fluids with high relaxation time ratio

    Indian Academy of Sciences (India)

    Tao Jiang; Qiwei Gong; Ruofan Qiu; Anlin Wang

    2014-10-01

    An immiscible multicomponent lattice Boltzmann model is developed for fluids with high relaxation time ratios, which is based on the model proposed by Shan and Chen (SC). In the SC model, an interaction potential between particles is incorporated into the discrete lattice Boltzmann equation through the equilibrium velocity. Compared to the SC model, external forces in our model are discretized directly into the discrete lattice Boltzmann equation, as proposed by Guo et al. We develop it into a new multicomponent lattice Boltzmann (LB) model which has the ability to simulate immiscible multicomponent fluids with relaxation time ratio as large as 29.0 and to reduce `spurious velocity’. In this work, the improved model is validated and studied using the central bubble case and the rising bubble case. It finds good applications in both static and dynamic cases for multicomponent simulations with different relaxation time ratios.

  18. Single-Molecule Diodes with High On/Off Ratios Through Environmental Control

    Science.gov (United States)

    Capozzi, Brian; Xia, Jianlong; Dell, Emma; Adak, Olgun; Liu, Zhen-Fei; Neaton, Jeffrey; Campos, Luis; Venkataraman, Latha

    2015-03-01

    Single-Molecule diodes were first proposed with an asymmetric molecule comprising a donor-bridge-acceptor architecture to mimic a semiconductor p-n junction. Progress in molecular electronics has led to the realization of several single-molecule diodes; these have relied on asymmetric molecular backbones, asymmetric molecule-electrode linkers, or asymmetric electrode materials. Despite these advances, molecular diodes have had limited potential for functional applications due to several pitfalls, including low rectification ratios (``on''/``off'' current ratios environment instead of an asymmetric molecule, we reproducibly achieve high rectification ratios at low operating voltages for molecular junctions based on a family of symmetric small-gap molecules. This technique serves as an unconventional approach for developing functional molecular-scale devices and probing their charge transport characteristics. Furthermore, this technique should be applicable to other nanoscale devices, providing a general route for tuning device properties.

  19. Micro precision casting based on investment casting for micro structures with high aspect ratio

    Institute of Scientific and Technical Information of China (English)

    YANG Chuang; LI Bang-sheng; REN Ming-xing; FU Heng-zhi

    2009-01-01

    Microcasting is one of the significant technologies for the production of metallic micro parts with high aspect ratio (ratio of flow length to diameter). A micro precision casting technology based on investment casting using centrifugal method was investigated. The micro parts of Zn-4%Al alloy with an aspect ratio up to 200 was produced at the centrifugal speed of 1 500 r/min and the mold temperature of 270 ℃. The investigations on the relationship between flow length and rotational speed were carried out. For microcasting, the flow length is not only dependent on the centrifugal speed under the constant centrifugal radius, but also on the preheating temperature of mold. The flow length increases as the rotational speed and the mold temperature increase, and is much higher at a mold temperature of 270 ℃ than at other mold temperatures.

  20. A simple method for fabrication of high-aspect-ratio all-silicon grooves

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yuncan; Pan, An; Si, Jinhai, E-mail: jinhaisi@mail.xjtu.edu.cn; Chen, Tao; Chen, Feng; Hou, Xun

    2013-11-01

    A simple method using 800-nm femtosecond laser irradiation and chemical selective etching has been proposed for fabrication of high-aspect-ratio all-silicon grooves. Grooves with the maximum aspect ratio of 44 were produced. A scanning electronic microscopy equipped with an energy dispersive X-ray spectroscopy was employed to characterize the morphology and chemical composition of the grooves respectively. The formation mechanism of the grooves was attributed to the chemical reaction of the laser induced refractive index change microstructures and hydrofluoric acid solution. The dependences of the aspect ratio of the grooves on the laser irradiation parameters, such as: the numerical aperture of the microscope objective lens, the laser average power and the laser scanning velocity, are discussed.

  1. Fabrication of nanopore and nanoparticle arrays with high aspect ratio AAO masks

    Science.gov (United States)

    Li, Z. P.; Xu, Z. M.; Qu, X. P.; Wang, S. B.; Peng, J.; Mei, L. H.

    2017-03-01

    How to use high aspect ratio anodic aluminum oxide (AAO) membranes as an etching and evaporation mask is one of the unsolved problems in the application of nanostructured arrays. Here we describe the versatile utilizations of the highly ordered AAO membranes with a high aspect ratio of more than 20 used as universal masks for the formation of various nanostructure arrays on various substrates. The result shows that the fabricated nanopore and nanoparticle arrays of substrates inherit the regularity of the AAO membranes completely. The flat AAO substrates and uneven AAO frontages were attached to the Si substrates respectively as an etching mask, which demonstrates that the two kinds of replication, positive and negative, represent the replication of the mirroring of Si substrates relative to the flat AAO substrates and uneven AAO frontages. Our work is a breakthrough for the broad research field of surface nano-masking.

  2. Simultaneous X-ray diffraction and phase-contrast imaging for investigating material deformation mechanisms during high-rate loading.

    Science.gov (United States)

    Hudspeth, M; Sun, T; Parab, N; Guo, Z; Fezzaa, K; Luo, S; Chen, W

    2015-01-01

    Using a high-speed camera and an intensified charge-coupled device (ICCD), a simultaneous X-ray imaging and diffraction technique has been developed for studying dynamic material behaviors during high-rate tensile loading. A Kolsky tension bar has been used to pull samples at 1000 s(-1) and 5000 s(-1) strain-rates for super-elastic equiatomic NiTi and 1100-O series aluminium, respectively. By altering the ICCD gating time, temporal resolutions of 100 ps and 3.37 µs have been achieved in capturing the diffraction patterns of interest, thus equating to single-pulse and 22-pulse X-ray exposure. Furthermore, the sample through-thickness deformation process has been simultaneously imaged via phase-contrast imaging. It is also shown that adequate signal-to-noise ratios are achieved for the detected white-beam diffraction patterns, thereby allowing sufficient information to perform quantitative data analysis diffraction via in-house software (WBXRD_GUI). Of current interest is the ability to evaluate crystal d-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates.

  3. 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)

  4. High Turndown Ratio, High Delta-Emittance, Variable Emissivity Electrochromics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Variable-emittance materials are in high demand for applications ranging from manned and unmanned space platforms (e.g. in radiators at the Moon's poles where damage...

  5. Flight Loads Prediction of High Aspect Ratio Wing Aircraft Using Multibody Dynamics

    Directory of Open Access Journals (Sweden)

    Michele Castellani

    2016-01-01

    Full Text Available A framework based on multibody dynamics has been developed for the static and dynamic aeroelastic analyses of flexible high aspect ratio wing aircraft subject to structural geometric nonlinearities. Multibody dynamics allows kinematic nonlinearities and nonlinear relationships in the forces definition and is an efficient and promising methodology to model high aspect ratio wings, which are known to be prone to structural nonlinear effects because of the high deflections in flight. The multibody dynamics framework developed employs quasi-steady aerodynamics strip theory and discretizes the wing as a series of rigid bodies interconnected by beam elements, representative of the stiffness distribution, which can undergo arbitrarily large displacements and rotations. The method is applied to a flexible high aspect ratio wing commercial aircraft and both trim and gust response analyses are performed in order to calculate flight loads. These results are then compared to those obtained with the standard linear aeroelastic approach provided by the Finite Element Solver Nastran. Nonlinear effects come into play mainly because of the need of taking into account the large deflections of the wing for flight loads computation and of considering the aerodynamic forces as follower forces.

  6. Plasma-assisted atomic layer deposition of conformal Pt films in high aspect ratio trenches

    Science.gov (United States)

    Erkens, I. J. M.; Verheijen, M. A.; Knoops, H. C. M.; Keuning, W.; Roozeboom, F.; Kessels, W. M. M.

    2017-02-01

    To date, conventional thermal atomic layer deposition (ALD) has been the method of choice to deposit high-quality Pt thin films grown typically from (MeCp)PtMe3 vapor and O2 gas at 300 °C. Plasma-assisted ALD of Pt using O2 plasma can offer several advantages over thermal ALD, such as faster nucleation and deposition at lower temperatures. In this work, it is demonstrated that plasma-assisted ALD at 300 °C also allows for the deposition of highly conformal Pt films in trenches with high aspect ratio ranging from 3 to 34. Scanning electron microscopy inspection revealed that the conformality of the deposited Pt films was 100% in trenches with aspect ratio (AR) up to 34. These results were corroborated by high-precision layer thickness measurements by transmission electron microscopy for trenches with an aspect ratio of 22. The role of the surface recombination of O-radicals and the contribution of thermal ALD reactions is discussed.

  7. 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.

  8. Petrogenetic significance of high Fe/Mn ratios of the Cenozoic basalts from Eastern China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Cenozoic basalts from eastern China show commonly high Fe/Mn ratios (average = 68.6 ± 11.5) coupled with OIB-type trace element signature. The Cenozoic basalts form the northern margin and the southern margin of the North China Craton are studied in detail. Model calculations point out that the coupling feature of high Fe/Mn ratio with OIB-type trace element signature of these basalts cannot be produced by neither pyroxene/olivine crystallization nor remelting of previously melted mantle, but require partial melting of a garnet pyroxenite-rich mantle source. Combining these features of the Cenozoic basalts with the Phanerozoic lithospheric evolution of the eastern China, we suggest that the Cenozoic basalts were derived from a garnet pyroxenite-rich mantle source associated with continental crust delamination or oceanic crust subduction.

  9. An implicit wetting and drying approach for non-hydrostatic flows in high aspect ratio domains

    CERN Document Server

    Candy, Adam S

    2013-01-01

    A wetting and drying approach for free surface flows governed by the three-dimensional, non-hydrostatic Navier-Stokes equations in high aspect ratio domains is developed. This has application in the modelling of inundation processes in geophysical domains, where dynamics takes place over a large horizontal extent relative to vertical resolution, such as in the evolution of a tsunami, or an urban fluvial flooding scenario. The approach is novel in that it solves for three dimensional dynamics in these very high aspect ratio domains, to include non-hydrostatic effects and accurately model dispersive processes. These become important in shallow regions with steep gradients, a particularly acute problem where man-made structures exist such as buildings or flood defences in an urban environment. It is implicit in time to allow efficient time integration over a range of mesh element sizes. Specific regularisation methods are introduced to improve conditioning of the full three-dimensional pressure Poisson problem i...

  10. Optimal design and installation of ultra high bypass ratio turbofan nacelle

    Science.gov (United States)

    Savelyev, Andrey; Zlenko, Nikolay; Matyash, Evgeniy; Mikhaylov, Sergey; Shenkin, Andrey

    2016-10-01

    The paper is devoted to the problem of designing and optimizing the nacelle of turbojet bypass engine with high bypass ratio and high thrust. An optimization algorithm EGO based on development of surrogate models and the method for maximizing the probability of improving the objective function has been used. The designing methodology has been based on the numerical solution of the Reynolds equations system. Spalart-Allmaras turbulence model has been chosen for RANS closure. The effective thrust losses has been uses as an objective function in optimizing the engine nacelle. As a result of optimization, effective thrust has been increased by 1.5 %. The Blended wing body aircraft configuration has been studied as a possible application. Two variants of the engine layout arrangement have been considered. It has been shown that the power plant changes the pressure distribution on the aircraft surface. It results in essential diminishing the configuration lift-drag ratio.

  11. Shear softening of Earth's inner core indicated by its high Poisson's ratio and elastic anisotropy

    CERN Document Server

    Wu, Zhongqing

    2016-01-01

    Earth's inner core exhibits an unusually high Poisson's ratio and noticeable elastic anisotropy. The mechanisms responsible for these features are critical for understanding the evolution of the Earth but remain unclear. This study indicates that once the correct formula for the shear modulus is used, shear softening can simultaneously explain the high Poisson's ratio and strong anisotropy of the inner core. Body-centred-cubic (bcc) iron shows shear instability at the pressures found in the inner-core and can be dynamically stabilized by temperature and light elements. It is very likely that some combinations of light elements stabilize the bcc iron alloy under inner-core conditions. Such a bcc phase would exhibit significant shear softening and match the geophysical constraints of the inner core. Identifying which light elements and what concentrations of these elements stabilize the bcc phase will provide critical information on the light elements of the inner core.

  12. Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

    Science.gov (United States)

    Li, Ting

    2013-08-13

    The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

  13. High aspect ratio tungsten grating on ultrathin Si membranes for extreme UV lithography

    Science.gov (United States)

    Peng, Xinsheng; Ying, Yulong

    2016-09-01

    Extreme ultraviolet lithography is one of the modern lithography tools for high-volume manufacturing with 22 nm resolution and beyond. But critical challenges exist to the design and fabrication of large-scale and highly efficient diffraction transmission gratings, significantly reducing the feature sizes down to 22 nm and beyond. To achieve such a grating, the surface flatness, the line edge roughness, the transmission efficiency and aspect ratio should be improved significantly. Delachat et al (2015 Nanotechnology 26 108262) develop a full process to fabricate a tungsten diffraction grating on an ultrathin silicon membrane with higher aspect ratio up to 8.75 that met all the aforementioned requirements for extreme ultraviolet lithography. This process is fully compatible with standard industrial extreme ultraviolet lithography.

  14. High aspect ratio tungsten grating on ultrathin Si membranes for extreme UV lithography.

    Science.gov (United States)

    Peng, Xinsheng; Ying, Yulong

    2016-09-02

    Extreme ultraviolet lithography is one of the modern lithography tools for high-volume manufacturing with 22 nm resolution and beyond. But critical challenges exist to the design and fabrication of large-scale and highly efficient diffraction transmission gratings, significantly reducing the feature sizes down to 22 nm and beyond. To achieve such a grating, the surface flatness, the line edge roughness, the transmission efficiency and aspect ratio should be improved significantly. Delachat et al (2015 Nanotechnology 26 108262) develop a full process to fabricate a tungsten diffraction grating on an ultrathin silicon membrane with higher aspect ratio up to 8.75 that met all the aforementioned requirements for extreme ultraviolet lithography. This process is fully compatible with standard industrial extreme ultraviolet lithography.

  15. Few-layer SnSe{sub 2} transistors with high on/off ratios

    Energy Technology Data Exchange (ETDEWEB)

    Pei, Tengfei; Bao, Lihong, E-mail: lhbao@iphy.ac.cn; Wang, Guocai; Ma, Ruisong; Yang, Haifang; Li, Junjie; Gu, Changzhi; Du, Shixuan; Gao, Hong-jun [Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100190 (China); Pantelides, Sokrates [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Material Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37381 (United States)

    2016-02-01

    We report few-layer SnSe{sub 2} field effect transistors (FETs) with high current on/off ratios. By trying different gate configurations, 300 nm SiO{sub 2} and 70 nm HfO{sub 2} as back gate only and 70 nm HfO{sub 2} as back gate combined with a top capping layer of polymer electrolyte, few-layer SnSe{sub 2} FET with a current on/off ratio of 10{sup 4} can be obtained. This provides a reliable solution for electrically modulating quasi-two-dimensional materials with high electron density (over 10{sup 13} cm{sup −2}) for field-effect transistor applications.

  16. Petrogenetic significance of high Fe/Mn ratios of the Cenozoic basalts from Eastern China

    Institute of Scientific and Technical Information of China (English)

    ZHANG BinHui; LIU YongSheng; GAO Shan

    2008-01-01

    The Cenozoic basalts from eastern China show commonly high Fe/Mn ratios (average = 68.6 卤 11.5) coupled with OIB-type trace element signature. The Cenozoic basalts form the northern margin and the southern margin of the North China Craton are studied in detail. Model calculations point out that the coupling feature of high Fe/Mn ratio with OIB-type trace element signature of these basalts cannot be produced by neither pyroxene/olivine crystallization nor remelting of previously melted mantle, but require partial melting of a garnet pyroxenite-rich mantle source. Combining these features of the Cenozoic basalts with the Phanerozoic lithospheric evolution of the eastern China, we suggest that the Cenozoic basalts were derived from a garnet pyroxenite-rich mantle source associated with continental crust delamination or oceanic crust subduction.

  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. 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.

  3. 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.

  4. 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.

  5. On the Elastic Vibration Model for High Length-Diameter Ratio Rocket with Attitude Control System

    Institute of Scientific and Technical Information of China (English)

    朱伯立; 杨树兴

    2003-01-01

    An elastic vibration model for high length-diameter ratio spinning rocket with attitude control system which can be used for trajectory simulation is established. The basic theory of elastic dynamics and vibration dynamics were both used to set up the elastic vibration model of rocket body. In order to study the problem more conveniently, the rocket's body was simplified to be an even beam with two free ends. The model was validated by simulation results and the test data.

  6. Prediction of failure strain and burst pressure in high yield-to-tensile strength ratio linepipe

    Energy Technology Data Exchange (ETDEWEB)

    Law, M. [Institute of Materials and Engineering Science, Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia)]. E-mail: mlx@ansto.gov.au; Bowie, G. [BlueScope Steel Ltd., Level 11, 120 Collins St, Melbourne, Victoria 3000 (Australia)

    2007-08-15

    Failure pressures and strains were predicted for a number of burst tests as part of a project to explore failure strain in high yield-to-tensile strength ratio linepipe. Twenty-three methods for predicting the burst pressure and six methods of predicting the failure strain are compared with test results. Several methods were identified which gave accurate and reliable estimates of burst pressure. No method of accurately predicting the failure strain was found, though the best was noted.

  7. 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.

  8. Simulation and Measurement of Neuroelectrodes' Characteristics with Integrated High Aspect Ratio Nano Structures

    Directory of Open Access Journals (Sweden)

    Christoph Nick

    2015-07-01

    Full Text Available Improving the interface between electrodes and neurons has been the focus of research for the last decade. Neuroelectrodes should show small geometrical surface area and low impedance for measuring and high charge injection capacities for stimulation. Increasing the electrochemically active surface area by using nanoporous electrode material or by integrating nanostructures onto planar electrodes is a common approach to improve this interface. In this paper a simulation approach for neuro electrodes' characteristics with integrated high aspect ratio nano structures based on a point-contact-model is presented. The results are compared with experimental findings conducted with real nanostructured microelectrodes. In particular, effects of carbon nanotubes and gold nanowires integrated onto microelectrodes are described. Simulated and measured impedance properties are presented and its effects onto the transfer function between the neural membrane potential and the amplifier output signal are studied based on the point-contact-model. Simulations show, in good agreement with experimental results, that electrode impedances can be dramatically reduced by the integration of high aspect ratio nanostructures such as gold nanowires and carbon nanotubes. This lowers thermal noise and improves the signal-to-noise ratio for measuring electrodes. It also may increase the adhesion of cells to the substrate and thus increase measurable signal amplitudes.

  9. Fabrication of Aspheric Micro-Lens Mold with High Aspect Ratio

    Science.gov (United States)

    Naniwa, Irizo; Kanamaru, Masatoshi; Nakamura, Shigeo; Shimano, Takeshi; Horino, Masaya

    The optical pickup of our Small-Form-Factor Optical Disc Drives (SFFODDs) requires a micro-objective whose profile is composed of two aspheric surfaces. However, it is difficult to fabricate a micro-objective with an arbitrary aspheric surface and high aspect ratio using conventional techniques. We propose here a new method to fabricate an aspheric micro-lens mold with high aspect ratio. This method uses the micro-loading effect in Deep Reactive Ion Etching (DRIE) and isotropic Reactive Ion Etching (RIE). The micro-loading effect is a phenomenon that leads to different etching depths depending on the aperture size of the mask layer used in etching. We fabricated an aspheric micro-lens mold for the prototype by using the proposed method after experimental evaluations of the micro-loading effect for a feasibility study. The profile of the first prototype was slightly different from the designed one according as the distance from the lens center increase. The profile error of the second prototype was reduced by using a mask that had multiple apertures with the smallest aperture located outside the area where the crater was formed. Our proposed method was found to be effective for fabricating a micro-lens mold with an arbitrary aspheric surface and high aspect ratio.

  10. δ-Phosphorene: a two dimensional material with a highly negative Poisson's ratio.

    Science.gov (United States)

    Wang, Haidi; Li, Xingxing; Li, Pai; Yang, Jinlong

    2017-01-05

    As a basic mechanical parameter, Poisson's ratio (ν) measures the mechanical responses of solids against external loads. In rare cases, materials have a negative Poisson's ratio (NPR), and present an interesting auxetic effect. That is, when a material is stretched in one direction, it will expand in the perpendicular direction. To design modern nanoscale electromechanical devices with special functions, two dimensional (2D) auxetic materials are highly desirable. In this work, based on first principles calculations, we rediscover the previously proposed δ-phosphorene (δ-P) nanosheets [Jie Guan, et al., Phys. Rev. Lett., 2014, 113, 046804] which are good auxetic materials with a high NPR. The results show that the Young's modulus and Poisson's ratio of δ-P are all anisotropic. The NPR value along the grooved direction is up to -0.267, which is much higher than the recently reported 2D auxetic materials. The auxetic effect of δ-P originating from its puckered structure is robust and insensitive to the number of layers due to weak interlayer interactions. Moreover, δ-P possesses good flexibility because of its relatively small Young's modulus and high critical crack strain. If δ-P can be synthesized, these extraordinary properties would endow it with great potential in designing low dimensional electromechanical devices.

  11. High contrast tumor imaging with radio-labeled antibody Fab fragments tailored for optimized pharmacokinetics via PASylation.

    Science.gov (United States)

    Mendler, Claudia T; Friedrich, Lars; Laitinen, Iina; Schlapschy, Martin; Schwaiger, Markus; Wester, Hans-Jürgen; Skerra, Arne

    2015-01-01

    Although antigen-binding fragments (Fabs) of antibodies constitute established tracers for in vivo radiodiagnostics, their functionality is hampered by a very short circulation half-life. PASylation, the genetic fusion with a long, conformationally disordered amino acid chain comprising Pro, Ala and Ser, provides a convenient way to expand protein size and, consequently, retard renal filtration. Humanized αHER2 and αCD20 Fabs were systematically fused with 100 to 600 PAS residues and produced in E. coli. Cytofluorimetric titration analysis on tumor cell lines confirmed that antigen-binding activities of the parental antibodies were retained. The radio-iodinated PASylated Fabs were studied by positron emission tomography (PET) imaging and biodistribution analysis in mouse tumor xenograft models. While the unmodified αHER2 and αCD20 Fabs showed weak tumor uptake (0.8% and 0.2% ID/g, respectively; 24 h p.i.) tumor-associated radioactivity was boosted with increasing PAS length (up to 9 and 26-fold, respectively), approaching an optimum for Fab-PAS400. Remarkably, 6- and 5-fold higher tumor-to-blood ratios compared with the unmodified Fabs were measured in the biodistribution analysis (48 h p.i.) for αHER2 Fab-PAS100 and Fab-PAS200, respectively. These findings were confirmed by PET studies, showing high imaging contrast in line with tumor-to-blood ratios of 12.2 and 5.7 (24 h p.i.) for αHER2 Fab-PAS100 and Fab-PAS200. Even stronger tumor signals were obtained with the corresponding αCD20 Fabs, both in PET imaging and biodistribution analysis, with an uptake of 2.8% ID/g for Fab-PAS100 vs. 0.24% ID/g for the unmodified Fab. Hence, by engineering Fabs via PASylation, plasma half-life can be tailored to significantly improve tracer uptake and tumor contrast, thus optimally matching reagent/target interactions.

  12. High triglyceride-to-HDL cholesterol ratio associated with albuminuria in type 2 diabetic subjects.

    Science.gov (United States)

    Lee, I Te; Wang, Chih-Yuan; Huang, Chien-Ning; Fu, Chen-Chung; Sheu, Wayne H H

    2013-01-01

    Emerging evidence indicates that metabolic syndrome (MetS) predisposes diabetic subjects to nephropathy. Aside from hypertension and hyperglycemia, it is unclear which component of MetS also contributes to increased urinary albumin excretion (UAE). We compared the MetS profiles of subjects divided into two groups based on their UAE. The Asia Pacific Real-Life Effectiveness and Care Patterns of Diabetes Management (AP RECAP-DM) study is a cross-sectional survey in which type 2 diabetic subjects using oral anti-hyperglycemic drugs were enrolled. We analyzed the data of 162 type 2 diabetic subjects with normotension or taking antihypertensive medications. There were 123 subjects with normal UAE (HDL) cholesterol (odds ratio=3.27, P=0.022) were both independently associated with abnormal UAE. Using 3.4 as a cut-off value, a high triglyceride-to-HDL cholesterol ratio was a useful marker (odds ratio=15.05, PHDL cholesterol ratio was found to be an important risk factor for nephropathy in type 2 diabetic subjects. Copyright © 2013 Elsevier Inc. All rights reserved.

  13. High tunneling magnetoresistance ratio in perpendicular magnetic tunnel junctions using Fe-based Heusler alloys

    Science.gov (United States)

    Wang, Yu-Pu; Lim, Sze-Ter; Han, Gu-Chang; Teo, Kie-Leong

    2015-12-01

    Heulser alloys Fe2Cr1-xCoxSi (FCCS) with different Co compositions x have been predicted to have high spin polarization. High perpendicular magnetic anisotropy (PMA) has been observed in ultra-thin FCCS films with magnetic anisotropy energy density up to 2.3 × 106 erg/cm3. The perpendicular magnetic tunnel junctions (p-MTJs) using FCCS films with different Co compositions x as the bottom electrode have been fabricated and the post-annealing effects have been investigated in details. An attractive tunneling magnetoresistance ratio as high as 51.3% is achieved for p-MTJs using Fe2CrSi (FCS) as the bottom electrode. The thermal stability Δ can be as high as 70 for 40 nm dimension devices using FCS, which is high enough to endure a retention time of over 10 years. Therefore, Heusler alloy FCS is a promising PMA candidate for p-MTJ application.

  14. Design requirements for high-efficiency high concentration ratio space solar cells

    Science.gov (United States)

    Rauschenbach, H.; Patterson, R.

    1980-01-01

    A miniaturized Cassegrainian concentrator system concept was developed for low cost, multikilowatt space solar arrays. The system imposes some requirements on solar cells which are new and different from those imposed for conventional applications. The solar cells require a circular active area of approximately 4 mm in diameter. High reliability contacts are required on both front and back surfaces. The back area must be metallurgically bonded to a heat sink. The cell should be designed to achieve the highest practical efficiency at 100 AMO suns and at 80 C. The cell design must minimize losses due to nonuniform illumination intensity and nonnormal light incidence. The primary radiation concern is the omnidirectional proton environment.

  15. 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.)

  16. Characterization of a custom-built RF coil for a high-resolution phase-contrast magnetic resonance velocimeter

    Science.gov (United States)

    Yang, Byungkuen; Cho, Jee-Hyun; Song, Simon

    2016-11-01

    For the use of clinical purpose magnetic resonance velocimeter (MRV) is a versatile flow visualization technique in that it allows opaque flow, complex geometry, no use of tracer particles and facile fast non-invasive measurements of 3 dimensional and 3 component velocity vectors. However, the spatial resolution of a commercial MR machine is lower than optics-based techniques like PIV. On the other hand, the use of MRV for clinical purposes like cardiovascular flow visualization requires accurate measurements or estimations on wall shear stress (WSS) with a high spatial resolution. We developed a custom-built solenoid RF coil for phase-contrast (PC) MRV to improve its resolution. We compared signal-to-noise ratio, WSS estimations, partial volume effects near wall between the custom RF coil and a commercial coil. Also, a Hagen-Poiseuille flow was analyzed with the custom RF coil. This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIP) (No. 2016R1A2B3009541).

  17. Characterization of a photon counting EMCCD for space-based high contrast imaging spectroscopy of extrasolar planets

    CERN Document Server

    Wilkins, Ashlee N; Norton, Timothy J; Rauscher, Bernard J; Rothe, Johannes F; Malatesta, Michael; Hilton, George M; Bubeck, James R; Grady, Carol A; Lindler, Don J

    2014-01-01

    We present the progress of characterization of a low-noise, photon counting Electron Multiplying Charged Coupled Device (EMCCD) operating in optical wavelengths and demonstrate possible solutions to the problems of Clock-Induced Charge (CIC) and other trapped charge through sub-bandgap illumination. Such a detector will be vital to the feasibility of future space-based direct imaging and spectroscopy missions for exoplanet characterization, and is scheduled to fly on-board the AFTA-WFIRST mission. The 512$\\times$512 EMCCD is an e2v detector housed and clocked by a N\\"uv\\"u Cameras controller. Through a multiplication gain register, this detector produces as many as 5000 electrons for a single, incident-photon-induced photoelectron produced in the detector, enabling single photon counting operation with read noise and dark current orders of magnitude below that of standard CCDs. With the extremely high contrasts (Earth-to-Sun flux ratio is $\\sim$ 10$^{-10}$) and extremely faint targets (an Earth analog would m...

  18. 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.

  19. Nanometer scale high-aspect-ratio trench etching at controllable angles using ballistic reactive ion etching

    Energy Technology Data Exchange (ETDEWEB)

    Cybart, Shane; Roediger, Peter; Ulin-Avila, Erick; Wu, Stephen; Wong, Travis; Dynes, Robert

    2012-11-30

    We demonstrate a low pressure reactive ion etching process capable of patterning nanometer scale angled sidewalls and three dimensional structures in photoresist. At low pressure the plasma has a large dark space region where the etchant ions have very large highly-directional mean free paths. Mounting the sample entirely within this dark space allows for etching at angles relative to the cathode with minimal undercutting, resulting in high-aspect ratio nanometer scale angled features. By reversing the initial angle and performing a second etch we create three-dimensional mask profiles.

  20. 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.

  1. 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.

  2. 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.

  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. 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 ...

  5. 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.

  6. 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...

  7. 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.

  8. 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.

  9. 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...

  10. 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.

  11. 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.

  12. Compact diode-laser spectrometer ISOWAT for highly sensitive airborne measurements of water-isotope ratios

    Science.gov (United States)

    Dyroff, C.; Fütterer, D.; Zahn, A.

    2010-02-01

    The tunable diode-laser absorption spectrometer ISOWAT for airborne measurements of the water-isotope ratios 18O/16O and D/H is described. The spectrometer uses a distributed feedback (DFB) diode laser to probe fundamental rovibrational water-absorption lines at around 2.66 μm. Very-low-noise system components along with signal averaging allow for a detection limit of 1.2 and 4.5 ‰ for measurements of 18O/16O and D/H, respectively, for a water-vapour mixing ratio of 100 ppmv and an averaging time of 60 s. This corresponds to a minimum detectable absorbance of ˜5×10-6 or ˜6.6×10-10 cm-1 when normalized to pathlength. In addition to its high sensitivity, the spectrometer is highly compact (19-inch rack at a height of 35 cm, excluding pump and calibration unit) and light weight (automated. ISOWAT will be calibrated during flight with known water-isotope ratios using a compact calibration-gas source.

  13. a Brief Climatology of Cirrus LIDAR Ratios Measured by High Spectral Resolution LIDAR

    Science.gov (United States)

    Kuehn, R.; Holz, R.; Hair, J. W.; Vaughan, M. A.; Eloranta, E. W.

    2015-12-01

    Our ability to detect and probe the vertical extent of cirrus was hugely improved with the launch of the NASA-CNES CALIPSO mission in April 2006. However, our skill at retrieving the optical properties of the cirrus detected by the CALIPSO lidar is not yet commensurate with our detection abilities. As with any new observing system, CALIPSO faces challenges and uncertainties in the retrieval of the geophysical parameters from its fundamental measurements. Specifically, extinction and optical depth retrievals for elastic backscatter lidars like CALIPSO typically rely on a priori assumptions about layer-mean extinction-to-backscatter ratios (AKA lidar ratios), which can vary regionally and for which uncertainties are high. To improve CALIPSO optical properties retrievals, we show High Spectral Resolution Lidar (HSRL) measurements acquired with systems from the University of Wisconsin and NASA Langley. HSRLs can directly determine ice cloud extinction and lidar ratio by separately measuring the molecular and particulate components of the total backscattered signal, thus largely eliminating many of the uncertainties inherent in elastic backscatter retrievals. These measurements were acquired during the SEAC4RS (Huntsville, AL, USA and Singapore), and FRAPPE/DISCOVER-AQ 2014 (BAO tower near Boulder, CO, USA) field campaigns, and an intensive operations period in Hampton, VA, USA.

  14. Podiatry impact on high-low amputation ratio characteristics: A 16-year retrospective study.

    Science.gov (United States)

    Schmidt, Brian M; Wrobel, James S; Munson, Michael; Rothenberg, Gary; Holmes, Crystal M

    2017-04-01

    Complications from diabetes mellitus including major lower extremity amputation may have significant impact on a patient's mortality. This study determined what impact the addition of a limb salvage and diabetic foot program involving podiatry had at an academic institution over 16years by analyzing high-low amputation ratio data. The high-low amputation ratio in the diabetic population who underwent non-traumatic amputation of the lower extremity was retrospectively evaluated at an academic institution via cohort discovery of the electronic medical record and analysis of billing over 16years. We directly compared two eras, one without podiatry and one with a podiatry presence. It was found that with the addition of a podiatry program, limb salvage rates significantly increased (R(2) (without podiatry)=0.45, R(2) (with podiatry)=0.26), with a significant change in both the rate of limb salvage per year (-0.11% per year versus -0.36% per year; pamputation ratio (0.89 without podiatry to 0.60 with podiatry). Of note, approximately 40 major lower extremity amputations were avoided per year with the addition of a podiatry program (pamputations can be avoided and more limbs can be salvaged, thus preventing some of the moribund complications from this condition. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. High Bypass Ratio Jet Noise Reduction and Installation Effects Including Shielding Effectiveness

    Science.gov (United States)

    Thomas, Russell H.; Czech, Michael J.; Doty, Michael J.

    2013-01-01

    An experimental investigation was performed to study the propulsion airframe aeroacoustic installation effects of a separate flow jet nozzle with a Hybrid Wing Body aircraft configuration where the engine is installed above the wing. Prior understanding of the jet noise shielding effectiveness was extended to a bypass ratio ten application as a function of nozzle configuration, chevron type, axial spacing, and installation effects from additional airframe components. Chevron types included fan chevrons that are uniform circumferentially around the fan nozzle and T-fan type chevrons that are asymmetrical circumferentially. In isolated testing without a pylon, uniform chevrons compared to T-fan chevrons showed slightly more low frequency reduction offset by more high frequency increase. Phased array localization shows that at this bypass ratio chevrons still move peak jet noise source locations upstream but not to nearly the extent, as a function of frequency, as for lower bypass ratio jets. For baseline nozzles without chevrons, the basic pylon effect has been greatly reduced compared to that seen for lower bypass ratio jets. Compared to Tfan chevrons without a pylon, the combination with a standard pylon results in more high frequency noise increase and an overall higher noise level. Shielded by an airframe surface 2.17 fan diameters from nozzle to airframe trailing edge, the T-fan chevron nozzle can produce reductions in jet noise of as much as 8 dB at high frequencies and upstream angles. Noise reduction from shielding decreases with decreasing frequency and with increasing angle from the jet inlet. Beyond an angle of 130 degrees there is almost no noise reduction from shielding. Increasing chevron immersion more than what is already an aggressive design is not advantageous for noise reduction. The addition of airframe control surfaces, including vertical stabilizers and elevon deflection, showed only a small overall impact. Based on the test results, the best

  16. 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.)

  17. Chemistry in isolation: High CCH/HCO+ line ratio in the AMIGA galaxy CIG 638

    CERN Document Server

    Martin, S; Aladro, R; Espada, D; Argudo-Fernandez, M; Kramer, C; Scott, T C

    2014-01-01

    Multi-molecule observations towards an increasing variety of galaxies have been showing that the relative molecular abundances are affected by the type of activity. However, these studies are biased towards bright active galaxies, which are typically in interaction. We study the molecular composition of one of the most isolated galaxies in the local Universe where the physical and chemical properties of their molecular clouds have been determined by intrinsic mechanisms. We present 3 mm broad band observations of the galaxy CIG 638, extracted from the AMIGA sample of isolated galaxies. The emission of the J=1-0 transitions of CCH, HCN, HCO+, and HNC are detected. Integrated intensity ratios between these line are compared with similar observations from the literature towards active galaxies including starburst galaxies (SB), active galactic nuclei (AGN), luminous infrared galaxies (LIRG), and GMCs in M33. A significantly high ratio of CCH with respect to HCN, HCO+, and HNC is found towards CIG 638 when compar...

  18. Nanofabrication of low extinction coefficient and high-aspect-ratio Si structures for metaphotonic applications

    Science.gov (United States)

    Lee, JeongYub; Song, Byonggwon; Kim, Jaekwan; Lee, Chang-Won; Han, Seunghoon; Baik, Chan-Wook; Jeong, Heejeong; Kim, Yongsung; Lee, Chang Seung

    2016-09-01

    We investigated forming of high refractive index (n), low extinction coefficient (k) of Si dielectrics in visible wavelength ranges. To decrease k, pulsed green laser annealing (GLA) with line beam of a 532-nm wavelength was applied in this study for homogeneous melting. By AFM, XRD and TEM analysis, we examined the defect reduction in various conditions during poly-crystallization. We achieved dielectric nanostructures having optical properties of n>4.2, k<0.06 at 550 nm wavelength and fine pitches down to 40 nm (aspect ratio 3:1) and 130 nm (aspect ratio 7:1) with +/-5% size accuracy. Finally, we realized optical metasurfaces for optical band filters, flat lens and beam deflectors.

  19. FeII/MgII Emission Line Ratio in High Redshift Quasars

    DEFF Research Database (Denmark)

    Dietrich, M.; Hamann, F.; Appenzeller, I.

    2003-01-01

    We present results of the analysis of near infrared spectroscopic observations of 6 high-redshift quasars (z > 4), emphasizing the measurement of the ultraviolet FeII/MgII emission line strength in order to estimate the beginning of intense star formation in the early universe. To investigate...... the evolution of the FeII/MgII ratio over a wider range in cosmic time, we measured this ratio for composite quasar spectra which cover a redshift range of 0 4 quasars must have started already at an epoch corresponding to z_f = 6 to 9, when the age of the universe was ~0.5 Gyr (H_o = 72 km/s/Mpc, Omega_M = 0...

  20. Hybrid UV Lithography for 3D High-Aspect-Ratio Microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sungmin; Nam, Gyungmok; Kim, Jonghun; Yoon, Sang-Hee [Inha Univ, Incheon (Korea, Republic of)

    2016-08-15

    Three-dimensional (3D) high-aspect-ratio (HAR) microstructures for biomedical applications (e.g., microneedle, microadhesive, etc.) are microfabricated using the hybrid ultraviolet (UV) lithography in which inclined, rotational, and reverse-side UV exposure processes are combined together. The inclined and rotational UV exposure processes are intended to fabricate tapered axisymmetric HAR microstructures; the reverse-side UV exposure process is designed to sharpen the end tip of the microstructures by suppressing the UV reflection on a bottom substrate which is inevitable in conventional UV lithography. Hybrid UV lithography involves fabricating 3D HAR microstructures with an epoxy-based negative photoresist, SU-8, using our customized UV exposure system. The effects of hybrid UV lithography parameters on the geometry of the 3D HAR microstructures (aspect ratio, radius of curvature of the end tip, etc.) are measured. The dependence of the end-tip shape on SU-8 soft-baking condition is also discussed.

  1. Pilot Study of Inhaled Aerosols Targeted via Magnetic Alignment of High Aspect Ratio Particles in Rabbits

    Directory of Open Access Journals (Sweden)

    Gillian E. S. Redman

    2011-01-01

    Full Text Available Recently, inhaled pharmaceutical aerosols have seen increased investigation in the treatment of lung cancer, where the inability to deliver adequate therapeutic drug concentrations to tumour sites may be overcome with improved targeted delivery to the site of the tumour. In this study, the feasibility of magnetically targeted delivery of high aspect ratio particles loaded with iron oxide nanoparticles was studied in 19 New Zealand White rabbits. Half of the exposed rabbits had a magnetic field placed externally over their right lung. Iron sensitive magnetic resonance images of the lungs were acquired to determine the iron concentrations in the right and left lung of each animal. The right/left ratio increased in the middle and basal regions of the lung where, due to the morphology of the rabbit lung, this method of targeting is most effective. With further optimization, this technique could be an effective method for increasing the dose of drug delivered to a specific site within the lung.

  2. High Stellar FUV/NUV Ratio and Oxygen Contents in the Atmospheres of Potentially Habitable Planets

    CERN Document Server

    Tian, Feng; Linsky, Jeffrey L; Mauas, Pablo J D; Vieytes, Mariela C

    2013-01-01

    Recent observations of several planet-hosting M dwarfs show that most have FUV/NUV flux ratios 1000 times greater than that of the Sun. Here we show that the atmospheric oxygen contents (O2 and O3) of potentially habitable planets in this type of UV environment could be 2~3 orders of magnitude greater than those of their counterparts around Sun-like stars as a result of decreased photolysis of O3, H2O2, and HO2. Thus detectable levels of atmospheric oxygen, in combination with the existence of H2O and CO2, may not be the most promising biosignatures on planets around stars with high FUV/NUV ratios such as the observed M dwarfs.

  3. Multiscale Domain Decomposition Methods for Elliptic Problems with High Aspect Ratios

    Institute of Scientific and Technical Information of China (English)

    Jфrg Aarnes; Thomas Y. Hou

    2002-01-01

    In this paper we study some nonoverlapping domain decomposition methods for solving a class of elliptic problems arising from composite materials and flows in porous media which contain many spatial scales. Our preconditioner differs from traditional domain decomposition preconditioners by using a coarse solver which is adaptive to small scale heterogeneous features. While the convergence rate of traditional domain decomposition algorithms using coarse solvers based on linear or polynomial interpolations may deteriorate in the presence of rapid small scale oscillations or high aspect ratios, our preconditioner is applicable to multiplescale problems without restrictive assumptions and seems to have a convergence rate nearly independent of the aspect ratio within the substructures. A rigorous convergence analysis based on the Schwarz framework is carried out, and we demonstrate the efficiency and robustness of the proposed preconditioner through numerical experiments which include problems with multiple-scale coefficients, as well problems with continuous scales.

  4. High precision and high aspect ratio laser drilling: challenges and solutions

    Science.gov (United States)

    Uchtmann, Hermann; He, Chao; Gillner, Arnold

    2016-03-01

    Laser drilling is a very versatile tool to produce high accuracy bores in small and large geometries using different technologies. In large and deep hole drilling laser drilling can be found in drilling cooling holes into turbomachinery components such as turbine blades. In micro drilling, the technology is used for the generation of nozzles and filters. However, especially in macro drilling, the process often causes microstructure changes and induces defects such as recast layers and cracks. The defects are caused by the melt dominated drilling process by using pulse durations in the range of some 100 μm up to a few ms. A solution of this problem is the use of ultrashort pulsed laser radiation with pulse durations in the range of some 100 fs up to a few ps, however with the disadvantage of long drilling times. Thus, the aim of this work is to combine the productive process by using ms pulsed fiber laser radiation with subsequent ablation of existing recast layers at the hole wall by using ultrashort pulsed laser radiation. By using fast scanning techniques the recast layer can be avoided almost completely. With a similar technology also very small hole can be produced. Using a rotating dove prism a circular oscillation of the laser spots is performed and holes are drilled at intervals in 1 mm thick stainless steel (1.4301) by ultra-short laser pulses of 7 ps at 515 nm. The formation of hole and the behavior of energy deposition differ from other drilling strategies due to the helical revolution. The temporal evolution of the hole shape is analyzed by means of SEM techniques from which three drilling phases can be distinguished.

  5. 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.)

  6. 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.

  7. 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.

  8. 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.

  9. Mechanical Design of High Lift Systems for High Aspect Ratio Swept Wings

    Science.gov (United States)

    Rudolph, Peter K. C.

    1998-01-01

    The NASA Ames Research Center is working to develop a methodology for the optimization and design of the high lift system for future subsonic airliners with the involvement of two partners. Aerodynamic analysis methods for two dimensional and three dimensional wing performance with flaps and slats deployed are being developed through a grant with the aeronautical department of the University of California Davis, and a flap and slat mechanism design procedure is being developed through a contract with PKCR, Inc., of Seattle, WA. This report documents the work that has been completed in the contract with PKCR on mechanism design. Flap mechanism designs have been completed for seven (7) different mechanisms with a total of twelve (12) different layouts all for a common single slotted flap configuration. The seven mechanisms are as follows: Simple Hinge, Upside Down/Upright Four Bar Linkage (two layouts), Upside Down Four Bar Linkages (three versions), Airbus A330/340 Link/Track Mechanism, Airbus A320 Link/Track Mechanism (two layouts), Boeing Link/Track Mechanism (two layouts), and Boeing 767 Hinged Beam Four Bar Linkage. In addition, a single layout has been made to investigate the growth potential from a single slotted flap to a vane/main double slotted flap using the Boeing Link/Track Mechanism. All layouts show Fowler motion and gap progression of the flap from stowed to a fully deployed position, and evaluations based on spanwise continuity, fairing size and number, complexity, reliability and maintainability and weight as well as Fowler motion and gap progression are presented. For slat design, the options have been limited to mechanisms for a shallow leading edge slat. Three (3) different layouts are presented for maximum slat angles of 20 deg, 15 deg and 1O deg all mechanized with a rack and pinion drive similar to that on the Boeing 757 airplane. Based on the work of Ljungstroem in Sweden, this type of slat design appears to shift the lift curve so that

  10. Maintaining high precision of isotope ratio analysis over extended periods of time.

    Science.gov (United States)

    Brand, Willi A

    2009-06-01

    Stable isotope ratios are reliable and long lasting process tracers. In order to compare data from different locations or different sampling times at a high level of precision, a measurement strategy must include reliable traceability to an international stable isotope scale via a reference material (RM). Since these international RMs are available in low quantities only, we have developed our own analysis schemes involving laboratory working RM. In addition, quality assurance RMs are used to control the long-term performance of the delta-value assignments. The analysis schemes allow the construction of quality assurance performance charts over years of operation. In this contribution, the performance of three typical techniques established in IsoLab at the MPI-BGC in Jena is discussed. The techniques are (1) isotope ratio mass spectrometry with an elemental analyser for delta(15)N and delta(13)C analysis of bulk (organic) material, (2) high precision delta(13)C and delta(18)O analysis of CO(2) in clean-air samples, and (3) stable isotope analysis of water samples using a high-temperature reaction with carbon. In addition, reference strategies on a laser ablation system for high spatial resolution delta(13)C analysis in tree rings is exemplified briefly.

  11. 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 ...

  12. 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.

  13. Different methods to alter surface morphology of high aspect ratio structures

    Science.gov (United States)

    Leber, M.; Shandhi, M. M. H.; Hogan, A.; Solzbacher, F.; Bhandari, R.; Negi, S.

    2016-03-01

    In various applications such as neural prostheses or solar cells, there is a need to alter the surface morphology of high aspect ratio structures so that the real surface area is greater than geometrical area. The change in surface morphology enhances the devices functionality. One of the applications of altering the surface morphology is of neural implants such as the Utah electrode array (UEA) that communicate with single neurons by charge injection induced stimulation or by recording electrical neural signals. For high selectivity between single cells of the nervous system, the electrode surface area is required to be as small as possible, while the impedance is required to be as low as possible for good signal to noise ratios (SNR) during neural recording. For stimulation, high charge injection and charge transfer capacities of the electrodes are required, which increase with the electrode surface. Traditionally, researchers have worked with either increasing the roughness of the existing metallization (platinum grey, black) or other materials such as Iridium Oxide and PEDOT. All of these previously investigated methods lead to more complicated metal deposition processes that are difficult to control and often have a critical impact on the mechanical properties of the metal films. Therefore, a modification of the surface underneath the electrode's coating will increase its surface area while maintaining the standard and well controlled metal deposition process. In this work, the surfaces of the silicon micro-needles were engineered by creating a defined microstructure on the electrodes surface using several methods such as laser ablation, focused ion beam, sputter etching, reactive ion etching (RIE) and deep reactive ion etching (DRIE). The surface modification processes were optimized for the high aspect ratio silicon structures of the UEA. The increase in real surface area while maintaining the geometrical surface area was verified using scanning electron

  14. Static synthesis of high-quality MCM-22 zeolite with high SiO2/Al2O3 ratio

    Institute of Scientific and Technical Information of China (English)

    LIU Zhicheng; SHEN Shaodian; TIAN Bozhi; SUN Jinyu; TU Bo; ZHAO Dongyuan

    2004-01-01

    We demonstrate a synthesis method to broaden the range of SiO2/Al2O3 ratio (30-100) of high-silica MCM-22 zeolites by prolonging the aging time of the gel before the crystallization. The synthesis conditions such as silica sources, chemical compositions of initial gel and aging time of gel were investigated in detail. High quality MCM-22products with various morphologies have been synthesized by optimize their synthesis conditions. Our results show that increasing of the aging time can make the gel be homogenization and promote their nucleus formation, which may avoid the formation of impurity phase and thus broaden the range of SiO2/Al2O3 ratio.

  15. Online stable carbon isotope ratio measurement in formic acid, acetic acid, methanol and ethanol in water by high performance liquid chromatography-isotope ratio mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Tagami, Keiko [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan)], E-mail: k_tagami@nirs.go.jp; Uchida, Shigeo [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan)

    2008-05-05

    A suitable analysis condition was determined for high performance liquid chromatography-isotope ratio mass spectrometry (HPLC-IRMS) while making sequential measurements of stable carbon isotope ratios of {delta}{sup 13}C in formic acid, acetic acid, methanol and ethanol dissolved in water. For this online column separation method, organic reagents are not applicable due to carbon contamination; thus, water and KH{sub 2}PO{sub 4} at low concentrations were tested as mobile phase in combination with a HyPURITY AQUASTAR{sup TM} column. Formic acid, acetic acid, methanol and ethanol were separated when 2 mM KH{sub 2}PO{sub 4} aqueous solution was used. Under the determined analysis condition for HPLC-IRMS, carbon concentrations could be measured quantitatively as well as carbon isotope ratio when carbon concentration was higher than 0.4 mM L for each chemical.

  16. Millijoule femtosecond micro-Bessel beams for ultra-high aspect ratio machining.

    Science.gov (United States)

    Mitra, Sambit; Chanal, Margaux; Clady, Raphaël; Mouskeftaras, Alexandros; Grojo, David

    2015-08-20

    We report on a functional experimental design for Bessel beam generation capable of handling high-energy ultrashort pulses (up to 1.2 mJ per pulse of 50 fs duration). This allows us to deliver intensities exceeding the breakdown threshold for air or any dielectric along controlled micro-filaments with lengths exceeding 4 mm. It represents an unprecedented upscaling in comparison to recent femtosecond Bessel beam micromachining experiments. We produce void microchannels through glass substrates to demonstrate that aspect ratios exceeding 1200∶1 can be achieved by using single high-intensity pulses. This demonstration must lead to new methodologies for deep-drilling and high-speed cutting applications.

  17. A new multifunctional platform based on high aspect ratio interdigitated NEMS structures

    Energy Technology Data Exchange (ETDEWEB)

    Ghatnekar-Nilsson, S; Karlsson, I; Kvennefors, A; Luo, G; Zela, V; Parker, T; Litwin, A [NEMS AB, Solvegatan 16, S-223 62 Lund (Sweden); Arlelid, M [Electrical and Information Technology, Lund University, PO Box 118, S-221 00 Lund (Sweden); Montelius, L [Solid State Physics/The Nanometer Structure Consortium, Lund University, PO Box 118, S-221 00 Lund (Sweden)], E-mail: andrej.litwin@nems.se

    2009-04-29

    A multifunctional NEMS platform based on a mass-producible, surface relief grating has been developed and fabricated directly in polymer materials. The pattern consists of high aspect ratio interdigitated nanometer-sized pairs of walls and can be produced in a low-complexity one-step patterning process with nanoimprint lithography. In this paper, we demonstrate the usefulness of the platform primarily by showing an application as a high-sensitivity mass sensor in air. The sensors, which are based on the high frequency resonant response of around 200 MHz, show a mass responsivity of the order of 0.1 Hz/zg per wall at room temperature and in ambient air. Their ability to selectively adsorb airborne target molecules, such as thiols, is also demonstrated. We also show that the same device can function as a varactor for electronic circuits based on its large tunable capacitive range.

  18. A new multifunctional platform based on high aspect ratio interdigitated NEMS structures.

    Science.gov (United States)

    Ghatnekar-Nilsson, S; Karlsson, I; Kvennefors, A; Luo, G; Zela, V; Arlelid, M; Parker, T; Montelius, L; Litwin, A

    2009-04-29

    A multifunctional NEMS platform based on a mass-producible, surface relief grating has been developed and fabricated directly in polymer materials. The pattern consists of high aspect ratio interdigitated nanometer-sized pairs of walls and can be produced in a low-complexity one-step patterning process with nanoimprint lithography. In this paper, we demonstrate the usefulness of the platform primarily by showing an application as a high-sensitivity mass sensor in air. The sensors, which are based on the high frequency resonant response of around 200 MHz, show a mass responsivity of the order of 0.1 Hz/zg per wall at room temperature and in ambient air. Their ability to selectively adsorb airborne target molecules, such as thiols, is also demonstrated. We also show that the same device can function as a varactor for electronic circuits based on its large tunable capacitive range.

  19. Analytical Expressions of the Efficiency of Standard and High Contact Ratio Involute Spur Gears

    Directory of Open Access Journals (Sweden)

    Miguel Pleguezuelos

    2013-01-01

    Full Text Available Simple, traditional methods for computation of the efficiency of spur gears are based on the hypotheses of constant friction coefficient and uniform load sharing along the path of contact. However, none of them is accurate. The friction coefficient is variable along the path of contact, though average values can be often considered for preliminary calculations. Nevertheless, the nonuniform load sharing produced by the changing rigidity of the pair of teeth has significant influence on the friction losses, due to the different relative sliding at any contact point. In previous works, the authors obtained a nonuniform model of load distribution based on the minimum elastic potential criterion, which was applied to compute the efficiency of standard gears. In this work, this model of load sharing is applied to study the efficiency of both standard and high contact ratio involute spur gears (with contact ratio between 1 and 2 and greater than 2, resp.. Approximate expressions for the friction power losses and for the efficiency are presented assuming the friction coefficient to be constant along the path of contact. A study of the influence of some transmission parameters (as the gear ratio, pressure angle, etc. on the efficiency is also presented.

  20. Wet Etched High Aspect Ratio Microstructures on Quartz for MEMS Applications

    Science.gov (United States)

    Liang, Jinxing; Kohsaka, Fusao; Matsuo, Takahiro; Ueda, Toshitsugu

    Z cut α-quartz wafers were etched in saturated ammonium bifluoride solution at 87 degrees C. The side wall profiles were observed using the scanning electron microscopy (SEM) and plotted dependent on the polar direction. This research focused on investigating high aspect ratio trench and through-hole, which were dependent on the polar direction to the crystal axis. Aspect ratio in dependence on polar direction was also plotted and microchannels with aspect ratio > 3 could be achieved at the polar angle between 30° to 60°. The possibility of application for microcapillary was discussed, and the trench at 45° was considered best. Double-sided etching technique was used for manufacturing through-hole structures. Through-hole at 0° was demonstrated effective for fabrication of capacitive MEMS tilt sensor. Through-holes at 15° and 105° were proposed for fabrication of 90°-arranged two axis capactive tilt sensor, taking advantage of the twofold symmetry property around X axis and threefold symmetry property around Z axis.

  1. Nanofabrication of high aspect ratio structures using an evaporated resist containing metal

    Science.gov (United States)

    Con, Celal; Zhang, Jian; Cui, Bo

    2014-05-01

    Organic electron beam resists are typically not resistant to the plasma etching employed to transfer the pattern into the underlying layer. Here, the authors present the incorporation of a metal hard mask material into negative resist polystyrene by co-evaporation of the polystyrene and the metal onto a substrate. With a volume ratio of 1:15 between Cr and polystyrene, this nanocomposite resist showed an etching selectivity to silicon one order higher than pure polystyrene resist. Silicon structures of 100 nm width and 3.5 μm height (aspect ratio 1:35) were obtained using a non-switching deep silicon etching recipe with SF6 and C4F8 gas. Moreover, unlike the common spin coating method, evaporated nanocomposite resist can be coated onto irregular and non-flat surfaces such as optical fibers and AFM cantilevers. As a proof of concept, we fabricated high aspect ratio structures on top of an AFM cantilever. Nanofabrication on non-flat surfaces may find applications in the fields of (AFM) tip enhanced Raman spectroscopy for chemical analysis and lab-on-fiber technology.

  2. Mixing Characteristics of Coaxial Injectors at High Gas to Liquid Momentum Ratios

    Science.gov (United States)

    Strakey, P. A.; Talley, D. G.; Hutt, J. J.

    1999-01-01

    A study of the spray of a swirl coaxial gas-liquid injector operating at high gas to liquid momentum ratios is reported. Mixing and droplet size characteristics of the swirl injector are also compared to a shear coaxial injector, currently being used in the Space Shuttle Main Engine fuel preburner. The injectors were tested at elevated chamber pressures using water as a LOX simulant and nitrogen and helium as gaseous hydrogen simulants. The elevated chamber pressure allowed for matching of several of the preburner injector conditions including; gas to liquid momentum ratio, density ratio and Mach number. Diagnostic techniques used to characterize the spray included; strobe back-light imaging, laser sheet spray imaging, mechanical patternation, and a phase Doppler interferometry. Results thus far indicate that the radial spreading of the swirl coaxial spray is much less than was reported in previous studies of swirl injectors operating at atmospheric back-pressure. The swirl coaxial spray does, however, exhibit a smaller overall droplet size which may be interpreted as an increase in local mixing.

  3. Modulating Cationic Ratios for High-Performance Transparent Solution-Processed Electronics.

    Science.gov (United States)

    John, Rohit Abraham; Nguyen, Anh Chien; Chen, Yuxin; Shukla, Sudhanshu; Chen, Shi; Mathews, Nripan

    2016-01-20

    Amorphous oxide semiconductors such as indium zinc tin oxide (IZTO) are considered favorites to serve as channel materials for thin film transistors (TFTs) because they combine high charge carrier mobility with high optical transmittance, allowing for the development of transparent electronics. Although the influence of relative cationic concentrations in determining the electronic properties have been studied in sputtered and PLD films, the development of printed transparent electronics hinges on such dependencies being explored for solution-processed systems. Here, we study solution-processed indium zinc tin oxide thin film transistors (TFTs) to investigate variation in their electrical properties with change in cationic composition. Charge transport mobility ranging from 0.3 to 20.3 cm(2)/(V s), subthreshold swing ranging from 1.2 to 8.4 V/dec, threshold voltage ranging from -50 to 5 V, and drain current on-off ratio ranging from 3 to 6 orders of magnitude were obtained by examining different compositions of the semiconductor films. Mobility was found to increase with the incorporation of large cations such as In(3+) and Sn(4+) due to the vast s-orbital overlap they can achieve when compared to the intercationic distance. Subthreshold swing decreased with an increase in Zn(2+) concentration due to reduced interfacial state formation between the semiconductor and dielectric. The optimized transistor obtained at a compositional ratio of In/Zn/Sn = 1:1:1, exhibited a high field-effect mobility of 8.62 cm(2)/(V s), subthreshold swing of 1.75 V/dec, and current on-off ratio of 10(6). Such impressive performances reaffirm the promise of amorphous metal oxide semiconductors for printed electronics.

  4. 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.)

  5. Documentation of normal and leukemic myelopoietic progenitor cells with high-resolution phase-contrast time-lapse cinematography.

    Science.gov (United States)

    Boll, I T

    2001-08-01

    The high-resolution phase-contrast, time-lapse cinematography using oil immersion lenses and 16-mm film demonstrates the kinetic cell events as maturation, locomotion, mitosis, and apoptosis of cells cultivated at 37 degrees C for up to 10 days. 0.5 v/v frozen-thawed sera with presumably high cytokine concentrations were added to the plasma or agar clot. Vital progenitor cells from human bone marrow and blood have a large, bright, unstructured nucleus with a large nucleolus and a narrow rim of cytoplasm (nuclear/cytoplasmic volume ratio = 0.7). Their nuclei are 6-14 micrometer in diameter and double their volume within 8 h. Many (70%) move at a mean speed of 2 micrometer/min, and many (30%) multiply with alpha-2alpha mitoses, generating progenitor cell families. Various disturbances during the course of mitosis lead to the formation of polyploid cells, thereby yielding the megakaryocytic cell line. Some of the progenitor cells undergo asymmetric alpha-alphan mitoses: One of the two initially identical daughter cells remains a progenitor cell in the morphological sense, whereas the other daughter cell - depending on the size of its mother cell - matures in the same culture medium to form a granulocytopoietic, monocytopoietic or erythrocytopoietic cell line. - In acute myeloid leukemias (AML), the blasts and their nuclei are slightly larger than the corresponding progenitor cells and move faster (5 micrometer/min). Symmetric alpha-2alpha mitoses permit unlimited multiplication of the leukemic blasts if contact with cytotoxic lymphocytes does not render them apoptotic. This results in more stromal cells than normal. Granulocytopenia, monocytopenia, and anemia occur due to the genetic impairment of signaling control for asymmetric alpha-alphan mitoses, and thrombocytopenia occurs due to the reduction in polyploidization.

  6. Free-jet acoustic investigation of high-radius-ratio coannular plug nozzles

    Science.gov (United States)

    Knott, P. R.; Janardan, B. A.; Majjigi, R. K.; Bhutiani, P. K.; Vogt, P. G.

    1984-01-01

    The experimental and analytical results of a scale model simulated flight acoustic exploratory investigation of high radius ratio coannular plug nozzles with inverted velocity and temperature profiles are summarized. Six coannular plug nozzle configurations and a baseline convergent conical nozzle were tested for simulated flight acoustic evaluation. The nozzles were tested over a range of test conditions that are typical of a Variable Cycle Engine for application to advanced high speed aircraft. It was found that in simulate flight, the high radius ratio coannular plug nozzles maintain their jet noise and shock noise reduction features previously observed in static testing. The presence of nozzle bypass struts will not significantly affect the acousticn noise reduction features of a General Electric type nozzle design. A unique coannular plug nozzle flight acoustic spectral prediction method was identified and found to predict the measured results quite well. Special laser velocimeter and acoustic measurements were performed which have given new insights into the jet and shock noise reduction mechanisms of coannular plug nozzles with regard to identifying further benificial research efforts.

  7. Characterization of the optical parameters of high aspect ratio polymer micro-optical components

    Science.gov (United States)

    Krajewski, Rafal; Van Erps, Jurgen; Wissmann, Markus; Kujawinska, Malgorzata; Parriaux, Olivier; Tonchev, S.; Mohr, Jurgen; Thienpont, Hugo

    2008-04-01

    Over the last decades the significant grow of interest of photonics devices is observed in various fields of applications. Due to the market demands, the current research studies are focused on the technologies providing miniaturized, reliable low-cost micro-optical systems, particularly the ones featuring the fabrication of high aspect ratio structures. A high potential of these technologies comes from the fact that fabrication process is not limited to single optical components, but entire systems integrating sets of elements could be fabricated. This could in turn result in a significant saving on the assembly and packaging costs. We present a brief overview of the most common high aspect ratio fabrication technologies for micro-optical components followed by some characterization studies of these techniques. The sidewall quality and internal homogeneity will be considered as the most crucial parameters, having an impact on the wavefront propagation in the fabricated components. We show the characterization procedure and measurement results for components prototyped with Deep Proton Writing and glass micromachining technology replicated with Hot Embossing and Elastomeric Mould Vacuum Casting technology. We discuss the pros and cons for using these technologies for the production of miniaturized interferometers blocks. In this paper we present the status of our research on the new technology chain and we show the concept of microinterferometers to be fabricated within presented technology chain.

  8. 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.

  9. 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.

  10. High On/Off Conductance Switching Ratio via H-Tautomerization in Quinone.

    Science.gov (United States)

    Tawfik, Sherif Abdulkader; Cui, X Y; Ringer, S P; Stampfl, C

    2015-09-01

    Through first-principles electron transport simulations using the nonequilibrium Green's function formalism together with density functional theory, we show that, upon H-tautomerization, a simple derivative of quinone can act as a molecular switch with high ON/OFF ratio, up to 70 at low bias voltage. This switching behavior is explained by the quantum interference effect, where the positional change of hydrogen atoms causes the energies of the transmission channels to overlap. Our results suggest that this molecule could have potential applications as an effective switching device.

  11. Isotopic Abundances and Ratios in Arsenic Irradiated by High-Energy Neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Parker, W. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hall, J. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2010-06-07

    This document provides derivations of the 73As, 74As and 75As isotopic abundances and ratios in an arsenic sample irradiated by high-energy (14 MeV) neutrons for 0 ≤ t ≤ T, where T is short compared to the natural decay times of the reaction products (t1/2 (73As) ~ 80.3 d, t1/2 (74As) ~ 17.8 d). The document also outlines the historic approach used to analyze arsenic data from experiments.

  12. High voltage conversion ratio, switched C & L cells, step-down DC-DC converter

    DEFF Research Database (Denmark)

    Pelan, Ovidiu; Muntean, Nicolae; Cornea, Octavian;

    2013-01-01

    The paper presents a high voltage conversion ratio DC-DC step-down topology obtained from a classical buck converter associated with an input switched-capacitor cell and an output switched-inductor cell. Analytical descriptions, the voltage and current limits of the main components are synthesized...... in a comparative form, related to the classical buck structure, in order to emphasis the advantages of the proposed converter. Digital simulations and experimental results obtained with a built prototype are compared. From the first evaluation, the proposed converter is expected to be effectively used at input...

  13. Optical bistability effect in plasmonic racetrack resonator with high extinction ratio.

    Science.gov (United States)

    Wang, Xiaolei; Jiang, Houqiang; Chen, Junxue; Wang, Pei; Lu, Yonghua; Ming, Hai

    2011-09-26

    In this paper, optical bistability effect in an ultracompact plasmonic racetrack resonator with nonlinear optical Kerr medium is investigated both analytically and numerically. The properties of optical bistability and pump threshold are studied at 1.55 µm with various detuning parameters by an analytical model. The transmission switch from the upper branch to the lower branch with a pulse is also demonstrated by a finite-difference time-domain method. An extinction ratio of 97.8% and a switching time of 0.38 ps can be achieved with proper detuning parameter. Such a plasmonic resonator design provides a promising realization for highly effective optical modulators and switch.

  14. High sensitivity to mass-ratio variation in deep molecular potentials

    CERN Document Server

    Hanneke, D; Lane, D A

    2016-01-01

    Molecular vibrational transitions are prime candidates for model-independent searches for variation of the proton-to-electron mass ratio. Searches for present-day variation achieve highest sensitivity with deep molecular potentials. We identify several high-sensitivity transitions in the deeply bound ${\\rm O}_2^+$ molecular ion. These transitions are electric-dipole forbidden and thus have narrow linewidths. The most sensitive transitions take advantage of an accidental degeneracy between vibrational states in different electronic potentials. We suggest experimentally feasible routes to a measurement with uncertainty exceeding current limits on present-day variation in $m_p/m_e$.

  15. High sensitivity to variation in the proton-to-electron mass ratio in O2+

    Science.gov (United States)

    Hanneke, D.; Carollo, R. A.; Lane, D. A.

    2016-11-01

    Molecular vibrational transitions are prime candidates for model-independent searches for variation of the proton-to-electron mass ratio. Searches for present-day variation achieve the highest sensitivity with deep molecular potentials. We identify several high-sensitivity transitions in the deeply bound O2+ molecular ion. These transitions are electric-dipole forbidden and have narrow linewidths. The most sensitive transitions take advantage of an accidental degeneracy between vibrational states in different electronic potentials. We suggest experimentally feasible routes to a measurement with uncertainty below current limits on present-day variation in mp/me .

  16. MEMS microphone innovations towards high signal to noise ratios (Conference Presentation) (Plenary Presentation)

    Science.gov (United States)

    Dehé, Alfons

    2017-06-01

    After decades of research and more than ten years of successful production in very high volumes Silicon MEMS microphones are mature and unbeatable in form factor and robustness. Audio applications such as video, noise cancellation and speech recognition are key differentiators in smart phones. Microphones with low self-noise enable those functions. Backplate-free microphones enter the signal to noise ratios above 70dB(A). This talk will describe state of the art MEMS technology of Infineon Technologies. An outlook on future technologies such as the comb sensor microphone will be given.

  17. High speed forging of solid powder discs of large slenderness ratio

    Indian Academy of Sciences (India)

    R K Ranjan; S Kumar

    2004-10-01

    The paper reports an investigation into the forging of a solid powder circular disc with large slenderness ratio (L/D) between two flat dies at high speed. The deformation pattern during the operation is influenced by many factors, which interact with one another in a complex manner. The decisive factors are the interfacial conditions, initial relative density of the preform and the geometry of the preform. An attempt has been made to determine the die pressures developed during such forging, using an upper bound approach. The results so obtained are presented graphically and discussed critically to illustrate the interaction of various process parameters involved.

  18. Relationship between functional hamstring: quadriceps ratios and running economy in highly trained and recreational female runners.

    Science.gov (United States)

    Sundby, Oyvind H; Gorelick, Mark L S

    2014-08-01

    The purpose of this study was to investigate the relationship between running economy (RE), functional hamstring:quadriceps peak torque ratios (f-H:Q), and flexibility among female runners. Seven highly trained (HT) female runners (age: 25.7 ± 4.7 years, VO2peak of 62.0 ± 4.8 ml·kg-1·min-1) and 11 recreational female runners (age of 28.8 ± 5.6 years, VO2peak of 49.2 ± 4.6 ml·kg-1·min-1) were measured for maximal aerobic power (VO2peak), RE, heart rate, respiratory exchange ratio, f-H:Q (Hecc:Qcon and Hcon:Qecc), and sit-and-reach hamstring/trunk flexibility. On 2 separate days, RE was measured on a treadmill at 1% grade at 2 velocities (160.9 and 201.2 m·min-1) for 6 minutes each, and isokinetic knee strength was measured at 3 angular velocities (60, 120, and 180°·s-1) for both concentric and eccentric muscle actions. The unpaired t-tests showed a consistent trend toward higher f-H:Q ratios at all angular velocities among the HT runners. Highly trained runners had significantly higher Hecc:Qcon at 120°·s-1 (p ≤ 0.05) and 180°·s-1 (p ≤ 0.05). Whole group correlations demonstrated a significant correlation between Hcon:Qecc at 180°·s-1 and RE (ml·kg-1·km-1) at 201.2 m·min-1 (R = -0.48, p ≤ 0.05). No significant relationships were found between flexibility, or hamstring and quadriceps peak torque (N·m) and RE (p > 0.05). This cross-sectional analysis suggests that higher f-H:Q torque ratios, and not muscle strength per se, are associated with a lower metabolic cost of running. Therefore, runners should consider implementing hamstring exercises to improve their f-H:Q ratios.

  19. 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.

  20. Chemistry in isolation: High CCH/HCO+ line ratio in the AMIGA galaxy CIG 638

    Science.gov (United States)

    Martín, S.; Verdes-Montenegro, L.; Aladro, R.; Espada, D.; Argudo-Fernández, M.; Kramer, C.; Scott, T. C.

    2014-03-01

    Context. Multi-molecule observations towards an increasing variety of galaxies have been showing that the relative molecular abundances are affected by the type of activity. However, these studies are biased towards bright active galaxies, which are typically in interaction. Aims: We study the molecular composition of one of the most isolated galaxies in the local Universe where the physical and chemical properties of their molecular clouds have been determined by intrinsic mechanisms. Methods: We present 3 mm broad band observations of the galaxy CIG 638, extracted from the AMIGA sample of isolated galaxies. The emission of the J = 1-0 transitions of CCH, HCN, HCO+, and HNC are detected. Integrated intensity ratios between these line are compared with similar observations from the literature towards active galaxies including starburst galaxies (SB), active galactic nuclei, luminous infrared galaxies (LIRG), and GMCs in M 33. Results: A significantly high ratio of CCH with respect to HCN, HCO+, and HNC is found towards CIG 638 when compared with all other galaxies where these species have been detected. This points to either an overabundance of CCH or to a relative lack of dense molecular gas as supported by the low HCN/CO ratio, or both. Conclusions: The data suggest that the CIG 638 is naturally a less perturbed galaxy where a lower fraction of dense molecular gas, as well as a more even distribution could explain the measured ratios. In this scenario the dense gas tracers would be naturally dimmer, while the UV enhanced CCH, would be overproduced in a less shielded medium. Reduced IRAM data (FITS file) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/L6

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Aqueous solution route to high-aspect-ratio zinc oxide nanostructures on indium tin oxide substrates.

    Science.gov (United States)

    Ku, Chen-Hao; Wu, Jih-Jen

    2006-07-06

    High-aspect-ratio ZnO nanowires and nanotubes are formed on indium tin oxide (ITO) substrates using a three-step route at low temperatures. The three steps, including successive ionic layer absorption and reaction (SILAR) deposition of the ZnO seed layer, hydrothermal annealing of the seed layer, and chemical bath deposition (CBD) of the one-dimensional (1D) ZnO nanostructures, are all conducted in aqueous solutions at temperatures below 120 degrees C. Both the hydrothermal annealing of the SILAR seed layer and the low-concentration precursor solution employed in the CBD process are crucial in order to synthesize the uniform and high-aspect-ratio ZnO nanostructures on the ITO substrate. TEM analyses reveal that both the nanowire and the nanotube possess the single-crystal structure and are grown along [001] direction. Room-temperature cathodoluminescence spectrum of the 1D ZnO nanostructures shows a sharp ultraviolet emission at 375 nm and a broad green-band emission.

  8. An enhanced fraction of starbursting galaxies among high Eddington ratio AGNs

    CERN Document Server

    Bernhard, E; Daddi, E; Ciesla, L; Schreiber, C

    2016-01-01

    We investigate the star-forming properties of 1620 X-ray selected AGN host galaxies as a function of their specific X-ray luminosity (i.e., X-ray luminosity per unit host stellar mass) -- a proxy of the Eddington ratio. Our motivation is to determine whether there is any evidence of a suppression of star-formation at high Eddington ratios, which may hint toward "AGN feedback" effects. Star-formation rates (SFRs) are derived from fits to Herschel-measured far-infrared spectral energy distributions, taking into account any contamination from the AGN. Herschel-undetected AGNs are included via stacking analyses to provide average SFRs in bins of redshift and specific X-ray luminosity (spanning $0.01 \\lesssim L_{\\rm X}/M_{\\ast} \\lesssim 100~L_{\\odot} ~M_{\\odot}^{-1}$). After normalising for the effects of mass and redshift arising from the evolving galaxy main sequence, we find that the SFRs of high specific luminosity AGNs are slightly enhanced compared to their lower specific luminosity counterparts. This sugges...

  9. Combined AFM nano-machining and reactive ion etching to fabricate high aspect ratio structures.

    Science.gov (United States)

    Peng, Ping; Shi, Tielin; Liao, Guanglan; Tang, Zirong

    2010-11-01

    In this paper, a new combined method of sub-micron high aspect ratio structure fabrication is developed which can be used for production of nano imprint template. The process includes atomic force microscope (AFM) scratch nano-machining and reactive ion etching (RIE) fabrication. First, 40 nm aluminum film was deposited on the silicon substrate by magnetron sputtering, and then sub-micron grooves were fabricated on the aluminum film by nano scratch using AFM diamond tip. As aluminum film is a good mask for etching silicon, high aspect ratio structures were finally fabricated by RIE process. The fabricated structures were studied by SEM, which shows that the grooves are about 400 nm in width and 5 microm in depth. To obtain sub-micron scale groove structures on the aluminum film, experiments of nanomachining on aluminum films under various machining conditions were conducted. The depths of the grooves fabricated using different scratch loads were also studied by the AFM. The result shows that the material properties of the film/substrate are elastic-plastic following nearly a bilinear law with isotropic strain hardening. Combined AFM nanomachining and RIE process provides a relative lower cost nano fabrication technique than traditional e-beam lithography, and it has a good prospect in nano imprint template fabrication.

  10. Biomimetic Ant-Nest Electrode Structures for High Sulfur Ratio Lithium-Sulfur Batteries.

    Science.gov (United States)

    Ai, Guo; Dai, Yiling; Mao, Wenfeng; Zhao, Hui; Fu, Yanbao; Song, Xiangyun; En, Yunfei; Battaglia, Vincent S; Srinivasan, Venkat; Liu, Gao

    2016-09-14

    The lithium-sulfur (Li-S) rechargeable battery has the benefit of high gravimetric energy density and low cost. Significant research currently focuses on increasing the sulfur loading and sulfur/inactive-materials ratio, to improve life and capacity. Inspired by nature's ant-nest structure, this research results in a novel Li-S electrode that is designed to meet both goals. With only three simple manufacturing-friendly steps, which include slurry ball-milling, doctor-blade-based laminate casting, and the use of the sacrificial method with water to dissolve away table salt, the ant-nest design has been successfully recreated in an Li-S electrode. The efficient capabilities of the ant-nest structure are adopted to facilitate fast ion transportation, sustain polysulfide dissolution, and assist efficient precipitation. High cycling stability in the Li-S batteries, for practical applications, has been achieved with up to 3 mg·cm(-2) sulfur loading. Li-S electrodes with up to a 85% sulfur ratio have also been achieved for the efficient design of this novel ant-nest structure.

  11. Planarization of High Aspect Ratio P-I-N Diode Pillar Arrays for Blanket Electrical Contacts

    Energy Technology Data Exchange (ETDEWEB)

    Voss, L F; Shao, Q; Reinhardt, C E; Graff, R T; Conway, A M; Nikolic, R J; Deo, N; Cheung, C L

    2009-03-05

    Two planarization techniques for high aspect ratio three dimensional pillar structured P-I-N diodes have been developed in order to enable a continuous coating of metal on the top of the structures. The first technique allows for coating of structures with topography through the use of a planarizing photoresist followed by RIE etch back to expose the tops of the pillar structure. The second technique also utilizes photoresist, but instead allows for planarization of a structure in which the pillars are filled and coated with a conformal coating by matching the etch rate of the photoresist to the underlying layers. These techniques enable deposition using either sputtering or electron beam evaporation of metal films to allow for electrical contact to the tops of the underlying pillar structure. These processes have potential applications for many devices comprised of 3-D high aspect ratio structures. Two separate processes have been developed in order to ensure a uniform surface for deposition of an electrode on the {sup 10}Boron filled P-I-N pillar structured diodes. Each uses S1518 photoresist in order to achieve a relatively uniform surface despite the non-uniformity of the underlying detector. Both processes allow for metallization of the final structure and provide good electrical continuity over a 3D pillar structure.

  12. Diffusion of dilute gas in arrays of randomly distributed, vertically aligned, high-aspect-ratio cylinders

    Science.gov (United States)

    Guerra, Carlos

    2017-01-01

    In this work we modelled the diffusive transport of a dilute gas along arrays of randomly distributed, vertically aligned nanocylinders (nanotubes or nanowires) as opposed to gas diffusion in long pores, which is described by the well-known Knudsen theory. Analytical expressions for (i) the gas diffusion coefficient inside such arrays, (ii) the time between collisions of molecules with the nanocylinder walls (mean time of flight), (iii) the surface impingement rate, and (iv) the Knudsen number of such a system were rigidly derived based on a random-walk model of a molecule that undergoes memoryless, diffusive reflections from nanocylinder walls assuming the molecular regime of gas transport. It can be specifically shown that the gas diffusion coefficient inside such arrays is inversely proportional to the areal density of cylinders and their mean diameter. An example calculation of a diffusion coefficient is delivered for a system of titanium isopropoxide molecules diffusing between vertically aligned carbon nanotubes. Our findings are important for the correct modelling and optimisation of gas-based deposition techniques, such as atomic layer deposition or chemical vapour deposition, frequently used for surface functionalisation of high-aspect-ratio nanocylinder arrays in solar cells and energy storage applications. Furthermore, gas sensing devices with high-aspect-ratio nanocylinder arrays and the growth of vertically aligned carbon nanotubes need the fundamental understanding and precise modelling of gas transport to optimise such processes. PMID:28144565

  13. High fat diet prevents over-crowding induced decrease of sex ratio in mice.

    Directory of Open Access Journals (Sweden)

    Madhukar Shivajirao Dama

    Full Text Available Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to their offspring's future reproductive success. In the present study, we tested the effect of housing mice under crowded condition on the sex ratio and whether the fat content of the diet has any influence on the outcome of pregnancies. Three-week-old mice were placed on the control diet (NFD for 3 weeks. Thereafter the mice were allotted randomly to two groups of 7 cages each with 4, 6, 8, 10, 12, 14, and 16 mice in every cage to create increasing crowding gradient and fed either NFD or high fat diet (HFD. After 4 weeks, dams were bred and outcomes of pregnancy were analyzed. The average dam body weight (DBW at conception, litter size (LS and SR were significantly higher in HFD fed dams. Further, male biased litters declined with increasing crowding in NFD group but not in HFD. The LS and SR in NFD declined significantly with increasing crowding, whereas only LS was reduced in HFD group. We conclude that female mice housed under overcrowding conditions shift offspring SR in favor of daughters in consistent with the TW hypothesis and high fat diet reduces this influence of overcrowding.

  14. The Capabilities of Electrodischarge Microdrilling of High Aspect Ratio Holes in Ceramic Materials

    Directory of Open Access Journals (Sweden)

    Skoczypiec Sebastian

    2015-09-01

    Full Text Available In the first part of the article the review of ceramic materials drilling possibilities was presented. Among the described methods special attention is paid to electrodischarge drilling. This process have especially been predicted for machining difficult-to-cut electrically conductive materials. The second part consist of the results analysis of electrodischarge microdrilling of siliconized silicon carbide. The experiment involves the impact of current amplitude, discharge voltage and pulse time on the hole depth, side gap, linear tool wear and mean drilling speed. The results shows that electrodischarge drilling is a good alternative when machining inhomogeneous ceramic materials and gives possibility to drill high aspect ratio holes with relatively high efficiency (the drilling speed >2 mm/min.

  15. 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...

  16. An enhanced fraction of starbursting galaxies among high Eddington ratio AGNs

    Science.gov (United States)

    Bernhard, E.; Mullaney, J. R.; Daddi, E.; Ciesla, L.; Schreiber, C.

    2016-07-01

    We investigate the star-forming properties of 1620 X-ray selected active galactic nuclei (AGN) host galaxies as a function of their specific X-ray luminosity (i.e. X-ray luminosity per unit host stellar mass) - a proxy of the Eddington ratio. Our motivation is to determine whether there is any evidence of a suppression of star formation at high Eddington ratios, which may hint towards `AGN feedback' effects. Star formation rates (SFRs) are derived from fits to Herschel-measured far-infrared spectral energy distributions, taking into account any contamination from the AGN. Herschel-undetected AGNs are included via stacking analyses to provide average SFRs in bins of redshift and specific X-ray luminosity (spanning 0.01 lesssim L_X/M_{ast } lesssim 100 L_{{⊙}} M_{{⊙}}^{-1}). After normalizing for the effects of mass and redshift arising from the evolving galaxy main sequence, we find that the SFRs of high specific luminosity AGNs are slightly enhanced compared to their lower specific luminosity counterparts. This suggests that the SFR distribution of AGN hosts changes with specific X-ray luminosity, a result reinforced by our finding of a significantly higher fraction of starbursting hosts among high specific luminosity AGNs compared to that of the general star-forming galaxy population (i.e. 8-10 per cent versus 3 per cent). Contrary to our original motivation, our findings suggest that high specific luminosity AGNs are more likely to reside in galaxies with enhanced levels of star formation.

  17. Analytical description of the injection ratio of self-biased bipolar transistors under the very high injection conditions of ESD events

    Science.gov (United States)

    Gendron, A.; Renaud, P.; Bafleur, M.; Nolhier, N.

    2008-05-01

    This paper proposes a 1D-analytical description of the injection ratio of a self-biased bipolar transistor under very high current injection conditions. Starting from an expression of the current gain based on the stored charge into the emitter and base regions, we derive a new analytical expression of the current injection ratio. This analytical description demonstrates the presence of an asymptotic limit for the injection ratio at very high current densities, as the ratio of electron/hole mobilities in the case of an NPN transistor and to the ratio of hole/electron saturation velocities for a PNP. Moreover, for the first time, a base narrowing effect is demonstrated and explained in the case of a self-biased PNP, in contrast with the base widening effect (Kirk effect [Kirk CT, A theory of transistor cutoff frequency (fT) falloff at high current densities, IRE Trans Electr Dev 1961: p. 164-73]) reported for lower current density. These results are validated by numerical simulation and show a good agreement with experimental characterizations of transistors especially designed to operate under extreme condition such as electrostatic discharge (ESD) events.

  18. Etching high aspect ratio structures in silicon using sulfur hexafluoride/oxygen plasma

    Science.gov (United States)

    Belen, Rodolfo Jun

    Plasma etching of high aspect ratio structures in Si is an important step in manufacturing capacitors for memory devices and integrated components of microelectromechanical systems. In these applications, the goal is to etch deep features anisotropically with high etch rates and selectivities to the mask while maintaining good uniformity and reproducibility. This study investigates the etching of deep sub-half-micron diameter holes in Si using SF6/O 2 plasma. Etching experiments and plasma diagnostics are combined with modeling to gain a fundamental understanding of the etching and passivation kinetics and mechanism necessary in developing and scaling-up processes. Etching experiments are conducted in an inductively coupled plasma reactor with a planar coil. The substrate electrode is biased with a separate rf power supply to achieve independent control of the ion flux and energy. The effects of pressure, rf-bias and SF6-to-O2 ratio in the feed gas on the etch rate, selectivity and feature profile shape are studied using Si wafers patterned with 0.35 mum-diameter holes in a SiO2 mask. Visualization of profiles using scanning electron microscopy is complemented by plasma diagnostics such as mass spectrometry and actinometry. Simultaneous with experiments, reactor-scale and feature-scale models are developed to quantify the etching and passivation kinetics and identify the important kinetic parameters that affect feature profile evolution. Information from plasma diagnostics and previously published data are used to reduce the degrees of freedom in the model. Experiments are designed to directly measure kinetic parameters such as the chemical etch rate constant and the incidence angle dependence of the etching yield. Experimentally inaccessible parameters such as the sticking coefficients, etching yield and ion scattering parameters are determined through feature profile simulation. The key internal plasma parameters that affect profile evolution are the F-to-O and F

  19. Frontiers of QC Laser spectroscopy for high precision isotope ratio analysis of greenhouse gases

    Science.gov (United States)

    Emmenegger, Lukas; Mohn, Joachim; Harris, Eliza; Eyer, Simon; Ibraim, Erkan; Tuzson, Béla

    2016-04-01

    An important milestone for laser spectroscopy was achieved when isotope ratios of greenhouse gases were reported at precision levels that allow addressing research questions in environmental sciences. Real-time data with high temporal resolution at moderate cost and instrument size make the optical approach highly attractive, complementary to the well-established isotope-ratio mass-spectrometry (IRMS) method. Especially appealing, in comparison to IRMS, is the inherent specificity to structural isomers having the same molecular mass. Direct absorption in the MIR in single or dual QCL configuration has proven highly reliable for the sta-ble isotopes of CO2, N2O and CH4. The longest time series of real-time measurements is currently available for δ13C and δ18O in CO2 at the high-alpine station Jung-fraujoch. At this well-equipped site, QCL based direct absorption spectroscopy (QCLAS) measurements are ongoing since 2008 1,2. Applications of QCLAS for N2O and CH4 stable isotopes are considerably more challenging because of the lower atmospheric mixing ratios, especially for the less abundant species, such as N218O and CH3D. For high precision (mental applications illustrating the highly valuable information that isotope ratios of atmospheric trace gases can carry. For example, the intramolecular distribution of 15N in N2O gives important information on the geochemical cycle of N2O4-6, while the analysis of δ13C and δ D in CH4 may be applied to disentangle microbial, fossil and landfill sources 7. 1 Sturm, P., Tuzson, B., Henne, S. & Emmenegger, L. Tracking isotopic signatures of CO2 at the high altitude site Jungfraujoch with laser spectroscopy: Analytical improvements and representative re-sults. Atmospheric Measurement Techniques 6, 1659-1671 (2013). 2 Tuzson, B. et al. Continuous isotopic composition measurements of tropospheric CO2 at Jungfraujoch (3580 m a.s.l.), Switzerland: real-time observation of regional pollution events. Atmospheric Chemistry and Physics

  20. High tunneling magnetoresistance ratio in perpendicular magnetic tunnel junctions using Fe-based Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu-Pu, E-mail: Vicky-sg1015@hotmail.com [Department of Electrical and Computer Engineering, National University of Singapore (Singapore); Data Storage Institute, Agency for Science, Technology and Research - A*STAR (Singapore); Lim, Sze-Ter; Han, Gu-Chang, E-mail: HAN-Guchang@dsi.a-star.edu.sg [Data Storage Institute, Agency for Science, Technology and Research - A*STAR (Singapore); Teo, Kie-Leong, E-mail: eleteokl@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore (Singapore)

    2015-12-21

    Heulser alloys Fe{sub 2}Cr{sub 1−x}Co{sub x}Si (FCCS) with different Co compositions x have been predicted to have high spin polarization. High perpendicular magnetic anisotropy (PMA) has been observed in ultra-thin FCCS films with magnetic anisotropy energy density up to 2.3 × 10{sup 6 }erg/cm{sup 3}. The perpendicular magnetic tunnel junctions (p-MTJs) using FCCS films with different Co compositions x as the bottom electrode have been fabricated and the post-annealing effects have been investigated in details. An attractive tunneling magnetoresistance ratio as high as 51.3% is achieved for p-MTJs using Fe{sub 2}CrSi (FCS) as the bottom electrode. The thermal stability Δ can be as high as 70 for 40 nm dimension devices using FCS, which is high enough to endure a retention time of over 10 years. Therefore, Heusler alloy FCS is a promising PMA candidate for p-MTJ application.