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Sample records for achieve high contrast

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

    ERIC Educational Resources Information Center

    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)

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

    ERIC Educational Resources Information Center

    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…

  3. Achieving High Contrast for Exoplanet Imaging with a Kalman Filter and Stroke Minimization

    NASA Astrophysics Data System (ADS)

    Eldorado Riggs, A. J.; Groff, T. D.; Kasdin, N. J.; Carlotti, A.; Vanderbei, R. J.

    2014-01-01

    High contrast imaging requires focal plane wavefront control and estimation to correct aberrations in an optical system; non-common path errors prevent the use of conventional estimation with a separate wavefront sensor. The High Contrast Imaging Laboratory (HCIL) at Princeton has led the development of several techniques for focal plane wavefront control and estimation. In recent years, we developed a Kalman filter for optimal wavefront estimation. Our Kalman filter algorithm is an improvement upon DM Diversity, which requires at least two images pairs each iteration and does not utilize any prior knowledge of the system. The Kalman filter is a recursive estimator, meaning that it uses the data from prior estimates along with as few as one new image pairs per iteration to update the electric field estimate. Stroke minimization has proven to be a feasible controller for achieving high contrast. While similar to a variation of Electric Field Conjugation (EFC), stroke minimization achieves the same contrast with less stroke on the DMs. We recently utilized these algorithms to achieve high contrast for the first time in our experiment at the High Contrast Imaging Testbed (HCIT) at the Jet Propulsion Laboratory (JPL). Our HCIT experiment was also the first demonstration of symmetric dark hole correction in the image plane using two DMs--this is a major milestone for future space missions. Our ongoing work includes upgrading our optimal estimator to include an estimate of the incoherent light in the system, which allows for simultaneous estimation of the light from a planet along with starlight. The two-DM experiment at the HCIT utilized a shaped pupil coronagraph. Those tests utilized ripple style, free-standing masks etched out of silicon, but our current work is in designing 2-D optimized reflective shaped pupils. In particular, we have created several designs for the AFTA telescope, whose pupil presents major hurdles because of its atypical pupil obstructions. Our

  4. High-Achieving and Average Students' Reading Growth: Contrasting School and Summer Trajectories

    ERIC Educational Resources Information Center

    Rambo-Hernandez, Karen E.; McCoach, D. Betsy

    2015-01-01

    Much is unknown about how initially high-achieving students grow academically, especially given the measurement issues inherent in assessing growth for the highest performing students. This study compared initially high-achieving and average students' growth in reading (in a cohort of third-grade students from 2,000 schools) over 3 years.…

  5. High Contrast CRT.

    DTIC Science & Technology

    1980-02-01

    form brown sulfides or sulfates. By con- trast, No. 1720 glass does not acquire a brown coloration . How- ever, preliminary tests with 1723 glass show...TR-77-2639-F NL -mmo mhhmhul IIII,. BwII ---- i 11111--- IIIIIN III i 8’ II.I25 .11111 I .6 MCROCOPY RESOLUTION TEST CHART NATIONAL BUREAU Of...High Contrast Displays Two- Color CRT Laminar Flow Electron Gun Thin Film Phosphor Color Penetration Tube 2% AS~iTACT (ConIlm. a" Pove.. 0fdo if

  6. High-contrast imaging testbed

    SciTech Connect

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

    2008-01-23

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

  7. Is High Temporal Resolution Achievable for Paediatric Cardiac Acquisitions during Several Heart Beats? Illustration with Cardiac Phase Contrast Cine-MRI

    PubMed Central

    Bonnemains, Laurent; Odille, Freddy; Meyer, Christophe; Hossu, Gabriella; Felblinger, Jacques; Vuissoz, Pierre-André

    2015-01-01

    Background During paediatric cardiac Cine-MRI, data acquired during cycles of different lengths must be combined. Most of the time, Feinstein’s model is used to project multiple cardiac cycles of variable lengths into a mean cycle. Objective To assess the effect of Feinstein projection on temporal resolution of Cine-MRI. Methods 1/The temporal errors during Feinstein’s projection were computed in 306 cardiac cycles fully characterized by tissue Doppler imaging with 6-phase analysis (from a population of 7 children and young adults). 2/The effects of these temporal errors on tissue velocities were assessed by simulating typical tissue phase mapping acquisitions and reconstructions. 3/Myocardial velocities curves, extracted from high-resolution phase-contrast cine images, were compared for the 6 volunteers with lowest and highest heart rate variability, within a population of 36 young adults. Results 1/The mean of temporal misalignments was 30 ms over the cardiac cycle but reached 60 ms during early diastole. 2/During phase contrast MRI simulation, early diastole velocity peaks were diminished by 6.1 cm/s leading to virtual disappearance of isovolumic relaxation peaks. 3/The smoothing and erasing of isovolumic relaxation peaks was confirmed on tissue phase mapping velocity curves, between subjects with low and high heart rate variability (p = 0.05). Conclusions Feinstein cardiac model creates temporal misalignments that impair high temporal resolution phase contrast cine imaging when beat-to-beat heart rate is changing. PMID:26599755

  8. Determination of contrast media administration to achieve a targeted contrast enhancement in CT

    NASA Astrophysics Data System (ADS)

    Sahbaee, Pooyan; Li, Yuan; Segars, Paul; Marin, Daniele; Nelson, Rendon; Samei, Ehsan

    2015-03-01

    Contrast enhancement is a key component of CT imaging and offer opportunities for optimization. The design and optimization of new techniques however requires orchestration with the scan parameters and further a methodology to relate contrast enhancement and injection function. In this study, we used such a methodology to develop a method, analytical inverse method, to predict the required injection function to achieve a desired contrast enhancement in a given organ by incorporation of a physiologically based compartmental model. The method was evaluated across 32 different target contrast enhancement functions for aorta, kidney, stomach, small intestine, and liver. The results exhibited that the analytical inverse method offers accurate performance with error in the range of 10% deviation between the predicted and desired organ enhancement curves. However, this method is incapable of predicting the injection function based on the liver enhancement. The findings of this study can be useful in optimizing contrast medium injection function as well as the scan timing to provide more consistency in the way that the contrast enhanced CT examinations are performed. To our knowledge, this work is one of the first attempts to predict the contrast material injection function for a desired organ enhancement curve.

  9. High-performance nanostructured MR contrast probes

    PubMed Central

    Hu, Fengqin; Joshi, Hrushikesh M.; Dravid, Vinayak P.; Meade, Thomas J.

    2011-01-01

    Magnetic resonance imaging (MRI) has become a powerful technique in biological molecular imaging and clinical diagnosis. With the rapid progress in nanoscale science and technology, nanostructure-based MR contrast agents are undergoing rapid development. This is in part due to the tuneable magnetic and cellular uptake properties, large surface area for conjugation and favourable biodistribution. In this review, we describe our recent progress in the development of high-performance nanostructured MR contrast agents. Specifically, we report on Gd-enriched nanostructured probes that exhibit T1 MR contrast and superparamagnetic Fe3O4 and CoFe2O4 nanostructures that display T2 MR contrast enhancement. The effects of nanostructure size, shape, assembly and surface modification on relaxivity are described. The potential of these contrast agents for in vitro and in vivo MR imaging with respect to colloidal stability under physiological conditions, biocompatibility, and surface functionality are also evaluated. PMID:20694208

  10. NASA High Contrast Imaging for Exoplanets

    NASA Technical Reports Server (NTRS)

    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.

  11. Contrast enhancement of high-energy radiotherapy films.

    PubMed

    Reinstein, L E; Orton, C G

    1979-11-01

    An order-of-magnitude improvment in the contrast of high-energy localization and verification films has been achieved through the application of a simple, inexpensive, contrast enhancement technique. The method involves making reversal contact "prints" of the original film onto ordinary X-ray fi-m with equipment commonly available in any radiotherapy department. This results in "gamma multiplication". The theory as well as several applications of this effect are presented.

  12. The Potential of High-Contrast Coronagraphy

    NASA Technical Reports Server (NTRS)

    Serabyn, E.

    2008-01-01

    The direct detection of faint companions near much brighter stars requires the development of very high-contrast, small field-of-view detection techniques, and the past decade has seen remarkable conceptual and instrumental progress in this area. New coronagraphic techniques are being developed and deployed, as are extreme adaptive optics (ExAO) systems that will enable the advantageous exploitation of these new techniques. This paper provides a short overview of promising high contrast coronagraphic techniques, as well as recent examples of ExAO coronagraphy and transit measurements obtained with the ExAO-level "well-corrected subaperture" at Palomar.

  13. Embedded high-contrast distributed grating structures

    DOEpatents

    Zubrzycki, Walter J.; Vawter, Gregory A.; Allerman, Andrew A.

    2002-01-01

    A new class of fabrication methods for embedded distributed grating structures is claimed, together with optical devices which include such structures. These new methods are the only known approach to making defect-free high-dielectric contrast grating structures, which are smaller and more efficient than are conventional grating structures.

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

    NASA Technical Reports Server (NTRS)

    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.

  15. Proton shock acceleration using a high contrast high intensity laser

    NASA Astrophysics Data System (ADS)

    Gauthier, Maxence; Roedel, Christian; Kim, Jongjin; Aurand, Bastian; Curry, Chandra; Goede, Sebastian; Propp, Adrienne; Goyon, Clement; Pak, Art; Kerr, Shaun; Ramakrishna, Bhuvanesh; Ruby, John; William, Jackson; Glenzer, Siegfried

    2015-11-01

    Laser-driven proton acceleration is a field of intense research due to the interesting characteristics of this novel particle source including high brightness, high maximum energy, high laminarity, and short duration. Although the ion beam characteristics are promising for many future applications, such as in the medical field or hybrid accelerators, the ion beam generated using TNSA, the acceleration mechanism commonly achieved, still need to be significantly improved. Several new alternative mechanisms have been proposed such as collisionless shock acceleration (CSA) in order to produce a mono-energetic ion beam favorable for those applications. We report the first results of an experiment performed with the TITAN laser system (JLF, LLNL) dedicated to the study of CSA using a high intensity (5x1019W/cm2) high contrast ps laser pulse focused on 55 μm thick CH and CD targets. We show that the proton spectrum generated during the interaction exhibits high-energy mono-energetic features along the laser axis, characteristic of a shock mechanism.

  16. The TRENDS High-Contrast Imaging Program

    NASA Astrophysics Data System (ADS)

    Crepp, Justin

    2014-08-01

    We have established a multi-disciplinary program that combines precise Doppler measurements with high-contrast imaging. Using long-term RV accelerations (or 'trends'), we take a much-needed short-cut for identifying promising high-contrast imaging targets. The goal of this project is to directly detect and characterize the companions responsible for accelerating their host stars. By working at the interface of two powerful and complementary planet detection techniques, we are able to construct 3d-orbits, calculate dynamical masses, and explicitly calibrate theoretical atmospheric models for substellar objects in a regime where they currently break-down (low temperatures). Using a sample of non-detections, the TRENDS program also provides the ability to robustly determine the occurrence rate of giant planets from 0-20 AU through statistical inference.

  17. Phase contrast in high resolution electron microscopy

    DOEpatents

    Rose, H.H.

    1975-09-23

    This patent relates to a device for developing a phase contrast signal for a scanning transmission electron microscope. The lens system of the microscope is operated in a condition of defocus so that predictable alternate concentric regions of high and low electron density exist in the cone of illumination. Two phase detectors are placed beneath the object inside the cone of illumination, with the first detector having the form of a zone plate, each of its rings covering alternate regions of either higher or lower electron density. The second detector is so configured that it covers the regions of electron density not covered by the first detector. Each detector measures the number of electrons incident thereon and the signal developed by the first detector is subtracted from the signal developed by the record detector to provide a phase contrast signal. (auth)

  18. HIGH-CONTRAST IMAGING VIA MODAL CONVERGENCE OF DEFORMABLE MIRROR

    SciTech Connect

    Wang Feiling

    2012-06-01

    For extremely high contrast imaging, such as direct observation of faint stellar companions, an adaptive optics system is required to produce low-halo and low-speckle regions in the focal plane. A method for deformable mirror control is proposed to achieve this goal. The method relies on a modal convergence of the deformable mirror driven by a focal-plane metric. The modal sets are derived from the Walsh functions. The Walsh-function modes serve two purposes: the expansion of the actuator displacements and the expansion of the phase functions. Taking advantage of the unique properties of the modal functions, a universal control algorithm is devised for the realization of high-contrast focal planes with and without the help of conventional coronagraphy. Numerical modeling is conducted to simulate complete imaging systems under various scenarios. It is shown that the proposed method reliably produces high-contrast focal planes using either a segmented or a membrane mirror. In the presence of random aberration the method is shown to be able to maintain high-contrast focal planes. Requiring neither retrieval of electric fields nor detailed knowledge of the deformable mirrors, this technique may allow high-contrast imaging in real time.

  19. The Constraints of Poverty on High Achievement

    ERIC Educational Resources Information Center

    Burney, Virginia H.; Beilke, Jayne R.

    2008-01-01

    Research studies on school success often focus on the impact of discrete elements such as race, culture, ethnicity, gender, language, or school location on high achievement. The condition of poverty, however, may be the most important of all student differences in relation to high achievement; although not all schools have racial diversity, nearly…

  20. Self Regulated Learning of High Achievers

    ERIC Educational Resources Information Center

    Rathod, Ami

    2010-01-01

    The study was conducted on high achievers of Senior Secondary school. Main objectives were to identify the self regulated learners among the high achievers, to find out dominant components and characteristics operative in self regulated learners and to compare self regulated learning of learners with respect to their subject (science and non…

  1. High-contrast imaging with METIS

    NASA Astrophysics Data System (ADS)

    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.

  2. High-contrast and fast electrochromic switching enabled by plasmonics

    PubMed Central

    Xu, Ting; Walter, Erich C.; Agrawal, Amit; Bohn, Christopher; Velmurugan, Jeyavel; Zhu, Wenqi; Lezec, Henri J.; Talin, A. Alec

    2016-01-01

    With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. However, slow switching speeds in devices realized to date, as well as the complexity of having to combine several distinct polymers to achieve a full-colour gamut, have limited electrochromic materials to niche applications. Here we achieve fast, high-contrast electrochromic switching by significantly enhancing the interaction of light—propagating as deep-subwavelength-confined surface plasmon polaritons through arrays of metallic nanoslits, with an electrochromic polymer—present as an ultra-thin coating on the slit sidewalls. The switchable configuration retains the short temporal charge-diffusion characteristics of thin electrochromic films, while maintaining the high optical contrast associated with thicker electrochromic coatings. We further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-colour response with high contrast and fast switching speeds, while relying on just one electrochromic polymer. PMID:26814453

  3. High-contrast and fast electrochromic switching enabled by plasmonics

    SciTech Connect

    Xu, Ting; Walter, Erich C.; Agrawal, Amit; Bohn, Christopher; Velmurugan, Jeyavel; Zhu, Wenqi; Lezec, Henri J.; Talin, A. Alec

    2016-01-27

    With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. However, slow switching speeds in devices realized to date, as well as the complexity of having to combine several distinct polymers to achieve a full-colour gamut, have limited electrochromic materials to niche applications. Here we achieve fast, high-contrast electrochromic switching by significantly enhancing the interaction of light—propagating as deep-subwavelength-confined surface plasmon polaritons through arrays of metallic nanoslits, with an electrochromic polymer—present as an ultra-thin coating on the slit sidewalls. The switchable configuration retains the short temporal charge-diffusion characteristics of thin electrochromic films, while maintaining the high optical contrast associated with thicker electrochromic coatings. In conclusion, we further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-colour response with high contrast and fast switching speeds, while relying on just one electrochromic polymer.

  4. High-contrast and fast electrochromic switching enabled by plasmonics.

    PubMed

    Xu, Ting; Walter, Erich C; Agrawal, Amit; Bohn, Christopher; Velmurugan, Jeyavel; Zhu, Wenqi; Lezec, Henri J; Talin, A Alec

    2016-01-27

    With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. However, slow switching speeds in devices realized to date, as well as the complexity of having to combine several distinct polymers to achieve a full-colour gamut, have limited electrochromic materials to niche applications. Here we achieve fast, high-contrast electrochromic switching by significantly enhancing the interaction of light--propagating as deep-subwavelength-confined surface plasmon polaritons through arrays of metallic nanoslits, with an electrochromic polymer--present as an ultra-thin coating on the slit sidewalls. The switchable configuration retains the short temporal charge-diffusion characteristics of thin electrochromic films, while maintaining the high optical contrast associated with thicker electrochromic coatings. We further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-colour response with high contrast and fast switching speeds, while relying on just one electrochromic polymer.

  5. High-contrast and fast electrochromic switching enabled by plasmonics

    NASA Astrophysics Data System (ADS)

    Talin, Albert; Xu, Ting; Walter, Erich; Agrawal, Amit; Bohn, Christopher; Velmurugan, Jeyavel; Zhu, Wenqi; Lezec, Henri

    With vibrant colors and simple, room-temperature processing methods, electrochromic polymers have long attracted attention as active materials for flexible, low-power consuming devices such as smart windows and displays. However, despite their many advantages, slow switching speed and complexity of combining several separate polymers to achieve full-color gamut has limited electrochromic materials to niche applications. Here we exploit the enhanced light-matter interaction associated with the deep-subwavelength mode confinement of surface plasmon polaritons propagating in metallic nanoslit arrays coated with ultra-thin electrochromic polymers to build a novel configuration for achieving high-contrast and fast electrochromic switching. The switchable configuration retains the short temporal charge-diffusion characteristics of thin electrochromic films while maintaining the high optical-contrast associated with thicker electrochromic coatings. We further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-color response with high-contrast and fast switching-speeds while relying on just one electrochromic polymer.

  6. High-contrast and fast electrochromic switching enabled by plasmonics

    NASA Astrophysics Data System (ADS)

    Xu, Ting; Walter, Erich C.; Agrawal, Amit; Bohn, Christopher; Velmurugan, Jeyavel; Zhu, Wenqi; Lezec, Henri J.; Talin, A. Alec

    2016-01-01

    With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. However, slow switching speeds in devices realized to date, as well as the complexity of having to combine several distinct polymers to achieve a full-colour gamut, have limited electrochromic materials to niche applications. Here we achieve fast, high-contrast electrochromic switching by significantly enhancing the interaction of light--propagating as deep-subwavelength-confined surface plasmon polaritons through arrays of metallic nanoslits, with an electrochromic polymer--present as an ultra-thin coating on the slit sidewalls. The switchable configuration retains the short temporal charge-diffusion characteristics of thin electrochromic films, while maintaining the high optical contrast associated with thicker electrochromic coatings. We further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-colour response with high contrast and fast switching speeds, while relying on just one electrochromic polymer.

  7. High-contrast and fast electrochromic switching enabled by plasmonics

    DOE PAGES

    Xu, Ting; Walter, Erich C.; Agrawal, Amit; ...

    2016-01-27

    With vibrant colours and simple, room-temperature processing methods, electrochromic polymers have attracted attention as active materials for flexible, low-power-consuming devices. However, slow switching speeds in devices realized to date, as well as the complexity of having to combine several distinct polymers to achieve a full-colour gamut, have limited electrochromic materials to niche applications. Here we achieve fast, high-contrast electrochromic switching by significantly enhancing the interaction of light—propagating as deep-subwavelength-confined surface plasmon polaritons through arrays of metallic nanoslits, with an electrochromic polymer—present as an ultra-thin coating on the slit sidewalls. The switchable configuration retains the short temporal charge-diffusion characteristics of thinmore » electrochromic films, while maintaining the high optical contrast associated with thicker electrochromic coatings. In conclusion, we further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-colour response with high contrast and fast switching speeds, while relying on just one electrochromic polymer.« less

  8. High contrast laser marking of alumina

    NASA Astrophysics Data System (ADS)

    Penide, J.; Quintero, F.; Riveiro, A.; Fernández, A.; del Val, J.; Comesaña, R.; Lusquiños, F.; Pou, J.

    2015-05-01

    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.

  9. Systemic Reform and Minority Student High Achievement.

    ERIC Educational Resources Information Center

    Treisman, Philip Uri; Surles, Stephanie A.

    The under-representation of African American and Hispanic American students among high achievers on standardized tests, honors graduates of most colleges, and practitioners of mathematics and science professions is well-documented. This paper explores the extent to which the current educational reform movement is achieving the goal of…

  10. Versatile method for achieving 1% speckle contrast in large-venue laser projection displays using a stationary multimode optical fiber.

    PubMed

    Manni, Jeffrey G; Goodman, Joseph W

    2012-05-07

    We propose a method based on quantitative theoretical analysis for achieving speckle contrast of 1% or less in images created by a full-frame laser projection display system. The method employs a stationary multimode optical fiber to achieve the effect of using a rapidly moving diffuser, but without moving the fiber or any other system component. When a suitably large projector lens is used, low-speckle illumination light delivered through the fiber acts in conjunction with wavelength diversity at the projection screen to achieve speckle contrast of 1% in viewed images. We describe in detail how the proposed method might be used with most types of high-power visible lasers being considered for large-venue displays. When used with visible laser diodes, the method may also be suitable for use in laser-based television.

  11. Clouds of high contrast on Uranus.

    PubMed

    Karkoschka, E

    1998-04-24

    Near-infrared images of Uranus taken with the Hubble Space Telescope in July and October 1997 revealed discrete clouds with contrasts exceeding 10 times the highest contrast observed before with other techniques. At visible wavelengths, these 10 clouds had lower contrasts than clouds seen by Voyager 2 in 1986. Uranus' rotational rates for southern latitudes were identical in 1986 and 1997. Clouds in northern latitudes rotate slightly more slowly than clouds in opposite southern latitudes.

  12. Student Perceptions of High-Achieving Classmates

    ERIC Educational Resources Information Center

    Händel, Marion; Vialle, Wilma; Ziegler, Albert

    2013-01-01

    The reported study investigated students' perceptions of their high-performing classmates in terms of intelligence, social skills, and conscientiousness in different school subjects. The school subjects for study were examined with regard to cognitive, physical, and gender-specific issues. The results show that high academic achievements in…

  13. High Stakes Testing and Student Achievement.

    ERIC Educational Resources Information Center

    Ediger, Marlow

    The effects of high stakes testing may be critical in the lives of public school students and may have many consequences for schools and teachers. There are no easy answers in measuring student achievement and in holding teachers accountable for learner progress. High stakes testing also involves responsibilities on the part of the principal who…

  14. High Achievers: 23rd Annual Survey. Attitudes and Opinions from the Nation's High Achieving Teens.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Northbrook, IL.

    This report presents data from an annual survey of high school student leaders and high achievers. It is noted that of the nearly 700,000 high achievers featured in this edition, 5,000 students were sent the survey and 2,092 questionnaires were completed. Subjects were high school juniors and seniors selected for recognition by their principals or…

  15. Orion: a high contrast user facility

    NASA Astrophysics Data System (ADS)

    Hillier, D. I.; Danson, C. N.; Duffield, S. J.; Egan, D. A.; Elsmere, S. P.; Girling, M. T.; Harvey, E. J.; Hopps, N. W.; Norman, M. J.; Parker, S. J. F.; Treadwell, P. T.; Winter, D. N.; Bett, T. H.

    2016-03-01

    The Orion facility consists of two synchronized laser systems: two CPA (Chirped Pulse Amplification) beamlines each deliver 500J to target in a 0.5ps pulse (1PW) at 1054nm; and ten long pulse beamlines each deliver 500J in 0.1-5ns temporally shaped pulse at 351nm. One of the CPA beamlines has the option to be frequency doubled at sub-aperture to produce 100J laser pulses with a nanosecond contrast of ∼ 1014. Further work is under way to enhance the contrast of both CPA beamlines in the first harmonic.

  16. Achieving High Performance Perovskite Solar Cells

    NASA Astrophysics Data System (ADS)

    Yang, Yang

    2015-03-01

    Recently, metal halide perovskite based solar cell with the characteristics of rather low raw materials cost, great potential for simple process and scalable production, and extreme high power conversion efficiency (PCE), have been highlighted as one of the most competitive technologies for next generation thin film photovoltaic (PV). In UCLA, we have realized an efficient pathway to achieve high performance pervoskite solar cells, where the findings are beneficial to this unique materials/devices system. Our recent progress lies in perovskite film formation, defect passivation, transport materials design, interface engineering with respect to high performance solar cell, as well as the exploration of its applications beyond photovoltaics. These achievements include: 1) development of vapor assisted solution process (VASP) and moisture assisted solution process, which produces perovskite film with improved conformity, high crystallinity, reduced recombination rate, and the resulting high performance; 2) examination of the defects property of perovskite materials, and demonstration of a self-induced passivation approach to reduce carrier recombination; 3) interface engineering based on design of the carrier transport materials and the electrodes, in combination with high quality perovskite film, which delivers 15 ~ 20% PCEs; 4) a novel integration of bulk heterojunction to perovskite solar cell to achieve better light harvest; 5) fabrication of inverted solar cell device with high efficiency and flexibility and 6) exploration the application of perovskite materials to photodetector. Further development in film, device architecture, and interfaces will lead to continuous improved perovskite solar cells and other organic-inorganic hybrid optoelectronics.

  17. Reliability achievement in high technology space systems

    NASA Technical Reports Server (NTRS)

    Lindstrom, D. L.

    1981-01-01

    The production of failure-free hardware is discussed. The elements required to achieve such hardware are: technical expertise to design, analyze, and fully understand the design; use of high reliability parts and materials control in the manufacturing process; and testing to understand the system and weed out defects. The durability of the Hughes family of satellites is highlighted.

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

    NASA Astrophysics Data System (ADS)

    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.

  19. High contrast reflective liquid crystal display using a thermochromic reflector

    NASA Astrophysics Data System (ADS)

    Heo, Kyong Chan; Yi, Jonghoon; Kwon, Jin Hyuk; Seog Gwag, Jin

    2015-02-01

    This paper presents a reflective liquid crystal display (LCD) with a high contrast ratio (CR) combined with mono-type thermochromic materials to solve the low CR of reflective type LCDs. Here, reflective, wide-band, electrically controlled birefringence mode was used as the optical liquid crystal (LC) mode, and a thermochromic material was used as the reflector for the white state and an absorber for the dark state. The combination of LCD and thermochromic material can have a synergistic effect in achieving a better display. By controlling the reflectance of the thermochromic reflector using Joule heating, the proposed reflective LC cell exhibited a high CR of approximately 70:1. The figure was extremely high compared to the approximately 10:1 of a typical reflective LC cell with an optically wide band design. The proposed LC cell configuration is expected to find many outdoor applications which can admit slow response speed.

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

    SciTech Connect

    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.

  1. Early predictors of high school mathematics achievement.

    PubMed

    Siegler, Robert S; Duncan, Greg J; Davis-Kean, Pamela E; Duckworth, Kathryn; Claessens, Amy; Engel, Mimi; Susperreguy, Maria Ines; Chen, Meichu

    2012-07-01

    Identifying the types of mathematics content knowledge that are most predictive of students' long-term learning is essential for improving both theories of mathematical development and mathematics education. To identify these types of knowledge, we examined long-term predictors of high school students' knowledge of algebra and overall mathematics achievement. Analyses of large, nationally representative, longitudinal data sets from the United States and the United Kingdom revealed that elementary school students' knowledge of fractions and of division uniquely predicts those students' knowledge of algebra and overall mathematics achievement in high school, 5 or 6 years later, even after statistically controlling for other types of mathematical knowledge, general intellectual ability, working memory, and family income and education. Implications of these findings for understanding and improving mathematics learning are discussed.

  2. Attitudes and Opinions from the Nation's High Achieving Teens. 18th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Educational Communications, Inc., Lake Forest, IL.

    This document contains factsheets and news releases which cite findings from a national survey of 1,985 high achieving high school students. Factsheets describe the Who's Who Among American High School Students recognition and service program for high school students and explain the Who's Who survey. A summary report of this eighteenth annual…

  3. Highly efficient polarization control using subwavelength high contrast transmitarrays

    NASA Astrophysics Data System (ADS)

    Arbabi, Amir; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

    2015-02-01

    We report efficient wave plates with different retardations and orientations of fast axes realized using transmitarrays composed of a periodic arrangement of amorphous silicon elliptical cylinders on glass. We show that novel polarization devices which locally rotate the polarization by different angles while preserving the wavefront can be demonstrated using such a high contrast transmitarray. We present design, fabrication and experimental characterization results for near infrared transmissive wave retarders with efficiencies in excess of 90%, and discuss the potential applications of atwill local polarization control enabled by this technology.

  4. High Resolution X-Ray Phase Contrast Imaging With Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2006-06-01

    microfocus x - ray source. Rev. Sci. Instr. 68, 2774 (1997). 8. Krol, A. et al. Laser-based microfocused x - ray source for mammography: Feasibility study...W81XWH-04-1-0481 TITLE: High Resolution X - ray Phase Contrast Imaging With Acoustic Tissue-Selective Contrast Enhancement PRINCIPAL...REPORT TYPE Annual 3. DATES COVERED (From - To) 1 Jun 2005 – 31 May 2006 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER High Resolution X - ray

  5. 22nd Annual Survey of High Achievers: Attitudes and Opinions from the Nation's High Achieving Teens.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Northbrook, IL.

    This study surveyed high school students (N=1,879) who were student leaders or high achievers in the spring of 1991 for the purpose of determining their attitudes. Students were members of the junior or senior high school class during the 1990-91 academic year and were selected for recognition by their principals or guidance counselors, other…

  6. High efficiency upconversion nanophosphors for high-contrast bioimaging.

    PubMed

    Alkahtani, Masfer H; Alghannam, Fahad S; Sanchez, Carlos; Gomes, Carmen L; Liang, Hong; Hemmer, Philip R

    2016-12-02

    Upconversion nanoparticles (UCNPs) are of interest because they allow suppression of tissue autofluorescence and are therefore visible deep inside biological tissue. Compared to upconversion dyes, UCNPs have a lower pump intensity threshold, better photostability, and less toxicity. Recently, YVO4: Er(+3), Yb(+3) nanoparticles were shown to exhibit strong up-conversion luminescence with a relatively low 10 kW cm(-2) excitation intensity even in water, which makes them excellent bio-imaging candidates. Herein, we investigate their use as internal probes in insects by injecting YVO4 : Er(+3), Yb(+3) nanoparticles into fire ants as a biological model, and obtain 2D optical images with 980 nm illumination. High-contrast images with high signal-to-noise ratio are observed by detecting the up-conversion fluorescence as the excitation laser is scanned.

  7. High efficiency upconversion nanophosphors for high-contrast bioimaging

    NASA Astrophysics Data System (ADS)

    Alkahtani, Masfer H.; Alghannam, Fahad S.; Sanchez, Carlos; Gomes, Carmen L.; Liang, Hong; Hemmer, Philip R.

    2016-12-01

    Upconversion nanoparticles (UCNPs) are of interest because they allow suppression of tissue autofluorescence and are therefore visible deep inside biological tissue. Compared to upconversion dyes, UCNPs have a lower pump intensity threshold, better photostability, and less toxicity. Recently, YVO4: Er+3, Yb+3 nanoparticles were shown to exhibit strong up-conversion luminescence with a relatively low 10 kW cm-2 excitation intensity even in water, which makes them excellent bio-imaging candidates. Herein, we investigate their use as internal probes in insects by injecting YVO4 : Er+3, Yb+3 nanoparticles into fire ants as a biological model, and obtain 2D optical images with 980 nm illumination. High-contrast images with high signal-to-noise ratio are observed by detecting the up-conversion fluorescence as the excitation laser is scanned.

  8. High contrast holograms using nanotube forest

    NASA Astrophysics Data System (ADS)

    Montelongo, Yunuen; Chen, Bingan; Butt, Haider; Robertson, John; Wilkinson, Timothy D.

    2013-09-01

    Nanotube forest behaves as highly absorbent material when they are randomly placed in sub-wavelength scales. Furthermore, it is possible to create diffractive structures when these bulks are patterned in a substrate. Here, we introduce an alternative to fabricate intensity holograms by patterning fringes of nanotube forest on a substrate. The result is an efficient intensity hologram that is not restricted to sub-wavelength patterning. Both the theoretical and experimental analysis was performed with good agreement. The produced holograms show a uniform behaviour throughout the visible spectra.

  9. Attitudes and Opinions from the Nation's High Achieving Teens: 26th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    A national survey of 3,351 high achieving high school students (junior and senior level) was conducted. All students had A or B averages. Topics covered include lifestyles, political beliefs, violence and entertainment, education, cheating, school violence, sexual violence and date rape, peer pressure, popularity, suicide, drugs and alcohol,…

  10. Attitudes and Opinions from the Nation's High Achieving Teens. 24th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This survey represents information compiled by the largest national survey of adolescent leaders and high achievers. Of the 5,000 students selected demographically from "Who's Who Among American High School Students," 1,957 responded. All students surveyed had "A" or "B" averages, and 98% planned on attending college. Questions were asked about…

  11. High energy mode locked fiber oscillators for high contrast, high energy petawatt laser seed sources

    SciTech Connect

    Dawson, J W; Messerly, M J; An, J; Kim, D; Barty, C J

    2006-06-15

    In a high-energy petawatt laser beam line the ASE pulse contrast is directly related to the total laser gain. Thus a more energetic input pulse will result in increased pulse contrast at the target. We have developed a mode-locked fiber laser with high quality pulses and energies exceeding 25nJ. We believe this 25nJ result is scalable to higher energies. This oscillator has no intra-cavity dispersion compensation, which yields an extremely simple, and elegant laser configuration. We will discuss the design of this laser, our most recent results and characterization of all the key parameters relevant to it use as a seed laser. Our oscillator is a ring cavity mode-locked fiber laser [1]. These lasers operate in a self-similar pulse propagation regime characterized by a spectrum that is almost square. This mode was found theoretically [2] to occur only in the positive dispersion regime. Further increasing positive dispersion should lead to increasing pulse energy [2]. We established that the positive dispersion required for high-energy operation was approximately that of 2m of fiber. To this end, we constructed a laser cavity similar to [1], but with no gratings and only 2m of fiber, which we cladding pumped in order to ensure sufficient pump power was available to achieve mode-locked operation. A schematic of the laser is shown in figure 1 below. This laser produced low noise 25nJ pulses with a broad self similar spectrum (figure 2) and pulses that could be de-chirped to <100fs (figure 3). Pulse contrast is important in peta-watt laser systems. A major contributor to pulse contrast is amplified spontaneous emission (ASE), which is proportional to the gain in the laser chain. As the oscillator strength is increased, the required gain to reach 1PW pulses is decreased, reducing ASE and improving pulse contrast. We believe these lasers can be scaled in a stable fashion to pulse energies as high as 100nJ and have in fact seen 60nJ briefly in our lab, which is work still

  12. Contrast medium usage reduction in abdominal computed tomography by using high-iodinated concentration contrast medium

    NASA Astrophysics Data System (ADS)

    Suwannasri, A.; Kaewlai, R.; Asavaphatiboon, S.

    2016-03-01

    This study was to determine if administration of a low volume high-concentration iodinated contrast medium can preserve image quality in comparison with regular-concentration intravenous contrast medium in patient undergoing contrast-enhancement abdominal computed tomography (CT). Eighty-four patients were randomly divided into 3 groups of similar iodine delivery rate; A: 1.2 cc/kg of iomeprol-400, B: 1.0 cc/kg of iomeprol-400 and C: 1.5 cc/kg of ioversol-350. Contrast enhancement of the liver parenchyma, pancreas and aorta was quantitatively measured in Hounsfield units and qualitative assessed by a radiologist. T-test was used to evaluate contrast enhancement, and Chi-square test was used to evaluate qualitative image assessment, at significance level of 0.05 with 95% confidence intervals. There were no statistically significant differences in contrast enhancement of liver parenchyma and pancreas between group A and group C in both quantitative and qualitative analyses. Group C showed superior vascular enhancement to group A and B on quantitative analysis.

  13. Combining hard and soft magnetism into a single core-shell nanoparticle to achieve both hyperthermia and image contrast

    PubMed Central

    Yang, Qiuhong; Gong, Maogang; Cai, Shuang; Zhang, Ti; Douglas, Justin T; Chikan, Viktor; Davies, Neal M; Lee, Phil; Choi, In-Young; Ren, Shenqiang; Forrest, M Laird

    2015-01-01

    Background A biocompatible core/shell structured magnetic nanoparticles (MNPs) was developed to mediate simultaneous cancer therapy and imaging. Methods & results A 22-nm MNP was first synthesized via magnetically coupling hard (FePt) and soft (Fe3O4) materials to produce high relative energy transfer. Colloidal stability of the FePt@Fe3O4 MNPs was achieved through surface modification with silane-polyethylene glycol (PEG). Intravenous administration of PEG-MNPs into tumor-bearing mice resulted in a sustained particle accumulation in the tumor region, and the tumor burden of treated mice was a third that of the mice in control groups 2 weeks after a local hyperthermia treatment. In vivo magnetic resonance imaging exhibited enhanced T2 contrast in the tumor region. Conclusion This work has demonstrated the feasibility of cancer theranostics with PEG-MNPs. PMID:26606855

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

    NASA Technical Reports Server (NTRS)

    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.

  15. High Involvement Mothers of High Achieving Children: Potential Theoretical Explanations

    ERIC Educational Resources Information Center

    Hunsaker, Scott L.

    2013-01-01

    In American society, parents who have high aspirations for the achievements of their children are often viewed by others in a negative light. Various pejoratives such as "pushy parent," "helicopter parent," "stage mother," and "soccer mom" are used in the common vernacular to describe these parents. Multiple…

  16. Does High School Homework Increase Academic Achievement?

    ERIC Educational Resources Information Center

    Kalenkoski, Charlene Marie; Pabilonia, Sabrina Wulff

    2017-01-01

    Although previous research has shown that homework improves students' academic achievement, the majority of these studies use data on students' homework time from retrospective questionnaires, which may be less accurate than time-diary data. We use data from the combined Child Development Supplement (CDS) and the Transition to Adulthood Survey…

  17. Factors Implicated in High Mathematics Achievement

    ERIC Educational Resources Information Center

    Forgasz, Helen J.; Hill, Janelle C.

    2013-01-01

    The most recent Program for International Student Assessment (PISA) (2009) mathematical literacy results provide evidence that in Western English-speaking countries, including Australia, the gender gap in achievement appears to be widening in favour of males. In the study reported in this article, the aim was to explore the effects of gender,…

  18. High Ability Readers and the Achievement Gap

    ERIC Educational Resources Information Center

    Hunsaker, Scott L.; Parke, Cynthia J.; Bramble, Joan G.

    2004-01-01

    To close the achievement gap, the "No Child Left Behind" law calls for all students to make appropriate yearly progress. This presumably means that progress is being made by capable readers at the same time progress is being made by struggling readers. However, there appear to be unintended effects of "No Child Left Behind"…

  19. High-contrast imaging and high-resolution spectroscopy observation of exoplanets

    NASA Astrophysics Data System (ADS)

    Wang, Ji; Mawet, Dimitri; Hu, Renyu; Benneke, Björn

    2016-08-01

    Detection and characterization of exoplanets faces challenges of smaller angular separation and high contrast between exoplanets and their host stars. High contrast imaging (HCI) instruments equipped with coronagraphs are built to meet these challenges, providing a way of spatially suppressing and separating stellar flux from that of a planet. Another way of separating stellar flux can be achieved by high-resolution spectroscopy (HRS), exploiting the fact that spectral features are different between a star and a planet. Observing exoplanets with HCI+HRS will achieve a higher contrast than the spatial or the spectroscopic method alone, improving the sensitivity to planet detection and enabling the study of the physical and chemical processes. Here, we simulate the performance of a HCI+HRS instrument (i.e., the upgrade Keck NIRSPEC and the fiber injection unit) to study its potential in detecting and characterizing currently known directly imaged planets. The simulation considers the spectral information content of an exoplanet, telescope and instrument specifications and realistic noise sources. The result of the simulation helps to set system requirement and informs designs at system-level. We also perform a trade study for a HCI+HRS instrument for a space mission to study an Earth-like planet orbiting a Sun-like star at 10 pc.

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

    PubMed

    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.

  1. High Resolution X-Ray Phase Contrast Imaging with Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2005-06-01

    microfocus x - ray source. Rev. Sci. Instr. 68, 2774 (1997). 8. Krol, A. et al. Laser-based microfocused x - ray ...high spatial coherence, such as synchrotrons 46, microfocus x - ray tubes 7, or laser plasma x - ray sources 8,9are employed is the phase contrast component...imaging apparatus to determine the deflection of the bead as a function of acoustic pressure. The x - rays , generated by a microfocus x - ray tube

  2. High-Achieving Students in the Era of NCLB

    ERIC Educational Resources Information Center

    Loveless, Tom; Parkas, Steve; Duffett, Ann

    2008-01-01

    This report contains two separate studies examining the status of high-achieving students in the No Child Left Behind (NCLB) era. Part I, An Analysis of NAEP Data, authored by Brookings Institution scholar Tom Loveless, examines achievement trends for high-achieving students (defined, like low-achieving students, by their performance on the…

  3. Closed Loop, DM Diversity-based, Wavefront Correction Algorithm for High Contrast Imaging Systems

    NASA Technical Reports Server (NTRS)

    Give'on, Amir; Belikov, Ruslan; Shaklan, Stuart; Kasdin, Jeremy

    2007-01-01

    High contrast imaging from space relies on coronagraphs to limit diffraction and a wavefront control systems to compensate for imperfections in both the telescope optics and the coronagraph. The extreme contrast required (up to 10(exp -10) for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. This paper presents a general closed loop correction algorithm for high contrast imaging coronagraphs by minimizing the energy in a predefined region in the image where terrestrial planets could be found. The estimation part of the algorithm reconstructs the complex field in the image plane using phase diversity caused by the deformable mirror. This method has been shown to achieve faster and better correction than classical speckle nulling.

  4. High-contrast gratings as a new platform for integrated optoelectronics

    NASA Astrophysics Data System (ADS)

    Chang-Hasnain, Connie J.

    2011-01-01

    A new concept of dielectric subwavelength grating has emerged. This grating leverages a high contrast in refractive indices for the grating medium and its surroundings. We will discuss how high-index-contrast grating (HCG) can manipulate light to achieve various extraordinary properties. We will discuss various designs to yield broadband, high-reflectivity mirrors for light incident in surface-normal direction and at a glancing angle, ultra high-Q resonators with surface-normal output, planar high focusing power reflectors and lenses, and ultralow loss hollow-core waveguides. The HCG will be a new, promising platform for integrated optics with applications for lasers, filters, waveguides, sensors and detectors.

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

    SciTech Connect

    Snigireva, I.

    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.

  6. Improving Student Achievement: A Study of High-Poverty Schools with Higher Student Achievement Outcomes

    ERIC Educational Resources Information Center

    Butz, Stephen D.

    2012-01-01

    This research examined the education system at high-poverty schools that had significantly higher student achievement levels as compared to similar schools with lower student achievement levels. A multischool qualitative case study was conducted of the educational systems where there was a significant difference in the scores achieved on the…

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    Herein we report on our contrast assessment and the development, sensing and control of the Vacuum Nuller Testbed to realize a Visible Nulling Coronagraphy (VNC) for exoplanet detection and characterization. Tbe VNC is one of the few approaches that works with filled, segmented and sparse or diluted-aperture telescope systems. It thus spans a range of potential future NASA telescopes and could be flown as a separate instrument on such a future mission. NASA/Goddard Space Flight Center has an established effort to develop VNC technologies, and an incremental sequence of testbeds to advance this approach and its critical technologies. We discuss the development of the vacuum Visible Nulling Coronagraph testbed (VNT). The VNT is an ultra-stable vibration isolated testbed that operates under closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence of three visible-light nulling milestones with sequentially higher contrasts of 10(exp 8), 10(exp 9) and ideally 10(exp 10) at an inner working angle of 2*lambda/D. The VNT is based on a modified Mach-Zehnder nulling interferometer, with a "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters. We discuss the laboratory results, optical configuration, critical technologies and the null sensing and control approach.

  8. Achieving strategic surety for high consequence software

    SciTech Connect

    Pollock, G.M.

    1996-09-01

    A strategic surety roadmap for high consequence software systems under the High Integrity Software (HIS) Program at Sandia National Laboratories guides research in identifying methodologies to improve software surety. Selected research tracks within this roadmap are identified and described detailing current technology and outlining advancements to be pursued over the coming decade to reach HIS goals. The tracks discussed herein focus on Correctness by Design, and System Immunology{trademark}. Specific projects are discussed with greater detail given on projects involving Correct Specification via Visualization, Synthesis, & Analysis; Visualization of Abstract Objects; and Correct Implementation of Components.

  9. A Kindergarten Number-Sense Intervention with Contrasting Practice Conditions for Low-Achieving Children

    ERIC Educational Resources Information Center

    Dyson, Nancy; Jordan, Nancy C.; Beliakoff, Amber; Hassinger-Das, Brenna

    2015-01-01

    The efficacy of a research-based number-sense intervention for low-achieving kindergartners was examined. Children (N = 126) were randomly assigned to 1 of 3 conditions: a number-sense intervention followed by a number-fact practice session, an identical number-sense intervention followed by a number-list practice session, or a business-as-usual…

  10. Achieving High-Temperature Ferromagnetic Topological Insulator

    NASA Astrophysics Data System (ADS)

    Katmis, Ferhat

    Topological insulators (TIs) are insulating materials that display conducting surface states protected by time-reversal symmetry, wherein electron spins are locked to their momentum. This unique property opens new opportunities for creating next-generation electronic and spintronic devices, including TI-based quantum computation. Introducing ferromagnetic order into a TI system without compromising its distinctive quantum coherent features could lead to a realization of several predicted novel physical phenomena. In particular, achieving robust long-range magnetic order at the TI surface at specific locations without introducing spin scattering centers could open up new possibilities for devices. Here, we demonstrate topologically enhanced interface magnetism by coupling a ferromagnetic insulator (FMI) to a TI (Bi2Se3); this interfacial ferromagnetism persists up to room temperature, even though the FMI (EuS) is known to order ferromagnetically only at low temperatures (<17 K). The induced magnetism at the interface resulting from the large spin-orbit interaction and spin-momentum locking feature of the TI surface is found to greatly enhance the magnetic ordering (Curie) temperature of the TI/FMI bilayer system. Due to the short range nature of the ferromagnetic exchange interaction, the time-reversal symmetry is broken only near the surface of a TI, while leaving its bulk states unaffected. The topological magneto-electric response originating in such an engineered TI could allow for an efficient manipulation of the magnetization dynamics by an electric field, providing an energy efficient topological control mechanism for future spin-based technologies. Work supported by MIT MRSEC through the MRSEC Program of NSF under award number DMR-0819762, NSF Grant DMR-1207469, the ONR Grant N00014-13-1-0301, and the STC Center for Integrated Quantum Materials under NSF grant DMR-1231319.

  11. Norview High School: Leadership Fosters Achievment

    ERIC Educational Resources Information Center

    Principal Leadership, 2013

    2013-01-01

    Often little unsaid things demonstrate what is truly important in a school. When teachers have common planning time and all of the department chairs share a single space as they do at Norview High School in Norfolk, VA, the unmistakable message is that instructional collaboration and leadership are expected and valued. Norview, an urban,…

  12. High Contrast Programmable Field Masks for JWST NIRSpec

    NASA Technical Reports Server (NTRS)

    Kutyrev, Alexander S.

    2008-01-01

    Microshutter arrays are one of the novel technologies developed for the James Webb Space Telescope (JWST). It will allow Near Infrared Spectrometer (NIRSpec) to acquire spectra of hundreds of objects simultaneously therefore increasing its efficiency tremendously. We have developed these programmable arrays that are based on Micro-Electro Mechanical Structures (MEMS) technology. The arrays are 2D addressable masks that can operate in cryogenic environment of JWST. Since the primary JWST science requires acquisition of spectra of extremely faint objects, it is important to provide very high contrast of the open to closed shutters. This high contrast is necessary to eliminate any possible contamination and confusion in the acquired spectra by unwanted objects. We have developed and built a test system for the microshutter array functional and optical characterization. This system is capable of measuring the contrast of the microshutter array both in visible and infrared light of the NIRSpec wavelength range while the arrays are in their working cryogenic environment. We have measured contrast ratio of several microshutter arrays and demonstrated that they satisfy and in many cases far exceed the NIRSpec contrast requirement value of 2000.

  13. T1 and susceptibility contrast at high fields

    NASA Astrophysics Data System (ADS)

    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

  14. High contrast broadband seeder for multi-PW laser system

    NASA Astrophysics Data System (ADS)

    Chalus, O.; Pellegrina, A.; Ricaud, S.; Casagrande, O.; Derycke, C.; Radier, C.; Soujaeff, A.; Matras, G.; Rey, G.; Boudjemaa, L.; Simon-Boisson, C.; Laux, S.; Lureau, F.

    2016-03-01

    A hybrid Ti:Sa CPA/BBO OPCPA system with a XPW filter in between the two has been developed to produce a broadband high contrast seeder of 10 mJ for the two 10 PetaWatt beamlines of ELI NP infrastructure.

  15. A Kindergarten Number-Sense Intervention With Contrasting Practice Conditions for Low-Achieving Children

    PubMed Central

    Dyson, Nancy; Jordan, Nancy C.; Beliakoff, Amber; Hassinger-Das, Brenna

    2015-01-01

    The efficacy of a research-based number-sense intervention for low-achieving kinder-gartners was examined. Children (N = 126) were randomly assigned to 1 of 3 conditions: a number-sense intervention followed by a number-fact practice session, an identical number-sense intervention followed by a number-list practice session, or a business-as-usual control group. The interventions were delivered in a small-group setting over 24 half-hour lessons. Both intervention groups performed better than controls on measures of number sense, arithmetic fluency, and general mathematics calculation achievement at immediate posttest. However, the number-fact practice condition gave children an additional advantage over the number-list practice condition on the outcomes at delayed posttest 8 weeks later. The number-fact practice condition was especially effective for producing gains in English learners. PMID:26388651

  16. A Kindergarten Number-Sense Intervention With Contrasting Practice Conditions for Low-Achieving Children.

    PubMed

    Dyson, Nancy; Jordan, Nancy C; Beliakoff, Amber; Hassinger-Das, Brenna

    2015-05-01

    The efficacy of a research-based number-sense intervention for low-achieving kinder-gartners was examined. Children (N = 126) were randomly assigned to 1 of 3 conditions: a number-sense intervention followed by a number-fact practice session, an identical number-sense intervention followed by a number-list practice session, or a business-as-usual control group. The interventions were delivered in a small-group setting over 24 half-hour lessons. Both intervention groups performed better than controls on measures of number sense, arithmetic fluency, and general mathematics calculation achievement at immediate posttest. However, the number-fact practice condition gave children an additional advantage over the number-list practice condition on the outcomes at delayed posttest 8 weeks later. The number-fact practice condition was especially effective for producing gains in English learners.

  17. Self-Concept and Achievement Motivation of High School Students

    ERIC Educational Resources Information Center

    Lawrence, A. S. Arul; Vimala, A.

    2013-01-01

    The present study "Self-concept and Achievement Motivation of High School Students" was investigated to find the relationship between Self-concept and Achievement Motivation of High School Students. Data for the study were collected using Self-concept Questionnaire developed by Raj Kumar Saraswath (1984) and Achievement Motive Test (ACMT)…

  18. Gun requirements to achieve high field spheromaks

    SciTech Connect

    Fowler, T K

    1999-03-04

    It is shown that a gun similar to that in the SSPX could demonstrate the high fields required for Pulsed Spheromak reactors merely by prolonging the pulse. Important considerations are choosing the voltage to exceed ohmic losses; designing the gun to avoid wasteful short-circuiting of current within the gun; and the injection efficiency factor, f, determined by the ''sag'' in the profile of {lambda} = {mu}{sub o}j/B. Typically f = 0.75 in experiments, giving an overall efficiency > 50 % if short-circuiting is avoided. Theoretical transport models agree qualitatively with the need for a finite gradient in h to pump in helicity by current-driven tearing modes and suggest that pressure-driven resistive modes would not compete with current-driven modes during a buildup to ohmic ignition.

  19. The V-SHARK high contrast imager at LBT

    NASA Astrophysics Data System (ADS)

    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.

  20. Potential of high-Z contrast agents in clinical contrast-enhanced computed tomography

    SciTech Connect

    Nowak, Tristan; Hupfer, Martin; Brauweiler, Robert; Eisa, Fabian; Kalender, Willi A.

    2011-12-15

    Purpose: Currently, only iodine- and barium-based contrast media (CM) are used in clinical contrast-enhanced computed tomography (CE-CT). High-Z metals would produce a higher contrast at equal mass density for the x-ray spectra used in clinical CT. Using such materials might allow for significant dose reductions in CE-CT. The purpose of this study was to quantify the potential for dose reduction when using CM based on heavy metals. Methods: The contrast-to-noise ratio weighted by dose (CNRD) was determined as a function of scan protocol by means of measurements and simulations on a clinical CT scanner. For simulations, water cylinders with diameters 160, 320, 480, and 640 mm were used to cover a broad range of patient sizes. Measurements were conducted with 160 and 320 mm water-equivalent plastic cylinders. A central bore of 13 mm diameter was present in all phantoms. The tube voltage was varied from 80 to 140 kV for measurements and from 60 to 180 kV for simulations. Additional tin filtration of thicknesses 0.4, 0.8, and 1.2 mm was applied in the simulation to evaluate a range of spectral hardness. The bore was filled with a mixture of water and 10 mg/ml of pure iodine, holmium, gadolinium, ytterbium, osmium, tungsten, gold, and bismuth for the simulations and with aqueous solutions of ytterbium, tungsten, gold, and bismuth salts as well as Iopromid containing 10 mg/ml of the pure materials for the measurements. CNRDs were compared to iodine at phantom size-dependent reference voltages for all high-Z materials and the resulting dose reduction was calculated for equal contrast-to-noise ratio. Results: Dose reduction potentials strongly depended on phantom size, spectral hardness, and tube voltage. Depending on the added filtration, a dose reduction of 19%-60% could be reached at 80 kV with gadolinium for the 160 mm phantom, 52%-69% at 100 kV with holmium for the 320 mm phantom, 62%-78% with 120 kV for hafnium and the 480 mm phantom and 74%-86% with 140 kV for gold

  1. Gd-HOPO Based High Relaxivity MRI Contrast Agents

    SciTech Connect

    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.

  2. Optimal Phase Masks for High Contrast Imaging Applications

    NASA Astrophysics Data System (ADS)

    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.

  3. Scientific Temper among Academically High and Low Achieving Adolescent Girls

    ERIC Educational Resources Information Center

    Kour, Sunmeet

    2015-01-01

    The present study was undertaken to compare the scientific temper of high and low achieving adolescent girl students. Random sampling technique was used to draw the sample from various high schools of District Srinagar. The sample for the present study consisted of 120 school going adolescent girls (60 high and 60 low achievers). Data was…

  4. Laboratory Demonstrations of High-contrast Imaging for Space Coronagraphy

    NASA Technical Reports Server (NTRS)

    Trauger, John; Giveon, Amir; Gordon, Brian; Kern, Brian; Krist, John; Kuhnert, Andreas; Moody, Dwight; Traub, Wes; Wilson, Dan

    2008-01-01

    This slide presentation reviews the use of the High Contrast Imaging Testbed (HCIT) in the design and improvement of space coronagraphs. The objectives of the work are to: (1) Advance the technology readiness of space coronagraph hardware, techniques, algorithms, and predictive models; (2) Provide proof-of-concept demonstrations of coronagraph techniques; and (3) Support collaborations across the exoplanet community in pursuit of the optimal space coronagraph architecture.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

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

    NASA Astrophysics Data System (ADS)

    Dou, Jiangpei; Ren, Deqing

    2016-11-01

    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 extremely high contrast. We present a phase quantization study of a spatial light modulator (SLM) 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. The simulation result has constrained the specification for SLM phase accuracy in the above two optical configurations, which gives us a phase accuracy of 0.4/1000 and 1/1000 waves to achieve a contrast of 10-10. Finally, we have demonstrated that an SLM with more actuators can deliver a competitive contrast performance on the order of 10-10 in comparison to that by using a deformable mirror.

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

    NASA Astrophysics Data System (ADS)

    Girard, Julien H. V.; O'Neal, Jared; Mawet, Dimitri; Kasper, Markus; Zins, Gérard; Neichel, Benoît; Kolb, Johann; Christiaens, Valentin; Tourneboeuf, Martin

    2012-07-01

    NACO is the famous and versatile diffraction limited NIR imager and spectrograph at the VLT with which ESO celebrated 10 years of Adaptive Optics. Since two years a substantial effort has been put in 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 more 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 the ones working at the diffraction limit and making use of angular differential imaging (i.e. SPHERE, VISIR, and possibly ERIS).

  9. High Contrast Imaging with the JWST NIRCAM Coronagraph

    NASA Technical Reports Server (NTRS)

    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.

  10. The "Renaissance Child": High Achievement and Gender in Late Modernity

    ERIC Educational Resources Information Center

    Skelton, Christine; Francis, Becky

    2012-01-01

    This paper draws on the concept of the "Renaissance Child" to illustrate the ways in which gender influences the opportunities and possibilities of high-achieving pupils. Using data from a study of 12-13-year high-achieving boys and girls based in schools in England, the paper considers the ways in which a group of popular boys was able…

  11. Active tunable high contrast meta-structure Si waveguide

    NASA Astrophysics Data System (ADS)

    Jiang, Lingjun; Anderson, Stephen; Taleb, Hussein; Huang, Zhaoran R.; Zhou, Weimin

    2016-03-01

    In this work, we have designed a novel Si based 1-dimensional high contrast meta-structure waveguide that has slow light effect as well as phase tunability using p-n junction. The goal is to use such waveguide to design active optical devices such as high frequency modulators and tunable filters for analog RF-photonics or data communication applications. The Si ridge waveguide has a pair of high contrast grating wings adhered to the waveguide core in the center. Grating bars at two sides of the waveguide are doped P and N-type respectively, while a p-n junction region is formed in the middle of the waveguide core. By applying a voltage to bias the p-n junction, one can sweep the free carriers to change the effective index of the waveguide as well as the dispersion property of the grating. This metastructure Si waveguide is ideal in the design of high frequency optical modulators since the slow light effect can reduce the modulator waveguide length, increase the modulation efficiency as well as compensate other nonlinearity factors of the modulator for analog applications.

  12. High Resolution X-ray Phase Contrast Imaging with Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2008-06-01

    murine liver. 15. SUBJECT TERMS X-ray, ultrasound, phase contrast, imaging, elastography 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF...of the veins in a mouse liver that was excised from an euthanized mouse, fixed in paraformaldehyde and subsequently dried. The vascular tree is...clearly visible in the x-ray image. Contrast agent injections into the portal vein of another mouse liver verified that the veins are imaged and not

  13. The CHARIS IFS for high contrast imaging at Subaru

    NASA Technical Reports Server (NTRS)

    Groff, Tyler D.; Kasdin, N. Jeremy; Limbach, Mary Anne; Galvin, Michael; Carr, Michael A.; Knapp, Gillian; Brandt, Timothy; Loomis, Craig; Jarosik, Norman; Mede, Kyle; McElwain, Michael William; Leviton, Douglas B.; Miller, Kevin H.; Quijada, Manuel A.; Guyon, Olivier; Jovanovic, Nemanja; Takato, Naruhisa; Hayashi, Masahiko

    2015-01-01

    The Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) is an integral field spectrograph (IFS) being built for the Subaru telescope. CHARIS will take spectra of brown dwarfs and hot Jovian planets in the coronagraphic image provided by the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) and AO188 adaptive optics systems. The system is designed to detect objects five orders of magnitude dimmer than their parent star down to an 80 milliarcsecond inner working angle. For characterization, CHARIS has a high-resolution prism providing an average spectral resolution of R82, R69, and R82 in J, H, and K bands respectively. The so-called discovery mode uses a second low-resolution prism with an average spectral resolution of R19 spanning 1.15-2.37 microns (J+H+K bands). This is unique compared to other high contrast IFS designs. It augments low inner working angle performance by reducing the separation at which we can rely on spectral differential imaging. The principal challenge for a high-contrast IFS is quasi-static speckles, which cause undue levels of spectral crosstalk. CHARIS has addressed this through several key design aspects that should constrain crosstalk between adjacent spectral features to be below 1%. Sitting on the Nasmyth platform, the alignment between the lenslet array, prism, and detector will be highly stable, key for the performance of the data pipeline. Nearly every component has arrived and the project is entering its final build phase. Here we review the science case, the resulting design, status of final construction, and lessons learned that are directly applicable to future exoplanet instruments.

  14. Test-Taking Strategies of High and Low Mathematics Achievers

    ERIC Educational Resources Information Center

    Hong, Eunsook; Sas, Maggie; Sas, John C.

    2006-01-01

    The authors explored test-preparation and test-taking strategies that high school students used in algebra tests. From a pool of high school students (N = 156), 61 students participated in interviews, and of those interviewed, 26 represented those who were high achieving as well as highly interested in mathematics (n = 15) vs. those who were low…

  15. Some Correlates of High School Foreign Language Achievement.

    ERIC Educational Resources Information Center

    Beanblossom, Gary F.

    This paper investigates the influences of traditional kinds of verbal and quantitative achievement and aptitude variables on high school foreign language achievement, as measured by Modern Language Association and University of Washington tests of language skills administered to entering college students. The report focuses on: (1) the sample and…

  16. High-contrast and fast electrochromic switching enabled by plasmonics (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Talin, A. Alec

    2016-09-01

    With vibrant colors and simple, room-temperature processing methods, electrochromic polymers have long attracted attention as active materials for flexible, low-power consuming devices such as smart windows and displays. However, despite their many advantages, slow switching speed and complexity of combining several separate polymers to achieve full-color gamut has limited electrochromic materials to niche applications. Here we exploit the enhanced light-matter interaction associated with the deep-subwavelength mode confinement of surface plasmon polaritons propagating in metallic nanoslit arrays coated with ultra-thin electrochromic polymers to build a novel configuration for achieving high-contrast and fast electrochromic switching. The switchable configuration retains the short temporal charge-diffusion characteristics of thin electrochromic films while maintaining the high optical-contrast associated with thicker electrochromic coatings. We further demonstrate that by controlling the pitch of the nanoslit arrays, it is possible to achieve a full-color response with high-contrast and fast switching-speeds while relying on just one electrochromic polymer.

  17. Attitudes and Opinions from the Nation's High Achieving Teens: 29th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This report presents the 1998 statistical findings of the annual survey to determine the attitudes of national high school student leaders. Questionnaires were completed by 3,123 high school juniors and seniors, all of whom were selected for recognition in "Who's Who among American High School Students." In addition to demographic…

  18. Achievement Motivation Training for Potential High School Dropouts. Achievement Motivation Development Project Working Paper Number 4.

    ERIC Educational Resources Information Center

    McClelland, David C.

    This pilot project sought to determine if instruction in achievement motivation would help potential dropouts to complete their schooling. Subjects were tenth grade students in a suburban Boston high school. A one-week residential course during winter and spring vacations was taken by one group of six boys and a second group of four. Equated…

  19. High-contrast enzymatic immunohistochemistry of pigmented tissues

    PubMed Central

    Duncan, Sara M.; Seigel, Gail M.

    2016-01-01

    Historically, standard enzyme immunohistochemistry has been accomplished with brown (DAB, diaminobenzidine) substrate. This can become problematic in pigmented tissues, such as the retina, where brown pigment of retinal pigmented epithelial (RPE) cells can be easily confounded with brown substrate. Although immunofluorescence detection methods can overcome this challenge, fluorescence may fade over a period of weeks, while enzyme substrates allow for more long-lasting, archival results. In this report, we will describe a high-contrast enzyme immunohistochemistry method ideal for pigmented tissues that utilizes purple (VIP) substrate. We compared brown (DAB) and purple (VIP) substrates in enzyme immunohistochemistry experiments using human retina (paraffin sections) and monkey retinal pigmented epithelial cells (frozen sections), both containing brown pigmented cells. We compared substrates using several primary antibodies against markers that can be detected in the retina, including GFAP, VEGF, CD147 (EMMPRIN), RHO (rhodopsin) and PAX6. Methyl green was used as a counterstain for paraffin sections. A side-by-side comparison between DAB and VIP immunohistochemistry showed excellent contrast between pigmented cells and the purple VIP substrate in both human retinal tissue and monkey pigmented epithelial cells for all of the markers tested. This was a marked improvement over DAB staining in pigmented cells and tissues. For both paraffin sections and frozen sections of pigmented tissues, purple VIP substrate is an excellent alternative to brown DAB substrate and non-permanent immunofluorescence methods. PMID:27660801

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Behavior of imperfect band-limited coronagraphic masks in a high-contrast imaging system.

    PubMed

    Sidick, Erkin; Wilson, Daniel W

    2007-03-20

    We investigate the behavior of imperfect band-limited occulting masks in a high-contrast imaging system through modeling and simulations. Grayscale masks having 1D Sinc(2) (linear-Sinc(2)) amplitude transmission coefficient (Sinc(4) intensity transmittance) profiles as well as optical density and wavelength-dependent parasitic phases are considered occulters. We compare the behaviors of several, slightly different occulter transmittance profiles by evaluating the contrast performance of the high-contrast imaging testbed (HCIT) at the Jet Propulsion Laboratory (JPL). These occulters include a measured occulter, a standard Sinc(2) occulter, and several of its variations. We show that when an occulting mask has a parasitic phase, a modified Sinc(2) transmittance profile works much better than the standard Sinc(2) mask. We examine the impact of some fabrication errors of the occulter on the HCIT's contrast performance. We find through modeling and simulations that starlight suppression by a factor of more than 10(10) is achievable at least monochromatically on the HCIT with the occulting mask and the optics currently being used on the testbed. To the best of our knowledge, this is the first time that we investigate the behavior of a real (or fabricated) focal plane occulting mask in a high-contrast imaging system. We also briefly describe the approach used at JPL in fabricating a grayscale occulting mask and characterizing its transmittance and phase profiles.

  2. High Resolution X-Ray Phase Contrast Imaging with Acoustic Tissue-Selective Contrast Enhancement

    DTIC Science & Technology

    2007-06-01

    Contrast and resolution in imaging with microfocus x - ray source. Rev. Sci. Instr. 68, 2774 (1997). 8. Krol, A. et al. Laser-based microfocused x - ray ...water jet of carbon suspension and imaged using a microfocus x - ray source coupled in-line with a synchronously gated intensified optically coupled...

  3. Attitudes and Opinions from the Nation's High Achieving Teens: 28th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This report details the 28th annual study to examine the attitudes of student leaders in U.S. high schools. Participating in the survey were 3,210 adolescents, primarily 16- and 17-year-olds, who had been featured in the 1997 edition of "Who's Who Among American High School Students." The report presents demographic information on the…

  4. Attitudes and Opinions from the Nation's High Achieving Teens: 27th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This report details the 27th annual study to examine the attitudes of student leaders in U.S. high schools. Participating in the survey were 3,370 adolescents, primarily 16- and 17-year-olds, who had been featured in the 1996 edition of "Who's Who Among American High School Students." The report presents demographic information on the survey…

  5. High-Contrast Gratings based Spoof Surface Plasmons

    PubMed Central

    Li, Zhuo; Liu, Liangliang; Xu, Bingzheng; Ning, Pingping; Chen, Chen; Xu, Jia; Chen, Xinlei; Gu, Changqing; Qing, Quan

    2016-01-01

    In this work, we explore the existence of spoof surface plasmons (SSPs) supported by deep-subwavelength high-contrast gratings (HCGs) on a perfect electric conductor plane. The dispersion relation of the HCGs-based SSPs is derived analyt- ically by combining multimode network theory with rigorous mode matching method, which has nearly the same form with and can be degenerated into that of the SSPs arising from deep-subwavelength metallic gratings (MGs). Numerical simula- tions validate the analytical dispersion relation and an effective medium approximation is also presented to obtain the same analytical dispersion formula. This work sets up a unified theoretical framework for SSPs and opens up new vistas in surface plasmon optics. PMID:26879637

  6. High contrast single molecule tracking in the pericellular coat

    NASA Astrophysics Data System (ADS)

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

    PubMed

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

    2014-10-06

    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.

  8. Attitudes and Opinions from the Nation's High Achieving Teens. 25th Annual Survey of High Achievers.

    ERIC Educational Resources Information Center

    Who's Who among American High School Students, Lake Forest, IL.

    This survey was conducted during the spring of 1994 for the purpose of determining the attitudes of student leaders in the nation's high schools. Eight thousand surveys were sent out to students, of which 3177 were returned. All students surveyed were members of the junior or senior class during the 1993-94 academic year. They were selected for…

  9. A qualitative analysis of the nonverbal and verbal interactions of low achieving students in two contrasting science instructional settings

    NASA Astrophysics Data System (ADS)

    Logan, Laverne K.

    This research project was designed to describe and analyze the verbal and non-verbal interactions of low achieving students during science lessons taught in two contrasting science instructional settings. (1) Teacher-centered, textbook-dominated instruction and (2) Student-centered, materials-dominated instruction. This study provided the unique opportunity to observe individual students under both sets of conditions. Systematic classroom observation, non-structured student interviews, and student documents were used in the analysis. Levels of behavioral involvement were found to be lower during student-centered, materials-dominated lessons, however, increased frequencies, more varied types, and higher cognitive levels of verbal interaction were observed. Teacher-centered, text-dominated lessons yielded increased levels of on-task behavior, however, incidences of verbal interaction were observed to be decreased, less varied, and lower in cognitive level. The findings of this study suggest that the levels of behavioral involvement of low achieving students may be enhanced by increased structuring of the science learning environment. The findings suggest that additional structure in the form of task-specific directions and specific, short time allotments would enable low achieving students to better define a researchable question, and plan and conduct an investigation to answer the question. Low achieving students appeared to lack small group interaction skills needed to complete activities in the materials-dominated format. Groups of four tended to splinter: pairs would break off or students just worked individually. If groups of four are desired, the evidence from this study would suggest clearly defined expectations and shorter work times and more structure are needed for more effective group work. Questions remain concerning the ability for elementary science teachers to monitor the learning environment and learning processes, particularly in less structured

  10. What Does Quality Programming Mean for High Achieving Students?

    ERIC Educational Resources Information Center

    Samudzi, Cleo

    2008-01-01

    The Missouri Academy of Science, Mathematics and Computing (Missouri Academy) is a two-year accelerated, early-entrance-to-college, residential school that matches the level, complexity and pace of the curriculum with the readiness and motivation of high achieving high school students. The school is a part of Northwest Missouri State University…

  11. High School Employment and Academic Achievement: A Note for Educators

    ERIC Educational Resources Information Center

    Keister, Mary; Hall, Joshua

    2010-01-01

    Educators are often in a position to affect student decisions to work during the school term. This study reviews and summarizes the literature on the effect that employment during high school has on academic achievement. The available evidence suggests that part-time jobs for high school students are beneficial as long as the number of hours…

  12. High-Stakes Testing: Does It Increase Achievement?

    ERIC Educational Resources Information Center

    Nichols, Sharon L.

    2007-01-01

    I review the literature on the impact on student achievement of high-stakes testing. Its popularity as a mechanism for holding educators accountable has triggered studies to examine whether its promise to increase student learning has been fulfilled. The review concludes there is no consistent evidence to suggest high-stakes testing leads to…

  13. Brain Hemisphericity and Mathematics Achievement of High School Students

    ERIC Educational Resources Information Center

    Fernandez, Sanny F.

    2011-01-01

    This study aimed to find out the brain hemisphericity and mathematics achievement of high school students. The respondents of the study were the 168 first year high school students of Colegio de San Jose, during school year 2010-2011 who were chosen through stratified random sampling. The descriptive and interview methods of research were used in…

  14. Exploring High-Achieving Students' Images of Mathematicians

    ERIC Educational Resources Information Center

    Aguilar, Mario Sánchez; Rosas, Alejandro; Zavaleta, Juan Gabriel Molina; Romo-Vázquez, Avenilde

    2016-01-01

    The aim of this study is to describe the images that a group of high-achieving Mexican students hold of mathematicians. For this investigation, we used a research method based on the Draw-A-Scientist Test (DAST) with a sample of 63 Mexican high school students. The group of students' pictorial and written descriptions of mathematicians assisted us…

  15. Achieving the College Dream? Examining Disparities in Access to College Information among High Achieving and Non-High Achieving Latina Students

    ERIC Educational Resources Information Center

    Kimura-Walsh, Erin; Yamamura, Erica K.; Griffin, Kimberly A.; Allen, Walter R.

    2009-01-01

    Using an Opportunity to Learn (OTL) framework, this study examines the college preparatory experiences of Latina high and non-high achievers at an urban Latina/o majority high school. Findings indicate that students relied almost exclusively on school resources to navigate their college preparation process. However, the school provided…

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

    NASA Astrophysics Data System (ADS)

    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.

  17. MISR empirical stray light corrections in high-contrast scenes

    NASA Astrophysics Data System (ADS)

    Limbacher, J. A.; Kahn, R. A.

    2015-07-01

    We diagnose the potential causes for the Multi-angle Imaging SpectroRadiometer's (MISR) persistent high aerosol optical depth (AOD) bias at low AOD with the aid of coincident MODerate-resolution Imaging Spectroradiometer (MODIS) imagery from NASA's Terra satellite. Stray light in the MISR instrument is responsible for a large portion of the high AOD bias in high-contrast scenes, such as broken-cloud scenes that are quite common over ocean. Discrepancies among MODIS and MISR nadir-viewing blue, green, red, and near-infrared images are used to optimize seven parameters individually for each wavelength, along with a background reflectance modulation term that is modeled separately, to represent the observed features. Independent surface-based AOD measurements from the AErosol RObotic NETwork (AERONET) and the Marine Aerosol Network (MAN) are compared with MISR research aerosol retrieval algorithm (RA) AOD retrievals for 1118 coincidences to validate the corrections when applied to the nadir and off-nadir cameras. With these corrections, plus the baseline RA corrections and enhanced cloud screening applied, the median AOD bias for all data in the mid-visible (green, 558 nm) band decreases from 0.006 (0.020 for the MISR standard algorithm (SA)) to 0.000, and the RMSE decreases by 5 % (27 % compared to the SA). For AOD558 nm < 0.10, which includes about half the validation data, 68th percentile absolute AOD558 nm errors for the RA have dropped from 0.022 (0.034 for the SA) to < 0.02 (~ 0.018).

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. High-contrast Imaging with an Arbitrary Aperture: Active Compensation of Aperture Discontinuities

    NASA Astrophysics Data System (ADS)

    Pueyo, Laurent; Norman, Colin

    2013-06-01

    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 (DMs) 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 DM surfaces that yield high-contrast point-spread functions is not linear, and nonlinear methods are needed to find the true minimum in the optimization topology. We solve the highly nonlinear 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 DM 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 the James Webb Space Telescope, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for both the future extremely large telescopes and on-axis architectures reminiscent of the Hubble Space Telescope. We show that the converging nonlinear mappings resulting from our DM 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 struts while not amplifying the diffraction at the aperture edges beyond the Fresnel regime. This outer Fresnel ringing can be mitigated by properly designing the optical system. Consequently, ACAD is a true broadband solution to the problem of high-contrast imaging with segmented and/or on-axis apertures. We finally show that once the nonlinear solution is found, fine tuning with linear methods used in wavefront control can be applied to further contrast by another order of magnitude. Generally speaking, the

  1. High-contrast imaging with an arbitrary aperture: Active compensation of aperture discontinuities

    SciTech Connect

    Pueyo, Laurent; Norman, Colin

    2013-06-01

    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 (DMs) 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 DM surfaces that yield high-contrast point-spread functions is not linear, and nonlinear methods are needed to find the true minimum in the optimization topology. We solve the highly nonlinear 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 DM 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 the James Webb Space Telescope, ACAD can attain at least 10{sup –7} in contrast and an order of magnitude higher for both the future extremely large telescopes and on-axis architectures reminiscent of the Hubble Space Telescope. We show that the converging nonlinear mappings resulting from our DM 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 struts while not amplifying the diffraction at the aperture edges beyond the Fresnel regime. This outer Fresnel ringing can be mitigated by properly designing the optical system. Consequently, ACAD is a true broadband solution to the problem of high-contrast imaging with segmented and/or on-axis apertures. We finally show that once the nonlinear solution is found, fine tuning with linear methods used in wavefront control can be applied to further contrast by another order of magnitude. Generally speaking

  2. Fundamental Limitations of High Contrast Imaging Set by Small Sample Statistics

    NASA Astrophysics Data System (ADS)

    Mawet, D.; Milli, J.; Wahhaj, Z.; Pelat, D.; Absil, O.; Delacroix, C.; Boccaletti, A.; Kasper, M.; Kenworthy, M.; Marois, C.; Mennesson, B.; Pueyo, L.

    2014-09-01

    In this paper, we review the impact of small sample statistics on detection thresholds and corresponding confidence levels (CLs) in high-contrast imaging at small angles. When looking close to the star, the number of resolution elements decreases rapidly toward small angles. This reduction of the number of degrees of freedom dramatically affects CLs and false alarm probabilities. Naively using the same ideal hypothesis and methods as for larger separations, which are well understood and commonly assume Gaussian noise, can yield up to one order of magnitude error in contrast estimations at fixed CL. The statistical penalty exponentially increases toward very small inner working angles. Even at 5-10 resolution elements from the star, false alarm probabilities can be significantly higher than expected. Here we present a rigorous statistical analysis that ensures robustness of the CL, but also imposes a substantial limitation on corresponding achievable detection limits (thus contrast) at small angles. This unavoidable fundamental statistical effect has a significant impact on current coronagraphic and future high-contrast imagers. Finally, the paper concludes with practical recommendations to account for small number statistics when computing the sensitivity to companions at small angles and when exploiting the results of direct imaging planet surveys.

  3. Fundamental limitations of high contrast imaging set by small sample statistics

    SciTech Connect

    Mawet, D.; Milli, J.; Wahhaj, Z.; Pelat, D.; Absil, O.; Delacroix, C.; Boccaletti, A.; Kasper, M.; Kenworthy, M.; Marois, C.; Mennesson, B.; Pueyo, L.

    2014-09-10

    In this paper, we review the impact of small sample statistics on detection thresholds and corresponding confidence levels (CLs) in high-contrast imaging at small angles. When looking close to the star, the number of resolution elements decreases rapidly toward small angles. This reduction of the number of degrees of freedom dramatically affects CLs and false alarm probabilities. Naively using the same ideal hypothesis and methods as for larger separations, which are well understood and commonly assume Gaussian noise, can yield up to one order of magnitude error in contrast estimations at fixed CL. The statistical penalty exponentially increases toward very small inner working angles. Even at 5-10 resolution elements from the star, false alarm probabilities can be significantly higher than expected. Here we present a rigorous statistical analysis that ensures robustness of the CL, but also imposes a substantial limitation on corresponding achievable detection limits (thus contrast) at small angles. This unavoidable fundamental statistical effect has a significant impact on current coronagraphic and future high-contrast imagers. Finally, the paper concludes with practical recommendations to account for small number statistics when computing the sensitivity to companions at small angles and when exploiting the results of direct imaging planet surveys.

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

    PubMed

    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. Self-Esteem and Academic Achievement of High School Students

    ERIC Educational Resources Information Center

    Moradi Sheykhjan, Tohid; Jabari, Kamran; Rajeswari, K.

    2014-01-01

    The primary purpose of this study was to determine the influence of self-esteem on academic achievement among high school students in Miandoab City of Iran. The methodology of the research is descriptive and correlation that descriptive and inferential statistics were used to analyze the data. Statistical Society includes male and female high…

  6. Comparison of Achievement of Students in High School Courses

    ERIC Educational Resources Information Center

    Troxel, Verne A.

    1970-01-01

    Compares student achievements on common objectives of CHEMS, CBA, and "Modern Chemistry high school chemistry courses. Results indicate the three couses are not equally effective in meeting their objectives. CHEMS and CBA develop a better understanding of chemistry and science, as well as develop greater ability for critical thinking. CBA…

  7. Relationship between High School Leadership Team Practices and Student Achievement

    ERIC Educational Resources Information Center

    McInnis, Timothy M.

    2009-01-01

    This study investigated if a relationship existed between student achievement in 10th grade Missouri Assessment Program mathematics and 11th grade communication arts scores in 2007 and high school leadership team perceptions of the extent to which they demonstrated leadership practices. The secondary purpose was to compare perceptional…

  8. Early College High School: Closing the Latino Achievement Gap

    ERIC Educational Resources Information Center

    Beall, Kristen Ann

    2016-01-01

    The population of United States Latino students is growing at a rapid rate but their academic achievement lags behind white and Asian students. This issue has significant consequences for the nation's economy, as the job market continues to demand more education and better skills. Early College High School programs have the potential to improve…

  9. Confidence Level and Sensitivity Limits in High Contrast Imaging

    SciTech Connect

    Marois, C; LaFreniere, D; Macintosh, B; Doyon, R

    2008-06-02

    In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground and space-based telescopes. Previous theoretical analysis have shown that the time intensity variations of a single speckle follows a modified Rician. It is first demonstrated here that for a circular pupil this temporal intensity distribution also represents the speckle spatial intensity distribution at a fix separation from the point spread function center; this fact is demonstrated using numerical simulations for coronagraphic and non-coronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level. In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding confidence level as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckles noise, a detection threshold up to three times higher is required to obtain a confidence level equivalent to that at 5{sigma} for Gaussian noise. The technique is then tested using TRIDENT CFHT and angular differential imaging NIRI Gemini adaptive optics data. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. A power-law is finally derived to predict the 1-3 x 10{sup -7} confidence level detection threshold when averaging a partially correlated non-Gaussian noise.

  10. Confidence Level and Sensitivity Limits in High Contrast Imaging

    SciTech Connect

    Marois, C

    2007-11-07

    In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground and space-based telescopes. Previous theoretical analysis have shown that the time intensity variations of a single speckle follows a modified Rician. It is first demonstrated here that for a circular pupil this temporal intensity distribution also represents the speckle spatial intensity distribution at a fix separation from the point spread function center; this fact is demonstrated using numerical simulations for coronagraphic and non-coronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level. In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding confidence level as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckles noise, a detection threshold up to three times higher is required to obtain a confidence level equivalent to that at 5{sigma} for Gaussian noise. The technique is then tested using TRIDENT CFHT and angular differential imaging NIRI Gemini adaptive optics data. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. A power-law is finally derived to predict the 1-3 x 10{sup -7} confidence level detection threshold when averaging a partially correlated non-Gaussian noise.

  11. High-Contrast NIR Polarization Imaging of MWC480

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. High-contrast in vivo visualization of microvessels using novel FeCo/GC magnetic nanocrystals.

    PubMed

    Lee, Jin Hyung; Sherlock, Sarah P; Terashima, Masahiro; Kosuge, Hisanori; Suzuki, Yoriyasu; Goodwin, Andrew; Robinson, Joshua; Seo, Won Seok; Liu, Zhuang; Luong, Richard; McConnell, Michael V; Nishimura, Dwight G; Dai, Hongjie

    2009-12-01

    FeCo-graphitic carbon shell nanocrystals are a novel MRI contrast agent with unprecedented high per-metal-atom-basis relaxivity (r(1) = 97 mM(-1) sec(-1), r(2) = 400 mM(-1) sec(-1)) and multifunctional capabilities. While the conventional gadolinium-based contrast-enhanced angiographic magnetic MRI has proven useful for diagnosis of vascular diseases, its short circulation time and relatively low sensitivity render high-resolution MRI of morphologically small vascular structures such as those involved in collateral, arteriogenic, and angiogenic vessel formation challenging. Here, by combining FeCo-graphitic carbon shell nanocrystals with high-resolution MRI technique, we demonstrate that such microvessels down to approximately 100 mum can be monitored in high contrast and noninvasively using a conventional 1.5-T clinical MRI system, achieving a diagnostic imaging standard approximating that of the more invasive X-ray angiography. Preliminary in vitro and in vivo toxicity study results also show no sign of toxicity.

  14. High-Contrast In Vivo Visualization of Microvessels Using Novel FeCo/GC Magnetic Nanocrystals

    PubMed Central

    Lee, Jin Hyung; Sherlock, Sarah P.; Terashima, Masahiro; Kosuge, Hisanori; Suzuki, Yoriyasu; Goodwin, Andrew; Robinson, Joshua; Seo, Won Seok; Liu, Zhuang; Luong, Richard; McConnell, Michael V.; Nishimura, Dwight G.; Dai, Hongjie

    2010-01-01

    FeCo-graphitic carbon shell nanocrystals are a novel MRI contrast agent with unprecedented high per-metal-atom-basis relaxivity (r1 = 97 mM−1 sec−1, r2 = 400 mM−1 sec−1) and multifunctional capabilities. While the conventional gadolinium-based contrast-enhanced angiographic magnetic MRI has proven useful for diagnosis of vascular diseases, its short circulation time and relatively low sensitivity render high-resolution MRI of morphologically small vascular structures such as those involved in collateral, arteriogenic, and angiogenic vessel formation challenging. Here, by combining FeCo-graphitic carbon shell nanocrystals with high-resolution MRI technique, we demonstrate that such microvessels down to ~100 μm can be monitored in high contrast and noninvasively using a conventional 1.5-T clinical MRI system, achieving a diagnostic imaging standard approximating that of the more invasive X-ray angiography. Preliminary in vitro and in vivo toxicity study results also show no sign of toxicity. PMID:19859938

  15. Contrast enhanced high-resolution diffuse optical tomography of the human brain using ICG

    PubMed Central

    Habermehl, Christina; Schmitz, Christoph H.; Steinbrink, Jens

    2011-01-01

    Non-invasive diffuse optical tomography (DOT) of the adult brain has recently been shown to improve the spatial resolution for functional brain imaging applications. Here we show that high-resolution (HR) DOT is also advantageous for clinical perfusion imaging using an optical contrast agent. We present the first HR-DOT results with a continuous wave near infrared spectroscopy setup using a dense grid of optical fibers and indocyanine green (ICG) as an exogenic contrast agent. We find an early arrival of the ICG bolus in the intracerebral tissue and a delayed arrival of the bolus in the extracerebral tissue, achieving the separation of both layers. This demonstrates the method’s potential for brain perfusion monitoring in neurointensive care patients. PMID:21935232

  16. Parent Involvement Practices of High-Achieving Elementary Science Students

    NASA Astrophysics Data System (ADS)

    Waller, Samara Susan

    This study addressed a prevalence of low achievement in science courses in an urban school district in Georgia. National leaders and educators have identified the improvement of science proficiency as critical to the future of American industry. The purpose of this study was to examine parent involvement in this school district and its contribution to the academic achievement of successful science students. Social capital theory guided this study by suggesting that students achieve best when investments are made into their academic and social development. A collective case study qualitative research design was used to interview 9 parent participants at 2 elementary schools whose children scored in the exceeds category on the Science CRCT. The research questions focused on what these parents did at home to support their children's academic achievement. Data were collected using a semi-structured interview protocol and analyzed through the categorical aggregation of transcribed interviews. Key findings revealed that the parents invested time and resources in 3 practices: communicating high expectations, supporting and developing key skills, and communicating with teachers. These findings contribute to social change at both the local and community level by creating a starting point for teachers, principals, and district leaders to reexamine the value of parent input in the educational process, and by providing data to support the revision of current parent involvement policies. Possibilities for further study building upon the findings of this study may focus on student perceptions of their parents' parenting as it relates to their science achievement.

  17. The Construction of Black High-Achiever Identities in a Predominantly White High School

    ERIC Educational Resources Information Center

    Andrews, Dorinda J. Carter

    2009-01-01

    In this article, I examine how black students construct their racial and achievement self-concepts in a predominantly white high school to enact a black achiever identity. By listening to these students talk about the importance of race and achievement to their lives, I came to understand how racialized the task of achieving was for them even…

  18. Improving science achievement at high-poverty urban middle schools

    NASA Astrophysics Data System (ADS)

    Ruby, Allen

    2006-11-01

    A large percentage of U.S. students attending high-poverty urban middle schools achieve low levels of science proficiency, posing significant challenges to their success in high school science and to national and local efforts to reform science education. Through its work in Philadelphia schools, the Center for Social Organization of Schools at Johns Hopkins University developed a teacher-support model to address variation in science curricula, lack of materials, and underprepared teachers that combined with initial low levels of proficiency block improvements in science achievement. The model includes a common science curriculum based on NSF-supported materials commercially available, ongoing teacher professional development built around day-to-day lessons, and regular in-class support of teachers by expert peer coaches. One cohort of students at three Philadelphia middle schools using the model was followed from the end of fourth grade through seventh grade. Their gains in science achievement and achievement levels were substantially greater than students at 3 matched control schools and the 23 district middle schools serving a similar student population. Under school-by-school comparisons, these results held for the two schools with adequate implementation. Using widely available materials and techniques, the model can be adopted and modified by school partners and districts.

  19. Contrast Imaging in Mouse Embryos Using High-frequency Ultrasound

    PubMed Central

    Denbeigh, Janet M.; Nixon, Brian A.; Puri, Mira C.; Foster, F. Stuart

    2015-01-01

    Ultrasound contrast-enhanced imaging can convey essential quantitative information regarding tissue vascularity and perfusion and, in targeted applications, facilitate the detection and measure of vascular biomarkers at the molecular level. Within the mouse embryo, this noninvasive technique may be used to uncover basic mechanisms underlying vascular development in the early mouse circulatory system and in genetic models of cardiovascular disease. The mouse embryo also presents as an excellent model for studying the adhesion of microbubbles to angiogenic targets (including vascular endothelial growth factor receptor 2 (VEGFR2) or αvβ3) and for assessing the quantitative nature of molecular ultrasound. We therefore developed a method to introduce ultrasound contrast agents into the vasculature of living, isolated embryos. This allows freedom in terms of injection control and positioning, reproducibility of the imaging plane without obstruction and motion, and simplified image analysis and quantification. Late gestational stage (embryonic day (E)16.6 and E17.5) murine embryos were isolated from the uterus, gently exteriorized from the yolk sac and microbubble contrast agents were injected into veins accessible on the chorionic surface of the placental disc. Nonlinear contrast ultrasound imaging was then employed to collect a number of basic perfusion parameters (peak enhancement, wash-in rate and time to peak) and quantify targeted microbubble binding in an endoglin mouse model. We show the successful circulation of microbubbles within living embryos and the utility of this approach in characterizing embryonic vasculature and microbubble behavior. PMID:25867243

  20. Contrast imaging in mouse embryos using high-frequency ultrasound.

    PubMed

    Denbeigh, Janet M; Nixon, Brian A; Puri, Mira C; Foster, F Stuart

    2015-03-04

    Ultrasound contrast-enhanced imaging can convey essential quantitative information regarding tissue vascularity and perfusion and, in targeted applications, facilitate the detection and measure of vascular biomarkers at the molecular level. Within the mouse embryo, this noninvasive technique may be used to uncover basic mechanisms underlying vascular development in the early mouse circulatory system and in genetic models of cardiovascular disease. The mouse embryo also presents as an excellent model for studying the adhesion of microbubbles to angiogenic targets (including vascular endothelial growth factor receptor 2 (VEGFR2) or αvβ3) and for assessing the quantitative nature of molecular ultrasound. We therefore developed a method to introduce ultrasound contrast agents into the vasculature of living, isolated embryos. This allows freedom in terms of injection control and positioning, reproducibility of the imaging plane without obstruction and motion, and simplified image analysis and quantification. Late gestational stage (embryonic day (E)16.6 and E17.5) murine embryos were isolated from the uterus, gently exteriorized from the yolk sac and microbubble contrast agents were injected into veins accessible on the chorionic surface of the placental disc. Nonlinear contrast ultrasound imaging was then employed to collect a number of basic perfusion parameters (peak enhancement, wash-in rate and time to peak) and quantify targeted microbubble binding in an endoglin mouse model. We show the successful circulation of microbubbles within living embryos and the utility of this approach in characterizing embryonic vasculature and microbubble behavior.

  1. Electrical Capacitance Volume Tomography with High-Contrast Dielectrics

    NASA Technical Reports Server (NTRS)

    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

  2. Demonstration of symmetric dark holes using two deformable mirrors at the high-contrast imaging testbed

    NASA Astrophysics Data System (ADS)

    Riggs, A. J. Eldorado; Groff, Tyler D.; Carlotti, Alexis; Kasdin, N. Jeremy; Cady, Eric J.; Kern, Brian D.; Kuhnert, Andreas

    2013-09-01

    The High Contrast Imaging Laboratory (HCIL) at Princeton has developed several important algorithms and technologies for space-based coronagraphy missions to detect earth-like exoplanets. Before June 2013 the HCIL was the only facility with two deformable mirrors (DMs) in series for focal plane wavefront control, which allows for quasi-static speckle correction on both sides of the image plane. From June through August 2013, the High- Contrast Imaging Testbed (HCIT) at JPL had a second DM installed. In this paper we report on the results of our Technology Development for Exoplanet Missions project to achieve high contrast in two symmetric dark holes using a shaped pupil (SP) coronagraph at the HCIT. Our previous experiment with a similar SP at the HCIT in 2007 yielded single-sided dark holes. That experiment utilized an iterative, batch-process wavefront estimator and Electric Field Conjugation for wavefront control. Our current tests use the faster Kalman filter estimator and the stroke minimization control algorithm. We use the same ripple-style SPs as in the previous HCIT experiment because that mask manufacturing technique proved successful. Our tests of symmetric dark holes in monochromatic light at the HCIT demonstrate Princeton's steady improvements in wavefront control and estimation techniques for a space-based coronagraphy mission.

  3. The Will to Achieve: A Phenomenological Study of the Experiences of African American High Achieving Students and Their Parents

    ERIC Educational Resources Information Center

    Spencer, Natalie Faye

    2012-01-01

    The purpose of this research study was to understand the experiences of high achieving African American students and their parents. The experiences of high achieving African American students and their parents have been missing from literature on the academic achievement of African American students. Much of the literature that has been published…

  4. A High Contrast Tri-state Fluorescent Switch: Properties and Applications.

    PubMed

    Su, Xing; Wang, Yi; Fang, Xiaofeng; Zhang, Yu-Mo; Zhang, Ting; Li, Minjie; Liu, Yifei; Lin, Tingting; Zhang, Sean Xiao-An

    2016-11-22

    A high contrast tri-state fluorescent switch (FSPTPE) with both emission color change and on/off switching is achieved in a single molecular system by fusing the aggregation-induced emissive tetraphenylethene (TPE) with a molecular switch of spiropyran (SP). In contrast to most of the reported solid-state fluorescent switches, FSPTPE only exists in the amorphous phase in the ring-closed form owing to its highly asymmetric molecular geometry and weak intermolecular interactions, which leads to its grinding-inert stable cyan emission in the solid state. Such an amorphous phase facilitates the fast response of FSPTPE to acidic gases and induces the structural transition from the ring-closed form to ring-open form, accompanied with the "Off" state of the fluorescence. The structural transition leads to a planar molecular conformation and high dipole moment, which further results in strong intermolecular interactions and good crystallinity, so when the acid is added together with a solvent, both the ring-opening reaction and re-crystallization can be triggered to result in an orange emissive state. The reversible control between any two of the three states (cyan/orange/dark) can be achieved with acid/base or mechanical force/solvent treatment. Because of the stable initial state and high color contrast (Δλ=120 nm for cyan/orange switch, dark state ΦF <0.01 %), the fluorescent switch is very promising for applications such as displays, chemical or mechanical sensing, and anti-counterfeiting.

  5. Achieving High Performance on the i860 Microprocessor

    NASA Technical Reports Server (NTRS)

    Lee, King; Kutler, Paul (Technical Monitor)

    1998-01-01

    The i860 is a high performance microprocessor used in the Intel Touchstone project. This paper proposes a paradigm for programming the i860 that is modelled on the vector instructions of the Cray computers. Fortran callable assembler subroutines were written that mimic the concurrent vector instructions of the Cray. Cache takes the place of vector registers. Using this paradigm we have achieved twice the performance of compiled code on a traditional solve.

  6. High index contrast polysiloxane waveguides fabricated by dry etching

    SciTech Connect

    Madden, S. J.; Zhang, M. Y.; Choi, D.-Y.; Luther-Davies, B.; Charters, R.

    2009-05-15

    The authors demonstrate the production of low loss enhanced index contrast waveguides by reactive ion etching of IPG trade mark sign polysiloxane thin films. The use of a silica mask and CHF{sub 3}/O{sub 2} etch gas led to large etch selectivity between the silica and IPG trade mark sign of >20 and etch rates of >100 nm/min. This work indicates that compact optical circuits could be successfully fabricated for telecommunication applications using polysiloxane films.

  7. Characterization of a high-energy in-line phase contrast tomosynthesis prototype

    PubMed Central

    Wu, Di; Yan, Aimin; Li, Yuhua; Wong, Molly D.; Zheng, Bin; Wu, Xizeng; Liu, Hong

    2015-01-01

    Purpose: In this research, a high-energy in-line phase contrast tomosynthesis prototype was developed and characterized through quantitative investigations and phantom studies. Methods: The prototype system consists of an x-ray source, a motorized rotation stage, and a CMOS detector with a pixel pitch of 0.05 mm. The x-ray source was operated at 120 kVp for this study, and the objects were mounted on the rotation stage 76.2 cm (R1) from the source and 114.3 cm (R2) from the detector. The large air gap between the object and detector guarantees sufficient phase-shift effects. The quantitative evaluation of this prototype included modulation transfer function and noise power spectrum measurements conducted under both projection mode and tomosynthesis mode. Phantom studies were performed including three custom designed phantoms with complex structures: a five-layer bubble wrap phantom, a fishbone phantom, and a chicken breast phantom with embedded fibrils and mass structures extracted from an ACR phantom. In-plane images of the phantoms were acquired to investigate their image qualities through observation, intensity profile plots, edge enhancement evaluations, and/or contrast-to-noise ratio calculations. In addition, the robust phase-attenuation duality (PAD)-based phase retrieval method was applied to tomosynthesis for the first time in this research. It was utilized as a preprocessing method to fully exhibit phase contrast on the angular projection before reconstruction. Results: The resolution and noise characteristics of this high-energy in-line phase contrast tomosynthesis prototype were successfully investigated and demonstrated. The phantom studies demonstrated that this imaging prototype can successfully remove the structure overlapping in phantom projections, obtain delineate interfaces, and achieve better contrast-to-noise ratio after applying phase retrieval to the angular projections. Conclusions: This research successfully demonstrated a high-energy in

  8. Scanning EM of non-heavy metal stained biosamples: Large-field of view, high contrast and highly efficient immunolabeling

    SciTech Connect

    Kuipers, Jeroen; Boer, Pascal de; Giepmans, Ben N.G.

    2015-10-01

    Scanning electron microscopy (SEM) is increasing its application in life sciences for electron density measurements of ultrathin sections. These are traditionally analyzed with transmission electron microscopy (TEM); by most labs, SEM analysis still is associated with surface imaging only. Here we report several advantages of SEM for thin sections over TEM, both for structural inspection, as well as analyzing immuno-targeted labels such as quantum dots (QDs) and gold, where we find that QD-labeling is ten times more efficient than gold-labeling. Furthermore, we find that omitting post-staining with uranyl and lead leads to QDs readily detectable over the ultrastructure, but under these conditions ultrastructural contrast was even almost invisible in TEM examination. Importantly, imaging in SEM with STEM detection leads to both outstanding QDs and ultrastructural contrast. STEM imaging is superior over back-scattered electron imaging of these non-contrasted samples, whereas secondary electron detection cannot be used at all. We conclude that examination of ultrathin sections by SEM, which may be immunolabeled with QDs, will allow rapid and straightforward analysis of large fields with more efficient labeling than can be achieved with immunogold. The large fields of view routinely achieved with SEM, but not with TEM, allows straightforward raw data sharing using virtual microscopy, also known as nanotomy when this concerns EM data in the life sciences. - Highlights: • High resolution and large fields of view via nanotomy or virtual microscopy. • Highly relevant for EM‐datasets where information density is high. • Sample preparation with low contrast good for STEM, not TEM. • Quantum dots now stand out in STEM‐based detection. • 10 Times more efficient labeling with quantum dots compared to gold.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Experiences of High-Achieving High School Students Who Have Taken Multiple Concurrent Advanced Placement Courses

    ERIC Educational Resources Information Center

    Milburn, Kristine M.

    2011-01-01

    Problem: An increasing number of high-achieving American high school students are enrolling in multiple Advanced Placement (AP) courses. As a result, high schools face a growing need to understand the impact of taking multiple AP courses concurrently on the social-emotional lives of high-achieving students. Procedures: This phenomenological…

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

    NASA Astrophysics Data System (ADS)

    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.

  13. High-contrast qubit interactions using multimode cavity QED.

    PubMed

    McKay, David C; Naik, Ravi; Reinhold, Philip; Bishop, Lev S; Schuster, David I

    2015-02-27

    We introduce a new multimode cavity QED architecture for superconducting circuits that can be used to implement photonic memories, more efficient Purcell filters, and quantum simulations of photonic materials. We show that qubit interactions mediated by multimode cavities can have exponentially improved contrast for two qubit gates without sacrificing gate speed. Using two qubits coupled via a three-mode cavity system we spectroscopically observe multimode strong couplings up to 102 MHz and demonstrate suppressed interactions off resonance of 10 kHz when the qubits are ≈600  MHz detuned from the cavity resonance. We study Landau-Zener transitions in our multimode systems and demonstrate quasiadiabatic loading of single photons into the multimode cavity in 25 ns. We introduce an adiabatic gate protocol to realize a controlled-Z gate between the qubits in 95 ns and create a Bell state with 94.7% fidelity. This corresponds to an on/off ratio (gate contrast) of 1000.

  14. Interface Strategy To Achieve Tunable High Frequency Attenuation.

    PubMed

    Lv, Hualiang; Zhang, Haiqian; Ji, Guangbin; Xu, Zhichuan J

    2016-03-01

    Among all polarizations, the interface polarization effect is the most effective, especially at high frequency. The design of various ferrite/iron interfaces can significantly enhance the materials' dielectric loss ability at high frequency. This paper presents a simple method to generate ferrite/iron interfaces to enhance the microwave attenuation at high frequency. The ferrites were coated onto carbonyl iron and could be varied to ZnFe2O4, CoFe2O4, Fe3O4, and NiFe2O4. Due to the ferrite/iron interface inducing a stronger dielectric loss effect, all of these materials achieved broad effective frequency width at a coating layer as thin as 1.5 mm. In particular, an effective frequency width of 6.2 GHz could be gained from the Fe@NiFe2O4 composite.

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

    NASA Astrophysics Data System (ADS)

    Ruane, G. J.; Huby, E.; Absil, O.; Mawet, D.; Delacroix, C.; Carlomagno, B.; Swartzlander, G. A.

    2015-11-01

    Context. 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, 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. Aims: We introduce a phase-only Lyot-plane optic to the vortex coronagraph, which offers improved contrast performance on telescopes with complicated apertures. Potential solutions for the European Extremely Large Telescope (E-ELT) are described. Methods: 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. Results: Numerically, we achieve a contrast on the order of 10-6 for a companion with angular displacement as small as 4λ/D with an E-ELT type aperture. Even in the presence of aberrations, improved performance is expected compared to either a conventional vortex coronagraph or an optimized pupil plane phase element alone.

  16. Unlocking Emergent Talent: Supporting High Achievement of Low-Income, High Ability Students

    ERIC Educational Resources Information Center

    Olszewski-Kubilius, Paula; Clarenbach, Jane

    2012-01-01

    This report takes a comprehensive look at achievement for low-income promising learners--past, present, and future. At its core, it challenges the nation to move beyond its near-singular focus of achieving minimum performance for all students, to identifying and developing the talent of all students who are capable of high achievement, including…

  17. High speed optical phased array using high contrast grating all-pass filters.

    PubMed

    Yang, Weijian; Sun, Tianbo; Rao, Yi; Megens, Mischa; Chan, Trevor; Yoo, Byung-Wook; Horsley, David A; Wu, Ming C; Chang-Hasnain, Connie J

    2014-08-25

    We report a high speed 8x8 optical phased array using tunable 1550 nm all-pass filters with ultrathin high contrast gratings (HCGs) as the microelectromechanical-actuated top reflectors. The all-pass filter design enables a highly efficient phase tuning (1.7 π) with a small actuation voltage (10 V) and actuation displacement of the HCG (50 nm). The microelectromechanical HCG structure facilitates a high phase tuning speed >0.5 MHz. Beam steering is experimentally demonstrated with the optical phased array.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  19. Theoretical analysis of subwavelength high contrast grating reflectors.

    PubMed

    Karagodsky, Vadim; Sedgwick, Forrest G; Chang-Hasnain, Connie J

    2010-08-02

    A simple analytic analysis of the ultra-high reflectivity feature of subwavelength dielectric gratings is developed. The phenomenon of ultra high reflectivity is explained to be a destructive interference effect between the two grating modes. Based on this phenomenon, a design algorithm for broadband grating mirrors is suggested.

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

    SciTech Connect

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

    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

  1. Achieving unusual oxidation state of matter under high pressure

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoli; Lin, Haiqing; Ma, Yanming; Miao, Maosheng

    2013-03-01

    Pressure has many effects to matter including the reduction of the volume, the increase of the coordination number and the broadening of the band-widths. In the past, most of the high-pressure studies focused on structural and electronic state phase transitions. Using first principles calculations and a bias-free structural search method, we will demonstrate that high pressure can lead to high oxidation state of elements that can never be achieved under ambient condition, making high pressure technique a nice tool to explore many traditional topics in solid state and molecular chemistry. As an example, we will show that Hg can transfer the electrons in its outmost d shell to F atoms and form HgF4 molecular crystals under pressure, thereby acting as a true transition metal. Group IIB elements, including Zn, Cd, and Hg are usually defined as post-transition metals because they are commonly oxidized only to the +2 state. Their d shells are completely filled and do not participate in the formation of chemical bonds. Although the synthesis of HgF4 molecules in gas phase was reported before, the molecules show strong instabilities and dissociate. Therefore, the transition metal propensity of Hg remains an open question.

  2. Achieving high energy absorption capacity in cellular bulk metallic glasses

    PubMed Central

    Chen, S. H.; Chan, K. C.; Wu, F. F.; Xia, L.

    2015-01-01

    Cellular bulk metallic glasses (BMGs) have exhibited excellent energy-absorption performance by inheriting superior strength from the parent BMGs. However, how to achieve high energy absorption capacity in cellular BMGs is vital but mysterious. In this work, using step-by-step observations of the deformation evolution of a series of cellular BMGs, the underlying mechanisms for the remarkable energy absorption capacity have been investigated by studying two influencing key factors: the peak stress and the decay of the peak stress during the plastic-flow plateau stages. An analytical model of the peak stress has been proposed, and the predicted results agree well with the experimental data. The decay of the peak stress has been attributed to the geometry change of the macroscopic cells, the formation of shear bands in the middle of the struts, and the “work-softening” nature of BMGs. The influencing factors such as the effect of the strut thickness and the number of unit cells have also been investigated and discussed. Strategies for achieving higher energy absorption capacity in cellular BMGs have been proposed. PMID:25973781

  3. High contrast two-photon imaging of fingermarks

    NASA Astrophysics Data System (ADS)

    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.

  4. High contrast two-photon imaging of fingermarks

    PubMed Central

    Stoltzfus, Caleb R.; Rebane, Aleksander

    2016-01-01

    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. PMID:27053515

  5. High Contrast Ultrafast Imaging of the Human Heart

    PubMed Central

    Papadacci, Clement; Pernot, Mathieu; Couade, Mathieu; Fink, Mathias; Tanter, Mickael

    2014-01-01

    Non-invasive ultrafast imaging for human cardiac applications is a big challenge to image intrinsic waves such as electromechanical waves or remotely induced shear waves in elastography imaging techniques. In this paper we propose to perform ultrafast imaging of the heart with adapted sector size by using diverging waves emitted from a classical transthoracic cardiac phased array probe. As in ultrafast imaging with plane wave coherent compounding, diverging waves can be summed coherently to obtain high-quality images of the entire heart at high frame rate in a full field-of-view. To image shear waves propagation at high SNR, the field-of-view can be adapted by changing the angular aperture of the transmitted wave. Backscattered echoes from successive circular wave acquisitions are coherently summed at every location in the image to improve the image quality while maintaining very high frame rates. The transmitted diverging waves, angular apertures and subapertures size are tested in simulation and ultrafast coherent compounding is implemented on a commercial scanner. The improvement of the imaging quality is quantified in phantom and in vivo on human heart. Imaging shear wave propagation at 2500 frame/s using 5 diverging waves provides a strong increase of the Signal to noise ratio of the tissue velocity estimates while maintaining a high frame rate. Finally, ultrafast imaging with a 1 to 5 diverging waves is used to image the human heart at a frame rate of 900 frames/s over an entire cardiac cycle. Thanks to spatial coherent compounding, a strong improvement of imaging quality is obtained with a small number of transmitted diverging waves and a high frame rate, which allows imaging the propagation of electromechanical and shear waves with good image quality. PMID:24474135

  6. Achieving High Resolution Timer Events in Virtualized Environment

    PubMed Central

    Adamczyk, Blazej; Chydzinski, Andrzej

    2015-01-01

    Virtual Machine Monitors (VMM) have become popular in different application areas. Some applications may require to generate the timer events with high resolution and precision. This however may be challenging due to the complexity of VMMs. In this paper we focus on the timer functionality provided by five different VMMs—Xen, KVM, Qemu, VirtualBox and VMWare. Firstly, we evaluate resolutions and precisions of their timer events. Apparently, provided resolutions and precisions are far too low for some applications (e.g. networking applications with the quality of service). Then, using Xen virtualization we demonstrate the improved timer design that greatly enhances both the resolution and precision of achieved timer events. PMID:26177366

  7. Achievement of high nitrite accumulation via endogenous partial denitrification (EPD).

    PubMed

    Ji, Jiantao; Peng, Yongzhen; Wang, Bo; Wang, Shuying

    2017-01-01

    This study proposed a novel strategy for achievement of partial denitrification driven by endogenous carbon sources in an anaerobic/anoxic/aerobic activated sludge system. Results showed that in the steady-stage, the nitrate-to-nitrite transformation ratio (NTR) was kept at around 87% without nitrate in the effluent. During the anaerobic period, exogenous carbon sources was completely taken up, accompanied by the consumption of glycogen and production of polyhydroxyalkanoates (PHAs). During the anoxic period, nitrate was reduced to nitrite by using PHAs as carbon sources, followed by the replenishment of glycogen. Thus, the phenotype of denitrifying GAOs was clearly observed and endogenous partial denitrification (EPD) occurred. Furthermore, results showed the nitrate reduction was prior to the nitrite reduction in the presence of nitrate, which led to the high nitrite accumulation.

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

    NASA Astrophysics Data System (ADS)

    Skemer, Andrew J.; Hinz, Philip; Esposito, Simone; Skrutskie, Michael F.; Defrère, Denis; Bailey, Vanessa; Leisenring, Jarron; Apai, Daniel; Biller, Beth; Bonnefoy, Mickaël.; 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

    2014-07-01

    In Spring 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began its ~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 μm), as opposed to the shorter wavelength near-infrared bands (1-2.4 μm) of other surveys. This portion of the spectrum offers deep mass sensitivity, especially around nearby adolescent (~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 3-5μm in preparation for JWST.

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

    SciTech Connect

    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.

  10. Achieving ultra-high temperatures with a resistive emitter array

    NASA Astrophysics Data System (ADS)

    Danielson, Tom; Franks, Greg; Holmes, Nicholas; LaVeigne, Joe; Matis, Greg; McHugh, Steve; Norton, Dennis; Vengel, Tony; Lannon, John; Goodwin, Scott

    2016-05-01

    The rapid development of very-large format infrared detector arrays has challenged the IR scene projector community to also develop larger-format infrared emitter arrays to support the testing of systems incorporating these detectors. In addition to larger formats, many scene projector users require much higher simulated temperatures than can be generated with current technology in order to fully evaluate the performance of their systems and associated processing algorithms. Under the Ultra High Temperature (UHT) development program, Santa Barbara Infrared Inc. (SBIR) is developing a new infrared scene projector architecture capable of producing both very large format (>1024 x 1024) resistive emitter arrays and improved emitter pixel technology capable of simulating very high apparent temperatures. During earlier phases of the program, SBIR demonstrated materials with MWIR apparent temperatures in excess of 1400 K. New emitter materials have subsequently been selected to produce pixels that achieve even higher apparent temperatures. Test results from pixels fabricated using the new material set will be presented and discussed. A 'scalable' Read In Integrated Circuit (RIIC) is also being developed under the same UHT program to drive the high temperature pixels. This RIIC will utilize through-silicon via (TSV) and Quilt Packaging (QP) technologies to allow seamless tiling of multiple chips to fabricate very large arrays, and thus overcome the yield limitations inherent in large-scale integrated circuits. Results of design verification testing of the completed RIIC will be presented and discussed.

  11. Experimental Realisation of High-sensitivity Laboratory X-ray Grating-based Phase-contrast Computed Tomography

    NASA Astrophysics Data System (ADS)

    Birnbacher, Lorenz; Willner, Marian; Velroyen, Astrid; Marschner, Mathias; Hipp, Alexander; Meiser, Jan; Koch, Frieder; Schröter, Tobias; Kunka, Danays; Mohr, Jürgen; Pfeiffer, Franz; Herzen, Julia

    2016-04-01

    The possibility to perform high-sensitivity X-ray phase-contrast imaging with laboratory grating-based phase-contrast computed tomography (gbPC-CT) setups is of great interest for a broad range of high-resolution biomedical applications. However, achieving high sensitivity with laboratory gbPC-CT setups still poses a challenge because several factors such as the reduced flux, the polychromaticity of the spectrum, and the limited coherence of the X-ray source reduce the performance of laboratory gbPC-CT in comparison to gbPC-CT at synchrotron facilities. In this work, we present our laboratory X-ray Talbot-Lau interferometry setup operating at 40 kVp and describe how we achieve the high sensitivity yet unrivalled by any other laboratory X-ray phase-contrast technique. We provide the angular sensitivity expressed via the minimum resolvable refraction angle both in theory and experiment, and compare our data with other differential phase-contrast setups. Furthermore, we show that the good stability of our high-sensitivity setup allows for tomographic scans, by which even the electron density can be retrieved quantitatively as has been demonstrated in several preclinical studies.

  12. Experimental Realisation of High-sensitivity Laboratory X-ray Grating-based Phase-contrast Computed Tomography

    PubMed Central

    Birnbacher, Lorenz; Willner, Marian; Velroyen, Astrid; Marschner, Mathias; Hipp, Alexander; Meiser, Jan; Koch, Frieder; Schröter, Tobias; Kunka, Danays; Mohr, Jürgen; Pfeiffer, Franz; Herzen, Julia

    2016-01-01

    The possibility to perform high-sensitivity X-ray phase-contrast imaging with laboratory grating-based phase-contrast computed tomography (gbPC-CT) setups is of great interest for a broad range of high-resolution biomedical applications. However, achieving high sensitivity with laboratory gbPC-CT setups still poses a challenge because several factors such as the reduced flux, the polychromaticity of the spectrum, and the limited coherence of the X-ray source reduce the performance of laboratory gbPC-CT in comparison to gbPC-CT at synchrotron facilities. In this work, we present our laboratory X-ray Talbot-Lau interferometry setup operating at 40 kVp and describe how we achieve the high sensitivity yet unrivalled by any other laboratory X-ray phase-contrast technique. We provide the angular sensitivity expressed via the minimum resolvable refraction angle both in theory and experiment, and compare our data with other differential phase-contrast setups. Furthermore, we show that the good stability of our high-sensitivity setup allows for tomographic scans, by which even the electron density can be retrieved quantitatively as has been demonstrated in several preclinical studies. PMID:27040492

  13. How to achieve high-level expression of microbial enzymes

    PubMed Central

    Liu, Long; Yang, Haiquan; Shin, Hyun-dong; Chen, Rachel R.; Li, Jianghua; Du, Guocheng; Chen, Jian

    2013-01-01

    Microbial enzymes have been used in a large number of fields, such as chemical, agricultural and biopharmaceutical industries. The enzyme production rate and yield are the main factors to consider when choosing the appropriate expression system for the production of recombinant proteins. Recombinant enzymes have been expressed in bacteria (e.g., Escherichia coli, Bacillus and lactic acid bacteria), filamentous fungi (e.g., Aspergillus) and yeasts (e.g., Pichia pastoris). The favorable and very advantageous characteristics of these species have resulted in an increasing number of biotechnological applications. Bacterial hosts (e.g., E. coli) can be used to quickly and easily overexpress recombinant enzymes; however, bacterial systems cannot express very large proteins and proteins that require post-translational modifications. The main bacterial expression hosts, with the exception of lactic acid bacteria and filamentous fungi, can produce several toxins which are not compatible with the expression of recombinant enzymes in food and drugs. However, due to the multiplicity of the physiological impacts arising from high-level expression of genes encoding the enzymes and expression hosts, the goal of overproduction can hardly be achieved, and therefore, the yield of recombinant enzymes is limited. In this review, the recent strategies used for the high-level expression of microbial enzymes in the hosts mentioned above are summarized and the prospects are also discussed. We hope this review will contribute to the development of the enzyme-related research field. PMID:23686280

  14. An Assessment of Science Achievement of Five- and Six-Year Old Students of Contrasting Socio-Economic Backgrounds.

    ERIC Educational Resources Information Center

    McGlathery, Glenn Edward

    Assessed was the science achievement of five-and six-year-olds from different socioeconomic backgrounds. Classes included both a middle-class and lower-class pre-school class and a middle-class and a lower-class first grade class. Four additional classes, which were studying a local science curriculum, were chosen to match these same grade-level…

  15. Sequential Prediction of Literacy Achievement for Specific Learning Disabilities Contrasting in Impaired Levels of Language in Grades 4 to 9.

    PubMed

    Sanders, Elizabeth A; Berninger, Virginia W; Abbott, Robert D

    2017-02-01

    Sequential regression was used to evaluate whether language-related working memory components uniquely predict reading and writing achievement beyond cognitive-linguistic translation for students in Grades 4 through 9 ( N = 103) with specific learning disabilities (SLDs) in subword handwriting (dysgraphia, n = 25), word reading and spelling (dyslexia, n = 60), or oral and written language (oral and written language learning disabilities, n = 18). That is, SLDs are defined on the basis of cascading level of language impairment (subword, word, and syntax/text). A five-block regression model sequentially predicted literacy achievement from cognitive-linguistic translation (Block 1); working memory components for word-form coding (Block 2), phonological and orthographic loops (Block 3), and supervisory focused or switching attention (Block 4); and SLD groups (Block 5). Results showed that cognitive-linguistic translation explained an average of 27% and 15% of the variance in reading and writing achievement, respectively, but working memory components explained an additional 39% and 27% of variance. Orthographic word-form coding uniquely predicted nearly every measure, whereas attention switching uniquely predicted only reading. Finally, differences in reading and writing persisted between dyslexia and dysgraphia, with dysgraphia higher, even after controlling for Block 1 to 4 predictors. Differences in literacy achievement between students with dyslexia and oral and written language learning disabilities were largely explained by the Block 1 predictors. Applications to identifying and teaching students with these SLDs are discussed.

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

    PubMed

    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.

  17. High-performance dendritic contrast agents for X-ray computed tomography imaging using potent tetraiodobenzene derivatives.

    PubMed

    You, Suyeon; Jung, Hye-Youn; Lee, Chaewoon; Choe, Yun Hui; Heo, Ju Young; Gang, Gil-Tae; Byun, Sang-Kyung; Kim, Won Kon; Lee, Chul-Ho; Kim, Dong-Eog; Kim, Young Il; Kim, Yoonkyung

    2016-03-28

    The use of computed tomography (CT) for vascular imaging is critical in medical emergencies requiring urgent diagnostic decisions, such as cerebral ischemia and many cardiovascular diseases. Small-molecule iodinated contrast media are often injected intravenously as radiopaque agents during CT imaging to achieve high contrast enhancement of vascular systems. The rapid excretion rate of these agents is overcome by injecting a significantly high dose of iodine, which can have serious side effects. Here we report a simple method to prepare blood-pool contrast agents for CT based on dendrimers for the first time using tetraiodobenzene derivatives as potent radiopaque moieties. Excellent in vivo safety has been demonstrated for these small (13-22nm) unimolecular water-soluble dendritic contrast agents, which exhibit high contrast enhancement in the blood-pool and effectively extend their blood half-lives. Our method is applicable to virtually any scaffold with suitable surface groups and may fulfill the current need for safer, next-generation iodinated CT contrast agents.

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

    PubMed

    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.

  19. Effects of Partner's Ability on the Achievement and Conceptual Organization of High-Achieving Fifth-Grade Students.

    ERIC Educational Resources Information Center

    Carter, Glenda; Jones, M. Gail; Rua, Melissa

    2003-01-01

    Investigates high-achieving fifth-grade students' achievement gains and conceptual reorganization on convection. Features an instructional sequence of three dyadic inquiry investigations related to convection currents as well as pre- and post-assessment consisting of a multiple-choice test, a card sorting task, construction of a concept map, and…

  20. Comparison of the Level of Using Metacognitive Strategies during Study between High Achieving and Low Achieving Prospective Teachers

    ERIC Educational Resources Information Center

    Doganay, Ahmet; Demir, Ozden

    2011-01-01

    The main purpose of this study is to compare the level of using metacognitive strategies during study between high achieving and low achieving prospective classroom teachers. This study was designed as a mixed method study. Metacognitive Learning Strategies Scale developed by Namlu (2004) was used to measure the use of metacognitive strategies…

  1. Exploring Planetary System Evolution Through High-Contrast Imaging

    NASA Astrophysics Data System (ADS)

    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

  2. Variance of high contrast textures is sensed using negative half-wave rectification.

    PubMed

    Chubb, C; Nam, J H

    2000-01-01

    A rectifying transformation is required to sense variations in texture contrast. Various theoretical and practical considerations have inclined researchers to suppose that this rectification is full-wave, rather than half-wave. In the studies reported here, observers are asked to judge which of two texture patches has higher texture variance. Textures are composed of small squares, with each square being painted with one of nine different luminances. Different texture variances are achieved by manipulating the histograms of the texture patches to be compared. When the nine luminances range linearly from 0 to 160 cd/m(2), the transformation mediating judgments of texture variance takes the form of a negative half-wave rectifier: texture variance judgments are determined exclusively by the frequencies of luminances below mean luminance in the textures being compared. However, when the nine luminances range linearly from 60 to 100 cd/m(2), two of three observers use a full-wave rectifying transformation in making texture variance judgments; the third observer continued to use a negative half-wave rectifier. The unexpectedly asymmetric roles played by low versus high luminances in texture variance judgments suggest that the off-center system may play a dominant role in human perception of texture contrast.

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

    NASA Astrophysics Data System (ADS)

    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 (<10 Myr) stars, which often harbor protoplanetary disks where planets may be forming. We achieve a typical contrast of ∼10‑4–10‑5.5 at an angular distance of 1″ from the central star, corresponding to typical mass sensitivities (assuming hot-start evolutionary models) of ∼10 M J at 70 au and ∼6 M J at 140 au. We detected a new 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 probe 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. Our sample and the associated observational results will help enable detailed statistical analyses of giant planet formation.

  4. High-contrast multilayer imaging of biological organisms through dark-field digital refocusing

    NASA Astrophysics Data System (ADS)

    Faridian, Ahmad; Pedrini, Giancarlo; Osten, Wolfgang

    2013-08-01

    We have developed an imaging system to extract high contrast images from different layers of biological organisms. Utilizing a digital holographic approach, the system works without scanning through layers of the specimen. In dark-field illumination, scattered light has the main contribution in image formation, but in the case of coherent illumination, this creates a strong speckle noise that reduces the image quality. To remove this restriction, the specimen has been illuminated with various speckle-fields and a hologram has been recorded for each speckle-field. Each hologram has been analyzed separately and the corresponding intensity image has been reconstructed. The final image has been derived by averaging over the reconstructed images. A correlation approach has been utilized to determine the number of speckle-fields required to achieve a desired contrast and image quality. The reconstructed intensity images in different object layers are shown for different sea urchin larvae. Two multimedia files are attached to illustrate the process of digital focusing.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Pair-Wise, Deformable Mirror, Image Plane-Based Diversity Electric Field Estimation for High Contrast Coronagraphy

    NASA Technical Reports Server (NTRS)

    Give'on, Amir; Kern, Brian D.; Shaklan, Stuart

    2011-01-01

    In this paper we describe the complex electric field reconstruction from image plane intensity measurements for high contrast coronagraphic imaging. A deformable mirror (DM) surface is modied with pairs of complementary shapes to create diversity in the image plane of the science camera where the intensity of the light is measured. Along with the Electric Field Conjugation correction algorithm, this estimation method has been used in various high contrast imaging testbeds to achieve the best contrasts to date both in narrow and in broad band light. We present the basic methodology of estimation in easy to follow list of steps, present results from HCIT and raise several open quations we are confronted with using this method.

  7. High-resolution short-exposure small-animal laboratory x-ray phase-contrast tomography

    PubMed Central

    Larsson, Daniel H.; Vågberg, William; Yaroshenko, Andre; Yildirim, Ali Önder; Hertz, Hans M.

    2016-01-01

    X-ray computed tomography of small animals and their organs is an essential tool in basic and preclinical biomedical research. In both phase-contrast and absorption tomography high spatial resolution and short exposure times are of key importance. However, the observable spatial resolutions and achievable exposure times are presently limited by system parameters rather than more fundamental constraints like, e.g., dose. Here we demonstrate laboratory tomography with few-ten μm spatial resolution and few-minute exposure time at an acceptable dose for small-animal imaging, both with absorption contrast and phase contrast. The method relies on a magnifying imaging scheme in combination with a high-power small-spot liquid-metal-jet electron-impact source. The tomographic imaging is demonstrated on intact mouse, phantoms and excised lungs, both healthy and with pulmonary emphysema. PMID:27958376

  8. High-resolution short-exposure small-animal laboratory x-ray phase-contrast tomography

    NASA Astrophysics Data System (ADS)

    Larsson, Daniel H.; Vågberg, William; Yaroshenko, Andre; Yildirim, Ali Önder; Hertz, Hans M.

    2016-12-01

    X-ray computed tomography of small animals and their organs is an essential tool in basic and preclinical biomedical research. In both phase-contrast and absorption tomography high spatial resolution and short exposure times are of key importance. However, the observable spatial resolutions and achievable exposure times are presently limited by system parameters rather than more fundamental constraints like, e.g., dose. Here we demonstrate laboratory tomography with few-ten μm spatial resolution and few-minute exposure time at an acceptable dose for small-animal imaging, both with absorption contrast and phase contrast. The method relies on a magnifying imaging scheme in combination with a high-power small-spot liquid-metal-jet electron-impact source. The tomographic imaging is demonstrated on intact mouse, phantoms and excised lungs, both healthy and with pulmonary emphysema.

  9. Achieving High Throughput for Data Transfer over ATM Networks

    NASA Technical Reports Server (NTRS)

    Johnson, Marjory J.; Townsend, Jeffrey N.

    1996-01-01

    File-transfer rates for ftp are often reported to be relatively slow, compared to the raw bandwidth available in emerging gigabit networks. While a major bottleneck is disk I/O, protocol issues impact performance as well. Ftp was developed and optimized for use over the TCP/IP protocol stack of the Internet. However, TCP has been shown to run inefficiently over ATM. In an effort to maximize network throughput, data-transfer protocols can be developed to run over UDP or directly over IP, rather than over TCP. If error-free transmission is required, techniques for achieving reliable transmission can be included as part of the transfer protocol. However, selected image-processing applications can tolerate a low level of errors in images that are transmitted over a network. In this paper we report on experimental work to develop a high-throughput protocol for unreliable data transfer over ATM networks. We attempt to maximize throughput by keeping the communications pipe full, but still keep packet loss under five percent. We use the Bay Area Gigabit Network Testbed as our experimental platform.

  10. Does Recreational Computer Use Affect High School Achievement?

    ERIC Educational Resources Information Center

    Bowers, Alex J.; Berland, Matthew

    2013-01-01

    Historically, the relationship between student academic achievement and use of computers for fun and video gaming has been described from a multitude of perspectives, from positive, to negative, to neutral. However, recent research has indicated that computer use and video gaming may be positively associated with achievement, yet these studies…

  11. Student Perception of Academic Achievement Factors at High School

    ERIC Educational Resources Information Center

    Bahar, Mustafa

    2016-01-01

    Measuring the quality of the "product" is elemental in education, and most studies depend on observational data about student achievement factors, focusing overwhelmingly on quantitative data namely achievement scores, school data like attendance, facilities, expenditure class size, etc. But there is little evidence of learner…

  12. High-Achieving High School Students and Not so High-Achieving College Students: A Look at Lack of Self-Control, Academic Ability, and Performance in College

    ERIC Educational Resources Information Center

    Honken, Nora B.; Ralston, Patricia A. S.

    2013-01-01

    This study investigated the relationship among lack of self-control, academic ability, and academic performance for a cohort of freshman engineering students who were, with a few exceptions, extremely high achievers in high school. Structural equation modeling analysis led to the conclusion that lack of self-control in high school, as measured by…

  13. Frustrated FRET for high-contrast high-resolution two-photon imaging.

    PubMed

    Xu, Fang; Wei, Lu; Chen, Zhixing; Min, Wei

    2013-06-17

    Two-photon fluorescence microscopy has become increasingly popular in biomedical research as it allows high-resolution imaging of thick biological specimen with superior contrast and penetration than confocal microscopy. However, two-photon microscopy still faces two fundamental limitations: 1) image-contrast deterioration with imaging depth due to out-of-focus background and 2) diffraction-limited spatial resolution. Herein we propose to create and detect high-order (more than quadratic) nonlinear signals by harnessing the frustrated fluorescence resonance energy transfer (FRET) effect within a specially designed donor-acceptor probe pair. Two distinct techniques are described. In the first method, donor fluorescence generated by a two-photon laser at the focus is preferentially switched on and off by a modulated and focused one-photon laser beam that is able to block FRET via direct acceptor excitation. The resulting image, constructed from the enhanced donor fluorescence signal, turns out to be an overall three-photon process. In the second method, a two-photon laser at a proper wavelength is capable of simultaneously exciting both the donor and the acceptor. By sinusoidally modulating the two-photon excitation laser at a fundamental frequency ω, an overall four-photon signal can be isolated by demodulating the donor fluorescence at the third harmonic frequency 3ω. We show that both the image contrast and the spatial resolution of the standard two-photon fluorescence microscopy can be substantially improved by virtue of the high-order nonlinearity. This frustrated FRET approach represents a strategy that is based on extracting the inherent nonlinear photophysical response of the specially designed imaging probes.

  14. Compact high-resolution differential interference contrast soft x-ray microscopy

    SciTech Connect

    Bertilson, Michael C.; Hofsten, Olov von; Lindblom, Magnus; Hertz, Hans M.; Vogt, Ulrich

    2008-02-11

    We demonstrate high-resolution x-ray differential interference contrast (DIC) in a compact soft x-ray microscope. Phase contrast imaging is enabled by the use of a diffractive optical element objective which is matched to the coherence conditions in the microscope setup. The performance of the diffractive optical element objective is evaluated in comparison with a normal zone plate by imaging of a nickel siemens star pattern and linear grating test objects. Images obtained with the DIC optic exhibit typical DIC enhancement in addition to the normal absorption contrast. Contrast transfer functions based on modulation measurements in the obtained images show that the DIC optic gives a significant increase in contrast without reducing the spatial resolution. The phase contrast operation mode now available for our compact soft x-ray microscope will be a useful tool for future studies of samples with low absorption contrast.

  15. High Contrast.

    ERIC Educational Resources Information Center

    Greenman, Geri

    2002-01-01

    Presents an art lesson in which drawing students learn to use scratchboard to create a picture of a skeleton part that they find interesting. Describes how the students create pictures using this technique. Includes a list of materials and objectives. (CMK)

  16. Combining high-dispersion spectroscopy with high contrast imaging: Probing rocky planets around our nearest neighbors

    NASA Astrophysics Data System (ADS)

    Snellen, I.; de Kok, R.; Birkby, J. L.; Brandl, B.; Brogi, M.; Keller, C.; Kenworthy, M.; Schwarz, H.; Stuik, R.

    2015-04-01

    Context. Ground-based high-dispersion (R ~ 100 000) spectroscopy (HDS) is proving to be a powerful technique with which to characterize extrasolar planets. The planet signal is distilled from the bright starlight, combining ral and time-differential filtering techniques. In parallel, high-contrast imaging (HCI) is developing rapidly, aimed at spatially separating the planet from the star. While HDS is limited by the overwhelming noise from the host star, HCI is limited by residual quasi-static speckles. Both techniques currently reach planet-star contrast limits down to ~10-5, albeit for very different types of planetary systems. Aims: In this work, we discuss a way to combine HDS and HCI (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 ~10-5 × 10-5, although in practice this will be limited by photon noise and/or sky-background. In contrast to current direct imaging techniques, such as Angular Differential Imaging and Spectral Differential Imaging, it will work well at small working angles and is much less sensitive to speckle noise. For the discovery of previously unknown planets HDS+HCI requires a high-contrast adaptive optics system combined with a high-dispersion R ~ 100 000 integral field spectrograph (IFS). This combination currently does not exist, but is planned for the European Extremely Large Telescope. 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

  17. Threatened and Placed at Risk: High Achieving African American Males in Urban High Schools

    ERIC Educational Resources Information Center

    McGee, Ebony O.

    2013-01-01

    This study investigated the risk and protective factors of 11 high-achieving African American males attending 4 urban charter high schools in a Midwestern city to determine what factors account for their resilience and success in mathematics courses, and in high school more generally. This research was guided by a Phenomenological Variant of…

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

    PubMed

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

    2017-01-30

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

  19. End-to-end simulation of high-contrast imaging systems: methods and results for the PICTURE mission family

    NASA Astrophysics Data System (ADS)

    Douglas, Ewan S.; Hewasawam, Kuravi; Mendillo, Christopher B.; Cahoy, Kerri L.; Cook, Timothy A.; Finn, Susanna C.; Howe, Glenn A.; Kuchner, Marc J.; Lewis, Nikole K.; Marinan, Anne D.; Mawet, Dimitri; Chakrabarti, Supriya

    2015-09-01

    We describe a set of numerical approaches to modeling the performance of space flight high-contrast imaging payloads. Mission design for high-contrast imaging requires numerical wavefront error propagation to ensure accurate component specifications. For constructed instruments, wavelength and angle-dependent throughput and contrast models allow detailed simulations of science observations, allowing mission planners to select the most productive science targets. The PICTURE family of missions seek to quantify the optical brightness of scattered light from extrasolar debris disks via several high-contrast imaging techniques: sounding rocket (the Planet Imaging Concept Testbed Using a Rocket Experiment) and balloon flights of a visible nulling coronagraph, as well as a balloon flight of a vector vortex coronagraph (the Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph, PICTURE-C). The rocket mission employs an on-axis 0.5m Gregorian telescope, while the balloon flights will share an unobstructed off-axis 0.6m Gregorian. This work details the flexible approach to polychromatic, end-to-end physical optics simulations used for both the balloon vector vortex coronagraph and rocket visible nulling coronagraph missions. We show the preliminary PICTURE-C telescope and vector vortex coronagraph design will achieve 10-8 contrast without post-processing as limited by realistic optics, but not considering polarization or low-order errors. Simulated science observations of the predicted warm ring around Epsilon Eridani illustrate the performance of both missions.

  20. The Effect of Music Participation on Mathematical Achievement and Overall Academic Achievement of High School Students

    ERIC Educational Resources Information Center

    Cox, H. A.; Stephens, L. J.

    2006-01-01

    A study was conducted on high school students, comparing those with some music credits to those with none. No statistically significant difference was found in their mean math grade point averages (GPA) or their mean cumulative GPAs. Students were then separated into two groups based on the number of music credits. Students who had earned at least…

  1. Pushing the limits of high contrast with STIS/BAR5

    NASA Astrophysics Data System (ADS)

    Debes, John H.; Ren, Bin

    2017-01-01

    The Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) contains the only currently operating coronagraph in space that is not trained on the sun. We demonstrate the high contrast capabilities of the newly commissioned BAR5 occulter. We discuss the latest procedures in obtaining high contrast imaging of circumstellar disks and faint point sources with STIS and present results from a recent calibration program that demonstrates better than 10-6 point-source contrast at sub-arcsecond inner working angles, and better than 10-5 point-source contrast beyond 0.25‧‧. These results are obtained by a combination of sub-pixel grid dithers, multiple spacecraft orientations, and post-processing. Some of these same techniques will be employed by future coronagraphic missions. We present sample science cases for high contrast imaging in the visible with these newly demonstrated capabilities.

  2. Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions

    NASA Astrophysics Data System (ADS)

    Rymaruk, Matthew J.; Thompson, Kate L.; Derry, Matthew J.; Warren, Nicholas J.; Ratcliffe, Liam P. D.; Williams, Clive N.; Brown, Steven L.; Armes, Steven P.

    2016-07-01

    We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral

  3. Academic attainment and the high school science experiences among high-achieving African American males

    NASA Astrophysics Data System (ADS)

    Trice, Rodney Nathaniel

    This study examines the educational experiences of high achieving African American males. More specifically, it analyzes the influences on their successful navigation through high school science. Through a series of interviews, observations, questionnaires, science portfolios, and review of existing data the researcher attempted to obtain a deeper understanding of high achieving African American males and their limitations to academic attainment and high school science experiences. The investigation is limited to ten high achieving African American male science students at Woodcrest High School. Woodcrest is situated at the cross section of a suburban and rural community located in the southeastern section of the United States. Although this investigation involves African American males, all of whom are successful in school, its findings should not be generalized to this nor any other group of students. The research question that guided this study is: What are the limitations to academic attainment and the high school science experiences of high achieving African American males? The student participants expose how suspension and expulsion, special education placement, academic tracking, science instruction, and teacher expectation influence academic achievement. The role parents play, student self-concept, peer relationships, and student learning styles are also analyzed. The anthology of data rendered three overarching themes: (1) unequal access to education, (2) maintenance of unfair educational structures, and (3) authentic characterizations of African American males. Often the policies and practices set in place by school officials aid in creating hurdles to academic achievement. These policies and practices are often formed without meaningful consideration of the unintended consequences that may affect different student populations, particularly the most vulnerable. The findings from this study expose that high achieving African American males face major

  4. Dominant Achievement Goals across Tracks in High School

    ERIC Educational Resources Information Center

    Scheltinga, Peter A. M.; Kuyper, Hans; Timmermans, Anneke C.; van der Werf, Greetje P. C.

    2016-01-01

    The dominant achievement goals (DAGs) of 7,008 students in the third grade of Dutch secondary education (US grade 9) were investigated, based on Elliot & McGregors' 2 × 2 framework (2001), in relation to track-level and motivational variables. We found the mastery-approach goal and the performance-approach goal, generally considered adaptive,…

  5. Charter High Schools: Closing the Achievement Gap. Innovations in Education

    ERIC Educational Resources Information Center

    US Department of Education, 2006

    2006-01-01

    The eight schools profiled in this document are serving different populations, but all of them are closing the achievement gap between low-income, minority, and special needs students and their peers. By trying out innovative new strategies, these schools are blazing a trail for others to follow. They are dispelling the myth that some students can…

  6. "Brains before "Beauty"?" High Achieving Girls, School and Gender Identities

    ERIC Educational Resources Information Center

    Skelton, Christine; Francis, Becky; Read, Barbara

    2010-01-01

    In recent years educational policy on gender and achievement has concentrated on boys' underachievement, frequently comparing it with the academic success of girls. This has encouraged a perception of girls as the "winners" of the educational stakes and assumes that they no longer experience the kinds of gender inequalities identified in…

  7. Bespoke contrast-matched diblock copolymer nanoparticles enable the rational design of highly transparent Pickering double emulsions.

    PubMed

    Rymaruk, Matthew J; Thompson, Kate L; Derry, Matthew J; Warren, Nicholas J; Ratcliffe, Liam P D; Williams, Clive N; Brown, Steven L; Armes, Steven P

    2016-08-14

    We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 μm diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Parenting Style, Perfectionism, and Creativity in High-Ability and High-Achieving Young Adults

    ERIC Educational Resources Information Center

    Miller, Angie L.; Lambert, Amber D.; Speirs Neumeister, Kristie L.

    2012-01-01

    The current study explores the potential relationships among perceived parenting style, perfectionism, and creativity in a high-ability and high-achieving young adult population. Using data from 323 honors college students at a Midwestern university, bivariate correlations suggested positive relationships between (a) permissive parenting style and…

  10. Success Despite Socioeconomics: A Case Study of a High-Achieving, High-Poverty School

    ERIC Educational Resources Information Center

    Tilley, Thomas Brent; Smith, Samuel J.; Claxton, Russell L.

    2012-01-01

    This case study of a high-achieving, high-poverty school describes the school's leadership, culture, and programs that contributed to its success. Data were collected from two surveys (the School Culture Survey and the Vanderbilt Assessment of Leadership in Education), observations at the school site, and interviews with school personnel. The…

  11. High-Resolution Ultrasound-Switchable Fluorescence Imaging in Centimeter-Deep Tissue Phantoms with High Signal-To-Noise Ratio and High Sensitivity via Novel Contrast Agents

    PubMed Central

    Cheng, Bingbing; Bandi, Venugopal; Wei, Ming-Yuan; Pei, Yanbo; D’Souza, Francis; Nguyen, Kytai T.; Hong, Yi; Yuan, Baohong

    2016-01-01

    For many years, investigators have sought after high-resolution fluorescence imaging in centimeter-deep tissue because many interesting in vivo phenomena—such as the presence of immune system cells, tumor angiogenesis, and metastasis—may be located deep in tissue. Previously, we developed a new imaging technique to achieve high spatial resolution in sub-centimeter deep tissue phantoms named continuous-wave ultrasound-switchable fluorescence (CW-USF). The principle is to use a focused ultrasound wave to externally and locally switch on and off the fluorophore emission from a small volume (close to ultrasound focal volume). By making improvements in three aspects of this technique: excellent near-infrared USF contrast agents, a sensitive frequency-domain USF imaging system, and an effective signal processing algorithm, for the first time this study has achieved high spatial resolution (~ 900 μm) in 3-centimeter-deep tissue phantoms with high signal-to-noise ratio (SNR) and high sensitivity (3.4 picomoles of fluorophore in a volume of 68 nanoliters can be detected). We have achieved these results in both tissue-mimic phantoms and porcine muscle tissues. We have also demonstrated multi-color USF to image and distinguish two fluorophores with different wavelengths, which might be very useful for simultaneously imaging of multiple targets and observing their interactions in the future. This work has opened the door for future studies of high-resolution centimeter-deep tissue fluorescence imaging. PMID:27829050

  12. Simultaneous high-resolution scanning Bragg contrast and ptychographic imaging of a single solar cell nanowire

    PubMed Central

    Wallentin, Jesper; Wilke, Robin N.; Osterhoff, Markus; Salditt, Tim

    2015-01-01

    Simultaneous scanning Bragg contrast and small-angle ptychographic imaging of a single solar cell nanowire are demonstrated, using a nanofocused hard X-ray beam and two detectors. The 2.5 µm-long nanowire consists of a single-crystal InP core of 190 nm diameter, coated with amorphous SiO2 and polycrystalline indium tin oxide. The nanowire was selected and aligned in real space using the small-angle scattering of the 140 × 210 nm X-ray beam. The orientation of the nanowire, as observed in small-angle scattering, was used to find the correct rotation for the Bragg condition. After alignment in real space and rotation, high-resolution (50 nm step) raster scans were performed to simultaneously measure the distribution of small-angle scattering and Bragg diffraction in the nanowire. Ptychographic reconstruction of the coherent small-angle scattering was used to achieve sub-beam spatial resolution. The small-angle scattering images, which are sensitive to the shape and the electron density of all parts of the nanowire, showed a homogeneous profile along the nanowire axis except at the thicker head region. In contrast, the scanning Bragg diffraction microscopy, which probes only the single-crystal InP core, revealed bending and crystalline inhomogeneity. Both systematic and non-systematic real-space movement of the nanowire were observed as it was rotated, which would have been difficult to reveal only from the Bragg scattering. These results demonstrate the advantages of simultaneously collecting and analyzing the small-angle scattering in Bragg diffraction experiments. PMID:26664342

  13. Simultaneous high-resolution scanning Bragg contrast and ptychographic imaging of a single solar cell nanowire.

    PubMed

    Wallentin, Jesper; Wilke, Robin N; Osterhoff, Markus; Salditt, Tim

    2015-12-01

    Simultaneous scanning Bragg contrast and small-angle ptychographic imaging of a single solar cell nanowire are demonstrated, using a nanofocused hard X-ray beam and two detectors. The 2.5 µm-long nanowire consists of a single-crystal InP core of 190 nm diameter, coated with amorphous SiO2 and polycrystalline indium tin oxide. The nanowire was selected and aligned in real space using the small-angle scattering of the 140 × 210 nm X-ray beam. The orientation of the nanowire, as observed in small-angle scattering, was used to find the correct rotation for the Bragg condition. After alignment in real space and rotation, high-resolution (50 nm step) raster scans were performed to simultaneously measure the distribution of small-angle scattering and Bragg diffraction in the nanowire. Ptychographic reconstruction of the coherent small-angle scattering was used to achieve sub-beam spatial resolution. The small-angle scattering images, which are sensitive to the shape and the electron density of all parts of the nanowire, showed a homogeneous profile along the nanowire axis except at the thicker head region. In contrast, the scanning Bragg diffraction microscopy, which probes only the single-crystal InP core, revealed bending and crystalline inhomogeneity. Both systematic and non-systematic real-space movement of the nanowire were observed as it was rotated, which would have been difficult to reveal only from the Bragg scattering. These results demonstrate the advantages of simultaneously collecting and analyzing the small-angle scattering in Bragg diffraction experiments.

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

    SciTech Connect

    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.

  15. Highly photostable, reversibly photoswitchable fluorescent protein with high contrast ratio for live-cell superresolution microscopy

    PubMed Central

    Zhang, Xi; Zhang, Mingshu; Li, Dong; He, Wenting; Peng, Jianxin; Betzig, Eric; Xu, Pingyong

    2016-01-01

    Two long-standing problems for superresolution (SR) fluorescence microscopy are high illumination intensity and long acquisition time, which significantly hamper its application for live-cell imaging. Reversibly photoswitchable fluorescent proteins (RSFPs) have made it possible to dramatically lower the illumination intensities in saturated depletion-based SR techniques, such as saturated depletion nonlinear structured illumination microscopy (NL-SIM) and reversible saturable optical fluorescence transition microscopy. The characteristics of RSFPs most critical for SR live-cell imaging include, first, the integrated fluorescence signal across each switching cycle, which depends upon the absorption cross-section, effective quantum yield, and characteristic switching time from the fluorescent “on” to “off” state; second, the fluorescence contrast ratio of on/off states; and third, the photostability under excitation and depletion. Up to now, the RSFPs of the Dronpa and rsEGFP (reversibly switchable EGFP) families have been exploited for SR imaging. However, their limited number of switching cycles, relatively low fluorescence signal, and poor contrast ratio under physiological conditions ultimately restrict their utility in time-lapse live-cell imaging and their ability to reach the desired resolution at a reasonable signal-to-noise ratio. Here, we present a truly monomeric RSFP, Skylan-NS, whose properties are optimized for the recently developed patterned activation NL-SIM, which enables low-intensity (∼100 W/cm2) live-cell SR imaging at ∼60-nm resolution at subsecond acquisition times for tens of time points over broad field of view. PMID:27562163

  16. The Relationship between Self-Esteem and Academic Achievement in a Group of High, Medium, and Low Secondary Public High School Achievers.

    ERIC Educational Resources Information Center

    Thomas-Brantley, Betty J.

    This study investigated the relationship between self-esteem and academic achievement in a group of 150 high, medium, and low achievers at a large midwestern public high school. Correlating data from the Coopersmith Inventory of self-esteem with grades, cumulative grade point averages, and class rank, the study disclosed a positive correlation…

  17. Estimation of chromatic errors from broadband images for high contrast imaging

    NASA Astrophysics Data System (ADS)

    Sirbu, Dan; Belikov, Ruslan

    2015-09-01

    Usage of an internal coronagraph with an adaptive optical system for wavefront correction for direct imaging of exoplanets is currently being considered for many mission concepts, including as an instrument addition to the WFIRST-AFTA mission to follow the James Web Space Telescope. The main technical challenge associated with direct imaging of exoplanets with an internal coronagraph is to effectively control both the diffraction and scattered light from the star so that the dim planetary companion can be seen. For the deformable mirror (DM) to recover a dark hole region with sufficiently high contrast in the image plane, wavefront errors are usually estimated using probes on the DM. To date, most broadband lab demonstrations use narrowband filters to estimate the chromaticity of the wavefront error, but this reduces the photon flux per filter and requires a filter system. Here, we propose a method to estimate the chromaticity of wavefront errors using only a broadband image. This is achieved by using special DM probes that have sufficient chromatic diversity. As a case example, we simulate the retrieval of the spectrum of the central wavelength from broadband images for a simple shaped- pupil coronagraph with a conjugate DM and compute the resulting estimation error.

  18. Stabilized porous liposomes with encapsulated Gd-labeled dextran as highly efficient MRI contrast agents

    PubMed Central

    Zaki, Ajlan Al; Jones, Ian W.; Hall, Henry K.; Aspinwall, Craig A; Tsourkas, Andrew

    2014-01-01

    A highly efficient contrast agent for magnetic resonance imaging was developed by encapsulating gadolinium within a stabilized porous liposome. The highly porous membrane leads to a high relaxivity of the encapsulated Gd. The stability of the liposome was improved by forming a polymer network within the bilayer membrane. PMID:24457826

  19. Comparison between high- and zero-contrast gratings as VCSEL mirrors

    NASA Astrophysics Data System (ADS)

    Liu, Anjin; Zheng, Wanhua; Bimberg, Dieter

    2017-04-01

    This study presents a comparison between high-contrast gratings (HCGs) and zero-contrast gratings (ZCGs) for high-speed vertical-cavity surface-emitting lasers (VCSELs). Both types of gratings exhibit high reflectivities beyond 99.5% due to the destructive interference at the output plane, but the HCG has a broader high reflectivity band. The HCG has a lower reflection delay time and smaller energy penetration length than the ZCG. The HCG has poorer mode selectivity for the VCSEL than the ZCG. The fabrication of the ZCG is less complex but with tight fabrication tolerances.

  20. Highly magnetic iron carbide nanoparticles as effective T2 contrast agents

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.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. Electronic supplementary information (ESI) available: Supplementary figures and experimental details. See DOI: 10.1039/c3nr04691e

  1. Relationships among Stress, Coping, and Mental Health in High-Achieving High School Students

    ERIC Educational Resources Information Center

    Suldo, Shannon M.; Shaunessy, Elizabeth; Hardesty, Robin

    2008-01-01

    This study investigates the relationships among stress, coping, and mental health in 139 students participating in an International Baccalaureate (IB) high school diploma program. Mental health was assessed using both positive indicators (life satisfaction, academic achievement, academic self-efficacy) and negative indicators (psychopathology) of…

  2. Examining Organizational Practices That Predict Persistence among High-Achieving Black Males in High School

    ERIC Educational Resources Information Center

    Anderson, Kenneth Alonzo

    2016-01-01

    Background/Context: This article summarizes an increasing trend of antideficit Black male research in mathematics and highlights opportunities to add to the research. A review of the literature shows that antideficit researchers often examine relationships between individual traits and persistence of high-achieving Black males in mathematics.…

  3. The Strengths of High-Achieving Black High School Students in a Racially Diverse Setting

    ERIC Educational Resources Information Center

    Marsh, Kris; Chaney, Cassandra; Jones, Derrick

    2012-01-01

    Robert Hill (1972) identified strengths of Black families: strong kinship bonds, strong work orientation, adaptability of family roles, high achievement orientation, and religious orientation. Some suggest these strengths sustain the physical, emotional, social, and spiritual needs of Blacks. This study used narratives and survey data from a…

  4. Relationship between High School Mathematical Achievement and Quantitative GPA

    ERIC Educational Resources Information Center

    Brown, Jennifer L.; Halpin, Glennelle; Halpin, Gerald

    2015-01-01

    The demand for STEM graduates has increased, but the number of incoming freshmen who declare a STEM major has remained stagnant. High school courses, such as calculus, can open or close the gate for students interested in careers in STEM. The purpose of this study was to determine if high school mathematics preparation was a significant…

  5. Managing the optical wavefront for high contrast exoplanet imaging with the WFIRST-AFTA coronagraph

    NASA Astrophysics Data System (ADS)

    Trauger, John T.; Krist, John E.; Moody, Dwight

    2016-01-01

    The prospect of extreme high contrast astronomical imaging from space has inspired developments of new coronagraph methods for exoplanet imaging and spectroscopy. However, the requisite contrast, at levels of a billion to one or better for the direct imaging of cool mature exoplanets in reflected visible starlight, leads to challenging new requirements on the stability and control of the optical wavefront at levels currently beyond the reach of ground based telescopes. We briefly review the designs, laboratory validations, and science prospects for direct imaging and spectroscopic characterization of exoplanet systems with an actively corrected Lyot coronagraph. We review exoplanet science performance predicted for NASA's WFIRST-AFTA coronagraph. Together with a pair of deformable mirrors for optical wavefront control, the Lyot coronagraph creates high contrast dark fields of view extending to angular separations within 0.1 arcsec from the central star at visible wavelengths. Performance metrics are presented, including image contrast and spectral bandwidth, and laboratory validation experience.

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

    PubMed

    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.

  7. Practically Perfect in Every Way: Can Reframing Perfectionism for High-Achieving Undergraduates Impact Academic Resilience?

    ERIC Educational Resources Information Center

    Dickinson, Mary J.; Dickinson, David A. G.

    2015-01-01

    This study focuses on a pan-disciplinary scheme that targeted high-achieving undergraduate students. Earlier research from the scheme argued that high achievers have discernibly different learning and personal development support needs. One of the most frequent self-reported challenges within this high-achieving group is perfectionism. This…

  8. High Achiever: A School Modernization Uncovers Hidden Potential.

    ERIC Educational Resources Information Center

    Babcock, Regina Raiford

    2003-01-01

    Describes the renovation of Lisle Senior High School in Lisle, Illinois, including the educational context and design goals. Includes information on the architects, suppliers, and construction team. Also includes the floor plan and photographs. (EV)

  9. High accuracy and contrast resolution in ultra-low field magnetic resonance imaging.

    PubMed

    Agartz, I; Sääf, J; Wahlund, B; Wahlund, L O; Wetterberg, L

    1986-01-01

    Magnetic resonance imaging (MRI) at low magnetic field strengths is known to have a comparatively high contrast resolution. Current techniques increasing the signal to noise ratio 3 to 4 times allow for an improvement in the spatial resolution still maintaining the high contrast resolution. The contributing features to this advancement are improvements in software, development of new radiofrequency coils and image processing computors. The subsequent improvement in image evaluation and the access to added information make for a high accuracy in clinical diagnosis and research. The present potential of imaging at ultra-low (0.02 tesla) magnetic field strengths is illustrated with examples from clinical practice and research.

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

    NASA Astrophysics Data System (ADS)

    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).

  11. Gender, Student Motivation and Academic Achievement in a Midsized Wisconsin High School

    ERIC Educational Resources Information Center

    Lutzke, Steven Ronald

    2013-01-01

    This mixed-methods study investigated relationships among gender, academic motivation and achievement in a mid-sized Wisconsin high school. A questionnaire was developed that focused on perceived ability, achievement motives and achievement goals. Interviews with teachers focused on relationships among academic motivation and gender achievement.…

  12. Student Achievement Data Systems in High and Low Performing Schools

    ERIC Educational Resources Information Center

    Stachowiak, Jeannie E.

    2013-01-01

    The purpose of this study was to determine if there was a difference in how high and low performing elementary school districts use and analyze data to differentiate instruction, make changes to district/grade level curriculum, determine professional development needs, determine teacher effectiveness, and determine the use of school district…

  13. Behaviour and achievement disorders in children with high intelligence.

    PubMed

    Barchmann, H; Kinze, W

    1990-01-01

    With 6% of the patients of a childpsychiatric population using treatment a high intelligence with an IQ of over 120 was the result. This is in agreement with the results by Reinhard (1981), but is below the results by Schmidt (1977) and justifies neither the association to a higher talent as risk factor nor as protective factor in view of a potential psychic illness. 341 child-neuropsychiatric patients with hyperkinetic syndrome (55%), Enuresis (28%), reactions of adaptation (5%), specific emotional disturbances in childhood (4%), Encopresis (3%), Psychalgy (3%) and tics (2%) were studied; thereby 22 highly intelligent patients were compared with average intelligent patients. With high intelligence better performances of concentration, more reflexive style of study, better school notes and more favourable motor capabilities, less pronounced signs of anxiety and neuroticism are found, but also a poorer social adaptation and less favourable effects of treatment. Concerning the poorer chances of treatment with high intelligence however the behaviour-therapeutic concentration of our therapy has to be pointed out, which might not offer an optimal chance for development.

  14. Organizational Citizenship of Faculty and Achievement of High School Students

    ERIC Educational Resources Information Center

    DiPaola, Michael F.; Hoy, Wayne K.

    2005-01-01

    All successful organizations, including successful high schools, have employees who go beyond their formal job responsibilities and freely give of their time and energy to succeed. Organ was the first to use the phrase "organizational citizenship behavior" (OCB) to denote organizationally beneficial behavior of workers that was not prescribed but…

  15. Common Core and America's High-Achieving Students

    ERIC Educational Resources Information Center

    Plucker, Jonathan A.

    2015-01-01

    While the merit and politics of the Common Core State Standards (CCSS) have been much debated and discussed, one topic has been virtually ignored: What do the standards portend for America's high-ability students? This brief addresses that question and provides guidance for CCSS-implementing districts and schools as they seek to help these…

  16. Syllabication Skills and Reading Achievement of High School Students.

    ERIC Educational Resources Information Center

    Curry, Robert L.; Geis, Lynna

    A sample of 175 students, constituting grades 10, 11, and 12 of two high schools, was used in the validation of a new Syllabication Skills Test. On the first day, the students completed four forms of the syllabication test; on the second, they completed Survey F of the Gates-MacGinitie Reading Tests. Means and standard deviations were similar for…

  17. Technology's Achilles Heel: Achieving High-Quality Implementation

    ERIC Educational Resources Information Center

    Hall, Gene E.

    2010-01-01

    An inherent characteristic of technology education is the continual development of new technologies and creating innovative applications of already existing technologies. As exciting as these innovations can be, technology educators and school staffs are frequently challenged to accomplish high levels of implementation. The metaphor of the…

  18. Alternative High School Scheduling. Student Achievement and Behavior. Research Report.

    ERIC Educational Resources Information Center

    Pisapia, John; Westfall, Amy Lynn

    In 1995 the Metropolitan Educational Research Consortium (MERC), Richmond (Virginia) commissioned a study of alternative high school scheduling modules to determine the effects of different schedules on teaching strategies, teacher and student satisfaction, and student and school performance. This report presents results of an analysis of student…

  19. High-Achieving Schools Put Equity Front and Center

    ERIC Educational Resources Information Center

    Gleason, Sonia Caus; Gerzon, Nancy

    2014-01-01

    How does professional learning look and feel in high-poverty schools where every student makes at least one year's worth of progress every year? How do schools and leaders put all the varied components of professional learning together so that they support all students learning every day? What professional learning grounds and sustains educators…

  20. More High-Achieving Students Are Choosing Community Colleges First

    ERIC Educational Resources Information Center

    Pluviose, David

    2008-01-01

    Certainly, "Tonight Show" host Jay Leno has nurtured the perception that community colleges are a punishment for underperforming high school students by joking that community colleges aren't "real colleges." This article shows that this perception belies the reality that contemporary community colleges serve students seeking trade skills but also…

  1. Impact of learning orientation on African American children's attitudes toward high-achieving peers.

    PubMed

    Marryshow, Derrick; Hurley, Eric A; Allen, Brenda A; Tyler, Kenneth M; Boykin, A Wade

    2005-01-01

    This study examined Ogbu's widely accepted thesis that African American students reject high academic achievement because they perceive its limited utility in a world where their upward mobility is constrained by racial discrimination. Boykin's psychosocial integrity model contends that Black students value high achievement but that discrepancies between their formative cultural experiences and those imposed in school lead them to reject the modes of achievement available in classrooms. Ninety Black children completed a measure of attitudes toward students who achieve via mainstream or African American cultural values. Participants rejected the mainstream achievers and embraced the African American cultural achievers. Moreover, they expected their teachers to embrace the mainstream achievers and reject those who achieved through high-verve behavior. Results suggest that Boykin's thesis is a needed refinement to Ogbu's ideas. They indicate that Black children may reject not high achievement but some of the mainstream cultural values and behaviors on which success in mainstream classrooms is made contingent.

  2. High-contrast fluorescence imaging based on the polarization dependence of the fluorescence enhancement using an optical interference mirror slide.

    PubMed

    Yasuda, Mitsuru; Akimoto, Takuo

    2015-01-01

    High-contrast fluorescence imaging using an optical interference mirror (OIM) slide that enhances the fluorescence from a fluorophore located on top of the OIM surface is reported. To enhance the fluorescence and reduce the background light of the OIM, transverse-electric-polarized excitation light was used as incident light, and the transverse-magnetic-polarized fluorescence signal was detected. As a result, an approximate 100-fold improvement in the signal-to-noise ratio was achieved through a 13-fold enhancement of the fluorescence signal and an 8-fold reduction of the background light.

  3. Achieving High Reliability Operations Through Multi-Program Integration

    SciTech Connect

    Holly M. Ashley; Ronald K. Farris; Robert E. Richards

    2009-04-01

    Over the last 20 years the Idaho National Laboratory (INL) has adopted a number of operations and safety-related programs which has each periodically taken its turn in the limelight. As new programs have come along there has been natural competition for resources, focus and commitment. In the last few years, the INL has made real progress in integrating all these programs and are starting to realize important synergies. Contributing to this integration are both collaborative individuals and an emerging shared vision and goal of the INL fully maturing in its high reliability operations. This goal is so powerful because the concept of high reliability operations (and the resulting organizations) is a masterful amalgam and orchestrator of the best of all the participating programs (i.e. conduct of operations, behavior based safety, human performance, voluntary protection, quality assurance, and integrated safety management). This paper is a brief recounting of the lessons learned, thus far, at the INL in bringing previously competing programs into harmony under the goal (umbrella) of seeking to perform regularly as a high reliability organization. In addition to a brief diagram-illustrated historical review, the authors will share the INL’s primary successes (things already effectively stopped or started) and the gaps yet to be bridged.

  4. Telescoping Solar Array Concept for Achieving High Packaging Efficiency

    NASA Technical Reports Server (NTRS)

    Mikulas, Martin; Pappa, Richard; Warren, Jay; Rose, Geoff

    2015-01-01

    Lightweight, high-efficiency solar arrays are required for future deep space missions using high-power Solar Electric Propulsion (SEP). Structural performance metrics for state-of-the art 30-50 kW flexible blanket arrays recently demonstrated in ground tests are approximately 40 kW/cu m packaging efficiency, 150 W/kg specific power, 0.1 Hz deployed stiffness, and 0.2 g deployed strength. Much larger arrays with up to a megawatt or more of power and improved packaging and specific power are of interest to mission planners for minimizing launch and life cycle costs of Mars exploration. A new concept referred to as the Compact Telescoping Array (CTA) with 60 kW/cu m packaging efficiency at 1 MW of power is described herein. Performance metrics as a function of array size and corresponding power level are derived analytically and validated by finite element analysis. Feasible CTA packaging and deployment approaches are also described. The CTA was developed, in part, to serve as a NASA reference solar array concept against which other proposed designs of 50-1000 kW arrays for future high-power SEP missions could be compared.

  5. High-contrast imaging through scattering media using structured illumination and Fourier filtering.

    PubMed

    Berrocal, Edouard; Pettersson, Sven-Göran; Kristensson, Elias

    2016-12-01

    We show in this Letter a novel approach for high-contrast imaging through scattering media by combining structured illumination and Fourier filtering (SIF). To assess the image contrast enhancement at different image spatial frequencies, the modulation transfer function is calculated for four detection schemes: (1) no filtering, (2) Fourier filtering, (3) structured illumination, and (4) SIF filtering. A scattering solution consisting of D=7.3  μm polystyrene spheres immersed in distilled water and illuminated at λ=671  nm is used here. We demonstrate the possibility of obtaining, with SIF, an image contrast up to 60% at an optical depth of OD=10, improving the contrast by a factor of 40 over conventional transmission imaging.

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

    PubMed Central

    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

  7. From Dropout to High Achiever: An Understanding of Academic Excellence through the Ethnography of High and Low Achieving Secondary School Students.

    ERIC Educational Resources Information Center

    Cuellar, Alfredo

    This paper, a follow-up to a previous review of literature on academic excellence that synthesized information from the United States and Mexico, describes an ethnographic study of high-achieving and low-achieving Hispanic secondary school students from Calexico, California and Mexicali, Baja California Mexico. Five students for each group were…

  8. Improved high-contrast imaging with on-axis telescopes using a multistage vortex coronagraph.

    PubMed

    Mawet, Dimitri; Serabyn, Eugene; Wallace, J Kent; Pueyo, Laurent

    2011-04-15

    The vortex coronagraph is one of the most promising coronagraphs for high-contrast imaging because of its simplicity, small inner working angle, high throughput, and clear off-axis discovery space. However, as with most coronagraphs, centrally obscured on-axis telescopes degrade contrast. Based on the remarkable ability of vortex coronagraphs to move light between the interior and exterior of pupils, we propose a method based on multiple vortices, that without sacrificing throughput, reduces the residual light leakage to (a/A)(n), with n ≥ 4, and a and A being the radii of the central obscuration and primary mirror, respectively. This method thus enables high contrasts to be reached even with an on-axis telescope.

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

    PubMed

    Yao, Yuhan; Liu, He; Wu, Wei

    2015-07-18

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

  10. Achieving high data reduction with integral cubic B-splines

    NASA Technical Reports Server (NTRS)

    Chou, Jin J.

    1993-01-01

    During geometry processing, tangent directions at the data points are frequently readily available from the computation process that generates the points. It is desirable to utilize this information to improve the accuracy of curve fitting and to improve data reduction. This paper presents a curve fitting method which utilizes both position and tangent direction data. This method produces G(exp 1) non-rational B-spline curves. From the examples, the method demonstrates very good data reduction rates while maintaining high accuracy in both position and tangent direction.

  11. High Achievement in Mathematics Education in India: A Report from Mumbai

    ERIC Educational Resources Information Center

    Raman, Manya

    2010-01-01

    This paper reports a study aimed at characterizing the conditions that lead to high achievement in mathematics in India. The study involved eight schools in the greater Mumbai region. The main result of the study is that the notion of high achievement itself is problematic, as reflected in the reports about mathematics achievement within and…

  12. Wavefront Amplitude Variation of TPF's High Contrast Imaging Testbed: Modeling and Experiment

    NASA Technical Reports Server (NTRS)

    Shi, Fang; Lowman, Andrew E.; Moody, Dwight C.; Niessner, Albert F.; Trauger, John T.

    2005-01-01

    Knowledge of wavefront amplitude is as important as the knowledge of phase for a coronagraphic high contrast imaging system. Efforts have been made to understand various contributions of the amplitude variation in Terrestrial Planet Finder's (TPF) High Contrast Imaging Testbed (HCIT). Modeling of HCIT with as-built mirror surfaces has shown an amplitude variation of 1.3% due to the phase-amplitude mixing for the testbed's front-end optics. Experimental measurements on the testbed have shown the amplitude variation is about 2.5% with the testbed's illumination pattern has a major contribution as the low order amplitude variation.

  13. Performance Sensitivity Studies on the PIAA Implementation of the High-Contrast Imaging Testbed

    NASA Technical Reports Server (NTRS)

    Sidick, Erkin; Lou, John; Shaklan, Stuart; Levine, Marie

    2010-01-01

    This slide presentation reviews the sensitivity studies on the Phase-Induced Amplitude Apodization (PIAA), or pupil mapping using the High-Contrast Imaging Testbed (HCIT). PIAA is a promising technique in high-dynamic range stellar coronagraph. This presentation reports on the investigation of the effects of the phase and rigid-body errors of various optics on the narrowband contrast performance of the PIAA/HCIT hybrid system. The results have shown that the 2-step wavefront control method utilizing 2-DMs is quite effective in compensating the effects of realistic phase and rigid-body errors of various optics

  14. Breast tumor segmentation in high resolution x-ray phase contrast analyzer based computed tomography

    SciTech Connect

    Brun, E.; Grandl, S.; Sztrókay-Gaul, A.; Gasilov, S.; Barbone, G.; Mittone, A.; Coan, P.; Bravin, A.

    2014-11-01

    Purpose: Phase contrast computed tomography has emerged as an imaging method, which is able to outperform present day clinical mammography in breast tumor visualization while maintaining an equivalent average dose. To this day, no segmentation technique takes into account the specificity of the phase contrast signal. In this study, the authors propose a new mathematical framework for human-guided breast tumor segmentation. This method has been applied to high-resolution images of excised human organs, each of several gigabytes. Methods: The authors present a segmentation procedure based on the viscous watershed transform and demonstrate the efficacy of this method on analyzer based phase contrast images. The segmentation of tumors inside two full human breasts is then shown as an example of this procedure’s possible applications. Results: A correct and precise identification of the tumor boundaries was obtained and confirmed by manual contouring performed independently by four experienced radiologists. Conclusions: The authors demonstrate that applying the watershed viscous transform allows them to perform the segmentation of tumors in high-resolution x-ray analyzer based phase contrast breast computed tomography images. Combining the additional information provided by the segmentation procedure with the already high definition of morphological details and tissue boundaries offered by phase contrast imaging techniques, will represent a valuable multistep procedure to be used in future medical diagnostic applications.

  15. Rectangular Dielectric-loaded Structures for Achieving High Acceleration Gradients

    NASA Astrophysics Data System (ADS)

    Wang, Changbiao; Yakovlev, V. P.; Marshall, T. C.; LaPointe, M. A.; Hirshfield, J. L.

    2006-11-01

    Rectangular dielectric-loaded structures are described that may sustain higher acceleration gradients than conventional all-metal structures with similar apertures. One structure is a test cavity designed to ascertain the breakdown limits of dielectrics, while a second structure could be the basis for a two-beam accelerator. CVD diamond is an attractive dielectric for a high-gradient structure, since the published DC breakdown limit for CVD diamond is ˜ 2 GV/m, although the limit has never been determined for RF fields. Here we present a design of a diamond-lined test cavity to measure the breakdown limit. The designed cavity operates at 34 GHz, where with 10-MW input power it is expected to produce an ˜800 MV/m field on the diamond surface—provided breakdown is avoided. The two channel rectangular dielectric-loaded waveguide could be a two-beam accelerator structure, in which a drive beam is in one channel and an accelerated beam is in the other. The RF power produced by drive bunches in the drive channel is continuously coupled to the acceleration channel. The ratio of fields in the channels (transformer ratio) for the operating mode can be designed by adjusting the dimensions of the structure. An example of the two-channel structure is described, in which a train of five 3-nC drive bunches excites wake fields in the accelerator channel of up to 1.3 GV/m with a transformer ratio of 10 for the design mode.

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

    PubMed

    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.

  17. High and Low Contrast Visual Acuity Are Not Affected in Amyotrophic Lateral Sclerosis.

    PubMed

    Moss, Heather E; Samelson, Monica; Mohan, Girish; Jiang, Qin Li

    2016-01-01

    The afferent visual system may be affected by neuro-degeneration in amyotrophic lateral sclerosis (ALS) based on observations of visual function impairment and retinal inclusions on histopathology in ALS patients. To test the hypothesis that visual acuity is impaired in ALS, we compared three measures of visual acuity in ALS patients (n = 25) attending a multidisciplinary ALS clinic and age matched control subjects (n = 25). Bilateral monocular and binocular visual acuities were assessed using high contrast (black letters on white background) and low contrast (2.5%, 1.25% grey letters on white background) visual acuity charts under controlled lighting conditions following refraction. Binocular summation was calculated as the difference between binocular and best monocular acuity scores. There were no associations between binocular or monocular high contrast visual acuity or low contrast visual acuity and amyotrophic lateral sclerosis diagnosis (generalized estimating equation models accounting for age). Binocular summation was similar in both amyotrophic lateral sclerosis and control subjects. There was a small magnitude association between increased duration of ALS symptoms and reduced 1.25% low contrast visual acuity. This study does not confirm prior observations of impaired visual acuity in patients with amyotrophic lateral sclerosis and does not support this particular measure of visual function for use in broad scale assessment of visual pathway involvement in ALS patients.

  18. High and Low Contrast Visual Acuity Are Not Affected in Amyotrophic Lateral Sclerosis

    PubMed Central

    Samelson, Monica; Mohan, Girish; Jiang, Qin Li

    2016-01-01

    The afferent visual system may be affected by neuro-degeneration in amyotrophic lateral sclerosis (ALS) based on observations of visual function impairment and retinal inclusions on histopathology in ALS patients. To test the hypothesis that visual acuity is impaired in ALS, we compared three measures of visual acuity in ALS patients (n = 25) attending a multidisciplinary ALS clinic and age matched control subjects (n = 25). Bilateral monocular and binocular visual acuities were assessed using high contrast (black letters on white background) and low contrast (2.5%, 1.25% grey letters on white background) visual acuity charts under controlled lighting conditions following refraction. Binocular summation was calculated as the difference between binocular and best monocular acuity scores. There were no associations between binocular or monocular high contrast visual acuity or low contrast visual acuity and amyotrophic lateral sclerosis diagnosis (generalized estimating equation models accounting for age). Binocular summation was similar in both amyotrophic lateral sclerosis and control subjects. There was a small magnitude association between increased duration of ALS symptoms and reduced 1.25% low contrast visual acuity. This study does not confirm prior observations of impaired visual acuity in patients with amyotrophic lateral sclerosis and does not support this particular measure of visual function for use in broad scale assessment of visual pathway involvement in ALS patients. PMID:28033389

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

    NASA Astrophysics Data System (ADS)

    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

  20. Fundamental gain in high-contrast imaging with the large binocular telescope interferometer

    NASA Astrophysics Data System (ADS)

    Patru, Fabien; Esposito, Simone; Puglisi, Alfio; Riccardi, Armando; Pinna, Enrico; Arcidiacono, Carmelo; Hill, John; Hinz, Philip

    2016-08-01

    Numerical simulations for the Large Binocular Telescope Interferometer have shown a fundamental gain in contrast when using two 8m adaptive optics telescopes instead of one, assuming a high Strehl and a cophasing mode. The global gain is improved by a factor 2 in contrast by using the long exposures and by a factor of 10 in contrast by using the short exposures. Indeed, fringes are still present in the short exposure, contrary to the long exposure where the fringes are blurred. Thus, there is some gain in grouping some short exposures with high gain G. This makes the LBTI well suitable for the Angular Differential Imaging technique. A planet will be alternatively located in the dark fringes (G ≈ 10 to 100) and/or in the dark rings (G ≈ 4 to 20). A rotation of 15° is sufficient to pass through at least one gain zone. The LBTI can provide in the visible wavelengths not only high angular resolution (≈ 6:5mas at 750nm) and high sensitivity (by a factor 4), but also a gain in contrast (by a factor 10 to 100) compared to the stand-alone adaptive optics used on each LBT aperture.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  3. The Various Challenges of Subtracting Speckles and Planet Detection/Characterization in High Contrast Imaging

    NASA Astrophysics Data System (ADS)

    Marois, Christian

    2015-08-01

    Significant progresses have been achieved over the last 20 years in the field of speckle subtraction and planet detection. From the early days of simple “reference star subtraction”, astronomers are now using more advance observing techniques, such as the SDI and ADI, that are combined with complex image processing algorithms to gain more than two orders of magnitude of contrast. I will review the various observing techniques and algorithms now used in the field, as well as the various challenges when trying to optimize the speckle subtraction to maximize planet detection and characterization. In addition, I will review the difficult problem of identifying faint planets in noisy speckle-limited images.

  4. An Off-Axis Four-Quadrant Phase Mask (FQPM) Coronagraph for Palomar: High-Contrast Near Bright Stars Imager

    NASA Technical Reports Server (NTRS)

    Haguenauer, Pierre; Serabyn, Eugene; Bloemhof, Eric E.; Troy, Mitchell; Wallace, James K.; Koresko, Chris D.; Mennesson, Bertrand

    2005-01-01

    Direct detection of planets around nearby stars requires the development of high-contrast imaging techniques because of the high difference between their respective fluxes. This led us to test a new coronagraphic approach based on the use of phase mask instead of dark occulting ones. Combined with high-level wavefront correction on an unobscured off-axis section of a large telescope, this method allows imaging very close to the star. Calculations indicate that for a given ground-based on-axis telescope, use of such an off-axis coronagraph provides a near-neighbor detection capability superior to that of a traditional coronagraph utilizing the full telescope aperture. Setting up a laboratory experiment working in near infrared allowed us to demonstrate the principle of the method, and a rejection of 2000:1 has already been achieved.

  5. CT Image Contrast of High-Z Elements: Phantom Imaging Studies and Clinical Implications

    PubMed Central

    Colborn, Robert E.; Edic, Peter M.; Lambert, Jack W.; Torres, Andrew S.; Bonitatibus, Peter J.; Yeh, Benjamin M.

    2016-01-01

    Purpose To quantify the computed tomographic (CT) image contrast produced by potentially useful contrast material elements in clinically relevant imaging conditions. Materials and Methods Equal mass concentrations (grams of active element per milliliter of solution) of seven radiodense elements, including iodine, barium, gadolinium, tantalum, ytterbium, gold, and bismuth, were formulated as compounds in aqueous solutions. The compounds were chosen such that the active element dominated the x-ray attenuation of the solution. The solutions were imaged within a modified 32-cm CT dose index phantom at 80, 100, 120, and 140 kVp at CT. To simulate larger body sizes, 0.2-, 0.5-, and 1.0-mm-thick copper filters were applied. CT image contrast was measured and corrected for measured concentrations and presence of chlorine in some compounds. Results Each element tested provided higher image contrast than iodine at some tube potential levels. Over the range of tube potentials that are clinically practical for average-sized and larger adults—that is, 100 kVp and higher—barium, gadolinium, ytterbium, and tantalum provided consistently increased image contrast compared with iodine, respectively demonstrating 39%, 56%, 34%, and 24% increases at 100 kVp; 39%, 66%, 53%, and 46% increases at 120 kVp; and 40%, 72%, 65%, and 60% increases at 140 kVp, with no added x-ray filter. Conclusion The consistently high image contrast produced with 100–140 kVp by tantalum compared with bismuth and iodine at equal mass concentration suggests that tantalum could potentially be favorable for use as a clinical CT contrast agent. © RSNA, 2015 Online supplemental material is available for this article. PMID:26356064

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

    SciTech Connect

    Evans, Julia Wilhelmsen

    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

  7. High contrast imaging with an arbitrary aperture: active correction of aperture discontinuities: fundamental limits and practical trades offs

    NASA Astrophysics Data System (ADS)

    Pueyo, Laurent; Norman, Colin Arthur; Soummer, Remi; Perrin, Marshall D.; N'Diaye, Mamadou; Choquet, Elodie

    2015-01-01

    In a recent paper we discussed a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach, named Active Compensation of Aperture Discontinuities (ACAD) relies on two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum. In particular we showed that broadband high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies for a variety of telescope pupil geometries. In this paper we first focus on the fundamental limits and practical trade-offs associated with ACAD. In a first part we will study the fundamental limits and practical tradeoffs associated with ACAD, regardless of the downstream coronagraphic architecture. The mathematical techniques to finding ACAD DM shapes require to solve a complex differential equation. We will first discuss the scaling laws underlying this non-linear solution and their impact of DM placement and geometry wishing the optical design of an instrument. We will then consider the sensitivity to low order aberrations: in principle an ACAD solution that comprises large strokes will be more sensitive to these aberrations than one with smaller strokes. As a consequence, we will quantify this sensitive both using analytical models and numerical simulations. We will present diffractive end to end simulations and quantify the ultimate contrast and bandwidth achievable with ACAD, which can be reached by superposing using a classical linear wavefront control algorithms on top of the Monge Ampere solution. Finally, recent work has shown that coronagraph designs can also accommodate for secondary support structures and/or segments gaps, at a

  8. Highly relaxing gadolinium based MRI contrast agents responsive to Mg2+ sensing.

    PubMed

    Abada, Sabah; Lecointre, Alexandre; Elhabiri, Mourad; Esteban-Gómez, David; Platas-Iglesias, Carlos; Tallec, Gaylord; Mazzanti, Marinella; Charbonnière, Loïc J

    2012-04-28

    A Gd complex based on a polyphosphonated pyridyl ligand shows a very high stability in aqueous solution (log K(EuL) = 25.7), a high relaxivity (8.5 mM(-1) s(-1) at 25 °C and 20 MHz) and a marked and selective relaxivity enhancement (37%) in the presence of Mg(2+), opening interesting perspectives for the design of cation responsive contrast agents.

  9. K-Stacker, a new way of detecting and characterizing exoplanets with high contrast imaging instruments

    NASA Astrophysics Data System (ADS)

    Le Coroller, H.; Nowak, M.; Arnold, L.; Dohlen, K.; Fusco, T.; Sauvage, J. F.; Vigan, A.

    2015-10-01

    This year, a second generation of coronagraphs dedicated to high-contrast direct imaging of exoplanets is starting operations. Among them, SPHERE, installed at the focus of the UT3 Very Large Telescope, reaches unprecedented contrast ratios up to 10^{-6} - 10^{-7}, using eXtreme Adaptive Optics, Angular Differential Imaging (ADI) and Spectral Differential Imaging (SDI) techniques. In this paper, we present a new method called Keplerian-Stacker that improves the detection limit of high contrast instruments like SPHERE, by up to a factor of 10. It consists of observing a star on a long enough period to let a hypothetical planet around that star move along its orbit. Even if in each individual observation taken during one night, we do not detect anything, we show that it is possible, using an optimization algorithm, to re-center the images according to keplerian motions (ex: 10-100 images taken over a long period of typically 1-10 years) and detect planets otherwise unreachable. This method can be used in combination with the ADI technics (or possibly any other high contrast data reduction method) to improve the Signal to Noise Ratio in each individual image, and to further improve the global detection limit. It also directly provides orbital parameters of the detected planets, as a by-product of the optimization algorithm.

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

    NASA Technical Reports Server (NTRS)

    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.

  11. Golden carbon nanotubes as multimodal photoacoustic and photothermal high-contrast molecular agents

    PubMed Central

    Kim, Jin-Woo; Galanzha, Ekaterina I.; Shashkov, Evgeny V.; Moon, Hyung-Mo; Zharov, Vladimir P.

    2012-01-01

    Carbon nanotubes have shown promise as contrast agents for photoacoustic and photothermal imaging of tumours and infections because they offer high resolution and allow deep tissue imaging. However, in vivo applications have been limited by the relatively low absorption displayed by nanotubes at near-infrared wavelengths and concerns over toxicity. Here, we show that gold-plated carbon nanotubes—termed golden carbon nanotubes—can be used as photoacoustic and photothermal contrast agents with enhanced near-infrared contrast (~102-fold) for targeting lymphatic vessels in mice using extremely low laser fluence levels of a few mJ cm−2. Antibody-conjugated golden carbon nanotubes were used to map the lymphatic endothelial receptor, and preliminary in vitro viability tests show golden carbon nanotubes have minimal toxicity. This new nanomaterial could be an effective alternative to existing nanoparticles and fluorescent labels for non-invasive targeted imaging of molecular structures in vivo. PMID:19809462

  12. High-resolution visualization of airspace structures in intact mice via synchrotron phase-contrast X-ray imaging (PCXI)

    PubMed Central

    Parsons, David W; Morgan, Kaye; Donnelley, Martin; Fouras, Andreas; Crosbie, Jeffrey; Williams, Ivan; Boucher, Richard C; Uesugi, Kentaro; Yagi, Naoto; Siu, Karen K W

    2008-01-01

    Anatomical visualization of airspace-containing organs in intact small animals has been limited by the resolution and contrast available from current imaging methods such as X-ray, micro-computed tomography and magnetic resonance imaging. Determining structural relationships and detailed anatomy has therefore relied on suitable fixation, sectioning and histological processing. More complex and informative analyses such as orthogonal views of an organ and three-dimensional structure visualizations have required different animals and image sets, laboriously processed to gather this complementary structural information. Precise three-dimensional anatomical views have always been difficult to achieve in small animals. Here we report the ability of phase-contrast synchrotron X-ray imaging to provide detailed two- and three-dimensional visualization of airspace organ structures in intact animals. Using sub-micrometre square pixel charge-coupled device array detectors, the structure and anatomy of hard and soft tissues, and of airspaces, is readily available using phase-contrast synchrotron X-ray imaging. Moreover, software-controlled volume-reconstructions of tomographic images not only provide unsurpassed image clarity and detail, but also selectable anatomical views that cannot be obtained with established histological techniques. The morphology and structure of nasal and lung airways and the middle ear are illustrated in intact mice, using two- and three-dimensional representations. The utility of phase-contrast synchrotron X-ray imaging for non-invasively localizing objects implanted within airspaces, and the detection of gas bubbles transiting live airways, are other novel features of this visualization methodology. The coupling of phase-contrast synchrotron X-ray imaging technology with software-based reconstruction techniques holds promise for novel and high-resolution non-invasive examination of airspace anatomy in small animal models. PMID:19172736

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

    PubMed

    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).

  14. Formal Operational Precocity and Achievement in Biology among Some Nigerian High School Students.

    ERIC Educational Resources Information Center

    Ehindero, Olusola Joseph

    1979-01-01

    Compares the performances on a battery of six Piagetian tasks of 80 Nigerian high school students classified as high and low achievers in biology. The relationship between performance of very bright biology students (high achievers) and intellectual precocity is also investigated. (HM)

  15. The Chinese High School Student's Stress in the School and Academic Achievement

    ERIC Educational Resources Information Center

    Liu, Yangyang; Lu, Zuhong

    2011-01-01

    In a sample of 466 Chinese high school students, we examined the relationships between Chinese high school students' stress in the school and their academic achievements. Regression mixture modelling identified two different classes of the effects of Chinese high school students' stress on their academic achievements. One class contained 87% of…

  16. Beyond Academic Reputation: Factors that Influence the College of First Choice for High Achieving Students

    ERIC Educational Resources Information Center

    Schoenherr, Holly J.

    2009-01-01

    Studies that have investigated college choice factors for high-achieving students repeatedly cite academic reputation as one of the top indicators of choice but have not indicated why some high-achieving students choose to attend universities with a less prestigious reputation than the more highly prestigious options available to them. The purpose…

  17. Does High School Facility Quality Affect Student Achievement? A Two-Level Hierarchical Linear Model

    ERIC Educational Resources Information Center

    Bowers, Alex J.; Urick, Angela

    2011-01-01

    The purpose of this study is to isolate the independent effects of high school facility quality on student achievement using a large, nationally representative U.S. database of student achievement and school facility quality. Prior research on linking school facility quality to student achievement has been mixed. Studies that relate overall…

  18. The Effects of Web-Based/Non-Web-Based Problem-Solving Instruction and High/Low Achievement on Students' Problem-Solving Ability and Biology Achievement

    ERIC Educational Resources Information Center

    Yu, Wen-Feng; She, Hsiao-Ching; Lee, Yu-Mei

    2010-01-01

    This study investigates the effects of two factors: the mode of problem-solving instruction (i.e. Web-based versus non-Web-based) and the level of academic achievement (i.e. high achievers versus low achievers) on students' problem-solving ability and biology achievement. A quasi-experimental design was used, in which the experimental group…

  19. Acoustic angiography: a new high frequency contrast ultrasound technique for biomedical imaging

    NASA Astrophysics Data System (ADS)

    Shelton, Sarah E.; Lindsey, Brooks D.; Gessner, Ryan; Lee, Yueh; Aylward, Stephen; Lee, Hyunggyun; Cherin, Emmanuel; Foster, F. Stuart; Dayton, Paul A.

    2016-05-01

    Acoustic Angiography is a new approach to high-resolution contrast enhanced ultrasound imaging enabled by ultra-broadband transducer designs. The high frequency imaging technique provides signal separation from tissue which does not produce significant harmonics in the same frequency range, as well as high resolution. This approach enables imaging of microvasculature in-vivo with high resolution and signal to noise, producing images that resemble x-ray angiography. Data shows that acoustic angiography can provide important information about the presence of disease based on vascular patterns, and may enable a new paradigm in medical imaging.

  20. Normal Visual Acuity and Electrophysiological Contrast Gain in Adults with High-Functioning Autism Spectrum Disorder

    PubMed Central

    Tebartz van Elst, Ludger; Bach, Michael; Blessing, Julia; Riedel, Andreas; Bubl, Emanuel

    2015-01-01

    A common neurodevelopmental disorder, autism spectrum disorder (ASD), is defined by specific patterns in social perception, social competence, communication, highly circumscribed interests, and a strong subjective need for behavioral routines. Furthermore, distinctive features of visual perception, such as markedly reduced eye contact and a tendency to focus more on small, visual items than on holistic perception, have long been recognized as typical ASD characteristics. Recent debate in the scientific community discusses whether the physiology of low-level visual perception might explain such higher visual abnormalities. While reports of this enhanced, “eagle-like” visual acuity contained methodological errors and could not be substantiated, several authors have reported alterations in even earlier stages of visual processing, such as contrast perception and motion perception at the occipital cortex level. Therefore, in this project, we have investigated the electrophysiology of very early visual processing by analyzing the pattern electroretinogram-based contrast gain, the background noise amplitude, and the psychophysical visual acuities of participants with high-functioning ASD and controls with equal education. Based on earlier findings, we hypothesized that alterations in early vision would be present in ASD participants. This study included 33 individuals with ASD (11 female) and 33 control individuals (12 female). The groups were matched in terms of age, gender, and education level. We found no evidence of altered electrophysiological retinal contrast processing or psychophysical measured visual acuities. There appears to be no evidence for abnormalities in retinal visual processing in ASD patients, at least with respect to contrast detection. PMID:26379525

  1. Super-nonlinear fluorescence microscopy for high-contrast deep tissue imaging

    NASA Astrophysics Data System (ADS)

    Wei, Lu; Zhu, Xinxin; Chen, Zhixing; Min, Wei

    2014-02-01

    Two-photon excited fluorescence microscopy (TPFM) offers the highest penetration depth with subcellular resolution in light microscopy, due to its unique advantage of nonlinear excitation. However, a fundamental imaging-depth limit, accompanied by a vanishing signal-to-background contrast, still exists for TPFM when imaging deep into scattering samples. Formally, the focusing depth, at which the in-focus signal and the out-of-focus background are equal to each other, is defined as the fundamental imaging-depth limit. To go beyond this imaging-depth limit of TPFM, we report a new class of super-nonlinear fluorescence microscopy for high-contrast deep tissue imaging, including multiphoton activation and imaging (MPAI) harnessing novel photo-activatable fluorophores, stimulated emission reduced fluorescence (SERF) microscopy by adding a weak laser beam for stimulated emission, and two-photon induced focal saturation imaging with preferential depletion of ground-state fluorophores at focus. The resulting image contrasts all exhibit a higher-order (third- or fourth- order) nonlinear signal dependence on laser intensity than that in the standard TPFM. Both the physical principles and the imaging demonstrations will be provided for each super-nonlinear microscopy. In all these techniques, the created super-nonlinearity significantly enhances the imaging contrast and concurrently extends the imaging depth-limit of TPFM. Conceptually different from conventional multiphoton processes mediated by virtual states, our strategy constitutes a new class of fluorescence microscopy where high-order nonlinearity is mediated by real population transfer.

  2. On-chip preparation of nanoscale contrast agents towards high-resolution ultrasound imaging.

    PubMed

    Peyman, Sally A; McLaughlan, James R; Abou-Saleh, Radwa H; Marston, Gemma; Johnson, Benjamin R G; Freear, Steven; Coletta, P Louise; Markham, Alexander F; Evans, Stephen D

    2016-02-21

    Micron-sized lipid-stabilised bubbles of heavy gas have been utilised as contrast agents for diagnostic ultrasound (US) imaging for many years. Typically bubbles between 1 and 8 μm in diameter are produced to enhance imaging in US by scattering sound waves more efficiently than surrounding tissue. A potential area of interest for Contrast Enhanced Ultrasound (CEUS) are bubbles with diameters <1 μm or 'nanobubbles.' As bubble diameter decreases, ultrasonic resonant frequency increases, which could lead to an improvement in resolution for high-frequency imaging applications when using nanobubbles. In addition, current US contrast agents are limited by their size to the vasculature in vivo. However, molecular-targeted nanobubbles could penetrate into the extra-vascular space of cancerous tissue providing contrast in regions inaccessible to traditional microbubbles. This paper reports a new microfluidic method for the generation of sub-micron sized lipid stabilised particles containing perfluorocarbon (PFC). The nanoparticles are produced in a unique atomisation-like flow regime at high production rates, in excess of 10(6) particles per s and at high concentration, typically >10(11) particles per mL. The average particle diameter appears to be around 100-200 nm. These particles, suspected of being a mix of liquid and gaseous C4F10 due to Laplace pressure, then phase convert into nanometer sized bubbles on the application of US. In vitro ultrasound characterisation from these nanoparticle populations showed strong backscattering compared to aqueous filled liposomes of a similar size. The nanoparticles were stable upon injection and gave excellent contrast enhancement when used for in vivo imaging, compared to microbubbles with an equivalent shell composition.

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

    PubMed Central

    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

  4. Achieving High Strength and High Ductility in Friction Stir-Processed Cast Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Yuan, Wei; Panigrahi, Sushanta K.; Mishra, Rajiv S.

    2013-08-01

    Friction stir processing (FSP) is emerging as an effective tool for microstructural modification and property enhancement. As-cast AZ91 magnesium alloy was friction stir processed with one-pass and two-pass to examine the influence of processing conditions on microstructural evolution and corresponding mechanical properties. Grain refinement accompanied with development of strong basal texture was observed for both processing conditions. Ultrafine-grained (UFG) AZ91 was achieved under two-pass FSP with fine precipitates distributed on the grain boundary. The processed UFG AZ91 exhibited a high tensile strength of ~435 MPa (117 pct improvement) and tensile fracture elongation of ~23 pct. The promising combination of strength and ductility is attributed to the elimination of casting porosity, and high density of fine precipitates in an UFG structure with quite low dislocation density. The effects of grain size, precipitate, and texture on deformation behavior have been discussed.

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

    SciTech Connect

    Kemp, Gregory Elijah

    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

  6. Single-shot measurement of >1010 pulse contrast for ultra-high peak-power lasers

    NASA Astrophysics Data System (ADS)

    Wang, Yongzhi; Ma, Jingui; Wang, Jing; Yuan, Peng; Xie, Guoqiang; Ge, Xulei; Liu, Feng; Yuan, Xiaohui; Zhu, Heyuan; Qian, Liejia

    2014-01-01

    Real-time pulse-contrast observation with a high dynamic range is a prerequisite to tackle the contrast challenge in ultra-high peak-power lasers. However, the commonly used delay-scanning cross-correlator (DSCC) can only provide the time-consumed measurements for repetitive lasers. Single-shot cross-correlator (SSCC) becomes essential in optimizing laser systems and exploring contrast mechanisms. Here we report our progress in developing SSCC towards its practical use. By integrating both the techniques of scattering-noise reduction and sensitive parallel detection into SSCC, we demonstrate a high dynamic range of >1010, which, to our best knowledge, is the first demonstration of an SSCC with a dynamic range comparable to that of commercial DSCCs. The comparison of high-dynamic measurement performances between SSCC and a standard DSCC (Sequoia, Amplitude Technologies) is also carried out on a 200 TW Ti:sapphire laser, and the consistency of results verifies the veracity of our SSCC.

  7. An Analysis of Java Programming Behaviors, Affect, Perceptions, and Syntax Errors among Low-Achieving, Average, and High-Achieving Novice Programmers

    ERIC Educational Resources Information Center

    Rodrigo, Ma. Mercedes T.; Andallaza, Thor Collin S.; Castro, Francisco Enrique Vicente G.; Armenta, Marc Lester V.; Dy, Thomas T.; Jadud, Matthew C.

    2013-01-01

    In this article we quantitatively and qualitatively analyze a sample of novice programmer compilation log data, exploring whether (or how) low-achieving, average, and high-achieving students vary in their grasp of these introductory concepts. High-achieving students self-reported having the easiest time learning the introductory programming…

  8. A method for high-energy, low-dose mammography using edge illumination x-ray phase-contrast imaging

    NASA Astrophysics Data System (ADS)

    Diemoz, Paul C.; Bravin, Alberto; Sztrókay-Gaul, Anikó; Ruat, Marie; Grandl, Susanne; Mayr, Doris; Auweter, Sigrid; Mittone, Alberto; Brun, Emmanuel; Ponchut, Cyril; Reiser, Maximilian F.; Coan, Paola; Olivo, Alessandro

    2016-12-01

    Since the breast is one of the most radiosensitive organs, mammography is arguably the area where lowering radiation dose is of the uttermost importance. Phase-based x-ray imaging methods can provide opportunities in this sense, since they do not require x-rays to be stopped in tissue for image contrast to be generated. Therefore, x-ray energy can be considerably increased compared to those usually exploited by conventional mammography. In this article we show how a novel, optimized approach can lead to considerable dose reductions. This was achieved by matching the edge-illumination phase method, which reaches very high angular sensitivity also at high x-ray energies, to an appropriate image processing algorithm and to a virtually noise-free detection technology capable of reaching almost 100% efficiency at the same energies. Importantly, while proof-of-concept was obtained at a synchrotron, the method has potential for a translation to conventional sources.

  9. High contrast neutron radiography with optical devices in Kyoto University reactor

    NASA Astrophysics Data System (ADS)

    Kawabata, Y.; Nakano, T.; Hino, M.; Sunohara, H.; Matsushima, U.; Takenaka, N.

    2004-08-01

    The high-contrast neutron radiography has been performed at a VCN guide (VCN) and a supermirror cold neutron guide (CN-3) in Kyoto University Reactor. The large absorption cross-section of very low-energy neutrons can show a slight change of sample which thermal neutrons can not show. The effectiveness is shown in the fields of botany, agriculture and industrial researches. A new spectrum change option using high Qc supermirror ( m=4) is attached. It can change the upper limit of the energy of exposure neutrons by reflections, and gives a high flexibility of the experimental condition.

  10. CT of multiple sclerosis: reassessment of delayed scanning with high doses of contrast material

    SciTech Connect

    Spiegel, S.M.; Vinuela, F.; Fox, A.J.; Pelz, D.M.

    1985-09-01

    A prospective study involving 87 patients was carried out to evaluate the necessity for a high dose of contrast material in addition to delayed computed tomographic (CT) scanning for optimal detection of the lesions of multiple sclerosis in the brain. In patients with either clinically definite multiple sclerosis or laboratory-supported definite multiple sclerosis, CT scans were obtained with a uniform protocol. Lesions consistent with multiple sclerosis were demonstrated on the second scan in 54 patients. In 36 of these 54 patients, the high-dose delayed scan added information. These results are quite similar to those of a previous study from this institution using different patients, in whom the second scan was obtained immediately after the bolus injection of contrast material containing 40 g of organically bound iodine. The lack of real difference in the results of the two studies indicate that the increased dose, not just the delay in scanning, is necessary for a proper study.

  11. Photoacoustic contrast imaging of biological tissues with nanodiamonds fabricated for high near-infrared absorbance

    PubMed Central

    Zhang, Ti; Cui, Huizhong; Fang, Chia-Yi; Su, Long-Jyun; Ren, Shenqiang; Chang, Huan-Cheng; Yang, Xinmai

    2013-01-01

    Abstract. Radiation-damaged nanodiamonds (DNDs) are potentially ideal optical contrast agents for photoacoustic (PA) imaging in biological tissues due to their low toxicity and high optical absorbance. PA imaging contrast agents have been limited to quantum dots and gold particles, since most existing carbon-based nanoparticles, including fluorescent nanodiamonds, do not have sufficient optical absorption in the near-infrared (NIR) range. A new DND by He+ ion beam irradiation with very high NIR absorption was synthesized. These DNDs produced a 71-fold higher PA signal on a molar basis than similarly dimensioned gold nanorods, and 7.1 fmol of DNDs injected into rodents could be clearly imaged 3 mm below the skin surface with PA signal enhancement of 567% using an 820-nm laser wavelength. PMID:23400417

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

    NASA Technical Reports Server (NTRS)

    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.

  13. Analysis of High Contrast Imaging Techniques for Space Based Direct Planetary Imaging

    NASA Technical Reports Server (NTRS)

    Lyon, Richard G.; Gezari, Dan Y.; Nisenson, P.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We report on our ongoing investigations of a number of techniques for direct detection and imaging of Earth-like planets around nearby stellar sources. Herein, we give a quantitative analysis of these techniques and compare and contrast them via computer simulations. The techniques we will be reporting on are Bracewell Interferometry, Nisenson Apodized Square Aperture, and Coronagraphic masking techniques. We parameterize our results with respect to wavelength, aperture size, effects of mirror speckle, both mid- and high-spatial frequency, detector and photon noise as well pointing error. The recent numerous detections of Jupiter and Saturn like planets has driven a resurgence in research of space based high contrast imaging techniques for direct planetary imaging. Work is currently ongoing for concepts for NASA's Terrestrial Planet Finder mission and a number of study teams have been funded. The authors are members of one team.

  14. The HST/STIS BAR5 Occulter: High Contrast in Space at Visible Wavelengths

    NASA Astrophysics Data System (ADS)

    Debes, John H.; Gaspar, Andras; Schneider, Glenn; Proffitt, Charles

    2015-11-01

    The Hubble Space Telescope currently has only one operational high contrast imaging coronagraphic mode, the 50CORON imaging mode of the Space Telescope Imaging Spectrograph (STIS). 50CORON includes two intersecting wedges and two bar occulting masks in an image plane ahead of the detector that block light from bright stars to reveal the faint emission from circumstellar disks or faint companions. Recently, the smallest supported inner working angle for these occulters was 0.3". We present in this poster the commissioning of new occulting locations on the detector that allow for inner working angles as close as 0.15" at the new BAR5 position. We show preliminary results for BAR5 using two nearby debris disks, AU Mic and Beta Pictoris, and provide interested users with a prescription for how to design their own high contrast imaging observations.

  15. The Effect of the Time Management Art on Academic Achievement among High School Students in Jordan

    ERIC Educational Resources Information Center

    Al-Zoubi, Maysoon

    2016-01-01

    This study aimed at recognizing the effect of the Time Management Art on academic achievement among high school students in the Hashemite Kingdom of Jordan. The researcher employed the descriptive-analytic research to achieve the purpose of the study where he chose a sample of (2000) high school female and male students as respondents to the…

  16. Effects of a Collaborative Science Intervention on High Achieving Students' Learning Anxiety and Attitudes toward Science

    ERIC Educational Resources Information Center

    Hong, Zuway-R.

    2010-01-01

    This study investigated the effects of a collaborative science intervention on high achieving students' learning anxiety and attitudes toward science. Thirty-seven eighth-grade high achieving students (16 boys and 21 girls) were selected as an experimental group who joined a 20-week collaborative science intervention, which integrated and utilized…

  17. Individual and Longitudinal Differences among High and Low-Achieving, LD, and ADHD L2 Learners

    ERIC Educational Resources Information Center

    Sparks, Richard L.; Humbach, Nancy; Javorsky, James

    2008-01-01

    High-achieving (HA) and low-achieving (LA), learning disabled (LD), and attention deficit hyperactivity disorder (ADHD) high school students were followed over two years of L2 study and compared on measures of L1 literacy (reading and writing) in elementary school, L1 cognitive ability, L2 aptitude, oral and written L2 proficiency, and L2 word…

  18. International Note: Between-Domain Relations of Chinese High School Students' Academic Achievements

    ERIC Educational Resources Information Center

    Yangyang, Liu

    2012-01-01

    The present study examined the between-domain relations of Chinese high school students' academic achievements. In a sample of 1870 Chinese 10th grade students, the results indicated that Chinese high school students' academic achievements were correlated across nine subjects. In line with the previous Western findings, the findings suggested that…

  19. A Longitudinal Investigation of Project-Based Instruction and Student Achievement in High School Social Studies

    ERIC Educational Resources Information Center

    Summers, Emily J.; Dickinson, Gail

    2012-01-01

    This longitudinal study focused on how project-based instruction (PBI) influenced secondary social studies students' academic achievement and promoted College and Career Readiness (CCR). We explored and compared student achievement in a PBI high school versus a traditional instruction high school within the same rural school district. While…

  20. Parent-Child Relations and Psychological Adjustment among High-Achieving Chinese and European American Adolescents

    ERIC Educational Resources Information Center

    Qin, Desiree Baolian; Rak, Eniko; Rana, Meenal; Donnellan, M. Brent

    2012-01-01

    Chinese American students are often perceived as problem-free high achievers. Recent research, however, suggests that high-achieving Chinese American students can experience elevated levels of stress, especially comparing to their peers from other ethnic groups. In this paper, we examine how family dynamics may influence psychological adjustment…

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Highly efficient terahertz radiation from a thin foil irradiated by a high-contrast laser pulse.

    PubMed

    Jin, Z; Zhuo, H B; Nakazawa, T; Shin, J H; Wakamatsu, S; Yugami, N; Hosokai, T; Zou, D B; Yu, M Y; Sheng, Z M; Kodama, R

    2016-09-01

    Radially polarized intense terahertz (THz) radiation behind a thin foil irradiated by ultrahigh-contrast ultrashort relativistic laser pulse is recorded by a single-shot THz time-domain spectroscopy system. As the thickness of the target is reduced from 30 to 2 µm, the duration of the THz emission increases from 5 to over 20 ps and the radiation energy increases dramatically, reaching ∼10.5mJ per pulse, corresponding to a laser-to-THz radiation energy conversion efficiency of 1.7%. The efficient THz emission can be attributed to reflection (deceleration and acceleration) of the laser-driven hot electrons by the target-rear sheath electric field. The experimental results are consistent with that of a simple model as well as particle-in-cell simulation.

  4. High sensitivity phase retrieval method in grating-based x-ray phase contrast imaging

    SciTech Connect

    Wu, Zhao; Gao, Kun; Chen, Jian; Wang, Dajiang; Wang, Shenghao; Chen, Heng; Bao, Yuan; Shao, Qigang; Wang, Zhili; Zhang, Kai; Zhu, Peiping; Wu, Ziyu

    2015-02-15

    Purpose: Grating-based x-ray phase contrast imaging is considered as one of the most promising techniques for future medical imaging. Many different methods have been developed to retrieve phase signal, among which the phase stepping (PS) method is widely used. However, further practical implementations are hindered, due to its complex scanning mode and high radiation dose. In contrast, the reverse projection (RP) method is a novel fast and low dose extraction approach. In this contribution, the authors present a quantitative analysis of the noise properties of the refraction signals retrieved by the two methods and compare their sensitivities. Methods: Using the error propagation formula, the authors analyze theoretically the signal-to-noise ratios (SNRs) of the refraction images retrieved by the two methods. Then, the sensitivities of the two extraction methods are compared under an identical exposure dose. Numerical experiments are performed to validate the theoretical results and provide some quantitative insight. Results: The SNRs of the two methods are both dependent on the system parameters, but in different ways. Comparison between their sensitivities reveals that for the refraction signal, the RP method possesses a higher sensitivity, especially in the case of high visibility and/or at the edge of the object. Conclusions: Compared with the PS method, the RP method has a superior sensitivity and provides refraction images with a higher SNR. Therefore, one can obtain highly sensitive refraction images in grating-based phase contrast imaging. This is very important for future preclinical and clinical implementations.

  5. The Meaning High-Achieving African-American Males in an Urban High School Ascribe to Mathematics

    ERIC Educational Resources Information Center

    Thompson, LaTasha; Davis, Julius

    2013-01-01

    Many researchers, educators, administrators, policymakers and members of the general public doubt the prevalence of high-achieving African-American males in urban high schools capable of excelling in mathematics. As part of a larger study, the current study explored the educational experiences of four high-achieving African-American males…

  6. Glancing angle Talbot-Lau grating interferometers for phase contrast imaging at high x-ray energy

    NASA Astrophysics Data System (ADS)

    Stutman, D.; Finkenthal, M.

    2012-08-01

    A Talbot-Lau interferometer is demonstrated using micro-periodic gratings inclined at a glancing angle along the light propagation direction. Due to the increase in the effective thickness of the absorption gratings, the device enables differential phase contrast imaging at high x-ray energy, with improved fringe visibility (contrast). For instance, at 28° glancing angle, we obtain up to ˜35% overall interferometer contrast with a spectrum having ˜43 keV mean energy, suitable for medical applications. In addition, glancing angle interferometers could provide high contrast at energies above 100 keV, enabling industrial and security applications of phase contrast imaging.

  7. High resolution 3 Tesla contrast-enhanced MR angiography of the hands in Raynaud's disease.

    PubMed

    Walcher, J; Strecker, R; Goldacker, S; Winterer, J; Langer, M; Bley, T A

    2007-04-01

    Raynaud's disease is associated with disorders in blood circulation of the hands. The gold standard to visualise pathology of digital arteries is catheter angiography. Contrast-enhanced MR angiography (CE MRA) has developed even more as an alternative non-invasive method to digital subtraction angiography, mostly for pelvic or lower limb vessels. We report a case of primary Raynaud's disease with high-grade stenosis and an occlusion of the digital arteries. This case illustrates the benefit and efficiency of CE MRA at high fields in depicting location and extension of peripheral arterial alterations.

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

    PubMed

    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.

  9. Contrast MR of the brain after high-perfusion cardiopulmonary bypass

    SciTech Connect

    Simonson, T.M.; Yuh, W.T.C.; Hindman, B.J.; Embrey, R.P.; Halloran, J.I.; Behrendt, D.M. )

    1994-01-01

    To study the efficacy of contrast MR imaging in the evaluation of central nervous system complications in the cardiopulmonary bypass patient and attempt to explain their pathophysiology based on the MR appearance and the cardiopulmonary bypass protocol. Nineteen patients were prospectively studied with contrast MR examinations the day before and 3 to 7 days after cardiopulmonary bypass, to determine the nature, extent, and number of new postoperative MR abnormalities. Cardiopulmonary bypass parameters used in our institution included: membrane oxygenation, arterial filtration with a pore size of 25 [mu]m, and a relatively high perfusion rate to produce a cardiac index of 2.0 to 2.5 L min per m[sup 2]. The preoperative noncontrast MR examination showed age-related changes and/or signs of ischemia in 60% of patients on the day before surgery. However, there was no abnormal enhancement or new T2 abnormalities on any postoperative MR examination to suggest hypoperfusion or emboli. None of the 19 patients developed overt neurologic deficits postoperatively. Review of the cardiopulmonary bypass protocol used indicated significant variations in technique at different institutions. Contrast MR imaging demonstrated no new abnormalities in patients after cardiopulmonary bypass performed with strict in-line arterial filtration and relatively high perfusion. MR imaging is feasible in the early postoperative period after cardiopulmonary bypass and may offer a convenient method for evaluation of the neurologic impact of technical factors associated with cardiopulmonary bypass. 17 refs.

  10. Characterisation of a turbulent module for the MITHIC high-contrast imaging testbed

    NASA Astrophysics Data System (ADS)

    Vigan, A.; Postnikova, M.; Caillat, A.; Sauvage, J.-F.; Dohlen, K.; El Hadi, K.; Fusco, T.; Lamb, M.; N'Diaye, M.

    2016-07-01

    Future high-contrast imagers on ground-based extremely large telescopes will have to deal with the segmentation of the primary mirrors. Residual phase errors coming from the phase steps at the edges of the segments will have to be minimized in order to reach the highest possible wavefront correction and thus the best contrast performance. To study these effects, we have developed the MITHIC high-contrast testbed, which is designed to test various strategies for wavefront sensing, including the Zernike sensor for Extremely accurate measurements of Low-level Differential Aberrations (ZELDA) and COronagraphic Focal-plane wave-Front Estimation for Exoplanet detection (COFFEE). We recently equipped the bench with a new atmospheric turbulence simulation module that offers both static phase patterns representing segmented primary mirrors and continuous phase strips representing atmospheric turbulence filtered by an AO or an XAO system. We present a characterisation of the module using different instruments and wavefront sensors, and the first coronagraphic measurements obtained on MITHIC.

  11. Atomically Thin Graphene Windows That Enable High Contrast Electron Microscopy without a Specimen Vacuum Chamber.

    PubMed

    Han, Yimo; Nguyen, Kayla X; Ogawa, Yui; Park, Jiwoong; Muller, David A

    2016-12-14

    Scanning electron microscopes (SEMs) require a high vacuum environment to generate and shape an electron beam for imaging; however, the vacuum conditions greatly limit the nature of specimens that can be examined. From a purely scattering physics perspective, it is not necessary to place the specimen inside the vacuum chamber-the mean free paths (MFPs) for electron scattering in air at typical SEM beam voltages are 50-100 μm. This is the idea behind the airSEM, which removes the specimen vacuum chamber from the SEM and places the sample in air. The thickness of the gas layer is less than a MFP from an electron-transparent window to preserve the shape and resolution of the incident beam, resulting in comparable imaging quality to an all-vacuum SEM. Present silicon nitride windows scatter far more strongly than the air gap and are currently the contrast and resolution limiting factor in the airSEM. Graphene windows have been used previously to wrap or seal samples in vacuum for imaging. Here we demonstrate the use of a robust bilayer graphene window for sealing the electron optics from the room environment, providing an electron transparent window with only a 2% drop in contrast. There is a 5-fold-increase in signal/noise ratio for imaging compared to multi-MFP-thick silicon nitride windows, enabling high contrast in backscattered, transmission, and surface imaging modes for the new airSEM geometry.

  12. High-contrast Imager for Complex Aperture Telescopes (HICAT): II. Design overview and first light results

    NASA Astrophysics Data System (ADS)

    N'Diaye, Mamadou; Choquet, Elodie; Egron, Sylvain; Pueyo, Laurent; Leboulleux, Lucie; Levecq, Olivier; Perrin, Marshall D.; Elliot, Erin; Wallace, J. Kent; Hugot, Emmanuel; Marcos, Michel; Ferrari, Marc; Long, Chris A.; Anderson, Rachel; DiFelice, Audrey; Soummer, Rémi

    2014-08-01

    We present a new high-contrast imaging testbed designed to provide complete solutions in wavefront sensing, control and starlight suppression with complex aperture telescopes. The testbed was designed to enable a wide range of studies of the effects of such telescope geometries, with primary mirror segmentation, central obstruction, and spiders. The associated diffraction features in the point spread function make high-contrast imaging more challenging. In particular the testbed will be compatible with both AFTA-like and ATLAST-like aperture shapes, respectively on-axis monolithic, and on-axis segmented telescopes. The testbed optical design was developed using a novel approach to define the layout and surface error requirements to minimize amplitude­ induced errors at the target contrast level performance. In this communication we compare the as-built surface errors for each optic to their specifications based on end-to-end Fresnel modelling of the testbed. We also report on the testbed optical and optomechanical alignment performance, coronagraph design and manufacturing, and preliminary first light results.

  13. Color and contrast sensitivity after glare from high-brightness LEDs

    NASA Astrophysics Data System (ADS)

    Reidenbach, H.-D.

    2008-02-01

    The color contrast capability was investigated for 3 volunteers with 7 specially developed test charts in red, green, blue, cyan, magenta, yellow and black as a reference, namely without and after glare from 4 colored high-brightness LEDs. Each subject completed 56 tests in order to check especially the ability to discriminate low contrast. It was found that a contrast decrease of one level is equivalent to an increase of about 4 s in the required identification time and in addition a delay time between about 14 s and 16 s has been measured at the beginning of the respective test as a result of the dazzling glare from an LED. In addition trials have been performed with 4 different pseudoisochromatic color plates designed by Ishihara for color vision. These plates have been used to determine temporary color deficiencies after an exposure from a high-brightness LED. For this purpose 40 volunteers have been included in a laboratory test. Color vision was impaired for periods between 27 s and 186 s depending on the applied color plate and respective LED color.

  14. Detection of high k turbulence using two dimensional phase contrast imaging on LHD

    SciTech Connect

    Michael, C. A.; Tanaka, K.; Akiyama, T.; Kawahata, K.; Vyacheslavov, L. N.; Sanin, A.; Kharchev, N. K.; Okajima, S.

    2008-10-15

    High k turbulence, up to 30 cm{sup -1}, can be measured using the two dimensional CO2 laser phase contrast imaging system on LHD. Recent hardware improvements and experimental results are presented. Precise control over the lens positions in the detection system is necessary because of the short depth of focus for high k modes. Remote controllable motors to move optical elements were installed, which, combined with measurements of the response to ultrasound injection, allowed experimental verification and shot-to-shot adjustment of the object plane. Strong high k signals are observed within the first 100-200 ms after the initial electron cyclotron heating (ECH) breakdown, in agreement with gyrotron scattering. During later times in the discharge, the entire k spectrum shifts to lower values (although the total amplitude does not change significantly), and the weaker high k signals are obscured by leakage of low k components at low frequency, and detector noise, at high frequency.

  15. Methods for the shaping high-power picosecond laser pulses with a high-contrast ratio

    SciTech Connect

    Malinov, V. A.; Charukchev, A. V.; Chernov, V. N.; Nikitin, N. V.; Potapov, S. L.; Efanov, V. M.; Yarin, P. M.

    1998-02-20

    We present the performance of the electrooptical system based on four Pockels cells with 10 and 20 mm diameters, each of them is driving by its own drift step recovery diode pulse generator. We are developing electro-optic deflector system for CPA laser using two identical deflectors (diverging and converging) and three spatial filters. The results of numerical modeling of the time-dependent distributions of the intensity in the beam are presented. A peak-to-background intensity ratio more than five orders is achieved by this technique. We have developed a new pulse generator based on single drift step recovery diode producing two identical electrical pulses with output voltage up to 15 kV, FWHM of 1.5 ns, rise time of 0.7 ns and jitter of 100 ps at a 100 Hz repetition rate to electro-optic deflectors.

  16. Optical contrast enhancement of high-resolution ocular fundus imaging in vivo using polarimetry

    NASA Astrophysics Data System (ADS)

    Yang, Hansheng; Rao, Xuejun; Zhang, Yudong

    2007-11-01

    The adaptive optics (AO) retina imaging was performed with contrast enhancement by characterizing polarization parameters of the living retina. A removable pair of polarization state generating unit near the optical source and analysis unit near the CCD camera was incorporated into the basic 37-channle deformable mirror AO microscopic ophthalmoscope. Double-pass imaging polarimetry of the human eye was carried out, then incomplete Mueller matrix was calculated and analyzed to optimize the retina imaging condition using polarized light, which caused the subretinal structures with different polarization properties to emerge from the scattering light background, so the contrast of the image can be substantially enhanced. This method is demonstrated briefly and its validity was tested in the laboratory. The high-resolution images of ocular fundus are compared with 8-frame-averaging images we obtained prior to this method. The experiment results now show improved visualization of fundus structures to some extent without greatly sacrificing image resolution.

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

    SciTech Connect

    Higginson, Drew Pitney

    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

  18. Anti-biofouling polymer-decorated lutetium-based nanoparticulate contrast agents for in vivo high-resolution trimodal imaging.

    PubMed

    Liu, Zhen; Dong, Kai; Liu, Jianhua; Han, Xueli; Ren, Jinsong; Qu, Xiaogang

    2014-06-25

    Nanomaterials have gained considerable attention and interest in the development of novel and high-resolution contrast agents for medical diagnosis and prognosis in clinic. A classical urea-based homogeneous precipitation route that combines the merits of in situ thermal decomposition and surface modification is introduced to construct polyethylene glycol molecule (PEG)-decorated hybrid lutetium oxide nanoparticles (PEG-UCNPs). By utilizing the admirable optical and magnetic properties of the yielded PEG-UCNPs, in vivo up-conversion luminescence and T1 -enhanced magnetic resonance imaging of small animals are conducted, revealing obvious signals after subcutaneous and intravenous injection, respectively. Due to the strong X-ray absorption and high atomic number of lanthanide elements, X-ray computed-tomography imaging based on PEG-UCNPs is then designed and carried out, achieving excellent imaging outcome in animal experiments. This is the first example of the usage of hybrid lutetium oxide nanoparticles as effective nanoprobes. Furthermore, biodistribution, clearance route, as well as long-term toxicity are investigated in detail after intravenous injection in a murine model, indicating the overall safety of PEG-UCNPs. Compared with previous lanthanide fluorides, our nanoprobes exhibit more advantages, such as facile construction process and nearly total excretion from the animal body within a month. Taken together, these results promise the use of PEG-UCNPs as a safe and efficient nanoparticulate contrast agent for potential application in multimodal imaging.

  19. An optimal point spread function subtraction algorithm for high-contrast imaging: a demonstration with angular differential imaging

    SciTech Connect

    Lafreniere, D; Marois, C; Doyon, R; Artigau, E; Nadeau, D

    2006-09-19

    Direct imaging of exoplanets is limited by bright quasi-static speckles in the point spread function (PSF) of the central star. This limitation can be reduced by subtraction of reference PSF images. We have developed an algorithm to construct an optimal reference PSF image from an arbitrary set of reference images. This image is built as a linear combination of all available images and is optimized independently inside multiple subsections of the image to ensure that the absolute minimum residual noise is achieved within each subsection. The algorithm developed is completely general and can be used with many high contrast imaging observing strategies, such as angular differential imaging (ADI), roll subtraction, spectral differential imaging, reference star observations, etc. The performance of the algorithm is demonstrated for ADI data. It is shown that for this type of data the new algorithm provides a gain in sensitivity by up 22 to a factor 3 at small separation over the algorithm previously used.

  20. The impact of collective teacher efficacy on student achievement in high school science

    NASA Astrophysics Data System (ADS)

    Burcham, Mark W.

    This dissertation was designed to examine the impact of collective teacher efficacy on high school science achievement by looking at relationships among collective teacher efficacy, its two constructs, group competence and group task analysis, and high school science achievement scores at four rural high schools in Northwestern North Carolina. The researcher gathered historical test data from the testing coordinator from the school system and then administered the Collective Teacher Efficacy Instrument, developed by Goddard, Hoy, and Woolfolk Hoy (2000), to 24 science teachers from the four high schools. Using this information, the researcher conducted statistical analyses to determine the relationships among collective teacher efficacy, group competence, and group task analysis as compared with the tested science curriculum (physical science, biology, chemistry, and physics). The researcher also examined which construct was the most contributing factor and examined differences in efficacy levels and student achievement levels at each high school. Analysis of the data from this study indicated collective teacher efficacy, as well as its two constructs, group competence and group task analysis, does have a positive impact on student achievement in high school science. Analysis of the data revealed group competence is the major contributing factor for student achievement in biology and group task analysis is the major contributing factor for student achievement in physical science, chemistry, and physics. Further analysis of the data in this study, also revealed that the two high schools with the highest levels of collective teacher efficacy had the highest levels of student achievement.

  1. Achieving High Rates and High Uniformity in Copper Chemical Mechanical Polishing

    NASA Astrophysics Data System (ADS)

    Nolan, Lucy Marjorie

    The chemical mechanical polishing of Copper (Cu-CMP) is a complex and poorly understood process. Despite this, it is widely used throughout the semiconductor and microelectronics industries, and makes up a significant portion of wafer processing costs. In these contexts, desirable polishing outcomes such as a high rate of removal from the copper surface, and high removal rate uniformity, are achieved largely by trial-and-error. In this study, the same outcomes are pursued through a systematic investigation of polishing lubrication characteristics and abrasive and oxidiser concentrations in the polishing slurry. A strong link between lubrication characteristics, quantified by the dimensionless Sommerfield number, and the uniformity of polishing is demonstrated. A mechanism for the observed relationship is proposed, based on an adaptation of hydrodynamic lubrication theory. The overall rate of removal is maximized by polishing in a slurry containing oxidiser and abrasives in a synergistic ratio. Polishing away from this ratio has additional effects on the overall quality of the surface produced. Transport of slurry across the polishing pad is investigated by using tracers; the results demonstrate that slurry usage can be reduced in many circumstances with no impact on overall polishing outcomes, reducing overall processing costs. These findings are combined to design a polishing process, with good results.

  2. Achieving high strength and high ductility in magnesium alloy using hard-plate rolling (HPR) process

    PubMed Central

    Wang, Hui–Yuan; Yu, Zhao–Peng; Zhang, Lei; Liu, Chun–Guo; Zha, Min; Wang, Cheng; Jiang, Qi–Chuan

    2015-01-01

    Magnesium alloys are highly desirable for a wide range of lightweight structural components. However, rolling Mg alloys can be difficult due to their poor plasticity, and the strong texture yielded from rolling often results in poor plate forming ability, which limits their further engineering applications. Here we report a new hard-plate rolling (HPR) route which achieves a large reduction during a single rolling pass. The Mg-9Al-1Zn (AZ91) plates processed by HPR consist of coarse grains of 30–60 μm, exhibiting a typical basal texture, fine grains of 1–5 μm and ultrafine (sub) grains of 200–500 nm, both of the latter two having a weakened texture. More importantly, the HPR was efficient in gaining a simultaneous high strength and uniform ductility, i.e., ~371 MPa and ~23%, respectively. The superior properties should be mainly attributed to the cooperation effect of the multimodal grain structure and weakened texture, where the former facilitates a strong work hardening while the latter promotes the basal slip. The HPR methodology is facile and effective, and can avoid plate cracking that is prone to occur during conventional rolling processes. This strategy is applicable to hard-to-deform materials like Mg alloys, and thus has a promising prospect for industrial application. PMID:26603776

  3. Achieving high strength and high ductility in magnesium alloy using hard-plate rolling (HPR) process

    NASA Astrophysics Data System (ADS)

    Wang, Hui–Yuan; Yu, Zhao–Peng; Zhang, Lei; Liu, Chun–Guo; Zha, Min; Wang, Cheng; Jiang, Qi–Chuan

    2015-11-01

    Magnesium alloys are highly desirable for a wide range of lightweight structural components. However, rolling Mg alloys can be difficult due to their poor plasticity, and the strong texture yielded from rolling often results in poor plate forming ability, which limits their further engineering applications. Here we report a new hard-plate rolling (HPR) route which achieves a large reduction during a single rolling pass. The Mg-9Al-1Zn (AZ91) plates processed by HPR consist of coarse grains of 30-60 μm, exhibiting a typical basal texture, fine grains of 1-5 μm and ultrafine (sub) grains of 200-500 nm, both of the latter two having a weakened texture. More importantly, the HPR was efficient in gaining a simultaneous high strength and uniform ductility, i.e., ~371 MPa and ~23%, respectively. The superior properties should be mainly attributed to the cooperation effect of the multimodal grain structure and weakened texture, where the former facilitates a strong work hardening while the latter promotes the basal slip. The HPR methodology is facile and effective, and can avoid plate cracking that is prone to occur during conventional rolling processes. This strategy is applicable to hard-to-deform materials like Mg alloys, and thus has a promising prospect for industrial application.

  4. Achieving high strength and high ductility in magnesium alloy using hard-plate rolling (HPR) process.

    PubMed

    Wang, Hui-Yuan; Yu, Zhao-Peng; Zhang, Lei; Liu, Chun-Guo; Zha, Min; Wang, Cheng; Jiang, Qi-Chuan

    2015-11-25

    Magnesium alloys are highly desirable for a wide range of lightweight structural components. However, rolling Mg alloys can be difficult due to their poor plasticity, and the strong texture yielded from rolling often results in poor plate forming ability, which limits their further engineering applications. Here we report a new hard-plate rolling (HPR) route which achieves a large reduction during a single rolling pass. The Mg-9Al-1Zn (AZ91) plates processed by HPR consist of coarse grains of 30-60 μm, exhibiting a typical basal texture, fine grains of 1-5 μm and ultrafine (sub) grains of 200-500 nm, both of the latter two having a weakened texture. More importantly, the HPR was efficient in gaining a simultaneous high strength and uniform ductility, i.e., ~371 MPa and ~23%, respectively. The superior properties should be mainly attributed to the cooperation effect of the multimodal grain structure and weakened texture, where the former facilitates a strong work hardening while the latter promotes the basal slip. The HPR methodology is facile and effective, and can avoid plate cracking that is prone to occur during conventional rolling processes. This strategy is applicable to hard-to-deform materials like Mg alloys, and thus has a promising prospect for industrial application.

  5. New York State Superintendents and Board Presidents Attitudes on Superintendent Responsibilities in High-Achieving and Low-Achieving School Districts

    ERIC Educational Resources Information Center

    Murphy, Matthew J.

    2009-01-01

    The purpose of this study is to determine the perceptions of New York State superintendents and board presidents in high-achieving and low-achieving school districts on the six superintendent leadership responsibilities identified by Waters and Marzano (2006) and their relationship to improving student achievement: (1) creating research-relevant…

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

    NASA Astrophysics Data System (ADS)

    Higginson, Drew Pitney

    The cone-guided fast ignition approach to Inertial Confinement 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 first 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 Kalpha x-rays is used as a diagnostic to infer the electron energy coupled into the wire. Imaging the x-ray emission allowed an effective 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

  7. Experiment and simulation of novel liquid crystal plasma mirrors for high contrast, intense laser pulses

    PubMed Central

    Poole, P. L.; Krygier, A.; Cochran, G. E.; Foster, P. S.; Scott, G. G.; Wilson, L. A.; Bailey, J.; Bourgeois, N.; Hernandez-Gomez, C.; Neely, D.; Rajeev, P. P.; Freeman, R. R.; Schumacher, D. W.

    2016-01-01

    We describe the first demonstration of plasma mirrors made using freely suspended, ultra-thin films formed dynamically and in-situ. We also present novel particle-in-cell simulations that for the first time incorporate multiphoton ionization and dielectric models that are necessary for describing plasma mirrors. Dielectric plasma mirrors are a crucial component for high intensity laser applications such as ion acceleration and solid target high harmonic generation because they greatly improve pulse contrast. We use the liquid crystal 8CB and introduce an innovative dynamic film formation device that can tune the film thickness so that it acts as its own antireflection coating. Films can be formed at a prolonged, high repetition rate without the need for subsequent realignment. High intensity reflectance above 75% and low-field reflectance below 0.2% are demonstrated, as well as initial ion acceleration experimental results that demonstrate increased ion energy and yield on shots cleaned with these plasma mirrors. PMID:27557592

  8. Experiment and simulation of novel liquid crystal plasma mirrors for high contrast, intense laser pulses

    SciTech Connect

    Poole, P. L.; Krygier, A.; Cochran, G. E.; Foster, P. S.; Scott, G. G.; Wilson, L. A.; Bailey, J.; Bourgeois, N.; Hernandez-Gomez, C.; Neely, D.; Rajeev, P. P.; Freeman, R. R.; Schumacher, D. W.

    2016-08-25

    Here, we describe the first demonstration of plasma mirrors made using freely suspended, ultra-thin films formed dynamically and in-situ. We also present novel particle-in-cell simulations that for the first time incorporate multiphoton ionization and dielectric models that are necessary for describing plasma mirrors. Dielectric plasma mirrors are a crucial component for high intensity laser applications such as ion acceleration and solid target high harmonic generation because they greatly improve pulse contrast. We use the liquid crystal 8CB and introduce an innovative dynamic film formation device that can tune the film thickness so that it acts as its own antireflection coating. Films can be formed at a prolonged, high repetition rate without the need for subsequent realignment. High intensity reflectance above 75% and low-field reflectance below 0.2% are demonstrated, as well as initial ion acceleration experimental results that demonstrate increased ion energy and yield on shots cleaned with these plasma mirrors.

  9. Experiment and simulation of novel liquid crystal plasma mirrors for high contrast, intense laser pulses.

    PubMed

    Poole, P L; Krygier, A; Cochran, G E; Foster, P S; Scott, G G; Wilson, L A; Bailey, J; Bourgeois, N; Hernandez-Gomez, C; Neely, D; Rajeev, P P; Freeman, R R; Schumacher, D W

    2016-08-25

    We describe the first demonstration of plasma mirrors made using freely suspended, ultra-thin films formed dynamically and in-situ. We also present novel particle-in-cell simulations that for the first time incorporate multiphoton ionization and dielectric models that are necessary for describing plasma mirrors. Dielectric plasma mirrors are a crucial component for high intensity laser applications such as ion acceleration and solid target high harmonic generation because they greatly improve pulse contrast. We use the liquid crystal 8CB and introduce an innovative dynamic film formation device that can tune the film thickness so that it acts as its own antireflection coating. Films can be formed at a prolonged, high repetition rate without the need for subsequent realignment. High intensity reflectance above 75% and low-field reflectance below 0.2% are demonstrated, as well as initial ion acceleration experimental results that demonstrate increased ion energy and yield on shots cleaned with these plasma mirrors.

  10. Understanding and Reversing Underachievement, Low Achievement, and Achievement Gaps among High-Ability African American Males in Urban School Contexts

    ERIC Educational Resources Information Center

    Ford, Donna Y.; Moore, James L., III

    2013-01-01

    This article focuses on the achievement gap, with attention devoted to underachievement and low achievement among African American males in urban school contexts. More specifically, the article explains problems and issues facing or confronting these Black male students in urban education settings. A central part of this discussion is grounded in…

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

    PubMed Central

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

    2016-01-01

    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. PMID:27734931

  12. ARTIFICIAL INCOHERENT SPECKLES ENABLE PRECISION ASTROMETRY AND PHOTOMETRY IN HIGH-CONTRAST IMAGING

    SciTech Connect

    Jovanovic, N.; Guyon, O.; Pathak, P.; Kudo, T.; Martinache, F.; Hagelberg, J.

    2015-11-10

    State-of-the-art coronagraphs employed on extreme adaptive optics enabled instruments are constantly improving the contrast detection limit for companions at ever-closer separations from the host star. In order to constrain their properties and, ultimately, compositions, it is important to precisely determine orbital parameters and contrasts with respect to the stars they orbit. This can be difficult in the post-coronagraphic image plane, as by definition the central star has been occulted by the coronagraph. We demonstrate the flexibility of utilizing the deformable mirror in the adaptive optics system of the Subaru Coronagraphic Extreme Adaptive Optics system to generate a field of speckles for the purposes of calibration. Speckles can be placed up to 22.5 λ/D from the star, with any position angle, brightness, and abundance required. Most importantly, we show that a fast modulation of the added speckle phase, between 0 and π, during a long science integration renders these speckles effectively incoherent with the underlying halo. We quantitatively show for the first time that this incoherence, in turn, increases the robustness and stability of the adaptive speckles, which will improve the precision of astrometric and photometric calibration procedures. This technique will be valuable for high-contrast imaging observations with imagers and integral field spectrographs alike.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Shaped pupil Lyot coronagraphs: high-contrast solutions for restricted focal planes

    NASA Astrophysics Data System (ADS)

    Zimmerman, Neil T.; Eldorado Riggs, A. J.; Jeremy Kasdin, N.; 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 Telescope Assets (WFIRST-AFTA) coronagraph. These SPLCs help to enable two scientific objectives of the WFIRST-AFTA mission: (1) broadband spectroscopy to characterize exoplanet atmospheres in reflected starlight and (2) debris disk imaging.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Gender and High School Chemistry: Student Perceptions on Achievement in a Selective Setting

    ERIC Educational Resources Information Center

    Cousins, Andrew; Mills, Martin

    2015-01-01

    This paper reports on research undertaken in a middle-class Australian school. The focus of the research was on the relationship between gender and students' engagement with high school chemistry. Achievement data from many OECD [Organisation for Economic Co-operation and Development] countries suggest that middle-class girls are achieving equally…

  17. Predicting Early Academic Failure in High School from Prior Academic Achievement, Psychosocial Characteristics, and Behavior

    ERIC Educational Resources Information Center

    Casillas, Alex; Robbins, Steve; Allen, Jeff; Kuo, Yi-Lung; Hanson, Mary Ann; Schmeiser, Cynthia

    2012-01-01

    The authors examined the differential effects of prior academic achievement, psychosocial, behavioral, demographic, and school context factors on early high school grade point average (GPA) using a prospective study of 4,660 middle-school students from 24 schools. The findings suggest that (a) prior grades and standardized achievement are the…

  18. Accelerated Mathematics and High-Ability Students' Math Achievement in Grades Three and Four

    ERIC Educational Resources Information Center

    Stanley, Ashley M.

    2011-01-01

    The purpose of this study was to explore the relationship between the use of a computer-managed integrated learning system entitled Accelerated Math (AM) as a supplement to traditional mathematics instruction on achievement as measured by TerraNova achievement tests of third and fourth grade high-ability students. Gender, socioeconomic status, and…

  19. An Analysis of Mathematics Course Sequences for Low Achieving Students at a Comprehensive Technical High School

    ERIC Educational Resources Information Center

    Edge, D. Michael

    2011-01-01

    This non-experimental study attempted to determine how the different prescribed mathematic tracks offered at a comprehensive technical high school influenced the mathematics performance of low-achieving students on standardized assessments of mathematics achievement. The goal was to provide an analysis of any statistically significant differences…

  20. The Impact of Charter Schools on Promoting High Levels of Mathematics Achievement

    ERIC Educational Resources Information Center

    Plucker, Jonathan A.; Makel, Matthew C.; Rapp, Kelly E.

    2007-01-01

    This study compares achievement levels for high ability students attending charter schools and students in traditional public schools in Georgia. Researchers examined student achievement (as assessed by the state's Criterion-Referenced Competency Tests) using three comparison groups: students in the closest traditional schools with similar grade…

  1. A Quantitative Comparison of Pennsylvania High School Student Achievement by Middle States Association's Accreditation Status

    ERIC Educational Resources Information Center

    Johnson, Christopher A.

    2012-01-01

    As public school accountability for student achievement has continued to increase, prior to and as a result of the No Child Left Behind Act of 2001, schools have sought ways of bringing new instructional services to their students to raise their levels of achievement. Some Pennsylvania public high schools have attempted to improve student…

  2. Unforgiving Confucian Culture: A Breeding Ground for High Academic Achievement, Test Anxiety and Self-Doubt?

    ERIC Educational Resources Information Center

    Stankov, Lazar

    2010-01-01

    This paper reviews findings from several studies that contribute to our understanding of cross-cultural differences in academic achievement, anxiety and self-doubt. The focus is on comparisons between Confucian Asian and European regions. Recent studies indicate that high academic achievement of students from Confucian Asian countries is…

  3. Instructional, Transformational, and Managerial Leadership and Student Achievement: High School Principals Make a Difference

    ERIC Educational Resources Information Center

    Valentine, Jerry W.; Prater, Mike

    2011-01-01

    This statewide study examined the relationships between principal managerial, instructional, and transformational leadership and student achievement in public high schools. Differences in student achievement were found when schools were grouped according to principal leadership factors. Principal leadership behaviors promoting instructional and…

  4. Cohort versus Non-Cohort High School Students' Math Performance: Achievement Test Scores and Coursework

    ERIC Educational Resources Information Center

    Parke, Carol S.; Keener, Dana

    2011-01-01

    The purpose of this study is to compare multiple measures of mathematics achievement for 1,378 cohort students who attended the same high school in a district from 9th to 12th grade with non-cohort students in each grade level. Results show that mobility had an impact on math achievement. After accounting for gender, ethnicity, and SES, adjusted…

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

    PubMed Central

    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. PMID:25537588

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

    SciTech Connect

    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-1and 5000 s-1strain-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 imagedviaphase-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 diffractionviain-house software (WBXRD_GUI). Of current interest is the ability to evaluate crystald-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates.

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

    PubMed

    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.

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

    SciTech Connect

    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–1and 5000 s–1strain-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 imagedviaphase-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 diffractionviain-house software (WBXRD_GUI). Finally, of current interest is the ability to evaluate crystald-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates.

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

    DOE PAGES

    Hudspeth, M.; Sun, T.; Parab, N.; ...

    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–1and 5000 s–1strain-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 imagedviaphase-contrast imaging. It is also shownmore » that adequate signal-to-noise ratios are achieved for the detected white-beam diffraction patterns, thereby allowing sufficient information to perform quantitative data analysis diffractionviain-house software (WBXRD_GUI). Finally, of current interest is the ability to evaluate crystald-spacing, texture evolution and material phase transitions, all of which will be established from experiments performed at the aforementioned elevated strain-rates.« less

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  12. Determining Chemically and Spatially Resolved Atomic Profile of Low Contrast Interface Structure with High Resolution

    PubMed Central

    Nayak, Maheswar; Pradhan, P. C.; Lodha, G. S.

    2015-01-01

    We present precise measurements of atomic distributions of low electron density contrast at a buried interface using soft x-ray resonant scattering. This approach allows one to construct chemically and spatially highly resolved atomic distribution profile upto several tens of nanometer in a non-destructive and quantitative manner. We demonstrate that the method is sensitive enough to resolve compositional differences of few atomic percent in nano-scaled layered structures of elements with poor electron density differences (0.05%). The present study near the edge of potential impurities in soft x-ray range for low-Z system will stimulate the activity in that field. PMID:25726866

  13. Magneto-exciton-polariton condensation in a sub-wavelength high contrast grating based vertical microcavity

    SciTech Connect

    Fischer, J.; Brodbeck, S.; Worschech, L.; Kamp, M.; Schneider, C.; Höfling, S.; Zhang, B.; Wang, Z.; Deng, H.

    2014-03-03

    We comparably investigate the diamagnetic shift of an uncoupled quantum well exciton with a microcavity exciton-polariton condensate on the same device. The sample is composed of multiple GaAs quantum wells in an AlAs microcavity, surrounded by a Bragg reflector and a sub-wavelength high contrast grating reflector. Our study introduces an independent and easily applicable technique, namely, the measurement of the condensate diamagnetic shift, which directly probes matter contributions in polariton condensates and hence discriminates it from a conventional photon laser.

  14. Performance Sensitivity Studies on the PIAA Implementation of the High-Contrast Imaging Testbed

    NASA Technical Reports Server (NTRS)

    Sidick, Erkin; Lou, John Z.; Shaklan, Stuart; Levine, Marie

    2009-01-01

    We have investigated the dependence of the High Contrast Imaging Testbed (HCIT) Phase Induced Amplitude Apodization (PIAA) coronagraph system performance on the rigid-body perturbations of various optics. The structural design of the optical system as well as the parameters of various optical elements used in the analysis are drawn from those of the PIAA/HCIT system that have been and will be implemented, and the simulation takes into account the surface errors of various optics. In this paper, we report our findings when the input light is a narrowband beam.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

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

    2016-01-01

    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. PMID:27265624

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

    SciTech Connect

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

    2008-01-15

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

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

    PubMed

    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.

  19. Recursive starlight and bias estimation for high-contrast imaging with an extended Kalman filter

    NASA Astrophysics Data System (ADS)

    Riggs, A. J. Eldorado; Kasdin, N. Jeremy; 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 Princeton's High Contrast Imaging Laboratory, we demonstrate that the IEKF allows wavefront correction at least as fast as with a Kalman filter and provides the most accurate detection of a faint companion. The nonlinear IEKF formalism allows us to pursue other strategies such as parameter estimation to improve wavefront correction.

  20. Low Voltage, High Speed & High Contrast Electrooptical Thin Film Devices for Free Space Optical Interconnects

    DTIC Science & Technology

    2007-11-02

    Space Optical Interconnects (FSOI) for future ultra fast computing /communications systems. Fabry - Perot thin film Electrooptic(EO) modulators (STFP...low modulation voltages.This is enabled by Fabry - Perot (F-P) etalons of the EO film as modulators either in the reflection or transmission mode. In...Tuning’ of a F-P EOLM with respect to thickness variation for high extinction ratios. Demonstration of ’proof-of concept’ of a ’Self Tuned Fabry - Perot

  1. Piezoelectric Composite Micromachined Multifrequency Transducers for High-Resolution, High-Contrast Ultrasound Imaging for Improved Prostate Cancer Assessment

    DTIC Science & Technology

    2015-08-01

    682. S. Li, W. Chang, W. Huang, and X. Jiang, ൰-MHz Micromachined PMN-PT Composite Ultrasound Array for Medical Imaging ," in ASME 2015...Jiang, ൰-MHz Micromachined PMN-PT Composite Ultrasound Array for Medical Imaging ," in ASME 2015 International Mechanical Engineering Congress...Resolution, High- Contrast Ultrasound Imaging For Improved Prostate Cancer Assessment PRINCIPAL INVESTIGATOR: Paul A. Dayton CONTRACTING ORGANIZATION

  2. Photonic band gaps of increasingly isotropic crystals at high dielectric contrasts

    NASA Astrophysics Data System (ADS)

    Pollard, M. E.; Parker, G. J.; Charlton, M. D. B.

    2012-03-01

    Photonic band gaps (PBGs) are highly sensitive to lattice geometry and dielectric contrast. Here, we report theoretical and experimental confirmation of PBGs in photonic crystals (PhCs) with increasing levels of structural isotropy. These structures are: a standard 6-fold hexagonal lattice, a locally 12-fold Archimedean-like crystal, a true quasicrystal generated by non-random Stampfli inflation, and a biomimetic crystal based on Fibonacci phyllotaxis. Experimental transmission spectra were obtained at microwave frequencies using high-index alumina (ɛ = 9.61) rods. The results were compared to FDTD-calculated transmission spectra and PWE-calculated band diagrams. Wide and deep (> 60dB) primary TM gaps present in all high-index samples are related to reciprocal space vectors with the strongest Fourier coefficients. Their mid-gap frequencies are largely independent of the lattice geometry for comparable fill factors, whereas the gap ratios shrink monotonically as structural isotropy increases.

  3. Impacts of comprehensive reading instruction on diverse outcomes of low- and high-achieving readers.

    PubMed

    Guthrie, John T; McRae, Angela; Coddington, Cassandra S; Lutz Klauda, Susan; Wigfield, Allan; Barbosa, Pedro

    2009-01-01

    Low-achieving readers in Grade 5 often lack comprehension strategies, domain knowledge, word recognition skills, fluency, and motivation to read. Students with such multiple reading needs seem likely to benefit from instruction that supports each of these reading processes. The authors tested this expectation experimentally by comparing the effects of Concept-Oriented Reading Instruction (CORI) with traditional instruction (TI) on several outcomes in a 12-week intervention for low achievers and high achievers. Low achievers in the CORI group were afforded explicit instruction, leveled texts, and motivation support. Compared with TI students, CORI students scored higher on posttest measures of word recognition speed, reading comprehension on the Gates-MacGinitie Reading Test, and ecological knowledge. CORI was equally effective for lower achievers and higher achievers. Explicitly supporting multiple aspects of reading simultaneously appeared to benefit diverse learners on a range of reading outcomes.

  4. Understanding the Elements of Operational Reliability: A Key for Achieving High Reliability

    NASA Technical Reports Server (NTRS)

    Safie, Fayssal M.

    2010-01-01

    This viewgraph presentation reviews operational reliability and its role in achieving high reliability through design and process reliability. The topics include: 1) Reliability Engineering Major Areas and interfaces; 2) Design Reliability; 3) Process Reliability; and 4) Reliability Applications.

  5. A Quantitative Literature Review of Cooperative Learning Effects on High School and College Chemistry Achievement.

    ERIC Educational Resources Information Center

    Bowen, Craig W.

    2000-01-01

    Describes meta-analysis, a quantitative approach to conducting literature reviews. Illustrates the power of this technique by reporting the quantitative effects of cooperative learning on chemistry achievement in high school and college classes. (Contains 32 references.) (WRM)

  6. Dual Inversion Recovery Ultrashort Echo Time (DIR UTE) Imaging: Creating High Contrast for Short-T2 Species

    PubMed Central

    Du, Jiang; Takahashi, Atsushi M.; Bae, Won C.; Chung, Christine B.; Bydder, Graeme M.

    2015-01-01

    Imaging of short-T2 species requires not only a short echo time (TE) but also efficient suppression of long-T2 species in order to maximize the short-T2 contrast and dynamic range. This paper introduces a method of long-T2 suppression using two long adiabatic inversion pulses. The first adiabatic inversion pulse inverts the magnetization of long-T2 water and the second one inverts that of fat. Short-T2 species experience a significant transverse relaxation during the long adiabatic inversion process, and are minimally affected by the inversion pulses. Data acquisition with a short TE of 8 μs starts following a time delay of TI1 for the inverted water magnetization to reach a null point, and a time delay of TI2 for the inverted fat magnetization to reach a null point. The suppression of long-T2 species depends on proper combination of TI1, TI2 and TR. It is insensitive to RF inhomogeneities because of the adiabatic inversion pulses. The feasibility of this dual inversion recovery ultrashort TE (DIR UTE) technique was demonstrated on phantoms, cadaveric specimens and healthy volunteers using a clinical 3T scanner. High image contrast was achieved for the deep radial and calcified layers of articular cartilage, cortical bone and the Achilles tendon. PMID:20099332

  7. Extreme AO: The future of high-contrast imaging with adaptive optics

    NASA Astrophysics Data System (ADS)

    Macintosh, B.

    2001-05-01

    Title: Extreme AO: The future of high-contrast-imaging with adaptive optics. Adaptive optics (AO) partially cancels wavefront aberrations caused by atmospheric turbulence and can allow ground-basd telescope to reach their full diffraction-limited resolution. A fundamental limitation of all AO systems is that they have little effect on the atmospheric scattered light halo beyond a control radius roughly given by the wavelength of interest divided by the effective actuator spaceing d; for typical modern AO systems, d=60 cm and the control radius is about 0.6 arcseconds at H band. AO can still enhance contrast even beyond this radius, especially for point-source companions, by concentrating the light from the companion into a diffraction-limited spike, but the residual light remains a limitation on our ability to carry out high-contrast imaging from the ground. We will discuss potential improvements to AO over the next decade and the science they will enable. First, in the near term, high-order AO systems will soon be operational on most 8-10 m telescopes; such systems are theoretically capable of directly detecting extrasolar planets in wide (20-150 AU) orbits, and the capabilities and limitations of these systems will be discussed. Second, in the moderate term, new instrument technologies could substantially increase the performance of these systems, including exotic phase-based coronagraphs or "dark speckle" techniques. Third, it will soon be possible to construct "extreme" adaptive optics (EAO) systems, with many thousand actuators and d=5-20cm, capable of more deeply surpressing the atmospheric halo out to a much larger radius than current systems. Coronagraphs and EAO will substantially increase our sensitivity to diffuse circumstellar dust and could conceivably reach the contrast levels necessary to see giant plants around a handful of nearby stars. Finally, within a decade construction should be underway on next-generation extremely large (25-100 m) telescopes

  8. A Comparison of Emotional-Motivational (A-R-D Theory) Personality Characteristics in Learning Disabled, Normal Achieving, and High Achieving Children.

    ERIC Educational Resources Information Center

    Hufano, Linda D.

    The study examined emotional-motivational personality characteristics of 15 learning disabled, 15 normal achieving, and 15 high achieving students (grades 3-5). The study tested the hypothesis derived from the A-R-D (attitude-reinforcer-discriminative) theory of motivation that learning disabled (LD) children differ from normal and high achieving…

  9. The Outward Bound Bridging Course for Low-Achieving High School Males: Effect on Academic Achievement and Multidimensional Self-Concepts.

    ERIC Educational Resources Information Center

    Marsh, Herbert W.; Richards, Garry

    The Outward Bound Bridging Course is a 6-week residential program designed to improve academic achievement and self-concepts in low-achieving high school males. During 1980-1984, five courses were conducted for 66 Australian high school males. Most of them were ninth grade students, chosen on the basis of poor academic performance, an apparent…

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

    PubMed Central

    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

    2016-01-01

    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+. PMID:27585638

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

    SciTech Connect

    Higginson, D. P.; Link, A.; Sawada, H.; Wilks, S. C.; Chawla, S. R.; Chen, C. D.; Jarrott, L. C.; Flippo, K. A.; McLean, H. S.; Patel, P. K.; Perez, F.; Beg, F. N.; Bartal, T.; Wei, M. S.

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Development of optics for x-ray phase-contrast imaging of high energy density plasmas

    SciTech Connect

    Stutman, D.; Finkenthal, M.; Moldovan, N.

    2010-10-15

    Phase-contrast or refraction-enhanced x-ray radiography can be useful for the diagnostic of low-Z high energy density plasmas, such as imploding inertial confinement fusion (ICF) pellets, due to its sensitivity to density gradients. To separate and quantify the absorption and refraction contributions to x-ray images, methods based on microperiodic optics, such as shearing interferometry, can be used. To enable applying such methods with the energetic x rays needed for ICF radiography, we investigate a new type of optics consisting of grazing incidence microperiodic mirrors. Using such mirrors, efficient phase-contrast imaging systems could be built for energies up to {approx}100 keV. In addition, a simple lithographic method is proposed for the production of the microperiodic x-ray mirrors based on the difference in the total reflection between a low-Z substrate and a high-Z film. Prototype mirrors fabricated with this method show promising characteristics in laboratory tests.

  14. Electrical capacitance volume tomography with high contrast dielectrics using a cuboid sensor geometry

    NASA Astrophysics Data System (ADS)

    Nurge, Mark A.

    2007-05-01

    An electrical capacitance volume tomography system has been created for use with a new image reconstruction algorithm capable of imaging high contrast dielectric distributions. The electrode geometry consists of two 4 × 4 parallel planes of copper conductors connected through custom built switch electronics to a commercially available capacitance to digital converter. Typical electrical capacitance tomography (ECT) systems rely solely on mutual capacitance readings to reconstruct images of dielectric distributions. This paper presents a method of reconstructing images of high contrast dielectric materials using only the self-capacitance measurements. By constraining the unknown dielectric material to one of two values, the inverse problem is no longer ill-determined. 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 aluminium structure inserted at different positions within the sensing region. Comparisons with standard two-dimensional ECT systems highlight the capabilities and limitations of the electronics and reconstruction algorithm.

  15. Electrical capacitance volume tomography of high contrast dielectrics using a cuboid geometry

    NASA Astrophysics Data System (ADS)

    Nurge, Mark A.

    An Electrical Capacitance Volume Tomography system has been created for use with a new image reconstruction algorithm capable of imaging high contrast dielectric distributions. The electrode geometry consists of two 4 x 4 parallel planes of copper conductors connected through custom built switch electronics to a commercially available capacitance to digital converter. Typical electrical capacitance tomography (ECT) systems rely solely on mutual capacitance readings to reconstruct images of dielectric distributions. This dissertation presents a method of reconstructing images of high contrast dielectric materials using only the self capacitance measurements. By constraining the unknown dielectric material to one of two values, the inverse problem is no longer ill-determined. 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. Comparisons with standard two dimensional ECT systems highlight the capabilities and limitations of the electronics and reconstruction algorithm.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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+.

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

    PubMed

    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

    2016-09-02

    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:Eu(3+) nanorods have been characterized by studying its structural, optical and magnetic properties. The advantage offered by photoluminescent imaging with Gd2O3:Eu(3+) 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:Eu(3+) nanorods were compared with the spherical nanoparticles of Gd2O3:Eu(3+).

  19. Diamond Turned High Precision PIAA Optics and Four Mirror PIAA System for High Contrast Imaging of Exo-planets

    NASA Technical Reports Server (NTRS)

    Balasubramanian, Kunjithapatham; Cady, Eric; Pueyo, Laurent; Ana, Xin; Shaklan, Stuart; Guyon, Olivier; Belikov, Ruslan

    2011-01-01

    Off-axis, high-sag PIAA optics for high contrast imaging present challenges in manufacturing and testing. With smaller form factors and consequently smaller surface deformations (< 80 microns), diamond turned fabrication of these mirrors becomes feasible. Though such a design reduces the system throughput, it still provides 2(lambda)D inner working angle. We report on the design, fabrication, measurements, and initial assessment of the novel PIAA optics in a coronagraph testbed. We also describe, for the first time, a four mirror PIAA coronagraph that relaxes apodizer requirements and significantly improves throughput while preserving the low-cost benefits.

  20. [Spatial contrast sensitivity in patients with high myopia after refraction lamellar keratoplasty].

    PubMed

    Shpak, A A; Medvedev, I V; Karamian, A A; Milova, S V

    1997-01-01

    Spatial contrast sensitivity (SCS) is one of the most important visual functions. SCS was examined in 23 patients (38 eyes) with high myopia before and after refraction lamellar keratoplasty (RLK) and in 21 healthy controls. Before surgery an appreciable (p < 0.01) reduction of SCS was observed in patients with high myopia in the entire range of spatial frequencies in comparison with the controls. After the operation the maximally corrected vision acuity was virtually unchanged, whereas the parameters of SCS somewhat increased for all frequencies, the increase being statistically reliable at frequencies of 0.23 to 3.75 and 15 cycles/degree. Hence, the studies demonstrated that changes in the topography of the cornea after refraction lamellar keratoplasty do not deteriorate the visual function.

  1. Carbofluoresceins and Carborhodamines as Scaffolds for High-Contrast Fluorogenic Probes

    PubMed Central

    2013-01-01

    Fluorogenic molecules are important tools for advanced biochemical and biological experiments. The extant collection of fluorogenic probes is incomplete, however, leaving regions of the electromagnetic spectrum unutilized. Here, we synthesize green-excited fluorescent and fluorogenic analogues of the classic fluorescein and rhodamine 110 fluorophores by replacement of the xanthene oxygen with a quaternary carbon. These anthracenyl “carbofluorescein” and “carborhodamine 110” fluorophores exhibit excellent fluorescent properties and can be masked with enzyme- and photolabile groups to prepare high-contrast fluorogenic molecules useful for live cell imaging experiments and super-resolution microscopy. Our divergent approach to these red-shifted dye scaffolds will enable the preparation of numerous novel fluorogenic probes with high biological utility. PMID:23557713

  2. Phase-contrast microscopy at high x-ray energy with a laboratory setup.

    PubMed

    Endrizzi, Marco; Vittoria, Fabio A; Diemoz, Paul C; Lorenzo, Rodolfo; Speller, Robert D; Wagner, Ulrich H; Rau, Christoph; Robinson, Ian K; Olivo, Alessandro

    2014-06-01

    We report on the design and realization of an x-ray imaging system for quantitative phase-contrast microscopy at high x-ray energy with laboratory-scale instrumentation. Phase and amplitude were separated quantitatively at x-ray energies up to 80 keV with micrometric spatial resolution. The accuracy of the results was tested against numerical simulations, and the spatial resolution was experimentally quantified by measuring a Siemens star phase object. This simple setup should find broad application in those areas of x-ray imaging where high energy and spatial resolution are simultaneously required and in those difficult cases where the sample contains materials with similar x-ray absorption.

  3. Race and Ethnic Differences in College Achievement: Does High School Attended Matter?

    PubMed Central

    Fletcher, Jason M.; Tienda, Marta

    2012-01-01

    This paper uses 10 years of enrollment data at four Texas public universities to examine whether, to what extent, and in what ways high school attended contributes to racial and ethnic differences in college achievement. Like previous studies, we show that controlling for observable pre-college achievement variables (e.g. test scores, class rank) shrinks, but does not eliminate, sizable racial differences in college achievement. Fixed-effects models that take into account differences across high schools that minority and nonminority youth attend largely eliminate, and often reverse, black-white and Hispanic-white gaps in several measures of college achievement. Our results, which are quite robust across universities of varying selectivity, illustrate how high school quality foments race and ethnic inequality in postsecondary achievement. Leveling inequities in the quality of high schools that minority students attend is a long-run agenda, but remediation programs that compensate for instructional shortfalls at low performing high schools may help close achievement gaps in the interim. PMID:23136447

  4. Race and Ethnic Differences in College Achievement: Does High School Attended Matter?

    PubMed

    Fletcher, Jason M; Tienda, Marta

    2010-01-01

    This paper uses 10 years of enrollment data at four Texas public universities to examine whether, to what extent, and in what ways high school attended contributes to racial and ethnic differences in college achievement. Like previous studies, we show that controlling for observable pre-college achievement variables (e.g. test scores, class rank) shrinks, but does not eliminate, sizable racial differences in college achievement. Fixed-effects models that take into account differences across high schools that minority and nonminority youth attend largely eliminate, and often reverse, black-white and Hispanic-white gaps in several measures of college achievement. Our results, which are quite robust across universities of varying selectivity, illustrate how high school quality foments race and ethnic inequality in postsecondary achievement. Leveling inequities in the quality of high schools that minority students attend is a long-run agenda, but remediation programs that compensate for instructional shortfalls at low performing high schools may help close achievement gaps in the interim.

  5. High-contrast ratio and long lifetime polymer electrochromic devices (ECDs)

    NASA Astrophysics Data System (ADS)

    Ning, Dai; Xu, Chunye; Liu, Lu; Kaneko, Calen; Taya, Minoru

    2005-05-01

    The preparation and characterization of a type of ECD which was based on a cathodic EC polymer film, Poly [3, 3-dimethyl-3, 4-dihydro-2H-thieno [3, 4-b][1, 4] dioxepine] (PProDOT-Me2) is reported. A typical device was constructed by sandwiching a gel electrolyte between a PProDOT-Me2 EC film deposited on Indium Tin oxide (ITO) coated glass and a counter electrode which was also ITO glass coated by a Vanadium oxide (V2O5) thin film. The ECD has been characterized. Device contrast ratio, measured as Ε%T, was equal to 60%, and ranged from 2% to 62% between the colored and bleached state measured at 580 nm. A lifetime of over 100,000 cycles between the fully oxidized and fully reduced state has been achieved with only 6% change in the transmittance. The switching speed of a 2.5cm x 2.5cm ECD could be reached in 1 second between the bleached and colored state. The device also has a long open circuit memory. It can remain in the bleached or colored state without being energized for 30 days, and the change in transmittance is less than 6% in colored state. The cyclic voltammetry method was used to detect the moisture content in the gel electrolyte. ECDs of various dimensions were also prepared, 2.5cm x 2.5cm, 7.5cm x 7.5cm, 15cm x 15cm and 30cm x 30cm. The largest scale EC polymer device achieved is 30cm x 30cm. Low sheet resistance ITO glass and a thin-film silver deposition frame were applied to overcome the electric potential drop across the ITO glass surface.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Broadband Performance of TPF's High-contrast Imaging Testbed: Modeling and Simulations

    NASA Technical Reports Server (NTRS)

    Sidick, Erkin; Kuhnert, Andreas C.; Trauger, John T.

    2006-01-01

    The broadband performance of the high-contrast imaging testbed (HCIT) at JPL is investigated through optical modeling and simulations. The analytical tool is an optical simulation algorithm developed by combining the HCIT's optical model with a speckle-nulling algorithm that operates directly on coronagraphic images, an algorithm identical to the one currently being used on the HCIT to actively suppress scattered light via a deformable mirror. It is capable of performing full three-dimensional end-to-end near-field diffraction analysis on the HCIT's optical system. By conducting speckle-nulling optimization, we clarify the HCIT's capability and limitations in terms of its broadband contrast performance under various realistic conditions. Considered cases include non-ideal occulting masks, such as a mask with optical density and wavelength dependent parasitic phase-delay errors (i.e., a not band-limited occulting mask) and the one with an optical-density profile corresponding to a measured, non-standard profile, as well as the independently measured phase errors of all optics. Most of the information gathered on the HCIT's optical components through measurement and characterization over the last several years at JPL has been used in this analysis to make the predictions as accurate as possible. The best contrast values predicted so far by our simulations obtainable on the HCIT illuminated with a broadband light having a bandwidth of 80nm and centered at 800nm wavelength are Cm=1.1x10-8 (mean) and C4=4.9x10-8 (at 4(lamda)/D), respectively. In this paper we report our preliminary findings about the broadband light performance of the HCIT.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. High Contrast Science Program for the Exo-C Space Telescope Mission

    NASA Astrophysics Data System (ADS)

    Stapelfeldt, Karl R.; Marley, Mark S.; Bryden, Geoffrey; Meadows, Victoria; Belikov, Ruslan; McElwain, Michael W.; Exo-C Science; Technology Definition Team

    2015-01-01

    Exo-C is a detailed study of the science capability, engineering design, technology requirements, and costing for a modest-aperture space telescope with an internal coronagraph that could directly image exoplanetary systems. During its three year mission, Exo-C will carry out imaging and spectroscopy over the wavelength range 0.45-1.0 um towards the following goals: 1) Characterize the atmospheres of at least a dozen known, nearby radial velocity planets. Exo-C spectra will diagnose their atmospheric composition and the presence of clouds, performing the first such measurements of cool giant exoplanets like those in our own solar system. 2) Conduct an imaging survey of at least 100 additional nearby stars down to ~3e-10 contrast, enabling the discovery of new exoplanets down to super-Earth sizes. Sub-Neptune and super-Earth planets are relatively common in the exoplanet population, but have no counterparts in our Solar System. Exo-C spectra will provide the first atmospheric characterization for these intriguing objects. 3) Image several hundred circumstellar disks, revealing structures induced by planetary perturbations and the time evolution of disk properties. If exozodi is low and a very stable telescope can be achieved, habitable zone planets down to Earth size might be detected in a small sample of nearby stars including the alpha Cen system. Science targets, observing protocols, and future work will be discussed.

  10. High speed X-ray phase contrast imaging of energetic composites under dynamic compression

    NASA Astrophysics Data System (ADS)

    Parab, Niranjan D.; Roberts, Zane A.; Harr, Michael H.; Mares, Jesus O.; Casey, Alex D.; Gunduz, I. Emre; Hudspeth, Matthew; Claus, Benjamin; Sun, Tao; Fezzaa, Kamel; Son, Steven F.; Chen, Weinong W.

    2016-09-01

    Fracture of crystals and frictional heating are associated with the formation of "hot spots" (localized heating) in energetic composites such as polymer bonded explosives (PBXs). Traditional high speed optical imaging methods cannot be used to study the dynamic sub-surface deformation and the fracture behavior of such materials due to their opaque nature. In this study, high speed synchrotron X-ray experiments are conducted to visualize the in situ deformation and the fracture mechanisms in PBXs composed of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals and hydroxyl-terminated polybutadiene binder doped with iron (III) oxide. A modified Kolsky bar apparatus was used to apply controlled dynamic compression on the PBX specimens, and a high speed synchrotron X-ray phase contrast imaging (PCI) setup was used to record the in situ deformation and failure in the specimens. The experiments show that synchrotron X-ray PCI provides a sufficient contrast between the HMX crystals and the doped binder, even at ultrafast recording rates. Under dynamic compression, most of the cracking in the crystals was observed to be due to the tensile stress generated by the diametral compression applied from the contacts between the crystals. Tensile stress driven cracking was also observed for some of the crystals due to the transverse deformation of the binder and superior bonding between the crystal and the binder. The obtained results are vital to develop improved understanding and to validate the macroscopic and mesoscopic numerical models for energetic composites so that eventually hot spot formation can be predicted.

  11. Physiological and biochemical responses to high Mn concentrations in two contrasting Populus cathayana populations.

    PubMed

    Lei, Yanbao; Korpelainen, Helena; Li, Chunyang

    2007-06-01

    We exposed the cuttings of Populus cathayana to Hoagland's solution containing four different manganese (Mn) concentrations (0, 0.1, 0.5 and 1mM) in a greenhouse to characterize the physiological and biochemical basis of Mn resistance in woody plants. Two contrasting populations of P. cathayana were used in our study, which were from the wet and dry climate regions in western China, respectively. The results showed that Mn treatments significantly decreased chlorophyll content and growth characteristics, including shoot height, basal diameter, biomass accumulation and total leaf area in the two populations. Mn treatments also significantly increased the levels of abscisic acid (ABA), polyamines and free amino acids especially proline (Pro), histidine (His) and phenylalanine (Phe) available for cellular signaling and heavy metal chelation. In addition, high Mn concentrations also caused oxidative stress indicated as the accumulation of hydrogen peroxide (H(2)O(2)) and malondialdehyde (MDA) contents. On the other hand, there were different responses to Mn stress between the two contrasting populations. Compared with the dry climate population, the wet climate population accumulated more Mn in plant tissues especially in leaves; it showed lower tolerance index and more pronounced decrease in growth and chlorophyll contents. The wet climate population not only accumulated less ABA, putrescine and free amino acids, but also exhibited lower activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX), thus suffering from more serious oxidative damage. Therefore, our results showed that the wet climate population was more susceptible to Mn stress than the dry climate population.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Miniaturized selective plane illumination microscopy for high-contrast in vivo fluorescence imaging.

    PubMed

    Engelbrecht, Christoph J; Voigt, Fabian; Helmchen, Fritjof

    2010-05-01

    Light-sheet-based fluorescence imaging techniques rely on simultaneous excitation of a single optical plane and thus permit high-contrast optically sectioned imaging of extended tissue samples. Here, we introduce a miniaturized fiber-optic implementation of a selective plane-illumination microscope (miniSPIM). The excitation light was delivered through a single-mode optical fiber, and a light-sheet was created with a cylindrical gradient-index lens and a right-angle microprism. Fluorescence emission was collected orthogonally to the light-sheet through a gradient-index lens assembly and a coherent fiber bundle. The end face of the fiber bundle was imaged onto a charge-coupled device camera. The spatial resolutions of the miniSPIM were 3.2 microm laterally and 5.1 microm axially. Images of fluorescent beads and neurons in mouse neocortex exhibited superior axial resolution and contrast in the miniSPIM-mode compared to images recorded in epi-illumination mode. The miniSPIM may thus enable novel in vivo imaging approaches.

  14. Long-Term Follow-Up of Patients at High Risk for Nephropathy After Contrast Exposure.

    PubMed

    Abaci, Okay; Harmankaya, Ozlem; Kocas, Betul; Kocas, Cuneyt; Bostan, Cem; Coskun, Ugur; Yildiz, Ahmet; Ersanli, Murat

    2015-07-01

    Contrast medium-induced acute kidney injury (CI-AKI) is associated with morbidity and mortality, but the long-term outcomes of patients who do not develop CI-AKI remain unknown. We assessed clinical end points during long-term follow-up in patients at high risk for nephropathy who did not develop CI-AKI. Patients (n = 135) with impaired renal function (estimated glomerular filtration rate: 30-60 mL/min/1.73 m(2)) were divided into 2 groups according to contrast media (CM) exposure. The primary end point of this study was a composite outcome measure of death or renal failure requiring dialysis. Multivariate analyses identified CM exposure to be independently associated with major adverse long-term outcomes (hazard ratio: 2.3; 95% confidence interval, 1.34-6.52; P = .018). Even when CM exposure does not cause CI-AKI in patients with impaired renal function, in the long term, primary end points occur more frequently in patients exposed to CM than in those with no CM exposure.

  15. Early Tumor Development Captured Through Nondestructive, High Resolution Differential Phase Contrast X-ray Imaging

    PubMed Central

    Beheshti, A.; Pinzer, B. R.; McDonald, J. T.; Stampanoni, M.; Hlatky, L.

    2014-01-01

    Although a considerable amount is known about molecular dysregulations in later stages of tumor progression, much less is known about the regulated processes supporting initial tumor growth. Insight into such processes can provide a fuller understanding of carcinogenesis, with implications for cancer treatment and risk assessment. Work from our laboratory suggests that organized substructure emerges during tumor formation. The goal here was to examine the feasibility of using state-of-the-art differential phase contrast X-ray imaging to investigate density differentials that evolve during early tumor development. To this end the beamline for TOmographic Microscopy and Coherent rAdiology experimenTs (TOMCAT) at the Swiss Light Source was used to examine the time-dependent assembly of substructure in developing tumors. Differential phase contrast (DPC) imaging based on grating interferometry as implemented with TOMCAT, offers sensitivity to density differentials within soft tissues and a unique combination of high resolution coupled with a large field of view that permits the accommodation of larger tissue sizes (1 cm in diameter), difficult with other imaging modalities. PMID:24125488

  16. Laboratory test of a polarimetry imaging subtraction system for the high-contrast imaging

    NASA Astrophysics Data System (ADS)

    Dou, Jiangpei; Ren, Deqing; Zhu, Yongtian; Zhang, Xi; Li, Rong

    2012-09-01

    We propose a polarimetry imaging subtraction test system that can be used for the direct imaging of the reflected light from exoplanets. Such a system will be able to remove the speckle noise scattered by the wave-front error and thus can enhance the high-contrast imaging. In this system, we use a Wollaston Prism (WP) to divide the incoming light into two simultaneous images with perpendicular linear polarizations. One of the images is used as the reference image. Then both the phase and geometric distortion corrections have been performed on the other image. The corrected image is subtracted with the reference image to remove the speckles. The whole procedure is based on an optimization algorithm and the target function is to minimize the residual speckles after subtraction. For demonstration purpose, here we only use a circular pupil in the test without integrating of our apodized-pupil coronagraph. It is shown that best result can be gained by inducing both phase and distortion corrections. Finally, it has reached an extra contrast gain of 50-times improvement in average, which is promising to be used for the direct imaging of exoplanets.

  17. Social Goals, Social Status, and Problem Behavior among Low-Achieving and High-Achieving Adolescents from Rural Schools

    ERIC Educational Resources Information Center

    Ludden, Alison Bryant

    2012-01-01

    The current research examines how social goals and perceptions of what is needed for social status at school relate to school misbehavior and substance use among rural adolescents (N = 683). Results indicate that social goals and perceptions of social status have differential links to problem behaviors depending upon adolescents' achievement.…

  18. Integrated Wavefront Correction and Bias Estimation for the High-Contrast Imaging of Exoplanets

    NASA Astrophysics Data System (ADS)

    Riggs, A. J. Eldorado

    Just over two decades ago the first planet outside our solar system was found, and thousands more have been discovered since. Nearly all these exoplanets were indirectly detected by sensing changes in their host stars' light. However, exoplanets must be directly imaged to determine their atmospheric compositions and the orbital parameters unavailable from only indirect detections. The main challenge of direct imaging is to observe stellar companions much fainter than the star and at small angular separations. Coronagraphy is one method of suppressing stellar diffraction to provide high star-to-planet contrast, but coronagraphs are extremely sensitive to quasi-static aberrations in the optical system. Active correction of the stellar wavefront is performed with deformable mirrors to recover high-contrast regions in the image. Estimation and control of the stellar electric field is performed iteratively in the camera's focal plane to avoid non-common path aberrations arising from a separate pupil sensor. Estimation can thus be quite time consuming because it requires several high-contrast intensity images per correction iteration. This thesis focuses on efficient focal plane wavefront correction (FPWC) for coronagraphy. Time is a precious commodity for a space telescope, so there is a strong incentive to reduce the total exposure time required for focal plane wavefront estimation. Much of our work emphasizes faster, more robust estimation via Kalman filtering, which optimally combines prior data with new measurements. The other main contribution of this thesis is a paradigm shift in the use of estimation images. Time for FPWC has generally been considered to be lost overhead, but we demonstrate that estimation images can be used for the detection and characterization of exoplanets and disks. These science targets are incoherent with their host stars, so we developed and implemented an iterated extended Kalman filter (IEKF) for simultaneous estimation of the stellar

  19. The Impact of Block Scheduling on Student Achievement, Attendance, and Discipline at the High School Level

    ERIC Educational Resources Information Center

    Williams, Charles, Jr.

    2011-01-01

    The purpose of this study was to determine the impact block scheduling has on (a) student academic achievement, discipline, and attendance, and (b) administrator, teacher, and student perceptions. The study compared 2005-2010 data from a high school utilizing the A/B block schedule and a high school under a traditional schedule, in one suburban…

  20. The Role of Teachers at University: What Do High Achiever Students Look for?

    ERIC Educational Resources Information Center

    Monteiro, Silvia; Almeida, Leandro S.; Vasconcelos, Rosa M.

    2012-01-01

    The perceptions of students about their teachers have interested the academic and scientific community, regarding the improvement of the quality of higher education. This paper presents data obtained from interviews conducted with ten high achiever engineering students and focuses on the characteristics of teachers that are highly valued by the…

  1. Study-Orientation of High and Low Academic Achievers at Secondary Level in Pakistan

    ERIC Educational Resources Information Center

    Sarwar, Muhammad; Bashir, Muhammad; Khan, Muhammad Naemullah; Khan, Muhammad Saeed

    2009-01-01

    The study orientation of low and high academic achievers was compared, measured through a self-developed study orientation scale (SOS) primarily based on 47 items comparing study habits and attitude. Students' marks obtained in the 10th grade Examination determined the measure of academic performance. The analysis revealed that the high achievers…

  2. What Works Clearinghouse Quick Review: "Expanding College Opportunities for High-Achieving, Low Income Students"

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2013

    2013-01-01

    This study examined the effects of providing low-income, high-achieving high school seniors with college application guidance and information about the costs of college. The "application guidance" included information about deadlines and requirements for college applications at nearby institutions, at the state's flagship institution, and at in-…

  3. The Relationship between Self-Efficacy and Achievement in At-Risk High School Students

    ERIC Educational Resources Information Center

    Gold, Jarrett Graham

    2010-01-01

    The focus of this quantitative survey study was the examination of the relationship between self-efficacy and academic achievement in 164 at-risk high school students. The study used Bandura's self-efficacy as the theoretical framework. The research questions involved understanding the levels of self-efficacy in at-risk high school students and…

  4. The Contribution of Limbic Learning Aptitude to Achievement in High School. Final Report.

    ERIC Educational Resources Information Center

    Ax, Albert F.; And Others

    Achievement in earning grades in high school was resolved into its intellectual and motivational components. This study employed tests of I.Q., personality inventories and classical and operant conditioning of autonomic nervous system controlled variables. Eleven procedures were given to 99 Black inner city high school seniors. Six physiological…

  5. The Effects of Modeling Instruction on High School Physics Academic Achievement

    ERIC Educational Resources Information Center

    Wright, Tiffanie L.

    2012-01-01

    The purpose of this study was to explore whether Modeling Instruction, compared to traditional lecturing, is an effective instructional method to promote academic achievement in selected high school physics classes at a rural middle Tennessee high school. This study used an "ex post facto," quasi-experimental research methodology. The…

  6. Improving High School Students' Mathematics Achievement through the Use of Motivational Strategies.

    ERIC Educational Resources Information Center

    Portal, Jamie; Sampson, Lisa

    This report describes a program for motivating students in mathematics in order to improve achievement at the high school level. The targeted population consisted of high school students in a middle class community located in a suburb of a large metropolitan area. The problems of underachievement were documented through data collected from surveys…

  7. Coping with High-Achieving Transnationalist Immigrant Students: The Experience of Israeli Teachers

    ERIC Educational Resources Information Center

    Eisikovits, Rivka A.

    2008-01-01

    Little attention has been paid to teacher attitudes toward high-achieving culturally diverse student groups. This in-depth study focuses on the experience of Israeli teachers who tell the story of a decade and a half of educational work with their highly motivated, academically successful immigrant students from the Former Soviet Union. The paper…

  8. 10 Strategies for Raising Achievement and Improving High School Completion Rates

    ERIC Educational Resources Information Center

    Bottoms, Gene

    2004-01-01

    No state can afford to have the percentage of young people who are failing to finish high school remain at the present levels nor can they afford to ease the standards. This document discusses the following 10 strategies that states can implement to raise achievement and increase high school completion rates: (1) Initiate a transition program for…

  9. Emotional Intelligence as a Predictor of Leadership of Kuwaiti High and Low Achieving 11th Graders

    ERIC Educational Resources Information Center

    Alnabhan, Mousa

    2010-01-01

    The current study examined the association between emotional intelligence (EI) and the Leadership components (L) of high school students in the state of Kuwait. The possibility of predicting each leadership component via emotional intelligence components was investigated for high and low achievers. A sample of 11th grade students from Kuwaiti…

  10. Dual Enrollment Programs: A Comparative Study of High School Students' College Academic Achievement at Different Settings

    ERIC Educational Resources Information Center

    Flores, Agnes L. Acker

    2012-01-01

    The "ex post facto" causal-comparative study examined the academic achievement of high school students who took their dual credit English or mathematics college credit-bearing course in two different environments, namely, the college setting and the high school setting. Due to non-experimental nature of the study, no causal inferences…

  11. Classroom Environment, Instructional Resources, and Teaching Differences in High-Performing Kentucky Schools with Achievement Gaps.

    ERIC Educational Resources Information Center

    Meehan, Merrill L.; Cowley, Kimberly S.; Schumacher, Debbie; Hauser, Brenda; Croom, Nona D. M.

    This study examined differences at the classroom level between Kentucky schools with minimum versus large gaps in academic achievement between particular groups of students. Data were gathered via observations of 213 classrooms at 18 elementary, middle, and high schools. Although all the schools were identified as high-performing in terms of…

  12. A Case Study of 21st Century Skills in High Achieving Elementary Schools in Pennsylvania

    ERIC Educational Resources Information Center

    Egnor, Gregory P.

    2013-01-01

    This study examines if practices that advocate for 21st century skills are in conflict with the mandates of NCLB. Interviews with influential school leaders of high achieving elementary schools focused on collecting data about 21st century skills. This study was designed to (a) Determine if 21st century skills are addressed in high achieving…

  13. Small Classes in the Early Grades, Academic Achievement, and Graduating From High School

    ERIC Educational Resources Information Center

    Finn, Jeremy D.; Gerber, Susan B.; Boyd-Zaharias, Jayne

    2005-01-01

    This investigation addressed 3 questions about the long-term effects of early school experiences: (a) Is participation in small classes in the early grades (K-3) related to high school graduation? (b) Is academic achievement in K-3 related to high school graduation? (c) If class size is related to graduation, is the relationship explained by the…

  14. The Relationship between Thinking Style Differences and Career Choices for High-Achieving Students

    ERIC Educational Resources Information Center

    Kim, Mihyeon

    2011-01-01

    The intent of this study was to present information about high-achieving students' career decision making associated with thinking styles. We gathered data from two International Baccalaureate (IB) programs and a Governor's School Program with a sample of 209 high-school students. The findings of this study demonstrated that the effect of program…

  15. Experiment and simulation of novel liquid crystal plasma mirrors for high contrast, intense laser pulses

    DOE PAGES

    Poole, P. L.; Krygier, A.; Cochran, G. E.; ...

    2016-08-25

    Here, we describe the first demonstration of plasma mirrors made using freely suspended, ultra-thin films formed dynamically and in-situ. We also present novel particle-in-cell simulations that for the first time incorporate multiphoton ionization and dielectric models that are necessary for describing plasma mirrors. Dielectric plasma mirrors are a crucial component for high intensity laser applications such as ion acceleration and solid target high harmonic generation because they greatly improve pulse contrast. We use the liquid crystal 8CB and introduce an innovative dynamic film formation device that can tune the film thickness so that it acts as its own antireflection coating.more » Films can be formed at a prolonged, high repetition rate without the need for subsequent realignment. High intensity reflectance above 75% and low-field reflectance below 0.2% are demonstrated, as well as initial ion acceleration experimental results that demonstrate increased ion energy and yield on shots cleaned with these plasma mirrors.« less

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Short Term Reproducibility of a High Contrast 3-D Isotropic Optic Nerve Imaging Sequence in Healthy Controls

    PubMed Central

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

    2016-01-01

    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. PMID:27175048

  19. Short Term Reproducibility of a High Contrast 3-D Isotropic Optic Nerve Imaging Sequence in Healthy Controls.

    PubMed

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

    2016-02-27

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The coronagraph instrument on the Wide-Field Infrared Survey Telescope-Astrophysics-Focused Telescope Asset (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 in advance of the mission. A series of milestones were set to track the development of the technologies required for the instrument; 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.

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. An infrared small target detection algorithm based on high-speed local contrast method

    NASA Astrophysics Data System (ADS)

    Cui, Zheng; Yang, Jingli; Jiang, Shouda; Li, Junbao

    2016-05-01

    Small-target detection in infrared imagery with a complex background is always an important task in remote sensing fields. It is important to improve the detection capabilities such as detection rate, false alarm rate, and speed. However, current algorithms usually improve one or two of the detection capabilities while sacrificing the other. In this letter, an Infrared (IR) small target detection algorithm with two layers inspired by Human Visual System (HVS) is proposed to balance those detection capabilities. The first layer uses high speed simplified local contrast method to select significant information. And the second layer uses machine learning classifier to separate targets from background clutters. Experimental results show the proposed algorithm pursue good performance in detection rate, false alarm rate and speed simultaneously.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. High Contrast Internal and External Coronagraph Masks Produced by Various Techniques

    NASA Technical Reports Server (NTRS)

    Balasubramanian, Kunjithapatha; Wilson, Daniel; White, Victor; Muller, Richard; Dickie, Matthew; Yee, Karl; Ruiz, Ronald; Shaklan, Stuart; Cady, Eric; Kern, Brian; Belikov, Ruslan; Guyon, Olivier; Kasdin, N. Jeremy

    2013-01-01

    Masks for high contrast internal and external coronagraphic imaging require a variety of masks depending on different architectures to suppress star light. Various fabrication technologies are required to address a wide range of needs including gradient amplitude transmission, tunable phase profiles, ultra-low reflectivity, precise small scale features, and low-chromaticity. We present the approaches employed at JPL to produce pupil plane and image plane coronagraph masks, and lab-scale external occulter type masks by various techniques including electron beam, ion beam, deep reactive ion etching, and black silicon technologies with illustrative examples of each. Further development is in progress to produce circular masks of various kinds for obscured aperture telescopes.

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

    NASA Technical Reports Server (NTRS)

    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.

  7. Nulling interferometers for space-based high contrast visible imaging and measurement of exoplanetary environments

    NASA Astrophysics Data System (ADS)

    Hicks, Brian Andrew

    This dissertation presents the legacy, theory, design, characterization, and application prospects of a fully symmetric monolithic nulling interferometer (nuller). A nuller's function is to destructively interfere light originating from a bright, on-axis, unresolved source in order to lower its contrast with faint, off-axis sources of light in the field of view. The primary application lies in astronomical instrumentation, serving as an enabling technology for directly imaging exoplanets and measuring exozodiacal dust and debris disks, the planetary system evolutionary components around nearby stars. Typical on-sky planet/star flux ratios are 1:109 or less in the visible. Mitigating this contrast is key to spectroscopic study of exoplanets, which aims to characterize exoplanetary atmospheres and potentially locate biosignatures on exo-Earths. Within the past decade, adaptive optics-equipped breadboard demonstrations of nullers and other coronagraphs have shown the capability to image nearby (≤ 30 lightyears) extrasolar analogs to Jupiter with a 0.5 meter diameter telescope in the visible. The quiet laboratory environments that have been produced to demonstrate this capability do not reflect those of typical ground-based observatories where thermal drifts perturb optical alignment and atmospheric turbulence perturbs the source wavefront. Space-based platforms circumvent the atmosphere problem, but are still subjected to thermal instabilities and their associated risks. Robust optical systems must be designed and flight-tested in order to address such risks and provide grounds for their inclusion in the design of future exo-Earth imaging satellites. Sub-orbital platforms such as sounding rockets and high-altitude balloons provide a rapid, low-cost means of providing heritage for such optical systems while also delivering significant scientific results. The primary risk inherent with these platforms are harsh transient environmental conditions, for which, similar to

  8. High relaxivity MRI contrast agents part 2: Optimization of inner- and second-sphere relaxivity

    PubMed Central

    Jacques, Vincent; Dumas, Stephane; Sun, Wei-Chuan; Troughton, Jeffrey S.; Greenfield, Matthew T.; Caravan, Peter

    2011-01-01

    Rationale and objectives The observed relaxivity of gadolinium based contrast agents has contributions from the water molecule(s) that bind directly to the gadolinium ion (inner-sphere water), long lived water molecules and exchangeable protons that make up the second-sphere of coordination, and water molecules that diffuse near the contrast agent (outer-sphere). Inner- and second-sphere relaxivity can both be increased by optimization of the lifetimes of the water molecules and protons in these coordination spheres, the rotational motion of the complex, and the electronic relaxation of the gadolinium ion. We sought to identify new high relaxivity contrast agents by systematically varying the donor atoms that bind directly to gadolinium to increase inner-sphere relaxivity and concurrently including substituents that influence the second-sphere relaxivity. Methods Twenty GdDOTA derivatives were prepared and their relaxivity determined in presence and absence of human serum albumin as a function of temperature and magnetic field. Data was analyzed to extract the underlying molecular parameters influencing relaxivity. Each compound had a common albumin-binding group and an inner-sphere donor set comprising the 4 tertiary amine N atoms from cyclen, an α-substituted acetate oxygen atom, two amide oxygen atoms, an inner-sphere water oxygen atom, and a variable donor group. Each amide nitrogen was substituted with different groups to promote hydrogen bonding with second-sphere water molecules. Results Relaxivites at 0.47T and 1.4T, 37 °C, in serum albumin ranged from 16.0 to 58.1 mM−1s−1 and from 12.3 to 34.8 mM−1s−1 respectively. The reduction of inner-sphere water exchange typical of amide donor groups could be offset by incorporating a phosphonate or phenolate oxygen atom donor in the first coordination sphere resulting in higher relaxivity. Amide nitrogen substitution with pendant phosphonate or carboxylate groups increased relaxivity by as much as 88

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

    SciTech Connect

    Albertazzi, B.; Chen, S. N.; Fuchs, J.; Antici, P.; Böker, J.; Swantusch, M.; Willi, O.; Borghesi, M.; Breil, J.; Feugeas, J. L.; Nicolaï, Ph.; Tikhonchuk, V. T.; D'Humières, E.; Dervieux, V.; Nakatsutsumi, M.; Romagnagni, L.; Lancia, L.; Shepherd, R.; Sentoku, Y.; Starodubtsev, M.; and others

    2015-12-15

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

  10. Does Homogeneous Ability Grouping for High School Honors English Instruction Benefit the High Achiever?

    ERIC Educational Resources Information Center

    Hostetter, Douglas Paul

    2013-01-01

    Public schools are examining their policies and instructional practices to address the achievement gap exposed by the reporting requirements of NCLB (Wenglinski, 2004). As accountability measures and stakes rise, there is a call for an improved use of scientific evidence to inform educational policymaking (Wiseman, 2010). In terms of the…

  11. Academic achievement and career choice in science: Perceptions of African American urban high school students

    NASA Astrophysics Data System (ADS)

    Jones, Sheila Kay

    2007-12-01

    Low test scores in science and fewer career choices in science among African American high school students than their White counterparts has resulted in lower interest during high school and an underrepresentation of African Americans in science and engineering fields. Reasons for this underachievement are not known. This qualitative study used a grounded theory methodology to examine what influence parental involvement, ethnic identity, and early mentoring had on the academic achievement in science and career choice in science of African American urban high school 10th grade students. Using semi-structured open-ended questions in individual interviews and focus groups, twenty participants responded to questions about African American urban high school student achievement in science and their career choice in science. The median age of participants was 15 years; 85% had passed either high school biology or physical science. The findings of the study revealed influences and interactions of selected factors on African American urban high school achievement in science. Sensing potential emerged as the overarching theme with six subthemes; A Taste of Knowledge, Sounds I Hear, Aromatic Barriers, What Others See, The Touch of Others, and The Sixth Sense. These themes correlate to the natural senses of the human body. A disconnect between what science is, their own individual learning and success, and what their participation in science could mean for them and the future of the larger society. Insight into appropriate intervention strategies to improve African American urban high school achievement in science was gained.

  12. High-contrast fluorescence microscopy for a biomolecular analysis based on polarization techniques using an optical interference mirror slide.

    PubMed

    Yasuda, Mitsuru; Akimoto, Takuo

    2014-12-01

    Fluorescence microscopy with an improved contrast for fluorescence images is developed using an optical interference mirror (OIM) slide, which can enhance the fluorescence from a fluorophore as a result of the double interference of the excitation light and emission light. To improve the contrast of a fluorescence image using an OIM slide, a linearly-polarized excitation light was employed, and the fluorescence emission polarized perpendicular to the polarization of the excitation light was detected. The image contrast with this optical system was improved 110-fold for rhodamine B spotted on the OIM, in comparison with a glass slide using a general fluorescence microscopy optical system. Moreover, a 24-fold improvement of the image contrast was achieved for the detection of Cy3-labeled streptavidin bound to immobilize biotin.

  13. Patterns of Self-Regulation: Patterns of Self-Regulatory Strategy Use among Low-Achieving and High-Achieving University Students

    ERIC Educational Resources Information Center

    Ruban, Lilia; Reis, Sally M.

    2006-01-01

    The present mixed-methods study attempts to provide insights into the nature, idiosyncrasies, and inter- and intra-individual patterns of academic self-regulatory strategy use among two different populations of university students. Low-achieving (n = 49) and high-achieving students (n = 131) described their self-regulatory strategy use in their…

  14. High contrast microstructural visualization of natural acellular matrices by means of phase-based x-ray tomography

    NASA Astrophysics Data System (ADS)

    Hagen, Charlotte K.; Maghsoudlou, Panagiotis; Totonelli, Giorgia; Diemoz, Paul C.; Endrizzi, Marco; Rigon, Luigi; Menk, Ralf-Hendrik; Arfelli, Fulvia; Dreossi, Diego; Brun, Emmanuel; Coan, Paola; Bravin, Alberto; de Coppi, Paolo; Olivo, Alessandro

    2015-12-01

    Acellular scaffolds obtained via decellularization are a key instrument in regenerative medicine both per se and to drive the development of future-generation synthetic scaffolds that could become available off-the-shelf. In this framework, imaging is key to the understanding of the scaffolds’ internal structure as well as their interaction with cells and other organs, including ideally post-implantation. Scaffolds of a wide range of intricate organs (esophagus, lung, liver and small intestine) were imaged with x-ray phase contrast computed tomography (PC-CT). Image quality was sufficiently high to visualize scaffold microarchitecture and to detect major anatomical features, such as the esophageal mucosal-submucosal separation, pulmonary alveoli and intestinal villi. These results are a long-sought step for the field of regenerative medicine; until now, histology and scanning electron microscopy have been the gold standard to study the scaffold structure. However, they are both destructive: hence, they are not suitable for imaging scaffolds prior to transplantation, and have no prospect for post-transplantation use. PC-CT, on the other hand, is non-destructive, 3D and fully quantitative. Importantly, not only do we demonstrate achievement of high image quality at two different synchrotron facilities, but also with commercial x-ray equipment, which makes the method available to any research laboratory.

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

    NASA Astrophysics Data System (ADS)

    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. PIAA Coronagraph Development at NASA Ames: High Contrast Laboratory Demonstration at 2 l/D

    NASA Astrophysics Data System (ADS)

    Belikov, Ruslan; Pluzhnik, E.; Witteborn, F. C.; Lynch, D. H.; Greene, T. P.; Zell, P. T.; Balasubramanian, K.; Guyon, O.

    2011-01-01

    Coronagraph technology is advancing and promises to directly image and spectrally characterize extrasolar Earth-like planets in the foreseeable future (such as the 2020 decade) with a telescope as small as 1.5m. A small Explorer-sized telescope can also be launched in the 2010 decade capable of seeing debris disks as small as 10s of zodis and potentially a few large planets. The Phase Induced Amplitude Apodization (PIAA) coronagraph makes such aggressive performance possible. We report on the latest results from a testbed at NASA Ames that is focused on developing and testing the PIAA coronagraph. This laboratory facility was built in 2008 and is designed to be flexible, operated in an actively thermally stabilized air environment, and to complement collaborative efforts at NASA JPL's High Contrast Imaging Testbed. For our wavefront control we are using small Micro-Electro-Mechanical-System deformable mirrors (MEMS DMs), which promise to reduce the size of the beam and overall instrument, a consideration that becomes very important for small telescopes. We describe our lab efforts and results, which include: the operation of our new active thermal control system; the demonstration of 5.4x10-8 (at time of this writing) average raw contrast in a dark zone from 2.0 - 5.2 λ/D in monochromatic light with a refractive PIAA system; preliminary results with an innovative low-cost set of reflective PIAA from JPL; preliminary results with a set of next-generation reflective PIAA built by Tinsley and designed to have the best theoretical broadband performance so far; and finally, an innovative design for a chromatically compensated focal plane occulter that promises to enhance broadband performance by matching the wavelength-dependent inner working angle of coronagraphs such as PIAA.

  17. High-Accuracy Ultrasound Contrast Agent Detection Method for Diagnostic Ultrasound Imaging Systems.

    PubMed

    Ito, Koichi; Noro, Kazumasa; Yanagisawa, Yukari; Sakamoto, Maya; Mori, Shiro; Shiga, Kiyoto; Kodama, Tetsuya; Aoki, Takafumi

    2015-12-01

    An accurate method for detecting contrast agents using diagnostic ultrasound imaging systems is proposed. Contrast agents, such as microbubbles, passing through a blood vessel during ultrasound imaging are detected as blinking signals in the temporal axis, because their intensity value is constantly in motion. Ultrasound contrast agents are detected by evaluating the intensity variation of a pixel in the temporal axis. Conventional methods are based on simple subtraction of ultrasound images to detect ultrasound contrast agents. Even if the subject moves only slightly, a conventional detection method will introduce significant error. In contrast, the proposed technique employs spatiotemporal analysis of the pixel intensity variation over several frames. Experiments visualizing blood vessels in the mouse tail illustrated that the proposed method performs efficiently compared with conventional approaches. We also report that the new technique is useful for observing temporal changes in microvessel density in subiliac lymph nodes containing tumors. The results are compared with those of contrast-enhanced computed tomography.

  18. 2×2 dominant achievement goal profiles in high-level swimmers.

    PubMed

    Fernandez-Rio, Javier; Cecchini Estrada, Jose A; Mendez-Giménez, Antonio; Fernández-Garcia, Benjamín; Saavedra, Pablo

    2014-01-01

    The goal of this study was to assess achievement goal dominance, self-determined situational motivation and competence in high-level swimmers before and after three training sessions set at different working intensities (medium, sub-maximal and maximal). Nineteen athletes (males, n=9, 18.00±2.32 years; females, n=10, 16.30±2.01 years, range = 14-18) agreed to participate. They completed a questionnaire that included the Dominant Achievement Goal assessment instrument, the 2×2 Achievement Goals Questionnaire for Sport (AGQ-S), The Situational Motivation Scale (SIMS) and the Competence subscale of the Basic Psychological Needs in Exercise questionnaire (BPNES). Results indicated that participants overwhelmingly showed mastery-approach achievement goal dominance, and it remained stable at the conclusion of the different training sessions under all intensity levels. This profile was positively correlated to self-determined situational motivation and competence. However, swimmers' feelings of competence increased only after the medium intensity level training session. After the completion of the maximal intensity training session, swimmers' self-determined motivation was significantly lower compared to the other two training sessions, which could be caused by a temporary period of burnout. Results indicated that high-level swimmers had a distinct mastery-approach dominant achievement goal profile that was not affected by the workload of the different training sessions. They also showed high levels of self-determined situational motivation and competence. However, heavy workloads should be controlled because they can cause transitory burnout.

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

    PubMed

    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).

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  2. Training to improve contrast sensitivity in amblyopia: correction of high-order aberrations

    PubMed Central

    Liao, Meng; Zhao, Haoxing; Liu, Longqian; Li, Qian; Dai, Yun; Zhang, Yudong; Zhou, Yifeng

    2016-01-01

    Perceptual learning is considered a potential treatment for amblyopia even in adult patients who have progressed beyond the critical period of visual development because adult amblyopes retain sufficient visual plasticity. When perceptual learning is performed with the correction of high-order aberrations (HOAs), a greater degree of neural plasticity is present in normal adults and those with highly aberrated keratoconic eyes. Because amblyopic eyes show more severe HOAs than normal eyes, it is interesting to study the effects of HOA-corrected visual perceptual learning in amblyopia. In the present study, we trained twenty-six older child and adult anisometropic amblyopes while their HOAs were corrected using a real-time closed-loop adaptive optics perceptual learning system (AOPL). We found that adaptive optics (AO) correction improved the modulation transfer functions (MTFs) and contrast sensitivity functions (CSFs) of older children and adults with anisometropic amblyopia. When perceptual learning was performed with AO correction of the ocular HOAs, the improvements in visual function were not only demonstrated in the condition with AO correction but were also maintained in the condition without AO correction. Additionally, the learning effect with AO correction was transferred to the untrained visual acuity and fellow eyes in the condition without AO correction. PMID:27752122

  3. THE TRENDS HIGH-CONTRAST IMAGING SURVEY. II. DIRECT DETECTION OF THE HD 8375 TERTIARY

    SciTech Connect

    Crepp, Justin R.; Johnson, John Asher; Yantek, Scott M.; Howard, Andrew W.; Marcy, Geoff W.; Isaacson, Howard; Fischer, Debra A.; Wright, Jason T.; Feng Ying

    2013-07-01

    We present the direct imaging detection of a faint tertiary companion to the single-lined spectroscopic binary HD 8375 AB. Initially noticed as an 53 m s{sup -1} yr{sup -1} Doppler acceleration by Bowler et al., we have obtained high-contrast adaptive optics observations at Keck using NIRC2 that spatially resolve HD 8375 C from its host(s). Astrometric measurements demonstrate that the companion shares a common proper-motion. We detect orbital motion in a clockwise direction. Multiband relative photometry measurements are consistent with an early M-dwarf spectral type ({approx}M1V). Our combined Doppler and imaging observations place a lower-limit of m {>=} 0.297 M{sub Sun} on its dynamical mass. We also provide a refined orbit for the inner pair using recent radial velocity measurements obtained with the High Resolution Echelle Spectrometer. HD 8375 is one of many triple-star systems that are apparently missing in the solar neighborhood.

  4. High-throughput 3D tracking of bacteria on a standard phase contrast microscope

    NASA Astrophysics Data System (ADS)

    Taute, K. M.; Gude, S.; Tans, S. J.; Shimizu, T. S.

    2015-11-01

    Bacteria employ diverse motility patterns in traversing complex three-dimensional (3D) natural habitats. 2D microscopy misses crucial features of 3D behaviour, but the applicability of existing 3D tracking techniques is constrained by their performance or ease of use. Here we present a simple, broadly applicable, high-throughput 3D bacterial tracking method for use in standard phase contrast microscopy. Bacteria are localized at micron-scale resolution over a range of 350 × 300 × 200 μm by maximizing image cross-correlations between their observed diffraction patterns and a reference library. We demonstrate the applicability of our technique to a range of bacterial species and exploit its high throughput to expose hidden contributions of bacterial individuality to population-level variability in motile behaviour. The simplicity of this powerful new tool for bacterial motility research renders 3D tracking accessible to a wider community and paves the way for investigations of bacterial motility in complex 3D environments.

  5. High IQ Is Sufficient to Explain the High Achievements in Math and Science of the East Asian Peoples

    ERIC Educational Resources Information Center

    Lynn, Richard

    2010-01-01

    It is argued that it is unnecessary to propose that Confucian values explain the high achievements in math and science of the North East Asian peoples, and that these can be satisfactorily and more parsimoniously be explained by their high IQs.

  6. "It's a Way of Life for Us": High Mobility and High Achievement in Department of Defense Schools.

    ERIC Educational Resources Information Center

    Smrekar, Claire E.; Owens, Debra E.

    2003-01-01

    Examines the academic performance of students in U.S. Department of Defense Education Activity (DoDEA) schools, which have high student mobility. Some observers contend that these students' high achievement is a function of their middle class family and community characteristics. Asserts that DoDEA schools simultaneously "do the right…

  7. Modifying the size distribution of microbubble contrast agents for high-frequency subharmonic imaging

    PubMed Central

    Shekhar, Himanshu; Rychak, Joshua J.; Doyley, Marvin M.

    2013-01-01

    Purpose: Subharmonic imaging is of interest for high frequency (>10 MHz) nonlinear imaging, because it can specifically detect the response of ultrasound contrast agents (UCA). However, conventional UCA produce a weak subharmonic response at high frequencies, which limits the sensitivity of subharmonic imaging. We hypothesized that modifying the size distribution of the agent can enhance its high-frequency subharmonic response. The overall goal of this study was to investigate size-manipulated populations of the agent to determine the range of sizes that produce the strongest subharmonic response at high frequencies (in this case, 20 MHz). A secondary goal was to assess whether the number or the volume-weighted size distribution better represents the efficacy of the agent for high-frequency subharmonic imaging. Methods: The authors created six distinct agent size distributions from the native distribution of a commercially available UCA (Targestar-P®). The median (number-weighted) diameter of the native agent was 1.63 μm, while the median diameters of the size-manipulated populations ranged from 1.35 to 2.99 μm. The authors conducted acoustic measurements with native and size-manipulated agent populations to assess their subharmonic response to 20 MHz excitation (pulse duration 1.5 μs, pressure amplitudes 100–398 kPa). Results: The results showed a considerable difference between the subharmonic response of the agent populations that were investigated. The subharmonic response peaked for the agent population with a median diameter of 2.15 μm, which demonstrated a subharmonic signal that was 8 dB higher than the native agent. Comparing the subharmonic response of different UCA populations indicated that microbubbles with diameters between 1.3 and 3 μm are the dominant contributors to the subharmonic response at 20 MHz. Additionally, a better correlation was observed between the subharmonic response of the agent and the number-weighted size-distribution (R2

  8. Effects of Part-Time Work on School Achievement During High School

    ERIC Educational Resources Information Center

    Singh, Kusum; Chang, Mido; Dika, Sandra

    2007-01-01

    The authors explored the effects of part-time work on school achievement during high school. To estimate the true effects of part-time work on school grades, the authors included family background, students' educational aspirations, and school engagement as controls. Although a substantial literature exists on the relationship of part-time work…

  9. The Federal Transformation Intervention Model in Persistently Lowest Achieving High Schools: A Mixed-Methods Study

    ERIC Educational Resources Information Center

    Le Patner, Michelle B.

    2012-01-01

    This study examined the American Recovery and Reinvestment Act federal mandate of the Transformation Intervention Model (TIM) outlined by the School Improvement Grant, which was designed to turn around persistently lowest achieving schools. The study was conducted in four high schools in a large Southern California urban district that selected the…

  10. Balancing Dreams and Realities: The College Choice Process for High-Achieving Latinas

    ERIC Educational Resources Information Center

    Hernández, Ebelia

    2015-01-01

    This study's narratives of 17 high-achieving Latinas revealed how their college choice was a constant balancing of individual and family expectations, being "close, but far enough away," and "getting your money's worth." With the use of critical race theory, further analysis revealed the influence of "familismo" on…

  11. Fostering the Promise of High Achieving Mathematics Students through Curriculum Differentiation

    ERIC Educational Resources Information Center

    Zmood, Simone

    2014-01-01

    Recent research suggests some teachers may not have a wide range of teaching and learning strategies for their most proficient mathematics students, which could impact on these students' learning and ongoing improvement in performance. This paper outlines the different drivers of high achievement and explores the main curriculum differentiation…

  12. Being Labeled "Nerd": Factors that Influence the Social Acceptance of High-Achieving Students

    ERIC Educational Resources Information Center

    Rentzsch, Katrin; Schutz, Astrid; Schroder-Abe, Michela

    2011-01-01

    The present investigation addresses the question of whether certain factors can protect high-achieving students at risk for being labeled a nerd against devaluation. In 2 studies, 125 and 317 students from Grade 8 evaluated vignettes describing average students and students who were called "nerds." Results indicate that being modest…

  13. Conflicts and Communication between High-Achieving Chinese American Adolescents and Their Parents

    ERIC Educational Resources Information Center

    Qin, Desiree Baolian; Chang, Tzu-Fen; Han, Eun-Jin; Chee, Grace

    2012-01-01

    Drawing on in-depth interview data collected on 18 high-achieving Chinese American students, the authors examine domains of acculturation-based conflicts, parent and child internal conflicts, and conflict resolution in their families. Their analyses show that well-established negative communication patterns in educational expectations, divergent…

  14. The College-Choice Process of High Achieving Freshmen: A Comparative Case Study

    ERIC Educational Resources Information Center

    Dale, Amanda

    2010-01-01

    The purpose of this study was to examine the college-choice process of high achieving students. Employing current literature and previous research, it combined current models of college choice and the influential factors identified throughout the literature while utilizing the concept of bounded rationality to create a conceptual framework to…

  15. Examining the Relationship between Selected Variables and the Academic Achievement of African American High School Students

    ERIC Educational Resources Information Center

    Graham, David Mark

    2009-01-01

    Research investigating the impact of factors such as gender, socioeconomic status, racial socialization, and academic self-concept on the academic achievement of African American high school students has been of interest to scholars for decades. Previous literature has focused much attention on the relationship of each of these constructs and…

  16. The Transition Experiences of High-Achieving, Low-Income Undergraduates in an Elite College Environment

    ERIC Educational Resources Information Center

    McLoughlin, Paul J., II

    2012-01-01

    This hermeneutic phenomenological study describes the lived experiences of high-achieving, low-income undergraduates and their transition into a college environment historically reserved for wealthy students. The results of this study indicate that these students are flourishing in full need-based financial aid programs as a result of their own…

  17. Examining the Predictive Power of Autonomy and Self-Evaluation on High School Students' Language Achievement

    ERIC Educational Resources Information Center

    Yuksel, Ismail; Toker, Yalcin

    2013-01-01

    This study aims to determine language learners' autonomy, self-evaluation levels and to examine the predictive power of these two variables on language achievement. The study was designed as mixed method design and was conducted with 108 high school students. Data were collected through an autonomy scale, a self-evaluation scale, schools record on…

  18. Mathematics Attitudes and Achievement of U.S. High School Sophomores Based on Race

    ERIC Educational Resources Information Center

    Martinez, James

    2017-01-01

    What are high school students thinking? The purpose of this study was to examine the degree that psychosocial attitudes affect academic achievement in mathematics for students of different races during secondary schooling. Based on a quantitative methodology, data was gathered from a nationally distributed survey involving over 16,000 student…

  19. The Effects of Alcohol Use on Academic Achievement in High School

    ERIC Educational Resources Information Center

    Balsa, Ana I.; Giuliano, Laura M.; French, Michael T.

    2011-01-01

    This paper examines the effects of alcohol use on high school students' quality of learning. We estimate fixed-effects models using data from the National Longitudinal Study of Adolescent Health. Our primary measure of academic achievement is the student's grade point average (GPA) abstracted from official school transcripts. We find that…

  20. Growing into Equity: Professional Learning and Personalization in High-Achieving Schools

    ERIC Educational Resources Information Center

    Gleason, Sonia Caus; Gerzon, Nancy

    2013-01-01

    What makes a Title I school high-achieving, and what can we all learn from that experience? Professional learning and leadership that supports personalized instruction makes the difference, as captured in the ground-breaking research of authors Sonia Caus Gleason and Nancy Gerzon. This illuminating book shows how four outstanding schools are…

  1. Further Evidence of an Engagement-Achievement Paradox among U.S. High School Students

    ERIC Educational Resources Information Center

    Shernoff, David J.; Schmidt, Jennifer A.

    2008-01-01

    Achievement, engagement, and students' quality of experience were compared by racial and ethnic group in a sample of students (N = 586) drawn from 13 high schools with diverse ethnic and socioeconomic student populations. Using the Experience Sampling Method (ESM), 3,529 samples of classroom experiences were analyzed along with self-reported…

  2. Impact of Physical Environment on Academic Achievement of High School Youth.

    ERIC Educational Resources Information Center

    Burkhalter, Bettye B.

    1983-01-01

    To study the relationship of the physical environment to high school students' academic achievement, 60 students participated in an experiential career exploration program at the Alabama Space and Rocket Center while 108 students participated in a traditional careers program. Tests indicated the former group improved more in career choice…

  3. Reliability and Validity Evidence for Achievement Goal Models in High School Physical Education Settings

    ERIC Educational Resources Information Center

    Guan, Jianmin; McBride, Ron; Xiang, Ping

    2007-01-01

    Although empirical research in academic areas provides support for both a 3-factor as well as a 4-factor achievement goal model, both models were proposed and tested with a collegiate sample. Little is known about the generalizability of either model with high school level samples. This study was designed to examine whether the 3-factor model…

  4. Antecedent and Concurrent Psychosocial Skills That Support High Levels of Achievement within Talent Domains

    ERIC Educational Resources Information Center

    Olszewski-Kubilius, Paula; Subotnik, Rena F.; Worrell, Frank C.

    2015-01-01

    Motivation and emotional regulation are important for the sustained focused study and practice required for high levels of achievement and creative productivity in adulthood. Using the talent development model proposed by the authors as a framework, the authors discuss several important psychosocial skills based on the psychological research…

  5. How High-Achieving African American Undergraduate Men Negotiate Cultural Challenges at a Predominantly White Institution

    ERIC Educational Resources Information Center

    Bradley, Elva Elaine

    2010-01-01

    In this study I examine the manner in which high-achieving African American undergraduate men negotiate cultural challenges in a predominantly White institution (PWI). Cultural theory underpins the conceptual framework of this case study. Basing the study in cultural theory provided a lens through which to view the lived experiences of the twenty…

  6. Central American Refugees and U.S. High Schools. A Psychosocial Study of Motivation and Achievement.

    ERIC Educational Resources Information Center

    Suarez-Orozco, Marcelo M.

    This ethnographic study documents and interprets key school, work, and family life issues in the lives and experiences of a sampling of recent immigrants from the war-torn Central American nations; and suggests a psychocultural theory of achievement motivation. Information was gathered from observation in two urban high schools, interviews with 50…

  7. The Impact of Inclusion on the Academic Achievement of High School Special Education Students

    ERIC Educational Resources Information Center

    Dawkins, Harold Smith

    2010-01-01

    This dissertation examined the impact of inclusion on the academic achievement outcome of high school special education students as measured by English 1, biology, and algebra 1 as a function of gender, ethnicity, and years of inclusion. The study also examined the generalizations with confidence that could be made about the use of inclusion…

  8. High-Stakes Testing and Student Achievement: Updated Analyses with NAEP Data

    ERIC Educational Resources Information Center

    Nichols, Sharon L.; Glass, Gene V.; Berliner, David C.

    2012-01-01

    The present research is a follow-up study of earlier published analyses that looked at the relationship between high-stakes testing pressure and student achievement in 25 states. Using the previously derived Accountability Pressure Index (APR) as a measure of state-level policy pressure for performance on standardized tests, a series of…

  9. Standardized Tests as Measurements of Achievement: Does the High School Assessment Program (HSAP) Measure Up?

    ERIC Educational Resources Information Center

    Ray, Susan Amanda

    2008-01-01

    Purpose: The purpose of this study was to determine the correlation between HSAP scores and various measures of classroom achievement such as overall GPA, End Of Course Scores and SAT/ACT scores of Berea High School [BHS] students in the classes of 2005-2006 and 2006-2007. Methodology: The researcher collected the following data for random samples…

  10. Brain Structure and Resting-State Functional Connectivity in University Professors with High Academic Achievement

    ERIC Educational Resources Information Center

    Li, Weiwei; Yang, Wenjing; Li, Wenfu; Li, Yadan; Wei, Dongtao; Li, Huimin; Qiu, Jiang; Zhang, Qinglin

    2015-01-01

    Creative persons play an important role in technical innovation and social progress. There is little research on the neural correlates with researchers with high academic achievement. We used a combined structural (regional gray matter volume, rGMV) and functional (resting-state functional connectivity analysis, rsFC) approach to examine the…

  11. Ugandan Immigrant Students' Perceptions of Barriers to Academic Achievement in American High Schools

    ERIC Educational Resources Information Center

    Ssekannyo, Denis

    2010-01-01

    In a world that is now a global village, enterprising individuals, especially from Third World countries, who make it to greener pastures do not leave their children behind. But with a long list of barriers to academic achievement associated with immigrant and minority students in American high schools, an understanding of the experiences and…

  12. Students' High School Organizational Leadership Opportunities and Their Influences on Academic Achievement and Civic Participation

    ERIC Educational Resources Information Center

    Elemen, Jennifer E.

    2015-01-01

    The purpose of this quantitative study was to analyze high school leadership praxis for its inclusion of students in organizational leadership dialogue and decision-making and the influences of these factors on student achievement and civic participation. Survey questionnaire data were provided by 215 full-time enrolled undergraduate students from…

  13. Achievement, School Integration, and Self-Efficacy in Single-Sex and Coeducational Parochial High Schools

    ERIC Educational Resources Information Center

    Micucci, Kara Hanson

    2014-01-01

    A structural model for prior achievement, school integration, and self-efficacy was developed using Tinto's theory of student attrition and Bandura's self-efficacy theory. The model was tested and revised using a sample of 1,452 males and females from single-sex and coeducational parochial high schools. Results indicated that the theoretically…

  14. The Relationship between Illinois School District Superintendent Longevity and High School Student Achievement

    ERIC Educational Resources Information Center

    Libka, Robert J.

    2012-01-01

    Frequent changes in school district superintendents may be having a detrimental impact on student achievement. Rapid changes in leadership today parallel the present (NCLB) era of high stakes state assessments. The goal of the study was to provide correlation research that would have a positive effect on school district management, superintendent…

  15. Effect of Textbook Readability on Student Achievement in High School Chemistry.

    ERIC Educational Resources Information Center

    Rapp, D. Neil

    2001-01-01

    Notes the readability level of many high school chemistry textbooks is far above students' reading levels. Conducts two separate studies, making every effort to keep the two classes as similar as possible in all aspects except text. Finds strong evidence that changing the chemistry textbook resulted in an increase in student achievement. Suggests…

  16. Negative Relationship between Achievement in High School and Self-Concept in College.

    ERIC Educational Resources Information Center

    Wolfe, Raymond N.; Grosch, James W.

    Social learning theory implies that there should be a significant positive relationship between academic performance and self-concept and outcomes of recent meta-analyses support this prediction. While path-analytic studies of high school samples in the 1960s and 1970s demonstrated that ability and achievement each made a small positive…

  17. The Impact of Reading Success Academy on High School Reading Achievement

    ERIC Educational Resources Information Center

    Burlison, Kelly; Chave, Josh

    2014-01-01

    The study explores the effectiveness of the Reading Success Academy on the reading achievement of the selected group of ninth-grade students in a comprehensive high school. We examine in what ways the Reading Success Academy may improve the reading proficiency rates and amount of reading growth of ninth-grade students. The results indicate that…

  18. Black High Achieving Undergraduate Mathematics Majors Discuss Success and Persistence in Mathematics

    ERIC Educational Resources Information Center

    Ellington, Roni M.; Frederick, Rona

    2010-01-01

    Experiences of eight Black high-achieving college junior and senior mathematics majors are examined to discern which social and cultural factors shape success and persistence in mathematics. College persistence literature as well as mathematics education studies that document Black students' success in mathematics were used as frameworks to…

  19. Teaching Practices in Grade 5 Mathematics Classrooms with High-Achieving English Learner Students

    ERIC Educational Resources Information Center

    Merritt, Eileen G.; Palacios, Natalia; Banse, Holland; Rimm-Kaufman, Sara E.; Leis, Micela

    2017-01-01

    Teachers need more clarity about effective teaching practices as they strive to help their low-achieving students understand mathematics. Our study describes the instructional practices used by two teachers who, by value-added metrics, would be considered "highly effective teachers" in classrooms with a majority of students who were…

  20. One-to-One Computing and Student Achievement in Ohio High Schools

    ERIC Educational Resources Information Center

    Williams, Nancy L.; Larwin, Karen H.

    2016-01-01

    This study explores the impact of one-to-one computing on student achievement in Ohio high schools as measured by performance on the Ohio Graduation Test (OGT). The sample included 24 treatment schools that were individually paired with a similar control school. An interrupted time series methodology was deployed to examine OGT data over a period…

  1. Emotional Intelligence and Academic Achievement of High School Students in Kanyakumari District

    ERIC Educational Resources Information Center

    Lawrence, A. S. Arul; Deepa, T.

    2013-01-01

    The objective of the study is to find the significant relationship between emotional intelligence and academic achievement of high school students with reference to the background variables. Survey method was employed. Two tools are used in this study namely self-made Trait Emotional Intelligence Questionnaire Short Form (TEIQue SF) and the…

  2. Integrating Economic and Social Policy: Good Practices from High-Achieving Countries. Innocenti Working Papers.

    ERIC Educational Resources Information Center

    Mehrotra, Santosh

    This paper examines the successes of 10 "high achievers," countries with social indicators far higher than might be expected, given their national wealth, pulling together the lessons learned for social policy in the developing world. The 10 countries identified are Costa Rica, Cuba, Barbados, Botswana, Zimbabwe, Mauritius, Kerala, Sri…

  3. Spatial Experiences of High Academic Achievers: Insights from a Developmental Perspective

    ERIC Educational Resources Information Center

    Weckbacher, Lisa Marie; Okamoto, Yukari

    2012-01-01

    The study explored the relationship between types of spatial experiences and spatial abilities among 13- to 14-year-old high academic achievers. Each participant completed two spatial tasks and a survey assessing favored spatial activities across five categories (computers, toys, sports, music, and art) and three developmental periods (early…

  4. The Impact of High School Size on Math Achievement and Dropout Rate

    ERIC Educational Resources Information Center

    Werblow, Jacob; Duesbery, Luke

    2009-01-01

    The study explores the ways in which school size influences two important student outcomes commonly used in school effects research: growth in mathematics achievement and dropout rate. Past research suggests that smaller high schools can lead to increased benefits for students. In this study, multilevel analytic models of the first two waves of…

  5. Filial Piety and Academic Motivation: High-Achieving Students in an International School in South Korea

    ERIC Educational Resources Information Center

    Tam, Jonathan

    2016-01-01

    This study uses self-determination theory to explore the mechanisms of filial piety in the academic motivation of eight high-achieving secondary school seniors at an international school in South Korea, resulting in several findings. First, the students attributed their parents' values and expectations as a major source of the students'…

  6. Obesity, High-Calorie Food Intake, and Academic Achievement Trends among U.S. School Children

    ERIC Educational Resources Information Center

    Li, Jian; O'Connell, Ann A.

    2012-01-01

    The authors investigated children's self-reported high-calorie food intake in Grade 5 and its relationship to trends in obesity status and academic achievement over the first 6 years of school. They used 3-level hierarchical linear models in the large-scale database (the Early Childhood Longitudinal Study--Kindergarten Cohort). Findings indicated…

  7. Teachers and Student Achievement in the Chicago Public High Schools. WP 2002-28. Revised

    ERIC Educational Resources Information Center

    Aaronson, Daniel; Barrow, Lisa; Sander, William

    2003-01-01

    Using unique administrative data on Chicago public high school students and their teachers, we are able to estimate the importance of teachers on student mathematical achievement. We find that teachers are educationally and statistically important. To be sure, sampling variation and other measurement issues can strongly influence estimates of…

  8. Social Media Use, Loneliness, and Academic Achievement: A Correlational Study with Urban High School Students

    ERIC Educational Resources Information Center

    Neto, Roque; Golz, Nancy; Polega, Meaghan

    2015-01-01

    This study explored the association between social media use, loneliness, and academic achievement in high school students and identified the demographic characteristics associated with these three elements. This study also aimed to identify the percentage of variance in loneliness accounted for by social media use and GPA. Participants were 345…

  9. Actively Closing the Gap? Social Class, Organized Activities, and Academic Achievement in High School

    ERIC Educational Resources Information Center

    Morris, David S.

    2015-01-01

    Participation in Organized Activities (OA) is associated with positive behavioral and developmental outcomes in children. However, less is known about how particular aspects of participation affect the academic achievement of high school students from different social class positions. Using the Education Longitudinal Study of 2002, this study…

  10. Turkish High School Students' Biology Achievement in Relation to Academic Self-Regulation

    ERIC Educational Resources Information Center

    Yumusak, Necmettin; Sungur, Semra; Cakiroglu, Jale

    2007-01-01

    This study aimed at investigating the contribution of motivational beliefs, cognitive, and metacognitive strategy use to Turkish high school students' achievement in biology. In order to investigate the specified purpose of the study, 519 tenth-grade students were administered the Motivated Strategies for Learning Questionnaire (Pintrich, Smith,…

  11. Communication Satisfaction, Organizational Citizenship Behavior and the Relationship to Student Achievement in High Schools

    ERIC Educational Resources Information Center

    Blanchard, Gayle A.

    2012-01-01

    This study used a correlational design that allowed the researcher to examine the relationship among communication satisfaction, organizational citizenship behaviors (OCB) and student achievement. High school teachers were surveyed from a convenience sample of 12 school districts in Arizona. Established instruments were used to survey teachers'…

  12. Consequences of the Confucian Culture: High Achievement but Negative Psychological Attributes?

    ERIC Educational Resources Information Center

    Ho, Irene T.; Hau, Kit-Tai

    2010-01-01

    In "Unforgiving Confucian culture: A breeding ground for high academic achievement, test anxiety and self-doubt?" Stankov (in press) provides three reasons for caution against over-glorifying the academic excellence of Confucian Asian learners, namely that it may lead to a reluctance to change their rote learning approach which is not conducive to…

  13. Evaluative and Behavioral Correlates to Intrarehearsal Achievement in High School Bands

    ERIC Educational Resources Information Center

    Montemayor, Mark

    2014-01-01

    The purpose of this study was to investigate relationships of teaching effectiveness, ensemble performance quality, and selected rehearsal procedures to various measures of intrarehearsal achievement (i.e., musical improvement exhibited by an ensemble during the course of a single rehearsal). Twenty-nine high school bands were observed in two…

  14. Faculty Perceptions of High-Achieving Male Collegians: A Critical Race Theory Analysis

    ERIC Educational Resources Information Center

    Comeaux, Eddie

    2013-01-01

    Critical race theory was employed as an interpretive framework to explore faculty perceptions of the academic accomplishments of high-achieving Black and White male collegians. Using photo elicitation methodology, faculty participants responded to a randomly assigned photograph of and vignette about either a Black or White male student. While most…

  15. Self-Graded and Teacher-Graded Achievement in a BSCS High School Biology Course.

    ERIC Educational Resources Information Center

    Good, Wallace Martin

    The effect of self-grading on biology students exposed to the same instruction (except grading) in an upper-middle class public school was investigated by comparing self-graded and teacher-graded populations in (1) achievement in high school biology, (2) level of aspiration behavior, (3) critical thinking skills, and (4) productivity. The…

  16. Cognitive Abilities and Motivational Processes in High School Students' Situational Engagement and Achievement in Science.

    ERIC Educational Resources Information Center

    Lau, Shun; Roeser, Robert W.

    2002-01-01

    Building on R. Snow's two pathways to achievement outcomes (1989), examined how cognitive and motivational factors associated with the performance and commitment pathways respectively contributed to prediction of outcomes in science for 491 high school students. Results are consistent with Snow's conjecture that factors related to both pathways…

  17. Overall Findings: Common Practices and Procedures across Schools. High Achieving Schools Study. Synthesis Report

    ERIC Educational Resources Information Center

    Mohajeri-Nelson, Nazanin; Bamberry, Lynn; Dunaway, Wendy; Hunter, Ellen; Klein, Jeff; Kuntz, Courtney; Negley, Tina; Singer, Robin; Ottenbreit, Rebekah; Young, Eric

    2015-01-01

    This report summarizes the factors that were commonly noted across five high achieving elementary schools in Colorado: (1) Burlington; (2) Canyon Creek; (3) Soaring Eagles; (4) South Lakewood; and (5) Tavelli. After 10 days of onsite visits to participating schools, noteworthy commonalities surfaced across the schools. Policies, practices, and…

  18. Thermoacoustic Contrast of Prostate Cancer due to Heating by Very High Frequency Irradiation

    PubMed Central

    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 thermoacoustic 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. PMID:25554968

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Patch, S K; Hull, D; Thomas, M; Griep, S K; Jacobsohn, K; See, W A

    2015-01-21

    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.