Sample records for angular resolution approximately

  1. Trade-offs between Angular and Spatial Resolution in High Angular Resolution Diffusion Imaging

    E-print Network

    Thompson, Paul

    Trade-offs between Angular and Spatial Resolution in High Angular Resolution Diffusion Imaging. Jack Jr4 , Arthur W. Toga1 , Paul M. Thompson1 1 Laboratory of Neuro Imaging, Dept. of Neurology, UCLA question for DTI is how to allocate the scanning time: higher spatial resolution or more angular resolution

  2. Supernovae at the Highest Angular Resolution

    NASA Technical Reports Server (NTRS)

    Dyk, S. Van; Weiler, K.; Sramek, R.; Panagia, N.; Lacey, C.; Montes, M.; Mercaide, J.; Lewin, W.; Fox, D.; Filippenko, A.; Peng, C.

    2000-01-01

    The study of supernovae (SNe) and their environments in host galaxies at the highest possible angular resolution in a number of wavelength regimes is providing vital clues to the nature of their progenitor stars.

  3. Angular resolution of the Pierre Auger Observatory

    SciTech Connect

    Bonifazi, C.

    2005-08-01

    We studied the angular resolution of the Pierre Auger Detector using data collected from January 2004 to May 2005. The detector consists of two independent components, the fluorescence detector and the surface detector. Hybrid events, observed simultaneously by both components, have smaller reconstruction uncertainties than the events observed with only one component. The hybrid resolution is extracted from artificial showers generated by laser shots, while the surface detector angular accuracy is then determined from the comparison of the hybrid geometrical fit with the one obtained from the surface detector alone. We used adjacent surface detector stations to cross check our methods. The angular reconstruction accuracy of the surface detector events is given as a function of station multiplicity.

  4. CHARM2: An updated Catalog of High Angular Resolution Measurements

    Microsoft Academic Search

    A. Richichi; I. Percheron; M. Khristoforova

    2005-01-01

    We present an update of the Catalog of High Angular Resolution Measurements (CHARM, Richichi & Percheron \\\\cite{CHARM}, A&A, 386, 492), which includes results available until July 2004. CHARM2 is a compilation of direct measurements by high angular resolution methods, as well as indirect estimates of stellar diameters. Its main goal is to provide a reference list of sources which can

  5. CHARM: A Catalog of High Angular Resolution Measurements

    Microsoft Academic Search

    A. Richichi; I. Percheron

    2002-01-01

    The Catalog of High Angular Resolution Measurements (CHARM) includes most of the measurements obtained by the techniques of lunar occultations and long-baseline interferometry at visual and infrared wavelengths, which have appeared in the literature or have otherwise been made public until mid-2001. A total of 2432 measurements of 1625 sources are included, along with extensive auxiliary information. In particular, visual

  6. PHAROS - Proposal for a high-angular-resolution optical survey

    NASA Astrophysics Data System (ADS)

    Greenaway, A. H.; Smith, D. Mack

    A 2 mW laser source at cis-lunar altitudes provides sufficient illumination for adaptive-optic calibration of ground-based telescopes. Orbital parameters to permit such a satellite to be used for high-angular-resolution imaging from La Palma are examined. The apparent motion of the satellite is sufficiently slow to permit 60-min integrations on some low-declination astronomical objects.

  7. EUSO angular resolution based on Pierre Auger Observatory reconstruction methodology

    NASA Astrophysics Data System (ADS)

    Painter, William

    2015-04-01

    Ultra high energy cosmic rays (UHECRs) are astro-particles with energies above 1018 eV and are a readily detected phenomena. Their origin is yet undetermined due to the exceedingly low flux, 1 particle per km2 per century at 1020 eV. The proposed Extreme Universe Space Observatory (EUSO) utilizes the bottom 20 km of the atmosphere as a detection volume resulting in a detection area of nearly 150 , 000 km2 in nadir mode. We have developed an UHECR angular reconstruction algorithm based on the methodology developed at the Pierre Auger Observatory. This algorithm shows improved angular resolution over previous EUSO methods and has been applied to simulated showers over the expected energy and zenith angle ranges. William Painter with Dr. Fred Sarazin.

  8. The AT20G high-angular-resolution catalogue

    NASA Astrophysics Data System (ADS)

    Chhetri, R.; Ekers, R. D.; Jones, P. A.; Ricci, R.

    2013-09-01

    We present the high-angular-resolution catalogue for the Australia Telescope 20 GHz (AT20G) survey, using the high-angular-resolution 6-km antenna data at the baselines of ˜4500 m of the Australia Telescope Compact Array. We have used the data to produce the visibility catalogue that separates the compact active galactic nuclei (AGNs) from the extended radio sources at the 0.15 arcsec angular scale, corresponding to the linear size scale of 1 kpc at redshifts higher than 0.7. We find the radio population at 20 GHz to be dominated by compact AGNs constituting 77 per cent of the total sources in the AT20G. We introduce the visibility-spectra diagnostic plot, produced using the AT20G cross-matches with lower frequency radio surveys at 1 GHz [the NRAO VLA Sky Survey (NVSS) and the Sydney University Molonglo Sky Survey (SUMSS)], that separates the 20 GHz population into distinct sub-populations of the compact AGNs, the compact steep-spectrum (CSS) sources, the extended AGN-powered sources and extended flat-spectrum sources. The extended flat-spectrum sources include a local thermal emitting population of high-latitude planetary nebulae and also gravitational lens and binary black hole candidates among the AGNs. We find a smooth transition in properties between the CSS sources and the AGN populations. The visibility catalogue, together with the main AT20G survey, provides an estimate of angular size scales for sources in the AT20G and an estimate of the flux arising from central cores of extended radio sources. The identification of the compact AGNs in the AT20G survey provides high-quality calibrators for high-frequency radio telescope arrays and very large baseline interferometry observations.

  9. Optical Turbulence in High Angular Resolution Techniques in Astronomy

    NASA Astrophysics Data System (ADS)

    Beckers, Jacques M.

    2009-09-01

    All astronomical observations are done best from space where the absorption by and turbulence in the Earth atmosphere are absent. One has access to the entire electromagnetic radiation spectrum and the absence of seeing allows unlimited angular resolution. However, the cost of facilities in space and their operation is 3 orders of magnitude of similar sized facilities on Earth. Experimental astrophysicists have therefore in the past decades pursued the development of techniques to overcome the seeing limitations by the atmosphere. So far they have been very successful at this and much more is almost certain to come. Adaptive Optics (AO) will make very large (8 - 10-meters diameter) and extremely large (30 - 42 meters diameter) telescopes diffraction limited first at infrared wavelengths and eventually at visible wavelengths. The development of fast optical turbulence/seeing wavefront sensing techniques using artificial sources (Laser Beacons) will enable doing that over the entire sky. Atmospheric Tomography (AT) needed for Multi-Conjugate Adaptive Optics (MCAO) will give 3D maps of the rapidly variable atmospheric turbulence. Large interferometers with baselines of hundreds of meters will further enhance the angular resolution using fringe tracking for both co-phasing and coherent operation. Ground-based astronomy is therefore entering a new era in which milli-arcsecond observations and better are foreseen even of objects at the edge of the universe. The astronomical techniques will result in information of atmospheric optical turbulence which is likely to be of interest for meteorologists.

  10. High-Angular-Resolution Infrared Observations of Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Fukagawa, M.; Hashimoto, J.; Tamura, M.; Seeds/Hiciao/Ircs/Ao188

    2013-10-01

    Observations of protoplanetary disks are essential to understand planet building process since they provide realistic initial conditions as well as insights into new-born planets through disk-planet dynamical interaction. Scattered-light observations at optical and near-infrared are complementary with longer-wavelength studies as they can provide the information on smaller grains in disks, thus useful to discuss such as grain growth and dust transport that can be either the basic step toward or the consequence of planet-forming activity. As a part of Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS), we have observed more than 60 T Tauri and Herbig Ae/Fe stars. Our targets include transitional systems showing the dips in the mid-infrared SEDs and/or the resolved cavities in submillimeter. The technique of polarization differential imaging (PDI) was employed combined with adaptive optics for most cases in order to achieve high contrast by extracting the scattered light from the disk while suppressing the unpolarized stellar light. The PDI observations indeed enabled us to look at the inner region, as close as about 20 AU in radius typically, with the angular resolution of 0.06 arcsec, corresponding to less than 10 AU in nearby star-forming regions. As a result, the SEEDS imaging has newly uncovered rich structures such as spirals, inner holes, and gaps for transitional systems. The highlight is the discovery of two spiral arms in the submillimeter cavity for SAO 206462, and the subsequent finding of similar spirals for MWC 758, which can be explained by possible presence of giant planets. The comparable angular resolution will be achieved in submillimeter soon with ALMA, and multi-wavelength study will become more important for comprehensive understanding of disks.

  11. In-flight performance of the Very high Angular resolution ULtraviolet Telescope sounding rocket payload

    NASA Astrophysics Data System (ADS)

    Korendyke, Clarence M.; Vourlidas, A.; Cook, John W.; Dere, Kenneth P.; Feldman, R.; Howard, Russell A.; Lilley, D. N.; Morrill, Jeff S.; Moses, J. Daniel; Moulton, Norman E.; Moye, Robert W.; Roberts, D. E.; Shepler, E. L.; Smith, J. K.; Socker, Dennis G.; Spears, T. R.; Waymire, R. S.; Brown, Wayne E.; Tarbell, Theodore D.; Berger, Tom; Handy, Brian N.

    2000-12-01

    The Very high Angular Resolution ULtraviolet Telescope experiment was successfully launched on May 7, 1999 on a Black Brant sounding rocket vehicle from White Sands Missile Range. The instrument consists of a 30 cm UV diffraction limited telescope followed by a double grating spectroheliograph tuned to isolate the solar Lyman (alpha) emission line. During the flight, the instrument successfully obtained a series of images of the upper chromosphere with a limiting resolution of approximately 0.33 arc-seconds. The resulting observations are the highest resolution images of the solar atmosphere obtained from space to date. The flight demonstrated that subarc-second ultraviolet images of the solar atmosphere are achievable with a high quality, moderate aperture space telescope and associated optics. Herein, we describe the payload and its in- flight performance.

  12. Progress Toward A Very High Angular Resolution Imaging Spectrometer (VERIS)

    NASA Astrophysics Data System (ADS)

    Korendyke, Clarence M.; Vourlidas, A.; Landi, E.; Seely, J.; Klimchuck, J.

    2007-07-01

    Recent imaging at arcsecond (TRACE) and sub-arcsecond (VAULT) spatial resolution clearly show that structures with fine spatial scales play a key role in the physics of the upper solar atmosphere. Both theoretical and observational considerations point to the importance of small spatial scales, impulsive energy release, strong dynamics, and extreme plasma nonuniformity. Fundamental questions regarding the nature, structure, properties and dynamics of loops and filamentary structures in the upper atmosphere have been raised. To address these questions, we are developing a next generation, VEry high angular Resolution Imaging Spectrometer (VERIS) as a sounding rocket instrument. VERIS will obtain the necessary high spatial resolution, high fidelity measurements of plasma temperatures, densities and velocities. With broad simultaneous temperature coverage, the VERIS observations will directly address unresolved issues relating to interconnections of various temperature solar plasmas. VERIS will provide the first ever subarcsecond spectra of transition region and coronal structures. It will do so with a sufficient spectral resolution of to allow centroided Doppler velocity determinations to better than 3 km/s. VERIS uses a novel two element, normal incidence optical design with highly reflective EUV coatings to access a spectral range with broad temperature coverage (0.03-15 MK) and density-sensitive line ratios. Finally, in addition to the spectra, VERIS will simultaneously obtain spectrally pure slot images (10x150 arcsec) in the +/-1 grating orders, which can be combined to make instantaneous line-of-sight velocity maps with 8km/s accuracy over an unprecedented field of view. The VERIS program is beginning the second year of its three year development cycle. All design activities and reviews are complete. Fabrication of all major components has begun. Brassboard electronics cards have been fabricated, assembled and tested. The paper presents the essential scientific characteristics of the instrument.

  13. The GAMMA-400 gamma-ray telescope angular resolution

    NASA Astrophysics Data System (ADS)

    Kheymits, Maxim; Leonov, Alexey

    The measurements of gamma-ray fluxes and cosmic-ray electrons and positrons in the energy range from 100 MeV to several TeV, which will be realized by the specially designed GAMMA-400 gamma-ray telescope, concern with the following broad range of science topics. Search for signatures of dark matter, surveying the celestial sphere in order to study point and extended sources of gamma-rays, measuring the energy spectra of Galactic and extragalactic diffuse gamma-ray emission, study of gamma-ray bursts and gamma-ray emission from the Sun. To clarify these scientific problems with the new experimental data the GAMMA-400 gamma-ray telescope possesses unique physical characteristics comparing with previous and present experiments. For gamma-ray energies more than 100 GeV GAMMA-400 provides the energy resolution nearby 1% and angular resolution better than 0.02 deg. The methods, developed to reconstruct the direction of incident gamma photon, are presented in this paper. The main point concerns with the space topology of high energy gamma photon interaction in the matter of GAMMA-400. Multiple secondary particles, generated inside gamma-ray telescope, produce significant problems to restore the direction of initial gamma photon. Also back-splash particles, i.e., charged particles and gamma photons generated in calorimeter and moved upward, mask the initial tracks of electron/positron pair from conversion of incident gamma photon. The processed methods allow us to reconstruct the direction of electromagnetic shower axis and extract the electron/positron trace. As a result, the direction of incident gamma photon with the energy of 100 GeV is calculated with an accuracy of more than 0.02 deg.

  14. ACCELERATION OF HIGH ANGULAR AND SPATIAL RESOLUTION DIFFUSION IMAGING USING COMPRESSIVE SENSING

    E-print Network

    Jacob, Mathews

    ACCELERATION OF HIGH ANGULAR AND SPATIAL RESOLUTION DIFFUSION IMAGING USING COMPRESSIVE SENSING M. We propose a novel compressed sens- ing method to acquire high angular and spatial resolution dif functions (ODF) with high accuracy. We show that at least 6-fold acceleration of acquisition is possible

  15. Cepheids at high angular resolution: circumstellar envelope and pulsation

    NASA Astrophysics Data System (ADS)

    Gallenne, Alexandre

    2011-12-01

    In 2005, interferometric observations with VLTI/VINCI and CHARA/FLUOR revealed the existence of a circumstellar envelope (CSE) around some Cepheids. This surrounding material is particularly interesting for two reasons: it could have an impact on the distance estimates and could be linked to a past or on-going mass loss. The use of Baade-Wesselink methods for independent distance determinations could be significantly biased by the presence of these envelopes. Although their observations are difficult because of the high contrast between the photosphere of the star and the CSE, several observation techniques have the potential to improve our knowledge about their physical properties. In this thesis, I discuss in particular high angular resolution techniques that I applied to the study of several bright Galactic Cepheids. First, I used adaptive optic observations with NACO of the Cepheid RS Puppis, in order to deduce the flux ratio between the CSE and the photosphere of the star. In addition, I could carry out a statistical study of the speckle noise and inspect a possible asymmetry. Secondly, I analysed VISIR data to study the spectral energy distribution of a sample of Cepheids. These diffraction-limited images enabled me to carry out an accurate photometry in the N band and to detect an IR excess linked to the presence of a circumstellar component. On the other hand, applying a Fourier analysis I showed that some components are resolved. I then explored the K' band with the recombination instrument FLUOR for some bright Cepheids. Thanks to new set of data of Y Oph, I improved the study of its circumstellar envelope, using a ring-like model for the CSE. For two other Cepheids, U Vul and S Sge, I applied the interferometric Baade-Wesselink method in order to estimate their distance.

  16. Announcement - Scientific Importance of High Angular Resolution at Infrared and Optical Wavelengths - ESO Conference

    NASA Astrophysics Data System (ADS)

    1981-03-01

    The European Southern Observatory is organizing an international conference on the subject "SCIENTIFIC IMPORTANCE OF HIGH ANGULAR RESOLUTION AT INFRARED AND OPTICAL WAVELENGTHS", to be held in the ESO building at Garching bei München during the period of 24-27 March 1981. The purpose of this conference is to discuss, on the one hand, the systems in use or under construction and possible future developments to achieve high angular resolution and, on the other hand, to discuss the areas of astrophysics which, in the next decades, will most benefit from observations at high angular resolution.

  17. How Many Gradients are Sufficient in High-Angular Resolution Diffusion Imaging (HARDI)?

    E-print Network

    Thompson, Paul

    ). We artificially reduced the angular sampling of the 105-gradient sequence by optimizing the angular to determine analytically. Further studies of scanner field strength, spatial resolution, tolerability, motion artifacts, and clinical effect sizes will clarify the added benefit of this SNR for neuroscientific studies

  18. Measurements of the hemispherical-directional reflectance of snow at fine spectral and angular resolution

    E-print Network

    Dozier, Jeff

    Measurements of the hemispherical-directional reflectance of snow at fine spectral and angular of the hemispherical-directional reflectance factor (HDRF) of snow made at fine spectral and angular resolution underestimated reflectance for l > 1.30 mm and had large absolute errors in the perpendicular plane. Mean

  19. Star Formation at High Angular Resolution ASP Conference Series, Vol. S-221, 2003

    E-print Network

    Ward-Thompson, Derek

    Star Formation at High Angular Resolution ASP Conference Series, Vol. S-221, 2003 M.G. Burton, R-workers identified a significant number of isolated cores (e.g. Myers & Benson 1983; Benson & Myers 1989). Comparison

  20. SEX DIFFERENCES IN THE HUMAN CONNECTOME: 4-TESLA HIGH ANGULAR RESOLUTION DIFFUSION IMAGING (HARDI)

    E-print Network

    Thompson, Paul

    SEX DIFFERENCES IN THE HUMAN CONNECTOME: 4-TESLA HIGH ANGULAR RESOLUTION DIFFUSION IMAGING (HARDI diffusion imaging at 4 Tesla, we scanned 234 young adult twins and siblings (mean age: 23.4 ± 2.0 SD years

  1. X-ray interferometry with transmissive beam combiners for ultra-high angular resolution astronomy

    Microsoft Academic Search

    Gerald K. Skinner; John F. Krizmanic

    2009-01-01

    Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s of meters

  2. X-ray interferometry with transmissive beam combiners for ultra-high angular resolution astronomy

    Microsoft Academic Search

    Gerald K. Skinner; John F. Krizmanic

    2009-01-01

    Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second\\u000a angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive\\u000a black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s\\u000a of meters

  3. Strong scintillations in astrophysics. I - The Markov approximation, its validity and application to angular broadening

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Jokipii, J. R.

    1975-01-01

    The Markov approximation to the propagation of waves in an extended, irregular medium is discussed in an astrophysical context. A new derivation is presented which is simple and which shows that the assumption of Gaussian statistics used by previous authors is irrelevant. We discuss the relevance of the approximation and show that it may apply in many situations of interest, including interstellar scintillations of pulsar signals. The approximation does not require the assumption of weak scattering or Gaussian correlation functions. The Markov equation for the angular spectrum is particularly simple, and solutions are discussed for typical turbulence spectra. It is found that the equation for the angular spectrum is very nearly that used by previous authors, and the present discussion shows that these results are much more general than previously thought. A possible observational test for distinguishing between Gaussian and power-law interstellar density spectra is discussed.

  4. Apparent Diffusion Coefficients from High Angular Resolution Diffusion Imaging: Estimation and

    E-print Network

    Chen, Yiling

    Apparent Diffusion Coefficients from High Angular Resolution Diffusion Imaging: Estimation resolution diffusion imaging has recently been of great interest in characterizing non-Gaussian diffusion pro- cesses. One important goal is to obtain more accurate fits of the apparent diffusion processes

  5. High energy resolution, high angular acceptance crystal monochromator

    DOEpatents

    Alp, E.E.; Mooney, T.M.; Toellner, T.

    1996-06-04

    A 4-bounce dispersive crystal monochromator reduces the bandpass of synchrotron radiation to a 10-50 meV range without sacrificing angular acceptance. The monochromator includes the combination of an asymmetrical channel-cut single crystal of lower order reflection and a symmetrical channel-cut single crystal of higher order reflection in a nested geometric configuration. In the disclosed embodiment, a highly asymmetrically cut ({alpha}=20) outer silicon crystal (4 2 2) with low order reflection is combined with a symmetrically cut inner silicon crystal (10 6 4) with high order reflection to condition a hard x-ray component (5--30 keV) of synchrotron radiation down to the {micro}eV-neV level. Each of the crystals is coupled to the combination of a positioning inchworm and angle encoder via a respective rotation stage for accurate relative positioning of the crystals and precise energy tuning of the monochromator. 7 figs.

  6. High energy resolution, high angular acceptance crystal monochromator

    DOEpatents

    Alp, Ercan E. (Bolingbrook, IL); Mooney, Timothy M. (Westmont, IL); Toellner, Thomas (Green Bay, WI)

    1996-06-04

    A 4-bounce dispersive crystal monochromator reduces the bandpass of synchrotron radiation to a 10-50 meV range without sacrificing angular acceptance. The monochromator includes the combination of an asymmetrical channel-cut single crystal of lower order reflection and a symmetrical channel-cut single crystal of higher order reflection in a nested geometric configuration. In the disclosed embodiment, a highly asymmetrically cut (.alpha.=20) outer silicon crystal (4 2 2) with low order reflection is combined with a symmetrically cut inner silicon crystal (10 6 4) with high order reflection to condition a hard x-ray component (5-30 keV) of synchrotron radiation down to the .mu.eV-neV level. Each of the crystals is coupled to the combination of a positioning inchworm and angle encoder via a respective rotation stage for accurate relative positioning of the crystals and precise energy tuning of the monochromator.

  7. Development of the super high angular resolution principle for X-ray imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Zhang, Shuang-Nan

    2011-01-01

    Development of the Super High Angular Resolution Principle (SHARP) for coded-mask X-ray imaging is presented. We prove that SHARP can be considered as a generalized coded mask imaging method with a coding pattern comprised of diffraction-interference fringes in the mask pattern. The angular resolution of SHARP can be improved by detecting the fringes more precisely than the mask's element size, i.e. by using a detector with a pixel size smaller than the mask's element size. The proposed mission SHARP-X for solar X-ray observations is also briefly discussed.

  8. Low Power Compact Radio Galaxies at High Angular Resolution

    SciTech Connect

    Giroletti, Marcello; Giovannini, G.; /Bologna U. /Bologna, Ist. Radioastronomia; Taylor, G.B.; /KIPAC, Menlo Park /NRAO, Socorro

    2005-06-30

    We present sub-arcsecond resolution multi-frequency (8 and 22 GHz) VLA images of five low power compact (LPC) radio sources, and phase referenced VLBA images at 1.6 GHz of their nuclear regions. At the VLA resolution we resolve the structure and identify component positions and flux densities. The phase referenced VLBA data at 1.6 GHz reveals flat-spectrum, compact cores (down to a few milliJansky) in four of the five sources. The absolute astrometry provided by the phase referencing allows us to identify the center of activity on the VLA images. Moreover, these data reveal rich structures, including two-sided jets and secondary components. On the basis of the arcsecond scale structures and of the nuclear properties, we rule out the presence of strong relativistic effects in our LPCs, which must be intrinsically small (deprojected linear sizes {approx}< 10 kpc). Fits of continuous injection models reveal break frequencies in the GHz domain, and ages in the range 10{sup 5}-10{sup 7} yrs. In LPCs, the outermost edge may be advancing more slowly than in more powerful sources or could even be stationary; some LPCs might also have ceased their activity. In general, the properties of LPCs can be related to a number of reasons, including, but not limited to: youth, frustration, low kinematic power jets, and short-lived activity in the radio.

  9. Bayesian Deconvolution for Angular Super-Resolution in Forward-Looking Scanning Radar

    PubMed Central

    Zha, Yuebo; Huang, Yulin; Sun, Zhichao; Wang, Yue; Yang, Jianyu

    2015-01-01

    Scanning radar is of notable importance for ground surveillance, terrain mapping and disaster rescue. However, the angular resolution of a scanning radar image is poor compared to the achievable range resolution. This paper presents a deconvolution algorithm for angular super-resolution in scanning radar based on Bayesian theory, which states that the angular super-resolution can be realized by solving the corresponding deconvolution problem with the maximum a posteriori (MAP) criterion. The algorithm considers that the noise is composed of two mutually independent parts, i.e., a Gaussian signal-independent component and a Poisson signal-dependent component. In addition, the Laplace distribution is used to represent the prior information about the targets under the assumption that the radar image of interest can be represented by the dominant scatters in the scene. Experimental results demonstrate that the proposed deconvolution algorithm has higher precision for angular super-resolution compared with the conventional algorithms, such as the Tikhonov regularization algorithm, the Wiener filter and the Richardson–Lucy algorithm. PMID:25806871

  10. Bayesian deconvolution for angular super-resolution in forward-looking scanning radar.

    PubMed

    Zha, Yuebo; Huang, Yulin; Sun, Zhichao; Wang, Yue; Yang, Jianyu

    2015-01-01

    Scanning radar is of notable importance for ground surveillance, terrain mapping and disaster rescue. However, the angular resolution of a scanning radar image is poor compared to the achievable range resolution. This paper presents a deconvolution algorithm for angular super-resolution in scanning radar based on Bayesian theory, which states that the angular super-resolution can be realized by solving the corresponding deconvolution problem with the maximum a posteriori (MAP) criterion. The algorithm considers that the noise is composed of two mutually independent parts, i.e., a Gaussian signal-independent component and a Poisson signal-dependent component. In addition, the Laplace distribution is used to represent the prior information about the targets under the assumption that the radar image of interest can be represented by the dominant scatters in the scene. Experimental results demonstrate that the proposed deconvolution algorithm has higher precision for angular super-resolution compared with the conventional algorithms, such as the Tikhonov regularization algorithm, the Wiener filter and the Richardson-Lucy algorithm. PMID:25806871

  11. HARDI: A high angular resolution deployable interferometer for space

    NASA Technical Reports Server (NTRS)

    Bely, Pierre Y.; Burrows, Christopher; Roddier, Francois; Weigelt, Gerd

    1992-01-01

    We describe here a proposed orbiting interferometer covering the UV, visible, and near-IR spectral ranges. With a 6-m baseline and a collecting area equivalent to about a 1.4 m diameter full aperture, this instrument will offer significant improvements in resolution over the Hubble Space Telescope, and complement the new generation of ground-based interferometers with much better limiting magnitude and spectral coverage. On the other hand, it has been designed as a considerably less ambitious project (one launch) than other current proposals. We believe that this concept is feasible given current technological capabilities, yet would serve to prove the concepts necessary for the much larger systems that must eventually be flown. The interferometer is of the Fizeau type. It therefore has a much larger field (for guiding) better UV throughout (only 4 surfaces) than phased arrays. Optimize aperture configurations and ideas for the cophasing and coalignment system are presented. The interferometer would be placed in a geosynchronous or sunsynchronous orbit to minimize thermal and mechanical disturbances and to maximize observing efficiency.

  12. The Influence of Random Phase Errors on the Angular Resolution of Synthetic Aperture Radar Systems

    Microsoft Academic Search

    Jean A. Develet

    1964-01-01

    The influence of random phase errors on the angular resolution of a focused synthetic aperture radar system is treated. The principal measure of performance has been taken as the mean envelope power at the system output. This system output power is evaluated exactly, although not in closed form, based on the following assumptions: 1) the real beam pattern is Gaussian;

  13. A Study of Information Gain in High Angular Resolution Diffusion Imaging (HARDI)

    E-print Network

    Thompson, Paul

    . Zhu2 , L. Zhan3 , K. McMahon4 , G.I. de Zubicaray4 , M. Meredith4 , M. Wright4 , P.M. Thompson3 1 tissue. High- angular resolution diffusion imaging (HARDI) schemes have been em- ployed to resolve fiber estimates of the recovered fibers stabilized with around 40 directions, suggesting asymptotic but clear

  14. Lucky Imaging: High Angular Resolution Imaging in the Visible from the Ground

    E-print Network

    Nicholas M. Law; Craig D. Mackay; John E. Baldwin

    2005-07-13

    We use a Lucky Imaging system to obtain I-band images with much improved angular resolution on a ground-based 2.5m telescope. We present results from a 10-night assessment campaign on the 2.56m Nordic Optical Telescope and quantify the performance of our system in seeings better than 1.0''. In good seeing we have acquired near diffraction-limited images; in poorer seeing the angular resolution has been routinely improved by factors of 2.5-4. The system can use guide stars as faint as I=16 with full performance and its useful field of view is consistently larger than 40" diameter. The technique shows promise for a number of science programmes, both galactic (eg. binary candidates, brown dwarfs, globular cluster cores) and extragalactic (eg. quasar host galaxies, damped Lyman-alpha absorbers).

  15. High Angular Resolution Stellar Imaging with Occultations from the Cassini Spacecraft I: Observational Technique

    E-print Network

    Stewart, Paul N; Hedman, Matthew M; Nicholson, Philip D; Lloyd, James P

    2013-01-01

    We present novel observations utilising the Cassini spacecraft to conduct an observing campaign for stellar astronomy from a vantage point in the outer solar system. By exploiting occultation events in which Mira passed behind the Saturnian ring plane as viewed by Cassini, parametric imaging data were recovered spanning the near-infrared. From this, spatial information at extremely high angular resolution was recovered enabling a study of the stellar atmospheric extension across a spectral bandpass spanning the 1 - 5 {\\mu}m spectral region in the near-infrared. The resulting measurements of the angular diameter of Mira were found to be consistent with existing observations of its variation in size with wavelength. The present study illustrates the validity of the technique; more detailed exploration of the stellar physics obtained by this novel experiment will be the subject of forthcoming papers.

  16. High Angular Resolution and Lightweight X-Ray Optics for Astronomical Missions

    NASA Technical Reports Server (NTRS)

    Zhang, W. W.; Biskach, M. P.; Blake, P. N.; Chan, K. W.; Evans, T. C.; Hong, M.; Jones, W. D.; Jones, W. D.; Kolos, L. D.; Mazzarella, J. M.; McClelland, R. S.; ODell, S. L.; Saha, T. T.; Sharpe, M. V.

    2011-01-01

    X-ray optics with both high angular resolution and lightweight is essential for further progress in x-ray astronomy. High angular resolution is important in avoiding source confusion and reducing background to enable the observation of the most distant objects of the early Universe. It is also important in enabling the use of gratings to achieve high spectral resolution to study, among other things, the myriad plasmas that exist in planetary, stellar, galactic environments, as well as interplanetary, inter-stellar, and inter-galactic media. Lightweight is important for further increase in effective photon collection area, because x-ray observations must take place on space platforms and the amount of mass that can be launched into space has always been very limited and is expected to continue to be very limited. This paper describes an x-ray optics development program and reports on its status that meets these two requirements. The objective of this program is to enable Explorer type missions in the near term and to enable flagship missions in the long term.

  17. Next Generation X-ray Optics: High Angular Resolution, Light Weight, and Low Production Cost

    NASA Astrophysics Data System (ADS)

    Zhang, William

    2013-01-01

    Since its beginning 50 years ago, X-ray astronomy has advanced by leaps and bounds, culminating in its current golden age in which three major observatories—Chandra, XMM-Newton, and Suzaku—are operating simultaneously and addressing some of the most important astronomical and astrophysical problems of our time. Building upon this success, the recent Decadal Survey of Astronomy and Astrophysics has defined objectives for x-ray astronomy whose realization requires both new optics and new detector technologies. The development of these technologies has been identified as one of the highest priorities for funding to enable future x-ray missions. X-ray optics technology based on precision glass slumping is on the verge of revolutionizing x-ray telescope making. It has shown that extremely thin (< 0.4mm) and lightweight (areal density < 1 kg/m2) true Wolter-I mirror segments with angular resolutions better than 7 arc-seconds can be fabricated consistently, efficiently, and inexpensively. In comparison with those of XMM-Newton, these mirror segments represent a factor of 10 reduction in mass while achieving slightly better angular resolution. In comparison with those of Suzaku, they represent a factor of 20 improvement in angular resolution while maintaining the same mass areal density. These advances have been demonstrated with x-ray images from aligned and bonded mirror segments. In short, this technology is approaching TRL-5 for making the mirror assemblies required for a 10 arc-second observatory. In this poster we will present the latest x-ray and environment test results obtained with technology development modules which are substantially similar to flight modules in the way they constructed and tested.

  18. Next Generation X-ray Optics: High Angular Resolution, Light Weight, and Low Production Cost

    NASA Astrophysics Data System (ADS)

    Zhang, William; NGXO

    2014-01-01

    X-ray telescopes are essential to the future of x-ray astronomy. In this talk I will describe a comprehensive program to advance the technology for x-ray telescopes well beyond the state of the art represented by the dour missions currently in operations: Chandra, XMM-Newton, Suzaku, and NuSTAR. This program will address the three key issues in making an x-ray telescope: (1) angular resolution, (2) effective area per unit mass, and (3) cost per unit effective area. The objectives of this technology program are (1) in the near term, to enable Explorer-class x-ray missions and an IXO-type mission, and (2) in the long term, to enable a flagship x-ray mission with sub-arcsecond angular resolution and multi-square-meter effective area, at an affordable cost. We pursue two approaches concurrently, emphasizing the first approach in the near term (2-5 years) and the second in the long term (4-10 years). The first approach is precision slumping of borosilicate glass sheets. By design and choice at the outset, this technique makes lightweight and low-cost mirrors. The development program will continue to improve angular resolution, to enable the production of 5-arcsecond x-ray telescopes, to support Explorer-class missions and one or more missions to supersede the original IXO mission. The second approach is precision polishing and light-weighting of single-crystal silicon mirrors. This approach benefits from two recent commercial developments: (1) the inexpensive and abundant availability of large blocks of monocrystalline silicon, and (2) revolutionary advances in deterministic, precision polishing of mirrors. By design and choice at the outset, this technique is capable of producing lightweight mirrors with sub-arcsecond angular resolution. The development program will increase the efficiency and reduce the cost of the polishing and the light-weighting processes, to enable the production of lightweight sub-arcsecond x-ray telescopes. Concurrent with the fabrication of lightweight mirror segments is the continued development and perfection of alignment and integration techniques, for incorporating individual mirror segments into a precision mirror assembly.

  19. Lucky Imaging: High Angular Resolution Imaging in the Visible from the Ground

    Microsoft Academic Search

    Nicholas M. Law; Craig D. Mackay; John E. Baldwin

    2005-01-01

    We use a Lucky Imaging system to obtain I-band images with much improved\\u000aangular resolution on a ground-based 2.5m telescope. We present results from a\\u000a10-night assessment campaign on the 2.56m Nordic Optical Telescope and quantify\\u000athe performance of our system in seeings better than 1.0''. In good seeing we\\u000ahave acquired near diffraction-limited images; in poorer seeing the angular

  20. Quality assessment of High Angular Resolution Diffusion Imaging data using bootstrap on Q-ball reconstruction

    PubMed Central

    Cohen-Adad, J.; Descoteaux, M.; Wald, L.L.

    2011-01-01

    Purpose To develop a bootstrap method to assess the quality of High Angular Resolution Diffusion Imaging (HARDI) data using Q-Ball imaging (QBI) reconstruction. Materials and Methods HARDI data were re-shuffled using regular bootstrap with jackknife sampling. For each bootstrap dataset, the diffusion orientation distribution function (ODF) was estimated voxel-wise using QBI reconstruction based on spherical harmonics functions. The reproducibility of the ODF was assessed using the Jensen-Shannon divergence (JSD) and the angular confidence interval was derived for the first and the second ODF maxima. The sensitivity of the bootstrap method was evaluated on a human subject by adding synthetic noise to the data, by acquiring a map of image signal-to-noise ratio (SNR) and by varying the echo time and the b-value. Results The JSD was directly linked to the image SNR. The impact of echo times and b-values was reflected by both the JSD and the angular confidence interval, proving the usefulness of the bootstrap method to evaluate specific features of HARDI data. Conclusion The bootstrap method can effectively assess the quality of HARDI data and can be used to evaluate new hardware and pulse sequences, perform multi-fiber probabilistic tractography, and provide reliability metrics to support clinical studies. PMID:21509879

  1. Development of the super-high angular resolution principle for x-ray imaging: experimental demonstrations

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Ling, Zhixing; Zhang, Shuang-Nan

    2012-09-01

    Experimental demonstrations of the Super-High Angular Resolution Principle (SHARP) for coded aperture imaging are presented. SHARP has been theoretically proven to be an extension of the coded aperture imaging system by taking advantage of the significant diffraction-interference effects of pinholes on the mask, which operates beyond the diffraction limit of a single pinhole. We first set up an optical experiment, the so-called SHARP-O, in order to verify the theoretical predictions on SHARP. The images of point sources are successfully reconstructed, with an angular resolution of about 26 arcsec and position accuracy of 2 arcsec, whereas the diffraction limit of a single mask pinhole in the mask is 870 arcsec. We then set up a SHARP-X demonstration experiment at an X-ray beam line facility; encouraging results are obtained, indicating that the SHARP concept is feasible in the soft X-ray band. It is thus possible to achieve sub-arcsec X-ray imaging with a simple coded mask system working beyond the diffraction limit of a single pinhole.

  2. High angular resolution imaging of the circumstellar material around intermediate mass (IM) stars

    E-print Network

    A. Fuente

    2007-05-25

    In this Paper we present high angular resolution imaging of 3 intermediate-mass (IM) stars using the Plateau de Bure Interferometer (PdBI). In particular we present the chemical study we have carried out towards the IM hot core NGC 7129--FIRS 2. This is the first chemical study in an IM hot core and provides important hints to understand the dependence of the hot core chemistry on the stellar luminosity. We also present our high angular resolution (0.3") images of the borderline Class 0-Class I object IC1396 N. These images trace the warm region of this IM protostar with unprecedent detail (0.3"\\sim200 AU at the distance of IC1396 N) and provide the first detection of a cluster of IM hot cores. Finally, we present our interferometric continuum and spectroscopic images of the disk around the Herbig Be star R Mon. We have determined the kinematics and physical structure of the disk associated with this B0 star. The low spectral index derived from the dust emission as well as the flat geometry of the disk suggest a more rapid evolution of the disks associated with massive stars. In the Discussion, we dare to propose a possible evolutionary sequence for the warm circumstellar material around IM stars.

  3. Disks, outflows, and hot cores in the mm range at subarcsecond angular resolution

    NASA Astrophysics Data System (ADS)

    Palau, A.; Fuente, A.; Boissier, J.; Pietu, V.; Sanchez-Monge, A.; Zapata, L.; Fontani, F.; Girart, J. M.; Neri, R.; Busquet, G.; Zhang, Q.; Ho, P. T. P.; Estalella, R.; Audard, M.; Alonso-Albi, T.

    2011-05-01

    The formation of intermediate/high-mass stars is currently a matter of vigorous debate. On one hand, many authors suggest the possibility that massive stars form as a scaled-up version of low-mass stars, thus driving collimated outflows and being associated with rotating accretion disks. On the other hand, the fact that massive stars are found associated with clusters leads to consider the possibility that a cluster could be a requirement for massive star formation. This last property (clustered environments) together with the large distances where massive stars are located make their study challenging and requiring high angular resolution observations. We present a study of four regions forming intermediate/high-mass protostars driving outflows and (two of them) with hot core emission. The four regions were observed at 1 mm using the Plateau de Bure Interferometer in its most extended configuration, reaching angular resolutions of 0.4''. These observations allowed us to study: 1) the millimeter continuum emission down to mass sensitivities of 0.1 Msun, likely tracing the disk in some cases, and dust entrained by the outflow(s) in other cases; 2) the outflow emission as revealed by CO(2-1), tracing the walls of the outflow cavities and/or knots of high-velocity emission; and 3) the hot core emission for two of the regions with an exceptional spatial resolution of 300--700 AU. The hot core emission for one of the sources reveals a velocity gradient, possibly indicating rotation, while the other hot core source splits up into two hot core components with slightly different velocities, possibly forming a binary system fragmented from a rotating core. We will show a first analysis and discussion of these results, which constitute an excellent preparatory step for future ALMA observations.

  4. Future Prospects for Very High Angular Resolution Imaging in the UV/Optical

    NASA Astrophysics Data System (ADS)

    Allen, R. J.

    2004-05-01

    Achieving the most demanding science goals outlined by the previous speakers will ultimately require the development of coherent space-based arrays of UV/Optical light collectors spread over distances of hundreds of meters. It is possible to envisage ``in situ" assembly of large segmented filled-aperture telescopes in space using components ferried up with conventional launchers. However, the cost will grow roughly as the mass of material required, and this will ultimately limit the sizes of the apertures we can afford. Furthermore, since the collecting area and the angular resolution are coupled for diffraction-limited filled apertures, the sensitivity may be much higher than is actually required to do the science. Constellations of collectors deployed over large areas as interferometer arrays or sparse apertures offer the possibility of independently tailoring the angular resolution and the sensitivity in order to optimally match the science requirements. Several concept designs have been proposed to provide imaging data for different classes of targets such as protoplanetary disks, the nuclear regions of the nearest active galaxies, and the surfaces of stars of different types. Constellations of identical collectors may be built and launched at lower cost through mass production, but new challenges arise when they have to be deployed. The ``aperture" synthesized is only as good as the accuracy with which the individual collectors can be placed and held to the required figure. This ``station-keeping" problem is one of the most important engineering problems to be solved before the promise of virtually unlimited angular resolution in the UV/Optical can be realized. Among the attractive features of an array of free-flying collectors configured for imaging is the fact that the figure errors of the ``aperture" so produced may be much more random than is the case for monolithic or segmented telescopes. This can result in a significant improvement in the dynamic range and permit imaging of faint objects near much brighter extraneous nearby sources, a task presently reserved for specially-designed coronagraphs on filled apertures.

  5. Acceptance and Angular Resolution of an Infill Array for the Pierre Auger Surface Detector

    SciTech Connect

    Medina, C. [Tandar Laboratory (CAC - CNEA), Buenos Aires (Argentina); Gomez Berisso, M.; Allekotte, I. [I. Balseiro and Centro Atomico Bariloche (CNEA), Bariloche (Argentina); Etchegoyen, A.; Supanitsky, D. [Tandar Laboratory (CAC - CNEA), Buenos Aires (Argentina); CONICET, Buenos Aires (Argentina); Medina-Tanco, G. [I. Astronomico e Geofisico, Univ. de Sao Paulo, Sao Paulo (Brazil)

    2007-02-12

    The Pierre Auger Observatory has been designed to study the highest-energy cosmic rays in nature (E {>=} 1019 eV). The determination of their arrival direction, energy and composition is performed by the analysis of the atmospheric showers they produce. The Auger Surface Array will consist of 1600 water Cerenkov detectors placed in an equilateral triangular grid of 1.5 km. In this paper we show how adding a ''small'' area of surface detectors at half the above mentioned spacing would make it possible to lower the detection threshold by one order of magnitude, thus allowing the Observatory to reach lower energies where the cross-over from galactic to extragalactic sources is expected. We also analyze the angular resolution that can be attained with such an infill array.

  6. Spatial normalization of the fiber orientation distribution based on high angular resolution diffusion imaging data

    PubMed Central

    Hong, Xin; Arlinghaus, Lori R.; Anderson, Adam W.

    2009-01-01

    Comparison of high angular resolution diffusion imaging (HARDI) measurements between subjects or between time points for the same subject are facilitated by spatial normalization. In this work, an algorithm is developed to transform the fiber orientation distribution (FOD) function, based on HARDI data, taking into account not only translation, but also rotation, scaling, and shearing effects of the spatial transformation. The algorithm is tested using simulated data, and intra-subject and inter-subject normalization of in vivo human data. All cases demonstrate reliable transformation of the FOD. This technique makes it possible to compare the intra-voxel fiber distribution between subjects, between groups, or between time points for a single subject, which will be helpful in HARDI studies of white matter disease. PMID:19353649

  7. HIGH ANGULAR RESOLUTION OBSERVATIONS OF FOUR CANDIDATE BLAST HIGH-MASS STARLESS CORES

    SciTech Connect

    Olmi, Luca; Poventud, Carlos M. [Physics Department, Rio Piedras Campus, University of Puerto Rico, Box 23343, UPR Station, San Juan, Puerto Rico (United States); Araya, Esteban D. [Physics Department, Western Illinois University, 1 University Circle, Macomb, IL 61455 (United States); Chapin, Edward L.; Gibb, Andrew [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Hofner, Peter [Physics Department, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 (United States); Martin, Peter G., E-mail: olmi.luca@gmail.co, E-mail: olmi@arcetri.astro.i [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada)

    2010-06-01

    We discuss high angular resolution observations of ammonia toward four candidate high-mass starless cores (HMSCs). The cores were identified by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) during its 2005 survey of the Vulpecula region where 60 compact sources were detected simultaneously at 250, 350, and 500 {mu}m. Four of these cores, with no IRAS-PSC or MSX counterparts, were mapped with the NRAO Very Large Array and observed with the Effelsberg 100 m telescope in the NH{sub 3}(1,1) and (2,2) spectral lines. Our observations indicate that the four cores are cold (T {sub k} < 16 K) and show a filamentary and/or clumpy structure. They also show a significant velocity substructure within {approx}1 km s{sup -1}. The four BLAST cores appear to be colder and more quiescent than other previously observed HMSC candidates, suggesting an earlier stage of evolution.

  8. The multiplicity of massive stars: A high angular resolution survey with the HST fine guidance sensor

    SciTech Connect

    Aldoretta, E. J.; Gies, D. R.; Henry, T. J.; Jao, W.-C.; Norris, R. P., E-mail: emily@astro.umontreal.ca, E-mail: gies@chara.gsu.edu, E-mail: thenry@chara.gsu.edu, E-mail: jao@chara.gsu.edu, E-mail: norris@chara.gsu.edu [Center for High Angular Resolution Astronomy, Department of Physics and Astronomy, Georgia State University, P. O. Box 5060, Atlanta, GA 30302-5060 (United States); and others

    2015-01-01

    We present the results of an all-sky survey made with the Fine Guidance Sensor on the Hubble Space Telescope to search for angularly resolved binary systems among massive stars. The sample of 224 stars is comprised mainly of Galactic O- and B-type stars and luminous blue variables, plus a few luminous stars in the Large Magellanic Cloud. The FGS TRANS mode observations are sensitive to the detection of companions with an angular separation between 0.?01 and 1.?0 and brighter than ?m=5. The FGS observations resolved 52 binary and 6 triple star systems and detected partially resolved binaries in 7 additional targets (43 of these are new detections). These numbers yield a companion detection frequency of 29% for the FGS survey. We also gathered literature results on the numbers of close spectroscopic binaries and wider astrometric binaries among the sample, and we present estimates of the frequency of multiple systems and the companion frequency for subsets of stars residing in clusters and associations, field stars, and runaway stars. These results confirm the high multiplicity fraction, especially among massive stars in clusters and associations. We show that the period distribution is approximately flat in increments of logP. We identify a number of systems of potential interest for long-term orbital determinations, and we note the importance of some of these companions for the interpretation of the radial velocities and light curves of close binaries that have third companions.

  9. Conceptual Design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) for the Subaru Telescope

    NASA Technical Reports Server (NTRS)

    Peters, Mary Anne; Groff, Tyler; Kasdin, N. Jeremy; McElwain, Michael W.; Galvin, Michael; Carr, Michael A.; Lupton, Robert; Gunn, James E.; Knapp, Gillian; Gong, Qian; Carlotti, Alexis; Brandt, Timothy; Janson, Markus; Guyon, Olivier; Martinache, Frantz; Hayashi, Masahiko; Takato, Naruhisa

    2012-01-01

    Recent developments in high-contrast imaging techniques now make possible both imaging and spectroscopy of planets around nearby stars. We present the conceptual design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), a lenslet-based, cryogenic integral field spectrograph (IFS) for imaging exoplanets on the Subaru telescope. The IFS will provide spectral information for 140 x 140 spatial elements over a 1.75 arcsecs x 1.75 arcsecs field of view (FOV). CHARIS will operate in the near infrared (lambda = 0.9 - 2.5 micron) and provide a spectral resolution of R = 14, 33, and 65 in three separate observing modes. Taking advantage of the adaptive optics systems and advanced coronagraphs (AO188 and SCExAO) on the Subaru telescope, CHARIS will provide sufficient contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets. CHARIS is in the early design phases and is projected to have first light by the end of 2015. We report here on the current conceptual design of CHARIS and the design challenges.

  10. Assessment of anisotropic tissue elasticity of cortical bone from high-resolution, angular acoustic measurements.

    PubMed

    Lakshmanan, Sannachi; Bodi, Andreas; Raum, Kay

    2007-08-01

    Assessment of anisotropic elastic properties at the tissue level is still one of the major challenges in bone research. In previous studies, bone sections were cut in different directions relative to a principle axis of symmetry. This causes a high preparation and measurement effort. We have developed a new acoustic scanning procedure that allows one to measure the angular dependence of the acoustic impedance of cylindrically shaped samples (diameter: 4.4 mm) with a single measurement. Our scanning acoustic microscope was equipped with a rotational stage, and a scanning procedure was developed that measures the surface reflection of the rotating cylinder. It was shown in a previous study that the acoustic impedance derived from the reflection coefficient is highly correlated with the elastic coefficient in the probing direction. From the angular reflection, the independent elastic coefficients were derived using assumptions of transverse isotropy and continuum micromechanical model constraints. This method was applied to the inspection of human femoral bone samples. Four cylinders were prepared from the anterior, posterior, medial, and lateral regions. The measurements were performed with a 50 MHz transducer, providing a lateral resolution of 23 microm. Remarkable structural and elastic variations were observed between the four samples. The means and standard deviations of the derived elastic coefficients were: c33 = 29.9 +/- 5.0 GPa, c11 = 21.9 +/- 2.1 GPa, c12 = 9.2 +/- 1.5 GPa, c13 = 9.7 +/- 1.6 GPa, and c44 = 6.7 +/- 1.2 GPa. The results demonstrate that microstructural and anisotropic elastic tissue parameters can be assessed by ultrasound in very small bone samples. PMID:17703659

  11. Measurement method for roll angular displacement with a high resolution by using diffraction gratings and a heterodyne interferometer

    SciTech Connect

    Tang, Shanzhi, E-mail: shanzhit@gmail.com [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China) [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049 (China); Wang, Zhao [School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049 (China)] [School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049 (China); Gao, Jianmin; Guo, Junjie [State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710054 (China)] [State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710054 (China)

    2014-04-15

    The roll angle measurement is difficult to be achieved directly using a typical commercial interferometer due to its low sensitivity in axial direction, where the axial direction is orthogonal to the plane of the roll angular displacement. A roll angle measurement method combined diffraction gratings with a laser heterodyne interferometer is discussed in this paper. The diffraction grating placed in the plane of a roll angular displacement and the interferometer arranged in the plane's orthogonal direction, constitute the measurement pattern for the roll angle with high resolution. The roll angular displacement, considered as the linear, can be tested precisely when the corresponding angle is very small. Using the proposed method, the angle roll measurement obtains the high resolution of 0.002{sup ?}. Experiment has proved its feasibility and practicability.

  12. The Multiplicity of Massive Stars: a High Angular Resolution Survey With the Guidance Sensor

    NASA Astrophysics Data System (ADS)

    Aldoretta, E. J.; Caballero-Nieves, S. M.; Gies, D. R.; Nelan, E. P.; Wallace, D. J.; Hartkopf, W. I.; Henry, T. J.; Jao, W.-C.; Maíz Apellániz, J.; Mason, B. D.; Moffat, A. F. J.; Norris, R. P.; Richardson, N. D.; Williams, S. J.

    2015-01-01

    We present the results of an all-sky survey made with the Fine Guidance Sensor on the Hubble Space Telescope to search for angularly resolved binary systems among massive stars. The sample of 224 stars is comprised mainly of Galactic O- and B-type stars and luminous blue variables, plus a few luminous stars in the Large Magellanic Cloud. The FGS TRANS mode observations are sensitive to the detection of companions with an angular separation between 0.?01 and 1.?0 and brighter than \\vartriangle m=5. The FGS observations resolved 52 binary and 6 triple star systems and detected partially resolved binaries in 7 additional targets (43 of these are new detections). These numbers yield a companion detection frequency of 29% for the FGS survey. We also gathered literature results on the numbers of close spectroscopic binaries and wider astrometric binaries among the sample, and we present estimates of the frequency of multiple systems and the companion frequency for subsets of stars residing in clusters and associations, field stars, and runaway stars. These results confirm the high multiplicity fraction, especially among massive stars in clusters and associations. We show that the period distribution is approximately flat in increments of log P. We identify a number of systems of potential interest for long-term orbital determinations, and we note the importance of some of these companions for the interpretation of the radial velocities and light curves of close binaries that have third companions. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 11212, 11901, 11943, and 11944.

  13. High angular resolution measurements of K shell x-ray emission created by electron channeling in the analytical electron microscope.

    SciTech Connect

    Zaluzec, N. J.

    1999-03-10

    Since the original observations by Duncumb in 1962, a number of studies have been conducted on the effects of electron channel on characteristic x-ray emission and microanalysis. Most of the recent studies have concentrated upon using the phenomenon to perform site specific distributions of impurity elements in ordered compounds using the ALCHEMI methodology. Very few studies have attempted to accurately measure the effect as a function of orientation and compare these results to theories. In this study, two dimensional high angular resolution studies of channeling enhance x-ray emission were performed and herein the results are compared to theoretical calculations of Allen et al. All experimental measurements presented here were conducted on a Philips EM 420T analytical electron microscope. The instrument was operated in the TEM mode, at 120 kV using an LaB6 electron source. The characteristic x-ray emission was measured using an EDAX ultra thin window Si(Li) detector having a FWHM of {approximately}145 eV at Mn Km Nominal probe sizes used during the study were 200-500 nm with beam convergence half angle defined by the Condenser apertures. Control of the relative orientation of the incident probe was accomplished via direct computer control of the beam tilt coils, after the specimen was first manually oriented to an appropriate zone axis using the specimen tilt stage. Two dimensional measurements were carried out using a 128 x 100 pixel scan corresponding to an angular range of {approximately}100 by 80 mR using customized computer program running on a EDAX 9900 microanalyzer system. Careful alignment and manual optimization/adjustments of beam tilt pivot coils, minimized probe wobble during data acquisition. The effects of this were additionally mitigated due to the relative uniformity of the specimen thickness in the analyzed zone. Typical acquisition times for a complete two dimensional scan were 18-24 hours. Essential to the success of these measurements was the stability of the probe current, minimal specimen drift, and absence of hydrocarbon contamination. The latter being accomplished using argon plasma processing of the specimen (MgAl{sub 2}O{sub 4}) which was initially prepared by mechanical tripod polishing.

  14. Submillimeter Array High-angular Resolution Observations of the Monoceros R2 Star-forming Cluster

    NASA Astrophysics Data System (ADS)

    Dierickx, M.; Jiménez-Serra, I.; Rivilla, V. M.; Zhang, Q.

    2015-04-01

    We present the first high-angular resolution study of the MonR2 star-forming complex carried out with the Submillimeter Array at (sub-)millimeter wavelengths. We image the continuum and molecular line emission toward the young stellar objects in MonR2 at 0.85 and 1.3 mm, with resolutions ranging from 0.? 5 to ?3?. While free–free emission dominates the IRS1 and IRS2 continuum, dust thermal emission prevails for IRS3 and IRS5, giving envelope masses of ?0.1–0.3 {{M}? }. IRS5 splits into at least two sub-arcsecond scale sources, IRS5B and the more massive IRS5A. Our 12CO(2-1) images reveal 11 previously unknown molecular outflows in the MonR2 clump. Comparing these outflows with known IR sources in the IRS5 and IRS3 subclusters allows for tentative identification of driving stars. Line images of molecular species such as CH3CN or CH3OH show that, besides IRS3 (a well-known hot molecular core), IRS5 is also a chemically active source in the region. The gas excitation temperature derived from CH3CN lines toward IRS5 is 144 ± 15 K, indicating a deeply embedded protostar at the hot-core evolutionary stage. Spectral energy distribution fitting of IRS5 gives a mass of ?7 M ? and a luminosity of 300 {{L}? } for the central source. The derived physical properties of the CO outflows suggest that they contribute to the turbulent support of the MonR2 complex and to the gas velocity dispersion in the clump’s center. The detection of a large number of CO outflows widespread across the region supports the competitive accretion scenario as origin of the MonR2 star cluster.

  15. European Extremely Large Telescope Site Characterization II: High angular resolution parameters

    E-print Network

    Ramió, Héctor Vázquez; Muñoz-Tuñón, Casiana; Sarazin, Marc; Varela, Antonia M; Trinquet, Hervé; Delgado, José Miguel; Fuensalida, Jesús J; Reyes, Marcos; Benhida, Abdelmajid; Benkhaldoun, Zouhair; Lambas, Diego García; Hach, Youssef; Lazrek, M; Lombardi, Gianluca; Navarrete, Julio; Recabarren, Pablo; Renzi, Victor; Sabil, Mohammed; Vrech, Rubén

    2012-01-01

    This is the second article of a series devoted to European Extremely Large Telescope (E-ELT) site characterization. In this article we present the main properties of the parameters involved in high angular resolution observations from the data collected in the site testing campaign of the E-ELT during the Design Study (DS) phase. Observations were made in 2008 and 2009, in the four sites selected to shelter the future E-ELT (characterized under the ELT-DS contract): Aklim mountain in Morocco, Observatorio del Roque de los Muchachos (ORM) in Spain, Mac\\'on range in Argentina, and Cerro Ventarrones in Chile. The same techniques, instruments and acquisition procedures were taken on each site. A Multiple Aperture Scintillation Sensor (MASS) and a Differential Image Motion Monitor (DIMM) were installed at each site. Global statistics of the integrated seeing, the free atmosphere seeing, the boundary layer seeing and the isoplanatic angle were studied for each site, and the results are presented here. In order to e...

  16. First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region

    E-print Network

    Partnership, ALMA; Perez, L M; Hunter, T R; Dent, W R F; Hales, A S; Hills, R; Corder, S; Fomalont, E B; Vlahakis, C; Asaki, Y; Barkats, D; Hirota, A; Hodge, J A; Impellizzeri, C M V; Kneissl, R; Liuzzo, E; Lucas, R; Marcelino, N; Matsushita, S; Nakanishi, K; Phillips, N; Richards, A M S; Toledo, I; Aladro, R; Broguiere, D; Cortes, J R; Cortes, P C; Dhawan, V; Espada, D; Galarza, F; Garcia-Appadoo, D; Guzman-Ramirez, L; Humphreys, E M; Jung, T; Kameno, S; Laing, R A; Leon, S; Marconi, G; Nikolic, B; Nyman, L -A; Radiszcz, M; Remijan, A; Rodon, J A; Sawada, T; Takahashi, S; Tilanus, R P J; Vilaro, B Vila; Watson, L C; Wiklind, T; Akiyama, E; Chapillon, E; de Gregorio, I; Di Francesco, J; Gueth, F; Kawamura, A; Lee, C -F; Luong, Q Nguyen; Mangum, J; Pietu, V; Sanhueza, P; Saigo, K; Takakuwa, S; Ubach, C; van Kempen, T; Wootten, A; Castro-Carrizo, A; Francke, H; Gallardo, J; Garcia, J; Gonzalez, S; Hill, T; Kaminski, T; Kurono, Y; Liu, H -Y; Lopez, C; Morales, F; Plarre, K; Schieven, G; Testi, L; Videla, L; Villard, E; Andreani, P; Hibbard, J E; Tatematsu, K

    2015-01-01

    We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0.075 arcseconds (10 AU) to 0.025 arcseconds (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analogue HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46.72pm0.05 degrees) and position angle (+138.02pm0.07 degrees). We obtain a high-fidelity image of the 1.0 mm spectral index ($\\alpha$), which ranges from $\\alpha\\sim2.0$ in the optically-thick central peak and two brightest rings, increasing to 2.3-3.0 in the dark rings. The dark rings are not devoid of emission, we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for ...

  17. Segmentation of High Angular Resolution Diffusion MRI using Sparse Riemannian Manifold Clustering

    PubMed Central

    Wright, Margaret J.; Thompson, Paul M.; Vidal, René

    2015-01-01

    We address the problem of segmenting high angular resolution diffusion imaging (HARDI) data into multiple regions (or fiber tracts) with distinct diffusion properties. We use the orientation distribution function (ODF) to represent HARDI data and cast the problem as a clustering problem in the space of ODFs. Our approach integrates tools from sparse representation theory and Riemannian geometry into a graph theoretic segmentation framework. By exploiting the Riemannian properties of the space of ODFs, we learn a sparse representation for each ODF and infer the segmentation by applying spectral clustering to a similarity matrix built from these representations. In cases where regions with similar (resp. distinct) diffusion properties belong to different (resp. same) fiber tracts, we obtain the segmentation by incorporating spatial and user-specified pairwise relationships into the formulation. Experiments on synthetic data evaluate the sensitivity of our method to image noise and the presence of complex fiber configurations, and show its superior performance compared to alternative segmentation methods. Experiments on phantom and real data demonstrate the accuracy of the proposed method in segmenting simulated fibers, as well as white matter fiber tracts of clinical importance in the human brain. PMID:24108748

  18. European Extremely Large Telescope Site Characterization. II. High Angular Resolution Parameters

    NASA Astrophysics Data System (ADS)

    Vázquez Ramió, Héctor; Vernin, Jean; Muñoz-Tuñón, Casiana; Sarazin, Marc; Varela, Antonia M.; Trinquet, Hervé; Delgado, José Miguel; Fuensalida, Jesús J.; Reyes, Marcos; Benhida, Abdelmajid; Benkhaldoun, Zouhair; Lambas, Diego García; Hach, Youssef; Lazrek, M.; Lombardi, Gianluca; Navarrete, Julio; Recabarren, Pablo; Renzi, Victor; Sabil, Mohammed; Vrech, Rubén

    2012-08-01

    This is the second article of a series devoted to European Extremely Large Telescope (E-ELT) site characterization. In this article we present the main properties of the parameters involved in high angular resolution observations from the data collected in the site testing campaign of the E-ELT during the design study (DS) phase. Observations were made in 2008 and 2009, in the four sites selected to shelter the future E-ELT (characterized under the ELT-DS contract): Aklim mountain in Morocco, Observatorio del Roque de los Muchachos (ORM) in Spain, Macón range in Argentina, and Cerro Ventarrones in Chile. The same techniques, instruments, and acquisition procedures were taken on each site. A multiple aperture scintillation sensor (MASS) and a differential image motion monitor (DIMM) were installed at each site. Global statistics of the integrated seeing, the free atmosphere seeing, the boundary layer seeing, and the isoplanatic angle were studied for each site, and the results are presented here. In order to estimate other important parameters, such as the coherence time of the wavefront and the overall parameter "coherence étendue," additional information of vertical profiles of the wind speed was needed. Data were retrieved from the National Oceanic and Atmospheric Administration (NOAA) archive. Ground wind speed was measured by automatic weather stations (AWS). More aspects of the turbulence parameters, such as their seasonal trend, their nightly evolution, and their temporal stability, were also obtained and analyzed.

  19. Development of insula connectivity between ages 12 and 30 revealed by high angular resolution diffusion imaging.

    PubMed

    Dennis, Emily L; Jahanshad, Neda; McMahon, Katie L; de Zubicaray, Greig I; Martin, Nicholas G; Hickie, Ian B; Toga, Arthur W; Wright, Margaret J; Thompson, Paul M

    2014-04-01

    The insula, hidden deep within the Sylvian fissures, has proven difficult to study from a connectivity perspective. Most of our current information on the anatomical connectivity of the insula comes from studies of nonhuman primates and post mortem human dissections. To date, only two neuroimaging studies have successfully examined the connectivity of the insula. Here we examine how the connectivity of the insula develops between ages 12 and 30, in 307 young adolescent and adult subjects scanned with 4-Tesla high angular resolution diffusion imaging (HARDI). The density of fiber connections between the insula and the frontal and parietal cortex decreased with age, but the connection density between the insula and the temporal cortex generally increased with age. This trajectory is in line with well-known patterns of cortical development in these regions. In addition, males and females showed different developmental trajectories for the connection between the left insula and the left precentral gyrus. The insula plays many different roles, some of them affected in neuropsychiatric disorders; this information on the insula's connectivity may help efforts to elucidate mechanisms of brain disorders in which it is implicated. PMID:23836455

  20. High angular resolution diffusion imaging with stimulated echoes: compensation and correction in experiment design and analysis

    PubMed Central

    Lundell, Henrik; Alexander, Daniel C; Dyrby, Tim B

    2014-01-01

    Stimulated echo acquisition mode (STEAM) diffusion MRI can be advantageous over pulsed-gradient spin-echo (PGSE) for diffusion times that are long compared with T2. It therefore has potential for biomedical diffusion imaging applications at 7T and above where T2 is short. However, gradient pulses other than the diffusion gradients in the STEAM sequence contribute much greater diffusion weighting than in PGSE and lead to a disrupted experimental design. Here, we introduce a simple compensation to the STEAM acquisition that avoids the orientational bias and disrupted experiment design that these gradient pulses can otherwise produce. The compensation is simple to implement by adjusting the gradient vectors in the diffusion pulses of the STEAM sequence, so that the net effective gradient vector including contributions from diffusion and other gradient pulses is as the experiment intends. High angular resolution diffusion imaging (HARDI) data were acquired with and without the proposed compensation. The data were processed to derive standard diffusion tensor imaging (DTI) maps, which highlight the need for the compensation. Ignoring the other gradient pulses, a bias in DTI parameters from STEAM acquisition is found, due both to confounds in the analysis and the experiment design. Retrospectively correcting the analysis with a calculation of the full B matrix can partly correct for these confounds, but an acquisition that is compensated as proposed is needed to remove the effect entirely. PMID:24890716

  1. Exploring AGNs in the Local Universe through High Angular Resolution Spectroscopy and Optical Variability Monitoring

    NASA Astrophysics Data System (ADS)

    Walsh, Jonelle L.

    This dissertation presents the results of several observational projects designed to explore AGNs, on scales of about 100 pc and smaller, in nearby galaxies. High angular resolution spectroscopy acquired from HST STIS and Keck LGS AO OSIRIS observations are used to study the kinematic structure of gas disks and stars on scales comparable to the gravitational sphere of influence of the supermassive black hole. Specifically, I use multi-slit STIS data of low-luminosity AGNs to map out the emission-line kinematics, and to look for regularly rotating velocity fields suitable for future gas dynamical black hole mass measurements. The HST data is further useful for searching for electron-density gradients and for examining how the emission-line velocity dispersion varies as a function of aperture size. In another project, I aim to resolve a discrepancy between two previous gas dynamical measurements of the black hole in the elliptical galaxy M84. I perform new measurements of the gas kinematics from archival multi-slit STIS data, and carry out a more comprehensive dynamical model of the emission-line disk than had been previously attempted. With the most recent project, I measure high-resolution stellar kinematics from LGS AO OSIRIS data and large-scale kinematics from long-slit LRIS data of the S0 galaxy NGC 3998. Using triaxial orbit-based stellar dynamical models, I determine the black hole mass. The stellar dynamical value is then compared to a previous gas dynamical determination in order to test the consistency between these two main mass measurement methods. In addition to using high spatial resolution spectroscopy, AGN variability can be used to probe the inner regions of AGNs. The Lick AGN Monitoring Project targeted 12 galaxies expected to harbor low-mass black holes. Through reverberation mapping, the collaboration measured the masses of nine black holes, and learned about the geometry and kinematics of the broad-line region in several of the objects. I discuss my contribution to the project: measuring the AGN continuum from broadband B and V images. I also examine continuum variability characteristics, search for time lags between B - and V -band variations, and look for fluctuations in the AGN color.

  2. Recent Advances in Multi-Resolution Approximation for Modeling and Control

    E-print Network

    Krstic, Miroslav

    Recent Advances in Multi-Resolution Approximation for Modeling and Control John L. Junkins Texas A approximations. This lecture introduces essential ideas and explores a few applications in nonlinear dynamics characterizing the evolution of uncertain nonlinear system dynamics. In the latter application, some problems

  3. PREFACE: The Universe under the Microscope: Astrophysics at High Angular Resolution

    NASA Astrophysics Data System (ADS)

    Schödel, Rainer

    2009-01-01

    High angular resolution techniques at infrared and centimeter to millimeter wavelengths have become of ever increasing importance for astrophysical research in the past decade. They have led to important breakthroughs, like the direct imaging of protoplanetary discs and of the first exoplanets, the measurement of stellar orbits around the black hole at the center of the Milky Way, or the detection of sub-parsec-scale jets in low luminosity AGN. With adaptive optics in a mature state, infrared/optical astronomy is pushing toward extreme adaptive optics, extremely large telescopes, and infrared/optical interferometry with large aperture telescopes. At longer wavelengths, large arrays start to conquer the sub-millimeter window, with the mid-term goal of global VLBI at sub-millimeter wavelengths. These new techniques will have enormous impact on the field because they will enable us to address issues such as directly measuring the properties of exoplanets, imaging the surfaces of stars, examining stellar dynamics in extremely dense cluster cores, disentangling the processes at the bottom of black hole accretion flows in the jet launching region, or testing general relativity in the strong gravity regime near the event horizon of supermassive black holes. The conference The Universe under the Microscope: Astrophysics at High Angular Resolution, held at the Physikzentrum of the Deutsche Physikalische Gesellschaft in Bad Honnef, Germany, on 12-25 April 2008, aimed at an interdisciplinary approach by bringing together astrophysicists from the three great branches of the field, instrumentation, observation, and theory, to discuss the current state of research and the possibilities offered by the next-generation instruments. Editors of the proceedings Rainer Schödel Instituto de Astrofísica de Andalucía -CSIC, Granada, Spain Andreas Eckart I. Physikalisches Institut der Universität zu Köln, Köln, Germany Susanne Pfalzner I. Physikalisches Institut der Universität zu Köln, Köln, Germany Eduardo Ros Max-Planck-Institut für extraterrestrische Physik, Bonn, Germany Scientific organizing committee Dennis Downes Institut de Radio Astronomie Millimétrique, France Wolfgang Duschl University of Kiel, Germany Andrea Ghez University of California, Los Angeles, USA Vladimir Karas Academy of Sciences, Czech Republic Andreas Eckart University of Cologne, Germany Sera Marko University of Amsterdam, The Netherlands Susanne Pfalzner University of Cologne, Germany Sebastian Rabien Max-Planck-Institute for Extraterrestrial Physics, Germany Daniel Rouan Observatoire de Paris-Meudon, France Eduardo Ros Max-Planck-Institute for Radio Astronomy, Germany Rainer Schödel Instituto de Astrofísica de Andalucía -CSIC, Spain Zhiqiang Shen Shanghai Astronomical Observatory, China Anton Zensus Max-Planck-Institute for Radio Astronomy, Germany Local organizing committee Sebastian Fischer University of Cologne, Germany Devaky Kunneriath University of Cologne, Germany Leo Meyer University of Cologne, Germany Koraljka Muzic University of Cologne, Germany Rainer Schödel University of Cologne, Germany/IAA -CSIC, Spain Christian Straubmeier University of Cologne, Germany Mohammad Zamaninasab University of Cologne, Germany

  4. Sex differences in the human connectome: 4Tesla high angular resolution diffusion imaging (HARDI) tractography in 234 young adult twins

    Microsoft Academic Search

    Neda Jahanshad; Iman Aganj; Christophe Lenglet; Anand Joshi; Yan Jin; Marina Barysheva; Katie L. McMahon; Greig I. de Zubicaray; Nicholas G. Martin; Margaret J. Wright; Arthur W. Toga; Guillermo Sapiro; Paul M. Thompson

    2011-01-01

    Cortical connectivity is associated with cognitive and behavioral traits that are thought to vary between sexes. Using high-angular resolution diffusion imaging at 4 Tesla, we scanned 234 young adult twins and siblings (mean age: 23.4 ± 2.0 SD years) with 94 diffusion-encoding directions. We applied a novel Hough transform method to extract fiber tracts throughout the entire brain, based on

  5. SOUTHERN MASSIVE STARS AT HIGH ANGULAR RESOLUTION: OBSERVATIONAL CAMPAIGN AND COMPANION DETECTION

    SciTech Connect

    Sana, H. [European Space Agency/Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Le Bouquin, J.-B.; Duvert, G.; Zins, G. [Université Grenoble Alpes, IPAG, F-38000 Grenoble (France); Lacour, S.; Gauchet, L.; Pickel, D. [LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, Paris Sciences et Lettres, 5 Place Jules Janssen, F-92195 Meudon (France); Berger, J.-P. [European Southern Observatory, Schwarzschild-Str. 2, D-85748 Garching bei München (Germany); Norris, B. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Olofsson, J. [Max-Planck-Institut für Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Absil, O. [Département d'Astrophysique, Géophysique et Océanographie, Université de Liège, 17 Allée du Six Août, B-4000 Liège (Belgium); De Koter, A. [Astrophysical Institute Anton Pannekoek, Universiteit van Amsterdam, Science Park 904, 1098XH Amsterdam (Netherlands); Kratter, K. [JILA, 440 UCB, University of Colorado, Boulder, CO 80309-0440 (United States); Schnurr, O. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Zinnecker, H., E-mail: hsana@stsci.edu [Deutsches SOFIA Instituut, SOFIA Science Center, NASA Ames Research Center, Mail Stop N232-12, Moffett Field, CA 94035 (United States)

    2014-11-01

    Multiplicity is one of the most fundamental observable properties of massive O-type stars and offers a promising way to discriminate between massive star formation theories. Nevertheless, companions at separations between 1 and 100 milliarcsec (mas) remain mostly unknown due to intrinsic observational limitations. At a typical distance of 2 kpc, this corresponds to projected physical separations of 2-200 AU. The Southern MAssive Stars at High angular resolution survey (SMaSH+) was designed to fill this gap by providing the first systematic interferometric survey of Galactic massive stars. We observed 117 O-type stars with VLTI/PIONIER and 162 O-type stars with NACO/Sparse Aperture Masking (SAM), probing the separation ranges 1-45 and 30-250 mas and brightness contrasts of ?H < 4 and ?H < 5, respectively. Taking advantage of NACO's field of view, we further uniformly searched for visual companions in an 8'' radius down to ?H = 8. This paper describes observations and data analysis, reports the discovery of almost 200 new companions in the separation range from 1 mas to 8'' and presents a catalog of detections, including the first resolved measurements of over a dozen known long-period spectroscopic binaries. Excluding known runaway stars for which no companions are detected, 96 objects in our main sample (? < 0°; H < 7.5) were observed both with PIONIER and NACO/SAM. The fraction of these stars with at least one resolved companion within 200 mas is 0.53. Accounting for known but unresolved spectroscopic or eclipsing companions, the multiplicity fraction at separation ? < 8'' increases to f {sub m} = 0.91 ± 0.03. The fraction of luminosity class V stars that have a bound companion reaches 100% at 30 mas while their average number of physically connected companions within 8'' is f {sub c} = 2.2 ± 0.3. This demonstrates that massive stars form nearly exclusively in multiple systems. The nine non-thermal radio emitters observed by SMaSH+ are all resolved, including the newly discovered pairs HD 168112 and CPD–47°2963. This lends strong support to the universality of the wind-wind collision scenario to explain the non-thermal emission from O-type stars.

  6. Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection

    NASA Astrophysics Data System (ADS)

    Sana, H.; Le Bouquin, J.-B.; Lacour, S.; Berger, J.-P.; Duvert, G.; Gauchet, L.; Norris, B.; Olofsson, J.; Pickel, D.; Zins, G.; Absil, O.; de Koter, A.; Kratter, K.; Schnurr, O.; Zinnecker, H.

    2014-11-01

    Multiplicity is one of the most fundamental observable properties of massive O-type stars and offers a promising way to discriminate between massive star formation theories. Nevertheless, companions at separations between 1 and 100 milliarcsec (mas) remain mostly unknown due to intrinsic observational limitations. At a typical distance of 2 kpc, this corresponds to projected physical separations of 2-200 AU. The Southern MAssive Stars at High angular resolution survey (SMaSH+) was designed to fill this gap by providing the first systematic interferometric survey of Galactic massive stars. We observed 117 O-type stars with VLTI/PIONIER and 162 O-type stars with NACO/Sparse Aperture Masking (SAM), probing the separation ranges 1-45 and 30-250 mas and brightness contrasts of ?H < 4 and ?H < 5, respectively. Taking advantage of NACO's field of view, we further uniformly searched for visual companions in an 8'' radius down to ?H = 8. This paper describes observations and data analysis, reports the discovery of almost 200 new companions in the separation range from 1 mas to 8'' and presents a catalog of detections, including the first resolved measurements of over a dozen known long-period spectroscopic binaries. Excluding known runaway stars for which no companions are detected, 96 objects in our main sample (? < 0° H < 7.5) were observed both with PIONIER and NACO/SAM. The fraction of these stars with at least one resolved companion within 200 mas is 0.53. Accounting for known but unresolved spectroscopic or eclipsing companions, the multiplicity fraction at separation ? < 8'' increases to f m = 0.91 ± 0.03. The fraction of luminosity class V stars that have a bound companion reaches 100% at 30 mas while their average number of physically connected companions within 8'' is f c = 2.2 ± 0.3. This demonstrates that massive stars form nearly exclusively in multiple systems. The nine non-thermal radio emitters observed by SMaSH+ are all resolved, including the newly discovered pairs HD 168112 and CPD-47°2963. This lends strong support to the universality of the wind-wind collision scenario to explain the non-thermal emission from O-type stars.

  7. A high angular resolution survey of circumstellar dust around Herbig Ae/Be stars

    NASA Astrophysics Data System (ADS)

    Perrin, Marshall Dimsey

    This thesis presents the development of a sensitive near-infrared differential imaging polarimeter, and its subsequent use, combined with mid infrared imaging, to survey circumstellar dust around 110 Herbig Ae/Be stars. Planets are born in dusty circumstellar disks around young stars. By imaging such disks we can learn about the environment and physical processes that assemble planets from primordial dust and gas. But these observations are challenging on account of the high angular resolution and high dynamic range necessary to detect the disk's faint reflected light against a far brighter background of stellar light. One powerful method for obtaining the necessary contrast is the use of differential polarimetry to separate polarized dust-scattered light from unpolarized starlight. For this reason, I have developed a differential polarimetry mode for IRCAL, the adaptive optics science camera at Lick Observatory, which uses a YLF Wollaston prism beamsplitter to attenuate 98-99% of stellar light. I describe this instrument, summarize the data reduction and image analysis algorithms employed, and discuss lessons learned for future high-contrast imaging systems. A second strategy for high contrast science is to obtain observations at mid-infrared wavelengths, where dust is bright and stellar light is comparatively faint. These two techniques are complementary, respectively probing scattered and thermal light, and their multiwavelength combination can help constrain numerical models of circumstellar disks and envelopes. I have obtained near-IR adaptive optics imaging polarimetry and mid-IR imaging of a large sample of Herbig Ae/Be stars; 110 targets were observed with AO polarimetry and 61 with mid-IR imaging. Of these stars, 40 are found to have extended polarized nebulosity arising from scattered light. The dust geometry is highly variable, ranging from circumstellar disks to envelopes split by bipolar outflow cavities to complex arcs and lanes of dust spiraling around and between stars. I present detailed studies of a subset of these objects, including laser guide star AO observations of disks and envelopes around the stars LkHalpha 198 and LkHalpha 233; the discovery of the first resolved edge-on circumstellar disk around a Herbig Ae/Be star, PDS 144 N; and integral field spectroscopy of a narrowly collimated bipolar outflow from LkHalpha 233. I conclude by discussing future prospects for advances in the studies of circumstellar disks with the coming generation of high contrast instruments.

  8. Characterization of anisotropy in high angular resolution diffusion-weighted MRI

    Microsoft Academic Search

    Lawrence R. Frank

    2002-01-01

    The methods of group theory are applied to the problem of characterizing the diffusion measured in high angular resolu- tion MR experiments. This leads to a natural representation of the local diffusion in terms of spherical harmonics. In this rep- resentation, it is shown that isotropic diffusion, anisotropic diffusion from a single fiber, and anisotropic diffusion from multiple fiber directions

  9. High angular-resolution automated visible-wavelength scanning angle Raman microscopy.

    PubMed

    Lesoine, Michael D; Bobbitt, Jonathan M; Zhu, Shaobin; Fang, Ning; Smith, Emily A

    2014-10-27

    A scanning angle (SA) Raman microscope with 532-nm excitation is reported for probing chemical content perpendicular to a sample interface. The instrument is fully automated to collect Raman spectra across a range of incident angles from 20.50 to 79.50° with an angular spread of 0.4±0.2° and an angular uncertainty of 0.09°. Instrumental controls drive a rotational stage with a fixed axis of rotation relative to a prism-based sample interface mounted on an inverted microscope stage. Three benefits of SA Raman microscopy using visible wavelengths, compared to near infrared wavelengths are: (i) better surface sensitivity; (ii) increased signal due to the frequency to the fourth power dependence of the Raman signal, and the possibility for resonant enhancement; (iii) the need to scan a reduced angular range to shorten data collection times. These benefits were demonstrated with SA Raman measurements of thin polymer films of polystyrene or a diblock copolymer of polystyrene and poly(3-hexylthiophene-2,5-diyl). Thin film spectra were collected with a signal-to-noise ratio of 30 using a 0.25 s acquisition time. PMID:25263117

  10. Young binary systems and their nearby environment: high-angular resolution observations

    NASA Astrophysics Data System (ADS)

    Duchêne, Gaspard

    2000-07-01

    The high frequency of binary systems among main sequence stars as well as in star-forming regions has been largely documented in the last ten years. This raised the issue of the mechanism responsible for the preferred occurence of multiple systems. Moreover, interactions between a companion and the complex environment of a T Tauri star are only poorly understood. The work conducted during this thesis fits in this framework; the main goals of the thesis are: i) to estimate the binary frequency in various populations of pre-main sequence stars, ii) to study quantitatively the accretion phenomenon in binary T Tauri stars, and iii) to get direct observations and to model circumstellar and circumbinary disks in these systems. Using the Canada-France-Hawaii Telescope adaptive optics system to search for visual binaries, I took part in the observations of several hundreds objects located in various young stellar clusters. Here, I detail the analysis and results concerning two two-million years-old clusters, IC 348 and NGC 6611. When considering all populations studied to date, we find that the visual binary frequency among solar-type stars is the same in all stellar clusters as on the main sequence. Furthermore, this property does not depend on the age of the cluster, indicating that the binary frequency does not evolve after the first million years in these clusters. On the other hand, the extremely young loose star-forming regions display a significatively enhanced binary frequency. The models that best fit these observations are those where the binary frequency resulting from the gravitational collapse is close to 100%. In the densest clusters, this frequency can be subsequently decreased due to the numerous disrupting gravitational encounters between systems. OB stars in NGC 6611 retain significantly more companions in the separation range 200--2000 AU than low-mass objects in closer similarly-aged clusters, when one tries to account for uncompleteness in the observations. I then focus on the accretion phenomenon in binary T Tauri systems using spatially-resolved optical spectroscopy of 125--1400 AU binary systems in Taurus. This approach reveals that the accretion phenomenon lasts over the same time span on both components of a binary system. Furthermore, the comparison of the H? emission line luminosities suggests that the accretion rate is higher on the primary than on its companion. These results may be explained by the presence of a mass reservoir around the binary; this enveloppe would feed simultaneously both circumstellar disks. I finally present some high-angular resolution images of the GG Tau and UY Aur circumbinary rings and of the HK Tau B and HV Tau C circumstellar disks. These observations were obtained in the optical, the near-infrared and the millimetric ranges, and they allow an accurate description of the environment of these binary systems. I also analyze in details 1 micron polarimetric maps obtained with HST/NICMOS of the two circumbinary disks. In order to estimate the geometrical properties of these disks, as well as their dust grain properties, I performed Monte-Carlo modelling to describe photon multiple scattering and try to reproduce both the observed shape and the polarization level of the disks. This study confirms that the GG Tau circumbinary ring is geometrically thick (its aspect ratio is h/r~0.18), that small dust grains (<1 micron) are still present, and that the dust mass in the ring is at least 10-3 Modot. The UY Aur environment appears much more complex than that of GG Tau: the circumbinary disk, whose inclination is re-estimated to about 60°, coexists with a filament of material which is close to it but appears independent, and several arcs seem to get away from the main disk, one of which getting close to the stars. The scattering modelg reproduces the observations provided that the dust mass in the circumbinary disk is at least 10-3 Modot, in order to account for the non-detection of the back side of the disk from 6000 Å to 2 microns.

  11. The Lunar Reconnaissance Orbiter (LRO) Lunar Epithermal Neutron Detector (LEND): GOING BEYOND NOMINAL ANGULAR RESOLUTION

    NASA Astrophysics Data System (ADS)

    Nandikotkur, G.; Usikov, D.; McClanahan, T. P.; Sagdeev, R.; Milikh, G. M.; Chin, G.; SU, J.; Khachatryan, R.

    2012-12-01

    Since the launch of the Lunar Reconnaissance Orbiter (LRO) in 2009, the omnidirectional channels of the Lunar Epithermal Neutron Detector (LEND) for epithermal neutrons (SETN) have accumulated more than 109 neutron events. This neutron data have been used to map the entire Moon with a nominal resolution of ~60 km from a circular orbit altitude of ~50 km. This large volume of neutron data (still being accumulated at 10 cps) can now provide sufficiently high signal-to-noise maps that can be used to apply deconvolution techniques to improve the resolution of these moderate resolution data. We applied different computational techniques of deconvolution such as Conjugate Gradient, Iterative Gaussian Smoothing, Weiner and Regularized Deconvolution [1] to construct "super-resolution " maps (up to 20 km) for a few selected areas with most pronounced presence of hydrogen (Shoemaker PSR, NSRs, and others). This improved resolution maps from the uncollimated data then will be compared to the collimated LEND maps to assess the efficacy of the super-resolution methods and will allow these techniques to be used to provide more detailed comparisons of the uncollimated neutron data with lunar topographic features. References: [1] McClanahan T.P. et al. (2010), Computers & Geosciences, 36, 1484-1493.

  12. Angular effects and correction on medium resolution sensors for crop monitoring

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Remote sensing imagery at medium spatial resolutions (20-60m) such as Landsat, the Advanced Wide Field Sensor (AWiFS) and the Disaster Monitoring Constellation (DMC) have been broadly used in mapping crop types and monitoring crop conditions. This paper examined the influence of viewing and illumina...

  13. Sigma - A new gamma-ray space observatory with high angular resolution for 1985 and beyond

    NASA Astrophysics Data System (ADS)

    Debouzy, G.

    The primary objective of the Satellite d'Imagerie Gamma Montesur Ariane (SIGMA) is the acquisition of images of the sky in the hard X-ray/low energy gamma-ray domains, which cover the 30 keV-2 MeV range, with an angular accuracy of a few arcmin and a point source sensitivity as low as a few UHURU Flux Units. In order to fulfill these requirements, a large, position-sensitive detector operating with a coded aperture mask will be employed. While the sensitivity of the SIGMA detector can be derived easily in the low energy domain, where the photoelectric effect predominates, background estimation has required detailed Monte-Carlo simulations.

  14. Sigma: a new gamma-ray space observatory with high angular resolution for 1985 and beyond

    SciTech Connect

    Debouzy, G.

    1983-01-01

    The primary objective of the Satellite d'Imagerie Gamma Montesur Ariane (SIGMA) is the acquisition of images of the sky in the hard X-ray/low energy gamma-ray domains, which cover the 30 keV-2 MeV range, with an angular accuracy of a few arcmin and a point source sensitivity as low as a few UHURU Flux Units. In order to fulfill these requirements, a large, position-sensitive detector operating with a coded aperture mask will be employed. While the sensitivity of the SIGMA detector can be derived easily in the low energy domain, where the photoelectric effect predominates, background estimation has required detailed Monte-Carlo simulations.

  15. High angular resolution far-infrared and submillimeter mapping survey of the dust cores associated with ultracompact H II regions

    NASA Technical Reports Server (NTRS)

    Phillips, T. G.

    1995-01-01

    The primary objective of the research funded under this grant has been to perform a high angular resolution mapping survey of the far-infrared and submillimeter continuum emission from the dust cocoons surrounding young, deeply embedded massive stars and the ultracompact H II regions they create. The high infrared, submillimeter, and radio luminosity makes the ultracompact H II regions ideal tracers of current high-mass star formation. Detailed investigations of their structure, evolution, and interaction with their parent molecular clouds are thus important for understanding the early evolutionary phases of massive main sequence stars, the nature of the dense molecular cores in which they form, and the relationship to coeval low-mass star formation.

  16. Tiny twists in time; exploring angular resolution of in situ EBSD orientation microstructures in solar system zircon

    NASA Astrophysics Data System (ADS)

    Moser, D. E.

    2012-12-01

    Kikuchi discovered electron diffraction in samples of calcite in the 1920's, and orientation of lattice planes by Electron Backscatter Diffraction (EBSD) is now routinely measured by automated camera systems at a spatial resolution of tens of nanometers using Field Emission Gun SEM. The current methodology is proving particularly powerful when measuring lattice orientation microstructure in U-Pb geochronology minerals such as zircon and baddeleyite that have experienced high temperature deformation or shock metamorphism. These are among the oldest preserved mineral phases in inner solar system materials, and we have been applying EBSD to rare samples of the Early Earth and grains from extraterrestrial environments such as the Moon and Mars. In these cases the EBSD orientation data are useful for identifying high diffusivity pathways that may have afforded isotopic and trace element disturbance, microstructural proxies for shock metamorphic pressures, as well as resolving glide plane systems in ductile zircon and shear twin mechanisms. Blanket estimates of angular resolution for automated EBSD misorientation measurements are often in the range of 0.5 degrees. In some cases strain giving rise to only a few degrees of lattice misorientation has facilitated 100% Pb-loss. In some cases, however, there is a spatial correlation between trace element or cathodoluminescence zoning in zircon and what appears to be low magnitudes misorientation close to the limits of resolution. Given the proven value of performing EBSD analysis on geochronology minerals, a more thorough exploration of the precision and accuracy of EBSD lattice misorientation measurements is warranted. In this talk the relative weighting of the factors that limit EBSD angular resolution will be investigated, focusing on U-Pb dating minerals such as zircon. These factors include; sample surface preparation, phase symmetry, pseudo-symmetry effects, degree of crystallinity, Kikuchi band contrast and indexing, solid solution effects on unit cell, dimension camera calibration and camera-sample distance, beam conditions and focussing, and general microscope operating conditions (e.g. high vacuum vs. variable pressure). An assessment of potential zircon EBSD reference materials and sample preparation protocols will be presented, along with case studies of zircon orientation microstructures from meteorites and terrestrial craters representative of different strain and thermal environments in the inner solar system.BSD lattice misorientation maps of a) crystal-plastically deformed and partly recrystallized zircon, after Rayner et al. (in prep.), and b) shock-metamorphosed lunar zircon (Darling et al., in prep.).

  17. In vivo High Angular Resolution Diffusion-Weighted Imaging of Mouse Brain at 16.4 Tesla

    PubMed Central

    Alomair, Othman I.; Brereton, Ian M.; Smith, Maree T.; Galloway, Graham J.; Kurniawan, Nyoman D.

    2015-01-01

    Magnetic Resonance Imaging (MRI) of the rodent brain at ultra-high magnetic fields (> 9.4 Tesla) offers a higher signal-to-noise ratio that can be exploited to reduce image acquisition time or provide higher spatial resolution. However, significant challenges are presented due to a combination of longer T1 and shorter T2/T2* relaxation times and increased sensitivity to magnetic susceptibility resulting in severe local-field inhomogeneity artefacts from air pockets and bone/brain interfaces. The Stejskal-Tanner spin echo diffusion-weighted imaging (DWI) sequence is often used in high-field rodent brain MRI due to its immunity to these artefacts. To accurately determine diffusion-tensor or fibre-orientation distribution, high angular resolution diffusion imaging (HARDI) with strong diffusion weighting (b >3000 s/mm2) and at least 30 diffusion-encoding directions are required. However, this results in long image acquisition times unsuitable for live animal imaging. In this study, we describe the optimization of HARDI acquisition parameters at 16.4T using a Stejskal-Tanner sequence with echo-planar imaging (EPI) readout. EPI segmentation and partial Fourier encoding acceleration were applied to reduce the echo time (TE), thereby minimizing signal decay and distortion artefacts while maintaining a reasonably short acquisition time. The final HARDI acquisition protocol was achieved with the following parameters: 4 shot EPI, b = 3000 s/mm2, 64 diffusion-encoding directions, 125×150 ?m2 in-plane resolution, 0.6 mm slice thickness, and 2h acquisition time. This protocol was used to image a cohort of adult C57BL/6 male mice, whereby the quality of the acquired data was assessed and diffusion tensor imaging (DTI) derived parameters were measured. High-quality images with high spatial and angular resolution, low distortion and low variability in DTI-derived parameters were obtained, indicating that EPI-DWI is feasible at 16.4T to study animal models of white matter (WM) diseases. PMID:26110770

  18. Next Generation Astronomical X-ray Optics: High Angular Resolution, Light Weight, and Low Production Cost

    NASA Technical Reports Server (NTRS)

    Zhang. W. W.; Biskach, M. P.; Blake, P. N.; Chan, K. W.; Gaskin, J. A.; Hong, M. L.; Jones, W. D.; Kolos, L. D.; Mazzarella, J. R.; McClelland, R. S.; O'Dell, S. L.; Saha, T. T.; Sharpe, M. V.

    2012-01-01

    X-ray astronomy depends on the availability of telescopes with high resolution and large photon collecting areas. Since x-ray observation can only be carried out above the atmosphere, these telescopes must be necessarily lightweight. Compounding the lightweight requirement is that an x-ray telescope consists of many nested concentric shells, which further require that x-ray mirrors must also be geometrically thin to achieve high packing efficiency. This double lightweight and geometrically thin requirement poses significant technical challenges in fabricating the mirrors and in integrating them into mirror assemblies. This paper reports on the approach, strategy and status of our x-ray optics development program whose objective is to meet these technical challenges at modest cost to enable future x-ray missions, including small Explorer missions in the near term, probe class missions in the medium term, and large flagship missions in the long term.

  19. High resolution angular sensor. [reducing ring laser gyro output quantization using phase locked loops

    NASA Technical Reports Server (NTRS)

    Gneses, M. I.; Berg, D. S.

    1981-01-01

    Specifications for the pointing stabilization system of the large space telescope were used in an investigation of the feasibility of reducing ring laser gyro output quantization to the sub-arc-second level by the use of phase locked loops and associated electronics. Systems analysis procedures are discussed and a multioscillator laser gyro model is presented along with data on the oscillator noise. It is shown that a second order closed loop can meet the measurement noise requirements when the loop gain and time constant of the loop filter are appropriately chosen. The preliminary electrical design is discussed from the standpoint of circuit tradeoff considerations. Analog, digital, and hybrid designs are given and their applicability to the high resolution sensor is examined. the electrical design choice of a system configuration is detailed. The design and operation of the various modules is considered and system block diagrams are included. Phase 1 and 2 test results using the multioscillator laser gyro are included.

  20. ATMOSPHERIC PHASE CORRECTION USING CARMA-PACS: HIGH ANGULAR RESOLUTION OBSERVATIONS OF THE FU ORIONIS STAR PP 13S*

    SciTech Connect

    Perez, Laura M.; Carpenter, John M.; Isella, Andrea [Department of Astronomy, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125 (United States); Lamb, James W.; Woody, David P.; Leitch, Erik M.; Muchovej, Stephen J.; Scott, Stephen L. [Owens Valley Radio Observatory, California Institute of Technology, Big Pine, CA 93513 (United States); Zauderer, B. Ashley; Bolatto, Alberto D.; Teuben, Peter J. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Bock, Douglas C. [Combined Array for Research in Millimeter-wave Astronomy, P.O. Box 968, Big Pine, CA 93513 (United States); Carlstrom, John; Culverhouse, Thomas L.; Marrone, Daniel P. [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave. Chicago, IL 60637 (United States); Joy, Marshall [Space Sciences-VP62, NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States); Kwon, Woojin [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Plambeck, Richard L.; Wright, Melvyn C. H. [Astronomy Department, University of California at Berkeley, Berkeley, CA 94720-3411 (United States)

    2010-11-20

    We present 0.''15 resolution observations of the 227 GHz continuum emission from the circumstellar disk around the FU Orionis star PP 13S*. The data were obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) Paired Antenna Calibration System (C-PACS), which measures and corrects the atmospheric delay fluctuations on the longest baselines of the array in order to improve the sensitivity and angular resolution of the observations. A description of the C-PACS technique and the data reduction procedures are presented. C-PACS was applied to CARMA observations of PP 13S*, which led to a factor of 1.6 increase in the observed peak flux of the source, a 36% reduction in the noise of the image, and a 52% decrease in the measured size of the source major axis. The calibrated complex visibilities were fitted with a theoretical disk model to constrain the disk surface density. The total disk mass from the best-fit model corresponds to 0.06 M{sub sun}, which is larger than the median mass of a disk around a classical T Tauri star. The disk is optically thick at a wavelength of 1.3 mm for orbital radii less than 48 AU. At larger radii, the inferred surface density of the PP 13S* disk is an order of magnitude lower than that needed to develop a gravitational instability.

  1. Pulsar timing arrays as imaging gravitational wave telescopes: Angular resolution and source (de)confusion

    NASA Astrophysics Data System (ADS)

    Boyle, Latham; Pen, Ue-Li

    2012-12-01

    Pulsar timing arrays (PTAs) will be sensitive to a finite number of gravitational wave (GW) “point” sources (e.g. supermassive black hole binaries). N quiet pulsars with accurately known distances dpulsar can characterize up to 2N/7 distant chirping sources per frequency bin ?fgw=1/T and localize them with “diffraction-limited” precision ???(1/SNR)(?gw/dpulsar). Even if the pulsar distances are poorly known, a PTA with F GW frequency bins can still characterize up to (2N/7)(1-(1)/(2F)) sources per bin, and the quasisingular pattern of timing residuals in the vicinity of a GW source still allows the source to be localized quasitopologically within roughly the smallest quadrilateral of quiet pulsars that encircles it on the sky, down to a limiting resolution ???(1/SNR)?gw/dpulsar. PTAs may be unconfused, even at the lowest GW frequencies: in that case, standard analysis techniques designed to detect a stochastic GW background would be incomplete and suboptimal, whereas matched filtering could provide more information and sensitivity.

  2. Pulsar timing arrays as imaging gravitational wave telescopes: angular resolution and source (de)confusion

    E-print Network

    Latham Boyle; Ue-Li Pen

    2013-03-12

    Pulsar timing arrays (PTAs) will be sensitive to a finite number of gravitational wave (GW) "point" sources (e.g. supermassive black hole binaries). N quiet pulsars with accurately known distances d_{pulsar} can characterize up to 2N/7 distant chirping sources per frequency bin \\Delta f_{gw}=1/T, and localize them with "diffraction limited" precision \\delta\\theta \\gtrsim (1/SNR)(\\lambda_{gw}/d_{pulsar}). Even if the pulsar distances are poorly known, a PTA with F frequency bins can still characterize up to (2N/7)[1-(1/2F)] sources per bin, and the quasi-singular pattern of timing residuals in the vicinity of a GW source still allows the source to be localized quasi-topologically within roughly the smallest quadrilateral of quiet pulsars that encircles it on the sky, down to a limiting resolution \\delta\\theta \\gtrsim (1/SNR) \\sqrt{\\lambda_{gw}/d_{pulsar}}. PTAs may be unconfused, even at the lowest frequencies, with matched filtering always appropriate.

  3. Parabolic approximation analytical model of super-resolution spot generation using nonlinear thin films: Theory and simulation

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Wei, Jingsong

    2014-04-01

    In this work, we present a theoretical analytical model called the parabolic approximation analytical model that considers the absorption coefficient and refractive index in a parabolic approximation profile along the radial direction. By using this model the generation of a super-resolution spot is analyzed in detail, and a numerical simulation subsequently conducted to verify the analytical model. This work is helpful in understanding the super-resolution effect of nonlinear thin films.

  4. The 2014 ALMA Long Baseline Campaign: First Results from High Angular Resolution Observations toward the HL Tau Region

    NASA Astrophysics Data System (ADS)

    Partnership, ALMA; Brogan, C. L.; Pérez, L. M.; Hunter, T. R.; Dent, W. R. F.; Hales, A. S.; Hills, R. E.; Corder, S.; Fomalont, E. B.; Vlahakis, C.; Asaki, Y.; Barkats, D.; Hirota, A.; Hodge, J. A.; Impellizzeri, C. M. V.; Kneissl, R.; Liuzzo, E.; Lucas, R.; Marcelino, N.; Matsushita, S.; Nakanishi, K.; Phillips, N.; Richards, A. M. S.; Toledo, I.; Aladro, R.; Broguiere, D.; Cortes, J. R.; Cortes, P. C.; Espada, D.; Galarza, F.; Garcia-Appadoo, D.; Guzman-Ramirez, L.; Humphreys, E. M.; Jung, T.; Kameno, S.; Laing, R. A.; Leon, S.; Marconi, G.; Mignano, A.; Nikolic, B.; Nyman, L.-A.; Radiszcz, M.; Remijan, A.; Rodón, J. A.; Sawada, T.; Takahashi, S.; Tilanus, R. P. J.; Vila Vilaro, B.; Watson, L. C.; Wiklind, T.; Akiyama, E.; Chapillon, E.; de Gregorio-Monsalvo, I.; Di Francesco, J.; Gueth, F.; Kawamura, A.; Lee, C.-F.; Nguyen Luong, Q.; Mangum, J.; Pietu, V.; Sanhueza, P.; Saigo, K.; Takakuwa, S.; Ubach, C.; van Kempen, T.; Wootten, A.; Castro-Carrizo, A.; Francke, H.; Gallardo, J.; Garcia, J.; Gonzalez, S.; Hill, T.; Kaminski, T.; Kurono, Y.; Liu, H.-Y.; Lopez, C.; Morales, F.; Plarre, K.; Schieven, G.; Testi, L.; Videla, L.; Villard, E.; Andreani, P.; Hibbard, J. E.; Tatematsu, K.

    2015-07-01

    We present Atacama Large Millimeter/submillimeter Array (ALMA) observations from the 2014 Long Baseline Campaign in dust continuum and spectral line emission from the HL Tau region. The continuum images at wavelengths of 2.9, 1.3, and 0.87 mm have unprecedented angular resolutions of 0.? 075 (10 AU) to 0.? 025 (3.5 AU), revealing an astonishing level of detail in the circumstellar disk surrounding the young solar analog HL Tau, with a pattern of bright and dark rings observed at all wavelengths. By fitting ellipses to the most distinct rings, we measure precise values for the disk inclination (46\\buildrel{\\circ}\\over{.} 72+/- 0\\buildrel{\\circ}\\over{.} 05) and position angle (+138\\buildrel{\\circ}\\over{.} 02+/- 0\\buildrel{\\circ}\\over{.} 07). We obtain a high-fidelity image of the 1.0 mm spectral index (?), which ranges from ? ? 2.0 in the optically thick central peak and two brightest rings, increasing to 2.3–3.0 in the dark rings. The dark rings are not devoid of emission, and we estimate a grain emissivity index of 0.8 for the innermost dark ring and lower for subsequent dark rings, consistent with some degree of grain growth and evolution. Additional clues that the rings arise from planet formation include an increase in their central offsets with radius and the presence of numerous orbital resonances. At a resolution of 35 AU, we resolve the molecular component of the disk in HCO+ (1-0) which exhibits a pattern over LSR velocities from 2–12 km s?1 consistent with Keplerian motion around a ?1.3 {M}? star, although complicated by absorption at low blueshifted velocities. We also serendipitously detect and resolve the nearby protostars XZ Tau (A/B) and LkH?358 at 2.9 mm. .

  5. Stability of dislocation structures in copper towards stress relaxation investigated by high angular resolution 3D x-ray diffraction.

    SciTech Connect

    Jakobsen, B.; Poulsen, H. F.; Lienert, U.; Bernier, J.; Gundlach, C.; Pantleon, W.; Riso National Lab.; Roskilde Univ.; LLNL; European Synchrotron Research Facility

    2008-01-01

    300 {micro}m thick tensile specimen of OFHC copper is subjected to a tensile loading sequence and deformed to a maximal strain of 3.11%. Using the novel three-dimensional X-ray diffraction method High angular resolution 3DXRD', the evolution of the microstructure within a deeply embedded grain is characterized in-situ by the behavior of individual subgrains. The loading sequence consists of three continuous deformation stages with strain rates of 1.1 x 10{sup -6} s{sup -1} and 3 x 10{sup -2} s{sup -1}, in each case followed by a period of extended stress relaxation at fixed motor positions, as well as an unloading step. In contrast to the deformation stages, during each stress relaxation stage, number, size and orientation of subgrains are found to be constant, while a minor amount of clean-up of the microstructure is observed as narrowing of the radial X-ray diffraction line profile. The associated decrease in the width of the strain distribution indicates homogenization of the elastic strains present in the deformation structure. During reloading, the subgrain structure seemingly starts to develop further when the entire dislocation structure is deforming plastically. Upon unloading of the sample, the average backward strain of the subgrains increases.

  6. Anomalous transmission of x rays scattered by phonons through germanium crystals: A high-angular-resolution study

    NASA Astrophysics Data System (ADS)

    Mori, Masahiro; Kashiwase, Yasuji; Kogiso, Motokazu; Ushida, Katsutoshi; Minoura, Masayuki; Ishikawa, Tetsuya; Sasaki, Satoshi

    1992-05-01

    An intensity-profile analysis has clarified the origin of a sharp diffraction line which has been observed in the 22¯0 thermal diffuse scattering from a thick perfect germanium crystal oriented in a direction offset by the Bragg angle in the transmission geometry. Experimental intensity measurements were performed with monochromatic synchrotron radiation, with use of a high-angular-resolution diffractometry system. The dependence of the intensity profiles on the crystal thickness and orientation was investigated in detail. A theoretical analysis of the intensity profiles was made on the basis of the dynamical diffraction theory including absorption and the kinematical theory of thermal diffuse scattering. We show that the diffraction peak is caused by dynamical Bragg reflection and anomalous transmission of x rays following thermal diffuse scattering in the absorbing perfect crystal and a satisfactory agreement is obtained between the experimental intensity peak profile and the calculated one. These results lend further support to our earlier interpretation [Y. Kashiwase et al., Phys. Rev. Lett. 62, 925 (1989)].

  7. Optimizing the angular resolution of the HEGRA telescope system to study the emission region of VHE gamma rays in the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Aharonian, F. A.; Akhperjanian, A. G.; Barrio, J. A.; Bernlöhr, K.; Bojahr, H.; Bolz, O.; Börst, H.; Contreras, J. L.; Cortina, J.; Denninghoff, V.; Fonseca, S.; Gonzalez, J. C.; Götting, N.; Heinzelmann, G.; Hermann, G.; Heusler, A.; Hofmann, W.; Horns, D.; Ibarra, A.; Iserlohe, C.; Jung, I.; Kankanyan, R.; Kestel, M.; Kettler, J.; Kohnle, A.; Konopelko, A.; Kornmeyer, H.; Kranich, D.; Krawczynski, H.; Lampeitl, H.; Lorenz, E.; Lucarelli, F.; Magnussen, N.; Mang, O.; Meyer, H.; Mirzoyan, R.; Moralejo, A.; Padilla, L.; Panter, M.; Plaga, R.; Plyasheshnikov, A.; Prahl, J.; Pühlhofer, G.; Rhode, W.; Röhring, A.; Rowell, G.; Sahakian, V.; Samorski, M.; Schilling, M.; Schröder, F.; Siems, M.; Stamm, W.; Tluczykont, M.; Völk, H. J.; Wiedner, C.; Wittek, W.

    2000-09-01

    The HEGRA system of imaging atmospheric Cherenkov telescopes provides for specially selected classes of events an angular resolution of better than 3'. By comparing the measured angular distribution of TeV gamma rays from the Crab Nebula with the distribution expected on the basis of Monte Carlo simulations, and with measurements of gamma rays from the point source Mrk 501, we conclude that the rms size of the VHE gamma-ray emission region in the Crab Nebula is less than 1.5'.

  8. Observations of the Sunyaev-Zel'dovich effect at high angular resolution towards the galaxy clusters A665, A2163 and CL0016+16

    E-print Network

    F. -X. Desert; A. Benoit; S. Gaertner; J. -P. Bernard; N. Coron; J. Delabrouille; P. de Marcillac; M. Giard; J. -M. Lamarre; B. Lefloch; J. -L. Puget; A. Sirbi

    1998-08-24

    We report on the first observation of the Sunyaev-Zel'dovich effect with the Diabolo experiment at the IRAM 30 metre telescope. A significant brightness decrement is detected in the direction of three clusters (Abell 665, Abell 2163 and CL0016+16). With a 30 arcsecond beam and 3 arcminute beamthrow, this is the highest angular resolution observation to date of the SZ effect.

  9. High angular resolution CO mapping of the high velocity gas associated with HL\\/XZ Tau and V 645 Cygni (GL 2789)

    Microsoft Academic Search

    J. M. Torrelles; G. Anglada; L. F. Rodriguez; L. F. Canto; J. F. Barral

    1987-01-01

    The authors have mapped the CO outflows associated with HL\\/XZ Tau and V645 Cygni with an angular resolution of 30arcsec. The blueshifted CO component associated with HL\\/XZ Tau appears to be located closer to XZ Tau than to HL Tau. This result together with theoretical considerations make doubtful the correctness of the previous indentification of HL Tau as the source

  10. Adaptive lobster-eye hard x-ray telescope with high-angular resolution and wide field of view

    NASA Astrophysics Data System (ADS)

    Grubsky, Victor; Gertsenshteyn, Michael; Shoemaker, Keith; Jannson, Tomasz

    2007-09-01

    High-resolution, wide-field-of-view hard X-ray telescopes are essential for detecting and studying cosmic sources in the 10-100 keV photon energy band, which are typically inaccessible to conventional Wolter I X-ray telescopes. To focus such high-energy photons, we developed special Lobster-Eye optics consisting of multiple reflective channels with square cross sections, which are formed by intersecting two sets of semiconductor-grade gold-coated flat silicon elements. Reflective channels with square cross sections The presented hard X-ray Lobster-Eye telescope lens designed for the 10-80 keV energy band consists of approximately 100 channels in both the horizontal and the vertical directions, with the angle between the adjacent plates being less than 1'. An array of such lenses, in which the orientation of each lens is independently controlled, can be used as an adaptive X-ray focusing device capable of changing its imaging properties depending on the user-selected mode. In the wide-angle operation, the individual lenses are aligned toward a common center to form a lobster-eye lens with a large (~2°) field of view, which would be suitable for monitoring stellar or galactic X-ray bursts. For observing a specific event, the telescope can be switched to the high-sensitivity mode by aligning the axes of the individual lenses in parallel so that they are all pointing to the region of interest, effectively adding up the effective areas of individual lenses (up to ~1600 cm2 at 40 keV). In the paper we will discuss the system performance simulations and the experimental results using initial prototype Lobster-Eye lenses.

  11. Approximate Approximate

    E-print Network

    Har-Peled, Sariel

    , slow, and not robust nZ1,000,000 n 2 =10 12 O n 2 #12; Approximation Algorithms: Approximation the Polytope A Features of the polytope partition sphere into regions A Voronoi Diagram induced by features

  12. IMPLICATIONS OF A HIGH ANGULAR RESOLUTION IMAGE OF THE SUNYAEV-ZEL'DOVICH EFFECT IN RXJ1347-1145

    SciTech Connect

    Mason, B. S.; Cotton, W. D. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Dicker, S. R.; Korngut, P. M.; Devlin, M. J.; Aguirre, J. E. [University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Koch, P. M.; Molnar, S. M. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Sievers, J. [The Canadian Institute of Theoretical Astrophysics, 60 St. George Street, Toronto, Ontario M5S 3H8 (Canada); Benford, D.; Staguhn, J. G.; Moseley, H. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Irwin, K. D. [National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80303 (United States); Ade, P., E-mail: bmason@nrao.ed [School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff CF24 3AA (United Kingdom)

    2010-06-10

    The most X-ray luminous cluster known, RXJ1347-1145 (z = 0.45), has been the object of extensive study across the electromagnetic spectrum. We have imaged the Sunyaev-Zel'dovich effect (SZE) at 90 GHz ({lambda} = 3.3 mm) in RXJ1347-1145 at 10'' resolution with the 64 pixel MUSTANG bolometer array on the Green Bank Telescope, confirming a previously reported strong, localized enhancement of the SZE 20'' to the southeast of the center of X-ray emission. This enhancement of the SZE has been interpreted as shock-heated (>20 keV) gas caused by an ongoing major (low mass ratio) merger event. Our data support this interpretation. We also detect a pronounced asymmetry in the projected cluster pressure profile, with the pressure just east of the cluster core {approx}1.6x higher than just to the west. This is the highest resolution image of the SZE made to date.

  13. A new UV and VUV beamline for angular resolved photoemission with high resolution and at low energy

    NASA Astrophysics Data System (ADS)

    Janowitz, Christoph; Zandt, Thorsten; Dudy, Lenart; Manzke, Recardo; Reichardt, Gerd

    2012-11-01

    A new 5-m normal-incidence monochromator at the third generation synchrotron source BESSY II of the Helmholz-Zentrum Berlin (HZB) has been constructed with the emphasis on angle-resolved photoelectron spectroscopy with high-resolution and at low energy utilizing photons from 5 eV to 40 eV. Optical design and preliminary performance results of the beamline and the photoemission endstation are presented and match the design goals.

  14. Initial time singularities in nonequilibrium evolution of condensates and their resolution in the linearized approximation

    NASA Astrophysics Data System (ADS)

    Baacke, J.; Boyanovsky, D.; de Vega, H. J.

    2001-02-01

    The real time nonequilibrium evolution of condensates in field theory requires an initial value problem specifying an initial quantum state or density matrix. Arbitrary specifications of the initial quantum state (pure or mixed) results in initial time singularities. These initial time singularities are of a different nature and independent of the ultraviolet divergences which are removed by the usual renormalization counterterms. The removal of the initial time singularities requires a specific choice of initial states. We study the initial time singularities in the linearized equation of motion for the scalar condensate in a renormalizable Yukawa theory in 3+1 dimensions. In this renormalizable theory the initial time singularities are enhanced. We present a consistent method for removing these initial time singularities by specifying initial states where the distribution of high energy quanta is determined by the initial conditions and the interaction effects. This is done through a Bogoliubov transformation which is consistently obtained in a perturbative expansion. The usual renormalization counterterms and the proper choice of the Bogoliubov coefficients lead to a singularity free evolution equation. We establish the relationship between the evolution equations in the linearized approximation and linear response theory. It is found that only a very specific form of the external source for linear response leads to a real time evolution equation which is singularity free. We focus on the evolution of spatially inhomogeneous scalar condensates by implementing the initial state preparation via a Bogoliubov transformation up to one loop. As a concrete application, the evolution equation for an inhomogeneous condensate is solved analytically and the results are carefully analyzed. Symmetry breaking by initial quantum states is discussed.

  15. ANGULAR MOMENTUM L Angular Momentum

    E-print Network

    ANGULAR MOMENTUM L #12;#12;#12;#12;#12;#12;p-6' Angular Momentum Case: A few particles Example: This example emphasizes the fact that the value of the angular momentum of a system of particles depends just for reference.). v v v 1 2 3 Calculate the vector angular momentum of the three-particle system

  16. High mass resolution, high angular acceptance time-of-flight mass spectroscopy for planetary missions under the Planetary Instrument Definition and Development Program (PIDDP)

    NASA Technical Reports Server (NTRS)

    Young, David T.

    1991-01-01

    This final report covers three years and several phases of work in which instrumentation for the Planetary Instrument Definition and Development Program (PIDDP) were successfully developed. There were two main thrusts to this research: (1) to develop and test methods for electrostatically scanning detector field-of-views, and (2) to improve the mass resolution of plasma mass spectrometers to M/delta M approximately 25, their field-of-view (FOV) to 360 degrees, and their E-range to cover approximately 1 eV to 50 keV. Prototypes of two different approaches to electrostatic scanning were built and tested. The Isochronous time-of-flight (TOF) and the linear electric field 3D TOF devices were examined.

  17. The Evolution of Planetary Systems: Ultra-High Angular Resolution and Contrast Imaging and Spectral Imaging with VLST and SI

    NASA Astrophysics Data System (ADS)

    Grady, C. A.; Woodgate, Bruce

    2004-05-01

    Protoplanetary disks are where planets form, migrate to their final orbits, and where the pre-biotic materials that can ultimately produce life-bearing worlds are assembled or produced. We need to understand them, how they interact with their central stars, and their evolution both to reconstruct the Solar System's history, and to account for the observed diversity of exo-planetary systems. An increasing body of evidence suggests that for 0.7-2.0 solar mass stars central clearing of the disk is not linked to the evolution of the star, but may be tied to formation of planets within the disk. The earliest manifestation of the presence of such bodies is likely to be changes in the mass accretion rate onto the star, the mass loss geometry from the star, and the development of dynamically sculpted cavities in the inner disk. While HST can detect the presence of 10 AU-scale cavities at d=100 pc, such as the one around HD 100546, mapping the interior structure of the cavity, directly detecting gas giants or terrestrial planets resident in the cavity, mapping the portion of the disk where chemistry occurs, and probing the geometry of the accretion flow and the stellar wind all require higher resolution and in some cases, contrast, than HST can provide. We discuss the potential for probing the planetary region of young circumstellar disks with a 10-30m UV/Optical telescope such as VLST equipped with a coronagraph and integral field spectrometer and the region from the dust sublimation radius in to the inner edge of the disk with a 20-500 m UV/Optical interferometer such as Stellar Imager.

  18. Application of second-order Møller-Plesset perturbation theory with resolution-of-identity approximation to periodic systems

    NASA Astrophysics Data System (ADS)

    Katouda, Michio; Nagase, Shigeru

    2010-11-01

    Efficient periodic boundary condition (PBC) calculations by the second-order Møller-Plesset perturbation (MP2) method based on crystal orbital formalism are developed by introducing the resolution-of-identity (RI) approximation of four-center two-electron repulsion integrals (ERIs). The formulation and implementation of the PBC RI-MP2 method are presented. In this method, the mixed auxiliary basis functions of the combination of Poisson and Gaussian type functions are used to circumvent the slow convergence of the lattice sum of the long-range ERIs. Test calculations of one-dimensional periodic trans-polyacetylene show that the PBC RI-MP2 method greatly reduces the computational times as well as memory and disk sizes, without the loss of accuracy, compared to the conventional PBC MP2 method.

  19. Application of second-order Møller-Plesset perturbation theory with resolution-of-identity approximation to periodic systems.

    PubMed

    Katouda, Michio; Nagase, Shigeru

    2010-11-14

    Efficient periodic boundary condition (PBC) calculations by the second-order Møller-Plesset perturbation (MP2) method based on crystal orbital formalism are developed by introducing the resolution-of-identity (RI) approximation of four-center two-electron repulsion integrals (ERIs). The formulation and implementation of the PBC RI-MP2 method are presented. In this method, the mixed auxiliary basis functions of the combination of Poisson and Gaussian type functions are used to circumvent the slow convergence of the lattice sum of the long-range ERIs. Test calculations of one-dimensional periodic trans-polyacetylene show that the PBC RI-MP2 method greatly reduces the computational times as well as memory and disk sizes, without the loss of accuracy, compared to the conventional PBC MP2 method. PMID:21073209

  20. A high angular resolution survey of massive stars in Cygnus OB2: Results from the Hubble space telescope fine guidance sensors

    SciTech Connect

    Caballero-Nieves, S. M.; Gies, D. R.; Jao, W.-C., E-mail: s.caballero@shef.ac.uk, E-mail: gies@chara.gsu.edu, E-mail: jao@chara.gsu.edu [Center for High Angular Resolution Astronomy, Department of Physics and Astronomy, Georgia State University, P.O. Box 4106, Atlanta, GA 30302-4106 (United States); and others

    2014-02-01

    We present results of a high angular resolution survey of massive OB stars in the Cygnus OB2 association that we conducted with the fine guidance sensor 1R (FGS1r) on the Hubble Space Telescope. FGS1r is able to resolve binary systems with a magnitude difference ?V < 4 down to separations as small as 0.''01. The sample includes 58 of the brighter members of Cyg OB2, one of the closest examples of an environment containing a large number of very young and massive stars. We resolved binary companions for 12 targets and confirmed the triple nature of one other target, and we offer evidence of marginally resolved companions for two additional stars. We confirm the binary nature of 11 of these systems from complementary adaptive optics imaging observations. The overall binary frequency in our study is 22% to 26% corresponding to orbital periods ranging from 20 to 20,000 yr. When combined with the known short-period spectroscopic binaries, the results support the hypothesis that the binary fraction among massive stars is >60%. One of the new discoveries is a companion to the hypergiant star MT 304 = Cyg OB2-12, and future measurements of orbital motion should provide mass estimates for this very luminous star.

  1. High-resolution electron microscopy observation of a new crystalline approximant W' of Mg-Zn-Y icosahedral quasicrystal

    PubMed

    Luo; Hashimoto

    2000-10-01

    A new ordered structure W' with a lattice parameter (a = 2.05 nm) about three times as large as that of the fundamental face-centered cubic W phase (a = 0.6848 nm) has been found in the Mg-Zn-Y system by means of transmission electron microscopy. The W' and W phases have the cube-to-cube orientation relationship. Moreover, the strong electron diffraction spots of the W' phase showed pseudoicosahedral symmetry, implying that it is a crystalline approximant of the Mg-Zn-Y icosahedral quasicrystal. In the high-resolution electron microscopic images of the W' phase, Penrose tiles of pentagons and boats with an edge length of a(p) = 0.481 nm can be identified. A binary tile of crown subunit has also been deduced from such a tiling. Translation domains of the W' phase have also been observed and the translation vectors at the domain boundary are: a(p), tau x a(p) and (1 + tau) x a(p), respectively, where (1 + tau) x a(p) equals to the edge length a(r) of the big obtuse rhombus of the W' phase and tau = (1 + square root of 5)/2, is the golden ratio. PMID:10831292

  2. The complex dust formation zone of the AGB star IRC+10216 probed with CARMA 0.25 arcsec angular resolution molecular observations

    NASA Astrophysics Data System (ADS)

    Fonfría, J. P.; Fernández-López, M.; Agúndez, M.; Sánchez-Contreras, C.; Curiel, S.; Cernicharo, J.

    2014-12-01

    We present low spectral resolution molecular interferometric observations at 1.2 mm obtained with the Combined Array for Research in Millimetre-wave Astronomy (CARMA) towards the C-rich AGB star IRC+10216. We have mapped the emission of several lines of SiS, H13CN, SiO and SiC2 in the ground and first excited vibrational states with a high angular resolution of 0.25 arcsec. These observations have allowed us to partially resolve the emission of the envelope at distances from the star ?50 stellar radii (R?), where the stellar wind is mainly accelerated. The structure of the molecular emission has been modelled with a 3D radiation transfer code. The emission of line SiS (v = 0, J = 14-13) is best reproduced with a set of maser emitting arcs arranged between 5 and 20R?. The abundance of H13CN with respect to H2 decreases from 8 × 10-7 at 1-5R? to 3 × 10-7 at 20R?. The SiO observations are explained with an abundance ?2 × 10-8 in the shell-like region between 1 and 5R?. At this point, the SiO abundance sharply increases up to (2-3) × 10-7. The vibrational temperature of SiO increases by a factor of 2 due north-east between 20 and 50R?. SiC2 is formed at the stellar surface with an abundance of 8 × 10-7 decreasing down to 8 × 10-8 at 20R? probably due to depletion on to dust grains. Several asymmetries are found in the abundance distributions of H13CN, SiO and SiC2 which define three remarkable directions (north-east, south-southwest, and south-east) in the explored region of the envelope. There are some differences between the redshifted and blueshifted emissions of these molecules suggesting the existence of additional asymmetries in their abundance distributions along the line of sight.

  3. Scaleable resolution transformation with anti-aliasing by outlining with approximated B-spline curve and rerendering

    NASA Astrophysics Data System (ADS)

    Sakaue, Eiichi

    1999-12-01

    This paper presents a developed scaleable resolution transformation method with high image quality, real-time processing and small circuitry. The progress of networked multi-functional hard-copy products for printing images from various sources such as facsimile machines, PCs, scanners and digital cameras, which have various resolutions, has created an urgent need for scaleable resolution transformation with high image quality.

  4. High Angular Resolution Radio Observations of the HL\\/XZ Tau Region: Mapping the 50 AU Protoplanetary Disk Around HL Tau and Resolving XZ Tau S Into a 13 AU Binary

    Microsoft Academic Search

    Carlos Carrasco-González; Luis F. Rodríguez; Guillem Anglada; Salvador Curiel

    2009-01-01

    We present new 7 mm and archive 1.3 cm high angular resolution observations of the HL\\/XZ Tau region made with the Very Large Array. At 7 mm, the emission from HL Tau seems to arise in a clumpy disk with radius of the order of 25 AU. The 1.3 cm emission from XZ Tau shows the emission from a binary

  5. Minimum uncertainty measurements of angle and angular momentum

    E-print Network

    Z. Hradil; J. Rehacek; Z. Bouchal; R. Celechovsky; L. L. Sanchez-Soto

    2006-05-16

    The uncertainty relations for angle and angular momentum are revisited. We use the exponential of the angle instead of the angle itself and adopt dispersion as a natural measure of resolution. We find states that minimize the uncertainty product under the constraint of a given uncertainty in angle or in angular momentum. These states are described in terms of Mathieu wave functions and may be approximated by a von Mises distribution, which is the closest analogous of the Gaussian on the unit circle. We report experimental results using beam optics that confirm our predictions.

  6. Resolution of identity approach for the Kohn-Sham correlation energy within the exact-exchange random-phase approximation.

    PubMed

    Bleiziffer, Patrick; Hesselmann, Andreas; Görling, Andreas

    2012-04-01

    Two related methods to calculate the Kohn-Sham correlation energy within the framework of the adiabatic-connection fluctuation-dissipation theorem are presented. The required coupling-strength-dependent density-density response functions are calculated within exact-exchange time-dependent density-functional theory, i.e., within time-dependent density-functional response theory using the full frequency-dependent exchange kernel in addition to the Coulomb kernel. The resulting resolution-of-identity exact-exchange random-phase approximation (RI-EXXRPA) methods in contrast to previous EXXRPA methods employ an auxiliary basis set (RI basis set) to improve the computational efficiency, in particular, to reduce the formal scaling of the computational effort with respect to the system size N from N(6) to N(5). Moreover, the presented RI-EXXRPA methods, in contrast to previous ones, do not treat products of occupied times unoccupied orbitals as if they were linearly independent. Finally, terms neglected in previous EXXRPA methods can be included, which leads to a method designated RI-EXXRPA+, while the method without these extra terms is simply referred to as RI-EXXRPA. Both EXXRPA methods are shown to yield total energies, reaction energies of small molecules, and binding energies of noncovalently bonded dimers of a quality that is similar and in some cases even better than that obtained with quantum chemistry methods such as Mo?ller-Plesset perturbation theory of second order (MP2) or with the coupled cluster singles doubles method. In contrast to MP2 and to conventional density-functional methods, the presented RI-EXXRPA methods are able to treat static correlation. PMID:22482535

  7. Angular resolution measurements at SPring-8 of a hard x-ray optic for the New Hard X-ray Mission

    NASA Astrophysics Data System (ADS)

    Spiga, D.; Raimondi, L.; Furuzawa, A.; Basso, S.; Binda, R.; Borghi, G.; Cotroneo, V.; Grisoni, G.; Kunieda, H.; Marioni, F.; Matsumoto, H.; Mori, H.; Miyazawa, T.; Negri, B.; Orlandi, A.; Pareschi, G.; Salmaso, B.; Tagliaferri, G.; Uesugi, K.; Valsecchi, G.; Vernani, D.

    2011-09-01

    The realization of X-ray telescopes with imaging capabilities in the hard (> 10 keV) X-ray band requires the adoption of optics with shallow (< 0.25 deg) grazing angles to enhance the reflectivity of reflective coatings. On the other hand, to obtain large collecting area, large mirror diameters (< 350 mm) are necessary. This implies that mirrors with focal lengths >=10 m shall be produced and tested. Full-illumination tests of such mirrors are usually performed with onground X-ray facilities, aimed at measuring their effective area and the angular resolution; however, they in general suffer from effects of the finite distance of the X-ray source, e.g. a loss of effective area for double reflection. These effects increase with the focal length of the mirror under test; hence a "partial" full-illumination measurement might not be fully representative of the in-flight performances. Indeed, a pencil beam test can be adopted to overcome this shortcoming, because a sector at a time is exposed to the X-ray flux, and the compensation of the beam divergence is achieved by tilting the optic. In this work we present the result of a hard X-ray test campaign performed at the BL20B2 beamline of the SPring-8 synchrotron radiation facility, aimed at characterizing the Point Spread Function (PSF) of a multilayer-coated Wolter-I mirror shell manufactured by Nickel electroforming. The mirror shell is a demonstrator for the NHXM hard X-ray imaging telescope (0.3 - 80 keV), with a predicted HEW (Half Energy Width) close to 20 arcsec. We show some reconstructed PSFs at monochromatic X-ray energies of 15 to 63 keV, and compare them with the PSFs computed from post-campaign metrology data, self-consistently treating profile and roughness data by means of a method based on the Fresnel diffraction theory. The modeling matches the measured PSFs accurately.

  8. Enhanced angular current intensity from Schottky emitters.

    PubMed

    Fujita, S; Wells, T R C; Ushio, W; Sato, H; El-Gomati, M M

    2010-09-01

    Even though the Schottky emitter is a high-brightness source of choice for electron beam systems, its angular current intensity is substantially lower than that of thermionic cathodes, rendering the emitter impractical for applications that require high beam current. In this study, two strategies were attempted to enhance its angular intensity, and their experimental results are reported. The first scheme is to employ a higher extraction field for increasing the brightness. However, the tip shape transformation was found to induce undesirably elevated emission from the facet edges at high fields. The second scheme exploits the fact that the angular intensity is proportional to the square of the electron gun focal length [Fujita, S. & Shimoyama, H. (2005) Theory of cathode trajectory characterization by canonical mapping transformation. J. Electron Microsc. 54, 331-343], which can be increased by scaling-up the emitter tip radius. A high angular current intensity (J(Omega) approximately 1.5 mA sr(-1)) was obtained from a scaled-up emitter. Preliminary performance tests were conducted on an electron probe-forming column by substituting the new emitter for the original tungsten filament gun. The beam current up to a few microamperes was achieved with submicron spatial resolution. PMID:20701659

  9. Fluidic angular velocity sensor

    NASA Technical Reports Server (NTRS)

    Berdahl, C. M. (inventor)

    1986-01-01

    A fluidic sensor providing a differential pressure signal proportional to the angular velocity of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular velocity of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular velocity of the impeller.

  10. Plasmons with orbital angular momentum

    SciTech Connect

    Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Ali, S. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); National Centre for Physics, Shahdra Valley Road, Islamabad 44000 (Pakistan); Thide, B. [Swedish Institute of Space Physics, Angstroem Laboratory, P.O. Box 537, SE-751 21 Uppsala (Sweden)

    2009-11-15

    Electron plasma waves carrying orbital angular momentum are investigated in an unmagnetized collisionless plasma composed of inertial electrons and static ions. For this purpose, the usual plasmon dispersion relation is employed to derive an approximate paraxial equation. The latter is analyzed with a Gaussian beam solution. For a finite angular momentum associated with the plasmon, Laguerre-Gaussian (LG) solutions are employed for solving the electrostatic potential problem which gives approximate solution and is valid for plasmon beams in the paraxial approximation. The LG potential determines the electric field components and energy flux of plasmons with finite angular momentum. Numerical illustrations show that the radial and angular mode numbers strongly modify the profiles of the LG potential.

  11. Atmospheric Corrections Using MODTRAN for TOA and Surface BRDF Characteristics from High Resolution Spectroradiometric\\/Angular Measurements from a Helicopter Platform

    Microsoft Academic Search

    Yaping Zhou; Ken C. Rutledge; Thomas P. Charlock

    Abstract High-resolution spectral radiance measurements were taken bya spectral radiometer on board a helicopter over the US Oklahoma Southern Great Plain near the Atmospheric Radiation Measurements,(ARM) site during August 1998. The radiometer has a spectral rangefrom 350nm to 2500nm at 1 nm resolution. Themeasure ments covered several grass and cropland scene types at multiple solar zenith angles. Detailed atmospheric corrections

  12. HARPO: beam characterization of a TPC for gamma-ray polarimetry and high angular-resolution astronomy in the MeV-GeV range

    E-print Network

    Wang, Shaobo; Bruel, Philippe; Frotin, Mickael; Geerebaert, Yannick; Giebels, Berrie; Gros, Philippe; Horan, Deirdre; Louzir, Marc; Poilleux, Patrick; Semeniouk, Igor; Attié, David; Calvet, Denis; Colas, Paul; Delbart, Alain; Sizun, Patrick; Götz, Diego; Amano, Sho; Kotaka, Takuya; Hashimoto, Satoshi; Minamiyama, Yasuhito; Takemoto, Akinori; Yamaguchi, Masashi; Miyamoto, Shuji; Daté, Schin; Ohkuma, Haruo

    2015-01-01

    A time projection chamber (TPC) can be used to measure the polarization of gamma rays with excellent angular precision and sensitivity in the MeV-GeV energy range through the conversion of photons to e+e- pairs. The Hermetic ARgon POlarimeter (HARPO) prototype was built to demonstrate this concept. It was recently tested in the polarized photon beam at the NewSUBARU facility in Japan. We present this data-taking run, which demonstrated the excellent performance of the HARPO TPC.

  13. Distributed memory parallel implementation of energies and gradients for second-order Møller-Plesset perturbation theory with the resolution-of-the-identity approximation.

    PubMed

    Hättig, Christof; Hellweg, Arnim; Köhn, Andreas

    2006-03-14

    We present a parallel implementation of second-order Møller-Plesset perturbation theory with the resolution-of-the-identity approximation (RI-MP2). The implementation is based on a recent improved sequential implementation of RI-MP2 within the Turbomole program package and employs the message passing interface (MPI) standard for communication between distributed memory nodes. The parallel implementation extends the applicability of canonical MP2 to considerably larger systems. Examples are presented for full geometry optimizations with up to 60 atoms and 3300 basis functions and MP2 energy calculations with more than 200 atoms and 7000 basis functions. PMID:16633596

  14. Angular Measure

    NSDL National Science Digital Library

    Students will learn about the Transit of Venus through reading a NASA press release and viewing a NASA eClips video that describes several ways to observe transits. Then students will study angular measurement by learning about parallax and how astronomers use this geometric effect to determine the distance to Venus during a Transit of Venus. This activity is part of the Space Math multimedia modules that integrate NASA press releases, NASA archival video, and mathematics problems targeted at specific math standards commonly encountered in middle school textbooks. The modules cover specific math topics at multiple levels of difficulty with real-world data and use the 5E instructional sequence.

  15. The Karlqvist approximation revisited

    E-print Network

    Tannous, C

    2015-01-01

    The Karlqvist approximation signaling the historical beginning of magnetic recording head theory is reviewed and compared to various approaches progressing from Green, Fourier, Conformal mapping that obeys the Sommerfeld edge condition at angular points and leads to exact results.

  16. A hybrid scheme for the resolution-of-the-identity approximation in second-order Møller-Plesset linear-r(12) perturbation theory.

    PubMed

    Klopper, Wim

    2004-06-15

    In the framework of second-order Møller-Plesset linear-r(12) (MP2-R12) perturbation theory, a method is developed and implemented that uses an auxiliary basis set for the resolution-of-the-identity (RI) approximation for the three- and four-electron integrals. In contrast to previous work, the two-electron integrals that must be evaluated never involve more than one auxiliary basis function. The new method therefore scales linearly with the number of auxiliary basis functions and is much more efficient than the previous one, which scaled quadratically. A general formulation of MP2-R12 theory is presented for various ansatze, approximations, and orbitals (canonical or localized). The new method is assessed by computations of the valence-shell second-order Møller-Plesset correlation energy of a few small closed-shell systems. The preliminary calculations indicate that the difference between the new and previous methods is about one order of magnitude smaller than the errors that occur due to basis-set truncations and RI approximations and under the assumptions of generalized and extended Brillouin conditions. PMID:15268119

  17. High Angular Resolution Radio Observations of the HL/XZ Tau Region: Mapping the 50 AU Protoplanetary Disk around HL Tau and Resolving XZ Tau S into a 13 AU Binary

    E-print Network

    Carrasco-Gonzalez, Carlos; Anglada, Guillem; Curiel, Salvador

    2009-01-01

    We present new 7 mm and archive 1.3 cm high angular resolution observations of the HL/XZ Tau region made with the VLA. At 7 mm, the emission from HL Tau seems to be arising in a clumpy disk with radius of order 25 AU. The 1.3 cm emission from XZ Tau shows the emission from a binary system with 0"3 (42 AU) separation, known from previous optical/IR observations. However, at 7 mm, the southern radio component resolves into a binary with 0"09 (13 AU) separation, suggesting that XZ Tau is actually a triple star system. We suggest that the remarkable ejection of gas from the XZ Tau system observed with the HST may be related to a periastron passage of this newly discovered close binary system.

  18. High angular resolution N-band observation of the silicate carbon star IRAS08002-3803 with the VLTI/MIDI instrument

    E-print Network

    Keiichi Ohnaka; T. Driebe; K. -H. Hofmann; Ch. Leinert; S. Morel; F. Paresce; Th. Preibisch; A. Richichi; D. Schertl; M. Schoeller; L. B. F. M. Waters; G. Weigelt; M. Wittkowski

    2005-09-26

    We present the results of N-band spectro-interferometric observations of the silicate carbon star IRAS08002-3803 with the MID-infrared Interferometric instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO). The observations were carried out using two unit telescopes (UT2 and UT3) with projected baseline lengths ranging from 39 to 47 m. Our observations of IRAS08002-3803 have spatially resolved the dusty environment of a silicate carbon star for the first time and revealed an unexpected wavelength dependence of the angular size in the N band: the uniform-disk diameter is found to be constant and ~36 mas (72 Rstar) between 8 and 10 micron, while it steeply increases longward of 10 micron to reach ~53 mas (106 Rstar) at 13 micron. Model calculations with our Monte Carlo radiative transfer code show that neither spherical shell models nor axisymmetric disk models consisting of silicate grains alone can simultaneously explain the observed wavelength dependence of the visibility and the spectral energy distribution (SED). We propose that the circumstellar environment of IRAS08002-3803 may consist of two grain species coexisting in the disk: silicate and a second grain species, for which we consider amorphous carbon, large silicate grains, and metallic iron grains. Comparison of the observed visibilities and SED with our models shows that such disk models can fairly -- though not entirely satisfactorily -- reproduce the observed SED and N-band visibilities. Our MIDI observations and the radiative transfer calculations lend support to the picture where oxygen-rich material around IRAS08002-3803 is stored in a circumbinary disk surrounding the carbon-rich primary star and its putative low-luminosity companion.

  19. High Angular Resolution Observations of Episodic Dust Emission from Long Period Variable Stars Twenty Years of Observations with the Berkeley Infrared Spatial Interferometer

    NASA Technical Reports Server (NTRS)

    Danchi, William

    2010-01-01

    Over the past twenty years the U. C. Berkeley Infrared Spatial Interferometer has observed a number of Long Period Variable stars in the mid-infrared, obtaining information on the spatial distribution of dust around these stars with resolutions of the order of a few tens of milliarcseconds. The ISI is a heterodyne interferometer operating mostly at 11.15 microns, initially with two telescopes. In the last decade, it has been taking data regularly with three telescopes, thus obtaining visibility data on three baselines and also a closure phase. Over the course of the years, the ISI has been able to measure the physical properties of the dust shells surrounding these stars, in particular the inner radii of the dust shells, as well as the temperature and density distribution. For some stars, the ISI has also made precision measurements of their diameters in the mid-infrared. Closure phase measurements have revealed asymmetries in the dust distributions around many stars. Most surprisingly the ISI data has shown evidence for substantial changes in the amount of dust on time scales of 5-10 years, rather than being directly correlated with the stellar pulsation periods, which are of the order of one year. We discuss past results and new results from the ISI that highlight the dynamic environment around these stars.

  20. High Angular Resolution Measurement of Ion and Neutral Spectra as a Probe of the Magnetic Field Structure in DR21(OH)

    E-print Network

    Lai, S P; Langer, W D; Lai, Shih-Ping

    2003-01-01

    It has been suggested that under average interstellar field strengths the cyclotron interaction between ions and magnetic fields is strong enough to narrow the linewidth and suppress the line wings in the ion spectra. We present evidence for the cyclotron interaction effect at arcsec scale on the velocity dispersions in the spectra of ion/neutral molecular species in DR21(OH) observed with the OVRO-MMA. Using a spatial resolution $\\sim$ 3 times higher than previous CSO observations by Houde et al. (2002), we show that H$^{13}$CO$^+$ and H$^{13}$CN are coexistent at the scale of our observations (6\\arcsec). In the eastern parts of the DR21(OH) core where the dynamics is simple, the ion linewidths are indeed narrower than the neutral linewidths with an average ion-to-neutral linewidth ratio of 0.82$\\pm$0.04. We use our results, along with the existing Zeeman and dust/CO polarization data on small scales, to derive the 3-D magnetic field structure. We obtain a field strength of $0.44\\pm$0.12 mG with inclination ...

  1. High Angular Resolution Measurement of Ion and Neutral Spectra as a Probe of the Magnetic Field Structure in DR21(OH)

    E-print Network

    Shih-Ping Lai; T. Velusamy; W. D. Langer

    2003-09-04

    It has been suggested that under average interstellar field strengths the cyclotron interaction between ions and magnetic fields is strong enough to narrow the linewidth and suppress the line wings in the ion spectra. We present evidence for the cyclotron interaction effect at arcsec scale on the velocity dispersions in the spectra of ion/neutral molecular species in DR21(OH) observed with the OVRO-MMA. Using a spatial resolution $\\sim$ 3 times higher than previous CSO observations by Houde et al. (2002), we show that H$^{13}$CO$^+$ and H$^{13}$CN are coexistent at the scale of our observations (6\\arcsec). In the eastern parts of the DR21(OH) core where the dynamics is simple, the ion linewidths are indeed narrower than the neutral linewidths with an average ion-to-neutral linewidth ratio of 0.82$\\pm$0.04. We use our results, along with the existing Zeeman and dust/CO polarization data on small scales, to derive the 3-D magnetic field structure. We obtain a field strength of $0.44\\pm$0.12 mG with inclination of 36\\deg to the line of sight, directed toward the observer, and a position angle of $-$75\\deg in the plane of the sky. With the full magnetic field strength derived here, we are able to conclude that the MM1 core of DR21(OH) is magnetically supercritical; although turbulence provides the dominant support.

  2. High Angular Resolution Astronomy on a Shoestring

    NASA Astrophysics Data System (ADS)

    Haniff, Chris

    Introduction; Lessons From Single-Telescope Interferometry; Interferometry with Single Telescopes; Astronomical applications; Desiderata For a Second-Generation Array; Astronomical goals; COAST - Lessons From a Prototype Array; Design elements of COAST; Suggestions For a Next-Generation Array (NGA); Collectors; Transport; Path Equalization; Optics; Operation; Summary

  3. An Angular Open Mapping Theorem Matthias Kawski1

    E-print Network

    Kawski, Matthias

    An Angular Open Mapping Theorem Matthias Kawski1 Department of Mathematics, Arizona State University Tempe, Arizona 85287 We give an angular open mapping theorem applicable to local approximating controllability, as only they allow one to use local approximating cones to conclude that a trajectory lies

  4. Investigation of angular and axial smoothing of PET data

    SciTech Connect

    Daube-Witherspoon, M.E.; Carson, R.E. [National Institutes of Health, Bethesda, MD (United States)

    1996-12-31

    Radial filtering of emission and transmission data is routinely performed in PET during reconstruction in order to reduce image noise. Angular smoothing is not typically done, due to the introduction of a non-uniform resolution loss; axial filtering is also not usually performed on data acquired in 2D mode. The goal of this paper was to assess the effects of angular and axial smoothing on noise and resolution. Angular and axial smoothing was incorporated into the reconstruction process on the Scanditronix PC2048-15B brain PET scanner. In-plane spatial resolution and noise reduction were measured for different amounts of radial and angular smoothing. For radial positions away from the center of the scanner, noise reduction and degraded tangential resolution with no loss of radial resolution were seen. Near the center, no resolution loss was observed, but there was also no reduction in noise for angular filters up to a 7{degrees} FWHM. These results can be understood by considering the combined effects of smoothing projections across rows (angles) and then summing (backprojecting). Thus, angular smoothing is not optimal due to its anisotropic noise reduction and resolution degradation properties. However, uniform noise reduction comparable to that seen with radial filtering can be achieved with axial smoothing of transmission data. The axial results suggest that combined radial and axial transmission smoothing could lead to improved noise characteristics with more isotropic resolution degradation.

  5. Resolution in rotation measurements

    Microsoft Academic Search

    Stephen M. Barnett; Roberta Zambrini

    2006-01-01

    The limiting resolution in optical interferometry is set by the number of photons used, with the functional dependence determined by the state of light that is prepared. We consider the problem of measuring the rotation of a beam of light about an optical axis and show how the limiting resolution depends on the total number of quanta of orbital angular

  6. Ultrahigh-resolution soft x-ray tomography

    NASA Astrophysics Data System (ADS)

    Haddad, Waleed S.; Trebes, James E.; Goodman, Dennis M.; Lee, Heung-Rae; McNulty, Ian; Anderson, Erik H.; Zalensky, Andrei O.

    1995-09-01

    Ultra high resolution three-dimensional images of a microscopic test object were made with soft x rays using a scanning transmission x-ray microscope. The test object consisted of two different patterns of gold bars on silicon nitride windows that were separated by approximately 5 micrometer. A series of nine 2-D images of the object were recorded at angles between -5 to +55 degrees with respect to the beam axis. The projections were then combined tomographically to form a 3-D image by means of an algebraic reconstruction technique (ART) algorithm. A transverse resolution of approximately 1000 angstrom was observed. Artifacts in the reconstruction limited the overall depth resolution to approximately 6000 angstrom, however some features were clearly reconstructed with a depth resolution of approximately 1000 angstrom. A specially modified ART algorithm and a constrained conjugate gradient (CCG) code were also developed as improvements over the standard ART algorithm. Both of these methods made significant improvements in the overall depth resolution, bringing it down to approximately 1200 angstrom overall. Preliminary projection data sets were also recorded with both dry and re-hydrated human sperm cells over a similar angular range.

  7. Angular Acceleration without Torque?

    ERIC Educational Resources Information Center

    Kaufman, Richard D.

    2012-01-01

    Hardly. Just as Robert Johns qualitatively describes angular acceleration by an internal force in his article "Acceleration Without Force?" here we will extend the discussion to consider angular acceleration by an internal torque. As we will see, this internal torque is due to an internal force acting at a distance from an instantaneous center.

  8. CONVERVATION OF ANGULAR MOMENTUM A rotating bicycle wheel has angular

    E-print Network

    CONVERVATION OF ANGULAR MOMENTUM A rotating bicycle wheel has angular momentum, which is a property a larger angular momentum at a given speed. Angular momentum is characterized by both size and direction momentum. This means that any change in angular momentum within the system must be accompanied by an equal

  9. Uncertainty Relations for Angular Momentum

    E-print Network

    Lars Dammeier; Rene Schwonnek; Reinhard F. Werner

    2015-04-30

    In this work we study various notions of uncertainty for angular momentum in the spin-s representation of SU(2). We characterize the "uncertainty regions" given by all vectors, whose components are the variances of the three angular momentum components. A basic feature of this set is a lower bound for the sum of the three variances. We give a method for obtaining optimal lower bounds for uncertainty regions for general operator triples, and evaluate these for small s. Further lower bounds are derived by generalizing the technique by which Robertson obtained his state-dependent lower bound. These are optimal for large s, since they are saturated by states taken from the Holstein-Primakoff approximation. We show that, for all s, all variances are consistent with the so-called vector model, i.e., they can also be realized by a classical probability measure on a sphere of radius sqrt(s(s+1)). Entropic uncertainty relations can be discussed similarly, but are minimized by quite different states from the variance minimizing ones for small s. For large s the Maassen-Uffink bound becomes sharp, again being saturated by Holstein-Primakoff states. Measurement uncertainty, as recently discussed by Busch, Lahti and Werner for position and momentum, is introduced and a generalized observable (POVM) which minimizes the worst case measurement uncertainty of all angular momentum components is explicitly determined. Its outputs are angular momentum vectors whose absolute value r(s) depends only on s. The function r is determined explicitly, and r(s)/s approaches 1 from below.

  10. Fission fragment angular distributions

    SciTech Connect

    Bond, P.D.

    1985-01-01

    Many recent papers have found that calculations with the standard angular distribution formula for fission fragments from compound nuclei do not reproduce the strong anisotropies observed in the decay of high spin systems. They conclude that a noncompound nuclear process must exist for some partial waves and postulate an ad-hoc angular distribution for this process in order to reproduce the strong anisotropies. It is the purpose of this contribtion to demonstrate that much of the data are, in fact, consistent with compound nucleus formation and to emphasize that the standard model is not a generally valid way to calculate fission fragment angular distributions from a compound nucleus.

  11. Fourier relationship between angular position and optical orbital angular momentum

    E-print Network

    Eric Yao; Sonja Franke-Arnold; Johannes Courtial; Stephen Barnett; Miles Padgett

    2006-06-15

    We demonstrate the Fourier relationship between angular position and angular momentum for a light mode. In particular we measure the distribution of orbital angular momentum states of light that has passed through an aperture and verify that the orbital angular momentum distribution is given by the complex Fourier-transform of the aperture function. We use spatial light modulators, configured as diffractive optical components, to define the initial orbital angular momentum state of the beam, set the defining aperture, and measure the angular momentum spread of the resulting beam. These measurements clearly confirm the Fourier relationship between angular momentum and angular position, even at light intensities corresponding to the single photon level.

  12. Absolute measurement of hyperspectral and angular reflection.

    PubMed

    Hwang, Jisoo

    2014-09-20

    A new instrument for absolute measurement of hyperspectral and angular reflection is presented. The instrument determines absolute values of angular reflection quantities in a wavelength range from 380 to 780 nm with a 3 nm spectral resolution by using a white source and a CCD-based spectroradiometer. Through uncertainty evaluation, the measurement uncertainty is determined as 1.4%-2.9% (k=2) for white diffuse material of Spectralon. The gonioreflectometric determination and an integrating-sphere-based reflection measurement traceable to KRISS spectral reflectance scale are compared by determining hemispherical reflectance, which results in agreement in their uncertainties. PMID:25322100

  13. Resolution in Electromagnetic Prospecting

    NASA Astrophysics Data System (ADS)

    Aldridge, D. F.; Bartel, L. C.; Knox, H. A.; Schramm, K. A.

    2014-12-01

    Low-frequency electromagnetic (EM) signals are commonly used in geophysical exploration of the shallow subsurface. Sensitivity to conductivity implies they are particularly useful for inferring fluid content of porous media. However, low-frequency EM wavefields are diffusive, and have significantly larger wavelengths compared to seismic signals of equal frequency. The wavelength of a 30 Hz sinusoid propagating with seismic velocity 3000 m/s is 100 m, whereas an analogous EM signal diffusing through a conductive body of 0.1 S/m (clayey shale) has wavelength 1825 m. The larger wavelength has implications for resolution of the EM prospecting method. We are investigating resolving power of the EM method via theoretical and numerical experiments. Normal incidence plane wave reflection/transmission by a thin geologic bed is amenable to analytic solution. Responses are calculated for beds that are conductive or resistive relative to the host rock. Preliminary results indicate the classic seismic resolution/detection limit of bed thickness ~1/8 wavelength is not achieved. EM responses for point or line current sources recorded by general acquisition geometries are calculated with a 3D finite-difference algorithm. These exhibit greater variability which may allow inference of bed thickness. We also examine composite responses of two point scatterers with separation when illuminated by an incident EM field. This is analogous to the Rayleigh resolution problem of estimating angular separation between two light sources. The First Born Approximation implies that perturbations in permittivity, permeability, and conductivity have different scattering patterns, which may be indicators of EM medium properties. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  14. Optical Broadband Angular Selectivity

    E-print Network

    Shen, Yichen

    Light selection based purely on the angle of propagation is a long-standing scientific challenge. In angularly selective systems, however, the transmission of light usually also depends on the light frequency. We tailored ...

  15. Metamaterial broadband angular selectivity

    E-print Network

    Shen, Yichen

    We demonstrate how broadband angular selectivity can be achieved with stacks of one-dimensionally periodic photonic crystals, each consisting of alternating isotropic layers and effective anisotropic layers, where each ...

  16. Product angular distributions in dissociative recombination.

    PubMed

    Guberman, Steven L

    2004-05-22

    The dependence of the dissociative recombination cross section upon the angle between the incoming electron beam and the ion internuclear axis is determined for diatomic molecules. Product angular distributions are derived for the component partial waves of the Coulomb wave function. In agreement with earlier results for dissociative attachment, it is shown that in the slow rotation approximation, if electron capture is dominated by a single partial wave, the product angular distribution is given by the square of the absolute value of the partial wave spherical harmonic describing the incoming electron. PMID:15267962

  17. Creating High-Harmonic Beams with Controlled Orbital Angular Momentum

    NASA Astrophysics Data System (ADS)

    Gariepy, Genevieve; Leach, Jonathan; Kim, Kyung Taec; Hammond, T. J.; Frumker, E.; Boyd, Robert W.; Corkum, P. B.

    2014-10-01

    A beam with an angular-dependant phase ? =?? about the beam axis carries an orbital angular momentum of ?? per photon. Such beams are exploited to provide superresolution in microscopy. Creating extreme ultraviolet or soft-x-ray beams with controllable orbital angular momentum is a critical step towards extending superresolution to much higher spatial resolution. We show that orbital angular momentum is conserved during high-harmonic generation. Experimentally, we use a fundamental beam with |?|=1 and interferometrically determine that the harmonics each have orbital angular momentum equal to their harmonic number. Theoretically, we show how any small value of orbital angular momentum can be coupled to any harmonic in a controlled manner. Our results open a route to microscopy on the molecular, or even submolecular, scale.

  18. Angular Momentum Operator Identities G I. Orbital Angular Momentum

    E-print Network

    Simons, Jack

    Angular Momentum Operator Identities G I. Orbital Angular Momentum A particle moving with momentum p at a position r relative to some coordinate origin has so-called orbital angular momentum equal to L = r x p . The three components of this angular momentum vector in a cartesian coordinate system

  19. SPECT electronic collimation resolution enhancement using chi-square minimization.

    PubMed

    Durkee, J W; Antich, P P; Tsyganov, E N; Constantinescu, A; Fernando, J L; Kulkarni, P V; Smith, B J; Arbique, G M; Lewis, M A; Nguyen, T; Raheja, A; Thambi, G; Parkey, R W

    1998-10-01

    An electronic collimation technique is developed which utilizes the chi-square goodness-of-fit measure to filter scattered gammas incident upon a medical imaging detector. In this data mining technique, Compton kinematic expressions are used as the chi-square fitting templates for measured energy-deposition data involving multiple-interaction scatter sequences. Fit optimization is conducted using the Davidon variable metric minimization algorithm to simultaneously determine the best-fit gamma scatter angles and their associated uncertainties, with the uncertainty associated with the first scatter angle corresponding to the angular resolution precision for the source. The methodology requires no knowledge of materials and geometry. This pattern recognition application enhances the ability to select those gammas that will provide the best resolution for input to reconstruction software. Illustrative computational results are presented for a conceptual truncated-ellipsoid polystyrene position-sensitive fibre head-detector Monte Carlo model using a triple Compton scatter gamma sequence assessment for a 99mTc point source. A filtration rate of 94.3% is obtained, resulting in an estimated sensitivity approximately three orders of magnitude greater than a high-resolution mechanically collimated device. The technique improves the nominal single-scatter angular resolution by up to approximately 24 per cent as compared with the conventional analytic electronic collimation measure. PMID:9814529

  20. The Angular Momentum Dichotomy

    NASA Astrophysics Data System (ADS)

    Teklu, Adelheid; Remus, Rhea-Silvia; Dolag, Klaus; Burkert, Andreas

    2015-02-01

    In the context of the formation of spiral galaxies the evolution and distribution of the angular momentum of dark matter halos have been discussed for more than 20 years, especially the idea that the specific angular momentum of the halo can be estimated from the specific angular momentum of its disk (e.g. Fall & Efstathiou (1980), Fall (1983) and Mo et al. (1998)). We use a new set of hydrodynamic cosmological simulations called Magneticum Pathfinder which allow us to split the galaxies into spheroidal and disk galaxies via the circularity parameter ?, as commonly used (e.g. Scannapieco et al. (2008)). Here, we focus on the dimensionless spin parameter ? = J |E|1/2 / (G M5/2) (Peebles 1969, 1971), which is a measure of the rotation of the total halo and can be fitted by a lognormal distribution, e.g. Mo et al. (1998). The spin parameter allows one to compare the relative angular momentum of halos across different masses and different times. Fig. 1 reveals a dichotomy in the distribution of ? at all redshifts when the galaxies are split into spheroids (dashed) and disk galaxies (dash-dotted). The disk galaxies preferentially live in halos with slightly larger spin parameter compared to spheroidal galaxies. Thus, we see that the ? of the whole halo reflects the morphology of its central galaxy. For more details and a larger study of the angular momentum properties of disk and spheroidal galaxies, see Teklu et al. (in prep.).

  1. Angular correlations and high energy evolution

    SciTech Connect

    Kovner, Alex [Physics Department, University of Connecticut, 2152 Hillside Road, Storrs, Connecticut 06269-3046 (United States); Lublinsky, Michael [Physics Department, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel); Physics Department, University of Connecticut, 2152 Hillside Road, Storrs, Connecticut 06269-3046 (United States)

    2011-11-01

    We address the question of to what extent JIMWLK evolution is capable of taking into account angular correlations in a high energy hadronic wave function. Our conclusion is that angular (and indeed other) correlations in the wave function cannot be reliably calculated without taking into account Pomeron loops in the evolution. As an example we study numerically the energy evolution of angular correlations between dipole scattering amplitudes in the framework of the large N{sub c} approximation to JIMWLK evolution (the 'projectile dipole model'). Target correlations are introduced via averaging over an (isotropic) ensemble of anisotropic initial conditions. We find that correlations disappear very quickly with rapidity even inside the saturation radius. This is in accordance with our physical picture of JIMWLK evolution. The actual correlations inside the saturation radius in the target QCD wave function, on the other hand, should remain sizable at any rapidity.

  2. Resolution in rotation measurements

    E-print Network

    Barnett, S M; Barnett, Stephen M; Zambrini, Roberta

    2005-01-01

    The limiting resolution in optical interferometry is set by the number of photons used, with the functional dependence determined by the state of light that is prepared. We consider the problem of measuring the rotation of a beam of light about an optical axis and show how the limiting resolution depends on the total number of quanta of orbital angular momentum carried by the light beam.

  3. Resolution in rotation measurements

    E-print Network

    Stephen M Barnett; Roberta Zambrini

    2005-03-30

    The limiting resolution in optical interferometry is set by the number of photons used, with the functional dependence determined by the state of light that is prepared. We consider the problem of measuring the rotation of a beam of light about an optical axis and show how the limiting resolution depends on the total number of quanta of orbital angular momentum carried by the light beam.

  4. Angular shear plate

    DOEpatents

    Ruda, Mitchell C. (Tucson, AZ); Greynolds, Alan W. (Tucson, AZ); Stuhlinger, Tilman W. (Tucson, AZ)

    2009-07-14

    One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.

  5. Unveiling Angular Momentum

    NASA Astrophysics Data System (ADS)

    Robinson, Stephen

    2015-03-01

    Angular momentum is a notoriously difficult concept to grasp. Visualization often requires three-dimensional pictures of vectors pointing in seemingly arbitrary directions. A simple student-run laboratory experiment coupled with intuitive explanations by an instructor can clear up some of the inherent ambiguity of rotational motion. Specifically, the precessional period of a suspended spinning bicycle wheel can be related to the spinning frequency through a simple algebraic expression. An explanation of this precession apart from the concept of angular momentum will be given.

  6. Semiclassical complex angular momentum theory and Padé reconstruction for resonances, rainbows, and reaction thresholds

    NASA Astrophysics Data System (ADS)

    Sokolovski, D.; Msezane, A. Z.

    2004-09-01

    A semiclassical complex angular momentum theory, used to analyze atom-diatom reactive angular distributions, is applied to several well-known potential (one-particle) problems. Examples include resonance scattering, rainbow scattering, and the Eckart threshold model. Padé reconstruction of the corresponding matrix elements from the values at physical (integral) angular momenta and properties of the Padé approximants are discussed in detail.

  7. Semiclassical complex angular momentum theory and Pade reconstruction for resonances, rainbows, and reaction thresholds

    SciTech Connect

    Sokolovski, D. [School of Mathematics and Physics, Queen's University of Belfast, Belfast, BT7 1NN (United Kingdom); Msezane, A.Z. [Department of Physics and Center for Theoretical Studies of Physical Systems, Clark Atlanta University, Atlanta, Georgia 30314 (United States)

    2004-09-01

    A semiclassical complex angular momentum theory, used to analyze atom-diatom reactive angular distributions, is applied to several well-known potential (one-particle) problems. Examples include resonance scattering, rainbow scattering, and the Eckart threshold model. Pade reconstruction of the corresponding matrix elements from the values at physical (integral) angular momenta and properties of the Pade approximants are discussed in detail.

  8. On separating the information of slow-mode angular motion of projectile

    Microsoft Academic Search

    Yuanqin Wang; Ruoyu Zhang; Jing Sun

    2010-01-01

    The information on angular motion of projectile can be expressed by the Amplitude Modulation (AM) index of radar echo. In order to separate the information of slow-mode angular motion, a method based on Empirical Mode Decomposition (EMD) is proposed. Three issues are discussed in this article. First, the angular motion of projectile is approximated as a fast-mode circle superposing over

  9. High-resolution electron microscopy analysis of structural defects in a (2/1, 5/3)-type approximant of a decagonal quasicrystal of an Al-Pd-Mn alloy

    SciTech Connect

    Yu, D.P.; Ren, G.; Zhang, Z. [Chinese Academy of Sciences, Beijing (China). Beijing Lab. of Electron Microscopy

    1996-10-01

    Structural defects were analyzed by means of high-resolution electron microscopy (HREM) in a crystalline (2/1, 5/3)-type Fibonacci approximant of an Al-Pd-Mn alloy system. A kind of stacking fault is observed with a projected displacement vector R parallel to the [{minus}3 0 29] direction; its amplitude {vert_bar}R{vert_bar} = 2a sin 18 deg = 1.19 nm, and its habit plane lies in the (1 0 1) plane. Two kinds of domain boundaries have been found and the domains are related by a 180 deg rotation around the c-axis plus a displacement along the [3 0 {minus}29] or the [{minus}3 0 {minus}29] direction in a plane perpendicular to the b-axis. The domain boundary planes are the {l_brace}1 0 1{r_brace} planes.

  10. A Universal Angular Momentum Profile for Galactic Halos

    Microsoft Academic Search

    J. S. Bullock; Avishai Dekel; T. S. Kolatt; Andrey V. Kravtsov; Anatoly A. Klypin; Cristiano Porciani; J. R. Primack

    2001-01-01

    We study the angular momentum profiles of a statistical sample of halos drawn from a high-resolution N-body simulation of the LambdaCDM cosmology. We find that the cumulative mass distribution of specific angular momentum j in a halo of mass Mv is well fitted by a universal function, M(

  11. Minimum uncertainty states of angular momentum and angular position

    Microsoft Academic Search

    R. Zambrini; D. T. Pegg; S. M. Barnott; S. Franke-Arnold; M. Padgett

    2005-01-01

    In this paper, the much less known uncertainty relation for angular position and momentum to find the system at the edge of the phase interval is considered. States that minimize the uncertainty product with a constraint given either by the angular variance or by the angular momentum variance is examined.

  12. Angular momentum of the atmosphere Variations of atmospheric relative angular

    E-print Network

    O'Gorman, Paul

    Angular momentum of the atmosphere #12;Variations of atmospheric relative angular momentum OCW Schematic of dynamic angular momentum transports and surface torques #12;NCEP reanalysis imbalance -30 0 30 60 0.2 0.8 JJA DJF #12;Northward flux of momentum (m2s-2) Peixoto and Oort, Fig 11

  13. Angular Momentum Diagrams

    NASA Astrophysics Data System (ADS)

    Wormer, Paul E. S.; Paldus, Josef

    Starting from the simplest possible building blocks--a ket, a bra, a time-reversed ket, and a time-reversed bra--a diagrammatic formalism is developed for angular momentum coupling problems. The formalism comprises Clebsch-Gordan coefficients as well as 3jm-symbols. The idea of constructing invariants (internal lines) by contracting contragredient pairs of quantities is emphasized throughout. The Clebsch-Gordan series, and its extension to the coupling of more than two angular momenta, is introduced algebraically and diagrammatically. Recoupling between bases obtained in different coupling schemes is introduced and the connection between recoupling coefficients and irreducible 3nj-symbols is derived diagrammatically. The well-known diagrammatic rules due to Jucys and co-workers are derived by group theoretical means and simple rules for their practical exploitation are presented.

  14. Mangle: Angular Mask Software

    NASA Astrophysics Data System (ADS)

    Swanson, Molly; Tegmark, Max; Hamilton, Andrew; Hill, Colin

    2012-02-01

    Mangle is a suite of software designed to deal accurately and efficiently with complex angular masks, such as occur typically in galaxy surveys. Mangle performs the following tasks: converts masks between many handy formats (including HEALPix),rapidly finds the polygons containing a given point on the sphere,rapidly decomposes a set of polygons into disjoint parts,expands masks in spherical harmonics,generates random points with weights given by the mask, and implements computations for correlation function analysis.To mangle, a mask is an arbitrary union of arbitrarily weighted angular regions bounded by arbitrary numbers of edges. The restrictions on the mask are only (1) that each edge must be part of some circle on the sphere (but not necessarily a great circle), and (2) that the weight within each subregion of the mask must be constant. Mangle is complementary to and integrated with the HEALPix package; mangle works with vector graphics whereas HEALPix works with pixels.

  15. Angular movement optical sensor

    NASA Astrophysics Data System (ADS)

    Palma-Vargas, Salvador; Sandoval-Romero, G. Eduardo; Ramírez-Ibarra, Angélica

    2006-09-01

    Most of the investigations that exist about the interferometer of Sagnac in our days, are made through fiber optic, which has the great advantage of having a big area size in very little space wound in a nucleus. The first interferometers of Sagnac, were used for very big angular speeds measures, it didn't have the advances to carry out detections of small signs, because the measurements systems like photo-detectors, amplifiers, filters, etc. didn't have the capacity of the systems that now exist. That is one reason that our experiments are based on the electronic advances, to make detections of phase changes of until less than 0.1 nm with area of 0.025 m2. Besides we proposed changes in the original interferometer diagram, adding some elements that can helps to achieve a bigger sensibility, accuracy and reduction of noise. Another of the advantages of use an interferometer of Sagnac, is work directly with the beams that travel through it, because we can observe the behavior from the optic road to external physical effects, like angular velocity or speed and little movements. Finally the acquisition devises and the software were used for calculate the angular frequency of the sensor directly from the experiment and know the parameters of the movement.

  16. Angular magnetoresistance in semiconducting undoped amorphous carbon thin films

    NASA Astrophysics Data System (ADS)

    Sagar, Rizwan Ur Rehman; Saleemi, Awais Siddique; Zhang, Xiaozhong

    2015-05-01

    Thin films of undoped amorphous carbon thin film were fabricated by using Chemical Vapor Deposition and their structure was investigated by using High Resolution Transmission Electron Microscopy and Raman Spectroscopy. Angular magnetoresistance (MR) has been observed for the first time in these undoped amorphous carbon thin films in temperature range of 2 ˜ 40 K. The maximum magnitude of angular MR was in the range of 9.5% ˜ 1.5% in 2 ˜ 40 K. The origin of this angular MR was also discussed.

  17. ANGULAR MOMENTUM ACQUISITION IN GALAXY HALOS

    SciTech Connect

    Stewart, Kyle R. [Department of Natural and Mathematical Sciences, California Baptist University, 8432 Magnolia Ave., Riverside, CA 92504 (United States); Brooks, Alyson M. [Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter St., Madison, WI 53706 (United States); Bullock, James S. [Center for Cosmology, Department of Physics and Astronomy, University of California at Irvine, Irvine, CA 92697 (United States); Maller, Ariyeh H. [Department of Physics, New York City College of Technology, 300 Jay St., Brooklyn, NY 11201 (United States); Diemand, Juerg [Institute for Theoretical Physics, University of Zurich, 8057, Zurich (Switzerland); Wadsley, James [Department of Physics and Astronomy, McMaster University, Main Street West, Hamilton L85 4M1 (Canada); Moustakas, Leonidas A. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2013-05-20

    We use high-resolution cosmological hydrodynamic simulations to study the angular momentum acquisition of gaseous halos around Milky-Way-sized galaxies. We find that cold mode accreted gas enters a galaxy halo with {approx}70% more specific angular momentum than dark matter averaged over cosmic time (though with a very large dispersion). In fact, we find that all matter has a higher spin parameter when measured at accretion than when averaged over the entire halo lifetime, and is well characterized by {lambda} {approx} 0.1, at accretion. Combined with the fact that cold flow gas spends a relatively short time (1-2 dynamical times) in the halo before sinking to the center, this naturally explains why cold flow halo gas has a specific angular momentum much higher than that of the halo and often forms ''cold flow disks.'' We demonstrate that the higher angular momentum of cold flow gas is related to the fact that it tends to be accreted along filaments.

  18. Development of a new angular displacement sensor based on principle of vernier caliper

    NASA Astrophysics Data System (ADS)

    Zhang, Xinghong; Peng, Donglin; Chen, Xihou; Liu, Xiaokang

    2006-11-01

    In this paper, a new kind of angular high precision displacement based on principle of vernier caliper is proposed. This displacement is sourced from the idea of vernier caliper. The longer arm of vernier caliper with a linear scale and the L-shaped sliding attachment with a vernier are replaced by an inner round part and outer round part with reticle around them. The numbers of reticle around inner part is different from that of outer part. Using the reticle number difference between two parts having relative motion, in the condition of the similar reticle, there exist changes of some physical parameter among the reticles. It can gain more pulse signal. In some cases, the numbers of pulse signal is approximately equal to the product of the two numbers of reticles around inner and outer round parts, which has identical consequence of pulse interpolation or frequency doubling. Through which the goal of improving resolution is achieved. The design idea, the working principle, the signal analysis, the precision analysis and the experiment result of this angular displacement sensor are introduced. The research result shows that thickness, spacing and number of reticles can directly affect the number, amplitude, wave shape, accuracy and other characteristics of the pulse signal. It will play an important rule in improving the traditional grating type angular displacement sensor technology.

  19. MULTI-RESOLUTION APPROXIMATE INVERSE PRECONDITIONERS

    E-print Network

    Bridson, Robert

    compress the inverse of the matrix, allowing an effective sparse approx- imate inverse by solving the sparsity vs. accuracy conflict. The key issue in this compression is to use second-generation wavelets reason is that they can be efficiently applied (with just matrix-vector products) on high per- formance

  20. Angular differential cross section calculations for ion-helium collisions

    NASA Astrophysics Data System (ADS)

    Zapukhlyak, M.; Kirchner, T.

    2009-11-01

    We have calculated projectile angular-differential cross sections for various processes in ion-helium collisions. Key ingredients of our approach are the independent electron model, the two-center basis generator method for orbital propagation, and the eikonal approximation for the extraction of angular-differential scattering amplitudes. In general, we find good agreement with measurements; in some cases even for two-electron processes, although correlation effects are not taken into account.

  1. Estimating Energy-Momentum and Angular Momentum Near Null Infinity

    E-print Network

    Adam D. Helfer

    2010-02-19

    The energy-momentum and angular momentum contained in a spacelike two-surface of spherical topology are estimated by joining the two-surface to null infinity via an approximate no-incoming-radiation condition. The result is a set of gauge-invariant formulas for energy-momentum and angular momentum which should be applicable to much numerical work; it also gives estimates of the finite-size effects.

  2. Estimating energy-momentum and angular momentum near null infinity

    SciTech Connect

    Helfer, Adam D. [Department of Mathematics, University of Missouri, Columbia, Missouri 65211 (United States)

    2010-04-15

    The energy-momentum and angular momentum contained in a spacelike two-surface of spherical topology are estimated by joining the two-surface to null infinity via an approximate no-incoming-radiation condition. The result is a set of gauge-invariant formulas for energy-momentum and angular momentum which should be applicable to much numerical work; it also gives estimates of the finite-size effects.

  3. High angular resolution cosmic X-ray astronomy observations in the energy range 0.15-2 keV and XUV observations of nearby stars from an attitude controlled rocket

    NASA Technical Reports Server (NTRS)

    Garmire, G. P.

    1974-01-01

    The construction of a two dimensional focusing Wolter Type I mirror system for X-ray and XUV astronomical observations from an Astrobee F sounding rocket is described. The mirror design goal will have a one degree field, a 20-arc seconds resolution, an effective area of about 50 sq cm at 1 keV and 10 sq cm at 0.25 keV on axis. A star camera provides aspect data to about 15-arc seconds. Two detectors are placed at the focus with an interchange mechanism to allow a detector change during flight. The following specific developments are reported: (1) position sensitive proportional counter development; (2) channel plate multiplier development; (3) telescope mirror development and payload structure; (4) Australian rocket flight results; (5) Comet Kohoutek He I observation; and (6) Vela, Puppis A, and Gem-Mon bright patch observations.

  4. Angular Momentum in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Del Popolo, A.

    We study the ``angular momentum catastrophe" in the framework of interaction among baryons and dark matter through dynamical friction. By means of Del Popolo (2009) model we simulate 14 galaxies similar to those investigated by van den Bosch, Burkert and Swaters (2001), and calculate the distribution of their spin parameters and the angular momenta. Our model gives the angular momentum distribution which is in agreement with the van den Bosch et al. observations. Our result shows that the ``angular momentum catastrophe" can be naturally solved in a model that takes into account the baryonic physics and the exchange of energy and angular momentum between the baryonic clumps and dark matter through dynamical friction.

  5. Angular Momentum Operators from Quantized SO(3)

    E-print Network

    Ahmad Adel Abutaleb

    2015-06-15

    In this paper, we will assume that the structure picture of the rotation angles will be changed according to the scale of measurement (minimum measurable angle) and if we have a device with very high accuracy (high resolution) then we can notice a discrete nature of the rotations. We derived the form of the angular momentum matrices and angular momentum operators in this case and we find an indication of the need to change all quantum mechanical operators at this very small scale (high energy level). As a physical consequence, we calculated the magnetic quantum number and find that it has been shifted to a fractional multiples of h and therefore the spin of quantum particles is no longer take integer or half integer values but some fractional values between them.

  6. Boson Star Rotation: A Newtonian Approximation

    E-print Network

    Vanda Silveira; Claudio M. G. de Sousa

    1995-08-08

    Using the Newtonian approximation, we study rotating compact bosonic objects. The equations which describe stationary states with non-zero angular momentum are constructed and some numerical results are presented as examples. Limits on the applicability of the Newtonian approximation are discussed.

  7. Approximations performance

    E-print Network

    Gautam, Natarajan

    Approximations for system performance under self­similar traffic N. Gautam Department of Industrial) in networks are Leland et al [13] in ethernet LAN traffic. Ever since, several experiments and measurements

  8. Uniaxial angular accelerometers

    NASA Astrophysics Data System (ADS)

    Seleznev, A. V.; Shvab, I. A.

    1985-05-01

    The basic mechanical components of an angular accelerometer are the sensor, the damper, and the transducer. Penumatic dampers are simplest in construction, but the viscosity of air is very low and, therefore, dampers with special purpose oils having a high temperature stability (synthetic silicon or organosilicon oils) are most widely used. The most common types of viscous dampers are lamellar with meshed opposed arrays of fixed and movable vanes in the dashpot, piston dampers regulated by an adjustable-length capillary tube, and dampers with paddle wheel in closed tank. Another type of damper is an impact-inertial one with large masses absorbing the rotational energy upon collision with the sensor. Conventional measuring elements are resistive, capacitive, electromagnetic, photoelectric, and penumatic or hydraulic. Novel types of angular accelerometers are based on inertia of gas jets, electron beams, and ion beams, the piezoelectric effect in p-n junctions of diode and transistors, the electrokinetic effect in fluids, and cryogenic suspension of the sensor.

  9. Angular velocity optical sensor

    NASA Astrophysics Data System (ADS)

    Palma-Vargas, Salvador; Sandoval-Romero, G. Eduardo; Ramírez-Ibarra, Angélica

    2006-02-01

    Most of the investigations that exist about the interferometer of Sagnac in our days, are made through fiber optic, which has the great advantage of having a big area size in very little space wound in a nucleus. The first interferometers of Sagnac, were used for very big angular speeds measures, it didn't have the advances to carry out detections of small signs, because the measurements systems like photo-detectors, amplifiers, filters, etc. didn't have the capacity of the systems that now exist. That is one reason that our experiments are based on the electronic advances, to make detections of phase changes of until less than 0.1 nm with area of 0.025 m2. Besides we proposed changes in the original interferometer diagram, adding some elements that can helps to achieve a bigger sensibility, accuracy and reduction of noise. Another of the advantages of use an interferometer of Sagnac, is work directly with the beams that travel through it, because we can observe the behavior from the optic road to external physical effects, like angular velocity or speed and little movements.

  10. Fabricating BRDFs at high spatial resolution using wave optics

    E-print Network

    Levin, Anat

    Recent attempts to fabricate surfaces with custom reflectance functions boast impressive angular resolution, yet their spatial resolution is limited. In this paper we present a method to construct spatially varying reflectance ...

  11. Supersensitive measurement of angular displacements using entangled photons

    SciTech Connect

    Jha, Anand Kumar; Boyd, Robert W. [The Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Agarwal, Girish S. [Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078 (United States)

    2011-05-15

    We show that the use of path-entangled states of photons, having nonzero orbital angular momentum (OAM), increases the resolution and sensitivity of angular-displacement measurements performed using an interferometer. In the ideal case of maximally path-entangled states, the resolution of angular-displacement measurements increases by a factor of Nl, while the uncertainty in the measurement of angular displacements scales as 1/Nl, where N is the number of entangled photons, half of which carry, on average, an OAM of +l({h_bar}/2{pi}) per photon and the other half carry an OAM of -l({h_bar}/2{pi}) per photon. We analyze measurement schemes for two- and four-photon entangled states produced by parametric down-conversion and, by employing a 4x4 matrix formalism to study the propagation of entangled OAM modes, obtain explicit expressions for the resolution and sensitivity in these schemes. These results constitute an improvement over what could be obtained with N nonentangled photons carrying an orbital angular momentum of |l|({h_bar}/2{pi}) per photon.

  12. Magnetic angular encoder using an offset compensation technique

    Microsoft Academic Search

    Maher Kayal; Frederic Burger; Radivoje S. Popovic

    2004-01-01

    Quality and resolution of integrated microsystems using Hall sensors dedicated to an angular encoder are strongly dependent on the accuracy of the relative position of Hall sensors and on the offset of electronic front end circuitry. In this paper, we describe a CMOS microsystem built on two integrated circuits. This contactless encoder microsystem gives three sine and square signals with

  13. The angular momentum of baryons and dark matter halos revisited

    Microsoft Academic Search

    Taysun Kimm; Julien Devriendt; Adrianne Slyz; Christophe Pichon; Susan A. Kassin; Yohan Dubois

    2011-01-01

    Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive mesh refinement, we find that at the time of accretion, gas and dark matter do carry a similar amount of specific

  14. Minimum uncertainty states of angular momentum and angular position

    Microsoft Academic Search

    David T. Pegg; Stephen M. Barnett; Roberta Zambrini; Sonja Franke-Arnold; Miles Padgett

    2005-01-01

    The states of linear momentum that satisfy the equality in the Heisenberg uncertainty principle for position and momentum, that is the intelligent states, are also the states that minimize the uncertainty product for position and momentum. The corresponding uncertainty relation for angular momentum and angular position, however, is more complicated and the intelligent states need not be the constrained minimum

  15. Wissenschaftliches Approximation

    E-print Network

    Auzinger, Winfried

    ' am Digitalcomputer Archimedes und die Berechnung von = 3.14159 . . . Das leidige Integral Das Einleitung: `Alles ist Zahl' am Digitalcomputer Archimedes und die Berechnung von = 3.14159 . . . Das Approximation als Sparmaßnahme Anhang Überblick Einleitung: `Alles ist Zahl' am Digitalcomputer Archimedes und

  16. Logical approximation

    Microsoft Academic Search

    Irina Perfilieva

    2002-01-01

    The principle approach to the construction of approximating formulas is discussed. We suggest the generalized definition\\u000a of normal forms in predicate BL-logic and prove the conditional equivalence between a formula and each of its normal forms.\\u000a Some mutual relations between normal forms will be also established.

  17. Large-uncertainty intelligent states for angular momentum and angle

    E-print Network

    Goette, J B; Franke-Arnold, S; Barnett, S M; Goette, Joerg B.; Zambrini, Roberta; Franke-Arnold, Sonja; Barnett, Stephen M.

    2005-01-01

    The equality in the uncertainty principle for linear momentum and position is obtained for states which also minimize the uncertainty product. However, in the uncertainty relation for angular momentum and angular position both sides of the inequality are state dependent and therefore the intelligent states, which satisfy the equality, do not necessarily give a minimum for the uncertainty product. In this paper, we highlight the difference between intelligent states and minimum uncertainty states by investigating a class of intelligent states which obey the equality in the angular uncertainty relation while having an arbitrarily large uncertainty product. To develop an understanding for the uncertainties of angle and angular momentum for the large-uncertainty intelligent states we compare exact solutions with analytical approximations in two limiting cases.

  18. Large-uncertainty intelligent states for angular momentum and angle

    E-print Network

    Joerg B. Goette; Roberta Zambrini; Sonja Franke-Arnold; Stephen M. Barnett

    2005-10-20

    The equality in the uncertainty principle for linear momentum and position is obtained for states which also minimize the uncertainty product. However, in the uncertainty relation for angular momentum and angular position both sides of the inequality are state dependent and therefore the intelligent states, which satisfy the equality, do not necessarily give a minimum for the uncertainty product. In this paper, we highlight the difference between intelligent states and minimum uncertainty states by investigating a class of intelligent states which obey the equality in the angular uncertainty relation while having an arbitrarily large uncertainty product. To develop an understanding for the uncertainties of angle and angular momentum for the large-uncertainty intelligent states we compare exact solutions with analytical approximations in two limiting cases.

  19. Fission-fragment angular distributions

    SciTech Connect

    Bond, P.D.

    1984-02-06

    The universally used ''exact'' formula for fission-fragment angular distributions is shown to be valid only under restrictive assumptions. The more general expression, which depends crucially on the final fragment spin distributions, predicts dramatically more anisotropic angular distributions for fission from nuclei at high spin. Recent ''anomalous'' results are analyzed.

  20. Fission-Fragment Angular Distributions

    NASA Astrophysics Data System (ADS)

    Bond, P. D.

    1984-02-01

    The universally used "exact" formula for fission-fragment angular distributions is shown to be valid only under restrictive assumptions. The more general expression, which depends crucially on the final fragment spin distributions, predicts dramatically more anisotropic angular distributions for fission from nuclei at high spin. Recent "anomalous" results are analyzed.

  1. Angular integrals in d dimensions

    NASA Astrophysics Data System (ADS)

    Somogyi, Gábor

    2011-08-01

    We discuss the evaluation of certain d-dimensional angular integrals which arise in perturbative field theory calculations. We find that the angular integral with n denominators can be computed in terms of a certain special function, the so-called H-function of several variables. We also present several illustrative examples of the general result and briefly consider some applications.

  2. Envelope Modes of Beams with Angular Momentum

    SciTech Connect

    Barnard, J J; Losic, B

    2000-08-21

    For a particle beam propagating in an alternating gradient focusing system, envelope equations are often employed to describe the evolution of the beam radii in the two directions transverse to the direction of propagation, and aligned with the principle axes of the alternating gradient system. When the beams have zero net angular momentum and when the alternating gradient focusing is approximated by a continuous focusing system, there are two normal modes to the envelope equations: the 'breathing' mode and a 'quadrupole' mode. In the former, the two radii oscillate in phase, and in the latter the radii oscillate 180 degrees out of phase. In this paper, we extend the analysis to include beams that have a finite angular momentum. We perturb the moment equations of ref. [1], wherein it was assumed that space charge is a distributed in a uniform density ellipse. Two additional modes are obtained. The breathing mode remains, but the quadrupole mode is split into two modes, and a new low frequency mode appears. We calculate the frequencies and eigenmodes of these four modes as a function of tune depression and a dimensionless net angular momentum. These modes can be excited by rotational errors of the quadrupoles in an alternating gradient focusing channel.

  3. The Angular Gyrus

    PubMed Central

    2013-01-01

    There is considerable interest in the structural and functional properties of the angular gyrus (AG). Located in the posterior part of the inferior parietal lobule, the AG has been shown in numerous meta-analysis reviews to be consistently activated in a variety of tasks. This review discusses the involvement of the AG in semantic processing, word reading and comprehension, number processing, default mode network, memory retrieval, attention and spatial cognition, reasoning, and social cognition. This large functional neuroimaging literature depicts a major role for the AG in processing concepts rather than percepts when interfacing perception-to-recognition-to-action. More specifically, the AG emerges as a cross-modal hub where converging multisensory information is combined and integrated to comprehend and give sense to events, manipulate mental representations, solve familiar problems, and reorient attention to relevant information. In addition, this review discusses recent findings that point to the existence of multiple subdivisions in the AG. This spatial parcellation can serve as a framework for reporting AG activations with greater definition. This review also acknowledges that the role of the AG cannot comprehensibly be identified in isolation but needs to be understood in parallel with the influence from other regions. Several interesting questions that warrant further investigations are finally emphasized. PMID:22547530

  4. Extending the Eikonal Approximation to Low Energy

    E-print Network

    Pierre Capel; Tokuro Fukui; Kazuyuki Ogata

    2014-11-21

    E-CDCC and DEA, two eikonal-based reaction models are compared to CDCC at low energy (e.g. 20AMeV) to study their behaviour in the regime at which the eikonal approximation is supposed to fail. We confirm that these models lack the Coulomb deflection of the projectile by the target. We show that a hybrid model, built on the CDCC framework at low angular momenta and the eikonal approximation at larger angular momenta gives a perfect agreement with CDCC. An empirical shift in impact parameter can also be used reliably to simulate this missing Coulomb deflection.

  5. The angular correlation hierarchy in the quasilinear regime.

    E-print Network

    F. Bernardeau

    1995-02-21

    For Gaussian initial conditions the perturbation theory predicts a very specific hierarchy for the projected matter $p$-point correlation functions. In the small angle approximation and assuming a power-law spectrum I derive the exact expressions of the coefficients $s_p$ relating the averaged $p$-order angular correlation function, $\\omb_p$ to the second one, $\\omb_p=s_p\\ \\omb_2^{p-1}$. These results are valid for any selection function, but for a top-hat angular filter only. These coefficients are found to be significantly higher than their 3D counterparts, $S_p=\\xib_p/\\xib_2^{p-1}$. For the coefficient $s_3$ I discussed the accuracy of the small angle approximation by computing, for particular examples, its angular dependence with Monte-Carlo numerical integrations. It is found that the accuracy of the small angle approximation for $\\theta\\approx 1^o$ slightly depends on the selection function. Using the selection function expected for galaxy catalogues the approximation is found to be reasonably good. The measurements of the $s_p$ parameters made in the APM angular survey are found to give systematic lower values than the theoretical predictions. How significant this discrepancy is and what the implications would be for galaxy formation models is discussed in the last section.

  6. On the simplest presentation of the molecular frame photoelectron angular distributions for core levels

    Microsoft Academic Search

    S K Semenov; N A Cherepkov

    2009-01-01

    It is shown that four two-dimensional angular distributions of photoelectrons ejected from core levels of fixed-in-space linear molecules constitute a minimal set sufficient to reproduce any three-dimensional angular distribution for arbitrary light polarization and for arbitrary direction of the light beam relative to the molecular axis in the dipole approximation. Experimentally these four two-dimensional angular distributions can be measured by

  7. Angular momentum & spin January 8, 2002

    E-print Network

    Landstreet, John D.

    Angular momentum & spin January 8, 2002 1 Angular momentum Angular momentum appears as a very properties of this quantity. 1.1 Definitions The classical definition of the angular momentum of a particle¯h, the quantum mechanical operator for angular momentum becomes L = -i¯h(r × ), for example Lz = -i¯h(x y - y x

  8. Detection and recognition of angular frequency patterns.

    PubMed

    Wilson, Hugh R; Propp, Roni

    2015-05-01

    Previous research has extensively explored visual encoding of smoothly curved, closed contours described by sinusoidal variation of pattern radius as a function of polar angle (RF patterns). Although the contours of many biologically significant objects are curved, we also confront shapes with a more jagged and angular appearance. To study these, we introduce here a novel class of visual stimuli that deform smoothly from a circle to an equilateral polygon with N sides (AF patterns). Threshold measurements reveal that both AF and RF patterns can be discriminated from circles at the same deformation amplitude, approximately 18.0arcsec, which is in the hyperacuity range. Thresholds were slightly higher for patterns with 3.0 cycles than for those with 5.0 cycles. Discrimination between AF and RF patterns was 75% correct at an amplitude that was approximately 3.0 times the threshold amplitude, which implies that AF and RF patterns activate different neural populations. Experiments with jittered patterns in which the contour was broken into several pieces and shifted inward or outward had much less effect on AF patterns than on RF patterns. Similarly, thresholds for single angles of AF patterns showed no significant difference from thresholds for the entire AF pattern. Taken together, these results imply that the visual system incorporates angles explicitly in the representation of closed object contours, but it suggests that angular contours are represented more locally than are curved contours. PMID:25782363

  9. A novel model of the geometric and detector response for limited angular sampling pinhole SPECT

    NASA Astrophysics Data System (ADS)

    Wietholt, Christian; Hsiao, Ing-Tsung; Clough, Anne V.; Chen, Chin-Tu

    2006-03-01

    Reconstruction methodologies for data sets with reduced angular sampling (RAS) are essential for efficient dynamic or static preclinical animal imaging research using single photon emission computed tomography (SPECT). Modern iterative reconstruction methods can obtain 3D radiotracer distributions of the highest possible quality and resolution. Essential to these algorithms is an accurate model of the physical imaging process. We developed a new point-spread function (PSF) model for the pinhole geometry and compared it to a Gaussian model in a RAS setting. The new model incorporates the geometric response of the pinhole and the detector response of the camera by simulating the system PSF using the error function. Reconstruction of simulated data was done with OS-EM and COS-EM: a new convergent OS-EM based algorithm. The reconstruction of projection data of a simulated point source using the novel method showed improved FWHM values compared to a standard Gaussian method. COS-EM delivers improved results for RAS data, although it converges slower than OS-EM. The reconstruction of Monte Carlo simulated projection data from a resolution phantom shows that as few as 40 projections are sufficient to reconstruct an image with a resolution of approximately 4 mm. The new pinhole model applied to iterative reconstruction methods can reduce imaging time in small animal experiments by a factor of three or reduce the number of cameras needed to perform dynamic SPECT.

  10. Resolution-Tunable Angle-Resolved X-ray Imaging

    SciTech Connect

    Hirano, Keiichi [Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

    2004-05-12

    A resolution-tunable double-crystal device was successfully applied to angle-resolved x-ray imaging. The angular resolution of a Si (220) double-crystal analyzer was tuned between 0.5'' and 2.3'' through the offset angle at {lambda} = 0.0733nm. The throughput of the analyzer was higher than 90%. The angle-resolved images of a spider were recorded on nuclear emulsion plates at various angular resolutions. It was clearly observed that the quality of the angle-resolved image varies with the angular resolution of the analyzer.

  11. Longitudinal profile diagnostic scheme with subfemtosecond resolution for high-brightness electron beams

    NASA Astrophysics Data System (ADS)

    Andonian, G.; Hemsing, E.; Xiang, D.; Musumeci, P.; Murokh, A.; Tochitsky, S.; Rosenzweig, J. B.

    2011-07-01

    High-resolution measurement of the longitudinal profile of a relativistic electron beam is of utmost importance for linac based free-electron lasers and other advanced accelerator facilities that employ ultrashort bunches. In this paper, we investigate a novel scheme to measure ultrashort bunches (subpicosecond) with exceptional temporal resolution (hundreds of attoseconds) and dynamic range. The scheme employs two orthogonally oriented deflecting sections. The first imparts a short-wavelength (fast temporal resolution) horizontal angular modulation on the beam, while the second imparts a long-wavelength (slow) angular kick in the vertical dimension. Both modulations are observable on a standard downstream screen in the form of a streaked sinusoidal beam structure. We demonstrate, using scaled variables in a quasi-1D approximation, an expression for the temporal resolution of the scheme and apply it to a proof-of-concept experiment at the UCLA Neptune high-brightness injector facility. The scheme is also investigated for application at the SLAC NLCTA facility, where we show that the subfemtosecond resolution is sufficient to resolve the temporal structure of the beam used in the echo-enabled free-electron laser. We employ beam simulations to verify the effect for typical Neptune and NLCTA parameter sets and demonstrate the feasibility of the concept.

  12. Longitudinal Profile Diagnostic Scheme with Subfemtosecond Resolution for High-Brightness Electron Beams

    SciTech Connect

    Andonian, G.; /UCLA /RadiaBeam Tech.; Hemsing, E.; /UCLA; Xiang, D.; /SLAC; Musumeci, P.; /UCLA; Murokh, A.; /RadiaBeam Tech.; Tochitsky, S.; /UCLA; Rosenzweig, J.B.; /UCLA

    2012-05-03

    High-resolution measurement of the longitudinal profile of a relativistic electron beam is of utmost importance for linac based free-electron lasers and other advanced accelerator facilities that employ ultrashort bunches. In this paper, we investigate a novel scheme to measure ultrashort bunches (subpicosecond) with exceptional temporal resolution (hundreds of attoseconds) and dynamic range. The scheme employs two orthogonally oriented deflecting sections. The first imparts a short-wavelength (fast temporal resolution) horizontal angular modulation on the beam, while the second imparts a long-wavelength (slow) angular kick in the vertical dimension. Both modulations are observable on a standard downstream screen in the form of a streaked sinusoidal beam structure. We demonstrate, using scaled variables in a quasi-1D approximation, an expression for the temporal resolution of the scheme and apply it to a proof-of-concept experiment at the UCLA Neptune high-brightness injector facility. The scheme is also investigated for application at the SLAC NLCTA facility, where we show that the subfemtosecond resolution is sufficient to resolve the temporal structure of the beam used in the echo-enabled free-electron laser. We employ beam simulations to verify the effect for typical Neptune and NLCTA parameter sets and demonstrate the feasibility of the concept.

  13. Angular Momentum Accretion onto a Gas Giant Planet

    E-print Network

    Masahiro N. Machida; Eiichiro Kokubo; Shu-ichiro Inutsuka; Tomoaki Matsumoto

    2008-01-22

    We investigate the accretion of angular momentum onto a protoplanet system using three-dimensional hydrodynamical simulations. We consider a local region around a protoplanet in a protoplanetary disk with sufficient spatial resolution. We describe the structure of the gas flow onto and around the protoplanet in detail. We find that the gas flows onto the protoplanet system in the vertical direction crossing the shock front near the Hill radius of the protoplanet, which is qualitatively different from the picture established by two-dimensional simulations. The specific angular momentum of the gas accreted by the protoplanet system increases with the protoplanet mass. At Jovian orbit, when the protoplanet mass M_p is M_p angular momentum increases as j \\propto M_p. On the other hand, it increases as j \\propto M_p^2/3 when the protoplanet mass is M_p > 1 M_J. The stronger dependence of the specific angular momentum on the protoplanet mass for M_p angular momentum of a system of a gas giant planet and a circumplanetary disk is two-orders of magnitude larger than those of the present gas giant planets in the solar system. A large fraction of the total angular momentum contributes to the formation of the circumplanetary disk. We also discuss the satellite formation from the circumplanetary disk.

  14. Theory for noise of propellers in angular inflow with parametric studies and experimental verification

    Microsoft Academic Search

    Donald B. Hanson; David J. Parzych

    1993-01-01

    This report presents the derivation of a frequency domain theory and working equations for radiation of propeller harmonic noise in the presence of angular inflow. In applying the acoustic analogy, integration over the tangential coordinate of the source region is performed numerically, permitting the equations to be solved without approximation for any degree of angular inflow. Inflow angle is specified

  15. "High Angular Resolution Observations of Protoplanetary Disks with Adaptive Optics"

    NASA Technical Reports Server (NTRS)

    Roddier, Francois

    1999-01-01

    Significant results were obtained and published in the literature. The first optical detection of a circumbinary disk was reported in the ApJ at millimetric wavelengths. The size and inclination of this disk were found to be consistent with millimetric observations. Evidence was found for a cavity inside the disk as theory predicts from dust clearing by the stellar companion.

  16. An Acousto-Optical Sensor with High Angular Resolution

    PubMed Central

    Kaloshin, Gennady; Lukin, Igor

    2012-01-01

    The paper introduces a new laser interferometry-based sensor for diagnosis of random media by means of high accuracy angle measurements and describes the results of its development and testing. Theoretical calculations of the dependence of the range of the laser interferometer on laser beam parameters, device geometry, and atmospheric turbulence characteristics are reported. It is demonstrated that at moderate turbulence intensities corresponding to those observed most frequently in turbulent atmosphere at moderate latitudes and with low interference contrast values, the performance range of the laser interferometer-based device exceeds 5 km. PMID:22737034

  17. Photoelectron spectrometer for high-resolution angular resolved studies

    Microsoft Academic Search

    A. C. Parr; S. H. Southworth; J. L. Dehner; D. M. P. Holland

    1982-01-01

    A new electron spectrometer system designed for use n storage-ring light sources is described. The system features a large (76 cm dia. x 92 cm long ) triply magnetically shielded vacuum chamber and two 10.2 cm mean radius hemispherical electron-energy analyzers. One of the analyzers is fixed and the other is rotatable through about 150 deg. The chamber is pumped

  18. Photoelectron spectrometer for high-resolution angular resolved studies

    SciTech Connect

    Parr, Albert C.; Southworth, Stephen H.; Dehmer, Joseph L.; Holland, David M.P.

    1982-08-01

    We report on a new electron spectrometer system designed for use on storage-ring light sources. The system features a large (76 cm dia. x 92 cm long) triply magnetically shielded vacuum chamber and two 10.2 cm mean radius hemispherical electron-energy analyzers. One of the analyzers is fixed and the other is rotatable through about 150 deg. The chamber is pumped by a cryopump and a turbomolecular pump combination so as to enable experiments with a variety of gases under different conditions. The light detection includes both a direct beam monitor and polarization analyzer. The electron detection is accomplished with either a continuous-channel electron multiplier or with multichannel arrays used as area detectors.

  19. Angular Momentum Balance Tuesday, January 7, 2014

    E-print Network

    Bordoni, Simona

    Angular Momentum Balance and Winds Tuesday, January 7, 2014 #12;(Source: CLAUS, http Extratropical macroturbulence transports angular momentum into regions of wave generation !"#$%&'( )*+,( )*+-( Tuesday, January 7, 2014 #12;Eddy angular momentum transport (ERA-40 Atlas, http

  20. Angular correlations of galaxy distribution

    E-print Network

    M. Montuori; F. Sylos-Labini

    1997-06-30

    We study the angular correlations of various galaxy catalogs (CfA1, SSRS1, Perseus-Pisces, APM Bright Galaxies and Zwicky). We find that the angular correlation exponent is $\\gamma_a= 0.1 \\pm 0.1$ rather than $\\gamma_a=0.7$ as usually found by the standard correlation function $\\omega(\\theta)$. We identify the problem in the artificial decay of $\\omega(\\theta)$. Moreover we find that no characteristic angular scale is present in any of the analyzed catalogs. Finally we show that all the available data are consistent with each other and the angular distribution of galaxies is quite naturally compatible with a fractal structure with $D \\approx 2$.

  1. Transverse angular momentum of photons

    E-print Network

    Andrea Aiello; Christoph Marquardt; Gerd Leuchs

    2010-03-04

    We develop the quantum theory of transverse angular momentum of light beams. The theory applies to paraxial and quasi-paraxial photon beams in vacuum, and reproduces the known results for classical beams when applied to coherent states of the field. Both the Poynting vector, alias the linear momentum, and the angular momentum quantum operators of a light beam are calculated including contributions from first-order transverse derivatives. This permits a correct description of the energy flow in the beam and the natural emergence of both the spin and the angular momentum of the photons. We show that for collimated beams of light, orbital angular momentum operators do not satisfy the standard commutation rules. Finally, we discuss the application of our theory to some concrete cases.

  2. Transverse angular momentum of photons

    SciTech Connect

    Aiello, Andrea [Max Planck Institute for the Science of Light, Guenter-Scharowsky-Strasse 1/Bau 24, D-91058 Erlangen (Germany); Marquardt, Christoph; Leuchs, Gerd [Max Planck Institute for the Science of Light, Guenter-Scharowsky-Strasse 1/Bau 24, D-91058 Erlangen (Germany); Institute for Optics, Information and Photonics, University Erlangen-Nuernberg, Staudtstrasse 7/B2, D-91058 Erlangen (Germany)

    2010-05-15

    We develop the quantum theory of transverse angular momentum of light beams. The theory applies to paraxial and quasiparaxial photon beams in vacuum and reproduces the known results for classical beams when applied to coherent states of the field. Both the Poynting vector, alias the linear momentum, and the angular-momentum quantum operators of a light beam are calculated including contributions from first-order transverse derivatives. This permits a correct description of the energy flow in the beam and the natural emergence of both the spin and the angular momentum of the photons. We show that for collimated beams of light, orbital angular-momentum operators do not satisfy the standard commutation rules. Finally, we discuss the application of our theory to some concrete cases.

  3. A halo expansion technique for approximating simulated dark matter haloes

    NASA Astrophysics Data System (ADS)

    Lowing, Ben; Jenkins, Adrian; Eke, Vincent; Frenk, Carlos

    2011-10-01

    We apply a basis function expansion method to create a time-evolving density/potential approximation of the late growth of simulated N-body dark matter haloes. We demonstrate how the potential of a halo from the Aquarius Project can be accurately represented by a small number of basis functions, and show that the halo expansion (HEX) method provides a way to replay simulations. We explore the level of accuracy of the technique as well as some of its limitations. We find that the number of terms included in the expansion must be large enough to resolve the large-scale distribution and shape of the halo but, beyond this, additional terms result in little further improvement. Particle and subhalo orbits can be integrated in this realistic, time-varying halo potential approximation, at much lower cost than the original simulation, with high fidelity for many individual orbits, and a good match to the distributions of orbital energy and angular momentum. Statistically, the evolution of structural subhalo properties, such as mass, half-mass radius and characteristic circular velocity, are very well reproduced in the HEX approximation over several Gyr. We demonstrate an application of the technique by following the evolution of an orbiting subhalo at much higher resolution than can be achieved in the original simulation. Our method represents a significant improvement over commonly used techniques based on static analytical descriptions of the halo potential.

  4. Angular momentum and Killing potentials

    NASA Astrophysics Data System (ADS)

    Glass, E. N.

    1996-01-01

    When the Penrose-Goldberg (PG) superpotential is used to compute the angular momentum of an axial symmetry, the Killing potential Q??(?) for that symmetry is needed. Killing potentials used in the PG superpotential must satisfy Penrose's equation. It is proved for the Schwarzschild and Kerr solutions that the Penrose equation does not admit a Q??(?) at finite r and therefore the PG superpotential can only be used to compute angular momentum asymptotically.

  5. Very high resolution radiometer

    Microsoft Academic Search

    A. I. Aronson

    1974-01-01

    A primary sensor used in environmental and earth-resource observation, the Very High Resolution Radiometer (VHRR) was designed for use on the ITOS D series spacecraft. The VHRR provides a 0.47 mile resolution made possible with a mercury-cadmium-telluride detector cooled to approximately 105 K by a passive radiator cooler. The components of this system are described. The optical subsystem of the

  6. The angular momentum of condensations within elephant trunks

    E-print Network

    Lora, V; Esquivel, A

    2009-01-01

    The radiation from newly born stars photoevaporates their parental neutral cloud, leading to the formation of dense clumps that will eventually form stars. We present 3D simulations of the interaction of a neutral cloud with an external ionising radiation field, and compute the angular momenta of these collapsing clumps. The angular momenta of these collapsing clumps show that they have preferential orient mostly perpendicular to the direction of the incident ionising photon field. Therefore, the axes of the jet systems that will be eventually ejected (from the star + accretion disk systems that will form) will be oriented approximately perpendicular to the direction to the photoionising source.

  7. Angular and spectrally resolved investigation of single particles by darkfield scattering microscopy.

    PubMed

    Rothe, Thomas; Schmitz, Michael; Kienle, Alwin

    2012-11-01

    A darkfield scattering microscope has been constructed that enables both angular and spectrally resolved measurements of elastic scattering patterns. The comparison of the angular and spectral resolution modes is shown in detail. Angular patterns of the backscattered light by homogeneous polystyrene spheres were measured at 57 wavelengths and the diameters of the single spheres were determined by using Mie theory at each wavelength. The mean diameter values were estimated in the angular mode with a relative standard deviation of 0.25% or less. Spectral scattering patterns of the same beads were investigated and the diameters were determined and compared with the results of the angular measurements. The estimated diameter values in the angular and the spectral mode were in an excellent agreement with deviations of less than 0.20%. PMID:23214188

  8. Angular momentum transport and disk morphology in SPH simulations of galaxy formation

    E-print Network

    Tobias Kaufmann; Lucio Mayer; James Wadsley; Joachim Stadel; Ben Moore

    2006-11-21

    We perform controlled N-Body/SPH simulations of disk galaxy formation by cooling a rotating gaseous mass distribution inside equilibrium cuspy spherical and triaxial dark matter halos. We systematically study the angular momentum transport and the disk morphology as we increase the number of dark matter and gas particles from 10^4 to 10^6, and decrease the gravitational softening from 2 kpc to 50 parsecs. The angular momentum transport, disk morphology and radial profiles depend sensitively on force and mass resolution. At low resolution, similar to that used in most current cosmological simulations, the cold gas component has lost half of its initial angular momentum via different mechanisms. The angular momentum is transferred primarily to the hot halo component, by resolution-dependent hydrodynamical and gravitational torques, the latter arising from asymmetries in the mass distribution. In addition, disk-particles can lose angular momentum while they are still in the hot phase by artificial viscosity. In the central disk, particles can transfer away over 99% of their initial angular momentum due to spiral structure and/or the presence of a central bar. The strength of this transport also depends on force and mass resolution - large softening will suppress the bar instability, low mass resolution enhances the spiral structure. This complex interplay between resolution and angular momentum transfer highlights the complexity of simulations of galaxy formation even in isolated haloes. With 10^6 gas and dark matter particles, disk particles lose only 10-20% of their original angular momentum, yet we are unable to produce pure exponential profiles.

  9. Microstructural characteristics of an ultrafine grain metal processed with equal-channel angular pressing

    SciTech Connect

    Furukawa, Minoru [Fukuoka Univ. of Education, Munakata, Fukuoka (Japan). Dept. of Technology] [Fukuoka Univ. of Education, Munakata, Fukuoka (Japan). Dept. of Technology; Horita, Zenji; Nemoto, Minoru [Kyushu Univ., Fukuoka (Japan). Dept. of Materials Science and Engineering] [Kyushu Univ., Fukuoka (Japan). Dept. of Materials Science and Engineering; Valiev, R.Z. [Ufa State Aviation Technical Univ. (Russian Federation). Inst. of Physics of Advanced Materials] [Ufa State Aviation Technical Univ. (Russian Federation). Inst. of Physics of Advanced Materials; Langdon, T.G. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States)

    1996-11-01

    Equal-channel angular pressing is a procedure for producing a fully dense material with an ultrafine grain size, typically in the submicrometer or nanometer range, by subjecting the material to a very high plastic strain. This paper describes the principle of equal-channel angular pressing and illustrates the capability of the technique by reference to a series of detailed experiments conducted on an Al-3%Mg solid solution alloy in which the grain size was successfully reduced by equal-channel angular pressing from an initial size of {approximately}500{micro}m in the hot-rolled condition to a final size of {approximately}0.2{micro}m.

  10. Angular momentum of isolated systems

    NASA Astrophysics Data System (ADS)

    Helfer, Adam D.

    2007-12-01

    Penrose’s twistorial approach to the definition of angular momentum at null infinity is developed so that angular momenta at different cuts can be meaningfully compared. This is done by showing that the twistor spaces associated with different cuts of mathcal{J}^+ can be identified as manifolds (but not as vector spaces). The result is a well-defined, Bondi-Metzner-Sachs-invariant notion of angular momentum in a radiating space-time; the difficulties and ambiguities previously encountered are attached to attempts to express this in special-relativistic terms, and in particular to attempts to identify a single Minkowski space of origins. Unlike the special-relativistic case, the angular momentum cannot be represented by a purely j = 1 quantity M ab , but has higher- j contributions as well. Applying standard kinematic prescriptions, these higher- j contributions are shown to correspond precisely to the shear. Thus it appears that shear and angular momentum should be regarded as different aspects of a single unified concept.

  11. Angular momentum of isolated systems

    E-print Network

    Adam D. Helfer

    2007-09-07

    Penrose's twistorial approach to the definition of angular momentum at null infinity is developed so that angular momenta at different cuts can be meaningfully compared. This is done by showing that the twistor spaces associated with different cuts of scri can be identified as manifolds (but not as vector spaces). The result is a well-defined, Bondi-Metzner-Sachs-invariant notion of angular momentum in a radiating space-time; the difficulties and ambiguities previously encountered are attached to attempts to express this in special-relativistic terms, and in particular to attempts to identify a single Minkowski space of origins. Unlike the special-relativistic case, the angular momentum cannot be represented by a purely j=1 quantity M_{ab}, but has higher-j contributions as well. Applying standard kinematic prescriptions, these higher-j contributions are shown to correspond precisely to the shear. Thus it appears that shear and angular momentum should be regarded as different aspects of a single unified concept.

  12. ANGULAR MOMENTUM: AN APPROACH TO COMBINATORIAL SPACETIME

    E-print Network

    Baez, John

    ANGULAR MOMENTUM: AN APPROACH TO COMBINATORIAL SPACE­TIME ROGER PENROSE I want to describe an idea­time in a very intimate way, is in angular momentum. The idea here, then, is to start with the concept of angular momentum--- here one has a discrete spectrum---and use the rules for combining angular This paper

  13. Nuclear pairing at finite temperature and angular momentum

    SciTech Connect

    Dang, N. Dinh [Heavy-Ion Nuclear Physics Laboratory, Nishina Center for Accelerator-Based Science, RIKEN 2-1 Hirosawa, Wako city, 351-0198 Saitama, Japan and Institute for Nuclear Science and Technique, Hanoi (Viet Nam); Hung, N. Quang [Heavy-Ion Nuclear Physics Laboratory, Nishina Center for Accelerator-Based Science, RIKEN 2-1 Hirosawa, Wako city, 351-0198 Saitama (Japan)

    2009-01-28

    We propose an approach to nuclear pairing at finite temperature and angular momentum. This approach includes the effects due to the quasiparticle-number fluctuation and dynamic coupling to pair vibrations within the self-consistent quasiparticle random-phase approximation. The pairing gaps, total energies, and heat capacities are calculated within a doubly folded multilevel model as well as several realistic nuclei. The results obtained show that, in the region of moderate and strong couplings, the sharp transition between the superconducting and normal phases is smoothed out. This is manifested in a thermal pairing gap, which does not collapse at a critical temperature predicted by the conventional Bardeen-Cooper-Schrieffer's (BCS) theory, but has a tail extended to high temperatures. Moreover, this approach also predicts the appearance of a thermally assisted pairing at finite angular momentum. The effect of backbending of the momentum of inertia as a function of the square of angular velocity is also discussed.

  14. Variations in atmospheric angular momentum

    NASA Technical Reports Server (NTRS)

    Rosen, R. D.; Salstein, D. A.

    1981-01-01

    Twice-daily values of the atmosphere's angular momentum about the polar axis during the five years from 1976 through 1980 are presented in graphs and a table. The compilation is based on a global data set, incorporating 90 percent of the mass of the atmosphere. The relationship between changes in the angular momentum of the atmosphere and changes in the length of day is described, as are the main sources of error in the data. The variability in angular momentum is revealed in a preliminary fashion by means of a spectral decomposition. The data presented should stimulate comparisons with other measures of the length of day and so provide a basis for greater understanding of Earth-atmosphere interactions.

  15. Gamma-neutrino angular correlations in muon capture.

    NASA Technical Reports Server (NTRS)

    Miller, G. H.; Kane, F. R.; Martin, P.; Welsh, R. E.; Eckhause, M.

    1972-01-01

    Using a high-resolution Ge(Li) spectrometer, it proved possible to observe several Doppler-broadened gamma-ray transitions in Al-28 excited by muon capture in Si-28. Several of these transitions are shown to be suitable for analysis in terms of angular correlations between the neutrino and a deexcitation nuclear gamma-ray. The observed transitions are interpreted in terms of gamma-neutrino correlation coefficients which are functions of the weak-interaction coupling constants.

  16. Automated Angular Momentum Recoupling Algebra

    NASA Astrophysics Data System (ADS)

    Williams, H. T.; Silbar, Richard R.

    1992-04-01

    We present a set of heuristic rules for algebraic solution of angular momentum recoupling problems. The general problem reduces to that of finding an optimal path from one binary tree (representing the angular momentum coupling scheme for the reduced matrix element) to another (representing the sub-integrals and spin sums to be done). The method lends itself to implementation on a microcomputer, and we have developed such an implementation using a dialect of LISP. We describe both how our code, called RACAH, works and how it appears to the user. We illustrate the use of RACAH for several transition and scattering amplitude matrix elements occurring in atomic, nuclear, and particle physics.

  17. Measuring Angular Size and Distance

    NSDL National Science Digital Library

    2012-08-03

    This is an activity about measuring angular size and understanding the solar and lunar proportions that result in solar eclipses. Learners will use triangles and proportions to create a shoebox eclipse simulator. They will then apply what they learn about angular size to predict the diameter and distance of one object that can be eclipsed by another. They will also complete three journal assignments to record observations and conceptual understanding. This activity derives from those demonstrated in the NASA CONNECT television series episode, titled Path of Totality.

  18. The Angular Momentum of Baryons and Dark Matter Halos Revisited

    NASA Technical Reports Server (NTRS)

    Kimm, Taysun; Devriendt, Julien; Slyz, Adrianne; Pichon, Christophe; Kassin, Susan A.; Dubois, Yohan

    2011-01-01

    Recent theoretical studies have shown that galaxies at high redshift are fed by cold, dense gas filaments, suggesting angular momentum transport by gas differs from that by dark matter. Revisiting this issue using high-resolution cosmological hydrodynamics simulations with adaptive-mesh refinement (AMR), we find that at the time of accretion, gas and dark matter do carry a similar amount of specific angular momentum, but that it is systematically higher than that of the dark matter halo as a whole. At high redshift, freshly accreted gas rapidly streams into the central region of the halo, directly depositing this large amount of angular momentum within a sphere of radius r = 0.1R(sub vir). In contrast, dark matter particles pass through the central region unscathed, and a fraction of them ends up populating the outer regions of the halo (r/R(sub vir) > 0.1), redistributing angular momentum in the process. As a result, large-scale motions of the cosmic web have to be considered as the origin of gas angular momentum rather than its virialised dark matter halo host. This generic result holds for halos of all masses at all redshifts, as radiative cooling ensures that a significant fraction of baryons remain trapped at the centre of the halos. Despite this injection of angular momentum enriched gas, we predict an amount for stellar discs which is in fair agreement with observations at z=0. This arises because the total specific angular momentum of the baryons (gas and stars) remains close to that of dark matter halos. Indeed, our simulations indicate that any differential loss of angular momentum amplitude between the two components is minor even though dark matter halos continuously lose between half and two-thirds of their specific angular momentum modulus as they evolve. In light of our results, a substantial revision of the standard theory of disc formation seems to be required. We propose a new scenario where gas efficiently carries the angular momentum generated by large-scale structure motions deep inside dark matter halos, redistributing it only in the vicinity of the disc.

  19. CUTS IN THE CCMPLEX ANGULAR MOMENTUM PLANE CUTS IN THE COMPLEX ANGULAR MOMENTUM PLANE

    E-print Network

    Boyer, Edmond

    CUTS IN THE CCMPLEX ANGULAR MOMENTUM PLANE CUTS IN THE COMPLEX ANGULAR MOMENTUM PLANE I.G. HALLIDAY is projected into angular momentum states where the left and right pairs have angular momentum and helicities Imperial College I have been asked to review the recent advances in the theory of cuts in the angular

  20. Energy and angular momentum transfer in the excitation of electron-hole pairs by slow dimers R. Diez Muin~o

    E-print Network

    Muiño, Ricardo Díez

    Energy and angular momentum transfer in the excitation of electron-hole pairs by slow dimers R. Di and angular momentum through electron-hole pair excitations for a slow dimer in an electron gas. We show approximation. We obtain the low-energy limit of the friction coeffi- cient and average angular momentum

  1. Angular momentum from tidal torques

    Microsoft Academic Search

    Joshua Barnes; George Efstathiou

    1987-01-01

    The authors describe results for the origin of angular momentum of bound objects in large cosmological N-body simulations. Three sets of models are analyzed: one with white-noise initial conditions and two in which the initial conditions have more power on large scales, as predicted in models with cold dark matter (CDM). Statistical analysis of large catalogs of objects shows that

  2. Unified Angular Momentum of Dyons

    E-print Network

    Shalini Dangwal; P. S. Bisht; O. P. S. Negi

    2006-08-22

    Unified quaternionic angular momentum for the fields of dyons and gravito-dyons has been developed and the commutation relations for dynamical variables are obtained in compact and consistent manner. Demonstrating the quaternion forms of unified fields of dyons (electromagnetic fields) and gravito-dyons (gravito-Heavisidian fields of linear gravity), corresponding quantum equations are reformulated in compact, simpler and manifestly covariant way.

  3. Olympic Wrestling and Angular Momentum.

    ERIC Educational Resources Information Center

    Carle, Mark

    1988-01-01

    Reported is the use of a wrestling photograph in a noncalculus introductory physics course. The photograph presents a maneuver that could serve as an example for a discussion on equilibrium, forces, torque, and angular motion. Provided are some qualitative thoughts as well as quantitative calculations. (YP)

  4. The lunar angular momentum problem

    NASA Technical Reports Server (NTRS)

    Weidenschilling, S. J.

    1984-01-01

    Formation of the Moon by classical Darwin-type fission of a rapidly spinning proto-Earth is discussed. The relationship of angular momentum to accretion disks is examined. The co-accretion scenario and Darwin-type fission are compared and evaluated.

  5. Angle-resolved x-ray imaging using a resolution-tunable double-crystal analyser

    NASA Astrophysics Data System (ADS)

    Hirano, K.

    2003-07-01

    A resolution-tunable double-crystal analyser was successfully applied, for the first time, to angle-resolved x-ray imaging. Tuning the resolution between 0.5'' and 2.3'' was done with small loss of peak intensity using a Si(220) double-crystal analyser. The angle-resolved images of a housefly were recorded on nuclear emulsion plates at various angular resolutions. Several methods to improve the angular resolution of the analyser are also proposed.

  6. Asteroid orbit fitting with radar and angular observations

    NASA Astrophysics Data System (ADS)

    Baturin, A. P.

    2013-12-01

    The asteroid orbit fitting problem using their radar and angular observations has been considered. The problem was solved in a standanrd way by means of minimization of weighted sum of squares of residuals. In the orbit fitting both kinds of radar observa-tions have been used: the observations of time delays and of Doppler frequency shifts. The weight for angular observations has been set the same for all of them and has been determined as inverse mean-square residual obtained in the orbit fitting using just angular observations. The weights of radar observations have been set as inverse squared errors of these observations published together with them in the Minor Planet Center electronical circulars (MPECs). For the orbit fitting some five asteroids have been taken from these circulars. The asteroids have been chosen fulfilling the requirement of more than six radar observations of them to be available. The asteroids are 1950 DA, 1999 RQ36, 2002 NY40, 2004 DC and 2005 EU2. Several orbit fittings for these aster-oids have been done: with just angular observations; with just radar observations; with both angular and radar observations. The obtained results are quite acceptable because in the last case the mean-square angular residuals are approximately equal to the same ones obtained in the fitting with just angular observations. As to radar observations mean-square residuals, the time delay residuals for three asteroids do not exceed 1 ?s, for two others ˜ 10 ?s and the Doppler shift residuals for three asteroids do not exceed 1 Hz, for two others ˜ 10 Hz. The motion equations included perturbations from 9 planets and the Moon using their ephemerides DE422. The numerical integration has been performed with Everhart 27-order method with variable step. All calculations have been exe-cuted to a 34-digit decimal precision (i.e. using 128-bit floating-point numbers). Further, the sizes of confidence ellipsoids of im-proved orbit parameters have been compared. It has been accepted that an indicator of ellipsoid size is a geometric mean of its six semi-axes. A comparison of sizes has shown that confidence ellipsoids obtained in orbit fitting with both angular and radar obser-vations are several times less than ellipsoids obtained with just angular observations.

  7. REMOVEALL BURRSAND SHARPEDGES ANGULAR TOL

    E-print Network

    Llope, William J.

    RHIC ± .02 ± .1 ± .005 .XX .X .XXX ± 1/ 2° ±1/ 64 REMOVEALL BURRSAND SHARPEDGES ANGULAR TOL MV2 MV3 Manual Valve PI1 PI2 PI3 Pressure Indicator (Dwyer 65030) Main Shutoff Valve (Asco EF8262G7) MSV1 gas pad PI4 PI5 PI6 FM1 FM2 FM3 Flowmeter (Teledyne HFC-202) Check Valve (Swagelok SS-4C-1/ 3) CV

  8. Paraxial Light Beams with Angular Momentum

    E-print Network

    A. Bekshaev; M. Soskin; M. Vasnetsov

    2008-01-15

    Fundamental and applied concepts concerning the ability of light beams to carry a certain mechanical angular momentum with respect to the propagation axis are reviewed and discussed. Following issues are included: Historical reference; Angular momentum of a paraxial beam and its constituents; Spin angular momentum and paradoxes associated with it; Orbital angular momentum; Circularly-spiral beams: examples and methods of generation; Orbital angular momentum and the intensity moments; Symmetry breakdown and decomposition of the orbital angular momentum; Mechanical models of the vortex light beams; Mechanical action of the beam angular momentum; Rotational Doppler effect, its manifestation in the image rotation; Spectrum of helical harmonics and associated problems; Non-collinear rotational Doppler effect; Properties of a beam forcedly rotating around its own axis. Research prospects and ways of practical utilization of optical beams with angular momentum.

  9. Orbital angular momentum in phase space

    E-print Network

    I. Rigas; L. L. Sanchez-Soto; A. B. Klimov; J. Rehacek; Z. Hradil

    2010-11-29

    A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.

  10. Achromatic orbital angular momentum generator

    NASA Astrophysics Data System (ADS)

    Bouchard, Frédéric; Mand, Harjaspreet; Mirhosseini, Mohammad; Karimi, Ebrahim; Boyd, Robert W.

    2014-12-01

    We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of two glued hollow axicons, is used to introduce a nonuniform rotation of polarization into a linearly polarized input beam. This device acts as a full spin-to-orbital angular momentum convertor. It functions by switching the helicity of the incoming beam?s polarization, and by conservation of total angular momentum thereby generates a well-defined value of OAM. Our device is broadband, since the phase shift due to total internal reflection is nearly independent of wavelength. We verify the broad-band behaviour by measuring the conversion efficiency of the device for three different wavelengths corresponding to the RGB colours, red, green and blue. An average conversion efficiency of 95% for these three different wavelengths is observed. This device may find applications in imaging from micro- to astronomical systems where a white vortex beam is needed.

  11. A test of galaxy evolutionary models via angular sizes

    NASA Technical Reports Server (NTRS)

    Im, Myungshin; Casertano, Stefano; Griffiths, Richard E.; Ratnatunga, Kavan U.; Tyson, J. Anthony

    1995-01-01

    The relationship between angular size, magnitude, and redshift of faint galaxies is explored as a potential tool to distinguish between galaxy evolutionary models. Different models, based on merging, mild luminosity evolution, and no evolution, lead to different predictions of the angular size distribution, redshift- size relation, and magnitude-size relation. The merging model predicts significantly smaller sizes for faint galaxies than the standard model, because of the requirement for more intrinsically small faint objects at high redshift. A dwarf-rich no-evolution model also predicts small sizes for faint galaxies. The mild luminosity evolution model predicts more luminous galaxies of large angular size at high redshift, as does a standard no-evolution model. Prefurbishment Hubble Space Telescope (HST) Medium Deep Survey observations of magnitudes and sizes of faint galaxies indicate an excess of small versus large faint galaxies, favoring the dwarf rich, no evolution model with respect to the merging model; the other two models are more discrepant with the data. While these results cannot yet rule out with certainty any of the proposed models, they demonstrate the potential of angular size to discriminate between models of galaxy evolution, especially with the high-resolution HST wide field/planetary camera-2 (WFPC2) data.

  12. Low angular momentum flow model of Sgr A* activity

    E-print Network

    B. Czerny; M. Moscibrodzka

    2008-08-21

    Sgr A* is the closest massive black hole and can be observed with the highest angular resolution. Nevertheless, our current understanding of the accretion process in this source is very poor. The inflow is almost certainly of low radiative efficiency and it is accompanied by a strong outflow and the flow is strongly variable but the details of the dynamics are unknown. Even the amount of angular momentum in the flow is an open question. Here we argue that low angular momentum scenario is better suited to explain the flow variability. We present a new hybrid model which describes such a flow and consists of an outer spherically symmetric Bondi flow and an inner axially symmetric flow described through MHD simulations. The assumed angular momentum of the matter is low, i.e. the corresponding circularization radius in the equatorial plane of the flow is just above the innermost stable circular orbit in pseudo-Newtonian potential. We compare the radiation spectrum from such a flow to the broad band observational data for Sgr A*.

  13. Angular Momentum Transport in Astrophysical Accretion Flows

    E-print Network

    Hammett, Greg

    Angular Momentum Transport in Astrophysical Accretion Flows Greg Hammett, Princeton Plasma Physics of matter onto a central object (generally w/ angular momentum) · Central to ­ Star & Planet Formation to Sgr A* #12;Outline · Accretion Disks: Basic Physical Picture · MHD of Disks: Angular Momentum

  14. Angular Momentum Decomposition for an Electron

    E-print Network

    Matthias Burkardt; Hikmat BC

    2008-12-09

    We calculate the orbital angular momentum of the `quark' in the scalar diquark model as well as that of the electron in QED (to order $\\alpha$). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.

  15. Angular Momentum Decomposition for an Electron

    SciTech Connect

    Burkardt, Matthias; BC, Hikmat

    2009-01-01

    We calculate the orbital angular momentum of the `quark' in the scalar diquark model as well as that of the electron in QED (to order $\\alpha$). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.

  16. High-resolution bottom-loss estimation using the ambient-noise vertical coherence function.

    PubMed

    Muzi, Lanfranco; Siderius, Martin; Quijano, Jorge E; Dosso, Stan E

    2015-01-01

    The seabed reflection loss (shortly "bottom loss") is an important quantity for predicting transmission loss in the ocean. A recent passive technique for estimating the bottom loss as a function of frequency and grazing angle exploits marine ambient noise (originating at the surface from breaking waves, wind, and rain) as an acoustic source. Conventional beamforming of the noise field at a vertical line array of hydrophones is a fundamental step in this technique, and the beamformer resolution in grazing angle affects the quality of the estimated bottom loss. Implementation of this technique with short arrays can be hindered by their inherently poor angular resolution. This paper presents a derivation of the bottom reflection coefficient from the ambient-noise spatial coherence function, and a technique based on this derivation for obtaining higher angular resolution bottom-loss estimates. The technique, which exploits the (approximate) spatial stationarity of the ambient-noise spatial coherence function, is demonstrated on both simulated and experimental data. PMID:25618076

  17. Wind measurement resolution for a scanning pencil beam scatterometer

    Microsoft Academic Search

    David G. Long

    1994-01-01

    The problem of determining the effective wind measurement resolution of a wind scatterometer is considered. Using simplifying assumptions and approximations, a simple linear model for wind retrieval is derived and related to the effective wind estimate resolution and the backscatter measurement resolution. This enables an analytic evaluation of the scatterometer wind measurement resolution. The effective wind resolution is shown to

  18. Accelerated rotation with orbital angular momentum modes

    NASA Astrophysics Data System (ADS)

    Schulze, Christian; Roux, Filippus S.; Dudley, Angela; Rop, Ronald; Duparré, Michael; Forbes, Andrew

    2015-04-01

    We introduce a class of light field that angularly accelerates during propagation. We show that the acceleration (deceleration) may be controlled by adjustment of a single parameter, and tuned continuously, down to no acceleration at all. As the angular acceleration takes place in a bounded space, the azimuthal degree of freedom, such fields accelerate periodically as they propagate. Notably, the amount of angular acceleration is not limited by paraxial considerations, may be tailored for large accelerations over arbitrarily long distances, and can be engineered independently of the beam's spatial extent. We discuss how such angularly accelerating light fields can maintain the conservation of angular momentum through an energy exchange mechanism across the field.

  19. Signature of HDM clustering at Planck angular scales

    E-print Network

    L. A. Popa; C. Burigana; N. Mandolesi

    2003-12-04

    We present the CMB anisotropy induced by the non-linear perturbations in the massive neutrino density associated to the non-linear gravitational clustering. We show that the non-linear time varying potential induced by the gravitational clustering process generates metric perturbations that affect the time evolution of the density fluctuations in all the components of the expanding Universe, leaving imprints on the CMB anisotropy power spectrum at subdegree angular scales. For a neutrino fraction in agreement with that indicated by the astroparticle and nuclear physics experiments and a cosmological accreting mass comparable with the mass of known clusters, we find that CMB anisotropy measurements with {\\sc Planck} angular resolution and sensitivity possibly combined to other precise cosmological observations will allow the detection of the dynamical, linear and non-linear effects of the neutrino gravitational clustering.

  20. Angular domain fluorescence imaging for small animal research

    NASA Astrophysics Data System (ADS)

    Vasefi, Fartash; Belton, Michelle; Kaminska, Bozena; Chapman, Glenn H.; Carson, Jeffrey J. L.

    2010-01-01

    We describe a novel macroscopic fluorescent imaging technique called angular domain fluorescence imaging (ADFI) applicable to the detection of fluorophores embedded in biological tissues. The method exploits the collimation detection capabilities of an angular filter array (AFA). The AFA uses the principle of acceptance angle filtration to extract minimally scattered photons emitted from fluorophores deep within tissue. Our goal was to develop an ADFI system for imaging near-infrared fluorescent markers for small animal imaging. According to the experimental results, the ADFI system offered higher resolution and contrast compared to a conventional lens and lens-pinhole fluorescent detection system. Furthermore, ADFI of a hairless mouse injected with a fluorescent bone marker revealed vertebral structural and morphometric data that correlated well with data derived from volumetric x-ray computed tomography images. The results suggested that ADFI is a useful technique for submillimeter mapping of the distribution of fluorescent biomarkers in small animals.

  1. Two-axis angular effector

    DOEpatents

    Vaughn, Mark R. (Albuquerque, NM); Robinett, III, Rush D. (Tijeras, NM); Phelan, John R. (Albuquerque, NM); Van Zuiden, Don M. (Albuquerque, NM)

    1997-01-21

    A new class of coplanar two-axis angular effectors. These effectors combine a two-axis rotational joint analogous to a Cardan joint with linear actuators in a manner to produce a wider range of rotational motion about both axes defined by the joint. This new class of effectors also allows design of robotic manipulators having very high strength and efficiency. These effectors are particularly suited for remote operation in unknown surroundings, because of their extraordinary versatility. An immediate application is to the problems which arise in nuclear waste remediation.

  2. Variable Distance Angular Symbology Reader

    NASA Technical Reports Server (NTRS)

    Schramm, Harry F., Jr. (Inventor); Corder, Eric L. (Inventor)

    2006-01-01

    A variable distance angular symbology, reader utilizes at least one light source to direct light through a beam splitter and onto a target. A target may be angled relative to the impinging light beam up to and maybe even greater than 45deg. A reflected beam from the target passes through the beam splitter and is preferably directed 90deg relative to the light source through a telecentric lens to a scanner which records an image of the target such as a direct part marking code.

  3. Fast Approximate Convex Decomposition 

    E-print Network

    Ghosh, Mukulika

    2012-10-19

    Approximate convex decomposition (ACD) is a technique that partitions an input object into "approximately convex" components. Decomposition into approximately convex pieces is both more efficient to compute than exact convex decomposition and can...

  4. Approximate Information Theory

    E-print Network

    Penny, Will

    Approximate Inference Will Penny Information Theory Information Entropy Kullback-Liebler Divergence Approximate Inference Will Penny 31st March 2011 #12;Approximate Inference Will Penny Information Theory Will Penny Information Theory Information Entropy Kullback-Liebler Divergence Gaussians Asymmetry

  5. Interpolation and Approximation Theory.

    ERIC Educational Resources Information Center

    Kaijser, Sten

    1991-01-01

    Introduced are the basic ideas of interpolation and approximation theory through a combination of theory and exercises written for extramural education at the university level. Topics treated are spline methods, Lagrange interpolation, trigonometric approximation, Fourier series, and polynomial approximation. (MDH)

  6. Measurement of polarization with the Degree Angular Scale Interferometer.

    PubMed

    Leitch, E M; Kovac, J M; Pryke, C; Carlstrom, J E; Halverson, N W; Holzapfel, W L; Dragovan, M; Reddall, B; Sandberg, E S

    Measurements of the cosmic microwave background (CMB) radiation can reveal with remarkable precision the conditions of the Universe when it was approximately 400,000 years old. The three most fundamental properties of the CMB are its frequency spectrum (which determines the temperature), and the fluctuations in both the temperature and polarization across a range of angular scales. The frequency spectrum has been well determined, and considerable progress has been made in measuring the power spectrum of the temperature fluctuations. But despite many efforts to measure the polarization, detection of this property of the CMB has hitherto been beyond the reach of even the most sensitive observations. Here we describe the Degree Angular Scale Interferometer (DASI), an array of radio telescopes, which for the past two years has conducted polarization-sensitive observations of the CMB from the Amundsen-Scott South Pole research station. PMID:12490940

  7. High resolution X-ray scattering measurements

    NASA Technical Reports Server (NTRS)

    Zombeck, M. V.; Braeuninger, H.; Ondrusch, A.; Predehl, P.

    1982-01-01

    The results of high angular resolution grazing incidence scattering measurements of highly polished, coated optical flats in the X-ray spectral range of 1.5 to 6.4 keV are reported. The interpretation of these results in terms of surface microtopography is presented and the implications for grazing incidence X-ray imaging are discussed.

  8. The SDSS galaxy angular two-point correlation function

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Brunner, R. J.; Dolence, J. C.

    2013-07-01

    We present the galaxy two-point angular correlation function for galaxies selected from the seventh data release of the Sloan Digital Sky Survey (SDSS). The galaxy sample was selected with r-band apparent magnitudes between 17 and 21, and we measure the correlation function for the full sample as well as for the four magnitude ranges: 17-18, 18-19, 19-20 and 20-21. We update the flag criteria to select a clean galaxy catalogue and detail specific tests that we perform to characterize systematic effects, including the effects of seeing, Galactic extinction and the overall survey uniformity. Notably, we find that optimally we can use observed regions with seeing <1.5 arcsec, and r-band extinction <0.13 mag, smaller than previously published results. Furthermore, we confirm that the uniformity of the SDSS photometry is minimally affected by the stripe geometry. We find that, overall, the two-point angular correlation function can be described by a power law, ?(?) = A??(1 - ?) with ? ? 1.72, over the range 0.005°-10°. We also find similar relationships for the four magnitude subsamples, but the amplitude within the same angular interval for the four subsamples is found to decrease with fainter magnitudes, in agreement with previous results. We find that the systematic signals are well below the galaxy angular correlation function for angles less than approximately 5°, which limits the modelling of galaxy angular correlations on larger scales. Finally, we present our custom, highly parallelized two-point correlation code that we used in this analysis.

  9. Angular sizes and luminosity evolution of faint galaxies

    NASA Astrophysics Data System (ADS)

    Roche, N.; Ratnatunga, K.; Griffiths, R. E.; Im, M.; Neuschaefer, L.

    1996-10-01

    We investigate the number counts and the V-I colour, angular size and axis ratio distributions of 5384 faint galaxies detected with the refurbished Hubble Space Telescope (HST) Wide Field Planetary Camera, to limits of I~=25 on a 27-field strip and I~=26 on a single deeper field. These results are compared with non-evolving and pure luminosity evolution (PLE) models, with a steep (alpha=-1.65) luminosity function for late-type galaxies. In these models, we have aimed to incorporate surface brightness selection effects, which can produce a significant bias against detection of higher redshift galaxies with larger angular sizes. We find no deficit of large-angular-size galaxies relative to our non-evolving model. At I<~22 there is a significant (approximately factor of 2) excess of moderately large (0.4<=r_hl<=1.5 arcsec at 22<=I<=24) galaxies with blue (V-I<=1.2) colours over our non-evolving model. The observed angular size and colour distributions are reasonably well-fitted by our PLE model, when detection thresholds appropriate to the data are included. These results appear to provide positive evidence that L~L* galaxies do brighten significantly (by ~1 mag) to z~1-2, increasing the numbers of blue, large-angular-size, high-redshift galaxies seen at I<~22, and that L* evolution, in addition to a steep luminosity function, is needed to explain the steep galaxy number counts. We also investigate faint galaxy axis ratios. At 20<=I<=24 the smaller galaxies tended to be more rounded than galaxies of large angular size, suggesting that a greater proportion are ellipticals. On going faintward, however, the axis ratio distribution of the smaller galaxies appears to shift towards that of a spiral-dominated population, as expected if later-type galaxies have a much steeper luminosity function than ellipticals. The axis ratio distribution of larger-angular-size galaxies remains consistent with a spiral-dominated population over the whole 20<=I<=25 range, suggesting that most of the evolving high-redshift galaxies on these fields are spirals and that the high-redshift ellipticals are significantly dimmed by dust extinction.

  10. Quantum Formulation of Fractional Orbital Angular Momentum

    E-print Network

    J. B. Goette; S. Franke-Arnold; R. Zambrini; Stephen M. Barnett

    2006-11-15

    The quantum theory of rotation angles (S. M. Barnett and D. T. Pegg, Phys. Rev. A, 41, 3427-3425 (1990)) is generalised to non-integer values of the orbital angular momentum. This requires the introduction of an additional parameter, the orientation of a phase discontinuity associated with fractional values of the orbital angular momentum. We apply our formalism to the propagation of light modes with fractional orbital angular momentum in the paraxial and non-paraxial regime.

  11. Quantum Formulation of Fractional Orbital Angular Momentum

    E-print Network

    Goette, J B; Franke-Arnold, S; Zambrini, R; Barnett, Stephen M.

    2006-01-01

    The quantum theory of rotation angles (S. M. Barnett and D. T. Pegg, Phys. Rev. A, 41, 3427-3425 (1990)) is generalised to non-integer values of the orbital angular momentum. This requires the introduction of an additional parameter, the orientation of a phase discontinuity associated with fractional values of the orbital angular momentum. We apply our formalism to the propagation of light modes with fractional orbital angular momentum in the paraxial and non-paraxial regime.

  12. Orbital angular momentum in phase space

    SciTech Connect

    Rigas, I. [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain); Sanchez-Soto, L.L., E-mail: lsanchez@fis.ucm.es [Departamento de Optica, Facultad de Fisica, Universidad Complutense, 28040 Madrid (Spain); Klimov, A.B. [Departamento de Fisica, Universidad de Guadalajara, 44420 Guadalajara, Jalisco (Mexico); Rehacek, J.; Hradil, Z. [Department of Optics, Palacky University, 17. Listopadu 12, 746 01 Olomouc (Czech Republic)

    2011-02-15

    Research Highlights: > We propose a comprehensive Weyl-Wigner formalism for the canonical pair angle-angular momentum. > We present a simple and useful toolkit for the practitioner. > We derive simple evolution equations in terms of a star product in the semiclassical limit. - Abstract: A comprehensive theory of the Weyl-Wigner formalism for the canonical pair angle-angular momentum is presented. Special attention is paid to the problems linked to rotational periodicity and angular-momentum discreteness.

  13. Anisotropy of the Cosmic Microwave Background Radiation on Large and Medium Angular Scales

    NASA Technical Reports Server (NTRS)

    Houghton, Anthony; Timbie, Peter

    1998-01-01

    This grant has supported work at Brown University on measurements of the 2.7 K Cosmic Microwave Background Radiation (CMB). The goal has been to characterize the spatial variations in the temperature of the CMB in order to understand the formation of large-scale structure in the universe. We have concurrently pursued two measurements using millimeter-wave telescopes carried aloft by scientific balloons. Both systems operate over a range of wavelengths, chosen to allow spectral removal of foreground sources such as the atmosphere, Galaxy, etc. The angular resolution of approx. 25 arcminutes is near the angular scale at which the most structure is predicted by current models to be visible in the CMB angular power spectrum. The main goal is to determine the angular scale of this structure; in turn we can infer the density parameter, Omega, for the universe as well as other cosmological parameters, such as the Hubble constant.

  14. High-resolution imaging at the SOAR telescope A. Tokovinin, R. Cantarutti, R. Tighe, P. Schurter, N. van der Bliek, M. Martinez, E.

    E-print Network

    Tokovinin, Andrei A.

    High-resolution imaging at the SOAR telescope A. Tokovinin, R. Cantarutti, R. Tighe, P. Schurter, N-baseline interfer- ometers, imaging and spectroscopy of faint sources is done today at the angular resolution by the visible-light adaptive optics system. We compare the angular resolution achieved by simple averaging of AO

  15. Angular sensitivity of vegetation indices derived from CHRIS\\/PROBA data

    Microsoft Academic Search

    J. Verrelst; M. E. Schaepman; B. Kötz; M. Kneubühler

    2008-01-01

    View angle effects present in spectral vegetation indices can either be regarded as an added source of uncertainty for variable retrieval or as a source of additional information, enhancing the variable retrieval; however, the magnitude of these angular effects remains for most indices unknown or unquantified. We use the ESA-mission CHRIS-PROBA (Compact High Resolution Imaging Spectrometer onboard the Project for

  16. Angular sensitivity analysis of vegetation indices derived from CHRIS\\/PROBA data

    Microsoft Academic Search

    J. Verrelst; M. E. Schaepman; B. Koetz; M. Kneubühler

    2008-01-01

    View angle effects present in spectral vegetation indices can either be regarded as an added source of uncertainty for variable retrieval or as a source of additional information, enhancing the variable retrieval; however, the magnitude of these angular effects remains for most indices unknown or unquantified. We use the ESA-mission CHRIS-PROBA (Compact High Resolution Imaging Spectrometer onboard the Project for

  17. Theory of angular dispersive imaging hard x-ray spectrographs

    E-print Network

    Shvyd'ko, Yuri

    2015-01-01

    A spectrograph is an optical instrument that disperses photons of different energies into distinct directions and space locations, and images photon spectra on a position-sensitive detector. Spectrographs consist of collimating, angular dispersive, and focusing optical elements. Bragg reflecting crystals arranged in an asymmetric scattering geometry are used as the dispersing elements. A ray-transfer matrix technique is applied to propagate x-rays through the optical elements. Several optical designs of hard x-ray spectrographs are proposed and their performance is analyzed. Spectrographs with an energy resolution of 0.1 meV and a spectral window of imaging up to a few tens of meVs are shown to be feasible for inelastic x-ray scattering (IXS) spectroscopy applications. In another example, a spectrograph with a 1-meV spectral resolution and 85-meV spectral window of imaging is considered for Cu K-edge resonant IXS (RIXS).

  18. A new approximation for atom-diatom rotational-relaxation cross sections

    Microsoft Academic Search

    Alan S. Dickinson

    2006-01-01

    A semiclassical approximation to the S matrix of the infinite-order-sudden approximation is introduced. This is employed to yield for the energy-transfer effective cross section a purely classical approximation, analogous to the Mason-Monchick approximation [J. Chem. Phys. 36, 1622 (1962)] for traditional collision integrals. Constraints on energy and on angular momentum transfer are included. Numerical evaluation of this new approximation can

  19. The angular power spectra of polarized Galactic synchrotron

    E-print Network

    M. Tucci; E. Carretti; S. Cecchini; R. Fabbri; M. Orsini; E. Pierpaoli

    2000-06-27

    We derive the angular power spectra of intensity and polarization of Galactic synchrotron emission in the range 36 < l < 10^3 from the Parkes survey mapping the southern Galactic plane at 2.4 GHz. The polarization spectra of both electric and magnetic parity up to l \\simeq 10^3 are approximated very well by power laws with slope coefficients \\simeq 1.4, quite different from the CMB spectra. We show that no problem should arise from Galactic synchrotron for measurements of CMB polarization in the cosmological window.

  20. High resolution image formation from low resolution frames using Delaunay triangulation

    Microsoft Academic Search

    Surapong Lertrattanapanich; Nirmal K. Bose

    2002-01-01

    An algorithm based on spatial tessellation and approximation of each triangle patch in the Delaunay (1934) triangulation (with smoothness constraints) by a bivariate polynomial is advanced to construct a high resolution (HR) high quality image from a set of low resolution (LR) frames. The high resolution algorithm is accompanied by a site-insertion algorithm for update of the initial HR image

  1. Study of the mode of angular velocity damping for a spacecraft at non-standard situation

    NASA Astrophysics Data System (ADS)

    Davydov, A. A.; Sazonov, V. V.

    2012-07-01

    Non-standard situation on a spacecraft (Earth's satellite) is considered, when there are no measurements of the spacecraft's angular velocity component relative to one of its body axes. Angular velocity measurements are used in controlling spacecraft's attitude motion by means of flywheels. The arising problem is to study the operation of standard control algorithms in the absence of some necessary measurements. In this work this problem is solved for the algorithm ensuring the damping of spacecraft's angular velocity. Such a damping is shown to be possible not for all initial conditions of motion. In the general case one of two possible final modes is realized, each described by stable steady-state solutions of the equations of motion. In one of them, the spacecraft's angular velocity component relative to the axis, for which the measurements are absent, is nonzero. The estimates of the regions of attraction are obtained for these steady-state solutions by numerical calculations. A simple technique is suggested that allows one to eliminate the initial conditions of the angular velocity damping mode from the attraction region of an undesirable solution. Several realizations of this mode that have taken place are reconstructed. This reconstruction was carried out using approximations of telemetry values of the angular velocity components and the total angular momentum of flywheels, obtained at the non-standard situation, by solutions of the equations of spacecraft's rotational motion.

  2. Models of Angular Momentum Input to a Circumterrestrial Swarm from Encounters with Heliocentric Planetesimals

    NASA Technical Reports Server (NTRS)

    Davis, D. R.; Greenberg, R.; Hebert, F.

    1985-01-01

    Models of lunar origin in which the Moon accretes in orbit about the Earth from material approaching the Earth from heliocentric orbits must overcome a fundamental problem: the approach orbits of such material would be, in the simplest approximation, equally likely to be prograde or retrograde about the Earth, with the result that accretion of such material adds mass but not angular momentum to circumterrestrial satellites. Satellite orbits would then decay due to the resulting drag, ultimately impacting onto the Earth. One possibility for adding both material and angular momentum to Earth orbit is investigated: imbalance in the delivered angular momentum between pro and retrograde Earth passing orbits which arises from the three body dynamics of planetesimals approaching the Earth from heliocentric space. In order to study angular momentum delivery to circumterrestrial satellites, the near Earth velocities were numerically computed as a function of distance from the Earth for a large array of orbits systematically spanning heliocentric phase space.

  3. Angular Momentum Operators from Quantized SO(3)

    E-print Network

    Ahmad Adel Abutaleb

    2015-04-08

    In this paper, we derive the form of the angular momentum matrices and angular momentum operators in the case of quantized rotations. We find an indication of the need to change all quantum mechanical operators at very small scale (High Energy level) if we assume a quantized nature of the Spacetime.

  4. Angular momentum control in coordinated Victor Zordan

    E-print Network

    Zordan, Victor

    in computer animation, biomechanics, and robotics have begun to explore the ability to produce whole-body control over whole-body rotation. With such compelling evidence and findings in biomechanics of the role of angular momentum in human movement to date. They postulate that whole-body (spin) angular

  5. Angular-Rate Estimation Using Quaternion Measurements

    NASA Technical Reports Server (NTRS)

    Azor, Ruth; Bar-Itzhack, Y.; Deutschmann, Julie K.; Harman, Richard R.

    1998-01-01

    In most spacecraft (SC) there is a need to know the SC angular rate. Precise angular rate is required for attitude determination, and a coarse rate is needed for attitude control damping. Classically, angular rate information is obtained from gyro measurements. These days, there is a tendency to build smaller, lighter and cheaper SC, therefore the inclination now is to do away with gyros and use other means and methods to determine the angular rate. The latter is also needed even in gyro equipped satellites when performing high rate maneuvers whose angular-rate is out of range of the on board gyros or in case of gyro failure. There are several ways to obtain the angular rate in a gyro-less SC. When the attitude is known, one can differentiate the attitude in whatever parameters it is given and use the kinematics equation that connects the derivative of the attitude with the satellite angular-rate and compute the latter. Since SC usually utilize vector measurements for attitude determination, the differentiation of the attitude introduces a considerable noise component in the computed angular-rate vector.

  6. Optical angular momentum in periodic arrays

    Microsoft Academic Search

    R. Zambrini; M. Vasnetsov; M. Dennis; J. Courtial

    2005-01-01

    This paper studies the optical angular momentum in periodic arrays. This work shows a gray-scale representation of the phase cross-section of a periodic array of optical vortices. The phase gradient gives rise to transverse linear momentum, which in turn leads to a nonvanishing angular momentum density.

  7. Quantum formulation of fractional orbital angular momentum

    Microsoft Academic Search

    J. B. Götte; S. Franke-Arnold; R. Zambrini; Stephen M. Barnett

    2007-01-01

    The quantum theory of rotation angles (S. M. Barnett and D. T. Pegg, Phys. Rev. A, 41, 3427-3425 (1990)) is generalised to non-integer values of the orbital angular momentum. This requires the introduction of an additional parameter, the orientation of a phase discontinuity associated with fractional values of the orbital angular momentum. We apply our formalism to the propagation of

  8. Angular minimum uncertainty states with large uncertainties

    Microsoft Academic Search

    Jörg B Götte; Paul M. Radmore; Roberta Zambrini; Stephen M. Barnett

    2006-01-01

    The uncertainty relation for angle and angular momentum has a lower bound which depends on the form of the state. Surprisingly, this lower bound can be very large. We derive the states which have the lowest possible uncertainty product for a given uncertainty in the angle or in the angular momentum. We show that, if the given angle uncertainty is

  9. Angular momenta of modeled ocean gyres

    Microsoft Academic Search

    Greg Holloway; Peter Rhines

    1991-01-01

    Total angular momentum of fluid within an ocean basin consists of a part due to center of mass of the fluid rotating about Earth's axis and a part due to relative motion within the basin. In rotating planar geometry (f plane) the relative angular momentum due to motion within a basin can be expressed as an integral of mass transport

  10. Specific Angular Momentum of Extrasolar Planetary Systems

    E-print Network

    John C. Armstrong; Shane L. Larson; Rhett R. Zollinger

    2011-09-02

    As the number of known planetary systems increases, the ability to follow-up and characterize the extent of any system becomes limited. This paper considers the use of specific angular momentum as a metric to prioritize future observations. We analyze 431 planets in 367 known extrasolar planetary systems from Butler et al. (2006) (including updates to their online catalog, current to April, 2011) and estimate each system's orbital angular momentum. The range of partition- ing of specific angular momentum in these systems is found to be large, spanning several orders of magnitude. The analysis shows that multi-planet systems tend to have the highest values of specific angular momentum normalized against the planetary masses. This suggests that in high angular momentum systems, the dominant contributors have already been discovered, and that single-planet sys- tems with low observed angular momentum may be the most likely candidates for additional undiscovered companions compared to their high angular momentum, single-planet counterparts. The multi-planet system, GJ 581, is considered as a historical case study to demonstrate the concept, examining how the specific angular momentum of the know planetary system evolved with each discovery.

  11. Orbital angular momentum in the nucleon

    SciTech Connect

    Garvey, Gerald T. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2010-05-15

    Analysis of the measured value of the integrated d-bar-u-bar asymmetry (I{sub fas} = 0.147 +- 0.027) in the nucleon show it to arise from nucleon fluctuations into baryon plus pion. Requiring angular momentum conservation in these fluctuations shows the associated orbital angular momentum is equal to the value of the flavor asymmetry.

  12. Do springboard divers violate angular momentum conservation?

    Microsoft Academic Search

    Cliff Frohlich

    1979-01-01

    No. However, divers and trampolinists can perform somersaults and twists even though they have zero angular momentum at all times during the stunt. Also, if a diver is somersaulting in space and possesses angular momentum only about his somersaulting axis, he can make a single discrete change in the position of his arms which initiates continuous twisting motion even in

  13. ALMA Observations of Asteroid 3 Juno at 60 Kilometer Resolution

    E-print Network

    Partnership, ALMA; Kneissl, R; Moullet, A; Brogan, C L; Fomalont, E B; Vlahakis, C; Asaki, Y; Barkats, D; Dent, W R F; Hills, R; Hirota, A; Hodge, J A; Impellizzeri, C M V; Liuzzo, E; Lucas, R; Marcelino, N; Matsushita, S; Nakanishi, K; Perez, L M; Phillips, N; Richards, A M S; Toledo, I; Aladro, R; Broguiere, D; Cortes, J R; Cortes, P C; Dhawan, V; Espada, D; Galarza, F; Garcia-Appadoo, D; Guzman-Ramirez, L; Hales, A S; Humphreys, E M; Jung, T; Kameno, S; Laing, R A; Leon, S; Marconi, G; Nikolic, B; Nyman, L -A; Radiszcz, M; Remijan, A; Rodon, J A; Sawada, T; Takahashi, S; Tilanus, R P J; Vilaro, B Vila; Watson, L C; Wiklind, T; de Gregorio, I; Di Francesco, J; Mangum, J; Francke, H; Gallardo, J; Garcia, J; Gonzalez, S; Hill, T; Kaminski, T; Kurono, Y; Lopez, C; Morales, F; Plarre, K; Randall, S; van kempen, T; Videla, L; Villard, E; Andreani, P; Hibbard, J E; Tatematsu, K

    2015-01-01

    We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum images of the asteroid 3 Juno obtained with an angular resolution of 0.042 arcseconds (60 km at 1.97 AU). The data were obtained over a single 4.4 hr interval, which covers 60% of the 7.2 hr rotation period, approximately centered on local transit. A sequence of ten consecutive images reveals continuous changes in the asteroid's profile and apparent shape, in good agreement with the sky projection of the three-dimensional model of the Database of Asteroid Models from Inversion Techniques. We measure a geometric mean diameter of 259pm4 km, in good agreement with past estimates from a variety of techniques and wavelengths. Due to the viewing angle and inclination of the rotational pole, the southern hemisphere dominates all of the images. The median peak brightness temperature is 215pm13 K, while the median over the whole surface is 197pm15 K. With the unprecedented resolution of ALMA, we find that the brightness temperature varies ...

  14. Wave function for spontaneous parametric down-conversion with orbital angular momentum

    SciTech Connect

    Barbosa, Geraldo A. [Department of Electrical Engineering and Computer Science, Northwestern University, 2145 N. Sheridan Road, Evanston, Illinois 60208-3118 (United States)

    2009-12-15

    Several wave-function approximations describing spontaneous parametric down-conversion can be found in the literature. Basically all cases are derived from the standard Hamiltonian for parametric down-conversion. Most frequently, particular cases describing collinear or paraxial approximations are described. This work presents a wave function in compact form, valid for all cases of single photon-pair conversion (Type I or Type II), for all angles allowed by the phase-matching conditions and for all orbital angular momentum values l. Examples are given of coincidence structures to be expected for signal and idler photons. Partial transfer of orbital angular momentum from the pump laser to the photon pair is discussed. Some hypothesis for the decay channels of the nontransferred part of the orbital angular momentum is made.

  15. Neutron yields and angular distributions produced in antiproton annihilation at rest in uranium

    SciTech Connect

    Chen, B.; Armstrong, T.A.; Lewis, R.A.; Newton, R.; Smith, G.A. (Laboratory for Elementary Particle Science, Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)); Bocquet, J.P.; Malek, F. (Institut des Sciences Nucleaires de Grenoble, 53 Avenue des Martyrs, 38026 Grenoble CEDEX (France)); Nifenecker, H. (Institut des Sciences Nucleaires de Grenoble CEDEX, 53 Avenue des Martyrs, 38026 Grenoble CEDEX (France) DRFMC/LIH Centre d'Etudes Nucleaires de Grenoble, Boite Postale 85X, 38041 Grenoble CEDEX (France)); Maurel, M.; Monnand, E.; Perrin, P.; Ristori, C. (DRFMC, Centre d'Etudes Nucleaires de Grenoble, Boite Postale 85X, 38041 Grenoble CEDEX (France)); Ericsson, G.; Johansson, T.; Tibell, G. (Department of Radiation Sciences, P.O. Box 535, S-75121 Uppsala (Sweden)); Rey-Campagnolle, M. (Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, Institut National de Physique Nucleaire et de Physique des Particules, Centr

    1992-05-01

    Measurements of neutron yields and their angular distributions in coincidence with fission fragments produced in antiproton annihilation at rest in a natural uranium target have been carried out Low Energy Antiproton Ring (LEAR) at CERN. A total of 16.3{plus minus}0.9 neutrons per annihilation have been found, distributed among direct knockout (27%), evaporation (21%), and fission (52%) processes. Angular distributions show that neutrons below approximately 5 MeV result entirely from moving fission fragments, and above approximately 12 MeV entirely from the excited, prescission nucleus. An estimate of the angular momentum of the excited fission fragment gives {similar to}13{h bar}. We are able to account for all baryons produced in annihilation, including neutrons from this experiment and light charged nuclei found in another LEAR experiment, to within 4.5{plus minus}2.5 of the initial 237 units in the initial state.

  16. Neutron yields and angular distributions produced in antiproton annihilation at rest in uranium

    SciTech Connect

    B. Chen; T. A. Armstrong; R. A. Lewis; R. Newton; G. A. Smith; J. P. Bocquet; F. Malek; H. Nifenecker; M. Maurel; E. Monn; P. Perrin; C. Ristori; G. Ericsson; T. Johansson; G. Tibell; M. Rey-Campagnolle; S. Polikanov; T. Krogulski; J. Mougey

    1992-05-01

    Measurements of neutron yields and their angular distributions in coincidence with fission fragments produced in antiproton annihilation at rest in a natural uranium target have been carried out Low Energy Antiproton Ring (LEAR) at CERN. A total of 16.3±0.9 neutrons per annihilation have been found, distributed among direct knockout (27%), evaporation (21%), and fission (52%) processes. Angular distributions show that neutrons below approximately 5 MeV result entirely from moving fission fragments, and above approximately 12 MeV entirely from the excited, prescission nucleus. An estimate of the angular momentum of the excited fission fragment gives ?13?. We are able to account for all baryons produced in annihilation, including neutrons from this experiment and light charged nuclei found in another LEAR experiment, to within 4.5±2.5 of the initial 237 units in the initial state.

  17. Molecular collisions 21: Semiclassical approximation to atom-symmetric top rotational excitation

    NASA Technical Reports Server (NTRS)

    Russell, D.; Curtiss, C. F.

    1973-01-01

    A distorted wave approximation to the T matrix for atom-symmetric top scattering was developed. The approximation is correct to first order in the part of the interaction potential responsible for transitions in the component of rotational angular momentum along the symmetry axis of the top. A semiclassical expression for this T matrix is derived by assuming large values of orbital and rotational angular momentum quantum numbers.

  18. HIERARCHICAL GEOMETRIC APPROXIMATIONS

    E-print Network

    North Carolina at Chapel Hill, University of

    HIERARCHICAL GEOMETRIC APPROXIMATIONS TR-050 1994 Amitabh Varshney Department of Computer Science;HIERARCHICAL GEOMETRIC APPROXIMATIONS by Amitabh Varshney A Dissertation submitted to the faculty Advisor Reader Reader Reader #12;@1994 Amitabh Varshney ALL RIGHTS RESERVED #12;AMITABH VARSHNEY

  19. Approximate flavor symmetries

    SciTech Connect

    Rasin, A.

    1994-04-01

    We discuss the idea of approximate flavor symmetries. Relations between approximate flavor symmetries and natural flavor conservation and democracy models is explored. Implications for neutrino physics are also discussed.

  20. Angular correlations and missing energy spectrum in quasifree electron scattering

    SciTech Connect

    Natarajan, R.K.; Arunachalam, N.; Devanathan, V.

    1984-09-01

    The angular correlations and missing energy spectrum in quasifree electron scattering are studied in the unfactorized distorted wave impulse approximation. The present approach, in the nonrelativistic description, effectively includes the finer aspects of the process, namely the off-energy-shell effect and the spin-orbit coupling, which are neglected or approximated in the usual factorization methods. A comparative study between the factorized and unfactorized methods reveals that the unfactorized cross section not only accounts for the absolute value but also a possible asymmetry in its distribution. The study of the off-shell influence on spherical and nonspherical nuclei indicates that the off-shell effect is to increase with the increase of nuclear deformation.

  1. Electron angular distributions above the dayside auroral oval

    NASA Technical Reports Server (NTRS)

    Craven, J. D.; Frank, L. A.

    1975-01-01

    An electrostatic analyzer was employed on the Ariel 4 satellite to determine pitch angle distributions of electron intensities over the dayside auroral oval. Two major precipitation zones were encountered: an equatorward zone of broad spectra with intensities of approximately 1000 electrons/(sq cm-sec-sr-eV) and a poleward zone, the polar cusp, with intensities typical of those of the magnetosheath. Angular distributions within the equatorward zone are generally isotropic outside of the atmospheric backscatter cone. The precipitation mechanism appears to be pitch angle scattering near the distant magnetic equator. In contrast, pitch angle distributions within the polar cusp are often found to be strongly field aligned with intensities within the atmospheric loss cone greater by factors of approximately 10 than the mirroring intensities. These distributions are qualititatively similar to those for the inverted V precipitation events at later local times, and probably share a common acceleration mechanism with the inverted V phenomenon.

  2. A polarization-sensitive light field imager for multi-channel angular spectroscopy of light scattering in biological tissues

    PubMed Central

    Lu, Rongwen; Zhang, Qiuxiang; Zhi, Yanan

    2015-01-01

    Background Angular spectroscopy of light scattering can be used for quantitative analysis of cellular and subcellular properties, and thus promises a noninvasive methodology for in vivo assessment cellular integrity to complement in vitro histological examination. Spatial information is essential for accurate identification of localized abnormalities. However, conventional angular spectroscopy systems only provide single-channel measurement, which suffers from poor spatial resolution or requires time-consuming scanning over extended area. The purpose of this study was to develop a multi-channel angular spectroscopy for light field imaging in biological tissues. Materials and methods A microlens array (MLA) (8×8) based light field imager for 64-channel angular spectroscopy was developed. A pair of crossed polarizers was employed for polarization-sensitive recording to enable quantitative measurement at high signal specificity and sensitivity. The polarization-sensitive light field imager enables rapid measurement of multiple sampling volumes simultaneously at 18 ?m spatial-resolution and 3° angular-resolution. Comparative light field imaging and electrophysiological examination of freshly isolated and physiologically deteriorated lobster leg nerves have been conducted. Results Two-dimensional (2D) polarization-sensitive scattering patterns of the fresh nerves were highly elliptical, while they gradually lost the ellipticity and became rotationally symmetric (i.e., circular) as the nerves physiologically deteriorated due to repeated electrical stimulations. Characterized parameters, i.e., the ellipticity and the scattering intensity, rendered spatially various characteristics such as different values and deteriorating rates. Conclusions The polarization-sensitive light field imager is able to provide multi-channel angular spectroscopy of light scattering with both spatial and angular resolutions. The light scattering properties of nerves are highly dependent on the orientation of nerves and their physiological status. Further development of polarization-sensitive multi-channel angular spectroscopy may promise a methodology for rapid and reliable identification of localized abnormalities in biological tissues. PMID:25694947

  3. Analytical and numerical studies of angular correlation function of waves scattered from randomly distributed cylinders

    Microsoft Academic Search

    Yasuo Kuga; Guifu Zhang; Ji-Hae Yea; Akira Ishimaru

    1998-01-01

    The analytical solution for the angular correlation function of scattered waves from randomly distributed infinitely long cylinders is obtained using the second-order approximation with a modified attenuation coefficient. The approach is based on the coherent summation of the scattered waves which preserves the interference effects such as backscattering enhancement. The modification of the transport attenuation coefficient includes the contribution due

  4. Radiation reaction and angular momentum loss in small angle gravitational scattering

    Microsoft Academic Search

    Thibaut Damour; Nathalie Deruelle

    1981-01-01

    Starting from the Poincaré invariant post-linear approximation of general relativity, we present newtonian-like equations of motion for two slowly moving point masses. They include radiation reaction forces and imply a net mechanical angular momentum loss which agrees with the quadrupole formula in the small angle scattering limit.

  5. Quasicrystals and crystalline approximants

    Microsoft Academic Search

    A. I. Goldman; R. F. Kelton

    1993-01-01

    Over the past seven years, many examples of periodic crystals closely related to quasicrystalline alloys have been discovered. These crystals have been termed approximants, since the arrangements of atoms within their unit cells closely approximate the local atomic structures in quasicrystals. This colloquium focuses on these approximant structures, their description, and their relationship to quasicrystals.

  6. Approximate solution in gasdynamics

    NASA Technical Reports Server (NTRS)

    Sirovich, L.; Chong, T. H.

    1980-01-01

    One-dimensional unsteady gasdynamics is considered. An approximation based mainly on the interaction of simple and entropy waves is adopted. A discussion supporting this approximation, based in part on shock expansion theory, is given. By the use of certain transformations the approximation leads to solution in terms of quadratures. Excellent agreement with exact numerical results is obtained over a wide range of cases.

  7. High-resolution electron microscope

    NASA Technical Reports Server (NTRS)

    Nathan, R.

    1977-01-01

    Employing scanning transmission electron microscope as interferometer, relative phases of diffraction maximums can be determined by analysis of dark field images. Synthetic aperture technique and Fourier-transform computer processing of amplitude and phase information provide high resolution images at approximately one angstrom.

  8. On the angular momentum of a system of quantum particles

    E-print Network

    Paris-Sud XI, Université de

    On the angular momentum of a system of quantum particles O. Chavoya-Aceves 5610 North 78th Dr, Glendale, AZ USA chavoyao@gmail.com October 3, 2013 Abstract The properties of angular momentum and its of angular momentum of a quantum system of particles into orbital angular momentum plus intrinsic angular

  9. Angular momentum conservation for uniformly expanding flows

    E-print Network

    Sean A. Hayward

    2006-11-04

    Angular momentum has recently been defined as a surface integral involving an axial vector and a twist 1-form, which measures the twisting around of space-time due to a rotating mass. The axial vector is chosen to be a transverse, divergence-free, coordinate vector, which is compatible with any initial choice of axis and integral curves. Then a conservation equation expresses rate of change of angular momentum along a uniformly expanding flow as a surface integral of angular momentum densities, with the same form as the standard equation for an axial Killing vector, apart from the inclusion of an effective energy tensor for gravitational radiation.

  10. Analytic treatment of resolution precision in electronically collimated SPECT imaging involving multiple-interaction gamma rays

    Microsoft Academic Search

    J. W. Durkee Jr.; P. P. Antich; E. N. Tsyganov; A. Constantinescu; P. V. Kulkarni; B. J. Smith; G. M. Arbique; M. A. Lewis; T. Nguyen; A. Raheja; G. Thambi; R. W. Parkey

    1998-01-01

    The widely applied single-interaction analytic expression characterizing the energy resolution component of the angular resolution precision for an electronically collimated point source is extended to include multiple-interaction Compton scatter sequences as well as sequences terminated by photoelectric absorption. The analytic formulation is developed using the statistical variance of the mean for components comprising composite, multivariate resolution precision estimators. It is

  11. Integrable ultra-compact, high-resolution, real-time MEMS LADAR for the individual soldier

    Microsoft Academic Search

    James P. Siepmann; Adam Rybaltowski

    2005-01-01

    Laser radar (LADAR) has many advantages over other methods of target detection and analysis, both in combat and commercial applications. Because it uses a shorter wavelength than microwave radar and has significantly greater angular resolution, it is capable of a greater degree of accuracy and more precise target resolution to a level that allows for high-resolution image acquisition. The development

  12. Motionless system to measure relative angular emission intensity of decaying or modulated light emitting diodes.

    PubMed

    Radziwon, M; Hernandez-Sosa, G; Lackner, C; Sitter, H; Simbrunner, C

    2014-10-01

    In this paper, a measurement system is presented which enables fast and accurate determination of the relative angular emission intensity of light emitting devices, taking into account their specific features such as low light output, narrow spectral distribution, high spatial luminous intensity ratios, and small dimensions. Application of logarithmic sensors allows for fast measurement of relative emission by simple analog circuitry, while locating 18 of them on a fixed ring around the emitter allows a motionless measurement system. As a result, the proposed system can determine the relative angular emission in less than 100 ms with a resolution of 5° for symmetric emitters. PMID:25362367

  13. Variational Posterior Distribution Approximation in Bayesian Super Resolution

    E-print Network

    Granada, Universidad de

    of Multispectral Images Rafael Molina a,,1 , Miguel Vega b,1 , Javier Mateos a,1 , Aggelos K. Katsaggelos c a. Email addresses: rms@decsai.ugr.es (Rafael Molina), mvega@ugr.es (Miguel Vega), jmd for the capture of a multispectral image with six bands (three bands on the visible spectrum plus three bands

  14. Goal-based angular adaptivity applied to a wavelet-based discretisation of the neutral particle transport equation

    NASA Astrophysics Data System (ADS)

    Goffin, Mark A.; Buchan, Andrew G.; Dargaville, Steven; Pain, Christopher C.; Smith, Paul N.; Smedley-Stevenson, Richard P.

    2015-01-01

    A method for applying goal-based adaptive methods to the angular resolution of the neutral particle transport equation is presented. The methods are applied to an octahedral wavelet discretisation of the spherical angular domain which allows for anisotropic resolution. The angular resolution is adapted across both the spatial and energy dimensions. The spatial domain is discretised using an inner-element sub-grid scale finite element method. The goal-based adaptive methods optimise the angular discretisation to minimise the error in a specific functional of the solution. The goal-based error estimators require the solution of an adjoint system to determine the importance to the specified functional. The error estimators and the novel methods to calculate them are described. Several examples are presented to demonstrate the effectiveness of the methods. It is shown that the methods can significantly reduce the number of unknowns and computational time required to obtain a given error. The novelty of the work is the use of goal-based adaptive methods to obtain anisotropic resolution in the angular domain for solving the transport equation.

  15. Angular momentum generation in cold gravitational collapse

    E-print Network

    Benhaiem, D; Labini, F Sylos; Worrakitpoonpon, T

    2015-01-01

    During the violent relaxation of a self-gravitating system a significant fraction of its mass may be ejected. If the time varying gravitational field also breaks spherical symmetry this mass can potentially carry angular momentum. Thus starting initial configurations with zero angular momentum can in principle lead to a bound virialized system with non-zero angular momentum. We explore here, using numerical simulations, how much angular momentum can be generated in a virialized structure in this way, starting from configurations of cold particles which are very close to spherically symmetric. For initial configurations in which spherical symmetry is broken only by the Poissonian fluctuations associated with the finite particle number $N$, with $N$ in range $10^3$ to $10^5$, we find that the relaxed structures have standard "spin" parameters $\\lambda \\sim 10^{-3}$, and decreasing slowly with $N$. For slightly ellipsoidal initial conditions, in which the finite-$N$ fluctuations break the residual reflection sym...

  16. Angular dependence of DRAM upset susceptibility

    NASA Technical Reports Server (NTRS)

    Guertin, S. M.; Swift, G. M.; Edmonds, L. D.

    2000-01-01

    Heavy ion irradiations of two types of commercial DRAMs reveal unexpected angular responses. One device's cross section varied by two orders of magnitude with azimuthal angle. Accurate prediction of space rates requires accommodating this effect.

  17. Angular correlations in neutron beta decay

    Microsoft Academic Search

    T. J. Bowles

    1993-01-01

    A new generation experiment searching for time reversal violation in polarized neutron beta decay is discussed, including theoretical description of polarized beta decay; measurement of angular correlations; theoretical implications; and future possibilities.

  18. Angular scattering of sound from solid particles in turbulent suspension.

    PubMed

    Moore, Stephanie A; Hay, Alex E

    2009-09-01

    Sound scattering by solid particles suspended in a turbulent jet is investigated. Measurements of the scattered amplitude were made in a bistatic geometry at frequencies between 1.5 and 4.0 MHz, and at scattering angles from 95 degrees to 165 degrees relative to the forward direction. Two types of particle were used: nearly spherical lead-glass beads and aspherical natural sand grains. For each particle type, experiments were carried out using approximately 200 and approximately 500 microm median diameter grain sizes, corresponding to 0.7 < or approximately ka < or approximately 4. The sphericity of the sand grains, defined as the ratio of projected perimeter size to projected area size, was 1.08. The lead-glass bead results are consistent with an elastic sphere model. A rigid movable sphere model provides the best fit to the sand data, and the best-fit diameter is within 4% of the equivalent volume size. However, the scattering pattern for sand is systematically smoother than predicted: that is, the undulations in the angular scattering pattern predicted by spherical scatterer theory are present, but muted. This observed departure from spherical scatterer theory is attributed to disruption of the interference among creeping waves by the irregular surfaces of natural sand grains. PMID:19739717

  19. Entanglement of polarization and orbital angular momentum

    NASA Astrophysics Data System (ADS)

    Bhatti, D.; von Zanthier, J.; Agarwal, G. S.

    2015-06-01

    We investigate two-photon entangled states using two important degrees of freedom of the electromagnetic field, namely orbital angular momentum (OAM) and spin angular momentum. For photons propagating in the same direction we apply the idea of entanglement duality and develop schemes to do entanglement sorting based on either OAM or polarization. In each case the entanglement is tested using appropriate witnesses. We finally present generalizations of these ideas to three- and four-photon entangled states.

  20. Angular Momentum Operators from Quantized SO(3)

    E-print Network

    Abutaleb, Ahmad Adel

    2015-01-01

    In this paper, we derive the form of the Angular Momentum Matrices and Angular Momentum Operators in the case of Quantized Rotations. We find an indication of the need to change all quantum mechanical operators at very small scale (High Energy level) if we assume a quantized nature of the Spacetime. Maybe the main purpose of this paper is to introduce the importance of using a branch of Mathematics called Time Scale calculus in Physical applications.

  1. Quantum formulation of fractional orbital angular momentum

    Microsoft Academic Search

    J. B. GÖTTE; S. Franke-Arnold; R. Zambrini; Stephen M. Barnett

    2007-01-01

    The quantum theory of rotation angles [S.M. Barnett and D.T. Pegg, Phys. Rev. A 41 3427 (1990)] is generalized to non-integer values of the orbital angular momentum. This requires the introduction of an additional parameter, the orientation of a phase discontinuity associated with fractional values of the orbital angular momentum. We apply our formalism to the propagation of light modes

  2. Angular minimum uncertainty states with large uncertainties

    E-print Network

    Goette, J B; Radmore, P M; Zambrini, R; Barnett, Stephen M.; Goette, Joerg B.; Radmore, Paul M.; Zambrini, Roberta

    2005-01-01

    The uncertainty relation for angle and angular momentum has a lower bound which depends on the form of the state. Surprisingly, this lower bound can be very large. We derive the states which have the lowest possible uncertainty product for a given uncertainty in the angle or in the angular momentum. We show that, if the given angle uncertainty is close to its maximum value, the lowest possible uncertainty product tends to infinity.

  3. Angular minimum uncertainty states with large uncertainties

    E-print Network

    Joerg B. Goette; Paul M. Radmore; Roberta Zambrini; Stephen M. Barnett

    2006-04-27

    The uncertainty relation for angle and angular momentum has a lower bound which depends on the form of the state. Surprisingly, this lower bound can be very large. We derive the states which have the lowest possible uncertainty product for a given uncertainty in the angle or in the angular momentum. We show that, if the given angle uncertainty is close to its maximum value, the lowest possible uncertainty product tends to infinity.

  4. Entanglement of Polarization and Orbital Angular Momentum

    E-print Network

    Daniel Bhatti; Joachim von Zanthier; Girish S. Agarwal

    2015-02-06

    We investigate two-photon entangled states using two important degrees of freedom of the electromagnetic field, namely orbital angular momentum (OAM) and spin angular momentum. For photons propagating in the same direction we apply the idea of $\\textit{entanglement duality}$ and develop schemes to do $\\textit{entanglement sorting}$ based either on OAM or polarization. In each case the entanglement is tested using appropriate witnesses. We finally present generalizations of these ideas to three- and four-photon entangled states.

  5. Angular momentum of walking at different speeds.

    PubMed

    Bennett, Bradford C; Russell, Shawn D; Sheth, Pradip; Abel, Mark F

    2010-02-01

    Recently, researchers in robotics have used regulation of the angular momentum of body segments about the total body center of mass (CoM) to develop control strategies for bipedal gait. This work was spurred by reports finding that for a "large class" of human movement tasks, including standing, walking, and running the angular momentum is conserved about the CoM. However, there is little data presented to justify this position. This paper describes an analysis of 11 male adults walking overground at 0.7, 1.0, and 1.3 times their comfortable walking speed (CWS). The normalized angular momenta about the body CoM of 12 body segments were computed about all three coordinate axes. The normalized angular momenta were both small (<0.03) and highly regulated for all subjects and walking speed with extrema that negatively correlated with walking speeds. It was found that the angular momentum of the body about its CoM during walking could be described by a small number of principal components. For the adult walkers the first three principal components accounted for more than 97% of the variability of the angular momentum about each of the three principal axes at all walking speeds. In addition, it was found that the orthogonal principal components at each speed and for each subject were similar, i.e., the vectors of the principal components at each speed and for each subject were co-linear. PMID:19889468

  6. Partial angular coherence and the angular Schmidt spectrum of entangled two-photon fields

    SciTech Connect

    Jha, Anand Kumar; Boyd, Robert W. [Institute of Optics, University of Rochester, Rochester, New York 14627 (United States); Agarwal, Girish S. [Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078 (United States)

    2011-12-15

    We study partially coherent fields that have a coherent-mode representation in the orbital-angular-momentum-mode basis. For such fields, we introduce the concepts of the angular coherence function and the coherence angle. Such fields are naturally produced by the process of parametric down-conversion--a second-order nonlinear optical process in which a pump photon breaks up into two entangled photons, known as the signal and idler photons. We show that the angular coherence functions of the signal and idler fields are directly related to the angular Schmidt (spiral) spectrum of the down-converted two-photon field and thus that the angular Schmidt spectrum can be measured directly by measuring the angular coherence function of either the signal or the idler field, without requiring coincidence detection.

  7. Transformation of the Angular Power Spectrum of Scattered Radiation in a Turbulent Absorbing Magnetoactive Plasma

    NASA Astrophysics Data System (ADS)

    Gavrilenko, V. G.; Sorokin, A. V.

    2002-11-01

    We consider the oblique incidence of a small-amplitude plane electromagnetic wave on a layer of turbulent absorbing plasma in a uniform external magnetic field. The equations for the first two statistical moments of the angular power spectrum of scattered radiation are derived in the geometrical-optics approximation. We show that two asymmetry factors of the problem, i.e., the oblique incidence and the influence of the anisotropic medium, compensate for each other along a certain direction and impede the appearance of the effect of displacement of the power-spectrum maximum and the effect of anomalous spectrum broadening. We find the condition at which such a case of wave propagation is realized. The dependence of the angular-spectrum shape on the distance from the plasma-layer boundary is studied numerically without using the small-angle approximation. The calculations confirm the results obtained using the geometrical-optics approximation.

  8. Efficient broadband third harmonic frequency conversion via angular dispersion

    SciTech Connect

    Pennington, D.M.; Henesian, M.A.; Milam, D.; Eimerl, D.

    1995-07-18

    In this paper we present experimental measurements and theoretical modeling of third harmonic (3{omega}) conversion efficiency with optical bandwidth. Third harmonic conversion efficiency drops precipitously as the input bandwidth significantly exceeds the phase matching limitations of the conversion crystals. For Type I/Type II frequency tripling, conversion efficiency be-gins to decrease for bandwidths greater than {approximately}60 GHz. However, conversion efficiency corresponding to monochromatic phase-matched beams can be recovered provided that the instantaneous Propagation vectors are phase matched at all times. This is achieved by imposing angular spectral dispersion (ASD) on the input beam via a diffraction grating, with a dispersion such that the phase mismatch for each frequency is zero. Experiments were performed on the Optical Sciences Laser (OSL), a 1--100 J class laser at LLNL. These experiments used a 200 GHz bandwidth source produced by a multipassed electro-optic phase modulator. The spectrum produced was composed of discrete frequency components spaced at 3 GHz intervals. Angular dispersion was incorporated by the addition of a 1200 gr/mm diffraction grating oriented at the Littrow angle, and capable of rotation about the beam direction. Experiments were performed with a pulse length of 1-ns and a 1{omega} input intensity of {approximately} 4 GW/cm{sup 2} for near optimal dispersion for phase matching, 5.2 {mu}rad/GHz, with 0.1, 60, and 155 GHz bandwidth, as well as for partial dispersion compensation, 1.66 {mu}rad/GHz, with 155 GHz and 0.1 GHz bandwidth. The direction of dispersion was varied incrementally 360{degrees} about the beam diameter. The addition of the grating to the beamline reduced the narrowband conversion efficiency by approximately 10%.

  9. Theoretical model for angular grating-based integrated optical vortex beam emitters.

    PubMed

    Zhu, Jiangbo; Cai, Xinlun; Chen, Yujie; Yu, Siyuan

    2013-04-15

    We develop a theoretical model for the recently reported integrated optical vortex beam emitters that incorporate angular gratings in microring resonators. Using azimuthally polarized dipole oscillators to represent emissions scattered from the grating elements that are located along the inner wall of the ring waveguide, we obtain expressions for far-field components under the paraxial approximation. The results show that the emission is of the form of cylindrical vector Bessel beams with exactly defined optical orbital angular momentum, and can have azimuthal, radial, and longitudinal field components after propagation. The calculation results for field distributions in both near and far zone agree well with the experimental results. PMID:23595479

  10. DISTRIBUTION OF ACCRETING GAS AND ANGULAR MOMENTUM ONTO CIRCUMPLANETARY DISKS

    SciTech Connect

    Tanigawa, Takayuki; Ohtsuki, Keiji [Center for Planetary Science, Kobe University, Kobe (Japan); Machida, Masahiro N., E-mail: tanigawa@cps-jp.org [Department of Earth and Planetary Sciences, Graduate School of Sciences, Kyushu University, Fukuoka (Japan)

    2012-03-01

    We investigate gas accretion flow onto a circumplanetary disk from a protoplanetary disk in detail by using high-resolution three-dimensional nested-grid hydrodynamic simulations, in order to provide a basis of formation processes of satellites around giant planets. Based on detailed analyses of gas accretion flow, we find that most of gas accretion onto circumplanetary disks occurs nearly vertically toward the disk surface from high altitude, which generates a shock surface at several scale heights of the circumplanetary disk. The gas that has passed through the shock surface moves inward because its specific angular momentum is smaller than that of the local Keplerian rotation, while gas near the midplane in the protoplanetary disk cannot accrete to the circumplanetary disk. Gas near the midplane within the planet's Hill sphere spirals outward and escapes from the Hill sphere through the two Lagrangian points L{sub 1} and L{sub 2}. We also analyze fluxes of accreting mass and angular momentum in detail and find that the distributions of the fluxes onto the disk surface are well described by power-law functions and that a large fraction of gas accretion occurs at the outer region of the disk, i.e., at about 0.1 times the Hill radius. The nature of power-law functions indicates that, other than the outer edge, there is no specific radius where gas accretion is concentrated. These source functions of mass and angular momentum in the circumplanetary disk would provide us with useful constraints on the structure and evolution of the circumplanetary disk, which is important for satellite formation.

  11. Geometric Approximation via Coresets

    Microsoft Academic Search

    PANKAJ K. AGARWAL; SARIEL HAR-PELED; KASTURI R. VARADARAJAN

    The paradigm of coresets has recently emerged as a powerful tool for eciently approximating various extent measures of a point set P. Using this paradigm, one quickly computes a small subset Q of P, called a coreset, that approximates the original set P and and then solves the problem on Q using a relatively inecient algorithm. The solution for Q

  12. Approximating Markov Chains

    Microsoft Academic Search

    Steven M. Pincus

    1992-01-01

    A common framework of finite state approximating Markov chains is developed for discrete time deterministic and stochastic processes. Two types of approximating chains are introduced: (i) those based on stationary conditional probabilities (time averaging) and (ii) transient, based on the percentage of the Lebesgue measure of the image of cells intersecting any given cell. For general dynamical systems, stationary measures

  13. Digital Angular Position Sensor Using Wavelength Division Multiplexing

    NASA Astrophysics Data System (ADS)

    Fritsch, Klaus; Beheim, Glenn; Sotomayor, Jorge L.

    1990-02-01

    Future aircraft will use fly-by-light control systems with fiber-linked optical sensors for such measurands as temperature, pressure, and linear and angular position. We describe a digital optical sensor which was developed to transmit the angular position of such slowly rotating parts as a throttle or fuel flow control valve on an aircraft. The sensor employs a reflective code plate with ten channels providing a resolution of 0.35 degrees. Two light-emitting diodes with overlapping spectra are used as light sources. A single micro-optic multiplexer-demultiplexer composed of a GRIN rod lens and a miniature grating is used to disperse the spectrum and recombine the spectral components from each channel after reflection by the code plate. We discuss the results of preliminary environmental tests of this unit. We have operated the sensor for brief periods of time between -60°C and +125°C without adverse effects. Preliminary vibration tests indicate that the unit will work properly at the maximum vibration levels expected in a jet-engine environment. Use of a reference track on the code plate in conjunction with an automatic gain control in the electronic circuit compensates for large changes in transmitted light intensity.

  14. Establishing an IERS Sub-Center for Ocean Angular Momentum

    NASA Technical Reports Server (NTRS)

    Ponte, Rui M.

    2001-01-01

    With the objective of establishing the Special Bureau for the Oceans (SBO), a new archival center for ocean angular momentum (OAM) products, we have computed and analyzed a number of OAM products from several ocean models, with and without data assimilation. All three components of OAM (axial term related to length of day variations and equatorial terms related to polar motion) have been examined in detail, in comparison to the respective Earth rotation parameters. An 11+ year time series of OAM given at 5-day intervals has been made publicly available. Other OAM products spanning longer periods and with higher temporal resolution, as well as products calculated from ocean model/data assimilation systems, have been prepared and should become part of the SBO archives in the near future.

  15. Ultrafast angular momentum transfer in multisublattice ferrimagnets.

    PubMed

    Bergeard, N; López-Flores, V; Halté, V; Hehn, M; Stamm, C; Pontius, N; Beaurepaire, E; Boeglin, C

    2014-01-01

    Femtosecond laser pulses can be used to induce ultrafast changes of the magnetization in magnetic materials. However, one of the unsolved questions is that of conservation of the total angular momentum during the ultrafast demagnetization. Here we report the ultrafast transfer of angular momentum during the first hundred femtoseconds in ferrimagnetic Co0.8Gd0.2 and Co0.74Tb0.26 films. Using time-resolved X-ray magnetic circular dichroism allowed for time-resolved determination of spin and orbital momenta for each element. We report an ultrafast quenching of the magnetocrystalline anisotropy and show that at early times the demagnetization in ferrimagnetic alloys is driven by the local transfer of angular momenta between the two exchange-coupled sublattices while the total angular momentum stays constant. In Co0.74Tb0.26 we have observed a transfer of the total angular momentum to an external bath, which is delayed by ~150?fs. PMID:24614016

  16. Angular momentum conservation for dynamical black holes

    E-print Network

    Sean A. Hayward

    2006-11-04

    Angular momentum can be defined by rearranging the Komar surface integral in terms of a twist form, encoding the twisting around of space-time due to a rotating mass, and an axial vector. If the axial vector is a coordinate vector and has vanishing transverse divergence, it can be uniquely specified under certain generic conditions. Along a trapping horizon, a conservation law expresses the rate of change of angular momentum of a general black hole in terms of angular momentum densities of matter and gravitational radiation. This identifies the transverse-normal block of an effective gravitational-radiation energy tensor, whose normal-normal block was recently identified in a corresponding energy conservation law. Angular momentum and energy are dual respectively to the axial vector and a previously identified vector, the conservation equations taking the same form. Including charge conservation, the three conserved quantities yield definitions of an effective energy, electric potential, angular velocity and surface gravity, satisfying a dynamical version of the so-called first law of black-hole mechanics. A corresponding zeroth law holds for null trapping horizons, resolving an ambiguity in taking the null limit.

  17. Angular momentum conservation for dynamical black holes

    SciTech Connect

    Hayward, Sean A. [Center for Astrophysics, Shanghai Normal University, 100 Guilin Road, Shanghai 200234 (China)

    2006-11-15

    Angular momentum can be defined by rearranging the Komar surface integral in terms of a twist form, encoding the twisting around of space-time due to a rotating mass, and an axial vector. If the axial vector is a coordinate vector and has vanishing transverse divergence, it can be uniquely specified under certain generic conditions. Along a trapping horizon, a conservation law expresses the rate of change of angular momentum of a general black hole in terms of angular momentum densities of matter and gravitational radiation. This identifies the transverse-normal block of an effective gravitational-radiation energy tensor, whose normal-normal block was recently identified in a corresponding energy conservation law. Angular momentum and energy are dual, respectively, to the axial vector and a previously identified vector, the conservation equations taking the same form. Including charge conservation, the three conserved quantities yield definitions of an effective energy, electric potential, angular velocity and surface gravity, satisfying a dynamical version of the so-called first law of black-hole mechanics. A corresponding zeroth law holds for null trapping horizons, resolving an ambiguity in taking the null limit.

  18. Variation in Angular Velocity and Angular Acceleration of a Particle in Rectilinear Motion

    ERIC Educational Resources Information Center

    Mashood, K. K.; Singh, V. A.

    2012-01-01

    We discuss the angular velocity ([image omitted]) and angular acceleration ([image omitted]) associated with a particle in rectilinear motion with constant acceleration. The discussion was motivated by an observation that students and even teachers have difficulty in ascribing rotational motion concepts to a particle when the trajectory is a…

  19. Theory of Angular Momentum This chapter is concerned with a systematic treatment of angular momen-

    E-print Network

    Satija, Indu

    153 CHAPTER 3 Theory of Angular Momentum This chapter is concerned with a systematic treatment to illustrate the noncommutativity of finite rotations. #12;154 155Theory of Angular NlOmentUm To be definite-plane, as viewed from the positi z-side. If we associate a right-handed screw with such a rotation, a rotation

  20. Degree Angular Scale Interferometer First Results: A Measurement of the Cosmic Microwave Background Angular Power Spectrum

    Microsoft Academic Search

    N. W. Halverson; E. M. Leitch; C. Pryke; J. Kovac; J. E. Carlstrom; W. L. Holzapfel; M. Dragovan; J. K. Cartwright; B. S. Mason; S. Padin; T. J. Pearson; A. C. S. Readhead; M. C. Shepherd

    2002-01-01

    We present measurements of anisotropy in the cosmic microwave background (CMB) from the first season of observations with the Degree Angular Scale Interferometer (DASI). The instrument was deployed at the South Pole in the austral summer 1999-2000, and we made observations throughout the following austral winter. We present a measurement of the CMB angular power spectrum in the range 100

  1. Angular distribution of quasi-ballistic light measured through turbid media using angular domain optical imaging

    E-print Network

    Chapman, Glenn H.

    Angular distribution of quasi-ballistic light measured through turbid media using angular domain of minimally deviated quasi-ballistic photons versus multiply scattered photons in a turbid medium. The study-machined arrays of micro-tunnels each with a different range of acceptance angles. The balance between quasi-ballistic

  2. A circularly polarized beam carries the double angular momentum

    E-print Network

    A circularly polarized beam carries the double angular momentum Radi I. Khrapko # Moscow Aviation without an azimuthal phase structure carries the double angular momentum in comparison with the prediction light beam without an azimuthal phase structure as total angular momentum of the beam, and the angular

  3. Angular momentum transport and large eddy simulations in magnetorotational turbulence: the small Pm limit

    E-print Network

    Meheut, H; Lesur, G; Joos, M; Longaretti, P -Y

    2015-01-01

    Angular momentum transport in accretion discs is often believed to be due to magnetohydrodynamic turbulence mediated by the magnetorotational instability. Despite an abundant literature on the MRI, the parameters governing the saturation amplitude of the turbulence are poorly understood and the existence of an asymptotic behavior in the Ohmic diffusion regime is not clearly established. We investigate the properties of the turbulent state in the small magnetic Prandtl number limit. Since this is extremely computationally expensive, we also study the relevance and range of applicability of the most common subgrid scale models for this problem. Unstratified shearing boxes simulations are performed both in the compressible and incompressible limits, with a resolution up to 800 cells per disc scale height. The latter constitutes the largest resolution ever attained for a simulation of MRI turbulence. In the presence of a mean magnetic field threading the domain, angular momentum transport converges to a finite va...

  4. Angular spectrum detection instrument for label-free photonic crystal sensors.

    PubMed

    Liu, Longju; Xu, Zhen; Dong, Liang; Lu, Meng

    2014-05-01

    An angular spectrum analysis system was demonstrated to monitor the optical resonant mode of a photonic crystal (PC) sensor comprised of a one-dimensional grating structure. Exposed to solutions with different refractive indices or adsorbed with biomaterials, the PC sensor exhibited changes of the optical resonant modes. The developed detection system utilized a focused laser beam to detect shifts of the resonant angle, and thereby allowed a kinetic analysis of chemical absorption. Such a detection apparatus offers an adjustable angular resolution and a tunable detection range for a wide variety of refractometric sensing applications. A limit of detection of 6.57×10(-5) refractive index unit has been observed. The instrument also offers an imaging capability of rapidly characterizing low-contrast samples deposited on the PC surface with a spatial resolution of 10 ?m. PMID:24784094

  5. A high-resolution optical see-through head-mounted display with eyetracking capability.

    PubMed

    Hua, Hong; Hu, Xinda; Gao, Chunyu

    2013-12-16

    A head-mounted display system with fully-integrated eyetracking capability offers multi-fold benefits, not only to fundamental scientific research but also to emerging applications of such technology. A key limitation of the state-of-the-art eyetracked head-mounted display (ET-HMD) technology is the lack of compactness and portability. In this paper, we present an innovative design of a high resolution optical see-through ET-HMD system based on freeform optical technology. A prototype system is demonstrated, which offers a goggle-like compact form factor, non-obstructive see-through field of view and true high-definition image resolution for the virtual display. The see-through view, via the combination of a freeform prism and corrector, achieved better than 0.5 arc minute of angular resolution for the central region of approximately 40-degrees to ensure minimal impacts on the see-through vision of an HMD user. PMID:24514672

  6. Optimization of Angular-Momentum Biases of Reaction Wheels

    NASA Technical Reports Server (NTRS)

    Lee, Clifford; Lee, Allan

    2008-01-01

    RBOT [RWA Bias Optimization Tool (wherein RWA signifies Reaction Wheel Assembly )] is a computer program designed for computing angular momentum biases for reaction wheels used for providing spacecraft pointing in various directions as required for scientific observations. RBOT is currently deployed to support the Cassini mission to prevent operation of reaction wheels at unsafely high speeds while minimizing time in undesirable low-speed range, where elasto-hydrodynamic lubrication films in bearings become ineffective, leading to premature bearing failure. The problem is formulated as a constrained optimization problem in which maximum wheel speed limit is a hard constraint and a cost functional that increases as speed decreases below a low-speed threshold. The optimization problem is solved using a parametric search routine known as the Nelder-Mead simplex algorithm. To increase computational efficiency for extended operation involving large quantity of data, the algorithm is designed to (1) use large time increments during intervals when spacecraft attitudes or rates of rotation are nearly stationary, (2) use sinusoidal-approximation sampling to model repeated long periods of Earth-point rolling maneuvers to reduce computational loads, and (3) utilize an efficient equation to obtain wheel-rate profiles as functions of initial wheel biases based on conservation of angular momentum (in an inertial frame) using pre-computed terms.

  7. Exact light propagation between rotated planes using non-uniform sampling and angular spectrum method

    NASA Astrophysics Data System (ADS)

    Kim, Yong-Hae; Kim, Gi Heon; Ryu, Hojun; Chu, Hye-Yong; Hwang, Chi-Sun

    2015-06-01

    A novel method is proposed for simulating exact light propagation between rotated planes using non-uniform sampling and angular spectrum method. Angular spectrum method (ASM) was widely used for simulating light diffraction between rotated planes using uniform sampling and interpolation of positive spatial frequency spectrums along z axis on a rotated destination plane which is an approximation valid only for large sampling interval on a source plane and for small rotation angle of a destination plane. To simulate exact wave propagation between rotated planes independent on sampling interval on a source plane or rotation angle of a destination plane, we applied non-uniform sampling to angular spectrum method. In the proposed method, we can produce simulation results between rotated planes with high accuracy for any sampling interval on a source plane or for any rotated angle.

  8. Fractional angular momentum in cold atom systems

    E-print Network

    Yuhe Zhang; G. J. Sreejith; N. D. Gemelke; J. K. Jain

    2014-10-21

    The quantum statistics of bosons or fermions are manifest through even or odd relative angular momentum of a pair. We show theoretically that, under certain conditions, a pair of certain test particles immersed in a fractional quantum Hall state possesses, effectively, a fractional relative angular momentum, which can be interpreted in terms of fractional braid statistics. We propose that the fractionalization of the angular momentum can be detected directly through the measurement of the pair correlation function in rotating ultra-cold atomic systems in the fractional quantum Hall regime. Such a measurement will also provide direct evidence for the effective magnetic field, resulting from Berry phases arising from attached vortices, and of excitations with fractional particle number, analogous to fractional charge of electron fractional quantum Hall effect.

  9. Electromagnetic angular momentum transport in Saturn's rings

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.; Morfill, G. E.; Ip, W.; Gruen, E.; Havnes, O.

    1986-01-01

    It is shown here that submicrometer dust particles sporadically elevated above Saturn's ring are subject to electromagnetic forces which will reduce their angular momentum inside synchronous orbit and increase it outside. When the dust is reabsorbed by the ring the angular momentum of the ring is decreased (increased) inside (outside) of synchronous orbit. For the case of the spokes in Saturn's B-ring it is estimated that the timescale for transporting ring material due to this angular momentum coupling effect is comparable to the viscous transport time or even smaller. It is suggested that the minimum in the optical depth of the B-ring at synchronous orbit is due to this effect.

  10. Quark Orbital Angular Momentum from Lattice QCD

    E-print Network

    N. Mathur; S. J. Dong; K. F. Liu; L. Mankiewicz; N. C. Mukhopadhyay

    1999-12-10

    We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the $Z_2$ noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be $0.30 \\pm 0.07$. From this and the quark spin content we deduce the quark orbital angular momentum to be $0.17 \\pm 0.06$ which is $\\sim 34$% of the proton spin. We further predict that the gluon angular momentum to be $0.20 \\pm 0.07$, i. e. $\\sim$ 40% of the proton spin is due to the glue.

  11. Quark Orbital Angular Momentum from Lattice QCD

    E-print Network

    Mathur, N D; Liu Ke Feng; Mankiewicz, L; Mukhopadhyay, N C

    2000-01-01

    We calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the $Z_2$ noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be $0.30 \\pm 0.07$. From this and the quark spin content we deduce the quark orbital angular momentum to be $0.17 \\pm 0.06$ which is $\\sim 34$% of the proton spin. We further predict that the gluon angular momentum to be $0.20 \\pm 0.07$, i. e.

  12. Angular analysis of the decay ? b ? ?(? N?) ? + ? -

    NASA Astrophysics Data System (ADS)

    Böer, Philipp; Feldmann, Thorsten; van Dyk, Danny

    2015-01-01

    We study the differential decay rate for the rare ? b ? ?(? N?) ? + ? - transition, including a determination of the complete angular distribution, assuming unpolarized ? b baryons. On the basis of a properly chosen parametrization of the various helicity amplitudes, we provide expressions for the angular observables within the Standard Model and a subset of new physics models with chirality-flipped operators. Hadronic effects at low recoil are estimated by combining information from lattice QCD with (improved) form-factor relations in Heavy Quark Effective Theory. Our estimates for large hadronic recoil — at this stage — are still rather uncertain because the baryonic input functions are not so well known, and non-factorizable spectator effects have not been worked out systematically so far. Still, our phenomenological analysis of decay asymmetries and angular observables for ? b ? ?(? N?) ? + ? - reveals that this decay mode can provide new and complementary constraints on the Wilson coefficients in radiative and semileptonic b ? s transitions compared to the corresponding mesonic modes.

  13. Mars - Satellite origin and angular momentum

    NASA Technical Reports Server (NTRS)

    Hartmann, W. K.; Davis, D. R.; Chapman, C. R.; Soter, S.; Greenberg, R.

    1975-01-01

    The origin of Phobos and Deimos is considered with a view to accounting for the existence of very small satellites with circular orbits in the Martian equatorial plane, and simultaneously for the suspected angular momentum deficiency of the Mars system. All models considered failed to satisfy at least one requirement, and the problem is considered more puzzling than is at first apparent. The Martian angular momentum deficiency, if physically significant, may be unrelated to the present satellites' origin, but might relate to a large ancient satellite, long ago destroyed. Accretion onto Mars of large amounts of asteroidal dust brought in by Poynting-Robertson drag may have some bearing on the angular momentum problem.

  14. Angular distribution of atoms ejected by laser ablation of different metals

    SciTech Connect

    Konomi, I.; Motohiro, T. [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511 (Japan); Toyota Central Research and Development Laboratories, Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Asaoka, T. [Toyota Central Research and Development Laboratories, Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan)

    2009-07-01

    Angular distributions of 13 different metals ejected by laser ablation using fourth harmonics (wavelength=266 nm) of neodymium doped yttrium aluminum garnet laser and a fluence close to near-threshold value (2.3 J/cm{sup 2}) have been investigated with a high angular resolution. The angular distribution which is characterized by the exponent n of cos{sup n} theta distribution showed very broad range of values between 3 and 24 for different metals. A simple relation that the exponent n is proportional to the square root of particle atomic weight as reported previously has not been observed. Instead, a general trend has been found that the metals with higher sublimation energy such as Ta and Zr show narrower angular distribution than those with lower sublimation energy such as Sn and In. While the sublimation energy of metals has a great influence on the angular distribution of ejected atoms, a simple consideration suggests that their thermal conductivity and specific heat have little effect on it.

  15. SUB-M-RAD ANGULAR STABILITY MEASUREMENTS BY USE OF LONG TRACE PROFILER BASED SYSTEMS.

    SciTech Connect

    QIAN,S.

    1999-07-23

    High accuracy angle measurement at the sub-{mu}rad level requires extremely high instrument stability. In order to reach sub-{mu}rad stability (0.1 arc second or less) over long time periods, it is necessary to maintain the test object and almost all of the optical components in the measuring instrument in very steady positions. However, mechanical force relaxation, thermal expansion, and asymmetric structures produce angular and linear displacements in the system resulting in angular measurement error. A Long-Trace-Profiler (LTP)-based stable equipment is used to test precision angular stability with sub-{mu}rad resolution. Long term stability over 15 hours has been measured on different kind of mechanical structures. Temperature monitoring during the tests is extremely important. Some test results showing the effects of thermal variations are presented, which indicate that temperature stability on the order of 0.1 C is absolutely necessary for repeatable sub-{mu}rad measurements. The optical method, using optics with an even number of reflecting surfaces (for example, a right angle prism, pentaprism, or rhomboid prism) to reduce the influence of existing angular displacement, is introduced and the comparison measurement is presented. An optical fiber transfer line is able to reduce the laser angular shift from about 10 {mu}rad to a level of 0.3 {mu}rad rms. Careful system configuration, design and operation are very important for the sub-{mu}rad angle stability.

  16. A New Automatic System for Angular Measurement and Calibration in Radiometric Instruments

    PubMed Central

    Marquez, Jose Manuel Andujar; Bohórquez, Miguel Ángel Martínez; Garcia, Jonathan Medina; Nieto, Francisco Jose Aguilar

    2010-01-01

    This paper puts forward the design, construction and testing of a new automatic system for angular-response measurement and calibration in radiometric instruments. Its main characteristics include precision, speed, resolution, noise immunity, easy programming and operation. The developed system calculates the cosine error of the radiometer under test by means of a virtual instrument, from the measures it takes and through a mathematical procedure, thus allowing correcting the radiometer with the aim of preventing cosine error in its measurements. PMID:22319320

  17. Extending high-angular accuracy to a near omni-directional 3D range sensor

    Microsoft Academic Search

    Albert Iavarone; Reda Fayek

    2005-01-01

    The emergence of tripod-mounted lidar sensors as a viable method of 3D data collection has provided users with the ability to interrogate structures using high-resolution, metrically accurate 3D measurements. As with any measurement device, the accuracy of the collected data is of paramount importance. Angular accuracy is a crucial parameter in the overall performance of a 3D range sensor. This

  18. Studying oxygen vacancies in ceramics by perturbed angular correlation spectroscopy

    SciTech Connect

    Su, Han-Tzong; Wang, Ruiping; Fuchs, H.; Gardner, J.A. (Oregon State Univ., Corvallis, OR (USA). Dept. of Physics); Evenson, W.E. (Brigham Young Univ., Provo, UT (USA). Dept. of Physics); Sommers, J.A. (Teledyne-Wah Chang, Albany, OR (USA))

    1990-01-01

    Perturbed angular correlation measurements in tetragonal and cubic zirconia and in ceria are described. A physically reasonable and self-consistent interpretation of these data implies that oxygen vacancies are trapped at a second neighbor position by Cd in tetragonal zirconia and by In in ceria. For Cd in tetragonal zirconia, the vacancy trap energy is found to be 0.44 eV, and the energy barrier between adjacent trap sites is approximately 0.8 eV. The activation energy of an oxygen vacancy hopping between trap sites around {sup 111}Cd in ceria is found to be 0.55 eV. The activation energy for oxygen vacancy hopping in cubic zirconia, as detected by {sup 181}Ta PAC, is about 1.0 eV and independent of the Y concentration. 12 refs., 4 figs.

  19. Retardation effects and angular coefficients in double photoionization

    SciTech Connect

    Kornberg, M.A.; Miraglia, J.E. [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina)] [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina)

    1995-10-01

    Retardation effects on the cross sections for double photoionization of He({sup 1}{ital S}{sub 0}) targets are studied at photon energies above 1.0 keV. The dipole asymmetry parameter {beta} is examined first and the importance of correlation in the final and initial states for this quantity is examined. The effects of retardation on the electron angular distributions are studied and the range of validity of a first-order retardation correction is evaluated. Finally, by using a simple model to calculate the total cross section, the contribution of retardation on the double ionization {sigma}{sup 2+} is calculated and it is found that the ratio of double to single photoionization, including retardation, remains the same as when the dipole velocity approximation is employed.

  20. Approximate distance oracles

    Microsoft Academic Search

    Mikkel Thorup; Uri Zwick

    2005-01-01

    Let G = (V,E) be an undirected weighted graph with |V| = n and |E| = m. Let k ? 1 be an integer. We show that G = (V,E) can be preprocessed in O(kmn1\\/k) expected time, constructing a data structure of size O(kn1+1\\/k), such that any subsequent distance query can be answered, approximately, in O(k) time. The approximate distance

  1. Angular gyrus syndrome mimicking depressive pseudodementia

    PubMed Central

    Nagaratnam, Nages; Phan, Tai Anh; Barnett, Claire; Ibrahim, Neamat

    2002-01-01

    A 67-year-old left-handed woman with a diagnosis of pseudodementia was being treated for depression with little benefit. Neuropsychological evaluations revealed features of angular gyrus syndrome, namely, agraphia, alexia, Gerstmann's syndrome and behavioural manifestations such as depression, poor memory, frustration and irritability. A computed tomographic scan showed a right occipito-temporal infarction, which had occurred 18 months earlier. The patient demonstrated aspects of language dysfunction associated with the syndrome and showed reversed lateralization of cerebral functions. Recognizing and distinguishing between angular gyrus syndrome and depression is important because the appropriate therapies differ. The use of the term pseudodementia can be misleading. PMID:12271792

  2. Probing angular correlations in sequential double ionization.

    PubMed

    Fleischer, A; Wörner, H J; Arissian, L; Liu, L R; Meckel, M; Rippert, A; Dörner, R; Villeneuve, D M; Corkum, P B; Staudte, A

    2011-09-01

    We study electron correlation in sequential double ionization of noble gas atoms and HCl in intense, femtosecond laser pulses. We measure the photoelectron angular distributions of Ne+ relative to the first electron in a pump-probe experiment with 8 fs, 800 nm, circularly polarized laser pulses at a peak intensity of a few 10(15)??W/cm2. Using a linear-linear pump-probe setup, we further study He, Ar, and HCl. We find a clear angular correlation between the two ionization steps in the sequential double ionization intensity regime. PMID:22026661

  3. Probing Angular Correlations in Sequential Double Ionization

    SciTech Connect

    Fleischer, A. [Joint Attosecond Science Laboratory, National Research Council and University of Ottawa, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6 (Canada); Department of Physics and Solid State Institute, Technion, Haifa 32000 (Israel); Woerner, H. J. [Joint Attosecond Science Laboratory, National Research Council and University of Ottawa, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6 (Canada); ETH Zuerich, Wolfgang-Pauli-Strasse 10, 8093 Zuerich (Switzerland); Arissian, L. [Joint Attosecond Science Laboratory, National Research Council and University of Ottawa, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6 (Canada); Texas A and M University, College Station, Texas 77843 (United States); Liu, L. R. [Joint Attosecond Science Laboratory, National Research Council and University of Ottawa, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6 (Canada); University of Toronto, 40 St. George Street, Toronto, Ontario M5S 2E4 (Canada); Meckel, M.; Rippert, A.; Doerner, R. [Institut fuer Kernphysik, Goethe Universitaet, Max-von-Laue Strasse 1, D-60438 Frankfurt (Germany); Villeneuve, D. M.; Corkum, P. B.; Staudte, A. [Joint Attosecond Science Laboratory, National Research Council and University of Ottawa, 100 Sussex Drive, Ottawa, Ontario, K1A 0R6 (Canada)

    2011-09-09

    We study electron correlation in sequential double ionization of noble gas atoms and HCl in intense, femtosecond laser pulses. We measure the photoelectron angular distributions of Ne{sup +} relative to the first electron in a pump-probe experiment with 8 fs, 800 nm, circularly polarized laser pulses at a peak intensity of a few 10{sup 15} W/cm{sup 2}. Using a linear-linear pump-probe setup, we further study He, Ar, and HCl. We find a clear angular correlation between the two ionization steps in the sequential double ionization intensity regime.

  4. Total angular momentum from Dirac eigenspinors

    E-print Network

    Laszlo B. Szabados

    2007-12-17

    The eigenvalue problem for Dirac operators, constructed from two connections on the spinor bundle over closed spacelike 2-surfaces, is investigated. A class of divergence free vector fields, built from the eigenspinors, are found, which, for the lowest eigenvalue, reproduce the rotation Killing vectors of metric spheres, and provide rotation BMS vector fields at future null infinity. This makes it possible to introduce a well defined, gauge invariant spatial angular momentum at null infinity, which reduces to the standard expression in stationary spacetimes. The general formula for the angular momentum flux carried away be the gravitational radiation is also derived.

  5. Approximate kernel competitive learning.

    PubMed

    Wu, Jian-Sheng; Zheng, Wei-Shi; Lai, Jian-Huang

    2015-03-01

    Kernel competitive learning has been successfully used to achieve robust clustering. However, kernel competitive learning (KCL) is not scalable for large scale data processing, because (1) it has to calculate and store the full kernel matrix that is too large to be calculated and kept in the memory and (2) it cannot be computed in parallel. In this paper we develop a framework of approximate kernel competitive learning for processing large scale dataset. The proposed framework consists of two parts. First, it derives an approximate kernel competitive learning (AKCL), which learns kernel competitive learning in a subspace via sampling. We provide solid theoretical analysis on why the proposed approximation modelling would work for kernel competitive learning, and furthermore, we show that the computational complexity of AKCL is largely reduced. Second, we propose a pseudo-parallelled approximate kernel competitive learning (PAKCL) based on a set-based kernel competitive learning strategy, which overcomes the obstacle of using parallel programming in kernel competitive learning and significantly accelerates the approximate kernel competitive learning for large scale clustering. The empirical evaluation on publicly available datasets shows that the proposed AKCL and PAKCL can perform comparably as KCL, with a large reduction on computational cost. Also, the proposed methods achieve more effective clustering performance in terms of clustering precision against related approximate clustering approaches. PMID:25528318

  6. Simulations of 2D Turbulence in the Anelastic Approximation

    Microsoft Academic Search

    T. M. Rogers; G. A. Glatzmaier; S. E. Woosley

    2002-01-01

    High resolution simulations of two-dimensional convection using the Anelastic approximation are presented. These calculations span Rayleigh numbers from 108}-10{12 for Prandtl number equal to unity. This range covers several decades in the hard turbulent regime. While many studies of this sort have been conducted for the Boussinesq approximation, these are the first to use the Anelastic Approximation in this turbulent

  7. High-statistics study of the low-energy cosmic-muons angular distribution: Results from MICRO

    Microsoft Academic Search

    G. Battistoni; C. Bloise; A. F. Grillo; A. Marini; F. Ronga; V. Valente

    1988-01-01

    Summary  We present results from MICRO, a muon telescope with good angular resolution, which has collected more than 31106 cosmic muons. Upper limits are given for the flux coming from point sources and for the periodic component from Cygnus X3.

  8. Angular Momentum Role in the Hypercritical Accretion of Binary-Driven Hypernovae

    E-print Network

    L. Becerra; F. Cipolletta; C. L. Fryer; Jorge A. Rueda; R. Ruffini

    2015-05-28

    The induced gravitational collapse (IGC) paradigm explains a class of energetic, $E_{\\rm iso}\\gtrsim 10^{52}$~erg, long-duration gamma-ray bursts (GRBs) associated with Ic supernovae, recently named binary-driven hypernovae (BdHNe). The progenitor is a tight binary system formed of a carbon-oxygen (CO) core and a neutron star companion. The supernova ejecta of the exploding CO core triggers a hypercritical accretion process onto the neutron star, which reaches in a few seconds the critical mass, and gravitationally collapses to a black hole emitting a GRB. In our previous simulations of this process we adopted a spherically symmetric approximation to compute the features of the hypercritical accretion process. We here present the first estimates of the angular momentum transported by the supernova ejecta, $L_{\\rm acc}$, and perform numerical simulations of the angular momentum transfer to the neutron star during the hyperaccretion process in full general relativity. We show that the neutron star: i) reaches in a few seconds either mass-shedding limit or the secular axisymmetric instability depending on its initial mass; ii) reaches a maximum dimensionless angular momentum value, $[c J/(G M^2)]_{\\rm max}\\approx 0.7$; iii) can support less angular momentum than the one transported by supernova ejecta, $L_{\\rm acc} > J_{\\rm NS,max}$, hence there is an angular momentum excess which necessarily leads to jetted emission.

  9. A Novel Permanent Magnetic Angular Acceleration Sensor.

    PubMed

    Zhao, Hao; Feng, Hao

    2015-01-01

    Angular acceleration is an important parameter for status monitoring and fault diagnosis of rotary machinery. Therefore, we developed a novel permanent magnetic angular acceleration sensor, which is without rotation angle limitations and could directly measure the instantaneous angular acceleration of the rotating system. The sensor rotor only needs to be coaxially connected with the rotating system, which enables convenient sensor installation. For the cup structure of the sensor rotor, it has a relatively small rotational inertia. Due to the unique mechanical structure of the sensor, the output signal of the sensor can be directed without a slip ring, which avoids signal weakening effect. In this paper, the operating principle of the sensor is described, and simulated using finite element method. The sensitivity of the sensor is calibrated by torsional pendulum and angle sensor, yielding an experimental result of about 0.88 mV/(rad·s-2). Finally, the angular acceleration of the actual rotating system has been tested, using both a single-phase asynchronous motor and a step motor. Experimental result confirms the operating principle of the sensor and indicates that the sensor has good practicability. PMID:26151217

  10. Angular spectrum of quantized light beams

    E-print Network

    A. Aiello; J. Visser; G. Nienhuis; J. P. Woerdman

    2006-02-20

    We introduce a generalized angular spectrum representation for quantized light beams. By using our formalism, we are able to derive simple expressions for the electromagnetic vector potential operator in the case of: {a)} time-independent paraxial fields, {b)} time-dependent paraxial fields, and {c)} non-paraxial fields. For the first case, the well known paraxial results are fully recovered.

  11. Incorporating Angular Information into Parametric Models

    Microsoft Academic Search

    G. A. Watson

    2002-01-01

    The problem is considered of fitting a parametrically defined model in two or three dimensions to observed data, when angular information about the measured data points is available. Gauss-Newton methods based on correct separation of variables are developed. Some numerical results are included.

  12. TE10 resonant iris with angular alignment

    E-print Network

    Bornemann, Jens

    TE10 resonant iris with angular alignment TE101 mode cavities TM110 mode cavities TE01 (TE10) resonant iris 1a 1b Fig. 1: Filter configurations utilizing cavity and iris resonances. Resonant irises and resonant irises. Two different configurations, which allow precise control of the direct couplings between

  13. Angular-momentum-bearing modes in fission

    SciTech Connect

    Moretto, L.G.; Peaslee, G.F.; Wozniak, G.J.

    1989-03-01

    The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs.

  14. An angular momentum bound at null infinity

    E-print Network

    Piotr T. Chru?ciel; Paul Tod

    2007-06-27

    We prove an inequality relating the trace of the extrinsic curvature, the total angular momentum, the centre of mass, and the Trautman-Bondi mass for a class of gravitational initial data sets with constant mean curvature extending to null infinity. As an application we obtain non-existence results for the asymptotic Dirichlet problem for CMC hypersurfaces in stationary space-times.

  15. Angular momentum of multimode and polarization patterns

    Microsoft Academic Search

    Roberta Zambrini; Stephen M. Barnett

    2007-01-01

    We study the mechanical properties of a broad class of multimode and polarization light patterns, resulting from the interference and superposition of waves in helical modes. General local and global properties of energy and angular momentum (AM) are identifie d, in order to define the conditions to optimize the AM with increasing beam complexity. We show the possibility to engineer

  16. Angular momentum of optical vortex arrays

    Microsoft Academic Search

    Johannes Courtial; Roberta Zambrini; Mark R. Dennis; Mikhail Vasnetsov

    2006-01-01

    Guided by the aim to construct light fields with spin-like orbital angular momentum (OAM), that is light fields with a uniform and intrinsic OAM density, we investigate the OAM of arrays of optical vortices with rectangular symmetry. We find that the OAM per unit cell depends on the choice of unit cell and can even change sign when the unit

  17. Wigner Functions and Quark Orbital Angular Momentum

    E-print Network

    Asmita Mukherjee; Sreeraj Nair; Vikash Kumar Ojha

    2014-09-25

    Wigner distributions contain combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We report on a recent model calculation of the Wigner distributions for the quark and their relation to the orbital angular momentum.

  18. Strain uniformity through equal channel angular extrusion 

    E-print Network

    Bier, Derek Werner

    1997-01-01

    The objective of this work is to characterize the processing effects of equal channel angular extrusion (ECAE) on aluminum 6063, copper I 10, and filamentary Cu/NbTi composite superconductor. The major objective of this study is to measure strain...

  19. Covariant approximation averaging

    NASA Astrophysics Data System (ADS)

    Shintani, Eigo; Arthur, Rudy; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph

    2015-06-01

    We present a new class of statistical error reduction techniques for Monte Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in Nf=2 +1 lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte Carlo calculations over conventional methods for the same cost.

  20. Molecular collisions. 11: Semiclassical approximation to atom-symmetric top rotational excitation

    NASA Technical Reports Server (NTRS)

    Russell, D.; Curtiss, C. F.

    1973-01-01

    In a paper of this series a distorted wave approximation to the T matrix for atom-symmetric top scattering was developed which is correct to first order in the part of the interaction potential responsible for transitions in the component of rotational angular momentum along the symmetry axis of the top. A semiclassical expression for this T matrix is derived by assuming large values of orbital and rotational angular momentum quantum numbers.

  1. Approximate distance oracles

    Microsoft Academic Search

    Mikkel Thorup; Uri Zwick

    2001-01-01

    Let G=(V,E) be an undirected weighted graph with |V|=n and |E|=m. Let k\\\\ge 1 be an integer. We show that G=(V,E) can be preprocessed in O(kmn^{1\\/k}) expected time, constructing a data structure of size O(kn^{1+1\\/k}), such that any subsequent distance query can be answered, approximately, in O(k) time. The approximate distance returned is of stretch at most 2k-1, i.e., the

  2. Scaling of mean lifetimes of metastable molecular states with angular-momentum and vibrational quantum numbers

    SciTech Connect

    Ben-Itzhak, I.; Chen, Z.; Lin, C.D. (James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States))

    1995-03-01

    The dependence of the mean lifetimes of metastable molecular ions on the vibrational and rotational quantum numbers is determined empirically. From the mean lifetimes calculated using the phase-shift method for the [sup 3]He[sup 4]He[sup 2+] and [sup 20]Ne[sup 40]Ar[sup 2+] metastable molecular ions, we show that the mean lifetimes of rotational states decrease with angular momentum [ital l] approximately as [tau][sub [ital l

  3. Linear force and moment equations for an annular smooth shaft seal perturbed both angularly and laterally

    NASA Technical Reports Server (NTRS)

    Fenwick, J.; Dijulio, R.; Ek, M. C.; Ehrgott, R.

    1982-01-01

    Coefficients are derived for equations expressing the lateral force and pitching moments associated with both planar translation and angular perturbations from a nominally centered rotating shaft with respect to a stationary seal. The coefficients for the lowest order and first derivative terms emerge as being significant and are of approximately the same order of magnitude as the fundamental coefficients derived by means of Black's equations. Second derivative, shear perturbation, and entrance coefficient variation effects are adjudged to be small.

  4. Hartree approximation to QCD in the Fock-Schwinger gauge

    Microsoft Academic Search

    M. Schaden; St. Glazek; E. Werner

    1987-01-01

    The gluonic mean field in the Hartree approximation is obtained utilizing the Fock-Schwinger gauge. The potential in Euclidean space-time is color diagonal and local. The angular momentum decomposition of gluonic states can be done and the self-consistency equations then only depend on the (Euclidean) radial variable rho=xmuxmu. Close to the gauge-fixing point we find that the potential resembles that of

  5. Ordinances and Resolutions ORDINANCES, RESOLUTIONS AND REGULATIONS

    E-print Network

    Brierley, Andrew

    Page 2.1 Ordinances and Resolutions ORDINANCES, RESOLUTIONS AND REGULATIONS 1. ORDINANCES AND RESOLUTIONS I. REGULATIONS FOR RESEARCH STUDENTS AND APPOINTMENT OF RESEARCH FELLOWS Ordinance 350, and Supplementary Regulations by the Senatus Academicus 1. Ordinance No. 61 (General No. 23) of the Commissioners

  6. High-resolution lithospheric imaging with seismic interferometry

    NASA Astrophysics Data System (ADS)

    Ruigrok, Elmer; Campman, Xander; Draganov, Deyan; Wapenaar, Kees

    2010-10-01

    In recent years, there has been an increase in the deployment of relatively dense arrays of seismic stations. The availability of spatially densely sampled global and regional seismic data has stimulated the adoption of industry-style imaging algorithms applied to converted- and scattered-wave energy from distant earthquakes, leading to relatively high-resolution images of the lower crust and upper mantle. We use seismic interferometry to extract reflection responses from the coda of transmitted energy from distant earthquakes. In theory, higher-resolution images can be obtained when migrating reflections obtained with seismic interferometry rather than with conversions, traditionally used in lithospheric imaging methods. Moreover, reflection data allow the straightforward application of algorithms previously developed in exploration seismology. In particular, the availability of reflection data allows us to extract from it a velocity model using standard multichannel data-processing methods. However, the success of our approach relies mainly on a favourable distribution of earthquakes. In this paper, we investigate how the quality of the reflection response obtained with interferometry is influenced by the distribution of earthquakes and the complexity of the transmitted wavefields. Our analysis shows that a reasonable reflection response could be extracted if (1) the array is approximately aligned with an active zone of earthquakes, (2) different phase responses are used to gather adequate angular illumination of the array and (3) the illumination directions are properly accounted for during processing. We illustrate our analysis using a synthetic data set with similar illumination and source-side reverberation characteristics as field data recorded during the 2000-2001 Laramie broad-band experiment. Finally, we apply our method to the Laramie data, retrieving reflection data. We extract a 2-D velocity model from the reflections and use this model to migrate the data. On the final reflectivity image, we observe a discontinuity in the reflections. We interpret this discontinuity as the Cheyenne Belt, a suture zone between Archean and Proterozoic terranes.

  7. Approximation Algorithms Tandy Warnow

    E-print Network

    Warnow,Tandy

    CS 331 Approximation Algorithms Tandy Warnow #12;Princeton University · COS 423 · Theory-SAT 3-SAT DIR-HAM-CYCLEINDEPENDENT SET VERTEX COVER GRAPH 3-COLOR HAM-CYCLE TSP SUBSET of DNA sequences) Travelling Salesman (finding a minimum cost tour in an edge-weighted graph) #12;Vertex

  8. Complexity of Approximating the

    E-print Network

    Fomin, Fedor V.

    Complexity of Approximating the Oriented Diameter of Chordal Graphs Fedor V. Fomin,1 Marti the diameters of strongly connected orientations of G. We study algorithmic aspects of determining the oriented chordal bcu graph G, finds a strongly connected orientation of G with diameter at most one plus twice

  9. Social choice Approximate MAX CUT

    E-print Network

    Pansu, Pierre

    Social choice Un-friends Approximate MAX CUT Unique games Hardness of approximation P. Pansu;Social choice Un-friends Approximate MAX CUT Unique games Today's menu: A theorem in social choice theory-Sud Hardness of approximation #12;Social choice Un-friends Approximate MAX CUT Unique games Influences Noise

  10. Angular Momentum Exchange in White Dwarf Binaries Accreting Through Direct Impact

    NASA Astrophysics Data System (ADS)

    Sepinsky, J. F.; Kalogera, V.

    2014-04-01

    We examine the exchange of angular momentum between the component spins and the orbit in semi-detached double white dwarf binaries undergoing mass transfer through direct impact of the transfer stream. We approximate the stream as a series of discrete massive particles ejected in the ballistic limit at the inner Lagrangian point of the donor toward the accretor. This work improves upon similar earlier studies in a number of ways. First, we self-consistently calculate the total angular momentum of the orbit at all times. This includes changes in the orbital angular momentum during the ballistic trajectory of the ejected mass, as well as changes during the ejection/accretion due to the radial component of the particle's velocity. Second, we calculate the particle's ballistic trajectory for each system, which allows us to determine the precise position and velocity of the particle upon accretion. We can then include specific information about the radius of the accretor as well as the angle of impact. Finally, we ensure that the total angular momentum is conserved, which requires the donor star spin to vary self-consistently. With these improvements, we calculate the angular momentum change of the orbit and each binary component across the entire parameter space of direct impact double white dwarf binary systems. We find a significant decrease in the amount of angular momentum removed from the orbit during mass transfer, as well as cases where this process increases the angular momentum of the orbit at the expense of the spin angular momentum of the donor. We conclude that, unlike earlier claims in the literature, mass transfer through direct impact need not destabilize the binary and that the quantity and sign of the orbital angular momentum transfer depends on the binary properties, particularly the masses of the double white dwarf binary component stars. This stabilization may significantly impact the population synthesis calculations of the expected numbers of events/systems for which double white dwarfs may be a progenitor, e.g., Type Ia supernovae, Type.Ia supernovae, and AM CVn.

  11. Sivers function in the quasiclassical approximation

    NASA Astrophysics Data System (ADS)

    Kovchegov, Yuri V.; Sievert, Matthew D.

    2014-03-01

    We calculate the Sivers function in semi-inclusive deep inelastic scattering (SIDIS) and in the Drell-Yan process (DY) by employing the quasiclassical Glauber-Mueller/McLerran-Venugopalan approximation. Modeling the hadron as a large "nucleus" with nonzero orbital angular momentum (OAM), we find that its Sivers function receives two dominant contributions: one contribution is due to the OAM, while another one is due to the local Sivers function density in the nucleus. While the latter mechanism, being due to the "lensing" interactions, dominates at large transverse momentum of the produced hadron in SIDIS or of the dilepton pair in DY, the former (OAM) mechanism is leading in saturation power counting and dominates when the above transverse momenta become of the order of the saturation scale. We show that the OAM channel allows for a particularly simple and intuitive interpretation of the celebrated sign flip between the Sivers functions in SIDIS and DY.

  12. Approximate spacetime symmetries and conservation laws

    E-print Network

    Abraham I Harte

    2008-08-29

    A notion of geometric symmetry is introduced that generalizes the classical concepts of Killing fields and other affine collineations. There is a sense in which flows under these new vector fields minimize deformations of the connection near a specified observer. Any exact affine collineations that may exist are special cases. The remaining vector fields can all be interpreted as analogs of Poincare and other well-known symmetries near timelike worldlines. Approximate conservation laws generated by these objects are discussed for both geodesics and extended matter distributions. One example is a generalized Komar integral that may be taken to define the linear and angular momenta of a spacetime volume as seen by a particular observer. This is evaluated explicitly for a gravitational plane wave spacetime.

  13. The Cosmology Large Angular Scale Surveyor

    NASA Astrophysics Data System (ADS)

    Marriage, Tobias; Ali, A.; Amiri, M.; Appel, J. W.; Araujo, D.; Bennett, C. L.; Boone, F.; Chan, M.; Cho, H.; Chuss, D. T.; Colazo, F.; Crowe, E.; Denis, K.; Dünner, R.; Eimer, J.; Essinger-Hileman, T.; Gothe, D.; Halpern, M.; Harrington, K.; Hilton, G.; Hinshaw, G. F.; Huang, C.; Irwin, K.; Jones, G.; Karakla, J.; Kogut, A. J.; Larson, D.; Limon, M.; Lowry, L.; Mehrle, N.; Miller, A. D.; Miller, N.; Moseley, S. H.; Novak, G.; Reintsema, C.; Rostem, K.; Stevenson, T.; Towner, D.; U-Yen, K.; Wagner, E.; Watts, D.; Wollack, E.; Xu, Z.; Zeng, L.

    2014-01-01

    Some of the most compelling inflation models predict a background of primordial gravitational waves (PGW) detectable by their imprint of a curl-like "B-mode" pattern in the polarization of the Cosmic Microwave Background (CMB). The Cosmology Large Angular Scale Surveyor (CLASS) is a novel array of telescopes to measure the B-mode signature of the PGW. By targeting the largest angular scales (>2°) with a multifrequency array, novel polarization modulation and detectors optimized for both control of systematics and sensitivity, CLASS sets itself apart in the field of CMB polarization surveys and opens an exciting new discovery space for the PGW and inflation. This poster presents an overview of the CLASS project.

  14. Phenomenological determination of the orbital angular momentum.

    SciTech Connect

    Ramsey, G. P.; High Energy Physics; Loyola Univ.

    2009-01-01

    Measurements involving the gluon spin, {Delta}G(x, t) and the corresponding asymmetry, A(x,t) = {Delta}G(x,t)/G(x,t) play an important role in quantitative understanding of proton structure. We have modeled the asymmetry perturbatively and calculated model corrections to obtain information about non-perturbative spin-orbit effects. These models are consistent with existing COMPASS and HERMES data on the gluon asymmetry. The J{sub z} = 1/2 sum rule is used to generate values of orbital angular momentum at LO and NLO. For models consistent with data, the orbital angular momentum is small. Our studies specify accuracy that future measurements should achieve to constrain theoretical models for nucleon structure.

  15. Phenomenological Determination of the Orbital Angular Momentum

    SciTech Connect

    Ramsey, Gordon P. [Physics Department, Loyola University, Chicago, IL 60626 (United States) and High Energy Physics Division, Argonne National Lab, Argonne, IL 60439 (United States)

    2009-08-04

    Measurements involving the gluon spin, {delta}G(x, t) and the corresponding asymmetry, A(x,t) = {delta}G(x,t)/G(x,t) play an important role in quantitative understanding of proton structure. We have modeled the asymmetry perturbatively and calculated model corrections to obtain information about non-perturbative spin-orbit effects. These models are consistent with existing COMPASS and HERMES data on the gluon asymmetry. The J{sub z} = (1/2) sum rule is used to generate values of orbital angular momentum at LO and NLO. For models consistent with data, the orbital angular momentum is small. Our studies specify accuracy that future measurements should achieve to constrain theoretical models for nucleon structure.

  16. Galactic microwave emission at degree angular scales

    E-print Network

    Angelica de Oliveira-Costa; A. Kogut; Mark J. Devlin; C. Barth Netterfield; Lyman A. Page; Edward J. Wollack

    1997-07-25

    We cross-correlate the Saskatoon Ka and Q-Band Cosmic Microwave Background (CMB) data with different maps to quantify possible foreground contamination. We detect a marginal correlation (2 sigma) with the Diffuse Infrared Background Experiment (DIRBE) 240, 140 and 100 microm maps, but we find no significant correlation with point sources, with the Haslam 408 MHz map or with the Reich and Reich 1420 MHz map. The rms amplitude of the component correlated with DIRBE is about 20% of the CMB signal. Interpreting this component as free-free emission, this normalization agrees with that of Kogut et al. (1996a; 1996b) and supports the hypothesis that the spatial correlation between dust and warm ionized gas observed on large angular scales persists to smaller angular scales. Subtracting this contribution from the CMB data reduces the normalization of the Saskatoon power spectrum by only a few percent.

  17. Angular momentum of optical vortex arrays.

    PubMed

    Courtial, Johannes; Zambrini, Roberta; Dennis, Mark R; Vasnetsov, Mikhail

    2006-01-23

    Guided by the aim to construct light fields with spin-like orbital angular momentum (OAM), that is light fields with a uniform and intrinsic OAM density, we investigate the OAM of arrays of optical vortices with rectangular symmetry. We find that the OAM per unit cell depends on the choice of unit cell and can even change sign when the unit cell is translated. This is the case even if the OAM in each unit cell is intrinsic, that is independent of the choice of measurement axis. We show that spin-like OAM can be found only if the OAM per unit cell vanishes. Our results are applicable to the z component of the angular momentum of any x- and y-periodic momentum distribution in the xy plane, and can also be applied other periodic light beams, arrays of rotating massive objects and periodic motion of liquids. PMID:19503414

  18. Interpolation function for approximating knee joint behavior in human gait

    NASA Astrophysics Data System (ADS)

    Toth-Ta?c?u, Mirela; Pater, Flavius; Stoia, Dan Ioan

    2013-10-01

    Starting from the importance of analyzing the kinematic data of the lower limb in gait movement, especially the angular variation of the knee joint, the paper propose an approximation function that can be used for processing the correlation among a multitude of knee cycles. The approximation of the raw knee data was done by Lagrange polynomial interpolation on a signal acquired using Zebris Gait Analysis System. The signal used in approximation belongs to a typical subject extracted from a lot of ten investigated subjects, but the function domain of definition belongs to the entire group. The study of the knee joint kinematics plays an important role in understanding the kinematics of the gait, this articulation having the largest range of motion in whole joints, in gait. The study does not propose to find an approximation function for the adduction-abduction movement of the knee, this being considered a residual movement comparing to the flexion-extension.

  19. Optimizing the Zeldovich approximation

    NASA Technical Reports Server (NTRS)

    Melott, Adrian L.; Pellman, Todd F.; Shandarin, Sergei F.

    1994-01-01

    We have recently learned that the Zeldovich approximation can be successfully used for a far wider range of gravitational instability scenarios than formerly proposed; we study here how to extend this range. In previous work (Coles, Melott and Shandarin 1993, hereafter CMS) we studied the accuracy of several analytic approximations to gravitational clustering in the mildly nonlinear regime. We found that what we called the 'truncated Zeldovich approximation' (TZA) was better than any other (except in one case the ordinary Zeldovich approximation) over a wide range from linear to mildly nonlinear (sigma approximately 3) regimes. TZA was specified by setting Fourier amplitudes equal to zero for all wavenumbers greater than k(sub nl), where k(sub nl) marks the transition to the nonlinear regime. Here, we study the cross correlation of generalized TZA with a group of n-body simulations for three shapes of window function: sharp k-truncation (as in CMS), a tophat in coordinate space, or a Gaussian. We also study the variation in the crosscorrelation as a function of initial truncation scale within each type. We find that k-truncation, which was so much better than other things tried in CMS, is the worst of these three window shapes. We find that a Gaussian window e(exp(-k(exp 2)/2k(exp 2, sub G))) applied to the initial Fourier amplitudes is the best choice. It produces a greatly improved crosscorrelation in those cases which most needed improvement, e.g. those with more small-scale power in the initial conditions. The optimum choice of kG for the Gaussian window is (a somewhat spectrum-dependent) 1 to 1.5 times k(sub nl). Although all three windows produce similar power spectra and density distribution functions after application of the Zeldovich approximation, the agreement of the phases of the Fourier components with the n-body simulation is better for the Gaussian window. We therefore ascribe the success of the best-choice Gaussian window to its superior treatment of phases in the nonlinear regime. We also report on the accuracy of particle positions and velocities produced by TZA.

  20. Quantized angular momenta in the laser gyro

    SciTech Connect

    Wolf, E.L.

    1982-07-01

    A brief discussion is presented of the operation of the traveling-wave ring laser as a sensor of rotation. The description, based on the azimuthal probability function P(phi) associated with a linear combination of oppositely directed and conserved angular momenta L/sub z/ = +- mh, is free of certain restrictions inherent in the conventional treatment, as well as providing a simple and transparent picture of the physical origin of gyroscopic action.(AIP)

  1. Angular Momentum Control in Coordinated Behaviors

    Microsoft Academic Search

    Victor B. Zordan

    2010-01-01

    \\u000a This paper explores the many uses of angular momentum regulation and its role in the synthesis of coordinated motion generated\\u000a with physically based characters. Previous investigations in biomechanics, robotics, and animation are discussed and a straightforward\\u000a organization is described for distinguishing the needs and control approaches of various behaviors including stepping, walking\\u000a and standing balance. Emphasis is placed on creating

  2. Angular momentum quantization from Planck's energy quantization

    E-print Network

    J. H. O. Sales; A. T. Suzuki; D. S. Bonafe

    2007-09-26

    We present in this work a pedagogical way of quantizing the atomic orbit for the hydrogen's atom model proposed by Bohr without using his hypothesis of angular momentum quantization. In contrast to the usual treatment for the orbital quantization, we show that using energy conservation, correspondence principle and Plank's energy quantization Bohr's hypothesis can be deduced from and is a consequence of the Planck's energy quantization.

  3. Angular resolved light scattering for discriminating among marine picoplankton

    E-print Network

    Jaffe, Jules

    Angular resolved light scattering for discriminating among marine picoplankton: modeling, both simulations and experiments of angular resolved light scattering (ARLS) were performed. After of an elliptical mirror, a rotating aperture, and a PMT. Scattered light was recorded with adequate signal

  4. Proper equation for angular momentum of trailing vortices

    Microsoft Academic Search

    Mahinder S. Uberoi

    1977-01-01

    It is shown that the invariably neglected radial convection and the associated axial convection of angular momentum are the most important terms in the equation for the change of angular momentum of a trailing vortex.

  5. A gear rattle metric based on the wavelet multi-resolution analysis: Experimental investigation

    NASA Astrophysics Data System (ADS)

    Brancati, Renato; Rocca, Ernesto; Savino, Sergio

    2015-01-01

    In the article an investigation about the feasibility of a wavelet analysis for gear rattle metric in transmission gears, due to tooth impacts under unloaded conditions, is conducted. The technique adopts the discrete wavelet transform (DWT), following the Multi-resolution analysis, to decompose an experimental signal of the relative angular motion of gears into an approximation and in some detail vectors. The described procedure, previously developed by the authors, permits the qualitative evaluation of the impacts occurring between the teeth by examining in particular the detail vectors coming out from the wavelet decomposition. The technique enables discriminating between the impacts occurring on the two different sides of tooth. This situation is typical of the double-sided gear rattle produced in the automotive gear boxes. This paper considers the influence of oil lubricant, inserted between the teeth, in reducing the impacts. Analysis is performed by comparing three different lubrication conditions, and some of the classical wavelet functions adopted in literature are tested as "mother" wavelet. Moreover, comparisons with a metric based on the harmonic analysis by means of the Fast Fourier Transform (FFT), often adopted in this field, are conducted to put in evidence the advantages of the Wavelet technique with reference to the influence of some fundamental operative parameters. The experimental signals of the relative angular rotation of gear are acquired by two high resolution incremental encoders on a specific test rig for lightly loaded gears. The results of the proposed method appear optimistic also in the detection of defects that could produce little variations in the dynamic behavior of unloaded gears.

  6. Optical angular momentum in a rotating frame.

    PubMed

    Speirits, Fiona C; Lavery, Martin P J; Padgett, Miles J; Barnett, Stephen M

    2014-05-15

    It is well established that light carrying orbital angular momentum (OAM) can be used to induce a mechanical torque causing an object to spin. We consider the complementary scenario: will an observer spinning relative to the beam axis measure a change in OAM as a result of their rotational velocity? Remarkably, although a linear Doppler shift changes the linear momentum of a photon, the angular Doppler shift induces no change in the angular momentum. Further, we examine the rotational Doppler shift in frequency imparted to the incident light due to the relative motion of the beam with respect to the observer and consider what must happen to the measured wavelength if the speed of light c is to remain constant. We show specifically that the OAM of the incident beam is not affected by the rotating observer and that the measured wavelength is shifted by a factor equal and opposite to that of the frequency shift induced by the rotational Doppler effect. PMID:24978243

  7. Variational truncated Wigner approximation.

    PubMed

    Sels, Dries; Brosens, Fons

    2014-04-01

    In this paper we reconsider the notion of an optimal effective Hamiltonian for the semiclassical propagation of the Wigner distribution in phase space. An explicit expression for the optimal effective Hamiltonian is obtained in the short-time limit by minimizing the Hilbert-Schmidt distance between the semiclassical approximation and the real state of the system. The method is illustrated for the quartic oscillator. PMID:24827193

  8. Approximate Non-interference

    Microsoft Academic Search

    Alessandra Di Pierro; Chris Hankin; Herbert Wiklicky

    2004-01-01

    We address the problem of characterising the security of a program,against unauthorised information flows. Classical approaches,are based on non-interference models which depend,ultimately on the notion of process equivalence. In these models confidentiality is an absolute property statin g the absence of any illegal information flow. We present a model,in which the notion of non-interference is approximated in the sense that

  9. Angular momentum redistribution and the evolution and morphology of bars

    E-print Network

    E. Athanassoula

    2003-02-25

    Angular momentum exchange is a driving process for the evolution of barred galaxies. Material at resonance in the bar region loses angular momentum which is taken by material at resonance in the outer disc and/or the halo. By losing angular momentum, the bar grows stronger and slows down. This evolution scenario is backed by both analytical calculations and by $N$-body simulations. The morphology of the bar also depends on the amount of angular momentum exchanged.

  10. Measuring the angular momentum distribution in core-collapse supernova progenitors with gravitational waves

    NASA Astrophysics Data System (ADS)

    Abdikamalov, Ernazar; Gossan, Sarah; DeMaio, Alexandra M.; Ott, Christian D.

    2014-08-01

    The late collapse, core bounce, and the early postbounce phase of rotating core collapse leads to a characteristic gravitational wave (GW) signal. The precise shape of the signal is governed by the interplay of gravity, rotation, nuclear equation of state (EOS), and electron capture during collapse. We explore the detailed dependence of the signal on total angular momentum and its distribution in the progenitor core by means of a large set of axisymmetric general-relativistic hydrodynamics core-collapse simulations, in which we systematically vary the initial angular momentum distribution in the core. Our simulations include a microphysical finite-temperature EOS, an approximate electron capture treatment during collapse, and a neutrino leakage scheme for the postbounce evolution. Our results show that the total angular momentum of the inner core at bounce and the inner core's ratio of rotational kinetic energy to gravitational energy T/|W| are both robust parameters characterizing the GW signal. We find that the precise distribution of angular momentum is relevant only for very rapidly rotating cores with T/|W|?8% at bounce. We construct a numerical template bank from our baseline set of simulations, and carry out additional simulations to generate trial waveforms for injection into simulated Advanced LIGO noise at a fiducial galactic distance of 10 kpc. Using matched filtering, we show that for an optimally oriented source and Gaussian noise, Advanced LIGO could measure the total angular momentum to within ±20%, for rapidly rotating cores. For most waveforms, the nearest known degree of precollapse differential rotation is correctly inferred by both our matched filtering analysis and an alternative Bayesian model selection approach. We test our results for robustness against systematic uncertainties by injecting waveforms from simulations utilizing a different EOS and variations in the electron fraction in the inner core. The results of these tests show that these uncertainties significantly reduce the accuracy with which the total angular momentum and its precollapse distribution can be inferred from observations.

  11. Angular momentum redistribution by mixed modes in evolved low-mass stars. I. Theoretical formalism

    NASA Astrophysics Data System (ADS)

    Belkacem, K.; Marques, J. P.; Goupil, M. J.; Sonoi, T.; Ouazzani, R. M.; Dupret, M. A.; Mathis, S.; Mosser, B.; Grosjean, M.

    2015-07-01

    Seismic observations by the space-borne mission Kepler have shown that the core of red giant stars slows down while evolving, requiring an efficient physical mechanism to extract angular momentum from the inner layers. Current stellar evolution codes fail to reproduce the observed rotation rates by several orders of magnitude and instead predict a drastic spin-up of red giant cores. New efficient mechanisms of angular momentum transport are thus required. In this framework, our aim is to investigate the possibility that mixed modes extract angular momentum from the inner radiative regions of evolved low-mass stars. To this end, we consider the transformed Eulerian mean (TEM) formalism, which allows us to consider the combined effect of both the wave momentum flux in the mean angular momentum equation and the wave heat flux in the mean entropy equation as well as their interplay with the meridional circulation. In radiative layers of evolved low-mass stars, the quasi-adiabatic approximation, the limit of slow rotation, and the asymptotic regime can be applied for mixed modes and enable us to establish a prescription for the wave fluxes in the mean equations. The formalism is finally applied to a 1.3 M? benchmark model, representative of observed CoRoT and Kepler oscillating evolved stars. We show that the influence of the wave heat flux on the mean angular momentum is not negligible and that the overall effect of mixed modes is to extract angular momentum from the innermost region of the star. A quantitative and accurate estimate requires realistic values of mode amplitudes. This is provided in a companion paper. Appendix A is available in electronic form at http://www.aanda.org

  12. Femtolensing: Beyond the semiclassical approximation

    NASA Technical Reports Server (NTRS)

    Ulmer, Andrew; Goodman, Jeremy

    1995-01-01

    Femtolensoing is a gravitational lensing effect in which the magnification is a function not only of the position and sizes of the source and lens, but also of the wavelength of light. Femtolensing is the only known effect of 10(exp -13) - 10(exp -16) solar mass) dark-matter objects and may possibly be detectable in cosmological gamma-ray burst spectra. We present a new and efficient algorithm for femtolensing calculation in general potentials. The physical optics results presented here differ at low frequencies from the semiclassical approximation, in which the flux is attributed to a finite number of mutually coherent images. At higher frequencies, our results agree well with the semicalssical predictions. Applying our method to a point-mass lens with external shear, we find complex events that have structure at both large and small spectral resolution. In this way, we show that femtolensing may be observable for lenses up to 10(exp -11) solar mass, much larger than previously believed. Additionally, we discuss the possibility of a search femtolensing of white dwarfs in the Large Magellanic Cloud at optical wavelengths.

  13. On the Relationship between Inertial Instability, Angular Momentum, and Jet flare-ups

    NASA Astrophysics Data System (ADS)

    Rowe, S. M.; Hitchman, M.

    2014-12-01

    A diagnostic study is conducted to determine the mechanisms involved in local jet accelerations and altered meridional circulation patterns associated with midlatitude cyclones. Regions of inertial instability, as they travel poleward and eastward through the sub-polar westerly jet, are analyzed, and the associated jet intensifications are the main features of interest. Streamfunction patterns and jet accelerations are driven by local regions of inertial instability. As air with negative potential vorticity (PV) moves upward and poleward from the surface it transports air from a lower latitude with higher angular momentum into the jet. The original speed of the air must increase as it moves poleward to conserve angular momentum. During inertial instability-driven poleward surges of absolute momentum a distinct increase in jet wind speed occurs. High resolution simulations with the University of Wisconsin Non-Hydrostatic Modeling System (UWNMS) show that the conformal agreement between the shapes of surfaces of inertial instability, angular momentum, and jet structure is remarkable, and that the nature of the jet downstream of a trough is consistent with simple poleward advection of high angular momentum. Mesoscale disturbances precisely rooted in regions of inertial instability create a jet-suturing effect, a possible new mechanism for merging the sub-polar and sub-tropical jets.

  14. Polarization-Dependent Measurements of Molecular Super Rotors with Oriented Angular Momenta

    NASA Astrophysics Data System (ADS)

    Murray, Matthew J.; Toro, Carlos; Liu, Qingnan; Mullin, Amy S.

    2014-05-01

    Controlling molecular motion would enable manipulation of energy flow between molecules. Here we have used an optical centrifuge to investigate energy transfer between molecular super rotors with oriented angular momenta. The polarizable electron cloud of the molecules interacts with the electric field of linearly polarized light that angularly accelerates over the time of the optical pulse. This process drives molecules into high angular momentum states that are oriented with the optical field and have energies far from equilibrium. High resolution transient IR spectroscopy reveals the dynamics of collisional energy transfer for these super excited rotors. The results of this study leads to a more fundamental understanding of energy balance in non-equilibrium environments and the physical and chemical properties of gases in a new regime of energy states. Results will be presented for several super rotor species including carbon monoxide, carbon dioxide, and acetylene. Polarization-dependent measurements reveal the extent to which the super rotors maintain spatial orientation of high angular momentum states.

  15. Extreme nonlinear optical processes with beams carrying orbital angular momentum

    NASA Astrophysics Data System (ADS)

    Kern, C.; Zürch, M.; Hansinger, P.; Dreischuh, A.; Spielmann, Ch.

    2014-03-01

    Light beams carrying an isolated point singularity with a screw-type phase distribution are called an optical vortex (OV). The fact that in free space the Poynting vector of the beam gives the momentum flow leads to an orbital angular momentum (OAM) of the photons in such a singular beam, independent on the spin angular momentun1. There are many applications of optical OAM shown in literature that would benefit from the availability of optical vortex beams in all spectral regions. For example it was shown that transitions forbidden by selection rules in dipole approximation appear allowed when using photons with the additional degree of freedom of optical OAM2. However, the common techniques of producing new light frequencies by nonlinear optical processes seem problematic in conserving the optical vortex when the nonlinearity becomes large. We show that with the extremely nonlinear process of High Harmonic Generation (HHG) it is possible to transfer OVs from the near-infrared to the extreme ultraviolet (XUV)3 at wavelengths down to ~30 nm. The observed XUV light was examined spatially and spectrally. The spatial profile showed the expected singular behavior, a dark region in the center. A comparison of the far-field fringe pattern caused by a thin wire with corresponding simulations suggests that the XUV vortex beam carries a unit topological charge. A screw-like phase evolution around the profile was also verified by employing a Hartmann type measurement. The generated spectrum revealed that in all Harmonic orders an OV was present. The profile, however, looked the same in all orders, indicating identical topological charge, which runs counterintuitive to the assumption that the phase of exp(-il?) is multiplied by the harmonic order in a frequency up-conversion experiment.

  16. Angularly-resolved elastic light scattering of micro-particles

    NASA Astrophysics Data System (ADS)

    Aptowicz, Kevin B.

    From microbiology to astrophysics, the scientific community has long embraced elastic light scattering from small particles as a diagnostic tool. Elastic light scattering has an extremely large scattering cross-section, allowing for single particle interrogation. This is critical in applications where trace amounts of suspect particles are to be detected in a diverse background of natural aerosols. By angularly-resolving the elastically scattered light, features can be detected in these patterns that are sensitive to a particle's morphology (shape, size, internal structure, and composition). An apparatus to collect LA TAOS (Large-Angle Two-dimensional Angular Optical Scattering) patterns from single particles in-situ and in real-time was designed and constructed. The setup utilizes a cross-beam trigger system to minimize the effects of the aberration coma stemming from the main collection optic, an ellipsoidal mirror. LA TAOS patterns of ambient aerosols were collected and analyzed. Approximately 15% of the ambient aerosol had a sphere-like shape. The refractive index of these spheres was estimated by curve-fitting to Lorenz-Mie theory. In addition, the island features prevalent in the LA TAOS pattern were analyzed. Metrics generated from these were used to get partial discrimination between clusters of Bacillus subtilis spores (a simulant for anthrax) and aerosol particles found in the ambient atmosphere. A novel experimental setup for collecting simultaneously LA TAOS patterns at two wavelengths in the mid-infrared was also implemented. With this setup, the relative strength of single-particle absorption could be discerned at the two illuminating wavelengths.

  17. Angular Momentum Regulation during Human Walking: Biomechanics and Control

    E-print Network

    Williams, Brian C.

    : BIOMECHANICS A. Spin Angular Momentum and Resulting Whole Body Angular Excursions during Human WalkingAngular Momentum Regulation during Human Walking: Biomechanics and Control Marko Popovic & Andreas by biomechanical studies on human walking, we present a control strategy for biologically realistic walking based

  18. Two Dimensions Angular Sensor for Micro\\/Nano Measurement

    Microsoft Academic Search

    Qinggang Liul; Yiping Li; Wenyong Zhao; Xiaotang Hu

    2007-01-01

    An optical non-contact and compact two dimensions angular sensor for micro angle measurement and nanometer scale measurement is introduced in the paper. The light beam emits from the angular sensor to the micro target and then is reflected back into the sensor. The angular sensor is designed based on optical differential method which adopts two orthogonal optical inner-reflection critical angle

  19. Attitude Control without Angular Velocity Measurement: A Passivity Approach

    Microsoft Academic Search

    Fernando C. Lizarralde; John T. Wen

    1995-01-01

    It is well known that the linear feedback of the quarternion of the attitude error and angular velocity globally stabilizes the attitude of a rigid body. In this note, we show that the angular velocity feedback can be replaced by a nonlinear filter of the quarternion, thus removing the need of direct angular velocity measurement. In contrast to other approaches,

  20. ANGULAR MOMENTUM: AN APPROACH TO COMBINATORIAL SPACE-TIME

    E-print Network

    Baez, John

    ANGULAR MOMENTUM: AN APPROACH TO COMBINATORIAL SPACE-TIME ROGER PENROSE I want to describe an idea is connected with the structure of space-time in a very intimate way, is in angular momentum. The idea here, then, is to start with the concept of angular momentum-- here one has a discrete spectrum--and use

  1. Realization of natural dynamic walking using the angular momentum information

    Microsoft Academic Search

    A. Sano; Junji Furusho

    1990-01-01

    In biped locomotion systems, the angular momentum of the whole system can be taken as a good index, as seen from the law of conservation of angular momentum. A control method which divides the walking into motions in the sagittal plane and in the lateral plane has been adopted. For motion in the sagittal plane, the angular momentum is placed

  2. Polarization control of single photon quantum orbital angular momentum

    E-print Network

    Roma "La Sapienza", Università di

    Polarization control of single photon quantum orbital angular momentum states E. Nagali1, F, Italy Abstract: The orbital angular momentum of photons, being defined in an infinite angular momentum of single photons and vice versa. All our schemes exploit a newly developed optical

  3. Angular momentum and the polar basis of harmonic oscillator

    E-print Network

    Paris-Sud XI, Université de

    1 Angular momentum and the polar basis of harmonic oscillator M. Hage-Hassan Université Libanaise for angular momentum but with the polar basis of harmonic oscillator as a starting point. We derive by a new momentum. 1-Introduction The theory of angular momentum occupies an important position in the development

  4. On the angular momentum of a system of quantum particles

    E-print Network

    On the angular momentum of a system of quantum particles O. Chavoya-Aceves Glendale Community College, Phoenix, AZ, USA chavoyao@gmail.com August 22, 2014 Abstract The properties of angular momentum experiment and gauge invariance. The separation of angular momentum of a quantum system of particles

  5. Quantised Angular Momentum Vectors and Projection Angle Distributions for Discrete

    E-print Network

    Boyer, Edmond

    Quantised Angular Momentum Vectors and Projection Angle Distributions for Discrete Radon that result from the quantisation of angular momentum (QAM) vectors may provide an alternative way to select on Discrete Geometry for Computer Imagery, Szeged : Hungary (2006)" #12;Quantised Angular Momentum Vectors

  6. Approximation of Time-Dependent, Viscoelastic Fluid Flow: SUPG Approximation

    E-print Network

    Ervin, Vincent J.

    Approximation of Time-Dependent, Viscoelastic Fluid Flow: SUPG Approximation Vincent J. Ervin equations with an Oldroyd B constitutive equation. The approximation is stabilized by using a SUPG, the numerical approximations. Key words. viscoelasticity, finite element method, fully discrete, SUPG AMS

  7. Approximation of Time-Dependent Viscoelastic Fluid Flow: SUPG Approximation

    Microsoft Academic Search

    Vincent J. Ervin; William W. Miles

    2003-01-01

    In this article we consider the numerical approximation to the time dependent vis- coelasticity equations with an Oldroyd B constitutive equation. The approximation is stabilized by using a SUPG approximation for the constitutive equation. We analyse both the semi-discrete and fully discrete numerical approximations. For both discretizations we prove the existence of, and derive a priori error estimates for, the

  8. Toward Approximate Moving Least Squares Approximation with Irregularly Spaced

    E-print Network

    Heller, Barbara

    -order moving least squares approximations. In this paper we focus our interest on practical implementationsToward Approximate Moving Least Squares Approximation with Irregularly Spaced Centers Gregory E.S.A. Abstract By combining the well known moving least squares approximation method and the theory

  9. Resolution limits for wave equation imaging

    NASA Astrophysics Data System (ADS)

    Huang, Yunsong; Schuster, Gerard T.

    2014-08-01

    Formulas are derived for the resolution limits of migration-data kernels associated with diving waves, primary reflections, diffractions, and multiple reflections. They are applicable to images formed by reverse time migration (RTM), least squares migration (LSM), and full waveform inversion (FWI), and suggest a multiscale approach to iterative FWI based on multiscale physics. That is, at the early stages of the inversion, events that only generate low-wavenumber resolution should be emphasized relative to the high-wavenumber resolution events. As the iterations proceed, the higher-resolution events should be emphasized. The formulas also suggest that inverting multiples can provide some low- and intermediate-wavenumber components of the velocity model not available in the primaries. Finally, diffractions can provide twice or better the resolution than specular reflections for comparable depths of the reflector and diffractor. The width of the diffraction-transmission wavepath is approximately ? at the diffractor location for the diffraction-transmission wavepath.

  10. Approximate option pricing

    SciTech Connect

    Chalasani, P.; Saias, I. [Los Alamos National Lab., NM (United States); Jha, S. [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    1996-04-08

    As increasingly large volumes of sophisticated options (called derivative securities) are traded in world financial markets, determining a fair price for these options has become an important and difficult computational problem. Many valuation codes use the binomial pricing model, in which the stock price is driven by a random walk. In this model, the value of an n-period option on a stock is the expected time-discounted value of the future cash flow on an n-period stock price path. Path-dependent options are particularly difficult to value since the future cash flow depends on the entire stock price path rather than on just the final stock price. Currently such options are approximately priced by Monte carlo methods with error bounds that hold only with high probability and which are reduced by increasing the number of simulation runs. In this paper the authors show that pricing an arbitrary path-dependent option is {number_sign}-P hard. They show that certain types f path-dependent options can be valued exactly in polynomial time. Asian options are path-dependent options that are particularly hard to price, and for these they design deterministic polynomial-time approximate algorithms. They show that the value of a perpetual American put option (which can be computed in constant time) is in many cases a good approximation to the value of an otherwise identical n-period American put option. In contrast to Monte Carlo methods, the algorithms have guaranteed error bounds that are polynormally small (and in some cases exponentially small) in the maturity n. For the error analysis they derive large-deviation results for random walks that may be of independent interest.

  11. Efficient polynomial L -approximations

    E-print Network

    Brisebarre, Nicolas

    Dr P. Michelon, 42023 St-´Etienne Cedex 02 and Projet Ar´enaire, LIP, 46 all´ee d'Italie, 69364 Lyon are the supremum norm (or L norm or absolute error) ||p - f||,[a,b] = sup axb |p(x) - f(x)|, or the relative error ||p - f||rel,[a,b] = sup axb 1 |f(x)| |p(x) - f(x)| or least squares approximations norm ||p-f||2,[a,b

  12. Angular distribution in two-particle emission induced by neutrinos and electrons

    NASA Astrophysics Data System (ADS)

    Simo, I. Ruiz; Albertus, C.; Amaro, J. E.; Barbaro, M. B.; Caballero, J. A.; Donnelly, T. W.

    2014-09-01

    The angular distribution of the phase space arising in two-particle emission reactions induced by electrons and neutrinos is computed in the laboratory (Lab) system by boosting the isotropic distribution in the center of mass (CM) system used in Monte Carlo generators. The Lab distribution has a singularity for some angular values, coming from the Jacobian of the angular transformation between CM and Lab systems. We recover the formula we obtained in a previous calculation for the Lab angular distribution. This is in accordance with the Monte Carlo method used to generate two-particle events for neutrino scattering [J. T. Sobczyk, Phys. Rev. C 86, 015504 (2012)]. Inversely, by performing the transformation to the CM system, it can be shown that the phase-space function, which is proportional to the two-particle-two-hole (2p-2h) hadronic tensor for a constant current operator, can be computed analytically in the frozen nucleon approximation, if Pauli blocking is absent. The results in the CM frame confirm our previous work done using an alternative approach in the Lab frame. The possibilities of using this method to compute the hadronic tensor by a boost to the CM system are analyzed.

  13. Local measurements of turbulent angular momentum transport in circular Couette flow

    NASA Astrophysics Data System (ADS)

    Burin, M. J.; Schartman, E.; Ji, H.

    2010-05-01

    We report on velocity fluctuations and the fluctuation-driven radial transport of angular momentum in turbulent circular Couette flow. Our apparatus is short (cylinder height to gap width ratio ? ~ 2) and of relatively high wall curvature (ratio of cylinder radii ? ~ 0.35). Fluctuation levels and the mean specific angular momentum are found to be roughly constant over radius, in accordance with previous studies featuring narrower gaps. Synchronized dual beam Laser Doppler Velocimetry (2D LDV) is used to directly measure the r - ? Reynolds stress component as a function of Reynolds number ( Re), revealing approximate scalings in the non-dimensional angular momentum transport that confirm previous measurements of torque in similar flows. 2D LDV further allows for a decomposition of the turbulent transport to assess the relative roles of fluctuation intensity and r - ? cross-correlation. We find that the increasing angular momentum transport with Re is due to intensifying absolute fluctuation levels accompanied by a slightly weakening cross-correlation.

  14. Non-contact measurement of an object's angular position by means of laser goniometer

    NASA Astrophysics Data System (ADS)

    Filatov, Yu. V.; Nikolaev, M. S.; Pavlov, P. A.; Venediktov, V. Y.

    2014-10-01

    The report presents results of analysis and experimental research of the laser goniometer in the mode of operation - noncontact measurements of an object's angular position. An important feature of this mode is an extremely large range of measurement with high accuracy. With the usual resolution of about 0,1 arcs the laser goniometer has in this mode of operation an essential advantage against photo-electric autocollimators with their rather small measuring range. Obtained results confirm that the laser dynamic goniometer using in the mode of non-contact measurement of an object's angular position can be characterized by the range of angle measurements up to 15…20 deg and accuracy of constant angles on the level 0,05…0,1 arcs. The error of angles changing in time has additional components on the level of 0,2 arcs connected with influence of optical polygon face unflatness and difficulties of use the statistical averaging of measurement results.

  15. Characterization of the angular memory effect of scattered light in biological tissues.

    PubMed

    Schott, Sam; Bertolotti, Jacopo; Léger, Jean-Francois; Bourdieu, Laurent; Gigan, Sylvain

    2015-05-18

    High resolution optical microscopy is essential in neuroscience but suffers from scattering in biological tissues and therefore grants access to superficial brain layers only. Recently developed techniques use scattered photons for imaging by exploiting angular correlations in transmitted light and could potentially increase imaging depths. But those correlations ('angular memory effect') are of a very short range and should theoretically be only present behind and not inside scattering media. From measurements on neural tissues and complementary simulations, we find that strong forward scattering in biological tissues can enhance the memory effect range and thus the possible field-of-view by more than an order of magnitude compared to isotropic scattering for ?1 mm thick tissue layers. PMID:26074598

  16. Characterization of the angular memory effect of scattered light in biological tissues

    E-print Network

    Schott, Sam; Léger, Jean-Francois; Bourdieu, Laurent; Gigan, Sylvain

    2015-01-01

    High resolution optical microscopy is essential in neuroscience but suffers from scattering in biological tissues. It therefore grants access to superficial layers only. Recently developed techniques use scattered photons for imaging by exploiting angular correlations in transmitted light and could potentially increase imaging depths. But those correlations (`angular memory effect') are of very short range and, in theory, only present behind and not inside scattering media. From measurements on neural tissues and complementary simulations, we find that strong forward scattering in biological tissues can enhance the memory effect range (and thus the possible field-of-view) by more than an order of magnitude compared to isotropic scattering for $\\sim$1\\,mm thick tissue layers.

  17. Image Resolution Enhancement using Wavelet Domain Hidden Markov Tree and Coefficient Sign Estimation

    Microsoft Academic Search

    Alptekin Temizel

    2007-01-01

    Image resolution enhancement using wavelets is a relatively new subject and many new algorithms have been proposed recently. These algorithms assume that the low resolution image is the approximation subband of a higher resolution image and attempts to estimate the unknown detail coefficients to reconstruct a high resolution image. A subset of these recent approaches utilized probabilistic models to estimate

  18. Simulation of LANDSAT multispectral scanner spatial resolution with airborne scanner data

    NASA Technical Reports Server (NTRS)

    Hlavka, C. A.

    1986-01-01

    A technique for simulation of low spatial resolution satellite imagery by using high resolution scanner data is described. The scanner data is convolved with the approximate point spread function of the low resolution data and then resampled to emulate low resolution imagery. The technique was successfully applied to Daedalus airborne scanner data to simulate a portion of a LANDSAT multispectra scanner scene.

  19. ANGULAR MOMENTUM AND GALAXY FORMATION REVISITED

    SciTech Connect

    Romanowsky, Aaron J. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Fall, S. Michael [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2012-12-15

    Motivated by a new wave of kinematical tracers in the outer regions of early-type galaxies (ellipticals and lenticulars), we re-examine the role of angular momentum in galaxies of all types. We present new methods for quantifying the specific angular momentum j, focusing mainly on the more challenging case of early-type galaxies, in order to derive firm empirical relations between stellar j{sub *} and mass M{sub *} (thus extending earlier work by Fall). We carry out detailed analyses of eight galaxies with kinematical data extending as far out as 10 effective radii, and find that data at two effective radii are generally sufficient to estimate total j{sub *} reliably. Our results contravene suggestions that ellipticals could harbor large reservoirs of hidden j{sub *} in their outer regions owing to angular momentum transport in major mergers. We then carry out a comprehensive analysis of extended kinematic data from the literature for a sample of {approx}100 nearby bright galaxies of all types, placing them on a diagram of j{sub *} versus M{sub *}. The ellipticals and spirals form two parallel j{sub *}-M{sub *} tracks, with log-slopes of {approx}0.6, which for the spirals are closely related to the Tully-Fisher relation, but for the ellipticals derives from a remarkable conspiracy between masses, sizes, and rotation velocities. The ellipticals contain less angular momentum on average than spirals of equal mass, with the quantitative disparity depending on the adopted K-band stellar mass-to-light ratios of the galaxies: it is a factor of {approx}3-4 if mass-to-light ratio variations are neglected for simplicity, and {approx}7 if they are included. We decompose the spirals into disks and bulges and find that these subcomponents follow j{sub *}-M{sub *} trends similar to the overall ones for spirals and ellipticals. The lenticulars have an intermediate trend, and we propose that the morphological types of galaxies reflect disk and bulge subcomponents that follow separate, fundamental j{sub *}-M{sub *} scaling relations. This provides a physical motivation for characterizing galaxies most basically with two parameters: mass and bulge-to-disk ratio. Next, in an approach complementary to numerical simulations, we construct idealized models of angular momentum content in a cosmological context, using estimates of dark matter halo spin and mass from theoretical and empirical studies. We find that the width of the halo spin distribution cannot account for the differences between spiral and elliptical j{sub *}, but that the observations are reproduced well if these galaxies simply retained different fractions of their initial j complement ({approx}60% and {approx}10%, respectively). We consider various physical mechanisms for the simultaneous evolution of j{sub *} and M{sub *} (including outflows, stripping, collapse bias, and merging), emphasizing that the vector sum of all such processes must produce the observed j{sub *}-M{sub *} relations. We suggest that a combination of early collapse and multiple mergers (major or minor) may account naturally for the trend for ellipticals. More generally, the observed variations in angular momentum represent simple but fundamental constraints for any model of galaxy formation.

  20. Resolutions of the Coulomb Operator

    NASA Astrophysics Data System (ADS)

    Gill, Peter

    2007-03-01

    The ``Resolution of the Identity Operator'' I ?| ?n>= through the introduction of an infinite complete expansion basis ?n. In practical implementations, where the basis set is finite and incomplete, (2) yields systematic approximations to difficult overlap integrals and is widely used in quantum physics and chemistry. We will present an analogous ``Resolution of the Coulomb Operator'' r12-1 ?| ?n>= and we will discuss the potential utility of (4) in the efficient treatment of the matrix elements that arise in quantum chemistry and elsewhere.

  1. Whole-body angular momentum during stair ascent and descent.

    PubMed

    Silverman, Anne K; Neptune, Richard R; Sinitski, Emily H; Wilken, Jason M

    2014-04-01

    The generation of whole-body angular momentum is essential in many locomotor tasks and must be regulated in order to maintain dynamic balance. However, angular momentum has not been investigated during stair walking, which is an activity that presents a biomechanical challenge for balance-impaired populations. We investigated three-dimensional whole-body angular momentum during stair ascent and descent and compared it to level walking. Three-dimensional body-segment kinematic and ground reaction force (GRF) data were collected from 30 healthy subjects. Angular momentum was calculated using a 13-segment whole-body model. GRFs, external moment arms and net joint moments were used to interpret the angular momentum results. The range of frontal plane angular momentum was greater for stair ascent relative to level walking. In the transverse and sagittal planes, the range of angular momentum was smaller in stair ascent and descent relative to level walking. Significant differences were also found in the ground reaction forces, external moment arms and net joint moments. The sagittal plane angular momentum results suggest that individuals alter angular momentum to effectively counteract potential trips during stair ascent, and reduce the range of angular momentum to avoid falling forward during stair descent. Further, significant differences in joint moments suggest potential neuromuscular mechanisms that account for the differences in angular momentum between walking conditions. These results provide a baseline for comparison to impaired populations that have difficulty maintaining dynamic balance, particularly during stair ascent and descent. PMID:24636222

  2. Approximate Bayesian Computation

    PubMed Central

    Sunnåker, Mikael; Corander, Jukka; Foll, Matthieu; Dessimoz, Christophe

    2013-01-01

    Approximate Bayesian computation (ABC) constitutes a class of computational methods rooted in Bayesian statistics. In all model-based statistical inference, the likelihood function is of central importance, since it expresses the probability of the observed data under a particular statistical model, and thus quantifies the support data lend to particular values of parameters and to choices among different models. For simple models, an analytical formula for the likelihood function can typically be derived. However, for more complex models, an analytical formula might be elusive or the likelihood function might be computationally very costly to evaluate. ABC methods bypass the evaluation of the likelihood function. In this way, ABC methods widen the realm of models for which statistical inference can be considered. ABC methods are mathematically well-founded, but they inevitably make assumptions and approximations whose impact needs to be carefully assessed. Furthermore, the wider application domain of ABC exacerbates the challenges of parameter estimation and model selection. ABC has rapidly gained popularity over the last years and in particular for the analysis of complex problems arising in biological sciences (e.g., in population genetics, ecology, epidemiology, and systems biology). PMID:23341757

  3. Mass and Angular Momentum in General Relativity

    E-print Network

    J. L. Jaramillo; E. Gourgoulhon

    2010-04-30

    We present an introduction to mass and angular momentum in General Relativity. After briefly reviewing energy-momentum for matter fields, first in the flat Minkowski case (Special Relativity) and then in curved spacetimes with or without symmetries, we focus on the discussion of energy-momentum for the gravitational field. We illustrate the difficulties rooted in the Equivalence Principle for defining a local energy-momentum density for the gravitational field. This leads to the understanding of gravitational energy-momentum and angular momentum as non-local observables that make sense, at best, for extended domains of spacetime. After introducing Komar quantities associated with spacetime symmetries, it is shown how total energy-momentum can be unambiguously defined for isolated systems, providing fundamental tests for the internal consistency of General Relativity as well as setting the conceptual basis for the understanding of energy loss by gravitational radiation. Finally, several attempts to formulate quasi-local notions of mass and angular momentum associated with extended but finite spacetime domains are presented, together with some illustrations of the relations between total and quasi-local quantities in the particular context of black hole spacetimes. This article is not intended to be a rigorous and exhaustive review of the subject, but rather an invitation to the topic for non-experts. In this sense we follow essentially the expositions in Szabados 2004, Gourgoulhon 2007, Poisson 2004 and Wald 84, and refer the reader interested in further developments to the existing literature, in particular to the excellent and comprehensive review by Szabados (2004).

  4. Angular Rate Estimation Using a Distributed Set of Accelerometers

    PubMed Central

    Park, Sungsu; Hong, Sung Kyung

    2011-01-01

    A distributed set of accelerometers based on the minimum number of 12 accelerometers allows for computation of the magnitude of angular rate without using the integration operation. However, it is not easy to extract the magnitude of angular rate in the presence of the accelerometer noises, and even worse, it is difficult to determine the direction of a rotation because the angular rate is present in its quadratic form within the inertial measurement system equations. In this paper, an extended Kalman filter scheme to correctly estimate both the direction and magnitude of the angular rate through fusion of the angular acceleration and quadratic form of the angular rate is proposed. We also provide observability analysis for the general distributed accelerometers-based inertial measurement unit, and show that the angular rate can be correctly estimated by general nonlinear state estimators such as an extended Kalman filter, except under certain extreme conditions. PMID:22346651

  5. Angular rate estimation using a distributed set of accelerometers.

    PubMed

    Park, Sungsu; Hong, Sung Kyung

    2011-01-01

    A distributed set of accelerometers based on the minimum number of 12 accelerometers allows for computation of the magnitude of angular rate without using the integration operation. However, it is not easy to extract the magnitude of angular rate in the presence of the accelerometer noises, and even worse, it is difficult to determine the direction of a rotation because the angular rate is present in its quadratic form within the inertial measurement system equations. In this paper, an extended Kalman filter scheme to correctly estimate both the direction and magnitude of the angular rate through fusion of the angular acceleration and quadratic form of the angular rate is proposed. We also provide observability analysis for the general distributed accelerometers-based inertial measurement unit, and show that the angular rate can be correctly estimated by general nonlinear state estimators such as an extended Kalman filter, except under certain extreme conditions. PMID:22346651

  6. Particle angular distributions and gamma-ray multiplicities as experimental probes for angular-momentum fluctuations

    SciTech Connect

    Moretto, L.G.

    1982-03-01

    The sequential emission of /sup 4/He is demonstrated in the reaction Ho + Ta and the /sup 4/He angular distribution is used to test the rigid rotation limit in the reaction Ho + Ag. A more refined analysis of the dependence of continuum ..gamma..-ray multiplicities upon Q-value and gamma ray energy shows that reasonable agreement with the statistical model is obtained if one assumes the presence of low energy aligned dipole transitions in the reactions Ho, Yb, Sm, Ag + Ho. Sequential fission angular distributions from very asymmetric reactions U, Au + Ne provide a severe test for the statistical model.

  7. Angular momentum transport in stellar interiors

    NASA Astrophysics Data System (ADS)

    Mathis, S.

    2011-12-01

    In this short article we review the advances that have been obtained in the global modelling of angular momentum transport in stellar interiors during the last years. First, we consider the couplings between differential rotation and the large-scale meridional circulation and shear-induced turbulence this induces. Then, we describe the state of the art of our understanding of transport mechanisms in presence of a fossil magnetic field. Next, we show how rotation and magnetic fields are now taken into account in the study of internal waves. Finally, we emphasize that it becomes necessary to get a complete picture of the interaction of stars with their environment.

  8. The Cosmology Large Angular Scale Surveyor (CLASS)

    NASA Astrophysics Data System (ADS)

    Eimer, Joseph; Ali, A.; Amiri, M.; Appel, J. W.; Araujo, D.; Bennett, C. L.; Boone, F.; Chan, M.; Cho, H.; Chuss, D. T.; Colazo, F.; Crowe, E.; Denis, K.; Dünner, R.; Essinger-Hileman, T.; Gothe, D.; Halpern, M.; Harrington, K.; Hilton, G.; Hinshaw, G. F.; Huang, C.; Irwin, K.; Jones, G.; Karakla, J.; Kogut, A. J.; Larson, D.; Limon, M.; Lowry, L.; Marriage, T.; Mehrle, N.; Miller, A. D.; Miller, N.; Moseley, S. H.; Novak, G.; Reintsema, C.; Rostem, K.; Stevenson, T.; Towner, D.; U-Yen, K.; Wagner, E.; Watts, D.; Wollack, E.; Xu, Z.; Zeng, L.

    2014-01-01

    The Cosmology Large Angular Scale Surveyor (CLASS) is an array of telescopes designed to search for the signature of inflation in the polarization of the Cosmic Microwave Background (CMB). By combining the strategy of targeting large scales (>2 deg) with novel front-end polarization modulation and novel detectors at multiple frequencies, CLASS will pioneer a new frontier in ground-based CMB polarization surveys. In this talk, I give an overview of the CLASS instrument, survey, and outlook on setting important new limits on the energy scale of inflation.

  9. Microcomputer-controlled perturbed angular correlation spectrometer

    SciTech Connect

    Jaeger, H.; Gardner, J.A.; Su, H.T.; Rasera, R.L.

    1987-09-01

    A four-detector time-differential perturbed angular correlation spectrometer controlled by an inexpensive microcomputer is described. The use of twin-single-channel analyzers permits each detector to identify both gamma rays in the cascade. An improved gating logic system reduces the MCA/computer deadtime and allows larger sample activity and faster data accumulation. The twin-single-channel analyzer and gating circuit additions also permit simultaneous accumulation of two statistically independent sets of four-channel spectra. The spectrometer provides on-line display of raw data and the perturbation function derived from either set of four-channel spectra.

  10. Angular momentum of multimode and polarization patterns.

    PubMed

    Zambrini, Roberta; Barnett, Stephen M

    2007-11-12

    We study the mechanical properties of a broad class of multimode and polarization light patterns, resulting from the interference and superposition of waves in helical modes. General local and global properties of energy and angular momentum (AM) are identified, in order to define the conditions to optimize the AM with increasing beam complexity. We show the possibility to engineer independently the local densities of optical AM and energy, opening the possibility of an experimental demonstration of their respective effects in light-matter interaction. Multimode Laguerre-Gaussian beams also allows us to tailor the local spin AM through the Gouy phase. PMID:19550805

  11. EQUAL CHANNEL ANGULAR EXTRUSION (ECAE) OF BERYLLIUM.

    SciTech Connect

    Field, R. D. (Richard D.); Hartwig, K. T.; Necker, C. T. (Carl T.); Bingert, J. F. (John F.); Agnew, S. R. (Sean R.)

    2001-01-01

    The Equal Channel Angular Extrusion (ECAE) technique has been applied to a P/M source Be alloy. Single and two-pass extrusions have been successfully completed, using two different processing routes, on Ni-canned billets of Be at 400 C. No cracking was observed in the billet and significant grain refinement was achieved. In this paper, microstructural features and dislocation structures are discussed for the single-pass material, including evidence of and dislocations. Significant crystallographic texture developed during ECAE, which will be discussed in terms of this unique deformation processing technique and the underlying physical processes which sustained the deformation.

  12. Angular momentum transport and flow super-rotation in Rayleigh stable Taylor-Couette

    NASA Astrophysics Data System (ADS)

    Nordsiek, Freja; Huisman, Sander; van der Veen, Roeland; Sun, Chao; Lohse, Detlef; Lathrop, Daniel

    2013-11-01

    We present experimental velocimetry and torque measurements for Taylor-Couette flow in the Rayleigh stable regime. Measurements are taken on two geometrically similar experiments, both of which had axial boundaries attatched to the outer cylinder, which is known to cause Ekman pumping. The Twente experiment has a radius ratio of 0.716, an aspect ratio of 11.68, and measures azimuthal velocities by Laser Doppler Anenometry. The Maryland experiment has a radius ratio of 0.725, an aspect ratio of 11.47, and measures the torque required to rotate the inner cylinder. The torque on the inner cylinder is observed to be greater than that of the analytical Couette profile and has a complex dependence on the Reynolds number and ?i /?o . The azimuthal velocity profiles also deviate from the laminar Couette profile. Signficantly, super-rotation in the angular velocity has been observed for 1 >?i /?o > 0 . In the quasi-Keplerian regime, the angular momentum profiles consist of an approximately constant inner region connected to an outer region approximately in solid-body rotation at ?o, which suggests that angular momentum is being actively transported from the inner region to the axial boundaries.

  13. CMB Anisotropies: Total Angular Momentum Method

    E-print Network

    Wayne Hu; Martin White

    1997-07-16

    A total angular momentum representation simplifies the radiation transport problem for temperature and polarization anisotropy in the CMB. Scattering terms couple only the quadrupole moments of the distributions and each moment corresponds directly to the observable angular pattern on the sky. We develop and employ these techniques to study the general properties of anisotropy generation from scalar, vector and tensor perturbations to the metric and the matter, both in the cosmological fluids and from any seed perturbations (e.g. defects) that may be present. The simpler, more transparent form and derivation of the Boltzmann equations brings out the geometric and model-independent aspects of temperature and polarization anisotropy formation. Large angle scalar polarization provides a robust means to distinguish between isocurvature and adiabatic models for structure formation in principle. Vector modes have the unique property that the CMB polarization is dominated by magnetic type parity at small angles (a factor of 6 in power compared with 0 for the scalars and 8/13 for the tensors) and hence potentially distinguishable independent of the model for the seed. The tensor modes produce a different sign from the scalars and vectors for the temperature-polarization correlations at large angles. We explore conditions under which one perturbation type may dominate over the others including a detailed treatment of the photon-baryon fluid before recombination.

  14. Evolution of the Angular Correlation Function

    E-print Network

    A. J. Connolly; A. S. Szalay; R. J. Brunner

    1998-03-05

    For faint photometric surveys our ability to quantify the clustering of galaxies has depended on interpreting the angular correlation function as a function of the limiting magnitude of the data. Due to the broad redshift distribution of galaxies at faint magnitude limits the correlation signal has been extremely difficult to detect and interpret. We introduce a new technique for measuring the evolution of clustering. We utilize photometric redshifts, derived from multicolor surveys, to isolate redshift intervals and calculate the evolution of the amplitude of the angular 2-pt correlation function. Applying these techniques to the the Hubble Deep Field we find that the shape of the correlation function, at z=1, is consistent with a power law with a slope of -0.8. For z>0.4 the best fit to the data is given by a model of clustering evolution with a comoving r0 = 2.37 Mpc and eps = -0.4 +/- 0.5, consistent with published measures of the clustering evolution. To match the canonical value of r0 = 5.4 Mpc, found for the clustering of local galaxies, requires a value of eps = 2.10 +/- 0.5 (significantly more than linear evolution). The log likelihood of this latter fit is 4.15 less than that for the r0 = 2.37 Mpc model. We, therefore, conclude that the parameterization of the clustering evolution of (1+z)^-(3+eps) is not a particularly good fit to the data.

  15. Angular power spectra with finite counts

    NASA Astrophysics Data System (ADS)

    Campbell, Sheldon S.

    2015-04-01

    Angular anisotropy techniques for cosmic diffuse radiation maps are powerful probes, even for quite small data sets. A popular observable is the angular power spectrum; we present a detailed study applicable to any unbinned source skymap S(n) from which N random, independent events are observed. Its exact variance, which is due to the finite statistics, depends only on S(n) and N; we also derive an unbiased estimator of the variance from the data. First-order effects agree with previous analytic estimates. Importantly, heretofore unidentified higher order effects are found to contribute to the variance and may cause the uncertainty to be significantly larger than previous analytic estimates - potentially orders of magnitude larger. Neglect of these higher order terms, when significant, may result in a spurious detection of the power spectrum. On the other hand, this would indicate the presence of higher order spatial correlations, such as a large bispectrum, providing new clues about the sources. Numerical simulations are shown to support these conclusions. Applying the formalism to an ensemble of Gaussian-distributed skymaps, the noise-dominated part of the power-spectrum uncertainty is significantly increased at high multipoles by the new, higher order effects. This work is important for harmonic analyses of the distributions of diffuse high-energy ?-rays, neutrinos, and charged cosmic rays, as well as for populations of sparse point sources such as active galactic nuclei.

  16. Angular Power Spectra with Finite Counts

    E-print Network

    Sheldon S. Campbell

    2014-10-24

    Angular anisotropy techniques for cosmic diffuse radiation maps are powerful probes, even for quite small data sets. A popular observable is the angular power spectrum; we present a detailed study applicable to any unbinned source skymap S(n) from which N random, independent events are observed. Its exact variance, which is due to the finite statistics, depends only on S(n) and N; we also derive an unbiased estimator of the variance from the data. First-order effects agree with previous analytic estimates. Importantly, heretofore unidentified higher-order effects are found to contribute to the variance and may cause the uncertainty to be significantly larger than previous analytic estimates---potentially orders of magnitude larger. Neglect of these higher-order terms, when significant, may result in a spurious detection of the power spectrum. On the other hand, this would indicate the presence of higher-order spatial correlations, such as a large bispectrum, providing new clues about the sources. Numerical simulations are shown to support these conclusions. Applying the formalism to an ensemble of Gaussian-distributed skymaps, the noise-dominated part of the power spectrum uncertainty is significantly increased at high multipoles by the new, higher-order effects. This work is important for harmonic analyses of the distributions of diffuse high-energy gamma-rays, neutrinos, and charged cosmic rays, as well as for populations of sparse point sources such as active galactic nuclei.

  17. Mass and angular-momentum inequalities for axi-symmetric initial data sets. II. Angular momentum

    SciTech Connect

    Chrusciel, Piotr T. [LMPT, Tours and Mathematical Institute, 24-29 St. Giles', Oxford OX1 3LB (United Kingdom)], E-mail: chrusciel@maths.ox.ac.uk; Li, Yanyan [Rutgers University (United States); Weinstein, Gilbert [University of Alabama at Birmingham (United States)

    2008-10-15

    We extend the validity of Dain's angular-momentum inequality to maximal, asymptotically flat, initial data sets on a simply connected manifold with several asymptotically flat ends which are invariant under a U(1) action and which admit a twist potential.

  18. Head kinematics in mini-sled tests of foam padding: relevance of linear responses from free motion headform (FMH) testing to head angular responses.

    PubMed

    Ivarsson, J; Viano, D C; Lövsund, P; Parnaik, Y

    2003-08-01

    The revised Federal Motor Vehicle Safety Standard (FMVSS) No. 201 specifies that the safety performance of vehicle upper interiors is determined from the resultant linear acceleration response of a free motion headform (FMH) impacting the interior at 6.7 m/s. This study addresses whether linear output data from the FMH test can be used to select an upper interior padding that decreases the likelihood of rotationally induced brain injuries. Using an experimental setup consisting of a Hybrid III head-neck structure mounted on a mini-sled platform, sagittal plane linear and angular head accelerations were measured in frontal head impacts into foam samples of various stiffness and density with a constant thickness (51 mm) at low (approximately 5.0 m/s), intermediate (approximately 7.0 m/s), and high (approximately 9.6 m/s) impact speeds. Provided that the foam samples did not bottom out, recorded peak values of angular acceleration and change in angular velocity increased approximately linearly with increasing peak resultant linear acceleration and value of the Head Injury Criterion (HIC36). The results indicate that the padding that produces the lowest possible peak angular acceleration and peak change in angular velocity without causing high peak forces is the one that produces the lowest possible HIC36 without bottoming out in the FMH test. PMID:12968577

  19. Photoelectron angular distributions from polar molecules probed by intense femtosecond lasers

    SciTech Connect

    Abu-samha, M.; Madsen, L. B. [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

    2010-10-15

    We present numerical calculations of molecular-frame photoelectron angular distributions in strong-field ionization of oriented polar HF and LiF molecules by linearly polarized laser pulses with durations of about 20 fs (seven cycles at 800 nm). The calculations are performed within the single-active-electron and frozen-nuclei approximations. Our analysis shows that for the HF and LiF molecules, anisotropies in the molecular potential and the probed orbital lead to enhanced ionization during laser half cycles with the field pointing antiparallel to the permanent dipole of the dipole term in a multipolar expansion of the anisotropic molecular potential. This is manifested as a strong asymmetry in the computed photoelectron angular distributions: The photoelectrons are preferentially detected opposite to the permanent dipole of the molecular potential. This phenomenon is very sensitive to the probed system (the probed orbital and the molecular potential) and the orientation angle between the molecular axis and the laser polarization.

  20. Genetic algorithms with decomposition procedures for multidimensional 0-1 knapsack problems with block angular structures.

    PubMed

    Kato, K; Sakawa, M

    2003-01-01

    This paper presents a detailed treatment of genetic algorithms with decomposition procedures as developed for large scale multidimensional 0-1 knapsack problems with block angular structures. Through the introduction of a triple string representation and the corresponding decoding algorithm, it is shown that a potential solution satisfying not only block constraints but also coupling constraints can be obtained for each individual. Then genetic algorithms with decomposition procedures are presented as an approximate solution method for multidimensional 0-1 knapsack problems with block angular structures. Many computational experiments on numerical examples with 30, 50, 70, 100, 150, 200, 300, 500, and 1000 variables demonstrate the feasibility and efficiency of the proposed method. PMID:18238188

  1. Comparison of FBP and Iterative Algorithms with Non-Uniform Angular Sampling

    PubMed Central

    Zeng, Gengsheng L.

    2014-01-01

    Some people may believe that the filtered backprojection (FBP) algorithm does not work if the projection data are measured non-uniformly. Some may also believe that iterative algorithms can automatically handle the non-uniformly sampled data in the projector/backprojector. This paper claims that the FBP algorithm can effectively handle the situation where the angular sampling is not uniform. This paper compares the images that are reconstructed by both the FBP and the iterative Landweber algorithms when the angular sampling is nonuniform. When the iteration number is low, the iterative algorithms do not handle the non-uniform sampling properly. A weighting strategy is then suggested and it makes the image resolution more isotropic. In few-view tomography, the FBP and iterative algorithms both perform poorly if no other prior information is used. We have made the following observations: 1) When using an iterative algorithm, one must use early solutions due to noise amplification. 2) An early solution can have anisotropic spatial resolution if the angular sampling is not uniform. 3) The anisotropic resolution problem can be solved by introducing angle dependent weighting, which is not noise dependent. 4) The weighting is not effective when the iteration number is large. The weighting only affects the early solutions, and does not affect the converged solution. 5) When the iteration number is large, the model-mismatch errors are amplified and cause artifacts in the image. 6) The FBP algorithm is not sensitive to the model-mismatch errors, and does not have the “early solution” problems. 7) In few-view tomography, both FBP and iterative algorithms perform poorly, while the FBP algorithm gives a sharper image than the iterative algorithm does. PMID:25678716

  2. Exploring Machin's Approximation of Exploring Machin's Approximation of

    E-print Network

    Knaust, Helmut

    #12;Exploring Machin's Approximation of Precursors Method of Exhaustion `a la Archimedes Archimedes of Precursors Method of Exhaustion `a la Archimedes Archimedes of Syracuse ( 287­212 BC) approximated la Archimedes Archimedes of Syracuse ( 287­212 BC) approximated by the Method of Exhaustion: 3

  3. Approximate nonlinear self-adjointness and approximate conservation laws

    E-print Network

    Zhi-Yong Zhang

    2013-04-03

    In this paper, approximate nonlinear self-adjointness for perturbed PDEs is introduced and its properties are studied. Consequently, approximate conservation laws which cannot be obtained by the approximate Noether theorem are constructed by means of the method. As an application, a class of perturbed nonlinear wave equations is considered to illustrate the effectiveness.

  4. Stability of Erythrocyte Ghosts: A ? -Ray Perturbed Angular Correlation Study

    NASA Astrophysics Data System (ADS)

    Kruse, Carol A.; Tin, George W.; Baldeschwieler, John D.

    1983-03-01

    The structural integrity of erythrocyte ghosts made by the preswell and slow-dialysis techniques has been studied in vitro by use of ? -ray perturbed angular correlation (PAC) techniques and also by standard in vitro leakage methods employing sequestered labeled markers. Complexes of 111In3+ and nitrilotriacetate were encapsulated in ghosts made from human, rabbit, rat, and mouse erythrocytes, and their leakage was monitored by both methods. In addition, 125I-labeled bovine serum albumin was encapsulated, and ghost integrity was monitored by conventional leakage measurements. With the PAC technique the percentage of material released from human ghosts was determined quantitatively, and the results were equivalent to those obtained by the conventional method. In addition, at various times after intravenous injection, tissue distribution of the ghosts in the mouse was studied. The percent injected dose per gram of tissue of the labeled surface proteins of erythrocyte ghosts in circulation approximated that of the entrapped labeled albumin. This suggests that the ghost membrane and contents are strongly associated in vivo. Large 125I-labeled bovine serum albumin molecules and small 111In3+-nitrilotriacetate complexes were delivered in high quantities to the lung initially, and to the liver and spleen. Because erythrocyte ghosts have the ability to entrap a wide range of substances and deliver them to specific organs, ghosts may be preferable to other drug carriers or drug therapy for treatment of certain disorders.

  5. The angular correlations of galaxies in the COSMOS field

    E-print Network

    H. J. McCracken; J. A. Peacock; L. Guzzo; P. Capak; C. Porciani; N. Scoville; H. Aussel; A. Finoguenov; J. B. James; M. G. Kitzbichler; A. Koekemoer; A. Leauthaud; O. Le Fèvre; R. Massey; Y. Mellier; B. Mobasher; P. Norberg; J. Rhodes; D. B. Sanders; S. S. Sasaki; Y. Taniguchi; D. J. Thompson; S. D. M. White; A. El-Zant

    2007-04-19

    We present measurements of the two-point galaxy angular correlation function w(\\theta) in the COSMOS field. Independent determinations of w(\\theta) as a function of magnitude limit are presented for both the HST ACS catalog and also for the ground-based data from Subaru and the CFHT. Despite having significantly different masks, these three determinations agree well. At bright magnitudes (IAB 10 arcmin, which we attribute to a particularly rich structure known to exist at z~0.8. For fainter samples, however, the level of clustering is somewhat higher than reported by some previous studies: in all three catalogues we find w(\\theta=1')~0.014 at a median IAB magnitude of 24. At these very faintest magnitudes, our measurements agree well with the latest determinations from the Canada-France Legacy Survey. This level of clustering is approximately double what is predicted by the semi-analytic catalogs (at all angles). The semi-analytic results allow an estimate of cosmic variance, which is too small to account for the discrepancy. We therefore conclude that the mean amplitude of clustering at this level is higher than previously estimated.

  6. Angular-resolved photoelectron spectroscopy of corrugated surfaces

    NASA Astrophysics Data System (ADS)

    Olejnik, K.; Zemek, J.; Werner, W. S. M.

    2005-12-01

    The influence of surface roughness on angle-resolved photoelectron intensities has been studied by means of a semiempirical method and experimentally. The full three-dimensional information about the surface roughness of real samples measured by atomic force microscopy (AFM) was used as an input for the calculations of the so-called tilt-angle histograms. Both effects of surface roughness, shadowing of photoelectrons and differences between microscopic and macroscopic signal electron emission geometry (true emission angles), are taken into account. Photoelectron current is then calculated using a common formalism XPS/AES valid for ideally flat surfaces, i.e. analytically by the straight-line approximation (SLA) or by Monte Carlo calculations. The approach which can be applied for an arbitrary type of surface roughness is verified on angular-resolved Si 2p photoelectron spectra recorded from model silicon samples with different artificially modified surface roughness, covered by a thin silicon oxide film and a surface contamination. The effect of surface roughness on the Si 2p photoelectron intensities was found to be quite prevalent over electron elastic scattering or surface contamination effects. The so-called magic angle depended on a character of surface roughness.

  7. Angular-momentum-dominated electron beams and flat-beam generation

    SciTech Connect

    Sun, Yin-e

    2005-06-01

    In the absence of external forces, if the dynamics within an electron beam is dominated by its angular momentum rather than other effects such as random thermal motion or self Coulomb-repulsive force (i.e., space-charge force), the beam is said to be angular-momentum-dominated. Such a beam can be directly applied to the field of electron-cooling of heavy ions; or it can be manipulated into an electron beam with large transverse emittance ratio, i.e., a flat beam. A flat beam is of interest for high-energy electron-positron colliders or accelerator-based light sources. An angular-momentum-dominated beam is generated at the Fermilab/NICADD photoinjector Laboratory (FNPL) and is accelerated to an energy of 16 MeV. The properties of such a beam is investigated systematically in experiment. The experimental results are in very good agreement with analytical expectations and simulation results. This lays a good foundation for the transformation of an angular-momentum-dominated beam into a flat beam. The round-to-flat beam transformer is composed of three skew quadrupoles. Based on a good knowledge of the angular-momentum-dominated beam, the quadrupoles are set to the proper strengths in order to apply a total torque which removes the angular momentum, resulting in a flat beam. For bunch charge around 0.5 nC, an emittance ratio of 100 {+-} 5 was measured, with the smaller normalized root-mean-square emittance around 0.4 mm-mrad. Effects limiting the flat-beam emittance ratio are investigated, such as the chromatic effects in the round-to-flat beam transformer, asymmetry in the initial angular-momentum-dominated beam, and space-charge effects. The most important limiting factor turns out to be the uncorrelated emittance growth caused by space charge when the beam energy is low, for example, in the rf gun area. As a result of such emittance growth prior to the round-to-flat beam transformer, the emittance ratio achievable in simulation decreases from orders of thousands to hundreds. Finally, factors that might spoil the smaller transverse emittance such as beamline misalignments and dispersions caused by magnetic elements are discussed. The limit of the emittance measurement system, such as camera resolution, is also studied.

  8. First Year Wilkinson Microwave Anisotropy Probe(WMAP)Observations: The Angular Power Spectrum

    NASA Technical Reports Server (NTRS)

    Hinshaw, G.; Spergel, D. N.; Verde, L.; Hill, R. S.; Meyer, S. S.; Barnes, C.; Bennett, C. L.; Halpern, M.; Jarosik, N.; Kogut, A.

    2003-01-01

    We present the angular power spectrum derived from the first-year Wilkinson Microwave Anisotropy Probe (WMAP) sky maps. We study a variety of power spectrum estimation methods and data combinations and demonstrate that the results are robust. The data are modestly contaminated by diffuse Galactic foreground emission, but we show that a simple Galactic template model is sufficient to remove the signal. Point sources produce a modest contamination in the low frequency data. After masking approximately 700 known bright sources from the maps, we estimate residual sources contribute approximately 3500 mu sq Kappa at 41 GHz, and approximately 130 mu sq Kappa at 94 GHz, to the power spectrum [iota(iota + 1)C(sub iota)/2pi] at iota = 1000. Systematic errors are negligible compared to the (modest) level of foreground emission. Our best estimate of the power spectrum is derived from 28 cross-power spectra of statistically independent channels. The final spectrum is essentially independent of the noise properties of an individual radiometer. The resulting spectrum provides a definitive measurement of the CMB power spectrum, with uncertainties limited by cosmic variance, up to iota approximately 350. The spectrum clearly exhibits a first acoustic peak at iota = 220 and a second acoustic peak at iota approximately 540, and it provides strong support for adiabatic initial conditions. Researchers have analyzed the CT(sup Epsilon) power spectrum, and present evidence for a relatively high optical depth, and an early period of cosmic reionization. Among other things, this implies that the temperature power spectrum has been suppressed by approximately 30% on degree angular scales, due to secondary scattering.

  9. A Nonparametric Riemannian Framework for Processing High Angular Resolution Diffusion Images (HARDI)

    E-print Network

    distribution func- tion. Water diffusion is then represented mathematically with a symmetric positive semi the orientation distribution function (ODF), which is the probability distribution function of wa- ter molecule parameterization, such as a mixture of von Mises-Fisher distributions or a spherical harmonic expansion. Instead

  10. High angular resolution mm- and submm-observations of dense molecular gas in M82

    NASA Technical Reports Server (NTRS)

    Wild, W.; Eckart, Andreas; Genzel, Reinhard; Harris, Andrew I.; Jackson, James M.; Jaffe, D. T.; Lugten, J. B.; Stutzki, J.

    1990-01-01

    Researchers observed CO(7-6), CO(3-2), HCN(3-2) and HCO+(3-2) line emission toward the starburst nucleus of M82 and have obtained an upper limit to H13CN(3-2). These are the first observations of the CO(7-6), HCN(3-2) and HCO+(3-2) lines in any extragalactic source. Researchers took the CO(7-6) spectrum in January 1988 at the Infrared Telescope Facility (IRTF) with the Max Planck Institute for Extraterrestrial Physics/Univ. of California, Berkeley 800 GHz Heterodyne Receiver. In March 1989 researchers used the Institute for Radio Astronomy in the Millimeter range (IRAM) 30 m telescope to observe the CO(3-2) line with the new MPE 350 GHz Superconductor Insulator Superconductor (SIS) receiver and the HCN(3-2) and HCO+(3-2) lines with the (IRAM) 230 GHz SIS receiver (beam 12" FWHM, Blundell et al. 1988). The observational parameters are summarized.

  11. Brain fiber architecture, genetics, and intelligence: a high angular resolution diffusion imaging (HARDI) study.

    PubMed

    Chiang, Ming-Chang; Barysheva, Marina; Lee, Agatha D; Madsen, Sarah; Klunder, Andrea D; Toga, Arthur W; Mcmahon, Katie L; de Zubicaray, Greig I; Meredith, Matthew; Wright, Margaret J; Srivastava, Anuj; Balov, Nikolay; Thompson, Paul M

    2008-01-01

    We developed an analysis pipeline enabling population studies of HARDI data, and applied it to map genetic influences on fiber architecture in 90 twin subjects. We applied tensor-driven 3D fluid registration to HARDI, resampling the spherical fiber orientation distribution functions (ODFs) in appropriate Riemannian manifolds, after ODF regularization and sharpening. Fitting structural equation models (SEM) from quantitative genetics, we evaluated genetic influences on the Jensen-Shannon divergence (JSD), a novel measure of fiber spatial coherence, and on the generalized fiber anisotropy (GFA) a measure of fiber integrity. With random-effects regression, we mapped regions where diffusion profiles were highly correlated with subjects' intelligence quotient (IQ). Fiber complexity was predominantly under genetic control, and higher in more highly anisotropic regions; the proportion of genetic versus environmental control varied spatially. Our methods show promise for discovering genes affecting fiber connectivity in the brain. PMID:18979850

  12. A high angular-resolution search for the progenitor of the type Ic Supernova 2004gt

    E-print Network

    A. Gal-Yam; D. B. Fox; S. R. Kulkarni; K. Matthews; D. C. Leonard; D. J. Sand; D. -S. Moon; S. B. Cenko; A. M. Soderberg

    2005-08-03

    We report the results of a high-spatial-resoltion search for the progenitor of type Ic supernova SN 2004gt, using the newly commissioned Keck laser-guide star adaptive optics system (LGSAO) along with archival Hubble Space Telescope data. This is the deepest search yet performed for the progenitor of any type Ib/c event in a wide wavelength range stretching from the far UV to the near IR. We determine that the progenitor of SN 2004gt was most likely less luminous than M_V=-5.5 and M_B=-6.5 magnitudes. The massive stars exploding as hydrogen-deficient core-collapse supernovae (SNe) should have lost their outer hydrogen envelopes prior to their explosion, either through winds -- such stars are identified within our Galaxy as Wolf-Rayet (W-R) stars -- or to a binary companion. The luminosity limits we set rule out more than half of the known galactic W-R stars as possible progenitors of this event. In particular, they imply that a W-R progenitor should have been among the more-evolved (highly stripped, less luminous) of these stars, a concrete constraint on its evolutionary state just prior to core collapse. The possibility of a less luminous, lower-mass binary progenitor cannot be constrained. This study demonstrates the power of LGS observations in furthering our understanding of core collapse, and the physics powering supernovae, GRBs and XRFs.

  13. High angular resolution and young stellar objects: Imaging the surroundings of MWC 158 by optical interferometry

    NASA Astrophysics Data System (ADS)

    Kluska, J.; Malbet, F.; Berger, J.-P.; Benisty, M.; Lazareff, B.; Le Bouquin, J.-B.; Pinte, C.

    2012-12-01

    In the course of our VLTI young stellar object PIONIER imaging program, we have identified a strong visibility chromatic dependency that appeared in certain sources. This effect, rising value of visibilities with decreasing wavelengths over one base, is also present in previous published and archival AMBER data. For Herbig AeBe stars, the H band is generally located at the transition between the star and the disk predominance in flux for Herbig AeBe stars. We believe that this phenomenon is responsible for the visibility rise effect. We present a method to correct the visibilities from this effect in order to allow "gray" image reconstruction software, like Mira, to be used. In parallel we probe the interest of carrying an image reconstruction in each spectral channel and then combine them to obtain the final broadband one. As an illustration we apply these imaging methods to MWC158, a (possibly Herbig) B[e] star intensively observed with PIONIER. Finally, we compare our result with a parametric model fitted onto the data.

  14. High Angular Resolution and Young Stellar Objects: Imaging the Surroundings of MWC 158 by Optical Interferometry

    NASA Astrophysics Data System (ADS)

    Kluska, J.; Malbet, F.; Berger, J.-P.; Benisty, M.; Lazareff, B.; Le Bouquin, J.-B.; Pinte, C.

    2013-03-01

    In the course of our VLTI young stellar object PIONIER imaging program, we have identified a strong visibility chromatic dependency that appeared in certain sources. This effect, rising value of visibilities with decreasing wavelengths over one base, is also present in previous published and archival AMBER data. For Herbig AeBe stars, the H band is generally located at the transition between the star and the disk predominance in flux for Herbig AeBe stars. We believe that this phenomenon is responsible for the visibility rise effect. We present a method to correct the visibilities from this effect in order to allow "gray" image reconstruction software, like Mira, to be used. In parallel we probe the interest of carrying an image reconstruction in each spectral channel and then combine them to obtain the final broadband one. As an illustration we apply these imaging methods to MWC158, a (possibly Herbig) B[e] star intensively observed with PIONIER. Finally, we compare our result with a parametric model fitted onto the data.

  15. VizieR Online Data Catalog: AT20G high-angular-resolution catalogue (Chhetri+, 2013)

    NASA Astrophysics Data System (ADS)

    Chhetri, R.; Ekers, R. D.; Jones, P. A.; Ricci, R.

    2014-08-01

    For data processing we used the Multichannel Image Reconstruction, Image Analysis and Display (MIRIAD; Sault, Teuben & Wright, 1995, ASP Conf. Ser., Vol. 77, p. 433) software package. We used the AT20G survey data after the initial data quality checks implemented in an automated custom analysis pipeline as described by Murphy et al. (2010MNRAS.402.2403M). We then calculated the visibilities on the 4500m baselines in a separate custom pipeline. (2 data files).

  16. CMB lensing power spectrum biases from galaxies and clusters using high-angular resolution temperature maps

    SciTech Connect

    Van Engelen, A.; Sehgal, N. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States); Bhattacharya, S. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Holder, G. P. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); Zahn, O. [Berkeley Center for Cosmological Physics, Department of Physics, University of California, and Lawrence Berkeley National Labs, Berkeley, CA 94720 (United States); Nagai, D. [Department of Physics, Department of Astronomy and Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06520 (United States)

    2014-05-01

    The lensing power spectrum from cosmic microwave background (CMB) temperature maps will be measured with unprecedented precision with upcoming experiments, including upgrades to the Atacama Cosmology Telescope and the South Pole Telescope. Achieving significant improvements in cosmological parameter constraints, such as percent level errors on ?{sub 8} and an uncertainty on the total neutrino mass of ?50 meV, requires percent level measurements of the CMB lensing power. This necessitates tight control of systematic biases. We study several types of biases to the temperature-based lensing reconstruction signal from foreground sources such as radio and infrared galaxies and the thermal Sunyaev-Zel'dovich effect from galaxy clusters. These foregrounds bias the CMB lensing signal due to their non-Gaussian nature. Using simulations as well as some analytical models we find that these sources can substantially impact the measured signal if left untreated. However, these biases can be brought to the percent level if one masks galaxies with fluxes at 150 GHz above 1 mJy and galaxy clusters with masses above M {sub vir} = 10{sup 14} M {sub ?}. To achieve such percent level bias, we find that only modes up to a maximum multipole of l {sub max} ? 2500 should be included in the lensing reconstruction. We also discuss ways to minimize additional bias induced by such aggressive foreground masking by, for example, exploring a two-step masking and in-painting algorithm.

  17. Instrument for underwater high-angular resolution volume scattering function measurements

    Microsoft Academic Search

    Paul W. Dueweke; Jay Bolstad; Donald A. Leonard; Harold E. Sweeney; Philip A. Boyer; Erik M. Winkler

    1997-01-01

    A prototype instrument for in situ measurements of the volume scattering function (VSF) and the beam attenuation of water has been built and tested in the EOO laboratory. The intended application of the instrument is the enhancement of Navy operational optical systems for finding and imaging underwater objects such as mines. A description of the apparatus that was built and

  18. A High Angular Resolution View of Hot Gas in Clusters, Groups, and Galaxies

    E-print Network

    W. Forman; E. Churazov; L. David; F. Durret; C. Jones; M. Markevitch; S. Murray; M. Sun; A. Vikhlinin

    2003-01-23

    We discuss two themes from Chandra and XMM-Newton observations of galaxies, groups, and clusters. First, we review observational aspects of cluster formation and evolution as matter accretes along filaments in A85 and A1367. We describe Chandra observations that probe the later evolutionary phases where the effects of mergers -- both subsonic and supersonic -- are observed in cluster cores as ``cold fronts'' and shocks. Second, we review the interactions between the hot, intracluster gas with relativistic plasma originating in active nuclei within the dominant galaxy at the cluster center. As examples of this interaction, we describe the radio and X-ray observations of M87 where buoyantly rising bubbles transfer energy and matter within the cluster core. We describe the Chandra observations of ZW3146 which exhibits both multiple cold fronts and relativistic plasma interactions. Finally, we describe the X-ray observations of NGC4636 where energy produced by the central AGN imprints a unique signature on the surrounding hot corona of the galaxy.

  19. Dynamical effects of the neutrino gravitational clustering at Planck angular scales

    E-print Network

    L. A. Popa; C. Burigana; N. Mandolesi

    2002-03-19

    We study the CMB anisotropy induced by the non-linear perturbations in the massive neutrino density associated to the non-linear gravitational clustering proceses. Our results show that for the neutrino fraction in agreement with that indicated by the astroparticle and nuclear physics experiments and a cosmological accreting mass comparable with the mass of known clusters, the angular resolution and the sensitivity of the CMB anisotropy measurements from the Planck surveyor will allow the detection of the dynamical effects of the neutrino gravitational clustering.

  20. Two-photon polymerization of a three dimensional structure using beams with orbital angular momentum

    SciTech Connect

    Zhang, Shi-Jie; Li, Yan, E-mail: li@pku.edu.cn; Liu, Zhao-Pei; Ren, Jin-Li; Xiao, Yun-Feng; Yang, Hong; Gong, Qihuang [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871, People's Republic of China and Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China)

    2014-08-11

    The focus of a beam with orbital angular momentum exhibits internal structure instead of an elliptical intensity distribution of a Gaussian beam, and the superposition of Gauss-Laguerre beams realized by two-dimensional phase modulation can generate a complex three-dimensional (3D) focus. By taking advantage of the flexibility of this 3D focus tailoring, we have fabricated a 3D microstructure with high resolution by two-photon polymerization with a single exposure. Furthermore, we have polymerized an array of double-helix structures that demonstrates optical chirality.

  1. Angular asymmetries as a probe for anomalous contributions to H Z Z vertex at the LHC

    NASA Astrophysics Data System (ADS)

    Belyaev, N.; Konoplich, R.; Pedersen, L. Egholm; Prokofiev, K.

    2015-06-01

    In this article, the prospects for studying the tensor structure of the H Z Z vertex with the LHC experiments are presented. The structure of tensor couplings in Higgs di-boson decays is investigated by measuring the asymmetries and by studying the shapes of the final state angular distributions. The expected background contributions, detector resolution, and trigger and selection efficiencies are taken into account. The potential of the LHC experiments to discover sizeable non-Standard Model contributions to the H Z Z vertex with 300 and 3000 fb-1 is demonstrated.

  2. On uniform approximation of elliptic functions by Pade approximants

    SciTech Connect

    Khristoforov, Denis V [Steklov Mathematical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2009-06-30

    Diagonal Pade approximants of elliptic functions are studied. It is known that the absence of uniform convergence of such approximants is related to them having spurious poles that do not correspond to any singularities of the function being approximated. A sequence of piecewise rational functions is proposed, which is constructed from two neighbouring Pade approximants and approximates an elliptic function locally uniformly in the Stahl domain. The proof of the convergence of this sequence is based on deriving strong asymptotic formulae for the remainder function and Pade polynomials and on the analysis of the behaviour of a spurious pole. Bibliography: 23 titles.

  3. THE ANGULAR MOMENTUM OF MAGNETIZED MOLECULAR CLOUD CORES: A TWO-DIMENSIONAL-THREE-DIMENSIONAL COMPARISON

    SciTech Connect

    Dib, Sami; Csengeri, Timea; Audit, Edouard [Service d'Astrophysique, DSM/Irfu, CEA/Saclay, F-91191, Gif-sur-Yvette Cedex (France); Hennebelle, Patrick [Laboratoire de Radioastronomie, UMR CNRS 8112, Ecole Normale Superieure, Observatoire de Paris, 24 rue Lhomond, 75231 Paris Cedex 05 (France); Pineda, Jaime E.; Goodman, Alyssa A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bontemps, Sylvain, E-mail: sami.dib@cea.f [CNRS/INU, Laboratoire d'Astrophysique de Bordeaux, UMR 5804, BP 89, 33271, Floirac, Cedex (France)

    2010-11-01

    In this work, we present a detailed study of the rotational properties of magnetized and self-gravitating dense molecular cloud (MC) cores formed in a set of two very high resolution three-dimensional (3D) MC simulations with decaying turbulence. The simulations have been performed using the adaptative mesh refinement code RAMSES with an effective resolution of 4096{sup 3} grid cells. One simulation represents a mildly magnetically supercritical cloud and the other a strongly magnetically supercritical cloud. We identify dense cores at a number of selected epochs in the simulations at two density thresholds which roughly mimic the excitation densities of the NH{sub 3} (J - K) = (1,1) transition and the N{sub 2}H{sup +} (1-0) emission line. A noticeable global difference between the two simulations is the core formation efficiency (CFE) of the high-density cores. In the strongly supercritical simulations, the CFE is 33% per unit free-fall time of the cloud (t{sub ff,cl}), whereas in the mildly supercritical simulations this value goes down to {approx}6 per unit t{sub ff,cl}. A comparison of the intrinsic specific angular momentum (j{sub 3D}) distributions of the cores with the specific angular momentum derived using synthetic two-dimensional (2D) velocity maps of the cores (j{sub 2D}) shows that the synthetic observations tend to overestimate the true value of the specific angular momentum by a factor of {approx}8-10. We find that the distribution of the ratio j{sub 3D}/j{sub 2D} of the cores peaks at around {approx}0.1. The origin of this discrepancy lies in the fact that contrary to the intrinsic determination of j which sums up the individual gas parcels' contributions to the angular momentum, the determination of the specific angular momentum using the standard observational procedure which is based on a measurement on the global velocity gradient under the hypothesis of uniform rotation smoothes out the complex fluctuations present in the 3D velocity field. Our results may well provide a natural explanation for the discrepancy by a factor of {approx}10 observed between the intrinsic 3D distributions of the specific angular momentum and the corresponding distributions derived in real observations. We suggest that previous and future measurements of the specific angular momentum of dense cores which are based on the measurement of the observed global velocity gradients may need to be reduced by a factor of {approx}10 in order to derive a more accurate estimate of the true specific angular momentum in the cores. We also show that the exponent of the size-specific angular momentum relation is smaller ({approx}1.4) in the synthetic observations than their values derived in the 3D space ({approx}1.8).

  4. Axial resolution in elastography

    Microsoft Academic Search

    Raffaella Righetti; Jonathan Ophir; Periklis Ktonas

    2002-01-01

    The limits and trade-offs of the axial resolution in elastography were investigated using a controlled simulation study. The axial resolution in elastography was estimated as the distance between the full widths at half-maximum of the strain profiles of two equally stiff lesions embedded in a softer homogeneous background. The results show that the upper bound of the axial resolution in

  5. The explicit representation for the angular flux solution in the simplified P{sub N} (SP{sub N}) theory

    SciTech Connect

    Chao, Y. A. [Apartment 101, Building 2, 788 Hong Xu Road, Shanghai 201103 (China); Yamamoto, A. [Nagoya Univ., Furo-cho, Chikusa-ku, Nagoya, 464-8603 (Japan)

    2012-07-01

    The current SP{sub n} theory formulation, via either the asymptotic method or the variational method, does not provide an explicit and calculable representation for the corresponding angular flux solution. It is therefore not possible to reconstruct from the SP{sub n} solution the corresponding angular flux solution, or to extract from a reference transport solution the corresponding SP{sub n} solution. This makes it impossible to calculate the necessary surface discontinuity factors to force consistency between the SP{sub n} solution and the higher level transport solution. Without discontinuity factors, the superiority of SP{sub n} over diffusion could be significantly degraded in practical applications. In this paper we present a different SP{sub n} formulation that provides the explicit angular flux solution such that the physical picture for the SP{sub n} approximation is transparent and the SP{sub n} discontinuity factors can be calculated. (authors)

  6. DIRECT MEASUREMENT OF THE ANGULAR POWER SPECTRUM OF COSMIC MICROWAVE BACKGROUND TEMPERATURE ANISOTROPIES IN THE WMAP DATA

    SciTech Connect

    Chiang, Lung-Yih [Institute of Astrophysics, National Taiwan University, 1, Rooservolt Road, Taipei, Taiwan (China); Chen, Fei-Fan, E-mail: lychiang@asiaa.sinica.edu.tw [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)

    2012-05-20

    The angular power spectrum of the cosmic microwave background temperature anisotropies is one of the most important characteristics in cosmology that can shed light on the properties of the universe such as its geometry and total density. Using flat sky approximation and Fourier analysis, we estimate the angular power spectrum from an ensemble of the least foreground-contaminated square patches from the Wilkinson Microwave Anisotropy Probe W and V frequency band map. This method circumvents the issue of foreground cleaning and that of breaking orthogonality in spherical harmonic analysis because we are able to mask out the bright Galactic plane region, thereby rendering a direct measurement of the angular power spectrum. We test and confirm the Gaussian statistical characteristic of the selected patches, from which the first and second acoustic peaks of the power spectrum are reproduced, and the third peak is clearly visible, albeit with some noise residual at the tail.

  7. Correction of measured Gamma-Knife output factors for angular dependence of diode detectors and PinPoint ionization chamber.

    PubMed

    Hršak, Hrvoje; Majer, Marija; Grego, Timor; Bibi?, Juraj; Heinrich, Zdravko

    2014-12-01

    Dosimetry for Gamma-Knife requires detectors with high spatial resolution and minimal angular dependence of response. Angular dependence and end effect time for p-type silicon detectors (PTW Diode P and Diode E) and PTW PinPoint ionization chamber were measured with Gamma-Knife beams. Weighted angular dependence correction factors were calculated for each detector. The Gamma-Knife output factors were corrected for angular dependence and end effect time. For Gamma-Knife beams angle range of 84°-54°. Diode P shows considerable angular dependence of 9% and 8% for the 18 mm and 14, 8, 4 mm collimator, respectively. For Diode E this dependence is about 4% for all collimators. PinPoint ionization chamber shows angular dependence of less than 3% for 18, 14 and 8 mm helmet and 10% for 4 mm collimator due to volumetric averaging effect in a small photon beam. Corrected output factors for 14 mm helmet are in very good agreement (within ±0.3%) with published data and values recommended by vendor (Elekta AB, Stockholm, Sweden). For the 8 mm collimator diodes are still in good agreement with recommended values (within ±0.6%), while PinPoint gives 3% less value. For the 4 mm helmet Diodes P and E show over-response of 2.8% and 1.8%, respectively. For PinPoint chamber output factor of 4 mm collimator is 25% lower than Elekta value which is generally not consequence of angular dependence, but of volumetric averaging effect and lack of lateral electronic equilibrium. Diodes P and E represent good choice for Gamma-Knife dosimetry. PMID:25266988

  8. Computer Graphics Proceedings, Annual Conference Series, 2005 Fast and Detailed Approximate Global Illumination by

    E-print Network

    O'Brien, James F.

    by decomposing the radiance field close to surfaces into separate far- and near-field components that can-data interpolation with spheri- cal harmonics to represent spatial and angular variation, and our near-field scheme a ground-truth solution. We also discuss how our near-field approximation can be used with standard local

  9. Structural optimization with approximate sensitivities

    Microsoft Academic Search

    S. N Patnaik; D. A Hopkins; R Coroneos

    1996-01-01

    Computational efficiency in structural optimization can be enhanced if the intensive computations associated with the calculation of the sensitivities, that is, gradients of the behavior constraints, are reduced. Approximation to gradients of the behavior constraints that can be generated with a small amount of numerical calculations is proposed. Structural optimization with these approximate sensitivities produced correct optimum solution. Approximate gradients

  10. Taylor Approximations and Definite Integrals

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2007-01-01

    We investigate the possibility of approximating the value of a definite integral by approximating the integrand rather than using numerical methods to approximate the value of the definite integral. Particular cases considered include examples where the integral is improper, such as an elliptic integral. (Contains 4 tables and 2 figures.)

  11. High-resolution model of Asteroid 4179 Toutatis

    Microsoft Academic Search

    R. S. Hudson; S. J. Ostro; D. J. Scheeresc

    2003-01-01

    A model of the shape of Toutatis based on “high-resolution” radar images obtained in 1992 and 1996 consists of 39,996 triangular facets of roughly equal area, defined by the locations of 20,000 vertices. These define the average spatial resolution of the model as approximately 34 m, significantly finer than Hudson and Ostro’s (1995, Science 270, 84–86) model (1600 vertices, resolution

  12. Angular momentum effects in subbarrier fusion

    SciTech Connect

    Halbert, M.L.; Beene, J.R.; Hensley, D.C.; Honkanen, K.; Semkow, T.M.; Abenante, V.; Sarantites, D.G.; Li, Z.

    1988-01-01

    Angular-momentum distributions sigma/sub L/ for the compound nucleus /sup 164/Yb were deduced from measurements of ..gamma..-ray multiplicity for all significant evaporation residues from fusion of /sup 64/Ni and /sup 100/Mo at and below the Coulomb barrier. The excitation functions can be reproduced with coupled-channels calculations only if additional coupling beyond the known inelastic strengths is included. Even with this augmented coupling, however, at the lowest bombarding energies the experimental sigma/sub L/ extend to higher L values than the predictions. Single-barrier penetration models for a potential with an energy-dependent depth and shape fitted to the excitation function likewise underestimate the role of high-L partial waves. Somewhat better success is achieved with models in which fission is allowed to occur at distances comparable with or even larger than the Coulomb barrier radius. 24 refs., 3 figs., 2 tabs.

  13. Coherent Control of Photoelectron Wavepacket Angular Interferograms

    E-print Network

    Hockett, Paul; Baumert, Thomas

    2015-01-01

    Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the coherent control over the resultant photoelectron interferogram is thus explored in detail. Based on this understanding, the use of coherent control with polarization-shaped pulses as a methodology for a highly multiplexed coherent quantum metrology is also investigated, and defined in terms of the information content of the observable.

  14. Angular relation of axes in perceptual space

    NASA Technical Reports Server (NTRS)

    Bucher, Urs

    1992-01-01

    The geometry of perceptual space needs to be known to model spatial orientation constancy or to create virtual environments. To examine one main aspect of this geometry, the angular relation between the three spatial axes was measured. Experiments were performed consisting of a perceptual task in which subjects were asked to set independently their apparent vertical and horizontal plane. The visual background provided no other stimuli to serve as optical direction cues. The task was performed in a number of different body tilt positions with pitches and rolls varied in steps of 30 degs. The results clearly show the distortion of orthogonality of the perceptual space for nonupright body positions. Large interindividual differences were found. Deviations from orthogonality up to 25 deg were detected in the pitch as well as in the roll direction. Implications of this nonorthogonality on further studies of spatial perception and on the construction of virtual environments for human interaction is also discussed.

  15. Angular correlation measurements in 40Ar

    Microsoft Academic Search

    J. R. Southon; A. R. Poletti; D. J. Beale

    1976-01-01

    Proton-gamma angular correlation measurements have been carried out on states in 40Ar populated by the 40Ar(p,p') reaction. Mixing ratios measured include the following (spin sequences are given in parentheses): sigma(2.52-->1.46)=0.41-0.06+0.13(2-->2) sigma(3.21-->1.46)=-0.11+\\/-0.07 (2-->2)sigma(3.51-->1.46)=0.05+\\/-0.11(2-->2)sigma(3.68-->1.46)=0.07-0.05+0.11(3-->2)sigma(3.92-->1.46) 0.3(2-->2). Rigorous spin assignments of 2 and 1 have beenmade to the 3.21 and 4.48 MeV levels, respectively. Excitation energies have been derived for some of the states

  16. Orbital angular momentum photonic quantum interface

    E-print Network

    Yan Li; Zhi-Yuan Zhou; Dong-Sheng Ding; Wei Zhang; Shuai Shi; Bao-Sen Shi; Guang-Can Guo

    2014-10-28

    High dimensional orbital angular momentum (OAM) light states are very important in enhancing the information carrying capacity in optical communications and quantum key distributions. Light at wavelengths of fiber communication windows or free space communication windows are suitable for long distance quantum communication, but most quantum processing tasks are performed in the visible wavelength ranges. The interface to bridge the wavelength gap of single photon with Gaussian shape has been realized, however, to create such interface for OAM-carrying light is a great challenge. We report the demonstration of such an interface to frequency up-conversion of herald single photon OAM state from 1560nm to 525nm with high efficiency by using nonlinear crystal in an external cavity. We show that different single photon OAM light shapes are observed directly by using single photon counting camera and the single photon entangled property is retained in the conversion process.

  17. Colliding particles carrying nonzero orbital angular momentum

    SciTech Connect

    Ivanov, Igor P. [IFPA, Universite de Liege, Allee du 6 Aout 17, batiment B5a, 4000 Liege, Belgium and Sobolev Institute of Mathematics, Koptyug avenue 4, 630090, Novosibirsk (Russian Federation)

    2011-05-01

    Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some generic features of scattering processes involving twisted particles in the initial and/or final state. In order to avoid additional complications arising from nontrivial polarization states, we focus here on scalar fields only. We show that processes involving twisted particles allow one to perform a Fourier analysis of the plane-wave cross section with respect to the azimuthal angles of the initial particles. In addition, using twisted states, one can probe the autocorrelation function of the amplitude, which is inaccessible in the plane-wave collisions. Finally, we discuss prospects for experimental study of these effects.

  18. EBSD FEG-SEM, TEM and XRD techniques applied to grain study of a commercially pure 1200 aluminum subjected to equal-channel angular-pressing.

    PubMed

    Cabibbo, M; Evangelista, E; Scalabroni, C

    2005-01-01

    Microstructural evolution due to equal-channel angular-pressing (ECAP) with increasingly severe deformation was investigated in a commercially pure 1200 aluminum alloy. A true strain of eight produced sub-micrometer scale grains and very fine subgrains in the grain interior. The deformation process was documented and described using field-emission (FEG) gun scanning and transmission electron microscopy techniques. After eight ECAP passes, the high-angle grain boundaries accounted for approximately 70% of all boundaries. The fine spacing resolution of FEG scanning electron microscopy allowed detailed grain and subgrain statistical evaluation in the deformed microstructure; transmission electron microscopic inspection afforded appreciation of the role of very low-angle misorientation boundaries in the microstructure-refining process. ECAP results were compared with those produced by cold rolling. The material's texture evolved in a decreasing trend of Cube {001}100 intensities in favor of Cube rotated toward the normal-to-pressing direction {001}120, while Goss {110}001 and {111}110, {111}112 directions slightly increased with strain. PMID:15908224

  19. Recovery Guarantees for Restoration and Separation of Approximately Sparse Signals

    E-print Network

    noise have been studied in [2], [11]. The corresponding algorithms and proof techniques, how- resolution, and signal separation. We develop computationally efficient algorithms for signal restoration columns have unit Euclidean norm. The vector x is assumed to be approximately sparse, i.e., its main

  20. Angular distribution of low-energy cosmic ray muons underground

    Microsoft Academic Search

    P. N. Bhat; P. V. Ramana Murthy

    1978-01-01

    An experiment to study the angular distribution of stopping muons at a depth of 417 hg cm-2 (1 hg cm-2=100 g cm-2) at Kolar Gold Fields, India, has been completed. The best-fit value of the exponent, n, of the angular distribution is 2.23+or-0.33. From the observations it is concluded that the locally produced low-energy muons follow an angular distribution of

  1. Measurement of angular correlations based on secondary vertex reconstruction at

    Microsoft Academic Search

    V. Khachatryan; A. M. Sirunyan; A. Tumasyan; W. Adam; T. Bergauer; M. Dragicevic; J. Erö; C. Fabjan; M. Friedl; R. Frühwirth; V. M. Ghete; J. Hammer; S. Hänsel; C. Hartl; M. Hoch; N. Hörmann; J. Hrubec; M. Jeitler; G. Kasieczka; W. Kiesenhofer; M. Krammer; D. Liko; I. Mikulec; M. Pernicka; H. Rohringer; R. Schöfbeck; J. Strauss; A. Taurok; F. Teischinger; P. Wagner; W. Waltenberger; G. Walzel; E. Widl; C.-E. Wulz; V. Mossolov; N. Shumeiko; J. Suarez Gonzalez; L. Benucci; K. Cerny; E. A. De Wolf; X. Janssen; T. Maes; L. Mucibello; S. Ochesanu; B. Roland; R. Rougny; M. Selvaggi; H. Van Haevermaet; P. Van Mechelen; N. Van Remortel; S. Beauceron; F. Blekman; S. Blyweert; J. D’Hondt; O. Devroede; R. Gonzalez Suarez; A. Kalogeropoulos; J. Maes; M. Maes; S. Tavernier; W. Van Doninck; P. Van Mulders; G. P. Van Onsem; I. Villella; O. Charaf; B. Clerbaux; G. De Lentdecker; V. Dero; A. P. R. Gay; G. H. Hammad; T. Hreus; P. E. Marage; L. Thomas; C. Vander Velde; P. Vanlaer; J. Wickens; V. Adler; S. Costantini; M. Grunewald; B. Klein; A. Marinov; J. Mccartin; D. Ryckbosch; F. Thyssen; M. Tytgat; L. Vanelderen; P. Verwilligen; S. Walsh; N. Zaganidis; S. Basegmez; G. Bruno; J. Caudron; L. Ceard; J. De Favereau De Jeneret; C. Delaere; P. Demin; D. Favart; A. Giammanco; G. Grégoire; J. Hollar; V. Lemaitre; J. Liao; O. Militaru; S. Ovyn; D. Pagano; A. Pin; K. Piotrzkowski; N. Schul; N. Beliy; T. Caebergs; E. Daubie; G. A. Alves; D. De Jesus Damiao; M. E. Pol; M. H. G. Souza; W. Carvalho; E. M. Da Costa; C. De Oliveira Martins; S. Fonseca De Souza; L. Mundim; H. Nogima; V. Oguri; W. L. Prado Da Silva; A. Santoro; S. M. Silva Do Amaral; A. Sznajder; F. Torres Da Silva De Araujo; F. A. Dias; M. A. F. Dias; T. R. Fernandez Perez Tomei; E. M. Gregores; F. Marinho; S. F. Novaes; Sandra S. Padula; N. Darmenov; L. Dimitrov; V. Genchev; P. Iaydjiev; S. Piperov; M. Rodozov; S. Stoykova; G. Sultanov; V. Tcholakov; R. Trayanov; I. Vankov; M. Dyulendarova; R. Hadjiiska; V. Kozhuharov; L. Litov; E. Marinova; M. Mateev; B. Pavlov; P. Petkov; J. G. Bian; G. M. Chen; H. S. Chen; C. H. Jiang; D. Liang; S. Liang; J. Wang; X. Wang; Z. Wang; M. Xu; M. Yang; J. Zang; Z. Zhang; Y. Ban; S. Guo; Y. Guo; W. Li; Y. Mao; S. J. Qian; H. Teng; L. Zhang; B. Zhu; W. Zou; A. Cabrera; B. Gomez Moreno; A. A. Ocampo Rios; A. F. Osorio Oliveros; J. C. Sanabria; N. Godinovic; D. Lelas; K. Lelas; R. Plestina; D. Polic; I. Puljak; Z. Antunovic; M. Dzelalija; V. Brigljevic; S. Duric; K. Kadija; S. Morovic; A. Attikis; M. Galanti; J. Mousa; C. Nicolaou; F. Ptochos; P. A. Razis; H. Rykaczewski; M. Finger; Y. Assran; M. A. Mahmoud; A. Hektor; M. Kadastik; K. Kannike; M. Müntel; M. Raidal; L. Rebane; V. Azzolini; P. Eerola; S. Czellar; J. Härkönen; A. Heikkinen; V. Karimäki; R. Kinnunen; J. Klem; M. J. Kortelainen; T. Lampén; K. Lassila-Perini; S. Lehti; T. Lindén; P. Luukka; T. Mäenpää; E. Tuominen; J. Tuominiemi; E. Tuovinen; D. Ungaro; L. Wendland; K. Banzuzi; A. Korpela; T. Tuuva; D. Sillou; M. Besancon; S. Choudhury; M. Dejardin; D. Denegri; B. Fabbro; J. L. Faure; F. Ferri; S. Ganjour; F. X. Gentit; A. Givernaud; P. Gras; G. Hamel de Monchenault; P. Jarry; E. Locci; J. Malcles; M. Marionneau; L. Millischer; J. Rander; A. Rosowsky; I. Shreyber; M. Titov; P. Verrecchia; S. Baffioni; F. Beaudette; L. Bianchini; M. Bluj; C. Broutin; P. Busson; C. Charlot; T. Dahms; L. Dobrzynski; R. Granier de Cassagnac; M. Haguenauer; P. Miné; C. Mironov; C. Ochando; P. Paganini; D. Sabes; R. Salerno; Y. Sirois; C. Thiebaux; B. Wyslouch; A. Zabi; J.-L. Agram; J. Andrea; A. Besson; D. Bloch; D. Bodin; J.-M. Brom; M. Cardaci; E. C. Chabert; C. Collard; E. Conte; F. Drouhin; C. Ferro; J.-C. Fontaine; D. Gelé; U. Goerlach; S. Greder; P. Juillot; M. Karim; A.-C. Le Bihan; Y. Mikami; P. Van Hove; F. Fassi; D. Mercier; C. Baty; N. Beaupere; M. Bedjidian; O. Bondu; G. Boudoul; D. Boumediene; H. Brun; N. Chanon; R. Chierici; D. Contardo; P. Depasse; H. El Mamouni; A. Falkiewicz; J. Fay; S. Gascon; B. Ille; T. Kurca; T. Le Grand; M. Lethuillier; L. Mirabito; S. Perries; V. Sordini; S. Tosi; Y. Tschudi; P. Verdier; H. Xiao; L. Megrelidze; V. Roinishvili; D. Lomidze; G. Anagnostou; M. Edelhoff; L. Feld; N. Heracleous; O. Hindrichs; R. Jussen; K. Klein; J. Merz; N. Mohr; A. Ostapchuk; A. Perieanu; F. Raupach; J. Sammet; S. Schael; D. Sprenger; H. Weber; M. Weber; B. Wittmer; M. Ata; W. Bender; M. Erdmann; J. Frangenheim; T. Hebbeker; A. Hinzmann; K. Hoepfner; C. Hof; T. Klimkovich; D. Klingebiel; P. Kreuzer; D. Lanske; C. Magass; G. Masetti; M. Merschmeyer; A. Meyer; P. Papacz; H. Pieta; H. Reithler; S. A. Schmitz; L. Sonnenschein; J. Steggemann; D. Teyssier; M. Bontenackels; M. Davids; M. Duda; G. Flügge; H. Geenen; M. Giffels; W. Haj Ahmad; D. Heydhausen; T. Kress; Y. Kuessel; A. Linn; A. Nowack; L. Perchalla; O. Pooth; J. Rennefeld

    2011-01-01

    A measurement of the angular correlations between beauty and anti-beauty hadrons () produced in pp collisions at a centre-of-mass energy of 7 TeV at the CERN LHC is presented, probing for the first time the\\u000a region of small angular separation. The B hadrons are identified by the presence of displaced secondary vertices from their\\u000a decays. The B hadron angular separation

  2. Electron-photon angular correlation in atomic physics

    Microsoft Academic Search

    K. Blum; H. Kleinpoppen

    1979-01-01

    A review is given on recent developments of electron-photon angular correlations resulting from electron impact of atoms and molecules. After a description of experimental methods the theory of measurement of electron-photon angular correlations is outlined in the following way. By applying measurements of electron-photon angular correlations a sub-ensemble of excited atoms is selected from the atomic target which can be

  3. Angular momentum exchange between coherent light and matter fields

    E-print Network

    T. P. Simula; N. Nygaard; S. X. Hu; L. A. Collins; B. I. Schneider; K. Molmer

    2007-07-25

    Full, three dimensional, time-dependent simulations are presented demonstrating the quantized transfer of angular momentum to a Bose-Einstein condensate from a laser carrying orbital angular momentum in a Laguerre-Gaussian mode. The process is described in terms of coherent Bragg scattering of atoms from a chiral optical lattice. The transfer efficiency and the angular momentum content of the output coupled vortex state are analyzed and compared with a recent experiment.

  4. Angular Momentum Transport in Clusters of Stars

    NASA Astrophysics Data System (ADS)

    Boily, Christian Marc; Spurzem, Rainer

    The evolution of rotating clusters of stars up to core-collapse is investigated with an N-body code portable to parallel architecture as well as special-purpose hardware (see Makino, J. & Taiji, M. 1998, Chichester: Wiley, 239pp). The simulations start off from axisymmetric generalisations of King profiles, with added global angular momentum. Varying the amount of rotation on input then allows a careful study of angular momentum transport over long periods of time, with a view to compare N-body results with two-dimensional Fokker-Planck models developed recently by Einsel & Spurzem (1999, MNRAS 302, 81). These authors found indications for the on-set of the `gravo-gyro' core collapse, as computed from a gas model by Hachisu (1979, PASJ 31, 523; 1982, PASJ 34, 313). Our objective is to test this scenario using a point-mass direct-integration algorithm. Recent improvements in computer algorithms, such as chain-regularisation of hierarchical two-body encounters (Mikkola & Aarseth 1998, New Astronomy 3, 309), have been incorporated in the hybrid code NBODY6++, an Ahmad-Cohen neighbour scheme based on an 4th order Hermite series expansion to integrate stellar orbits (see Aarseth, S.J. 1999, astro-ph/9901069). The code runs efficiently on CRAY T3E computer for N up to 50,000 member stars. Good statistics is obtained by ensemble-averaging m sets of N_m stars such that m x N_m ~ 50,000 à la Giersz & Heggie 1994ab, MN 268, 257; 270, 298), or by single runs with up to N = 50,000. In this contribution we report first results for mid-range simulations and summarise their observational implications.

  5. Optical resolution and the duality of light.

    PubMed

    Abramson, Nils H

    2008-07-01

    For 15 years, lensless microscopes have been constructed based on the use of holography, a digital CCD detector, and a computer for image reconstruction by use of, e.g., Fourier transformation. Thus, no lens is involved and therefore the conventional resolution limit of half the wavelength no longer applies. Instead of being limited by the wavelength, the resolution is in this case limited by how exact one can measure the phases of the light. It is remarkable that the interference-limited resolution is approximately 0.01 lambda, whereas the diffraction-limited resolution is only of the order of 0.5 lambda. It is my hope that by combining these two techniques it will be possible to increase the magnification in optical systems by at least an order of magnitude. The calculations also indicate that information does not necessarily decrease with distance. PMID:18594564

  6. Quadrupole Approximation for Para-Positronium in Relativistic Schrödinger Theory

    E-print Network

    M. Mattes; M. Sorg

    2011-09-11

    The non-relativistic energy levels of para-positronium are calculated in the quadrupole approximation of the interaction potential. This approximation technique takes into account the anisotropy of the electrostatic electron-positron interaction in the lowest order. The states due to different values of the quantum number $(l_z)$ of angular momentum are found to be no longer degenerate as is the case in the conventional theory. The physical origin of this elimination of the conventional degeneracy may intuitively be attributed to the state-dependent inertial \\emph{broadening} of the rotating charge clouds; the corresponding \\emph{anisotropic} deformation (in the quadrupole approximation) lowers then the negative electrostatic interaction energy. The result of this influence of anisotropy is that the states with $l_z=0$ adopt smaller binding energy whereas the states with maximal value of $|l_z|$ (for fixed principal quantum number $n$) have the largest binding energy within the angular momentum multiplet $(-|l_{z,\\mathrm{max}}| \\le l_z \\le |l_{z,\\mathrm{max}}|)$. This yields a certain kind of electric fine-structure splitting with the splitted RST levels being placed in a relatively narrow band around the (highly degenerated) conventional levels.

  7. Broad component of the (. pi. sup + , pp ) angular correlation

    SciTech Connect

    Yokota, H.; Igarashi, S.; Hama, K.; Mori, T.; Katsumi, T.; Ichimaru, K.; Nakayama, K.; Chiba, R. (Department of Physics, Tokyo Institute of Technology, Ohokayama, Meguro-ku, Tokyo 152, Japan (JP)); Nakai, K. (Department of Physics, Tokyo Institute of Technology, Ohokayama, Meguro-ku, Tokyo 152, Japan (JP)); Chiba, J. (National Laboratory for High Energy Physics, Oho, Tsukuba 305, Japan); and others

    1989-08-01

    The angular correlation of the ({pi}{sup +},{ital pp}) and ({pi}{sup {minus}},{ital pp}) cross sections for {sup 6}Li, {sup 7}Li, and C was measured in a wide angular range. We analyzed the structure of the ({pi}{sup +},{ital pp}) angular correlation comparing cross sections between the two reactions. It was found that the broad component of the ({pi}{sup +},{ital pp}) angular correlation is mainly due to the two-step processes associated with the two-nucleon absorption.

  8. Local computation of angular velocity in rotational visual motion

    E-print Network

    Grzywacz, Norberto

    Local computation of angular velocity in rotational visual motion Jose´ F. Barraza and Norberto M. Grzywacz Department of Biomedical Engineering and Neuroscience Graduate Program, University of Southern

  9. Angular Power Spectrum Estimation using High Performance Reconfigurable Computing

    E-print Network

    Brett Hayes; Robert Brunner; Volodymyr Kindratenko

    2007-11-14

    Angular power spectra are an important measure of the angular clustering of a given distribution. In Cosmology, they are applied to such vastly different observations as galaxy surveys that cover a fraction of the sky and the Cosmic Microwave Background that covers the entire sky, to obtain fundamental parameters that determine the structure and evolution of the universe. The calculation of an angular power spectrum, however, is complex and the optimization of these calculations is a necessary consideration for current and forthcoming observational surveys. In this work, we present preliminary results of implementing angular power spectrum estimation scheme on a high-performance reconfigurable computing platform.

  10. Orbital angular momentum mode-demultiplexing scheme with partial angular receiving aperture.

    PubMed

    Zheng, Shilie; Hui, Xiaonan; Zhu, Jiangbo; Chi, Hao; Jin, Xiaofeng; Yu, Siyuan; Zhang, Xianmin

    2015-05-01

    For long distance orbital angular momentum (OAM) based transmission, the conventional whole beam receiving scheme encounters the difficulty of large aperture due to the divergence of OAM beams. We propose a novel partial receiving scheme, using a restricted angular aperture to receive and demultiplex multi-OAM-mode beams. The scheme is theoretically analyzed to show that a regularly spaced OAM mode set remain orthogonal and therefore can be de-multiplexed. Experiments have been carried out to verify the feasibility. This partial receiving scheme can serve as an effective method with both space and cost savings for the OAM communications. It is applicable to both free space OAM optical communications and radio frequency (RF) OAM communications. PMID:25969311

  11. Angular neutron transport investigation in the HZETRN free-space ion and nucleon transport and shielding computer program

    SciTech Connect

    Singleterry, R.C. Jr. [Argonne National Lab. - West, Idaho Falls, ID (United States); Wilson, J.W. [National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center

    1997-05-01

    Extension of the high charge and energy (HZE) transport computer program HZETRN for angular transport of neutrons is considered. For this paper, only light ion transport, He{sup 4} and lighter, will be analyzed using a pure solar proton source. The angular transport calculator is the ANISN/PC program which is being controlled by the HZETRN program. The neutron flux values are compared for straight-ahead transport and angular transport in one dimension. The shield material is aluminum and the target material is water. The thickness of these materials is varied; however, only the largest model calculated is reported which is 50 gm/cm{sup 2} of aluminum and 100 gm/cm{sup 2} of water. The flux from the ANISN/PC calculation is about two orders of magnitude lower than the flux from HZETRN for very low energy neutrons. It is only a magnitude lower for the neutrons in the 10 to 20 MeV range in the aluminum and two orders lower in the water. The major reason for this difference is in the transport modes: straight-ahead versus angular. The angular treatment allows a longer path length than the straight-ahead approximation. Another reason is the different cross section sets used by the ANISN/PC-BUGLE-80 mode and the HZETRN mode. The next step is to investigate further the differences between the two codes and isolate the differences to just the angular versus straight-ahead transport mode. Then, create a better coupling between the angular neutron transport and the charged particle transport.

  12. Influence of Talc Concentration on Angular Deformation in Injection Molded Parts of Talc and Rubber Filled Polypropylene

    NASA Astrophysics Data System (ADS)

    Takahara, Tadayoshi; Koyama, Kiyohito

    Polypropylene (PP), filled with talc and rubber, is one of the most popular resins used for automotive plastic parts. The influence of talc concentration in PP compounds on the angular deformation of L-shaped specimens is discussed. The experimental and analytical results are as follows 1) Angular deformation increases sharply with increasing talc concentration until approximately 10 wt% of talc. The angle reaches a maximum at 10 wt% of talc, and then decreases above the critical concentration. 2) The shrinkage in the in-plane direction of the plate specimens shows a decrease until the talc concentration reaches approximately 10 wt%, and then becomes constant above the critical concentration. On the other hand, the shrinkage in the thickness direction increases sharply until talc concentration approaches 5 %, and then decreases gradually above that concentration. 3) The strains for each sample are calculated using Hooke's Law. In this case, the force that induces angular deformation is assumed to be the difference of shrinkage between the thickness and in-plane directions. The tendencies of calculated strains are quite qualitatively consistent with measured angular deformations. 4) A deformation angle peak can be explained by the difference of shrinkage in the thickness and in-plane directions, which increase sharply until 5 wt% talc concentration. Above this concentration, shrinkage will remain constant despite an increasing flexural modulus.

  13. Uncertainty due to quantization error in measurement of Newton's constant with the angular acceleration method

    NASA Astrophysics Data System (ADS)

    Luo, Jie; Tian, Yuan; Wang, Dian-Hong; Shao, Cheng-Gang

    2014-05-01

    The amplitude estimation of a sine signal with known frequency by the correlation method is biased in the presence of quantization error. An approximate analytical expression for the uncertainty as a function of the sine signal amplitude, the basic unit of quantization and the number of signal periods is obtained. As a comparison, the uncertainty due to general white Gaussian noise is also calculated. It is shown that in the experiment measuring G with the angular acceleration method, the uncertainty due to quantization error is evaluated to be less than that due to the additive thermal noise, which is somehow dependent on the experimental parameters.

  14. Choice of phase in the CS and IOS approximation

    SciTech Connect

    Snider, R.F.

    1982-04-01

    With the recognition that the angular momentum representations of unit position and momentum directional states must have different but uniquely related phases, the previously presented expression of scattering amplitude in terms of IOS angle dependent phase shifts must be modified. This resolves a major disagreement between IOS and close coupled degeneracy averaged differential cross sections. It is found that the phase factors appearing in the differential cross section have nothing to do with any particular choice of decoupling parameter. As a consequence, the differential cross section is relatively insensitive to the choice of CS decoupling parameter. The phase relations obtained are also in agreement with those deduced from the Born approximation.

  15. A new weighting function to achieve high temporal resolution in circular cone-beam CT with shifted detectors.

    PubMed

    Maass, Clemens; Knaup, Michael; Lapp, Robert; Karolczak, Marek; Kalender, Willi A; Kachelriess, Marc

    2008-12-01

    The size of the field of measurement (FOM) in computed tomography is limited by the size of the x-ray detector. In general, the detector is mounted symmetrically with respect to the rotation axis such that the transaxial FOM diameter approximately equals the lateral dimensions of the detector when being demagnified to the isocenter. To enlarge the FOM one may laterally shift the detector by up to 50% of its size. Well-known weighting functions must then be applied to the raw data prior to convolution and backprojection. In this case, a full scan or a scan with more than 360 degrees angular coverage is required to obtain complete data. However, there is a small region, the inner FOM, that is covered redundantly and where a partial scan reconstruction may be sufficient. A new weighting function is proposed that allows one to reconstruct partial scans in that inner FOM while it reconstructs full scan or overscan data for the outer FOM, which is the part that contains no redundancies. The presented shifted detector partial scan algorithm achieves a high temporal resolution in the inner FOM while maintaining truncation-free images for the outer part. The partial scan window can be arbitrarily shifted in the angular direction, what corresponds to shifting the temporal window of the data shown in the inner FOM. This feature allows for the reconstruction of dynamic CT data with high temporal resolution. The approach presented here is evaluated using simulated and measured data for a dual source micro-CT scanner with rotating gantry. PMID:19175145

  16. List of Court Resolutions may 13.xls RESOLUTIONS

    E-print Network

    Glasgow, University of

    List of Court Resolutions may 13.xls RESOLUTIONS SUNDRY REGULATIONS CONTAINED IN RESOLUTIONS OFTEN Regulations Page 1 #12;List of Court Resolutions may 13.xls 56 13.10.70 Foundation of the Chair of Management

  17. High-Resolution Optoelectronic Shaft-Angle Encoder

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    1994-01-01

    Improved optoelectronic encoder measures absolute angle to which shaft has been rotated. Costs little more than older, less capable encoders do, yet measures absolute angles at high resolution and does not lose absolute-angle data because generates those data anew with each reading at up to 1,000 times per second. It accumulates increments to measure total angular interval through which shaft has been turned (including unlimited number of complete turns), as long as power remains on.

  18. High resolution angle-resolved photoelectron spectrometer system

    NASA Astrophysics Data System (ADS)

    Parr, A. C.; Southworth, S. H.; Dehmer, J. L.; Holland, D. M. P.

    1984-05-01

    The design and construction details for a new high resolution, angle-resolved electron spectrometer system specifically designed for use on the National Bureau of Standards' synchrotron radiation facility (SURF-II) are described. The system features two 10.2 cm mean-radius hemispherical electron energy analyzers in a cryogenically-pumped, magnetically-shielded chamber and may be used to measure vibrationally resolved photoelectron branching ratios and angular distributions from small molecules.

  19. Changes in angular momentum during the tennis serve.

    PubMed

    Bahamonde, R E

    2000-08-01

    Three-dimensional cinematography and the direct linear transformation method were used to obtain the coordinates of the landmarks of five right-handed collegiate tennis players. A 15-segment model was used to calculate the total body angular momentum about three orthogonal axes (X, parallel to the baseline; Y, normal to baseline and pointing towards the net; and Z, pointing upwards) passing through the centre of mass and to obtain the segmental contribution of the trunk, arms and legs. Most of the clockwise angular momentum about the X-axis was concentrated in the trunk and the racket-arm. Between the events of maximum external rotation and ball impact, the clockwise angular momentum about the X-axis of rotation of most body segments was reduced and the racket-arm gained clockwise angular momentum. The body angular momentum about the Y-axis of rotation had two distinct patterns and was the result of the lateral rotation of the trunk as the racket shoulder was elevated in preparation for impact. This body angular momentum was clockwise from the event of maximum external rotation to impact for the players with the greatest ball speed, whereas it was counterclockwise for the other players. The angular momentum about the Z-axis of rotation was small and lacked a consistent pattern. The largest source of angular momentum in the tennis serve derives from the remote angular momentum about the X- and Y-axes of rotation, which are then transferred from the trunk to the racket-arm and finally to the racket. Near impact, most of the angular momentum (75.1%) was concentrated in the racket-arm. Of the angular momentum of the racket-arm, the largest percentages were concentrated in the racket (35.9%) and the forearm segment (25.7%). PMID:10972409

  20. Approximate equivalence and approximate synchronization of metric transition systems

    Microsoft Academic Search

    A. Agung Julius; George J. Pappas

    2006-01-01

    In this paper, we consider metric transition systems which are transition systems equipped with metrics for observation and synchronization labels. The existence of metrics leads to the introduction of two new concepts, (i) (epsi, delta)-approximate (bi)simulation of transition systems and (ii) approximate synchronization of transition systems. We show that the notion of (epsi, delta)-approximate (bi)simulation can be thought of as