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Sample records for spaced spherical perfect

  1. Spherically symmetric Einstein-aether perfect fluid models

    SciTech Connect

    Coley, Alan A.; Latta, Joey; Leon, Genly; Sandin, Patrik E-mail: genly.leon@ucv.cl E-mail: lattaj@mathstat.dal.ca

    2015-12-01

    We investigate spherically symmetric cosmological models in Einstein-aether theory with a tilted (non-comoving) perfect fluid source. We use a 1+3 frame formalism and adopt the comoving aether gauge to derive the evolution equations, which form a well-posed system of first order partial differential equations in two variables. We then introduce normalized variables. The formalism is particularly well-suited for numerical computations and the study of the qualitative properties of the models, which are also solutions of Horava gravity. We study the local stability of the equilibrium points of the resulting dynamical system corresponding to physically realistic inhomogeneous cosmological models and astrophysical objects with values for the parameters which are consistent with current constraints. In particular, we consider dust models in (β−) normalized variables and derive a reduced (closed) evolution system and we obtain the general evolution equations for the spatially homogeneous Kantowski-Sachs models using appropriate bounded normalized variables. We then analyse these models, with special emphasis on the future asymptotic behaviour for different values of the parameters. Finally, we investigate static models for a mixture of a (necessarily non-tilted) perfect fluid with a barotropic equations of state and a scalar field.

  2. Dynamical systems approach to relativistic spherically symmetric static perfect fluid models

    NASA Astrophysics Data System (ADS)

    Heinzle, J. Mark; Röhr, Niklas; Uggla, Claes

    2003-11-01

    We investigate relativistic spherically symmetric static perfect fluid models with barotropic equations of state that are asymptotically polytropic and linear at low and high pressures, respectively. We generalize standard work on Newtonian polytropes to a relativistic setting and to a much larger class of equations of state. This is accomplished by introducing dimensionless variables that are asymptotically homology invariant in the low pressure regime, which yields a reformulation of the field equations into a regular dynamical system on a three-dimensional compact state space. A global picture of the solution space is thus obtained which makes it possible to derive qualitative features and to prove theorems about mass radius properties. Moreover, the framework is also suited for numerical computations, as illustrated by several numerical examples, e.g., the ideal neutron gas and examples that involve phase transitions.

  3. Scattering by a thin multicoated perfectly conducting spherical shell with a circular aperture

    NASA Astrophysics Data System (ADS)

    Said, R. A.; Hamid, M.

    1992-03-01

    An analytic solution is presented for the problem of an infinitely thin perfectly conducting spherical shell with a circular aperture of arbitrary angle cut into the shell, filled with a dielectric, and coated by different thicknesses of spherical dielectric layers. The fields in all regions are expanded in terms of spherical wave functions and the boundary conditions of the continuity of the tangential fields at the dielectric-dielectric and dielectric-free-space boundaries are applied to express the expansion coefficients of the first dielectric layer in terms of the scattering coefficients. To approximate the modal expansion coefficients, the least-square error method is applied to the equations resulting from matching the fields through the aperture. Different numerical results for the simple case of a single coating layer are obtained in the form of amplitude patterns for the aperture and scattered fields versus angle as well as the backward- and forward-scattering cross sections for different loadings as functions of cavity size.

  4. A perfect launch of Space Shuttle Discovery

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Discovery lifts off Launch Pad 39A against a backdrop of xenon lights (just above the orbiter' nose and at left). On the Mobile Launcher Platform beneath, water begins flooding the area for flame and sound control. The perfect on- time liftoff occurred at 7:17 p.m. EDT, sending a crew of seven on the 100th launch in the history of the Shuttle program. Discovery carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.

  5. Application of Convolution Perfectly Matched Layer in MRTD scattering model for non-spherical aerosol particles and its performance analysis

    NASA Astrophysics Data System (ADS)

    Hu, Shuai; Gao, Taichang; Li, Hao; Yang, Bo; Jiang, Zidong; Liu, Lei; Chen, Ming

    2017-10-01

    The performance of absorbing boundary condition (ABC) is an important factor influencing the simulation accuracy of MRTD (Multi-Resolution Time-Domain) scattering model for non-spherical aerosol particles. To this end, the Convolution Perfectly Matched Layer (CPML), an excellent ABC in FDTD scheme, is generalized and applied to the MRTD scattering model developed by our team. In this model, the time domain is discretized by exponential differential scheme, and the discretization of space domain is implemented by Galerkin principle. To evaluate the performance of CPML, its simulation results are compared with those of BPML (Berenger's Perfectly Matched Layer) and ADE-PML (Perfectly Matched Layer with Auxiliary Differential Equation) for spherical and non-spherical particles, and their simulation errors are analyzed as well. The simulation results show that, for scattering phase matrices, the performance of CPML is better than that of BPML; the computational accuracy of CPML is comparable to that of ADE-PML on the whole, but at scattering angles where phase matrix elements fluctuate sharply, the performance of CPML is slightly better than that of ADE-PML. After orientation averaging process, the differences among the results of different ABCs are reduced to some extent. It also can be found that ABCs have a much weaker influence on integral scattering parameters (such as extinction and absorption efficiencies) than scattering phase matrices, this phenomenon can be explained by the error averaging process in the numerical volume integration.

  6. A new and quite general existence proof for static and spherically symmetric perfect fluid stars in general relativity

    NASA Astrophysics Data System (ADS)

    Pfister, Herbert

    2011-04-01

    In comparison to previous existence proofs for static and spherically symmetric perfect fluid stars in general relativity the new proof applies to a more general class of equations of state. In the star's interior we allow for piecewise Lipschitz continuous functions, including in this way the physically important case of phase transitions. Near the star's surface we allow for even more general functions, thereby including a large class of polytropic equations of state. Furthermore, the proof technique proceeds along standard techniques of functional analysis (Banach's fixed point theorem), and therefore applies in a similar manner to static stars in Newtonian gravity, and perhaps to rotating Newtonian and Einsteinian stars. In detail, the Einstein field equations for static perfect fluid stars are transformed to a system of coupled nonlinear integral equations being valid equally in the matter region and in the vacuum exterior. These integral equations are interpreted as a mapping in a Banach space. With the standard iteration technique, beginning with appropriate start functions, it is proven that the mapping has a unique fixed point, and that the solutions have appropriate regularity properties determined by the properties of the equation of state. The introduction gives an overview of earlier work on such systems, on the question of sphericity of static fluid stars, and on possible extensions of the above methods to rotating Newtonian and Einsteinian stars. An outlook addresses the question whether our proof method may be extensible to piecewise Hölder continuous equations of state.

  7. Weathering a Perfect Storm from Space

    USGS Publications Warehouse

    Love, Jeffrey J.

    2016-01-01

    Extreme space-weather events — intense solar and geomagnetic storms — have occurred in the past: most recently in 1859, 1921 and 1989. So scientists expect that, sooner or later, another extremely intense spaceweather event will strike Earth again. Such storms have the potential to cause widespread interference with and damage to technological systems. A National Academy of Sciences study projects that an extreme space-weather event could end up costing the American economy more than $1 trillion. The question now is whether or not we will take the actions needed to avoid such expensive consequences. Let’s assume that we do. Below is an imagined scenario of how, sometime in the future, an extreme space-weather event might play out.

  8. Genericity aspects of black hole formation in the collapse of spherically symmetric slightly inhomogeneous perfect fluids

    NASA Astrophysics Data System (ADS)

    Satin, Seema; Malafarina, Daniele; Joshi, Pankaj S.

    2016-12-01

    We study the complete gravitational collapse of a class of spherically symmetric inhomogeneous perfect fluid models obtained by introducing small radial perturbations in an otherwise homogeneous matter cloud. Our aim here is to study the genericity and stability of the formation of black holes and locally naked singularities in collapse. While the occurrence of naked singularities is known for many models of collapse, the key issue now in focus is genericity and stability of these outcomes. Towards this purpose, we study how the introduction of a somewhat general class of small inhomogeneities in homogeneous collapse leading to a black hole can change the final outcome to a naked singularity. The key feature that we assume for the perturbation profile is that of a mass profile that is separable in radial and temporal coordinates. The known models of dust and homogeneous perfect fluid collapse can be obtained from this choice of the mass profile as special cases. This choice is very general and physically well motivated and we show that this class of collapse models leads to the formation of a naked singularity as the final state.

  9. Tensor Spherical and Pseudo-Spherical Harmonics in Four-Dimensional Spaces

    NASA Astrophysics Data System (ADS)

    Tomita, K.

    1982-07-01

    Explicit expressions for tensor spherical harmonics on the 3 sphere in the four-dimensional Euclidean space are derived, and extended to derive those for pseudo-spherical harmonics. They are useful for the analyses of large-scale perturbations in the Friedmann universe models.

  10. Homogeneous near-perfect invisible ground and free space cloak

    NASA Astrophysics Data System (ADS)

    Fazeli, Mohamad; Sedighy, Seyyed Hassan; Hassani, Hamid Reza

    2017-04-01

    A general approach to design near perfect invisible ground and free space cloaks is introduced in this paper. The proposed method which is based on the optical transformation theory, leads to homogeneous constitutive parameters for the cloaks without any singularities. Moreover, the single-step mapping process with linear relations achieves an uncomplicated designing process. Invisibility performance obtained by using this approach does not depend on the incident wave direction, also. The simplicity and design flexibility of the introduced approach with the homogeneity of extracted parameters greatly facilitate the design and fabrication processes of the both proposed ground and free space invisible cloaks. The numerical simulations prove the capability and universality of the proposed design approach.

  11. Space Radiation Detector with Spherical Geometry

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D. (Inventor); Fralick, Gustave C. (Inventor); Wrbanek, Susan Y. (Inventor)

    2011-01-01

    A particle detector is provided, the particle detector including a spherical Cherenkov detector, and at least one pair of detector stacks. In an embodiment of the invention, the Cherenkov detector includes a sphere of ultraviolet transparent material, coated by an ultraviolet reflecting material that has at least one open port. The Cherenkov detector further includes at least one photodetector configured to detect ultraviolet light emitted from a particle within the sphere. In an embodiment of the invention, each detector stack includes one or more detectors configured to detect a particle traversing the sphere.

  12. Space Radiation Detector with Spherical Geometry

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D. (Inventor); Fralick, Gustave C. (Inventor); Wrbanek, Susan Y. (Inventor)

    2012-01-01

    A particle detector is provided, the particle detector including a spherical Cherenkov detector, and at least one pair of detector stacks. In an embodiment of the invention, the Cherenkov detector includes a sphere of ultraviolet transparent material, coated by an ultraviolet reflecting material that has at least one open port. The Cherenkov detector further includes at least one photodetector configured to detect ultraviolet light emitted from a particle within the sphere. In an embodiment of the invention, each detector stack includes one or more detectors configured to detect a particle traversing the sphere.

  13. Free-space optical communication link using perfect vortex beams carrying orbital angular momentum (OAM)

    NASA Astrophysics Data System (ADS)

    Zhu, Fuquan; Huang, Sujuan; Shao, Wei; Zhang, Jie; Chen, Musheng; Zhang, Weibing; Zeng, Junzhang

    2017-08-01

    We experimentally demonstrate a free-space optical communication link using perfect vortex beams. Perfect vortex beams with different topological charges are generated using a phase-modulation-type spatial light modulator (SLM) loaded with novel phase holograms based on the Bessel function. With the help of a microscope objective and simple lens, perfect vortex beams are transmitted effectively for a certain distance. After completing the demodulation of perfect vortex beams carrying OFDM 16-QAM signals and a series of offline processing on the Gaussian bright spot demodulated from the perfect vortex beams, we also achieve a communication link. The constellations and mean bit error rates (BER) of subcarriers are shown.

  14. A global conformal extension theorem for perfect fluid Bianchi space-times

    SciTech Connect

    Luebbe, Christian Tod, Paul

    2008-12-15

    A global extension theorem is established for isotropic singularities in polytropic perfect fluid Bianchi space-times. When an extension is possible, the limiting behaviour of the physical space-time near the singularity is analysed.

  15. Photoelectric sheath formation around small spherical objects in space

    SciTech Connect

    Misra, Shikha Sodha, M. S.; Mishra, S. K.

    2015-04-15

    The formation of a photoelectron sheath around positively charged small (∼cm) spherical objects roaming in near earth space due to the solar radiation (with continuous spectrum) and the solar wind plasma has been investigated. The sheath structure has been derived, taking into account anisotropic photoelectron flux with the Poisson equation, spherical geometry of the object, and half Fermi Dirac distribution of photoelectron velocities. Two cases, viz., when the object is illuminated by (i) isotropic or (ii) unidirectional (parallel beam) radiation, have been analyzed. The analysis predicts a spherically symmetric sheath in case of isotropic illumination, while a symmetry in sheath about a θ=π/4 is seen in case of parallel beam illumination; θ is the angle of incidence which is the angle made by the normal to a surface element with the direction of incidence of solar radiation. The radial and angular profiles of the electric potential and electron density in the photoelectron sheath have been evaluated and illustrated graphically; the dependence of the sheath structure on the solar wind plasma parameters, material properties of the spherical object, and its size have been discussed.

  16. The Perfect Field Trip for International Space Year.

    ERIC Educational Resources Information Center

    Hofman, Helenmarie

    1992-01-01

    Provides a poster containing activities that are part of the International Space Year. Describes activities in which students visit a local planetarium and re-create a National Aeronautic and Space Administration (NASA) space flight using reports, articles, NASA slides, and videos. Lists organizations, publications, and other resources related to…

  17. The Perfect Field Trip for International Space Year.

    ERIC Educational Resources Information Center

    Hofman, Helenmarie

    1992-01-01

    Provides a poster containing activities that are part of the International Space Year. Describes activities in which students visit a local planetarium and re-create a National Aeronautic and Space Administration (NASA) space flight using reports, articles, NASA slides, and videos. Lists organizations, publications, and other resources related to…

  18. Perfect launch for Space Shuttle Discovery on mission STS-105

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- Trailing a fiery-looking column of smoke, Space Shuttle Discovery hurtles into a blue sky on mission STS-105 to the International Space Station. Viewed from the top of the Vehicle Assembly Building, liftoff occurred at 5:10:14 p.m. EDT on this second launch attempt. Launch countdown activities for the 12-day mission were called off Aug. 9 during the T-9 minute hold due to the high potential for lightning, a thick cloud cover and the potential for showers. Besides the Shuttle crew of four, Discovery carries the Expedition Three crew who will replace Expedition Two on the International Space Station. The mission includes the third flight of an Italian-built Multi-Purpose Logistics Module delivering additional scientific racks, equipment and supplies for the Space Station, and two spacewalks. Part of the payload is the Early Ammonia Servicer (EAS) tank, which will be attached to the Station during the spacewalks. The EAS contains spare ammonia for the Station'''s cooling system. The three-member Expedition Two crew will be returning to Earth aboard Discovery after a five-month stay on the Station.

  19. Perfect launch for Space Shuttle Discovery on mission STS-105

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- Smoke billows out from Launch Pad 39A as Space Shuttle Discovery soars into the blue sky on mission STS-105 to the International Space Station. Liftoff occurred at 5:10:14 p.m. EDT on this second launch attempt. Launch countdown activities for the 12-day mission were called off Aug. 9 during the T-9 minute hold due to the high potential for lightning, a thick cloud cover and the potential for showers. Besides the Shuttle crew of four, Discovery carries the Expedition Three crew who will replace Expedition Two on the International Space Station. The mission includes the third flight of an Italian-built Multi-Purpose Logistics Module delivering additional scientific racks, equipment and supplies for the Space Station, and two spacewalks. Part of the payload is the Early Ammonia Servicer (EAS) tank, which will be attached to the Station during the spacewalks. The EAS contains spare ammonia for the Station'''s cooling system. The three-member Expedition Two crew will be returning to Earth aboard Discovery after a five-month stay on the Station.

  20. Perfect launch for Space Shuttle Discovery on mission STS-105

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. -- Viewed from between the trees, Space Shuttle Discovery rises above the smoke as it soars into the blue sky on mission STS-105 to the International Space Station. Viewed from the top of the Vehicle Assembly Building, liftoff occurred at 5:10:14 p.m. EDT on this second launch attempt. Launch countdown activities for the 12-day mission were called off Aug. 9 during the T-9 minute hold due to the high potential for lightning, a thick cloud cover and the potential for showers. Besides the Shuttle crew of four, Discovery carries the Expedition Three crew who will replace Expedition Two on the International Space Station. The mission includes the third flight of an Italian-built Multi-Purpose Logistics Module delivering additional scientific racks, equipment and supplies for the Space Station, and two spacewalks. Part of the payload is the Early Ammonia Servicer (EAS) tank, which will be attached to the Station during the spacewalks. The EAS contains spare ammonia for the Station'''s cooling system. The three-member Expedition Two crew will be returning to Earth aboard Discovery after a five-month stay on the Station.

  1. Horizons versus singularities in spherically symmetric space-times

    SciTech Connect

    Bronnikov, K. A.; Elizalde, E.; Odintsov, S. D.; Zaslavskii, O. B.

    2008-09-15

    We discuss different kinds of Killing horizons possible in static, spherically symmetric configurations and recently classified as 'usual', 'naked', and 'truly naked' ones depending on the near-horizon behavior of transverse tidal forces acting on an extended body. We obtain the necessary conditions for the metric to be extensible beyond a horizon in terms of an arbitrary radial coordinate and show that all truly naked horizons, as well as many of those previously characterized as naked and even usual ones, do not admit an extension and therefore must be considered as singularities. Some examples are given, showing which kinds of matter are able to create specific space-times with different kinds of horizons, including truly naked ones. Among them are fluids with negative pressure and scalar fields with a particular behavior of the potential. We also discuss horizons and singularities in Kantowski-Sachs spherically symmetric cosmologies and present horizon regularity conditions in terms of an arbitrary time coordinate and proper (synchronous) time. It turns out that horizons of orders 2 and higher occur in infinite proper times in the past or future, but one-way communication with regions beyond such horizons is still possible.

  2. Separating expansion from contraction in spherically symmetric models with a perfect fluid: Generalization of the Tolman-Oppenheimer-Volkoff condition and application to models with a cosmological constant

    SciTech Connect

    Mimoso, Jose P.; Le Delliou, Morgan; Mena, Filipe C.

    2010-06-15

    We investigate spherically symmetric perfect-fluid spacetimes and discuss the existence and stability of a dividing shell separating expanding and collapsing regions. We perform a 3+1 splitting and obtain gauge invariant conditions relating the intrinsic spatial curvature of the shells to the Misner-Sharp mass and to a function of the pressure that we introduce and that generalizes the Tolman-Oppenheimer-Volkoff equilibrium condition. We find that surfaces fulfilling those two conditions fit, locally, the requirements of a dividing shell, and we argue that cosmological initial conditions should allow its global validity. We analyze the particular cases of the Lemaitre-Tolman-Bondi dust models with a cosmological constant as an example of a cold dark matter model with a cosmological constant ({Lambda}-CDM model) and its generalization to contain a central perfect-fluid core. These models provide simple but physically interesting illustrations of our results.

  3. Spherically Symmetric Space Time with Regular de Sitter Center

    NASA Astrophysics Data System (ADS)

    Dymnikova, Irina

    We formulate the requirements which lead to the existence of a class of globally regular solutions of the minimally coupled GR equations asymptotically de Sitter at the center. The source term for this class, invariant under boosts in the radial direction, is classified as spherically symmetric vacuum with variable density and pressure Tμ ν vac associated with an r-dependent cosmological term Λ μ ν = 8π GTμ ν vac, whose asymptotic at the origin, dictated by the weak energy condition, is the Einstein cosmological term Λgμν, while asymptotic at infinity is de Sitter vacuum with λ < Λ or Minkowski vacuum. For this class of metrics the mass m defined by the standard ADM formula is related to both the de Sitter vacuum trapped at the origin and the breaking of space time symmetry. In the case of the flat asymptotic, space time symmetry changes smoothly from the de Sitter group at the center to the Lorentz group at infinity through radial boosts in between. Geometry is asymptotically de Sitter as r → 0 and asymptotically Schwarzschild at large r. In the range of masses m ≥ mcrit, the de Sitter Schwarzschild geometry describes a vacuum nonsingular black hole (ΛBH), and for m < mcrit it describes G-lump — a vacuum selfgravitating particle-like structure without horizons. In the case of de Sitter asymptotic at infinity, geometry is asymptotically de Sitter as r → 0 and asymptotically Schwarzschild de Sitter at large r. Λμν geometry describes, dependently on parameters m and q = √ {Λ /λ } and choice of coordinates, a vacuum nonsingular cosmological black hole, self-gravitating particle-like structure at the de Sitter background λgμν, and regular cosmological models with cosmological constant evolving smoothly from Λ to λ.

  4. The quantum free particle on spherical and hyperbolic spaces: A curvature dependent approach. II

    SciTech Connect

    Carinena, Jose F.; Ranada, Manuel F.; Santander, Mariano

    2012-10-15

    This paper is the second part of a study of the quantum free particle on spherical and hyperbolic spaces by making use of a curvature-dependent formalism. Here we study the analogues, on the three-dimensional spherical and hyperbolic spaces, S{sub {kappa}}{sup 3} ({kappa} > 0) and H{sub k}{sup 3} ({kappa} < 0), to the standard spherical waves in E{sup 3}. The curvature {kappa} is considered as a parameter and for any {kappa} we show how the radial Schroedinger equation can be transformed into a {kappa}-dependent Gauss hypergeometric equation that can be considered as a {kappa}-deformation of the (spherical) Bessel equation. The specific properties of the spherical waves in the spherical case are studied with great detail. These have a discrete spectrum and their wave functions, which are related with families of orthogonal polynomials (both {kappa}-dependent and {kappa}-independent), and are explicitly obtained.

  5. On Relativistic Space Charge Limited Current in Planar, Cylindrical, and Spherical Diodes

    DTIC Science & Technology

    2016-07-01

    AFRL-RD-PS- AFRL-RD-PS- TP-2016-0015 TP-2016-0015 ON RELATIVISTIC SPACE CHARGE LIMITED CURRENT IN PLANAR, CYLINDRICAL, AND SPHERICAL DIODES...01-06-2016 4. TITLE AND SUBTITLE On Relativistic Space Charge Limited Current in Planar, Cylindrical, and Spherical Diodes 5a. CONTRACT NUMBER IN...where ra and rc are, respectively, the anode and cathode radius. 15. SUBJECT TERMS space charge limit, emission, current, relativistic 16. SECURITY

  6. Integral Equation Space-Energy Flux Synthesis for Spherical Systems.

    DTIC Science & Technology

    1979-09-01

    flux distribution eigenfunction An eigenvalue associated with in(r) n(E) neutron number density in units...technique for obtaining the spatial and energy neutron flux distributions in multiplying systems. In IES, the integral form of the neutron transport... FLUX SYNTHESIS FOR SPHERICAL SYSTEMS I. Introduction The calculations of neutron flux distributions and neutron growth rate (a) for multiplying

  7. A perfect night-time launch of Space Shuttle Discovery on mission STS-92

    NASA Technical Reports Server (NTRS)

    2000-01-01

    In a perfect on-time launch at 7:17 p.m. EDT, Space Shuttle Discovery leaps free of Earth as its solid rocket boosters hurl it into the night sky. The launch of mission STS-92 carries a crew of seven on a construction flight to the International Space Station. Discovery also carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.

  8. A perfect night-time launch of Space Shuttle Discovery on mission STS-92

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Discovery hurtles into the night sky, trailing a tail of fire from the solid rocket boosters, after a perfect on- time launch at 7:17 p.m. EDT. The launch of mission STS-92 carries a crew of seven on a construction flight to the International Space Station. Discovery also carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT. [Photo taken with Nikon D1 camera.

  9. A perfect night-time launch of Space Shuttle Discovery on mission STS-92

    NASA Technical Reports Server (NTRS)

    2000-01-01

    In a perfect on-time launch at 7:17 p.m. EDT, Space Shuttle Discovery trails a blaze of flame amid clouds of smoke and steam as it leaps into the night sky. The launch of mission STS-92 carries a crew of seven on a construction flight to the International Space Station. Discovery also carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.

  10. General Dynamical Equations for Dingle's Space-Times Filled with a Charged Non-perfect Fluid

    NASA Astrophysics Data System (ADS)

    Hasmani, A. H.

    2009-12-01

    In this paper we have assumed charged non-perfect fluid as the material content of the space-time. The expression for the “ mass function- M( r, y, z, t)” is obtained for the general situation and the contributions from the Ricci tensor in the form of material energy density ρ, pressure anisotropy [p2+p3/2-p1] , electromagnetic field energy ℰ and the conformal Weyl tensor, viz. energy density of the free gravitational field ɛ (=-3Ψ2/4π) are made explicit. This work is an extension of the work obtained earlier by Rao and Hasmani (Math. Today XIIA:71, 1993; New Directions in Relativity and Cosmology, Hadronic Press, Nonantum, 1997) for deriving general dynamical equations for Dingle’s space-times described by this most general orthogonal metric, ds^2=exp(ν)dt^2-exp(λ)dr^2-exp(2α)dy^2-exp(2β)dz^2, where ν, λ, α and β are functions of all four space-time variables r, y, z and t.

  11. The Research of Spherical Door Shroud in Huge Space Environmental Simulator

    NASA Astrophysics Data System (ADS)

    Hua, Tong; Ran, Liu; Ming, Chen Jin

    The article mainly introduces the research for a spherical shroud used in a huge space environmental simulator. The shroud is of the pipe-sheet structure with stainless pipes welded along copper fins. In order to enlarge the capacity of the experiment, the door shroud adopts spherical structure. We used a simulator to optimize the structured design. The pressure drop and temperature pattern of the fluid also have been checked to ensure the performance index of the shroud. The shroud is divided into several pieces to manufacture. The pieces are assembled while transporting to site. This way can solve the problem of large dimension equipment's transportation.

  12. Equilibrium points of the tilted perfect fluid Bianchi VIh state space

    NASA Astrophysics Data System (ADS)

    Apostolopoulos, Pantelis S.

    2005-05-01

    We present the full set of evolution equations for the spatially homogeneous cosmologies of type VIh filled with a tilted perfect fluid and we provide the corresponding equilibrium points of the resulting dynamical state space. It is found that only when the group parameter satisfies h > -1 a self-similar solution exists. In particular we show that for h > -{1/9} there exists a self-similar equilibrium point provided that γ ∈ ({2(3+sqrt{-h})/5+3sqrt{-h}},{3/2}) whereas for h < -{frac 19} the state parameter belongs to the interval γ ∈(1,{2(3+sqrt{-h})/5+3sqrt{-h}}). This family of new exact self-similar solutions belongs to the subclass nαα = 0 having non-zero vorticity. In both cases the equilibrium points have a six-dimensional stable manifold and may act as future attractors at least for the models satisfying nαα = 0. Also we give the exact form of the self-similar metrics in terms of the state and group parameter. As an illustrative example we provide the explicit form of the corresponding self-similar radiation model (γ = {frac 43}), parametrised by the group parameter h. Finally we show that there are no tilted self-similar models of type III and irrotational models of type VIh.

  13. Spherical Primary Optical Telescope (SPOT): An Architecture Demonstration for Cost-effective Large Space Telescopes

    NASA Technical Reports Server (NTRS)

    Feinberg, Lee D.; Hagopian, John; Budinoff, Jason; Dean, Bruce; Howard, Joe

    2004-01-01

    This paper summarizes efforts underway at the Goddard Space Flight Center to demonstrate a new type of space telescope architecture that builds on the rigid segmented telescope heritage of the James Webb Space Telescope but that solves several key challenges for future space telescopes. The architecture is based on a cost-effective segmented spherical primary mirror combined with a unique wavefront sensing and control system that allows for continuous phasing of the primary mirror. The segmented spherical primary allows for cost-effective 3-meter class (e.g., Midex and Discovery) missions as well as enables 30-meter telescope solutions that can be manufactured in a reasonable amount of time and for a reasonable amount of money. The continuous wavefront sensing and control architecture enables missions in low-earth-orbit and missions that do not require expensive stable structures and thermal control systems. For the 30-meter class applications, the paper discusses considerations for assembling and testing the telescopes in space. The paper also summarizes the scientific and technological roadmap for the architecture and also gives an overview of technology development, design studies, and testbed activities underway to demonstrate its feasibility.

  14. Spherical Primary Optical Telescope (SPOT): An Architecture Demonstration for Cost-effective Large Space Telescopes

    NASA Technical Reports Server (NTRS)

    Feinberg, Lee; Hagopian, John; Budinoff, Jason; Dean, Bruce; Howard, Joe

    2005-01-01

    This paper summarizes efforts underway at the Goddard Space Flight Center to demonstrate a new type of space telescope architecture that builds on the rigid, segmented telescope heritage of the James Webb Space Telescope but that solves several key challenges for future space telescopes. The architecture is based on a cost-effective segmented spherical primary mirror combined with a unique wavefront sensing and control system that allows for continuous phasing of the primary mirror. The segmented spherical primary allows for cost-effective 3-meter class (eg, Midex and Discovery) missions as well as enables 30-meter telescope solutions that can be manufactured in a reasonable amount of time and for a reasonable amount of money. The continuous wavefront sensing and control architecture enables missions in low-earth-orbit and missions that do not require expensive stable structures and thermal control systems. For the 30-meter class applications, the paper discusses considerations for assembling and testing the telescopes in space. The paper also summarizes the scientific and technological roadmap for the architecture and also gives an overview of technology development, design studies, and testbed activities underway to demonstrate it s feasibility.

  15. New simple explicit solutions of perfect-fluid hydrodynamics and phase-space evolution

    SciTech Connect

    Nagy, M. I.

    2011-05-15

    New exact solutions of relativistic perfect-fluid hydrodynamics are presented, including the first family of exact rotating solutions. The method used to search for them is a simultaneous investigation of the relativistic hydrodynamical equations and the collisionless Boltzmann equation. Possible connections to the evolution of hot and dense partonic matter in heavy-ion collisions is discussed.

  16. Design of spherical varied line-space gratings for a high-resolution EUV spectrometer

    NASA Technical Reports Server (NTRS)

    Harada, Tatsuo; Kita, Toshiaki; Bowyer, Stuart; Hurwitz, Mark

    1991-01-01

    A highly efficient EUV spectrograph is designed for high-resolution spectroscopic observation. The spectrograph is designed for point source astronomy in a 40-120 nm bandpass and is to be ORFEUS (Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer), scheduled for launch as the first payload of a German space platform Astro-SPAS (Astronomy Shuttle Pallet Satellite). The design uses spherical varied line-space (SVLS) grating to minimize astigmatism, coma, and spherical aberration. The effectiveness and practical feasibility of the design is proved by an SVLS grating for visible use. The image focusing properties of the SVLS grating for ORFEUS are compared to those with toroidal uniform line-space (TULS) design. The SVLS design is superior to the TULS, theoretically in resolution and image concentration, but also practically with not only fabrication ease. Four SVLS gratings with nominal groove densities of 6000, 4550, 3450, and 2616 gr./mm, and a 200 mm x 200 mm ruled area have been ruled using a numerically controlled ruling engine for use in ORFEUS.

  17. Topological entropy and renormalization group flow in 3-dimensional spherical spaces

    NASA Astrophysics Data System (ADS)

    Asorey, M.; Beneventano, C. G.; Cavero-Peláez, I.; D'Ascanio, D.; Santangelo, E. M.

    2015-01-01

    We analyze the renormalization group (RG) flow of the temperature independent term of the entropy in the high temperature limit β/a ≪ 1 of a massive field theory in 3-dimensional spherical spaces, M 3, with constant curvature 6 /a 2. For masses lower than , this term can be identified with the free energy of the same theory on M 3 considered as a 3-dimensional Euclidean space-time. The non-extensive part of this free energy, S hol, is generated by the holonomy of the spatial metric connection. We show that for homogeneous spherical spaces the holonomy entropy S hol decreases monotonically when the RG scale flows to the infrared. At the conformal fixed points the values of the holonomy entropy do coincide with the genuine topological entropies recently introduced. The monotonic behavior of the RG flow leads to an inequality between the topological entropies of the conformal field theories connected by such flow, i.e. S {top/ UV } > S {top/ IR }. From a 3-dimensional viewpoint the same term arises in the 3-dimensional Euclidean effective action and has the same monotonic behavior under the RG group flow. We conjecture that such monotonic behavior is generic, which would give rise to a 3-dimensional generalization of the c-theorem, along the lines of the 2-dimensional c-theorem and the 4-dimensional a-theorem. The conjecture is related to recent formulations of the F -theorem. In particular, the holonomy entropy on lens spaces is directly related to the topological Rényi entanglement entropy on disks of 2-dimensional flat spaces.

  18. Sensational spherical shells

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Kendall, J. M., Jr.; Bahrami, P. A.; Wang, T. G.

    1986-01-01

    Fluid-dynamic and capillary forces can be used to form nearly perfect, very small spherical shells when a liquid that can solidify is passed through an annular die to form an annular jet. Gravity and certain properties of even the most ideal materials, however, can cause slight asymmetries. The primary objective of the present work is the control of this shell formation process in earth laboratories rather than space microgravity, through the development of facilities and methods that minimize the deleterious effects of gravity, aerodynamic drag, and uncontrolled cooling. The spherical shells thus produced can be used in insulation, recyclable filter materials, fire retardants, explosives, heat transport slurries, shock-absorbing armor, and solid rocket motors.

  19. Sensational spherical shells

    NASA Technical Reports Server (NTRS)

    Lee, M. C.; Kendall, J. M., Jr.; Bahrami, P. A.; Wang, T. G.

    1986-01-01

    Fluid-dynamic and capillary forces can be used to form nearly perfect, very small spherical shells when a liquid that can solidify is passed through an annular die to form an annular jet. Gravity and certain properties of even the most ideal materials, however, can cause slight asymmetries. The primary objective of the present work is the control of this shell formation process in earth laboratories rather than space microgravity, through the development of facilities and methods that minimize the deleterious effects of gravity, aerodynamic drag, and uncontrolled cooling. The spherical shells thus produced can be used in insulation, recyclable filter materials, fire retardants, explosives, heat transport slurries, shock-absorbing armor, and solid rocket motors.

  20. Realizing "2001: A Space Odyssey": Piloted Spherical Torus Nuclear Fusion Propulsion

    NASA Technical Reports Server (NTRS)

    Williams, Craig H.; Dudzinski, Leonard A.; Borowski, Stanley K.; Juhasz, Albert J.

    2005-01-01

    A conceptual vehicle design enabling fast, piloted outer solar system travel was created predicated on a small aspect ratio spherical torus nuclear fusion reactor. The initial requirements were satisfied by the vehicle concept, which could deliver a 172 mt crew payload from Earth to Jupiter rendezvous in 118 days, with an initial mass in low Earth orbit of 1,690 mt. Engineering conceptual design, analysis, and assessment was performed on all major systems including artificial gravity payload, central truss, nuclear fusion reactor, power conversion, magnetic nozzle, fast wave plasma heating, tankage, fuel pellet injector, startup/re-start fission reactor and battery bank, refrigeration, reaction control, communications, mission design, and space operations. Detailed fusion reactor design included analysis of plasma characteristics, power balance/utilization, first wall, toroidal field coils, heat transfer, and neutron/x-ray radiation. Technical comparisons are made between the vehicle concept and the interplanetary spacecraft depicted in the motion picture 2001: A Space Odyssey.

  1. Gauge-invariant coupled gravitational, acoustical, and electromagnetic modes on most general spherical space-times

    NASA Astrophysics Data System (ADS)

    Gerlach, Ulrich H.; Sengupta, Uday K.

    1980-09-01

    The coupled Einstein-Maxwell system linearized away from an arbitrarily given spherically symmetric background space-time is reduced from its four-dimensional to a two-dimensional form expressed solely in terms of gauge-invariant geometrical perturbation objects. These objects, which besides the gravitational and electromagnetic, also include mass-energy degrees of freedom, are defined on the two-manifold spanned by the radial and time coordinates. For charged or uncharged arbitrary matter background the odd-parity perturbation equations for example, reduce to three second-order linear scalar equations driven by matter and charge inhomogeneities. These three equations describe the intercoupled gravitational, electromagnetic, and acoustic perturbational degrees of freedom. For a charged black hole in an asymptotically de Sitter space-time the gravitational and electromagnetic equations decouple into two inhomogeneous scalar wave equations.

  2. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Framed between the branches of a tree, Space Shuttle Endeavour is hurtled into space on mission STS-100. Liftoff of Endeavour on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11- day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  3. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Space Shuttle Endeavour races into space, springing forth from clouds of smoke and steam, on mission STS-100. Liftoff of the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  4. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Space Shuttle Endeavour leaps from Launch Pad 39A amid billows of smoke and steam as it races into space on mission STS-100. Liftoff of Endeavour on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  5. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Flames from Space Shuttle Endeavour light up the clouds as the Shuttle races into space on mission STS-100. Liftoff of Endeavour on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11- day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  6. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Flames from Space Shuttle Endeavour light up the clouds as the Shuttle races into space on mission STS-100. Liftoff of Endeavour on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11- day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  7. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Space Shuttle Endeavour leaps from Launch Pad 39A amid billows of smoke and steam as it races into space on mission STS-100. Liftoff of Endeavour on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  8. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Space Shuttle Endeavour races into space, springing forth from clouds of smoke and steam, on mission STS-100. Liftoff of the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  9. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Trailing a plume of smoke, Space Shuttle Endeavour pierces a small cloud, briefly lighting it from within, during launch on mission STS-100. Liftoff of the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  10. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - The brilliant exhaust of Space Shuttle Endeavour as it lifts off Launch Pad 39A reflects in the nearby water. Liftoff of STS-100 on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11- day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  11. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Space Shuttle Endeavour lifts off amid streaming jets of water and steam on mission STS-100. In the background is the Atlantic Ocean. Liftoff of Endeavour on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  12. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Spring leaves frame Space Shuttle Endeavour as the water captures the launch of mission STS-100. Liftoff of Endeavour on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  13. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Through a cloud-brushed blue sky, Space Shuttle Endeavour is hurled into space on mission STS-100. Photographers crowd the bank of the turn basin near the flag pole to capture the image on film and video. Liftoff occurred at 2:40:42 p.m. EDT on the ninth flight to the International Space Station. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  14. A perfect liftoff of Space Shuttle Endeavour on mission STS-100

    NASA Technical Reports Server (NTRS)

    2001-01-01

    KENNEDY SPACE CENTER, Fla. - Looking like a bird with its tail is on fire, Space Shuttle Endeavour, atop solid rocket boosters and an external tank, soars into a Florida blue sky as it heads for space on mission STS-100. Liftoff of Endeavour on the ninth flight to the International Space Station occurred at 2:40:42 p.m. EDT. The 11-day mission will deliver and integrate the Spacelab Logistics Pallet/Launch Deployment Assembly, which includes the Space Station Remote Manipulator System and the UHF Antenna. The mission includes two planned spacewalks for installation of the SSRMS on the Station. Also onboard is the Multi-Purpose Logistics Module Raffaello, carrying resupply stowage racks and resupply/return stowage platforms.

  15. A Spherical Torus Nuclear Fusion Reactor Space Propulsion Vehicle Concept for Fast Interplanetary Travel

    NASA Technical Reports Server (NTRS)

    Williams, Craig H.; Borowski, Stanley K.; Dudzinski, Leonard A.; Juhasz, Albert J.

    1998-01-01

    A conceptual vehicle design enabling fast outer solar system travel was produced predicated on a small aspect ratio spherical torus nuclear fusion reactor. Initial requirements were for a human mission to Saturn with a greater than 5% payload mass fraction and a one way trip time of less than one year. Analysis revealed that the vehicle could deliver a 108 mt crew habitat payload to Saturn rendezvous in 235 days, with an initial mass in low Earth orbit of 2,941 mt. Engineering conceptual design, analysis, and assessment was performed on all ma or systems including payload, central truss, nuclear reactor (including divertor and fuel injector), power conversion (including turbine, compressor, alternator, radiator, recuperator, and conditioning), magnetic nozzle, neutral beam injector, tankage, start/re-start reactor and battery, refrigeration, communications, reaction control, and in-space operations. Detailed assessment was done on reactor operations, including plasma characteristics, power balance, power utilization, and component design.

  16. A spherical torus nuclear fusion reactor space propulsion vehicle concept for fast interplanetary travel

    NASA Astrophysics Data System (ADS)

    Williams, Craig H.; Borowski, Stanley K.; Dudzinski, Leonard A.; Juhasz, Albert J.

    1999-01-01

    A conceptual vehicle design enabling fast outer solar system travel was produced predicated on a small aspect ratio spherical torus nuclear fusion reactor. Initial requirements were for a human mission to Saturn with a>5% payload mass fraction and a one way trip time of less than one year. Analysis revealed that the vehicle could deliver a 108 mt crew habitat payload to Saturn rendezvous in 235 days, with an initial mass in low Earth orbit of 2,941 mt. Engineering conceptual design, analysis, and assessment was performed on all major systems including payload, central truss, nuclear reactor (including diverter and fuel injector), power conversion (including turbine, compressor, alternator, radiator, recuperator, and conditioning), magnetic nozzle, neutral beam injector, tankage, start/re-start reactor and battery, refrigeration, communications, reaction control, and in-space operations. Detailed assessment was done on reactor operations, including plasma characteristics, power balance, and component design.

  17. Space charge effects and aberrations on electron pulse compression in a spherical electrostatic capacitor.

    PubMed

    Yu, Lei; Li, Haibo; Wan, Weishi; Wei, Zheng; Grzelakowski, Krzysztof P; Tromp, Rudolf M; Tang, Wen-Xin

    2017-07-06

    The effects of space charge, aberrations and relativity on temporal compression are investigated for a compact spherical electrostatic capacitor (α-SDA). By employing the three-dimensional (3D) field simulation and the 3D space charge model based on numerical General Particle Tracer and SIMION, we map the compression efficiency for a wide range of initial beam size and single-pulse electron number and determine the optimum conditions of electron pulses for the most effective compression. The results demonstrate that both space charge effects and aberrations prevent the compression of electron pulses into the sub-ps region if the electron number and the beam size are not properly optimized. Our results suggest that α-SDA is an effective compression approach for electron pulses under the optimum conditions. It may serve as a potential key component in designing future time-resolved electron sources for electron diffraction and spectroscopy experiments. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Stationary spherically symmetric one-kink model in Saez-Ballester theory of gravitation

    NASA Astrophysics Data System (ADS)

    Kiran, M.; Reddy, D. R. K.; Rao, V. U. M.; Bhaskara Rao, M. P. V. V.

    2015-03-01

    In this paper we consider stationary Spherically symmetric kink space-time in the scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986) in the presence of perfect fluid distribution. It is shown that spherically symmetric kink space-time does not accommodate perfect fluid distribution in this theory. Hence a vacuum model is obtained which is asymptotically flat. This model corresponds to a one kink metric in this theory. This can be considered as an analogue of usual spherically symmetric Schwarzschild case in this theory.

  19. A perfect night-time launch of Space Shuttle Discovery on mission STS-92

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Discovery rises above the lighting mast on the Fixed Service Structure as it hurtles into the night sky on mission STS-92. Discovery launched on time at 7:17 p.m. EDT. Discovery carries a crew of seven on a construction flight to the International Space Station. Discovery also carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT. [Photo taken with Nikon D1 camera.

  20. STS-103 perfect night-time landing for Space Shuttle Discovery

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The orbiter Discovery looks like a blue ghost as it drops from the darkness onto lighted runway 33 at KSC's Shuttle Landing Facility. After traveling more than 3,267,000 miles on a successful eight-day mission to service the Hubble Space Telescope, the orbiter touches down at 7:00:47 p.m. EST. Aboard are Commander Curtis L. Brown Jr., Pilot Scott J. Kelly, and Mission Specialists Steven L. Smith, C. Michael Foale (Ph.D.), John M. Grunsfeld (Ph.D.), Claude Nicollier of Switzerland and Jean-Frangois Clervoy of France, who spent the Christmas holiday in space in order to accomplish their mission before the end of 1999. During the mission, Discovery's four space-walking astronauts, Smith, Foale, Grunsfeld and Nicollier, spent 24 hours and 33 minutes upgrading and refurbishing Hubble, making it more capable than ever to renew its observations of the universe. Mission objectives included replacing gyroscopes and an old computer, installing another solid state recorder, and replacing damaged insulation in the telescope. Hubble was released from the end of Discovery's robot arm on Christmas Day. This was the 96th flight in the Space Shuttle program and the 27th for the orbiter Discovery. The landing was the 20th consecutive Shuttle landing in Florida and the 13th night landing in Shuttle program history.

  1. STS-103 perfect night-time landing for Space Shuttle Discovery

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The orbiter Discovery looks like a blue ghost as it drops from the darkness onto lighted runway 33 at KSC's Shuttle Landing Facility. After traveling more than 3,267,000 miles on a successful eight-day mission to service the Hubble Space Telescope, the orbiter touches down at 7:00:47 p.m. EST. Aboard are Commander Curtis L. Brown Jr., Pilot Scott J. Kelly, and Mission Specialists Steven L. Smith, C. Michael Foale (Ph.D.), John M. Grunsfeld (Ph.D.), Claude Nicollier of Switzerland and Jean-Frangois Clervoy of France, who spent the Christmas holiday in space in order to accomplish their mission before the end of 1999. During the mission, Discovery's four space-walking astronauts, Smith, Foale, Grunsfeld and Nicollier, spent 24 hours and 33 minutes upgrading and refurbishing Hubble, making it more capable than ever to renew its observations of the universe. Mission objectives included replacing gyroscopes and an old computer, installing another solid state recorder, and replacing damaged insulation in the telescope. Hubble was released from the end of Discovery's robot arm on Christmas Day. This was the 96th flight in the Space Shuttle program and the 27th for the orbiter Discovery. The landing was the 20th consecutive Shuttle landing in Florida and the 13th night landing in Shuttle program history.

  2. A family of anisotropic super-dense star models using a space-time describing charged perfect fluid distributions

    NASA Astrophysics Data System (ADS)

    Maurya, S. K.; Gupta, Y. K.

    2012-08-01

    A family of anisotropic fluid distributions is constructed using a space-time describing a family of charged perfect fluid distributions. The anisotropy parameter is taken to be twice the square of electric intensity used in the charged fluid distributions. As the anisotropy parameter (or the electric intensity) is zero at the centre and is monotonically increasing towards the pressure-free interface, we have utilized the anisotropic fluid distributions to create Boson-type neutron stars models which join smoothly to the Schwarzschild exterior metric. All the physical entities such as energy density, radial pressure, tangential pressure and velocity of sound are monotonically decreasing towards the surface. Different members of the above family are characterized by a positive integral number n. It is observed that the maximum mass (which is 5.8051 solar mass for n = 4) starts decreasing for n > 4. But this reaches a non-zero terminal value (2.8010 solar mass) as n tends to infinity.

  3. Analysis and implementation of a space resolving spherical crystal spectrometer for x-ray Thomson scattering experiments

    SciTech Connect

    Harding, E. C.; Ao, T.; Bailey, J. E.; Loisel, G.; Sinars, D. B.; Geissel, M.; Rochau, G. A.; Smith, I. C.

    2015-04-15

    The application of a space-resolving spectrometer to X-ray Thomson Scattering (XRTS) experiments has the potential to advance the study of warm dense matter. This has motivated the design of a spherical crystal spectrometer, which is a doubly focusing geometry with an overall high sensitivity and the capability of providing high-resolution, space-resolved spectra. A detailed analysis of the image fluence and crystal throughput in this geometry is carried out and analytical estimates of these quantities are presented. This analysis informed the design of a new spectrometer intended for future XRTS experiments on the Z-machine. The new spectrometer collects 6 keV x-rays with a spherically bent Ge (422) crystal and focuses the collected x-rays onto the Rowland circle. The spectrometer was built and then tested with a foam target. The resulting high-quality spectra prove that a spherical spectrometer is a viable diagnostic for XRTS experiments.

  4. Analysis and implementation of a space resolving spherical crystal spectrometer for x-ray Thomson scattering experiments.

    PubMed

    Harding, E C; Ao, T; Bailey, J E; Loisel, G; Sinars, D B; Geissel, M; Rochau, G A; Smith, I C

    2015-04-01

    The application of a space-resolving spectrometer to X-ray Thomson Scattering (XRTS) experiments has the potential to advance the study of warm dense matter. This has motivated the design of a spherical crystal spectrometer, which is a doubly focusing geometry with an overall high sensitivity and the capability of providing high-resolution, space-resolved spectra. A detailed analysis of the image fluence and crystal throughput in this geometry is carried out and analytical estimates of these quantities are presented. This analysis informed the design of a new spectrometer intended for future XRTS experiments on the Z-machine. The new spectrometer collects 6 keV x-rays with a spherically bent Ge (422) crystal and focuses the collected x-rays onto the Rowland circle. The spectrometer was built and then tested with a foam target. The resulting high-quality spectra prove that a spherical spectrometer is a viable diagnostic for XRTS experiments.

  5. Cylindrical and spherical space equivalents to the plane wave expansion technique of Maxwell's wave equations

    NASA Astrophysics Data System (ADS)

    Gauthier, Robert C.; Alzahrani, Mohammed A.; Jafari, Seyed Hamed

    2015-02-01

    The plane wave expansion (PWM) technique applied to Maxwell's wave equations provides researchers with a supply of information regarding the optical properties of dielectric structures. The technique is well suited for structures that display a linear periodicity. When the focus is directed towards optical resonators and structures that lack linear periodicity the eigen-process can easily exceed computational resources and time constraints. In the case of dielectric structures which display cylindrical or spherical symmetry, a coordinate system specific set of basis functions have been employed to cast Maxwell's wave equations into an eigen-matrix formulation from which the resonator states associated with the dielectric profile can be obtained. As for PWM, the inverse of the dielectric and field components are expanded in the basis functions (Fourier-Fourier-Bessel, FFB, in cylindrical and Fourier- Bessel-Legendre, BLF, in spherical) and orthogonality is employed to form the matrix expressions. The theoretical development details will be presented indicating how certain mathematical complications in the process have been overcome and how the eigen-matrix can be tuned to a specific mode type. The similarities and differences in PWM, FFB and BLF are presented. In the case of structures possessing axial cylindrical symmetry, the inclusion of the z axis component of propagation constant makes the technique applicable to photonic crystal fibers and other waveguide structures. Computational results will be presented for a number of different dielectric geometries including Bragg ring resonators, cylindrical space slot channel waveguides and bottle resonators. Steps to further enhance the computation process will be reported.

  6. LETTER TO THE EDITOR: A few remarks on integral representation for zonal spherical functions on the symmetric space ?

    NASA Astrophysics Data System (ADS)

    Cariñena, J. F.; Perelomov, A. M.

    1997-08-01

    The integral representation of the orthogonal groups for zonal spherical functions of the symmetric space 0305-4470/30/15/003/img2 is used to obtain a generating function for such functions. For the case N = 3 the three-dimensional integral representation reduces to a one-dimensional one.

  7. Perfect embezzlement of entanglement

    NASA Astrophysics Data System (ADS)

    Cleve, Richard; Liu, Li; Paulsen, Vern I.

    2017-01-01

    Van Dam and Hayden introduced a concept commonly referred to as embezzlement, where, for any entangled quantum state ϕ, there is an entangled catalyst state ψ, from which a high fidelity approximation of ϕ ⊗ ψ can be produced using only local operations. We investigate a version of this where the embezzlement is perfect (i.e., the fidelity is 1). We prove that perfect embezzlement is impossible in a tensor product framework, even with infinite-dimensional Hilbert spaces and infinite entanglement entropy. Then we prove that perfect embezzlement is possible in a commuting operator framework. We prove this using the theory of C*-algebras and we also provide an explicit construction. Next, we apply our results to analyze perfect versions of a nonlocal game introduced by Regev and Vidick. Finally, we analyze the structure of perfect embezzlement protocols in the commuting operator model, showing that they require infinite-dimensional Hilbert spaces.

  8. Spherical Harmonic Analysis of Redshift Space Distortions in the IRAS PSCZ Redshift Survey

    NASA Astrophysics Data System (ADS)

    Tadros, H.; Ballinger, W.; Heavens, A.; Taylor, A.; Efstathiou, G.; Saunders, W.; Frenk, C.; Keeble, O.; McMahon, R.; Maddox, S.; Oliver, S.; Rowan-Robinson, M.; Sutherland, W.; White, S.

    We apply the formalism of spherical harmonic decomposition to the galaxy density field of the IRAS PSCz redshift survey. Taking into account the first order distortion of the galaxy pattern due to redshift coordinates, we have measured the degree of distortion, parameterised by the distortion parameter beta ~ Omega^{0.6}/b, using maximum likelihood methods. We simultaneously measure either the undistorted amplitude of perturbations in the galaxy distribution when a parameterised power spectrum is assumed, or the shape and amplitude of the real--space power spectrum if the band--power in a set of passbands is measured in a step--wise fashion. We find that in the case of a parameterised power spectrum beta=0.59 +/- 0.26 and the amplitude of the power at wavenumber k=0.1h{Mpc}^{-1} is Delta_{0.1}=0.48 +/- 0.04 (marginal errors). Freeing the shape of the power spectrum we find that beta=0.61 +/- 0.2, and Delta_{0.1}=0.48 +/- 0.04 (conditional errors).

  9. Polypolar spherical harmonic decomposition of galaxy correlators in redshift space: Toward testing cosmic rotational symmetry

    NASA Astrophysics Data System (ADS)

    Shiraishi, Maresuke; Sugiyama, Naonori S.; Okumura, Teppei

    2017-03-01

    We propose an efficient way to test rotational invariance in the cosmological perturbations by use of galaxy correlation functions. In symmetry-breaking cases, the galaxy power spectrum can have extra angular dependence in addition to the usual one due to the redshift-space distortion, k ^ .n ^ . We confirm that, via the decomposition into not the usual Legendre basis Lℓ(k ^.n ^) but the bipolar spherical harmonic one {Yℓ(k ^)⊗Yℓ'(n ^)}LM, the symmetry-breaking signal can be completely distinguished from the usual isotropic one since the former yields nonvanishing L ≥1 modes but the latter is confined to the L =0 one. As a demonstration, we analyze the signatures due to primordial-origin symmetry breakings such as the well-known quadrupolar-type and dipolar-type power asymmetries and find nonzero L =2 and 1 modes, respectively. Fisher matrix forecasts of their constraints indicate that the Planck-level sensitivity could be achieved by the SDSS or BOSS-CMASS data, and an order-of-magnitude improvement is expected in a near future survey as PFS or Euclid by virtue of an increase in accessible Fourier mode. Our methodology is model-independent and hence applicable to the searches for various types of statistically anisotropic fluctuations.

  10. Spectral and electrical diagnosis of complex space-charge structures excited by a spherical grid cathode with orifice

    NASA Astrophysics Data System (ADS)

    Schrittwieser, R. W.; Ionita, C.; Teodorescu-Soare, C. T.; Vasilovici, O.; Gurlui, S.; Irimiciuc, S. A.; Dimitriu, D. G.

    2017-04-01

    Optical emission spectroscopy and Langmuir probes were used to diagnose complex space-charge structures that appear inside and around a spherical grid with orifice applying a negative voltage below a critical value to it. Measurements (through the orifice) delivered the axial profiles of plasma potential, electron temperature and density, and of the densities of excited atoms and ions. Thereby the formation of a double layer was found in the region near the orifice with a potential drop close to the ionisation potential of the applied gas, confirming the presence of a fireball in that region (also evidenced by visual observation), i.e. of a quasi-spherical bright plasma region consisting of a positive core (an ion-rich plasma) confined by a double layer. Spectral investigations confirmed the presence of high ion density inside the spherical grid (due to the hollow cathode effect), while outside the grid a transition region with a strong rate of ionisation and excitation processes appears. Information on the nonlinear dynamics of this space-charge structure was obtained from the analysis of the oscillations of the discharge current, as well as of the floating potential inside and outside the spherical grid. Dedicated to Hans Pécseli at the occasion of his 70th birthday, an extraordinary plasma physicist and a wonderful, noble and warm-hearted friend for more than 40 years.

  11. Relevant parameter space and stability of spherical tokamaks with a plasma center column

    NASA Astrophysics Data System (ADS)

    Lampugnani, L. G.; Garcia-Martinez, P. L.; Farengo, R.

    2017-02-01

    A spherical tokamak (ST) with a plasma center column (PCC) can be formed inside a simply connected chamber via driven magnetic relaxation. From a practical perspective, the ST-PCC could overcome many difficulties associated with the material center column of the standard ST reactor design. Besides, the ST-PCC concept can be regarded as an advanced helicity injected device that would enable novel experiments on the key physics of magnetic relaxation and reconnection. This is because the concept includes not only a PCC but also a coaxial helicity injector (CHI). This combination implies an improved level of flexibility in the helicity injection scheme required for the formation and sustainment phases. In this work, the parameter space determining the magnetic structure of the ST-PCC equilibria is studied under the assumption of fully relaxed plasmas. In particular, it is shown that the effect of the external bias field of the PCC and the CHI essentially depends on a single parameter that measures the relative amount of flux of these two entities. The effect of plasma elongation on the safety factor profile and the stability to the tilt mode are also analyzed. In the first part of this work, the stability of the system is explained in terms of the minimum energy principle, and relevant stability maps are constructed. While this picture provides an adequate insight into the underlying physics of the instability, it does not include the stabilizing effect of line-tying at the electrodes. In the second part, a dynamical stability analysis of the ST-PCC configurations, including the effect of line-tying, is performed by numerically solving the magnetohydrodynamic equations. A significant stability enhancement is observed when the PCC contains more than the 70% of the total external bias flux, and the elongation is not higher than two.

  12. Radiation pressure and Poynting-Robertson drag for small spherical particles. [in interplanetary space

    NASA Technical Reports Server (NTRS)

    Soter, S.; Burns, J. A.; Lamy, P. L.

    1977-01-01

    Robertson's expression for the velocity-dependent effect of solar radiation on the motion of small particles is difficult because of its dependence on relativistic considerations, and it is also deficient in that it assumes perfectly absorbing particles. The present paper gives a heuristic derivation of the Poynting-Robertson effect. Robertson's expression for perfectly absorbing particles is obtained but on a much simpler physical basis, and an expression is also obtained for a particle that in general scatters, transmits, and absorbs light. Some numerical results on the solar radiation forces felt by small particles of cosmochemically important compositions are given.

  13. Entanglement entropy of spherical domains in anti-de Sitter space

    NASA Astrophysics Data System (ADS)

    Krtouš, Pavel; Zelnikov, Andrei

    2014-05-01

    It was proposed by Ryu and Takayanagi that the entanglement entropy in conformal field theory (CFT) is related through the AdS/CFT correspondence to the area of a minimal surface in the bulk. We apply this holographic geometrical method of calculating the entanglement entropy to study the vacuum case of a CFT which is holographically dual to empty anti-de Sitter (AdS) spacetime. We present all possible minimal surfaces spanned on one or two spherical boundaries at AdS infinity. We give exact analytical expressions for the regularized areas of these surfaces and identify finite renormalized quantities. In the case of two disjoint boundaries the existence of two different phases of the entanglement entropy is confirmed. A trivial phase corresponds to two disconnected minimal surfaces, while the other one corresponds to a tube connecting the spherical boundaries. A transition between these phases is reminiscent of the finite temperature deconfinement transition in the CFT on the boundary. The exact analytical results are thus consistent with previous numerical and approximate computations. We also briefly discuss the character of a spacetime extension of the minimal surface spanned on two uniformly accelerated boundaries.

  14. Effect of coseismic and postseismic deformation on homogeneous and layered half-space and spherical analysis: Model simulation of the 2006 Java, Indonesia, tsunami earthquake

    NASA Astrophysics Data System (ADS)

    Gunawan, Endra; Meilano, Irwan; Hanifa, Nuraini Rahma; Widiyantoro, Sri

    2017-10-01

    We simulate surface displacements calculated on homogeneous and layered half-space and spherical models as applied to the coseismic and postseismic (afterslip and viscoelastic relaxation) of the 2006 Java tsunami earthquake. Our analysis of coseismic and afterslip deformation suggests that the homogeneous half-space model generates a much broader displacement effect than the layered half-space and spherical models. Also, though the result for surface displacements is similar for the layered half-space and spherical models, noticeable displacements still occurred on top of the coseismic fault patches. Our displacement result in afterslip modeling suggests that significant displacements occurred on top of the main afterslip fault patches, differing from the viscoelastic relaxation model, which has displacements in the front region of coseismic fault patches. We propose this characteristic as one of the important features differentiating a postseismic deformation signal from afterslip and viscoelastic relaxation detected by geodetic data.

  15. Spherical Camera

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Developed largely through a Small Business Innovation Research contract through Langley Research Center, Interactive Picture Corporation's IPIX technology provides spherical photography, a panoramic 360-degrees. NASA found the technology appropriate for use in guiding space robots, in the space shuttle and space station programs, as well as research in cryogenic wind tunnels and for remote docking of spacecraft. Images of any location are captured in their entirety in a 360-degree immersive digital representation. The viewer can navigate to any desired direction within the image. Several car manufacturers already use IPIX to give viewers a look at their latest line-up of automobiles. Another application is for non-invasive surgeries. By using OmniScope, surgeons can look more closely at various parts of an organ with medical viewing instruments now in use. Potential applications of IPIX technology include viewing of homes for sale, hotel accommodations, museum sites, news events, and sports stadiums.

  16. Propagation of transient signals from a spherical source in a half-space with surface layers

    SciTech Connect

    Norwood, F.R.

    1993-01-01

    The title problem is of particular interest for the analysis of seismic signals arising from underground nuclear explosions. Previous attempts at the solution have indicated that, although cylindrical symmetry exists, conventional methods cannot be applied because of the existence of plane and spherical boundaries. The present paper develops a ray-grouping technique for finding the solution to the title problem. This technique allows the separation of the problem into a series of canonical problems. Each such problem deals with a given boundary condition (e.g., continuity conditions at a material interface). Using this technique, one may follow waves along ray paths. It is easy to identify, after n reflections, (a) rays which arrive simultaneously at a given point and (b) the terms in the solution which need to be included at a given time. It is important to note that a cylindrical coordinate system is not employed, even though the problem is axially symmetric. Instead, the equations are carefully transformed making it possible to use a Cartesian coordinate system. This results in a spectral representation of the solution in terms of algebraic expressions in lieu of Bessel functions.

  17. Casimir Densities for Two Concentric Spherical Shells in the Global Monopole Space-Time

    NASA Astrophysics Data System (ADS)

    Saharian, A. A.; Setare, M. R.

    The quantum vacuum effects are investigated for a massive scalar field with general curvature coupling and obeying the Robin boundary conditions given on two concentric spherical shells with radii a and b in the (D+1)-dimensional global monopole background. The expressions are derived for the Wightman function, the vacuum expectation values of the field square, the vacuum energy density, radial and azimuthal stress components in the region between the shells. A regularization procedure is carried out by making use of the generalized Abel-Plana formula for the series over zeros of combinations of the cylinder functions. This formula allows us to extract from the vacuum expectation values the parts due to a single sphere on background of the global monopole gravitational field, and to present the "interference" parts in terms of exponentially convergent integrals, useful, in particular, for numerical evaluations. The vacuum forces acting on the boundaries are presented as a sum of the self-action and interaction terms. The first one contains well-known surface divergences and needs a further regularization. The interaction forces between the spheres are finite for all values a

  18. Multiscale real-space quantum-mechanical tight-binding calculations of electronic structure in crystals with defects using perfectly matched layers

    NASA Astrophysics Data System (ADS)

    Pourmatin, Hossein; Dayal, Kaushik

    2016-10-01

    We consider the scattering of incident plane-wave electrons from a defect in a crystal modeled by the time-harmonic Schrödinger equation. While the defect potential is localized, the far-field potential is periodic, unlike standard free-space scattering problems. Previous work on the Schrödinger equation has been almost entirely in free-space conditions; a few works on crystals have been in one-dimension. We construct absorbing boundary conditions for this problem using perfectly matched layers in a tight-binding formulation. Using the example of a point defect in graphene, we examine the efficiency and convergence of the proposed absorbing boundary condition.

  19. Multiscale real-space quantum-mechanical tight-binding calculations of electronic structure in crystals with defects using perfectly matched layers

    SciTech Connect

    Pourmatin, Hossein Dayal, Kaushik

    2016-10-15

    Graphical abstract: - Abstract: We consider the scattering of incident plane-wave electrons from a defect in a crystal modeled by the time-harmonic Schrödinger equation. While the defect potential is localized, the far-field potential is periodic, unlike standard free-space scattering problems. Previous work on the Schrödinger equation has been almost entirely in free-space conditions; a few works on crystals have been in one-dimension. We construct absorbing boundary conditions for this problem using perfectly matched layers in a tight-binding formulation. Using the example of a point defect in graphene, we examine the efficiency and convergence of the proposed absorbing boundary condition.

  20. Interlaced crystals having a perfect Bravais lattice and complex chemical order revealed by real-space crystallography

    SciTech Connect

    Shen, Xiao; Hernandez-Pagan, Emil; Zhou, Wu; Puzyrev, Yevgeniy S.; Idrobo Tapia, Juan Carlos; Macdonald, Janet; Pennycook, Stephen J.; Pantelides, Sokrates T.

    2014-11-14

    The search for optimal thermoelectric materials aims for structures in which the crystalline order is disrupted to lower the thermal conductivity without degradation of the electron conductivity. Here we report the synthesis and characterization of ternary nanoparticles (two cations and one anion) that exhibit a new form of crystal-line order: an uninterrupted, perfect, global Bravais lattice, in which the two cations exhibit a wide array of distinct ordering patterns within the cation sublattice, form-ing interlaced domains and phases. Partitioning into domains and phases is not unique; the corresponding boundaries have no structural defects or strain and entail no energy cost. We call this form of crystalline order “interlaced crystals” and present the example of hexagonal-CuInS2. Interlacing is possible in multi-cation tetrahedral-ly-bonded compound with an average of two electrons per bond. Interlacing has min-imal effect on electronic properties, but should strongly reduce phonon transport, making interlaced crystals attractive for thermoelectric applications.

  1. Interlaced crystals having a perfect Bravais lattice and complex chemical order revealed by real-space crystallography

    DOE PAGES

    Shen, Xiao; Hernandez-Pagan, Emil; Zhou, Wu; ...

    2014-11-14

    The search for optimal thermoelectric materials aims for structures in which the crystalline order is disrupted to lower the thermal conductivity without degradation of the electron conductivity. Here we report the synthesis and characterization of ternary nanoparticles (two cations and one anion) that exhibit a new form of crystal-line order: an uninterrupted, perfect, global Bravais lattice, in which the two cations exhibit a wide array of distinct ordering patterns within the cation sublattice, form-ing interlaced domains and phases. Partitioning into domains and phases is not unique; the corresponding boundaries have no structural defects or strain and entail no energy cost.more » We call this form of crystalline order “interlaced crystals” and present the example of hexagonal-CuInS2. Interlacing is possible in multi-cation tetrahedral-ly-bonded compound with an average of two electrons per bond. Interlacing has min-imal effect on electronic properties, but should strongly reduce phonon transport, making interlaced crystals attractive for thermoelectric applications.« less

  2. Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection

    NASA Technical Reports Server (NTRS)

    Hu, Z. W.; Thomas, B. R.; Chernov, A. A.

    2001-01-01

    Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations.

  3. Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection.

    PubMed

    Hu, Z W; Thomas, B R; Chernov, A A

    2001-06-01

    Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations.

  4. Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection

    NASA Technical Reports Server (NTRS)

    Hu, Z. W.; Thomas, B. R.; Chernov, A. A.

    2001-01-01

    Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations.

  5. The Diagnostic Value of 3-Dimensional Sampling Perfection With Application Optimized Contrasts Using Different Flip Angle Evolutions (SPACE) MRI in Evaluating Lower Extremity Deep Venous Thrombus.

    PubMed

    Wu, Gang; Xie, Ruyi; Zhang, Xiaoli; Morelli, John; Yan, Xu; Zhu, Xiaolei; Li, Xiaoming

    2017-07-12

    The aim of this study was to evaluate the diagnostic performance of noncontrast magnetic resonance imaging utilizing sampling perfection with application optimized contrasts using different flip angle evolutions (SPACE) in detecting deep venous thrombus (DVT) of the lower extremity and evaluating clot burden. This prospective study was approved by the institutional review board. Ninety-four consecutive patients (42 men, 52 women; age range, 14-87 years; average age, 52.7 years) suspected of lower extremity DVT underwent ultrasound (US) and SPACE. The venous visualization score for SPACE was determined by 2 radiologists independently according to a 4-point scale (1-4, poor to excellent). The sensitivity and specificity of SPACE in detecting DVT were calculated based on segment, limb, and patient, with US serving as the reference standard. The clot burden for each segment was scored (0-3, patent to entire segment occlusion). The clot burden score obtained with SPACE was compared with US using a Wilcoxon test based on region, limb, and patient. Interobserver agreement in assessing DVT (absent, nonocclusive, or occlusive) with SPACE was determined by calculating Cohen kappa coefficients. The mean venous visualization score for SPACE was 3.82 ± 0.50 for reader 1 and 3.81 ± 0.50 for reader 2. For reader 1, sensitivity/specificity values of SPACE in detecting DVT were 96.53%/99.90% (segment), 95.24%/99.04% (limb), and 95.89%/95.24% (patient). For reader 2, corresponding values were 97.20%/99.90%, 96.39%/99.05%, and 97.22%/95.45%. The clot burden assessed with SPACE was not significantly different from US (P > 0.05 for region, limb, patient). Interobserver agreement of SPACE in assessing thrombosis was excellent (kappa = 0.894 ± 0.014). Non-contrast-enhanced 3-dimensional SPACE magnetic resonance imaging is highly accurate in detecting lower extremity DVT and reliable in the evaluation of clot burden. SPACE could serve as an important alternative for patients in whom US

  6. Particle System Based Adaptive Sampling on Spherical Parameter Space to Improve the MDL Method for Construction of Statistical Shape Models

    PubMed Central

    Zhou, Xiangrong; Hirano, Yasushi; Tachibana, Rie; Hara, Takeshi; Kido, Shoji; Fujita, Hiroshi

    2013-01-01

    Minimum description length (MDL) based group-wise registration was a state-of-the-art method to determine the corresponding points of 3D shapes for the construction of statistical shape models (SSMs). However, it suffered from the problem that determined corresponding points did not uniformly spread on original shapes, since corresponding points were obtained by uniformly sampling the aligned shape on the parameterized space of unit sphere. We proposed a particle-system based method to obtain adaptive sampling positions on the unit sphere to resolve this problem. Here, a set of particles was placed on the unit sphere to construct a particle system whose energy was related to the distortions of parameterized meshes. By minimizing this energy, each particle was moved on the unit sphere. When the system became steady, particles were treated as vertices to build a spherical mesh, which was then relaxed to slightly adjust vertices to obtain optimal sampling-positions. We used 47 cases of (left and right) lungs and 50 cases of livers, (left and right) kidneys, and spleens for evaluations. Experiments showed that the proposed method was able to resolve the problem of the original MDL method, and the proposed method performed better in the generalization and specificity tests. PMID:23861721

  7. The perfect boring situation-Addressing the experience of monotony during crewed deep space missions through habitability design

    NASA Astrophysics Data System (ADS)

    Peldszus, Regina; Dalke, Hilary; Pretlove, Stephen; Welch, Chris

    2014-01-01

    In contemporary orbital missions, workloads are so high and varied that crew may rarely experience stretches of monotony. However, in historical long duration missions, occurrences of monotony were, indeed, reported anecdotally by crew. Of the effective countermeasures that appear to be at hand, many rely on visual or logistical proximity to the Earth, and are not feasible in the remote context of an extended deep space mission scenario. There, particularly in- and outbound cruising stages would be characterised by longer, comparably uneventful periods of low workload, coupled with confinement and unchanging vehicle surroundings. While the challenge of monotony has been pointed out as an exploration-related research area, it has received less explicit attention from a habitation design perspective than other human behaviour and performance issues. The paper addresses this gap through a literature review of the theory and application of design-based mitigation strategies. It outlines models of emergence of monotony, situates the phenomenon in a remote mission context as a problem of sensory, social and spatio-temporal isolation, and discusses proposed countermeasures related to habitability. The scope of the literature is extended to primary sources in the form of a qualitative review of six onboard diaries from orbital and simulator missions, highlighting a range of habitat-related design themes. These are translated into the autonomous deep space setting with the overall rationale of integrating affordances into onboard habitation systems and placing emphasis on reinforcing positive situational characteristics.

  8. A perfect launch

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Billows of smoke and steam spread across Launch Pad 39A as Space Shuttle Discovery lifts off on mission STS-92 to the International Space Station. The perfect on-time liftoff occurred at 7:17 p.m. EDT, sending a crew of seven on the 100th launch in the history of the Shuttle program. Discovery carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.

  9. Spherical harmonic analysis of the PSCz galaxy catalogue: redshift distortions and the real-space power spectrum

    NASA Astrophysics Data System (ADS)

    Tadros, H.; Ballinger, W. E.; Taylor, A. N.; Heavens, A. F.; Efstathiou, G.; Saunders, W.; Frenk, C. S.; Keeble, O.; McMahon, R.; Maddox, S. J.; Oliver, S.; Rowan-Robinson, M.; Sutherland, W. J.; White, S. D. M.

    1999-05-01

    We apply the formalism of spherical harmonic decomposition to the galaxy density field of the IRAS PSCz redshift survey. The PSCz redshift survey has almost all-sky coverage and includes IRAS galaxies to a flux limit of 0.6 Jy. Using maximum likelihood methods to examine (to first order) the distortion of the galaxy pattern resulting from redshift coordinates, we have measured the parameter beta=Omega^{0.6}/b. We also simultaneously measure either (a) the undistorted amplitude of perturbations in the galaxy distribution when a parametrized power spectrum is assumed, or (b) the shape and amplitude of the real-space power spectrum if the band-power in a set of passbands is measured in a step-wise fashion. These methods are extensively tested on a series of CDM, Lambda CDM and MDM simulations and are found to be unbiased. We obtain consistent results for the subset of the PSCz catalogue with flux above 0.75 Jy, but inclusion of galaxies to the formal flux limit of the catalogue gives variations which are larger than our internal errors. For the 0.75-Jy catalogue we find, in the case of a parametrized power spectrum, beta=0.58+/-0.26 and the amplitude of the real-space power measured at wavenumber k=0.1h Mpc^-1 is Delta_0.1=0.42+/-0.03. Freeing the shape of the power spectrum we find that beta=0.47+/-0.16 (conditional error) and Delta_0.1=0.47+/-0.03. The shape of the real-space power spectrum is consistent with a Gamma=0.2 CDM-like model, but does not strongly rule out a number of other models. Finally by combining our estimate of the amplitude of galaxy clustering and the distortion parameter we find the amplitude of mass fluctuations on a scale k=0.1h Mpc^-1 is Delta_rho=0.24Omega_0^-0.6, with an uncertainty of 50 per cent.

  10. Magnetic fields of spherical compact stars in a braneworld

    SciTech Connect

    Ahmedov, B. J.; Fattoyev, F. J.

    2008-08-15

    We study the stellar magnetic field configuration in dependence on brane tension and present solutions of Maxwell equations in the external background space-time of a magnetized spherical star in a Randall-Sundrum II type braneworld. The star is modeled as a sphere consisting of perfect highly magnetized fluid with infinite conductivity and a frozen-in magnetic field. With respect to solutions for magnetic fields found in the Schwarzschild space-time, brane tension introduces enhancing corrections to the exterior magnetic field which could be relevant for the magnetic fields of magnetized compact objects as pulsars and magnetars and may provide observational evidence for the brane tension.

  11. Just Perfect, Part 2

    ERIC Educational Resources Information Center

    Scott, Paul

    2007-01-01

    In "Just Perfect: Part 1," the author defined a perfect number N to be one for which the sum of the divisors d (1 less than or equal to d less than N) is N. He gave the first few perfect numbers, starting with those known by the early Greeks. In this article, the author provides an extended list of perfect numbers, with some comments about their…

  12. Spherically Actuated Motor

    NASA Technical Reports Server (NTRS)

    Peeples, Steven

    2015-01-01

    A three degree of freedom (DOF) spherical actuator is proposed that will replace functions requiring three single DOF actuators in robotic manipulators providing space and weight savings while reducing the overall failure rate. Exploration satellites, Space Station payload manipulators, and rovers requiring pan, tilt, and rotate movements need an actuator for each function. Not only does each actuator introduce additional failure modes and require bulky mechanical gimbals, each contains many moving parts, decreasing mean time to failure. A conventional robotic manipulator is shown in figure 1. Spherical motors perform all three actuation functions, i.e., three DOF, with only one moving part. Given a standard three actuator system whose actuators have a given failure rate compared to a spherical motor with an equal failure rate, the three actuator system is three times as likely to fail over the latter. The Jet Propulsion Laboratory reliability studies of NASA robotic spacecraft have shown that mechanical hardware/mechanism failures are more frequent and more likely to significantly affect mission success than are electronic failures. Unfortunately, previously designed spherical motors have been unable to provide the performance needed by space missions. This inadequacy is also why they are unavailable commercially. An improved patentable spherically actuated motor (SAM) is proposed to provide the performance and versatility required by NASA missions.

  13. Scattering T-matrix theory in wave-vector space for surface-enhanced Raman scattering in clusters of nanoscale spherical metal particles

    NASA Astrophysics Data System (ADS)

    Arya, Karamjeet

    2006-11-01

    Very large enhancements up to 14 orders of magnitude in the Raman cross section from a molecule adsorbed on a single cluster of a few nanoscale metal particles has been reported recently. The enhancement is believed mainly due to the enhanced electric field because of the excitation of the localized surface plasmon modes. We have developed a Green’s function theory using scattering t matrix approach in the wave-vector space to solve the Maxwell equations for the enhanced field near a spherical metal particle cluster. The advantage of working in the wave-vector space is that one does not need to use complicated translational addition theorem required in the real space as used in earlier calculations. Therefore our theory can be easily extended to any shape or size of the cluster. We consider clusters of two, three, and four spherical particles forming a linear chain, triangle, and square and calculate their localized surface modes. These modes have much more localized field near the cluster compared to those of single metal sphere and are redshifted. We find the enhancement in the Raman cross section can reach up to 10 orders of magnitude due to the resonant excitation of these modes for silver particle clusters and is in a broad frequency range. We also find new results that chainlike clusters of three or more particles have very sharp resonant features that give a dramatic increase in the enhancement near the resonance. The results for gold particle clusters are also presented.

  14. Design of compact high-resolution far-ultraviolet spectrographs equipped with a spherical grating having variable spacing and curved grooves.

    NASA Astrophysics Data System (ADS)

    Namioka, T.; Koike, M.

    Spherical ruled gratings with variable spacing and curved grooves were designed for a FUSE type and an Eagle type spectrograph using a merit function which closely represents the rms spread of the ray-traced spots. The performance of the designed gratings in the spectrographs was evaluated by means of spot diagrams and line profiles. The results show resolving power of ≍50,000 for the FUSE type and ≍80,000 for the Eagle type, over a wavelength range of 91-103 nm. However, astigmatism is not sufficiently corrected for the purpose.

  15. Micro-CT analysis and mechanical properties of Ti spherical and polyhedral void composites made with saccharose as a space holder material

    SciTech Connect

    Jakubowicz, J.; Adamek, G.; Pałka, K.; Andrzejewski, D.

    2015-02-15

    The paper describes the formation, morphology and mechanical properties of Ti void composites. The Ti void composites were made using 100 and 325 mesh Ti powder for solid scaffold formation. The spherical and polyhedral voids (pores) were formed using saccharose particles (table sugar) of different shapes. The Ti void composite morphology was investigated by microcomputed tomography and scanning electron microscopy. The Ti void composites of designed porosity of 50–70% were made. Compression test was applied for mechanical properties estimation. It has been found, that Ti void composites made from 100 mesh Ti and those having spherical pores have a higher strength and elastic modulus, i.e. for the designed porosity of 50% for 100 and 325 mesh Ti void composites, a compressive strength was 32.32 and 20.13 MPa, respectively. It has been shown that this is related to better sintering of the 100 mesh Ti powders compared with the 325 mesh Ti powders. A correlation between microcomputed tomography data and mechanical properties has also been shown. The Ti void composites, made with the use of saccharose as a space holder, described in this work should be a promising material for biomedical applications, where interconnected pores and good mechanical properties are required. - Highlights: • Ti scaffolds of the porosity of 50–70% were made. • Saccharose particles as space holder were applied. • The voids in the scaffolds were designed with spherical and polyhedral shape. • The scaffold structure was investigated by SEM and micro-CT. • Micro-CT data and mechanical properties of the Ti scaffold have been correlated.

  16. Never Perfect Enough

    ERIC Educational Resources Information Center

    Landphair, Juliette

    2007-01-01

    What exactly is perfect? Students describe perfection as a combination of characteristics valued by their peer culture: intelligence, thin and fit physical appearance, social poise. As students chug through their daily lives--morning classes, organization meetings, club sports practice or the gym, dinner, another class, more meetings, library,…

  17. Never Perfect Enough

    ERIC Educational Resources Information Center

    Landphair, Juliette

    2007-01-01

    What exactly is perfect? Students describe perfection as a combination of characteristics valued by their peer culture: intelligence, thin and fit physical appearance, social poise. As students chug through their daily lives--morning classes, organization meetings, club sports practice or the gym, dinner, another class, more meetings, library,…

  18. A perfect launch on a perfect Florida day!

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A perfect launch on a perfect Florida day! Framed by two immense billows of steam, Space Shuttle Endeavour breaks its Earthly tethers to soar into a clear blue sky. Liftoff of mission STS-99 occurred at 12:43:40 p.m. EST. Known as the Shuttle Radar Topography Mission (SRTM), STS-99 will chart a new course to produce unrivaled 3-D images of the Earth's surface. The result of the SRTM could be close to 1 trillion measurements of the Earth's topography. The mission is expected to last 11days, with Endeavour landing at KSC Tuesday, Feb. 22, at 4:36 p.m. EST. This is the 97th Shuttle flight and 14th for Shuttle Endeavour.

  19. A perfect launch on a perfect Florida day!

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A perfect launch on a perfect Florida day! Space Shuttle Endeavour, with its crew of five, scatters billows of steam and smoke as it lifts off at 12:43:40 p.m. EST on mission STS-99. Employees and visitors watch intently from across the turn basin. Known as the Shuttle Radar Topography Mission (SRTM), STS-99 will chart a new course to produce unrivaled 3-D images of the Earth's surface. The result of the SRTM could be close to 1 trillion measurements of the Earth's topography. The mission is expected to last 11days, with Endeavour landing at KSC Tuesday, Feb. 22, at 4:36 p.m. EST. This is the 97th Shuttle flight and 14th for Shuttle Endeavour.

  20. Porous titanium manufactured by a novel powder tapping method using spherical salt bead space holders: Characterisation and mechanical properties.

    PubMed

    Jia, Jiangang; Siddiq, Abdur R; Kennedy, Andrew R

    2015-08-01

    Porous Ti with open porosity in the range of 70-80% has been made using Ti powder and a particulate leaching technique using porous, spherical, NaCl beads. By incorporating the Ti powder into a pre-existing network of salt beads, by tapping followed by compaction, salt dissolution and "sintering", porous structures with uniform density, pore and strut sizes and a predictable level of connectivity have been produced, showing a significant improvement on the structures made by conventional powder mixing processes. Parts made using beads with sizes in the range of 0.5-1.0 mm show excellent promise as porous metals for medical devices, showing structures and porosities similar to those of commercial porous metals used in this sector, with inter-pore connections that are similar to trabecular bone. The elastic modulus (0.86 GPa) is lower than those for commercial porous metals and more closely matches that of trabecular bone and good compressive yield strength is retained (21 MPa). The ability to further tailor the structure, in terms of the density and the size of the pores and interconnections has also been demonstrated by immersion of the porous components in acid.

  1. Visible light broadband perfect absorbers

    SciTech Connect

    Jia, X. L.; Meng, Q. X.; Yuan, C. X.; Zhou, Z. X.; Wang, X. O.

    2016-03-15

    The visible light broadband perfect absorbers based on the silver (Ag) nano elliptical disks and holes array are studied using finite difference time domain simulations. The semiconducting indium silicon dioxide thin film is introduced as the space layer in this sandwiched structure. Utilizing the asymmetrical geometry of the structures, polarization sensitivity for transverse electric wave (TE)/transverse magnetic wave (TM) and left circular polarization wave (LCP)/right circular polarization wave (RCP) of the broadband absorption are gained. The absorbers with Ag nano disks and holes array show several peaks absorbance of 100% by numerical simulation. These simple and flexible perfect absorbers are particularly desirable for various potential applications including the solar energy absorber.

  2. Hamiltonian Dynamics in Extended Phase Space for Gravity and its Consistency with Lagrangian Formalism: a Generalized Spherically Symmetric Model as AN Example

    NASA Astrophysics Data System (ADS)

    Shestakova, Tatyana P.

    2015-01-01

    Among theoretical issues in General Relativity the problem of constructing its Hamiltonian formulation is still of interest. The most of attempts to quantize Gravity are based upon Dirac generalization of Hamiltonian dynamics for system with constraints. At the same time there exists another way to formulate Hamiltonian dynamics for constrained systems guided by the idea of extended phase space. We have already considered some features of this approach in the previous MG12 Meeting by the example of a simple isotropic model. Now we apply the approach to a generalized spherically symmetric model which imitates the structure of General Relativity much better. In particular, making use of a global BRST symmetry and the Noether theorem, we construct the BRST charge that generates correct gauge transformations for all gravitational degrees of freedom.

  3. Perfect and improving

    NASA Astrophysics Data System (ADS)

    Kerr, Robert

    2008-09-01

    As a child I always used to wonder how someone could be described as a "perfect stranger". Not only did I not know any strangers (by definition), I also didn't really see how anyone could be called perfect - that seemed a bridge too far. Nowadays, however, in my early dotage/mid-life crisis/eternally youthful existence (depending on whether you are talking to my friends, family or me) I begin to see that perhaps at last I have achieved a level of perfection not anticipated in my youth. You see, I have almost completely transmogrified myself from a real physics teacher into a pretend sociologist. I am now, and intend to continue to be for some time, a perfect fraud.

  4. Just Perfect: Part 1

    ERIC Educational Resources Information Center

    Scott, Paul

    2007-01-01

    This article is about a very small subset of the positive integers. The positive integer N is said to be "perfect" if it is the sum of all its divisors, including 1, but less that N itself. For example, N = 6 is perfect, because the (relevant) divisors are 1, 2 and 3, and 6 = 1 + 2 + 3. On the other hand, N = 12 has divisors 1, 2, 3, 4 and 6, but…

  5. Electromagnetic Detection of a Perfect Invisibility Cloak

    SciTech Connect

    Zhang Baile; Wu, Bae-Ian

    2009-12-11

    A perfect invisibility cloak is commonly believed to be undetectable from electromagnetic (EM) detection because it is equivalent to a curved but empty EM space created from coordinate transformation. Based on the intrinsic asymmetry of coordinate transformation applied to motions of photons and charges, we propose a method to detect this curved EM space by shooting a fast-moving charged particle through it. A broadband radiation generated in this process makes a cloak visible. Our method is the only known EM mechanism so far to detect an ideal perfect cloak (curved EM space) within its working band.

  6. TM surface wave diffraction by a truncated dielectric slab recessed in a perfectly conducting surface. [considering flush mounted space shuttle antenna

    NASA Technical Reports Server (NTRS)

    Pathak, P. H.; Kouyoumjian, R. G.

    1974-01-01

    The diffraction of a TM sub o surface wave by a terminated dielectric slab which is flush mounted in a perfectly conducting surface is studied. The incident surface wave gives rise to waves reflected and diffracted by the termination; these reflected and diffracted fields may be expressed in terms of the geometrical theory of diffraction by introducing surface wave reflection and diffraction coefficients which are associated with the termination. In this investigation, the surface wave reflection and diffraction coefficients have been deduced from a formally exact solution to this canonical problem. The solution is obtained by a combination of the generalized scattering matrix technique and function theoretic methods.

  7. Invariant perfect tensors

    NASA Astrophysics Data System (ADS)

    Li, Youning; Han, Muxin; Grassl, Markus; Zeng, Bei

    2017-06-01

    Invariant tensors are states in the SU(2) tensor product representation that are invariant under SU(2) action. They play an important role in the study of loop quantum gravity. On the other hand, perfect tensors are highly entangled many-body quantum states with local density matrices maximally mixed. Recently, the notion of perfect tensors has attracted a lot of attention in the fields of quantum information theory, condensed matter theory, and quantum gravity. In this work, we introduce the concept of an invariant perfect tensor (IPT), which is an n-valent tensor that is both invariant and perfect. We discuss the existence and construction of IPTs. For bivalent tensors, the IPT is the unique singlet state for each local dimension. The trivalent IPT also exists and is uniquely given by Wigner’s 3j symbol. However, we show that, surprisingly, 4-valent IPTs do not exist for any identical local dimension d. On the contrary, when the dimension is large, almost all invariant tensors are asymptotically perfect, which is a consequence of the phenomenon of the concentration of measure for multipartite quantum states.

  8. Unidirectional perfect absorber

    NASA Astrophysics Data System (ADS)

    Jin, L.; Wang, P.; Song, Z.

    2016-09-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices.

  9. Unidirectional perfect absorber

    PubMed Central

    Jin, L.; Wang, P.; Song, Z.

    2016-01-01

    This study proposes a unidirectional perfect absorber (UPA), which we realized with a two-arm Aharonov-Bohm interferometer, that consists of a dissipative resonator side-coupled to a uniform resonator array. The UPA has reflection-less full absorption on one direction, and reflectionless full transmission on the other, with an appropriate magnetic flux and coupling, detuning, and loss of the side-coupled resonator. The magnetic flux controls the transmission, the left transmission is larger for magnetic flux less than one-half flux quantum; and the right transmission is larger for magnetic flux between one-half and one flux quantum. Besides, a perfect absorber (PA) can be realized based on the UPA, in which light waves from both sides, with arbitrary superposition of the ampli- tude and phase, are perfectly absorbed. The UPA is expected to be useful in the design of novel optical devices. PMID:27615125

  10. Electrodynamics of Perfect Conductors

    NASA Astrophysics Data System (ADS)

    Fiolhais, Miguel C. N.; Essén, Hanno

    2013-05-01

    The most general electrodynamic equations of a perfect conducting state are obtained using a variational principle in a classical framework, following an approach by Pierre-Gilles de Gennes. London equations are derived as the time-independent case of these equations, corresponding to the magnetostatic minimal energy state of the perfect conducting system. For further confirmation, the same equations are also derived in the classical limit of the Coleman-Weinberg model, the most successful quantum macroscopic theory of superconductivity. The magnetic field expulsion is, therefore, a direct consequence of zero resistivity and not an exclusive property of superconductors.

  11. Coordinate-space solution of the Skyrme-Hartree-Fock- Bogolyubov equations within spherical symmetry. The program HFBRAD (v1.00)

    NASA Astrophysics Data System (ADS)

    Bennaceur, K.; Dobaczewski, J.

    2005-06-01

    We describe the first version (v1.00) of the code HFBRAD which solves the Skyrme-Hartree-Fock or Skyrme-Hartree-Fock-Bogolyubov equations in the coordinate representation with spherical symmetry. A realistic representation of the quasiparticle wave functions on the space lattice allows calculations to be performed up to the particle drip lines. Zero-range density-dependent interactions are used in the pairing channel. The pairing energy is calculated by either using a cut-off energy in the quasiparticle spectrum or the regularization scheme proposed by A. Bulgac and Y. Yu. Program summaryTitle of the program:HFBRAD (v1.00) Catalogue indentifier:ADVM Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVM Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: none Computers on which the program has been tested: Pentium-III, Pentium-IV Operating systems: LINUX, Windows Programming language used:FORTRAN-95 Memory required to execute with typical data: 30 MBytes No. of bits in a word: The code is written with a type real and uses the intrinsic function selected_real_kind at the beginning of the code to ask for at least 12 significant digits. This can be easily modified by asking for more significant digits if the architecture of the computer can handle it. No. of processors used:1 Has the code been vectorized?:No No. of bytes in distributed program, including test data, etc.: 40 308 No. of lines in distributed program, including test data, etc.: 5370 Distribution format:tar.gz Nature of physical problem: For a self-consistent description of nuclear pair correlations, both the particle-hole (field) and particle-particle (pairing) channels of the nuclear mean field must be treated within a common approach, which is the Hartree-Fock-Bogolyubov theory. By expressing these fields in spatial coordinates one can obtain the best possible solutions of the problem; however, without assuming specific symmetries the

  12. Near-perfect diffraction grating rhomb

    DOEpatents

    Wantuck, Paul J.

    1990-01-01

    A near-perfect grating rhomb enables an output beam to be diffracted to an angle offset from the input beam. The correcting grating is tipped relative to the dispersing grating to provide the offset angle. The correcting grating is further provided with a groove spacing which differs from the dispersing grating groove space by an amount effective to substantially remove angular dispersion in the output beam. A near-perfect grating rhomb has the capability for selective placement in a FEL to suppress sideband instabilities arising from the FEL.

  13. SPHERICAL DIE

    DOEpatents

    Livingston, J.P.

    1959-01-27

    A die is presented for pressing powdered materials into a hemispherical shape of uniforin density and wall thickness comprising a fcmale and male die element held in a stationary spaced relation with the space being equivalent to the wall thickness and defining the hemispherical shape, a pressing ring linearly moveable along the male die element, an inlet to fill the space with powdered materials, a guiding system for moving the pressing ring along the male die element so as to press the powdered material and a heating system for heating the male element so that the powdered material is heated while being pressed.

  14. A More Perfect Union

    ERIC Educational Resources Information Center

    DiConsiglio, John

    2012-01-01

    Alumni relations and stewardship officers have the makings of a strong partnership. Alumni relations and stewardship can be a natural fit--a perfect match even--according to Mary Jo Chiara of St. Joseph's College (SJC) in New York. Both strive to cultivate long-term relationships with constituents and build increasing levels of engagement and…

  15. The Perfect Text.

    ERIC Educational Resources Information Center

    Russo, Ruth

    1998-01-01

    A chemistry teacher describes the elements of the ideal chemistry textbook. The perfect text is focused and helps students draw a coherent whole out of the myriad fragments of information and interpretation. The text would show chemistry as the central science necessary for understanding other sciences and would also root chemistry firmly in the…

  16. California's Perfect Storm

    ERIC Educational Resources Information Center

    Bacon, David

    2010-01-01

    The United States today faces an economic crisis worse than any since the Great Depression of the 1930s. Nowhere is it sharper than in the nation's schools. Last year, California saw a perfect storm of protest in virtually every part of its education system. K-12 teachers built coalitions with parents and students to fight for their jobs and their…

  17. California's Perfect Storm

    ERIC Educational Resources Information Center

    Bacon, David

    2010-01-01

    The United States today faces an economic crisis worse than any since the Great Depression of the 1930s. Nowhere is it sharper than in the nation's schools. Last year, California saw a perfect storm of protest in virtually every part of its education system. K-12 teachers built coalitions with parents and students to fight for their jobs and their…

  18. The Three Perfections

    ERIC Educational Resources Information Center

    Hinshaw, Craig

    2005-01-01

    For thousands of years, the three perfections--painting, poetry, and calligraphy--have been considered the mark of an enlightened person throughout Asian cultures. Fifth-grade students learned about these three hallmarks by studying three works from the Detroit Institute of Art's Asian collection: a nineteenth-century Japanese hand scroll, a…

  19. PERFECTIVE PARTICIPIALS IN HINDI.

    ERIC Educational Resources Information Center

    THIS PAPER DISCUSSES THE HINDI LANGUAGE SYNTAX OF PERFECTIVE PARTICIPIAL FORMS AS ADJECTIVES AND AS PARTICIPLES OF SEVERAL VARIETIES. THE FIRST PART OF THE REPORT DISTINGUISHES AND DESCRIBES EIGHT KINDS OF PARTICIPIAL USAGE AND SUGGESTS MORE GENERAL RULES FOR ANALYZING THESE USES. THE SECOND PART OFFERS A GENERATIVE DESCRIPTION OF THE SAME DATA.…

  20. The Perfect Politician

    ERIC Educational Resources Information Center

    Berry, John N., III

    2010-01-01

    The perfect politician, the ideal political ally to a library, is often but not always an elected official. He or she is always an effective champion of "reasonable financial support," i.e., "the amount...which a thoroughly competent librarian can spend wisely." That is what J.T. Wyer, director of the New York State Library, said in his "What the…

  1. In a Perfect World

    ERIC Educational Resources Information Center

    Murray, Jeannette

    2010-01-01

    In a perfect world, all children should live at home with their family, play with the kids in their neighborhood, walk or ride the school bus to a community-based school--after affectionately kissing or hugging their parents goodbye. They should receive adequate classroom services and return home at 3 p.m. or thereabouts. They may even…

  2. The Three Perfections

    ERIC Educational Resources Information Center

    Hinshaw, Craig

    2005-01-01

    For thousands of years, the three perfections--painting, poetry, and calligraphy--have been considered the mark of an enlightened person throughout Asian cultures. Fifth-grade students learned about these three hallmarks by studying three works from the Detroit Institute of Art's Asian collection: a nineteenth-century Japanese hand scroll, a…

  3. In a Perfect World

    ERIC Educational Resources Information Center

    Murray, Jeannette

    2010-01-01

    In a perfect world, all children should live at home with their family, play with the kids in their neighborhood, walk or ride the school bus to a community-based school--after affectionately kissing or hugging their parents goodbye. They should receive adequate classroom services and return home at 3 p.m. or thereabouts. They may even…

  4. The Perfect Politician

    ERIC Educational Resources Information Center

    Berry, John N., III

    2010-01-01

    The perfect politician, the ideal political ally to a library, is often but not always an elected official. He or she is always an effective champion of "reasonable financial support," i.e., "the amount...which a thoroughly competent librarian can spend wisely." That is what J.T. Wyer, director of the New York State Library, said in his "What the…

  5. Improved perfect-fluid energy-momentum tensor with spin in Einstein-Cartan space-time. [applicable to problems in cosmology

    NASA Technical Reports Server (NTRS)

    Ray, J. R.; Smalley, L. L.

    1982-01-01

    The description of the spin given here is classical in that it is intrinsic but not quantized. The approach in this matter is similar to, for example, the work of Bailey and Israel (1973, 1975, 1979), where the fluid particles, which have intrinsic spin, may be galaxies or clusters of galaxies. The elementary particles of these objects and the 'ferromagnetic alignment' of their quantum spins are not resorted to in order to describe a fluid with spin. Physically this means that the equation of motion for the spin tensor is a modified Fermi-Walker transport equation (Misner et al., 1973), arising as a direct result of the inclusion of spin as an intrinsic variable in the thermodynamic description of the internal energy. The variables in this description are classical variables throughout and are not microscopic fields. An improved perfect-fluid energy-momentum tensor that includes spin and torsion is presented. Use is made of a Lagrangian variational principle based on the tetrad formalism of Halbwach (1960) and the method od constraints of Ray (1972).

  6. Spherical colloidal photonic crystals.

    PubMed

    Zhao, Yuanjin; Shang, Luoran; Cheng, Yao; Gu, Zhongze

    2014-12-16

    CONSPECTUS: Colloidal photonic crystals (PhCs), periodically arranged monodisperse nanoparticles, have emerged as one of the most promising materials for light manipulation because of their photonic band gaps (PBGs), which affect photons in a manner similar to the effect of semiconductor energy band gaps on electrons. The PBGs arise due to the periodic modulation of the refractive index between the building nanoparticles and the surrounding medium in space with subwavelength period. This leads to light with certain wavelengths or frequencies located in the PBG being prohibited from propagating. Because of this special property, the fabrication and application of colloidal PhCs have attracted increasing interest from researchers. The most simple and economical method for fabrication of colloidal PhCs is the bottom-up approach of nanoparticle self-assembly. Common colloidal PhCs from this approach in nature are gem opals, which are made from the ordered assembly and deposition of spherical silica nanoparticles after years of siliceous sedimentation and compression. Besides naturally occurring opals, a variety of manmade colloidal PhCs with thin film or bulk morphology have also been developed. In principle, because of the effect of Bragg diffraction, these PhC materials show different structural colors when observed from different angles, resulting in brilliant colors and important applications. However, this angle dependence is disadvantageous for the construction of some optical materials and devices in which wide viewing angles are desired. Recently, a series of colloidal PhC materials with spherical macroscopic morphology have been created. Because of their spherical symmetry, the PBGs of spherical colloidal PhCs are independent of rotation under illumination of the surface at a fixed incident angle of the light, broadening the perspective of their applications. Based on droplet templates containing colloidal nanoparticles, these spherical colloidal PhCs can be

  7. Buckling of spherical shells revisited

    NASA Astrophysics Data System (ADS)

    Hutchinson, John W.

    2016-11-01

    A study is presented of the post-buckling behaviour and imperfection sensitivity of complete spherical shells subject to uniform external pressure. The study builds on and extends the major contribution to spherical shell buckling by Koiter in the 1960s. Numerical results are presented for the axisymmetric large deflection behaviour of perfect spheres followed by an extensive analysis of the role axisymmetric imperfections play in reducing the buckling pressure. Several types of middle surface imperfections are considered including dimple-shaped undulations and sinusoidal-shaped equatorial undulations. Buckling occurs either as the attainment of a maximum pressure in the axisymmetric state or as a non-axisymmetric bifurcation from the axisymmetric state. Several new findings emerge: the abrupt mode localization that occurs immediately after the onset of buckling, the existence of an apparent lower limit to the buckling pressure for realistically large imperfections, and comparable reductions of the buckling pressure for dimple and sinusoidal equatorial imperfections.

  8. RHIC The Perfect Liquid

    ScienceCinema

    BNL

    2016-07-12

    Evidence to date suggests that gold-gold collisions the Relativistic Heavy Ion Collider at Brookhaven are indeed creating a new state of hot, dense matter, but one quite different and even more remarkable than had been predicted. Instead of behaving like a gas of free quarks and gluons, as was expected, the matter created in RHIC's heavy ion collisions appears to be more like a "perfect" liquid.

  9. RHIC The Perfect Liquid

    SciTech Connect

    BNL

    2008-08-12

    Evidence to date suggests that gold-gold collisions the Relativistic Heavy Ion Collider at Brookhaven are indeed creating a new state of hot, dense matter, but one quite different and even more remarkable than had been predicted. Instead of behaving like a gas of free quarks and gluons, as was expected, the matter created in RHIC's heavy ion collisions appears to be more like a "perfect" liquid.

  10. Spherical 3D isotropic wavelets

    NASA Astrophysics Data System (ADS)

    Lanusse, F.; Rassat, A.; Starck, J.-L.

    2012-04-01

    Context. Future cosmological surveys will provide 3D large scale structure maps with large sky coverage, for which a 3D spherical Fourier-Bessel (SFB) analysis in spherical coordinates is natural. Wavelets are particularly well-suited to the analysis and denoising of cosmological data, but a spherical 3D isotropic wavelet transform does not currently exist to analyse spherical 3D data. Aims: The aim of this paper is to present a new formalism for a spherical 3D isotropic wavelet, i.e. one based on the SFB decomposition of a 3D field and accompany the formalism with a public code to perform wavelet transforms. Methods: We describe a new 3D isotropic spherical wavelet decomposition based on the undecimated wavelet transform (UWT) described in Starck et al. (2006). We also present a new fast discrete spherical Fourier-Bessel transform (DSFBT) based on both a discrete Bessel transform and the HEALPIX angular pixelisation scheme. We test the 3D wavelet transform and as a toy-application, apply a denoising algorithm in wavelet space to the Virgo large box cosmological simulations and find we can successfully remove noise without much loss to the large scale structure. Results: We have described a new spherical 3D isotropic wavelet transform, ideally suited to analyse and denoise future 3D spherical cosmological surveys, which uses a novel DSFBT. We illustrate its potential use for denoising using a toy model. All the algorithms presented in this paper are available for download as a public code called MRS3D at http://jstarck.free.fr/mrs3d.html

  11. Five dimensional spherically symmetric cosmological model in Brans-Dicke theory of gravitation

    NASA Astrophysics Data System (ADS)

    Rao, V. U. M.; Jaysudha, V.

    2015-08-01

    In this paper, we consider the spherically symmetric space-time in five dimensions in Brans-Dicke (Phys. Rev. 124:925, 1961) theory of gravitation in the presence of perfect fluid distribution. A determinate solution of the highly non-linear field equations is presented using (i) relation between metric potentials and (ii) an equation of state which represents disordered radiation in five dimensional universe. The solution obtained describes five dimensional radiating model in Brans-Dicke theory. Some physical and kinematical properties of the model are also discussed.

  12. Comparison between Measured and Simulated Radiation Doses in the Matoroshka-R Spherical phantom Experiment#1 and Area Monitoring aboard International Space Station using PADLES from May - Sep. 2012

    NASA Astrophysics Data System (ADS)

    Nagamatsu, Aiko; Tolochek, Raisa; Shurshakov, Vyacheslav; Nikolaev, Igor; Tawara, Hiroko; Kitajo, Keiichi; Shimada, Ken

    The measurement of radiation environmental parameters in space is essential to support radiation risk assessments for astronauts and establish a benchmark for space radiation models for present and future human space activities. Since Japanese Experiment Module ‘KIBO’ was attached to the International Space Station (ISS) in 2008, we have been performing continuous space radiation dosimetery using a PADLES (Passive Dosimeter for Life-Science Experiments in Space) consisting of CR-39 PNTDs (Plastic Nuclear track detectors) and TLD-MSOs (Mg2SiO4:Tb) for various space experiments onboard the ‘KIBO’ part of the ISS. The MATROSHKA-R experiments aims to verify of dose distributions in a human body during space flight. The phantom consists of tissue equivalent material covered by a poncho jacket with 32 pockets on the surface. 20 container rods with dosimeters can be struck into the spherical phantom. Its diameter is 370 mm and it is 32 kg in weight. The first experiment onboard the KIBO at Forward No.2 area (JPM1F2 Rack2) was conducted over 114 days from 21 May to 12 September 2012 (the installation schedule inside the phantom) on the way to solar cycle 24th upward curve. 16 PADLES packages were deployed into 16 poncho pockets on the surface of the spherical phantom. Another 12 PADLES packages were deployed inside 4 rods (3 packages per rod in the outer, middle and inner side). Area monitoring in the KIBO was conducted in the same period (Area PADLES series #8 from 15 May to 16 September, 2012). Absorbed doses were measured at 17 area monitoring points in the KIBO and 28 locations (16 packages in poncho pockets and 12 inside 4 rods) in the phantom. The maximum value measured with the PADLES in the poncho pockets on the surface of the spherical phantom facing the outer wall was 0.43 mGy/day and the minimum value measured with the PADLES in the poncho pockets on the surface of the spherical phantom facing the KIBO interior was 0.30 mGy/day. The maximum absorbed

  13. Ultra-Perfect Sorting Scenarios

    NASA Astrophysics Data System (ADS)

    Ouangraoua, Aïda; Bergeron, Anne; Swenson, Krister M.

    Perfection has been used as a criteria to select rearrangement scenarios since 2004. However, there is a fundamental bias towards extant species in the original definition: ancestral species are not bound to perfection. Here we develop a new theory of perfection that takes an egalitarian view of species, and apply it to the complex evolution of mammal chromosome X.

  14. Near perfect optics

    SciTech Connect

    Goeke, R.; Farnsworth, A.V.; Neumann, C.C.; Sweatt, W.C.; Warren, M.E.; Weed, J.W.

    1996-06-01

    This report discusses a novel fabrication process to produce nearly perfect optics. The process utilizes vacuum deposition techniques to optimally modify polished optical substrate surfaces. The surface figure, i.e. contour of a polished optical element, is improved by differentially filling in the low spots on the surface using flux from a physical vapor deposition source through an appropriate mask. The process is expected to enable the manufacture of diffraction-limited optical systems for the UV, extreme UV, and soft X-ray spectral regions, which would have great impact on photolithography and astronomy. This same technique may also reduce the fabrication cost of visible region optics with aspheric surfaces.

  15. A proposed mechanism for the formation of spherical vivianite crystal aggregates in sediments

    USGS Publications Warehouse

    Zelibor, J.L.; Senftle, F.E.; Reinhardt, J.L.

    1988-01-01

    Vivianite [Fe3(PO4)2??8H2O] is often found in the form of nodules composed of spherical aggregates of crystals. Crystallization of vivianite in agar gels of various concentrations yield crystal aggregates (nodules) that have spherical morphology and a bimodal size distribution. The aggregates were formed under both biotic and abiotic conditions. When special redox cells fitted with electrodes were used, more perfect spherical structures were formed when the electrodes were shorted than when they were on open circuit. In nature, vivianite nodules generally are found in sediments or clays that are gelatinous, often caused by the presence of organic debris. A model consistent with experimental observations and based on the dynamics of gels is proposed to explain a possible origin of nodular vivianite. To maintain iron and phosphate concentrations in sedimentary pore spaces filled with gel-like organic debris, the electric field spanning the aerobic-anerobic zones in the upper sediments may be an important driving force in addition to diffusion. It is suggested that the combination of the gel medium in the pore spaces and the natural electric field in the upper sediments could be contributing causes to explain the spherical aggregates of vivianite crystals found in nature. ?? 1988.

  16. Perfect fluid tori orbiting Kehagias-Sfetsos naked singularities

    NASA Astrophysics Data System (ADS)

    Stuchlík, Z.; Pugliese, D.; Schee, J.; Kučáková, H.

    2015-09-01

    We construct perfect fluid tori in the field of the Kehagias-Sfetsos (K-S) naked singularities. These are spherically symmetric vacuum solutions of the modified Hořava quantum gravity, characterized by a dimensionless parameter ω M^2, combining the gravitational mass parameter M of the spacetime with the Hořava parameter ω reflecting the role of the quantum corrections. In dependence on the value of ω M^2, the K-S naked singularities demonstrate a variety of qualitatively different behavior of their circular geodesics that is fully reflected in the properties of the toroidal structures, demonstrating clear distinction to the properties of the torii in the Schwarzschild spacetimes. In all of the K-S naked singularity spacetimes the tori are located above an "antigravity" sphere where matter can stay in a stable equilibrium position, which is relevant for the stability of the orbiting fluid toroidal accretion structures. The signature of the K-S naked singularity is given by the properties of marginally stable tori orbiting with the uniform distribution of the specific angular momentum of the fluid, l= const. In the K-S naked singularity spacetimes with ω M^2 > 0.2811, doubled tori with the same l= const can exist; mass transfer between the outer torus and the inner one is possible under appropriate conditions, while only outflow to the outer space is allowed in complementary conditions. In the K-S spacetimes with ω M^2 < 0.2811, accretion from cusped perfect fluid tori is not possible due to the non-existence of unstable circular geodesics.

  17. Universal evolution of perfect lenses.

    PubMed

    Wee, W H; Pendry, J B

    2011-04-22

    This Letter is a theoretical attempt to answer two questions. First how long does it takes for perfect lensing to be observed, and second how does loss diminish the performance of a general perfect lens. The method described in this Letter is universal, in the sense that it can be applied to perfect lenses of any arbitrary geometry. We shall show that the dynamics of perfect lensing is equivalent to the dynamics of 2 coupled simple harmonic oscillators. Moreover we shall derive quantitatively, the effects of losses on a compact perfect lens.

  18. Three-point spherical mirror mount

    DOEpatents

    Cutburth, R.W.

    1984-01-23

    A three-point spherical mirror mount for use with lasers is disclosed. The improved mirror mount is adapted to provide a pivot ring having an outer surface with at least three spaced apart mating points to engage an inner spherical surface of a support housing.

  19. Three-point spherical mirror mount

    DOEpatents

    Cutburth, Ronald W.

    1990-01-01

    A three-point spherical mirror mount for use with lasers is disclosed. The improved mirror mount is adapted to provide a pivot ring having an outer surface with at least three spaced apart mating points to engage an inner spherical surface of a support housing.

  20. The Perfect Map

    NASA Astrophysics Data System (ADS)

    Suri, Veenu; Rauscher, Emily; Cowan, Nicolas B.

    2017-01-01

    Thermal phase curves and eclipses provide the best constraints on the atmospheric temperature and circulation of short-period planets. The temperature structure of a planet can be expressed as a sum of spherical harmonics. Each spherical harmonic has a corresponding harmonic light curve, which is a function of system geometry (orbital inclination, planet/star radius ratio, and orbital separation). Depending on system geometry, there may be significant degeneracies between harmonic light curves: very different maps may produce similar light curves. Here we use Principal Component Analysis (PCA) to identify and quantify these degeneracies. Starting from a set of harmonic light curves, we use PCA to calculate the set of orthonormal "eigen-light-curves". In addition, PCA determines the importance of every eigen-light-curve, telling us which components provide the most information. From these eigen-curves we can then reconstruct corresponding "eigen-maps". These eigen-light-curves and eigen-maps are the mathematically ideal basis set for inverting phase curve and eclipse data to create maps of a planet's emission. We determine how many eigen-maps can be fit to full-orbit light curves, as a function of photometric precision and system geometry.

  1. On the unconstrained expansion of a spherical plasma cloud turning collisionless: case of a cloud generated by a nanometre dust grain impact on an uncharged target in space

    NASA Astrophysics Data System (ADS)

    Pantellini, F.; Landi, S.; Zaslavsky, A.; Meyer-Vernet, N.

    2012-04-01

    Nano and micrometre sized dust particles travelling through the heliosphere at several hundreds of km s-1 have been repeatedly detected by interplanetary spacecraft. When such fast moving dust particles hit a solid target in space, an expanding plasma cloud is formed through the vaporization and ionization of the dust particles itself and part of the target material at and near the impact point. Immediately after the impact the small and dense cloud is dominated by collisions and the expansion can be described by fluid equations. However, once the cloud has reached μm dimensions, the plasma may turn collisionless and a kinetic description is required to describe the subsequent expansion. In this paper we explore the late and possibly collisionless spherically symmetric unconstrained expansion of a single ionized ion-electron plasma using N-body simulations. Given the strong uncertainties concerning the early hydrodynamic expansion, we assume that at the time of the transition to the collisionless regime the cloud density and temperature are spatially uniform. We also neglect the role of the ambient plasma. This is a reasonable assumption as long as the cloud density is substantially higher than the ambient plasma density. In the case of clouds generated by fast interplanetary dust grains hitting a solid target, some 107 electrons and ions are liberated and the in vacuum approximation is acceptable up to meter order cloud dimensions. As such a cloud can be estimated to become collisionless when its radius has reached μm order dimensions, both the collisionless approximation and the in vacuum approximation are expected to hold during a long lasting phase as the cloud grows by a factor 106. With these assumptions, we find that the transition from the collisional to the collisionless regime could occur when the electron Debye length λD within the cloud is much smaller than the cloud radius R0, i.e. Λ ≡ λD/R0 ≪ 1. This implies a quasi-neutral expansion regime

  2. Perfect and Near-Perfect Adaptation in Cell Signaling.

    PubMed

    Ferrell, James E

    2016-02-24

    Adaptation is an important basic feature of cellular regulation. Previous theoretical work has identified three types of circuits-negative feedback loops, incoherent feedforward systems, and state-dependent inactivation systems-that can achieve perfect or near-perfect adaptation. Recent work has added another strategy, termed antithetic integral feedback, to the list of motifs capable of robust perfect adaptation. Here, we discuss the properties, limitations, and biological relevance of each of these circuits.

  3. Milking the spherical cow - on aspherical dynamics in spherical coordinates

    NASA Astrophysics Data System (ADS)

    Pontzen, Andrew; Read, Justin I.; Teyssier, Romain; Governato, Fabio; Gualandris, Alessia; Roth, Nina; Devriendt, Julien

    2015-08-01

    Galaxies and the dark matter haloes that host them are not spherically symmetric, yet spherical symmetry is a helpful simplifying approximation for idealized calculations and analysis of observational data. The assumption leads to an exact conservation of angular momentum for every particle, making the dynamics unrealistic. But how much does that inaccuracy matter in practice for analyses of stellar distribution functions, collisionless relaxation, or dark matter core-creation? We provide a general answer to this question for a wide class of aspherical systems; specifically, we consider distribution functions that are `maximally stable', i.e. that do not evolve at first order when external potentials (which arise from baryons, large-scale tidal fields or infalling substructure) are applied. We show that a spherically symmetric analysis of such systems gives rise to the false conclusion that the density of particles in phase space is ergodic (a function of energy alone). Using this idea we are able to demonstrate that: (a) observational analyses that falsely assume spherical symmetry are made more accurate by imposing a strong prior preference for near-isotropic velocity dispersions in the centre of spheroids; (b) numerical simulations that use an idealized spherically symmetric setup can yield misleading results and should be avoided where possible; and (c) triaxial dark matter haloes (formed in collisionless cosmological simulations) nearly attain our maximally stable limit, but their evolution freezes out before reaching it.

  4. Holographic Spherically Symmetric Metrics

    NASA Astrophysics Data System (ADS)

    Petri, Michael

    The holographic principle (HP) conjectures, that the maximum number of degrees of freedom of any realistic physical system is proportional to the system's boundary area. The HP has its roots in the study of black holes. It has recently been applied to cosmological solutions. In this article we apply the HP to spherically symmetric static space-times. We find that any regular spherically symmetric object saturating the HP is subject to tight constraints on the (interior) metric, energy-density, temperature and entropy-density. Whenever gravity can be described by a metric theory, gravity is macroscopically scale invariant and the laws of thermodynamics hold locally and globally, the (interior) metric of a regular holographic object is uniquely determined up to a constant factor and the interior matter-state must follow well defined scaling relations. When the metric theory of gravity is general relativity, the interior matter has an overall string equation of state (EOS) and a unique total energy-density. Thus the holographic metric derived in this article can serve as simple interior 4D realization of Mathur's string fuzzball proposal. Some properties of the holographic metric and its possible experimental verification are discussed. The geodesics of the holographic metric describe an isotropically expanding (or contracting) universe with a nearly homogeneous matter-distribution within the local Hubble volume. Due to the overall string EOS the active gravitational mass-density is zero, resulting in a coasting expansion with Ht = 1, which is compatible with the recent GRB-data.

  5. Medical Practice Makes Perfect

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Cedaron Medical Inc., was founded in 1990 as a result of a NASA SBIR (Small Business Innovative Research) grant from Johnson Space Center to develop a Hand Testing and Exercise Unit for use in space. From that research came Dexter, a comprehensive workstation that creates a paperless environment for medical data management.

  6. Spherical harmonics in texture analysis

    NASA Astrophysics Data System (ADS)

    Schaeben, Helmut; van den Boogaart, K. Gerald

    2003-07-01

    The objective of this contribution is to emphasize the fundamental role of spherical harmonics in constructive approximation on the sphere in general and in texture analysis in particular. The specific purpose is to present some methods of texture analysis and pole-to-orientation probability density inversion in a unifying approach, i.e. to show that the classic harmonic method, the pole density component fit method initially introduced as a distinct alternative, and the spherical wavelet method for high-resolution texture analysis share a common mathematical basis provided by spherical harmonics. Since pole probability density functions and orientation probability density functions are probability density functions defined on the sphere Ω3⊂ R3 or hypersphere Ω4⊂ R4, respectively, they belong at least to the space of measurable and integrable functions L1( Ωd), d=3, 4, respectively. Therefore, first a basic and simplified method to derive real symmetrized spherical harmonics with the mathematical property of providing a representation of rotations or orientations, respectively, is presented. Then, standard orientation or pole probability density functions, respectively, are introduced by summation processes of harmonic series expansions of L1( Ωd) functions, thus avoiding resorting to intuition and heuristics. Eventually, it is shown how a rearrangement of the harmonics leads quite canonically to spherical wavelets, which provide a method for high-resolution texture analysis. This unified point of view clarifies how these methods, e.g. standard functions, apply to texture analysis of EBSD orientation measurements.

  7. Structured metal film as a perfect absorber.

    PubMed

    Xiong, Xiang; Jiang, Shang-Chi; Hu, Yu-Hui; Peng, Ru-Wen; Wang, Mu

    2013-08-07

    A new type of absorber, a four-tined fish-spear-like resonator (FFR), constructed by the two-photon polymerization process, is reported. An absorbance of more than 90% is experimentally realized and the resonance occurs in the space between the tines. Since a continuous layer of metallic thin film covers the structure, it is perfectly thermo- and electroconductive, which is the mostly desired feature for many applications.

  8. The failure strengths of perfect diamond crystals

    NASA Technical Reports Server (NTRS)

    Whitlock, J.; Ruoff, A. L.

    1981-01-01

    Finite elasticity analysis is extended to the 110 direction, where off axis strain symmetry is not present, and the third order elastic data are obtained for diamond. The compressive yield strengths of perfect diamond crystals loaded in the 100, 110, and 111 directions are predicted to be 2.2, 5.6, and 2.8 Mbars, respectively, while the corresponding tensile fracture strengths are 1.0, 0.5, and 0.5 Mbars. From these results and from Hertz theory it is predicted that ring fracture of spherically tipped diamonds pressed against a flat will occur at pressures of 1.8-1.9 Mbars, substantially below the yield pressure (above 3 Mbars). Modification of the tip shape leads to a predicted increase in the pressure at which fracture occurs.

  9. Electromagnetic Detection of a Perfect Carpet Cloak

    NASA Astrophysics Data System (ADS)

    Shi, Xihang; Gao, Fei; Lin, Xiao; Zhang, Baile

    2015-05-01

    It has been shown that a spherical invisibility cloak originally proposed by Pendry et al. can be electromagnetically detected by shooting a charged particle through it, whose underlying mechanism stems from the asymmetry of transformation optics applied to motions of photons and charges [PRL 103, 243901 (2009)]. However, the conceptual three-dimensional invisibility cloak that exactly follows specifications of transformation optics is formidably difficult to implement, while the simplified cylindrical cloak that has been experimentally realized is inherently visible. On the other hand, the recent carpet cloak model has acquired remarkable experimental development, including a recently demonstrated full-parameter carpet cloak without any approximation in the required constitutive parameters. In this paper, we numerically investigate the electromagnetic radiation from a charged particle passing through a perfect carpet cloak and propose an experimentally verifiable model to demonstrate symmetry breaking of transformation optics.

  10. Electromagnetic detection of a perfect carpet cloak.

    PubMed

    Shi, Xihang; Gao, Fei; Lin, Xiao; Zhang, Baile

    2015-05-22

    It has been shown that a spherical invisibility cloak originally proposed by Pendry et al. can be electromagnetically detected by shooting a charged particle through it, whose underlying mechanism stems from the asymmetry of transformation optics applied to motions of photons and charges [PRL 103, 243901 (2009)]. However, the conceptual three-dimensional invisibility cloak that exactly follows specifications of transformation optics is formidably difficult to implement, while the simplified cylindrical cloak that has been experimentally realized is inherently visible. On the other hand, the recent carpet cloak model has acquired remarkable experimental development, including a recently demonstrated full-parameter carpet cloak without any approximation in the required constitutive parameters. In this paper, we numerically investigate the electromagnetic radiation from a charged particle passing through a perfect carpet cloak and propose an experimentally verifiable model to demonstrate symmetry breaking of transformation optics.

  11. Electromagnetic Detection of a Perfect Carpet Cloak

    PubMed Central

    Shi, Xihang; Gao, Fei; Lin, Xiao; Zhang, Baile

    2015-01-01

    It has been shown that a spherical invisibility cloak originally proposed by Pendry et al. can be electromagnetically detected by shooting a charged particle through it, whose underlying mechanism stems from the asymmetry of transformation optics applied to motions of photons and charges [PRL 103, 243901 (2009)]. However, the conceptual three-dimensional invisibility cloak that exactly follows specifications of transformation optics is formidably difficult to implement, while the simplified cylindrical cloak that has been experimentally realized is inherently visible. On the other hand, the recent carpet cloak model has acquired remarkable experimental development, including a recently demonstrated full-parameter carpet cloak without any approximation in the required constitutive parameters. In this paper, we numerically investigate the electromagnetic radiation from a charged particle passing through a perfect carpet cloak and propose an experimentally verifiable model to demonstrate symmetry breaking of transformation optics. PMID:25997798

  12. An approach towards a perfect thermal diffuser

    PubMed Central

    Vemuri, Krishna P.; Bandaru, Prabhakar R.

    2016-01-01

    A method for the most efficient removal of heat, through an anisotropic composite, is proposed. It is shown that a rational placement of constituent materials, in the radial and the azimuthal directions, at a given point in the composite yields a uniform temperature distribution in spherical diffusers. Such arrangement is accompanied by a very significant reduction of the source temperature, in principle, to infinitesimally above the ambient temperature and forms the basis for the design of a perfect thermal diffuser with maximal heat dissipation. Orders of magnitude enhanced performance, compared to that obtained through the use of a diffuser constituted from a single material with isotropic thermal conductivity has been observed and the analytical principles underlying the design were validated through extensive computational simulations. PMID:27404569

  13. Spherically symmetric canonical quantum gravity

    NASA Astrophysics Data System (ADS)

    Brahma, Suddhasattwa

    2015-06-01

    Canonical quantization of spherically symmetric space-times is carried out, using real-valued densitized triads and extrinsic curvature components, with specific factor-ordering choices ensuring in an anomaly free quantum constraint algebra. Comparison with previous work [Nucl. Phys. B399, 211 (1993)] reveals that the resulting physical Hilbert space has the same form, although the basic canonical variables are different in the two approaches. As an extension, holonomy modifications from loop quantum gravity are shown to deform the Dirac space-time algebra, while going beyond "effective" calculations.

  14. General formulations of global co-seismic deformations caused by an arbitrary dislocation in a spherically symmetric earth model-applicable to deformed earth surface and space-fixed point

    NASA Astrophysics Data System (ADS)

    Sun, Wenke; Okubo, Shuhei; Fu, Guangyu; Araya, Akito

    2009-06-01

    Based on the authors' previous work, co-seismic deformations for a spherical symmetric earth model are summarized and reformulated. Unified expressions presented herein accommodate physical deformations: displacement, potential, gravity, geoid and strain changes. The corresponding Green's functions are derived by combining spheroidal and toroidal deformations. Sign errors in previous publications are corrected in these new formulas. These expressions are developed basically for a deformed earth surface because most traditional geodetic measurements are performed on the terrain surface. However, through development of space geodetic techniques, such as the satellite gravity missions, co-seismic gravity changes can be detected from space. In this case, the above dislocation theory (e.g., the co-seismic gravity change) cannot be applied directly to the observed data because the data do not include surface crustal deformation (the free air gravity change). Correspondingly, the contribution by the vertical displacement part must be removed from the traditional expressions. For this purpose, we present the corresponding expressions applicable to space observations. Some numerical technical problems are discussed. In addition, a smoothing technique is necessary to damp the high-frequency contribution so that the theory can be applied reasonably. Global co-seismic deformations caused by the 2004 Sumatra-Andaman earthquake (M9.3) are studied as an application of the new Green's function. That earthquake caused a global deformation detected by GPS, strain metres and even a satellite gravity mission. These global deformations are calculated based on the derived Green's functions and the seismic-wave derived earth model. A segment-summation scheme is used considering the slip distribution on a limited fault plane. The results are useful for interpreting observed deformations, especially those in the far field. The earthquake reveals global co-seismic deformations and effects

  15. Contractions of affine spherical varieties

    SciTech Connect

    Arzhantsev, I V

    1999-08-31

    The language of filtrations and contractions is used to describe the class of G-varieties obtainable as the total spaces of the construction of contraction applied to affine spherical varieties, which is well-known in invariant theory. These varieties are local models for arbitrary affine G-varieties of complexity 1 with a one-dimensional categorical quotient. As examples, reductive algebraic semigroups and three-dimensional SL{sub 2}-varieties are considered.

  16. Ion focusing and interaction potential for spherical and rodlike obstacles in a supersonic plasma flow: numerical simulations

    SciTech Connect

    Miloch, W. J.; Pecseli, H. L.; Trulsen, J.; Vladimirov, S. V.

    2008-09-07

    The parameter dependence of the ion focus behind perfectly conducting or alternatively perfectly insulating spherical grains for different electron to ion temperature ratios is studied. For elongated, insulating dust grains we study the potential and plasma density wakes in drifting plasma for rods or plates of different lengths and different inclination angles. These two characteristics (i.e., the rod length and the inclination angle are important for the exact charge distribution on the surface and the wake pattern. For this case we discuss also the interaction potential between two elongated grains in a flowing plasma.Our simulations are carried out in two spatial dimensions by a Particle-in-Cell code, treating ions and electrons as individual particles. These studies can be relevant for finite size dust grains suspended in a plasma sheath or larger objects in space, e.g., meteoroids.

  17. Perfect extinction in subwavelength dual metallic transmitting gratings.

    PubMed

    Estruch, Thomas; Jaeck, Julien; Pardo, Fabrice; Derelle, Sophie; Primot, Jérôme; Pelouard, Jean-Luc; Haidar, Riad

    2011-08-15

    We investigate the strong electromagnetic coupling that settles in dual metallic grating structures. This coupling is evidenced to lead to a perfect optical extinction in the transmission spectrum. The behavior of this perfect extinction that strongly depends on the longitudinal space and the lateral displacement between the two gratings can be explained by a simple model that describes the interference between a propagating mode and a couple of evanescent modes. The results show that the electromagnetic transmission of the structure can be tuned by controlling the position of this perfect transmission extinction and thus pave the way to new types of infrared tunable filters. © 2011 Optical Society of America

  18. All static spherically symmetric anisotropic solutions of Einstein's equations

    SciTech Connect

    Herrera, L.; Di Prisco, A.; Ospino, J.

    2008-01-15

    An algorithm recently presented by Lake to obtain all static spherically symmetric perfect fluid solutions is extended to the case of locally anisotropic fluids (principal stresses unequal). As expected, the new formalism requires the knowledge of two functions (instead of one) to generate all possible solutions. To illustrate the method some known cases are recovered.

  19. Beam expander telescope design utilizing fast spherical primaries.

    PubMed

    Southwell, W H

    1979-04-15

    An exact geometrical ray analysis has been used to derive the profiles for telescope secondaries that perfectly recollimate beams incident on fast concave spherical mirrors. Both Cassegrainian and Gregorian configurations are possible. The high magnification designs tend to redistribute the energy profile and may be used, for example, to make Gaussian beams more uniform.

  20. The spherical birdcage resonator

    NASA Astrophysics Data System (ADS)

    Harpen, Michael D.

    A description of the operation of a spherical resonator capable of producing a uniform magnetic induction throughout a spherical volume is presented. Simple closed-form expressions for the spectrum of resonant frequencies are derived for both the low-pass and the high-pass configuration of the resonator and are shown to compare favorably with observation in an experimental coil system. It is shown that the spherical resonator produces a uniform spherical field of view when used as a magnetic resonance imaging radiofrequency coil.

  1. Spherical bearing. [to reduce vibration effects

    NASA Technical Reports Server (NTRS)

    Myers, W. N.; Hein, L. A. (Inventor)

    1978-01-01

    A spherical bearing including an inner ball with an opening for receiving a shaft and a spherical outer surface is described. Features of the bearing include: (1) a circular outer race including a plurality of circumferentially spaced sections extending around the inner ball for snugly receiving the inner ball; and (2) a groove extending circumferentially around the race producing a thin wall portion which permits the opposed side portions to flex relative to the ball for maximizing the physical contact between the inner surface of the race and the spherical outer surface of the ball.

  2. The Perfect Science Machine

    NASA Astrophysics Data System (ADS)

    2008-05-01

    ESO celebrates 10 years since First Light of the VLT Today marks the 10th anniversary since First Light with ESO's Very Large Telescope (VLT), the most advanced optical telescope in the world. Since then, the VLT has evolved into a unique suite of four 8.2-m Unit Telescopes (UTs) equipped with no fewer than 13 state-of-the-art instruments, and four 1.8-m moveable Auxiliary Telescopes (ATs). The telescopes can work individually, and they can also be linked together in groups of two or three to form a giant 'interferometer' (VLTI), allowing astronomers to see details corresponding to those from a much larger telescope. Green Flash at Paranal ESO PR Photo 16a/08 The VLT 10th anniversary poster "The Very Large Telescope array is a flagship facility for astronomy, a perfect science machine of which Europe can be very proud," says Tim de Zeeuw, ESO's Director General. "We have built the most advanced ground-based optical observatory in the world, thanks to the combination of a long-term adequately-funded instrument and technology development plan with an approach where most of the instruments were built in collaboration with institutions in the member states, with in-kind contributions in labour compensated by guaranteed observing time." Sitting atop the 2600m high Paranal Mountain in the Chilean Atacama Desert, the VLT's design, suite of instruments, and operating principles set the standard for ground-based astronomy. It provides the European scientific community with a telescope array with collecting power significantly greater than any other facilities available at present, offering imaging and spectroscopy capabilities at visible and infrared wavelengths. Blue Flash at Paranal ESO PR Photo 16b/08 A Universe of Discoveries The first scientifically useful images, marking the official 'First Light' of the VLT, were obtained on the night of 25 to 26 May 1998, with a test camera attached to "Antu", Unit Telescope number 1. They were officially presented to the press on

  3. Localized waves with spherical harmonic symmetries

    NASA Astrophysics Data System (ADS)

    Mills, M. S.; Siviloglou, G. A.; Efremidis, N.; Graf, T.; Wright, E. M.; Moloney, J. V.; Christodoulides, D. N.

    2012-12-01

    We introduce a class of propagation invariant spatiotemporal optical wave packets with spherical harmonic symmetries in their field configurations. The evolution of these light orbitals is considered theoretically in anomalously dispersive media, and their spinning dynamics are analyzed in terms of their corresponding energy flows. Similarly, localized waves generated via spherical superposition from Archimedean and Platonic solids in k⃗-ω space are investigated in this work.

  4. Exact solution for the Casimir stress in a spherically symmetric medium

    SciTech Connect

    Leonhardt, Ulf; Simpson, William M. R.

    2011-10-15

    We calculated the stress of the quantum vacuum, the Casimir stress, in a spherically symmetric medium, Maxwell's fish eye, surrounded by a perfect mirror and derived an exact analytic solution. Our solution questions the idea that the Casimir force of a spherical mirror is repulsive--we found an attractive stress in the medium that diverges at the mirror.

  5. Solute drag on perfect and extended dislocations

    NASA Astrophysics Data System (ADS)

    Sills, R. B.; Cai, W.

    2016-04-01

    The drag force exerted on a moving dislocation by a field of mobile solutes is studied in the steady state. The drag force is numerically calculated as a function of the dislocation velocity for both perfect and extended dislocations. The sensitivity of the non-dimensionalized force-velocity curve to the various controlling parameters is assessed, and an approximate analytical force-velocity expression is given. A non-dimensional parameter S characterizing the strength of the solute-dislocation interaction, the background solute fraction ?, and the dislocation character angle ?, are found to have the strongest influence on the force-velocity curve. Within the model considered here, a perfect screw dislocation experiences no solute drag, but an extended screw dislocation experiences a non-zero drag force that is about 10 to 30% of the drag on an extended edge dislocation. The solutes can change the spacing between the Shockley partials in both stationary and moving extended dislocations, even when the stacking fault energy remains unaltered. Under certain conditions, the solutes destabilize an extended dislocation by either collapsing it into a perfect dislocation or causing the partials to separate unboundedly. It is proposed that the latter instability may lead to the formation of large faulted areas and deformation twins in low stacking fault energy materials containing solutes, consistent with experimental observations of copper and stainless steel containing hydrogen.

  6. A perfect launch viewed across Banana Creek

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Discovery seems to burst forth from a pillow of smoke as it lifts off from Launch Pad 39A on mission STS-92 to the International Space Station. The brilliant light from the solid rocket booster flames is reflected in nearby water. The perfect on-time liftoff occurred at 7:17 p.m. EDT, sending a crew of seven on the 100th launch in the history of the Shuttle program. Discovery carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.

  7. A perfect launch viewed across Banana Creek

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Billows of smoke and steam surround Space Shuttle Discovery as it lifts off from Launch Pad 39A on mission STS-92 to the International Space Station. The perfect on-time liftoff occurred at 7:17 p.m. EDT, sending a crew of seven on the 100th launch in the history of the Shuttle program. Discovery carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.

  8. A perfect launch viewed across Banana Creek

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Billows of smoke and steam surround Space Shuttle Discovery as it lifts off from Launch Pad 39A on mission STS-92 to the International Space Station. The perfect on-time liftoff occurred at 7:17 p.m. EDT, sending a crew of seven on the 100th launch in the history of the Shuttle program. Discovery carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.

  9. A perfect launch viewed across Banana Creek

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Discovery seems to burst forth from a pillow of smoke as it lifts off from Launch Pad 39A on mission STS-92 to the International Space Station. The brilliant light from the solid rocket booster flames is reflected in nearby water. The perfect on-time liftoff occurred at 7:17 p.m. EDT, sending a crew of seven on the 100th launch in the history of the Shuttle program. Discovery carries a payload that includes the Integrated Truss Structure Z-1, first of 10 trusses that will form the backbone of the Space Station, and the third Pressurized Mating Adapter that will provide a Shuttle docking port for solar array installation on the sixth Station flight and Lab installation on the seventh Station flight. Discovery's landing is expected Oct. 22 at 2:10 p.m. EDT.

  10. Spherical neutron generator

    DOEpatents

    Leung, Ka-Ngo

    2006-11-21

    A spherical neutron generator is formed with a small spherical target and a spherical shell RF-driven plasma ion source surrounding the target. A deuterium (or deuterium and tritium) ion plasma is produced by RF excitation in the plasma ion source using an RF antenna. The plasma generation region is a spherical shell between an outer chamber and an inner extraction electrode. A spherical neutron generating target is at the center of the chamber and is biased negatively with respect to the extraction electrode which contains many holes. Ions passing through the holes in the extraction electrode are focused onto the target which produces neutrons by D-D or D-T reactions.

  11. Preparation and Optical Properties of Spherical Inverse Opals by Liquid Phase Deposition Using Spherical Colloidal Crystals

    NASA Astrophysics Data System (ADS)

    Aoi, Y.; Tominaga, T.

    2013-03-01

    Titanium dioxide (TiO2) inverse opals in spherical shape were prepared by liquid phase deposition (LPD) using spherical colloidal crystals as templates. Spherical colloidal crystals were produced by ink-jet drying technique. Aqueous emulsion droplets that contain polystyrene latex particles were ejected into air and dried. Closely packed colloidal crystals with spherical shape were obtained. The obtained spherical colloidal crystals were used as templates for the LPD. The templates were dispersed in the deposition solution of the LPD, i.e. a mixed solution of ammonium hexafluorotitanate and boric acid and reacted for 4 h at 30 °C. After the LPD process, the interstitial spaces of the spherical colloidal crystals were completely filled with titanium oxide. Subsequent heat treatment resulted in removal of templates and spherical titanium dioxide inverse opals. The spherical shape of the template was retained. SEM observations indicated that the periodic ordered voids were surrounded by titanium dioxide. The optical reflectance spectra indicated that the optical properties of the spherical titanium dioxide inverse opals were due to Bragg diffractions from the ordered structure. Filling in the voids of the inverse opals with different solvents caused remarkable changes in the reflectance peak.

  12. Imperfection sensitivity of pressured buckling of biopolymer spherical shells

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Ru, C. Q.

    2016-06-01

    Imperfection sensitivity is essential for mechanical behavior of biopolymer shells [such as ultrasound contrast agents (UCAs) and spherical viruses] characterized by high geometric heterogeneity. In this work, an imperfection sensitivity analysis is conducted based on a refined shell model recently developed for spherical biopolymer shells of high structural heterogeneity and thickness nonuniformity. The influence of related parameters (including the ratio of radius to average shell thickness, the ratio of transverse shear modulus to in-plane shear modulus, and the ratio of effective bending thickness to average shell thickness) on imperfection sensitivity is examined for pressured buckling. Our results show that the ratio of effective bending thickness to average shell thickness has a major effect on the imperfection sensitivity, while the effect of the ratio of transverse shear modulus to in-plane shear modulus is usually negligible. For example, with physically realistic parameters for typical imperfect spherical biopolymer shells, the present model predicts that actual maximum external pressure could be reduced to as low as 60% of that of a perfect UCA spherical shell or 55%-65% of that of a perfect spherical virus shell, respectively. The moderate imperfection sensitivity of spherical biopolymer shells with physically realistic imperfection is largely attributed to the fact that biopolymer shells are relatively thicker (defined by smaller radius-to-thickness ratio) and therefore practically realistic imperfection amplitude normalized by thickness is very small as compared to that of classical elastic thin shells which have much larger radius-to-thickness ratio.

  13. Imperfection sensitivity of pressured buckling of biopolymer spherical shells.

    PubMed

    Zhang, Lei; Ru, C Q

    2016-06-01

    Imperfection sensitivity is essential for mechanical behavior of biopolymer shells [such as ultrasound contrast agents (UCAs) and spherical viruses] characterized by high geometric heterogeneity. In this work, an imperfection sensitivity analysis is conducted based on a refined shell model recently developed for spherical biopolymer shells of high structural heterogeneity and thickness nonuniformity. The influence of related parameters (including the ratio of radius to average shell thickness, the ratio of transverse shear modulus to in-plane shear modulus, and the ratio of effective bending thickness to average shell thickness) on imperfection sensitivity is examined for pressured buckling. Our results show that the ratio of effective bending thickness to average shell thickness has a major effect on the imperfection sensitivity, while the effect of the ratio of transverse shear modulus to in-plane shear modulus is usually negligible. For example, with physically realistic parameters for typical imperfect spherical biopolymer shells, the present model predicts that actual maximum external pressure could be reduced to as low as 60% of that of a perfect UCA spherical shell or 55%-65% of that of a perfect spherical virus shell, respectively. The moderate imperfection sensitivity of spherical biopolymer shells with physically realistic imperfection is largely attributed to the fact that biopolymer shells are relatively thicker (defined by smaller radius-to-thickness ratio) and therefore practically realistic imperfection amplitude normalized by thickness is very small as compared to that of classical elastic thin shells which have much larger radius-to-thickness ratio.

  14. Dynamics of microparticles trapped in a perfect vortex beam.

    PubMed

    Chen, Mingzhou; Mazilu, Michael; Arita, Yoshihiko; Wright, Ewan M; Dholakia, Kishan

    2013-11-15

    We analyze microparticle dynamics within a "perfect" vortex beam. In contrast to other vortex fields, for any given integer value of the topological charge, a "perfect" vortex beam has the same annular intensity profile with fixed radius of peak intensity. For a given topological charge, the field possesses a well-defined orbital angular momentum density at each point in space, invariant with respect to azimuthal position. We experimentally create a perfect vortex and correct the field in situ, to trap and set in motion trapped microscopic particles. For a given topological charge, a single trapped particle exhibits the same local angular velocity moving in such a field independent of its azimuthal position. We also investigate particle dynamics in "perfect" vortex beams of fractional topological charge. This light field may be applied for novel studies in optical trapping of particles, atoms, and quantum gases.

  15. Wide scanning spherical antenna

    NASA Technical Reports Server (NTRS)

    Shen, Bing (Inventor); Stutzman, Warren L. (Inventor)

    1995-01-01

    A novel method for calculating the surface shapes for subreflectors in a suboptic assembly of a tri-reflector spherical antenna system is introduced, modeled from a generalization of Galindo-Israel's method of solving partial differential equations to correct for spherical aberration and provide uniform feed to aperture mapping. In a first embodiment, the suboptic assembly moves as a single unit to achieve scan while the main reflector remains stationary. A feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan thereby eliminating the need to oversize the main spherical reflector. In an alternate embodiment, both the main spherical reflector and the suboptic assembly are fixed. A flat mirror is used to create a virtual image of the suboptic assembly. Scan is achieved by rotating the mirror about the spherical center of the main reflector. The feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan.

  16. Magnetically tunable metamaterial perfect absorber

    NASA Astrophysics Data System (ADS)

    Lei, Ming; Feng, Ningyue; Wang, Qingmin; Hao, Yanan; Huang, Shanguo; Bi, Ke

    2016-06-01

    A magnetically tunable metamaterial perfect absorber (MPA) based on ferromagnetic resonance is experimentally and numerically demonstrated. The ferrite-based MPA is composed of an array of ferrite rods and a metallic ground plane. Frequency dependent absorption of the ferrite-based MPA under a series of applied magnetic fields is discussed. An absorption peak induced by ferromagnetic resonance appears in the range of 8-12 GHz under a certain magnetic field. Both the simulated and experimental results demonstrate that the absorption frequency of the ferrite-based MPA can be tuned by the applied magnetic field. This work provides an effective way to fabricate the magnetically tunable metamaterial perfect absorber.

  17. Factors influencing perfect surgical outcome.

    PubMed

    Lim, A S

    1997-03-01

    With affluence and education, the population of Asia will be demanding quality surgical care. The energetic, affluent and educated Asian professionals and business communities in the cities demand the best; and in surgery, they seek perfect results. Perfect results require a combination of 3 factors: the skill, knowledge and experience of the surgeon. He must be a skilled surgeon with good basic surgical techniques and also technical skills in the management of his discipline combined with meticulous attention to details. Furthermore, he must have a clear knowledge of the basic physiopathology of surgical principles of the condition he is to manage. Experience with difficult situations and intrasurgical problems are essential for success.

  18. Experimental realization of coherent perfect polarization rotation.

    PubMed

    Zhou, Chuanhong; Andrews, James H; Crescimanno, Michael

    2016-05-15

    Coherent perfect processes enable high optical efficiencies in optical conversion phenomena such as coherent perfect absorption or coherent perfect polarization rotation. A linear optical coherent perfect process based on Faraday rotation has been evaluated experimentally, achieving contrast limited by other optical components of the system and demonstrating like-parity resonance doublets above threshold.

  19. Radiative transfer in spherical atmospheres

    NASA Astrophysics Data System (ADS)

    Kalkofen, W.; Wehrse, R.

    A method for defining spherical model atmospheres in radiative/convective and hydrostatic equilibrium is presented. A finite difference form is found for the transfer equation and a matrix operator is developed as the discrete space analog (in curvilinear coordinates) of a formal integral in plane geometry. Pressure is treated as a function of temperature. Flux conservation is maintained within the energy equation, although the correct luminosity transport must be assigned for any given level of the atmosphere. A perturbed integral operator is used in a complete linearization of the transfer and constraint equations. Finally, techniques for generating stable solutions in economical computer time are discussed.

  20. Large displacement spherical joint

    DOEpatents

    Bieg, Lothar F.; Benavides, Gilbert L.

    2002-01-01

    A new class of spherical joints has a very large accessible full cone angle, a property which is beneficial for a wide range of applications. Despite the large cone angles, these joints move freely without singularities.

  1. The Precessing Spherical Pendulum.

    ERIC Educational Resources Information Center

    Olsson, M. G.

    1978-01-01

    Explains how the spherical pendulum could be used to observe nonreentrant orbits, and shows, using theoretical analysis, that for small displacements the elliptical orbit will precess at a rate proportional to its area. (GA)

  2. Steady accretion of an elastic body on a hard spherical surface and the notion of a four-dimensional reference space

    NASA Astrophysics Data System (ADS)

    Tomassetti, Giuseppe; Cohen, Tal; Abeyaratne, Rohan

    2016-11-01

    Taking the cue from experiments on actin growth on spherical beads, we formulate and solve a model problem describing the accretion of an incompressible elastic solid on a rigid sphere due to attachment of diffusing free particles. One of the peculiar characteristics of this problem is that accretion takes place on the interior surface that separates the body from its support rather than on its exterior surface, and hence is responsible for stress accumulation. Simultaneously, ablation takes place at the outer surface where material is removed from the body. As the body grows, mechanical effects associated with the build-up of stress and strain energy slow down accretion and promote ablation. Eventually, the system reaches a point where internal accretion is balanced by external ablation. The present study is concerned with this stationary regime called "treadmilling". The principal ingredients of our model are: a nonstandard choice of the reference configuration, which allows us to cope with the continually evolving material structure; and a driving force and a kinetic law for accretion/ablation that involves the difference in chemical potential, strain energy and the radial stress. By combining these ingredients we arrive at an algebraic system which governs the stationary treadmilling state. We establish the conditions under which this system has a solution and we show that this solution is unique. Moreover, by an asymptotic analysis we show that for small beads the thickness of the solid is proportional to the radius of the support and is strongly affected by the stiffness of the solid, whereas for large beads the stiffness of the solid is essentially irrelevant, the thickness being proportional to a characteristic length that depends on the parameters that govern diffusion and accretion kinetics.

  3. Will a perfect model agree with perfect observations? The impact of spatial sampling

    NASA Astrophysics Data System (ADS)

    Schutgens, Nick A. J.; Gryspeerdt, Edward; Weigum, Natalie; Tsyro, Svetlana; Goto, Daisuke; Schulz, Michael; Stier, Philip

    2016-05-01

    The spatial resolution of global climate models with interactive aerosol and the observations used to evaluate them is very different. Current models use grid spacings of ˜ 200 km, while satellite observations of aerosol use so-called pixels of ˜ 10 km. Ground site or airborne observations relate to even smaller spatial scales. We study the errors incurred due to different resolutions by aggregating high-resolution simulations (10 km grid spacing) over either the large areas of global model grid boxes ("perfect" model data) or small areas corresponding to the pixels of satellite measurements or the field of view of ground sites ("perfect" observations). Our analysis suggests that instantaneous root-mean-square (RMS) differences of perfect observations from perfect global models can easily amount to 30-160 %, for a range of observables like AOT (aerosol optical thickness), extinction, black carbon mass concentrations, PM2.5, number densities and CCN (cloud condensation nuclei). These differences, due entirely to different spatial sampling of models and observations, are often larger than measurement errors in real observations. Temporal averaging over a month of data reduces these differences more strongly for some observables (e.g. a threefold reduction for AOT), than for others (e.g. a twofold reduction for surface black carbon concentrations), but significant RMS differences remain (10-75 %). Note that this study ignores the issue of temporal sampling of real observations, which is likely to affect our present monthly error estimates. We examine several other strategies (e.g. spatial aggregation of observations, interpolation of model data) for reducing these differences and show their effectiveness. Finally, we examine consequences for the use of flight campaign data in global model evaluation and show that significant biases may be introduced depending on the flight strategy used.

  4. Casimir interactions of an object inside a spherical metal shell

    SciTech Connect

    Zaheer, Saad; Rahi, Sahand Jamal; Emig, Thorsten; Jaffe, Robert L.

    2010-03-15

    We investigate the electromagnetic Casimir interactions of an object contained within an otherwise empty, perfectly conducting spherical shell. For a small object we present analytical calculations of the force, which is directed away from the center of the cavity, and the torque, which tends to align the object opposite to the preferred alignment outside the cavity. For a perfectly conducting sphere as the interior object, we compute the corrections to the proximity force approximation (PFA) numerically. In both cases the results for the interior configuration match smoothly onto those for the corresponding exterior configuration.

  5. Effective perfect fluids in cosmology

    SciTech Connect

    Ballesteros, Guillermo; Bellazzini, Brando E-mail: brando.bellazzini@pd.infn.it

    2013-04-01

    We describe the cosmological dynamics of perfect fluids within the framework of effective field theories. The effective action is a derivative expansion whose terms are selected by the symmetry requirements on the relevant long-distance degrees of freedom, which are identified with comoving coordinates. The perfect fluid is defined by requiring invariance of the action under internal volume-preserving diffeomorphisms and general covariance. At lowest order in derivatives, the dynamics is encoded in a single function of the entropy density that characterizes the properties of the fluid, such as the equation of state and the speed of sound. This framework allows a neat simultaneous description of fluid and metric perturbations. Longitudinal fluid perturbations are closely related to the adiabatic modes, while the transverse modes mix with vector metric perturbations as a consequence of vorticity conservation. This formalism features a large flexibility which can be of practical use for higher order perturbation theory and cosmological parameter estimation.

  6. A Generalization of the Spherical Inversion

    ERIC Educational Resources Information Center

    Ramírez, José L.; Rubiano, Gustavo N.

    2017-01-01

    In the present article, we introduce a generalization of the spherical inversion. In particular, we define an inversion with respect to an ellipsoid, and prove several properties of this new transformation. The inversion in an ellipsoid is the generalization of the elliptic inversion to the three-dimensional space. We also study the inverse images…

  7. A Generalization of the Spherical Inversion

    ERIC Educational Resources Information Center

    Ramírez, José L.; Rubiano, Gustavo N.

    2017-01-01

    In the present article, we introduce a generalization of the spherical inversion. In particular, we define an inversion with respect to an ellipsoid, and prove several properties of this new transformation. The inversion in an ellipsoid is the generalization of the elliptic inversion to the three-dimensional space. We also study the inverse images…

  8. Sublithographic Architecture: Shifting the Responsibility for Perfection

    NASA Astrophysics Data System (ADS)

    Dehon, A.

    In the past, processing had orders of magnitude between devices and atoms (e.g., with silicon atom lattice spacing around 0.5 nm, a minimum size feature was roughly 2000 atoms wide when we had 1 μm feature sizes). It was the process engineer's job to craft this large collection of atoms into "perfect" devices. The circuit designer and architect could then design systems knowing the process engineer would always give them a set of perfect devices. As we continue to shrink our devices, we no longer have orders of magnitude between the devices and the atoms. As a result, the circuit designers and architects are beginning to work within a similar realm of atoms. Consequently, they must assume some of the responsibilities for dealing with atomic-scale imperfections and uncertainty. This demands a significant shift in our abstraction hierarchy, the responsibilities and expectations at each level in this hierarchy, our fabrication techniques, our testing strategies, and our approaches to design for these atomic-scale computing systems.

  9. Spherical geodesic mesh generation

    SciTech Connect

    Fung, Jimmy; Kenamond, Mark Andrew; Burton, Donald E.; Shashkov, Mikhail Jurievich

    2015-02-27

    In ALE simulations with moving meshes, mesh topology has a direct influence on feature representation and code robustness. In three-dimensional simulations, modeling spherical volumes and features is particularly challenging for a hydrodynamics code. Calculations on traditional spherical meshes (such as spin meshes) often lead to errors and symmetry breaking. Although the underlying differencing scheme may be modified to rectify this, the differencing scheme may not be accessible. This work documents the use of spherical geodesic meshes to mitigate solution-mesh coupling. These meshes are generated notionally by connecting geodesic surface meshes to produce triangular-prismatic volume meshes. This mesh topology is fundamentally different from traditional mesh topologies and displays superior qualities such as topological symmetry. This work describes the geodesic mesh topology as well as motivating demonstrations with the FLAG hydrocode.

  10. Infrared perfect absorber based on nanowire metamaterial cavities.

    PubMed

    He, Yingran; Deng, Huixu; Jiao, Xiangyang; He, Sailing; Gao, Jie; Yang, Xiaodong

    2013-04-01

    An infrared perfect absorber based on a gold nanowire metamaterial cavities array on a gold ground plane is designed. The metamaterial made of gold nanowires embedded in an alumina host exhibits an effective permittivity with strong anisotropy, which supports cavity resonant modes of both electric dipole and magnetic dipole. The impedance of the cavity modes matches the incident plane wave in free space, leading to nearly perfect light absorption. The incident optical energy is efficiently converted into heat so that the local temperature of the absorber will increase. Results show that the designed absorber is polarization-insensitive and nearly omnidirectional for the incident angle.

  11. Interference theory of metamaterial perfect absorbers.

    PubMed

    Chen, Hou-Tong

    2012-03-26

    The impedance matching to free space in metamaterial perfect absorbers has been believed to involve and rely on magnetic resonant response, with direct evidence provided by the anti-parallel surface currents in the metal structures. Here I present a different theoretical interpretation based on interference, which shows that the two layers of metal structures in metamaterial absorbers are linked only by multiple reflections with negligible near-field interactions or magnetic resonances. This is further supported by the out-of-phase surface currents derived at the interfaces of resonator array and ground plane through multiple reflections and superpositions. The theory developed here explains all features observed in narrowband metamaterial absorbers and therefore provides a profound understanding of the underlying physics.

  12. Compact expressions for spherically averaged position and momentum densities

    NASA Astrophysics Data System (ADS)

    Crittenden, Deborah L.; Bernard, Yves A.

    2009-08-01

    Compact expressions for spherically averaged position and momentum density integrals are given in terms of spherical Bessel functions (jn) and modified spherical Bessel functions (in), respectively. All integrals required for ab initio calculations involving s, p, d, and f-type Gaussian functions are tabulated, highlighting a neat isomorphism between position and momentum space formulae. Spherically averaged position and momentum densities are calculated for a set of molecules comprising the ten-electron isoelectronic series (Ne-CH4) and the eighteen-electron series (Ar-SiH4, F2-C2H6).

  13. Spherical mirror mount

    NASA Technical Reports Server (NTRS)

    Meyer, Jay L. (Inventor); Messick, Glenn C. (Inventor); Nardell, Carl A. (Inventor); Hendlin, Martin J. (Inventor)

    2011-01-01

    A spherical mounting assembly for mounting an optical element allows for rotational motion of an optical surface of the optical element only. In that regard, an optical surface of the optical element does not translate in any of the three perpendicular translational axes. More importantly, the assembly provides adjustment that may be independently controlled for each of the three mutually perpendicular rotational axes.

  14. [Greenhouse with a convex spherical planting surface as a prototype of space greenhouse and an instrument for studying the plant gravitropism].

    PubMed

    Berkovich, Iu A; Ziablova, N V; Erokhin, A N; Smolianina, S O; Krivobok, N M

    2007-01-01

    IBMP has developed a technology and unit for cultivating self-opening crops on a convex planting surface illuminated by light-emitting diodes mounted on an external concentric panel ("Hemisphere"). The unit has a structure of two-member clinostat with semispherical plant growth chamber with a 600-mm diameter and a speed of from 1 to 10 revo about each axis; water potential in the root supply system is maintained at 1.0 +/- 0.45 KPa. Having the data of 1200 measurements in the growth chamber, PAR latitude and meridian gradients were determined which did not exceed 0.7 micromol/(m2 x s x cm) in the work area and differed from the radial gradient by order and, therefore, had a negligible contribution to the axial organs' deviation from the radial directions during laboratory tests. Maximal centrifugal acceleration was equal to 10(-10) of the acceleration of gravity and did not impact the gravitropic crop reactions in the growth chamber. Five 5-day tests with semidwarf wheat Triticum aestivum L., cult. Lada were performed in the "Hemisphere" growth chamber turned at different angles relative to the gravity vector. In immobile growth chamber plants inclination from the vertical was a function of the angle between the PAR gradient and vector and the gravity vector at the site of each seed. Crop rotation at 3 revo about the horizontal axis did not produce noteworthy plant inclination suggesting neutralization of the plant geotropic reactions. In all tests about 80% of the plants formed the first leaf and about 20% reached the coleoptiles phase. Morphometric differences in the tests were insignificant. On a balance, the tests showed that prototype of space greenhouse "Hemisphere" is fit to run laboratory investigations of the plant gravitropic reactions in both static and dynamic conditions.

  15. High-order perturbations of a spherical collapsing star

    NASA Astrophysics Data System (ADS)

    Brizuela, David; Martín-García, José M.; Sperhake, Ulrich; Kokkotas, Kostas D.

    2010-11-01

    A formalism to deal with high-order perturbations of a general spherical background was developed in earlier work [D. Brizuela, J. M. Martín-García, and G. A. Mena Marugán, Phys. Rev. DPRVDAQ1550-7998 74, 044039 (2006);10.1103/PhysRevD.74.044039 D. Brizuela, J. M. Martín-García, and G. A. Mena Marugán, Phys. Rev. DPRVDAQ1550-7998 76, 024004 (2007)10.1103/PhysRevD.76.024004]. In this paper, we apply it to the particular case of a perfect fluid background. We have expressed the perturbations of the energy-momentum tensor at any order in terms of the perturbed fluid’s pressure, density, and velocity. In general, these expressions are not linear and have sources depending on lower-order perturbations. For the second-order case we make the explicit decomposition of these sources in tensor spherical harmonics. Then, a general procedure is given to evolve the perturbative equations of motions of the perfect fluid for any value of the harmonic label. Finally, with the problem of a spherical collapsing star in mind, we discuss the high-order perturbative matching conditions across a timelike surface, in particular, the surface separating the perfect fluid interior from the exterior vacuum.

  16. High-order perturbations of a spherical collapsing star

    SciTech Connect

    Brizuela, David; Martin-Garcia, Jose M.; Sperhake, Ulrich; Kokkotas, Kostas D.

    2010-11-15

    A formalism to deal with high-order perturbations of a general spherical background was developed in earlier work [D. Brizuela, J. M. Martin-Garcia, and G. A. Mena Marugan, Phys. Rev. D 74, 044039 (2006); D. Brizuela, J. M. Martin-Garcia, and G. A. Mena Marugan, Phys. Rev. D 76, 024004 (2007)]. In this paper, we apply it to the particular case of a perfect fluid background. We have expressed the perturbations of the energy-momentum tensor at any order in terms of the perturbed fluid's pressure, density, and velocity. In general, these expressions are not linear and have sources depending on lower-order perturbations. For the second-order case we make the explicit decomposition of these sources in tensor spherical harmonics. Then, a general procedure is given to evolve the perturbative equations of motions of the perfect fluid for any value of the harmonic label. Finally, with the problem of a spherical collapsing star in mind, we discuss the high-order perturbative matching conditions across a timelike surface, in particular, the surface separating the perfect fluid interior from the exterior vacuum.

  17. Interference control of perfect photon absorption in cavity quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Wang, Liyong; Di, Ke; Zhu, Yifu; Agarwal, G. S.

    2017-01-01

    We propose and analyze a scheme for controlling coherent photon transmission and reflection in a cavity-quantum-electrodynamics (CQED) system consisting of an optical resonator coupled with three-level atoms coherently prepared by a control laser from free space. When the control laser is off and the cavity is excited by two identical light fields from two ends of the cavity, the two input light fields can be completely absorbed by the CQED system and the light energy is converted into the excitation of the polariton states, but no light can escape from the cavity. Two distinct cases of controlling the perfect photon absorption are analyzed: (a) when the control laser is tuned to the atomic resonance and creates electromagnetically induced transparency, the perfect photon absorption is suppressed and the input light fields are nearly completely transmitted through the cavity; (b) when the control laser is tuned to the polariton state resonance and inhibits the polariton state excitation, the perfect photon absorption is again suppressed and the input light fields are nearly completely reflected from the cavity. Thus, the CQED system can act as a perfect absorber or near-perfect transmitter and/or reflector by simply turning the control laser off or on. Such interference control of the coherent photon-atom interaction in the CQED system should be useful for a variety of applications in optical logical devices.

  18. Disordered spherical bead packs are anisotropic

    NASA Astrophysics Data System (ADS)

    Schröder-Turk, G. E.; Mickel, W.; Schröter, M.; Delaney, G. W.; Saadatfar, M.; Senden, T. J.; Mecke, K.; Aste, T.

    2010-05-01

    Investigating how tightly objects pack space is a long-standing problem, with relevance for many disciplines from discrete mathematics to the theory of glasses. Here we report on the fundamental yet so far overlooked geometric property that disordered mono-disperse spherical bead packs have significant local structural anisotropy manifest in the shape of the free space associated with each bead. Jammed disordered packings from several types of experiments and simulations reveal very similar values of the cell anisotropy, showing a linear decrease with packing fraction. Strong deviations from this trend are observed for unjammed configurations and for partially crystalline packings above 64%. These findings suggest an inherent geometrical reason why, in disordered packings, anisotropic shapes can fill space more efficiently than spheres, and have implications for packing effects in non-spherical liquid crystals, foams and structural glasses.

  19. Gravitational energy in spherical symmetry

    NASA Astrophysics Data System (ADS)

    Hayward, Sean A.

    1996-02-01

    Various properties of the Misner-Sharp spherically symmetric gravitational energy E are established or reviewed. In the Newtonian limit of a perfect fluid, E yields the Newtonian mass to leading order and the Newtonian kinetic and potential energy to the next order. For test particles, the corresponding Hájíček energy is conserved and has the behavior appropriate to energy in the Newtonian and special-relativistic limits. In the small-sphere limit, the leading term in E is the product of volume and the energy density of the matter. In vacuo, E reduces to the Schwarzschild energy. At null and spatial infinity, E reduces to the Bondi-Sachs and Arnowitt-Deser-Misner energies, respectively. The conserved Kodama current has charge E. A sphere is trapped if E>1/2r, marginal if E=1/2r, and untrapped if E<1/2r, where r is the areal radius. A central singularity is spatial and trapped if E>0, and temporal and untrapped if E<0. On an untrapped sphere, E is nondecreasing in any outgoing spatial or null direction, assuming the dominant energy condition. It follows that E>=0 on an untrapped spatial hypersurface with a regular center, and E>=1/2r0 on an untrapped spatial hypersurface bounded at the inward end by a marginal sphere of radius r0. All these inequalities extend to the asymptotic energies, recovering the Bondi-Sachs energy loss and the positivity of the asymptotic energies, as well as proving the conjectured Penrose inequality for black or white holes. Implications for the cosmic censorship hypothesis and for general definitions of gravitational energy are discussed.

  20. Development of soft X-ray multilayer laminar-type plane gratings and varied-line-spacing spherical grating for flat-field spectrograph in the 1-8 keV region

    NASA Astrophysics Data System (ADS)

    Koike, Masato; Ishino, Masahiko; Imazono, Takashi; Sano, Kazuo; Sasai, Hiroyuki; Hatayama, Masatoshi; Takenaka, Hisataka; Heimann, Philip A.; Gullikson, Eric M.

    2009-08-01

    W/C and Co/SiO 2 multilayer laminar-type holographic plane gratings (groove density 1/σ = 1200 lines/mm) in the 1-8 keV region are developed. For the Co/SiO 2 grating the diffraction efficiencies of 0.41 and 0.47 at 4 and 6 keV, respectively, and for the W/C grating 0.38 at 8 keV are observed. Taking advantage of the outstanding high diffraction efficiencies into practical soft X-ray spectrographs a Mo/SiO 2 multilayer varied-line-spacing (VLS) laminar-type spherical grating (1/σ = 2400 lines/mm) is also developed for use with a flat field spectrograph in the region of 1.7 keV. For the Mo/SiO 2 multilayer grating the diffraction efficiencies of 0.05-0.20 at 0.9-1.8 keV are observed. The FWHMs of the measured line profiles of Hf-Mα 1(1644.6 eV), Si-Kα 1(1740.0 eV), and W-Mα 1 (1775.4 eV) are 13.7 eV, 8.0 eV, and 8.7 eV, respectively.

  1. Spherical coordinate descriptions of cylindrical and spherical Bessel beams.

    PubMed

    Poletti, M A

    2017-03-01

    This paper derives a generalized spherical harmonic description of Bessel beams. The spherical harmonic description of the well-known cylindrical Bessel beams is reviewed and a family of spherical Bessel beams are introduced which can provide a number of azimuthal phase variations for a single beam radial amplitude. The results are verified by numerical simulations.

  2. Spherical torus fusion reactor

    DOEpatents

    Peng, Yueng-Kay M.

    1989-01-01

    A fusion reactor is provided having a near spherical-shaped plasma with a modest central opening through which straight segments of toroidal field coils extend that carry electrical current for generating a toroidal magnet plasma confinement fields. By retaining only the indispensable components inboard of the plasma torus, principally the cooled toroidal field conductors and in some cases a vacuum containment vessel wall, the fusion reactor features an exceptionally small aspect ratio (typically about 1.5), a naturally elongated plasma cross section without extensive field shaping, requires low strength magnetic containment fields, small size and high beta. These features combine to produce a spherical torus plasma in a unique physics regime which permits compact fusion at low field and modest cost.

  3. Spherical torus fusion reactor

    DOEpatents

    Peng, Yueng-Kay M.

    1989-04-04

    A fusion reactor is provided having a near spherical-shaped plasma with a modest central opening through which straight segments of toroidal field coils extend that carry electrical current for generating a toroidal magnet plasma confinement fields. By retaining only the indispensable components inboard of the plasma torus, principally the cooled toroidal field conductors and in some cases a vacuum containment vessel wall, the fusion reactor features an exceptionally small aspect ratio (typically about 1.5), a naturally elongated plasma cross section without extensive field shaping, requires low strength magnetic containment fields, small size and high beta. These features combine to produce a spherical torus plasma in a unique physics regime which permits compact fusion at low field and modest cost.

  4. Noncommuting spherical coordinates

    SciTech Connect

    Bander, Myron

    2004-10-15

    Restricting the states of a charged particle to the lowest Landau level introduces a noncommutativity between Cartesian coordinate operators. This idea is extended to the motion of a charged particle on a sphere in the presence of a magnetic monopole. Restricting the dynamics to the lowest energy level results in noncommutativity for angular variables and to a definition of a noncommuting spherical product. The values of the commutators of various angular variables are not arbitrary but are restricted by the discrete magnitude of the magnetic monopole charge. An algebra, isomorphic to angular momentum, appears. This algebra is used to define a spherical star product. Solutions are obtained for dynamics in the presence of additional angular dependent potentials.

  5. Hollow spherical shell manufacture

    DOEpatents

    O'Holleran, Thomas P.

    1991-01-01

    A process for making a hollow spherical shell of silicate glass composition in which an aqueous suspension of silicate glass particles and an immiscible liquid blowing agent is placed within the hollow spherical cavity of a porous mold. The mold is spun to reduce effective gravity to zero and to center the blowing agent, while being heated so as to vaporize the immiscible liquid and urge the water carrier of the aqueous suspension to migrate into the body of the mold, leaving a green shell compact deposited around the mold cavity. The green shell compact is then removed from the cavity, and is sintered for a time and a temperature sufficient to form a silicate glass shell of substantially homogeneous composition and uniform geometry.

  6. Hollow spherical shell manufacture

    DOEpatents

    O'Holleran, T.P.

    1991-11-26

    A process is disclosed for making a hollow spherical shell of silicate glass composition in which an aqueous suspension of silicate glass particles and an immiscible liquid blowing agent is placed within the hollow spherical cavity of a porous mold. The mold is spun to reduce effective gravity to zero and to center the blowing agent, while being heated so as to vaporize the immiscible liquid and urge the water carrier of the aqueous suspension to migrate into the body of the mold, leaving a green shell compact deposited around the mold cavity. The green shell compact is then removed from the cavity, and is sintered for a time and a temperature sufficient to form a silicate glass shell of substantially homogeneous composition and uniform geometry. 3 figures.

  7. In search of perfect reads.

    PubMed

    Pal, Soumitra; Aluru, Srinivas

    2015-01-01

    Continued advances in next generation short-read sequencing technologies are increasing throughput and read lengths, while driving down error rates. Taking advantage of the high coverage sampling used in many applications, several error correction algorithms have been developed to improve data quality further. However, correcting errors in high coverage sequence data requires significant computing resources. We propose a different approach to handle erroneous sequence data. Presently, error rates of high-throughput platforms such as the Illumina HiSeq are within 1%. Moreover, the errors are not uniformly distributed in all reads, and a large percentage of reads are indeed error-free. Ability to predict such perfect reads can significantly impact the run-time complexity of applications. We present a simple and fast k-spectrum analysis based method to identify error-free reads. The filtration process to identify and weed out erroneous reads can be customized at several levels of stringency depending upon the downstream application need. Our experiments show that if around 80% of the reads in a dataset are perfect, then our method retains almost 99.9% of them with more than 90% precision rate. Though filtering out reads identified as erroneous by our method reduces the average coverage by about 7%, we found the remaining reads provide as uniform a coverage as the original dataset. We demonstrate the effectiveness of our approach on an example downstream application: we show that an error correction algorithm, Reptile, which rely on collectively analyzing the reads in a dataset to identify and correct erroneous bases, instead use reads predicted to be perfect by our method to correct the other reads, the overall accuracy improves further by up to 10%. Thanks to the continuous technological improvements, the coverage and accuracy of reads from dominant sequencing platforms have now reached an extent where we can envision just filtering out reads with errors, thus making

  8. Spherical nitroguanidine process

    DOEpatents

    Sanchez, John A.; Roemer, Edward L.; Stretz, Lawrence A.

    1990-01-01

    A process of preparing spherical high bulk density nitroguanidine by dissing low bulk density nitroguanidine in N-methyl pyrrolidone at elevated temperatures and then cooling the solution to lower temperatures as a liquid characterized as a nonsolvent for the nitroguanidine is provided. The process is enhanced by inclusion in the solution of from about 1 ppm up to about 250 ppm of a metal salt such as nickel nitrate, zinc nitrate or chromium nitrate, preferably from about 20 to about 50 ppm.

  9. Revisiting perfect fluid dark matter: Observational constraints from our galaxy

    NASA Astrophysics Data System (ADS)

    Potapov, Alexander A.; Garipova, Guzel M.; Nandi, Kamal K.

    2016-02-01

    We revisit certain features of an assumed spherically symmetric perfect fluid dark matter halo in the light of the observed data of our galaxy, the Milky Way (MW). The idea is to apply the Faber-Visser approach of combined observations of rotation curves and lensing to a first post-Newtonian approximation to "measure" the equation of state ω (r) of the perfect fluid galactic halo. However, for the model considered here, no constraints from lensing are used as it will be sufficient to consider only the rotation curve observations. The lensing mass together with other masses will be just computed using recent data. Since the halo has attractive gravity, we shall impose the constraint that ω (r) ≥ 0 for r ≤RMW, where RMW ∼ 200 kpc is the adopted halo radius of our galaxy. The observed circular velocity ℓ (= 2 vc2 / c02) from the flat rotation curve and a crucial adjustable parameter D appearing in the perfect fluid solution then yield different numerical ranges of ω (r). It is demonstrated that the computed observables such as the rotation curve mass, the lens mass, the post-Newtonian mass of our galaxy compare well with the recent mass data. We also calculate the Faber-Visser χ-factor, which is a measure of pressure content in the dark matter. Our analysis indicates that a range 0 ≤ ω (r) ≤ 2.8 ×10-7 for the perfect fluid dark matter can reasonably describe the attractive galactic halo. This is a strong constraint indicating a dust-like CDM halo (ω ∼ 0) supported also by CMB constraints.

  10. Conformal and traversable wormholes with monopole and perfect fluid in f(R)-gravity

    NASA Astrophysics Data System (ADS)

    Taşer, Doǧukan; Doǧru, Melis Ulu

    2016-10-01

    We investigate spherically symmetric spacetime filled with global monopole and perfect fluid in f(R)-gravity. We consider field equations of f(R)-gravity in order to understand the global monopole and the perfect fluid curve to the spacetime. It has taken advantages of conformal symmetry properties of the spacetime to solve these equations. The obtained solutions are improved in case of phantom energy. It is shown that obtained f(R) function is consistent with well-known models of the modified gravity. Also, it is examined whether the obtained solutions support a traversable wormhole geometry. Obtained results of the solutions have been concluded.

  11. Perfect fluid and scalar field in the Reissner-Nordstroem metric

    SciTech Connect

    Babichev, E. O.; Dokuchaev, V. I. Eroshenko, Yu. N.

    2011-05-15

    We describe the spherically symmetric steady-state accretion of perfect fluid in the Reissner-Nordstroem metric. We present analytic solutions for accretion of a fluid with linear equations of state and of the Chaplygin gas. We also show that under reasonable physical conditions, there is no steady-state accretion of a perfect fluid onto a Reissner-Nordstroem naked singularity. Instead, a static atmosphere of fluid is formed. We discuss a possibility of violation of the third law of black hole thermodynamics for a phantom fluid accretion.

  12. Electrical properties of spherical syncytia.

    PubMed Central

    Eisenberg, R S; Barcilon, V; Mathias, R T

    1979-01-01

    Syncytial tissues consist of many cells whose intracellular spaces are electrically coupled one to another. Such tissues typically include narrow, tortuous extracellular space and often have specialized membranes at their outer surface. We derive differential equations to describe the potentials induced when a sinusoidal or steady current is applied to the intracellular space with a microelectrode. We derive solutions for spherical preparations with isotropic properties or with a particular anisotropy in effective extracellular and intracellular resistivities. Solutions are presented in an approximate form with a simple physical interpretation. The leading term in the intracellular potential describes an "isopotential" cell in which there is no spatial variation of intracellular potential. The leading term in the extracellular potential, and thus the potential across the inner membranes, varies with radial position, even at zero frequency. The next term of the potentials describes the direct effects of the point source of current and, for the parameters given here, acts as a series resistance producing a large local potential drop essentially independent of frequency. A lumped equivalent circuit describes the "low frequency" behavior of the syncytium, and a distributed circuit gives a reasonably accurate general description. Graphs of the spatial variation and frequency dependence of intracellular, extracellular, and transmembrane potential are given, the response to sinusoidal currents is used to calculate numerically the response to a step function of current. PMID:262383

  13. Stability of thick spherical shells

    NASA Astrophysics Data System (ADS)

    Liu, I.-Shih

    1995-06-01

    The pressure-radius relation of spherical rubber balloons has been derived and its stability behavior investigated before. In this work, we show that similar results remain valid for thick spherical shells of Mooney-Rivlin materials. In addition, we show that eversion of a spherical shell is possible for any incompressible isotropic materials if the shell is not too thick.

  14. CLASSICAL AREAS OF PHENOMENOLOGY: Material parameter equation for rotating elliptical spherical cloaks

    NASA Astrophysics Data System (ADS)

    Ma, Hua; Qu, Shao-Bo; Xu, Zhuo; Zhang, Jie-Qiu; Wang, Jia-Fu

    2009-01-01

    By using the coordinate transformation method, we have deduced the material parameter equation for rotating elliptical spherical cloaks and carried out simulation as well. The results indicate that the rotating elliptical spherical cloaking shell, which is made of meta-materials whose permittivity and permeability are governed by the equation deduced in this paper, can achieve perfect invisibility by excluding electromagnetic fields from the internal region without disturbing any external field.

  15. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Atlantis roars toward space on mission STS-106 as it lifts off in a perfect launch at 8:45:47 a.m. EDT today. On the 11-day mission to the International Space Station, the seven- member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  16. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Atlantis appears to burst forth from a cocoon of smoke in the Florida marsh lands as it rockets toward space on mission STS-106. The perfect on-time liftoff of Atlantis occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbe d is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  17. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A perfect launch sends Space Shuttle Atlantis, leaving a trail of flames and billows of smoke and clouds behind, hurtling toward space on mission STS-106. Liftoff occurred at 8:45:47 a.m. EDT today. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  18. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Atlantis appears to burst forth from a cocoon of smoke as it rockets toward space on mission STS-106. The perfect on-time liftoff of Atlantis occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven- member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  19. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Filling the ground with billows of smoke and steam created by the flaming solid rocket boosters, Space Shuttle Atlantis speeds toward space on mission STS-106. The perfect on-time liftoff occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbe d is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  20. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Atlantis rises from a cocoon of smoke as it rockets toward space on mission STS-106. The perfect on-time liftoff of Atlantis occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  1. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Atlantis clears the tower as it roars into space on mission STS-106 after a perfect on-time launch at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  2. Systematic Calibration for a Backpacked Spherical Photogrammetry Imaging System

    NASA Astrophysics Data System (ADS)

    Rau, J. Y.; Su, B. W.; Hsiao, K. W.; Jhan, J. P.

    2016-06-01

    A spherical camera can observe the environment for almost 720 degrees' field of view in one shoot, which is useful for augmented reality, environment documentation, or mobile mapping applications. This paper aims to develop a spherical photogrammetry imaging system for the purpose of 3D measurement through a backpacked mobile mapping system (MMS). The used equipment contains a Ladybug-5 spherical camera, a tactical grade positioning and orientation system (POS), i.e. SPAN-CPT, and an odometer, etc. This research aims to directly apply photogrammetric space intersection technique for 3D mapping from a spherical image stereo-pair. For this purpose, several systematic calibration procedures are required, including lens distortion calibration, relative orientation calibration, boresight calibration for direct georeferencing, and spherical image calibration. The lens distortion is serious on the ladybug-5 camera's original 6 images. Meanwhile, for spherical image mosaicking from these original 6 images, we propose the use of their relative orientation and correct their lens distortion at the same time. However, the constructed spherical image still contains systematic error, which will reduce the 3D measurement accuracy. Later for direct georeferencing purpose, we need to establish a ground control field for boresight/lever-arm calibration. Then, we can apply the calibrated parameters to obtain the exterior orientation parameters (EOPs) of all spherical images. In the end, the 3D positioning accuracy after space intersection will be evaluated, including EOPs obtained by structure from motion method.

  3. Haplotyping as perfect phylogeny: a direct approach.

    PubMed

    Bafna, Vineet; Gusfield, Dan; Lancia, Giuseppe; Yooseph, Shibu

    2003-01-01

    list of "future work" in Gusfield (2002) began with the task of developing a simpler, more direct, yet still efficient algorithm. This paper accomplishes that goal, for both the rooted and unrooted PPH problems. It establishes a simple, easy-to-program, O(nm(2))-time algorithm that determines whether there is a PPH solution for input genotypes and produces a linear-space data structure to represent all of the solutions. The approach allows complete, self-contained proofs. In addition to algorithmic simplicity, the approach here makes the representation of all solutions more intuitive than in Gusfield (2002), and solves another goal from that paper, namely, to prove a nontrivial upper bound on the number of PPH solutions, showing that that number is vastly smaller than the number of haplotype solutions (each solution being a set of n pairs of haplotypes that can generate the genotypes) when the perfect phylogeny requirement is not imposed.

  4. Optical design of zero-power Hubble Space Telescope wave-front correctors for null testing.

    PubMed

    Hannan, P G; Davila, P; Wood, H J

    1993-04-01

    The optical design of the second-generation wide-field/planetary-camera instrument for the Hubble Space Telescope has been modified to compensate for the spherical aberration of the optical telescope assembly (OTA) by introduction of undercorrected spherical aberration into the wave front. This instrument can be tested in a simple manner to ensure that its aberration contribution has the proper sign and magnitude. We present designs for a near-zero power doublet lens that can be used to generate a spherically aberrated wave front that is similar to the OTA wave front. When this lens is used in combination with the instrument, a near-perfect or nulled wave front should be produced, resulting in a high-quality point image on axis. We also present lens designs for a similar test that can be performed on the OTA simulators now being built to verify the other second-generation instruments.

  5. Optical design of zero-power Hubble Space Telescope wave-front correctors for null testing

    NASA Technical Reports Server (NTRS)

    Hannan, Paul G.; Davila, Pam; Wood, H. J.

    1993-01-01

    The optical design of the second-generation wide-field/planetary-camera instrument for the Hubble Space Telescope has been modified to compensate for the spherical aberration of the optical telescope assembly (OTA) by introduction of undercorrected spherical aberration into the wave front. This instrument can be tested in a simple manner to ensure that its aberration contribution has the proper sign and magnitude. We present designs for a near-zero power doublet lens that can be used to generate a spherically aberrated wave front that is similar to the OTA wave front. When this lens is used in combination with the instrument, a near-perfect or nulled wave front should be produced, resulting in a high-quality point image on axis. We also present lens designs for a similar test that can be performed on the OTA simulators now being built to verify the other second-generation instruments.

  6. Optical design of zero-power Hubble Space Telescope wave-front correctors for null testing

    NASA Technical Reports Server (NTRS)

    Hannan, Paul G.; Davila, Pam; Wood, H. J.

    1993-01-01

    The optical design of the second-generation wide-field/planetary-camera instrument for the Hubble Space Telescope has been modified to compensate for the spherical aberration of the optical telescope assembly (OTA) by introduction of undercorrected spherical aberration into the wave front. This instrument can be tested in a simple manner to ensure that its aberration contribution has the proper sign and magnitude. We present designs for a near-zero power doublet lens that can be used to generate a spherically aberrated wave front that is similar to the OTA wave front. When this lens is used in combination with the instrument, a near-perfect or nulled wave front should be produced, resulting in a high-quality point image on axis. We also present lens designs for a similar test that can be performed on the OTA simulators now being built to verify the other second-generation instruments.

  7. Maxwell's fish-eye lens and the mirage of perfect imaging

    NASA Astrophysics Data System (ADS)

    Merlin, R.

    2011-02-01

    Recent claims that Maxwell's fish-eye is a perfect lens, capable of providing images with deep subwavelength resolution, are examined. We show that the imaging properties of a dispersionless fish-eye are very similar to those of an ideal spherical cavity. Using this correspondence, we prove that the correct solution to Maxwell equations in the fish-eye gives image sizes that are consistent with the standard diffraction limit. Perfect focusing is an optical illusion that results from placing a time-reversed source at the position of the geometrical image which, when combined with the field due to the primary (object) source, mimics the behavior of a perfect drain. Issues of causality are briefly discussed. We also demonstrate that passive outlets are not a good alternative to time-reversed sources for broadband drain-like behavior and that, even if they were, they could not do a better job than conventional optical systems at providing high resolution.

  8. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A perfect on-time launch for Atlantis as it rockets toward space on mission STS-106. Liftoff occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven- member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  9. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Atlantis streaks into the sky on mission STS-106 after a perfect on-time launch at 8:45:47 a.m. EDT. Blue mach diamonds are barely visible behind the main engine nozzles. On the 11-day mission to the International Space Station, the seven- member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbe d is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  10. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Billows of clouds and smoke frame Space Shuttle Atlantis after a perfect on-time launch on mission STS-106 at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven- member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  11. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    After a perfect on-time launch on mission STS-106 at 8:45:47 a.m. EDT, Space Shuttle Atlantis rolls and displays its external tank and solid rocket boosters. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  12. Spherical artifacts on ferrograms

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1976-01-01

    In the past, hollow spheres detected on ferrograms have been interpreted as being due to fretting, abrasion, cavitation erosion, and fatigue-related processes. Here it is reported that such spheres were found to result from the fact that a routine grinding operation on a steel plate was carried out about 20 feet away from the ferrograph. A similar grinding operation was performed on a piece of low carbon steel a few feet from the ferrograph, and after a few minutes of grinding, the resulting ferrogram contained thousands of particles of which more than 90% were spherical. Because of the widespread occurrence of ordinary grinding operations, it seems prudent that those utilizing the ferrograph be cognizant of this type of artifact.

  13. Vibration modes of spherical shells and containment vessels.

    SciTech Connect

    Duffey, T. A.; Romero, C. D.

    2001-01-01

    Spherical pressure vessels are used to fully contain the effects of high explosions. In this paper, the vibrations of a spherical containment vessel undergoing elastic response are investigated. Vibration modes of containment vessels are of particular interest, as it is the superposition and interaction of different modes of response with closely spaced frequencies that has been reported to be the mechanism of 'strain growth'. First, the modal frequencies of a spherical shell for both axisymmetric and nonaxisymmetric response modes are discussed, based on a sequence of papers that have appeared in the open literature. Analytical predictions are then compared with numerical simulations using ABAQUS. It is found that the numerical simulations accurately predict both the axisymmetric and nonaxisymmetric modal frequencies for the complete spherical shell. Next, numerical simulations of modal frequencies for the more complex spherical containment vessel (with nozzles) are compared with the spherical shell results. Numerical simulations for the spherical containment vessel reveal that frequencies are somewhat similar to the complete spherical shell. Limited comparisons with experimentally recorded frequencies for participating modes of vessel dynamic response during high explosive containment testing are presented as well.

  14. Spherical grating spectrometers

    NASA Astrophysics Data System (ADS)

    O'Donoghue, Darragh; Clemens, J. Christopher

    2014-07-01

    We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based instruments. We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface relief gratings; they have become the disperser of choice in optical / NIR spectrometers. The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and reduction in size. We describe a "Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary applications, including a design for a double-beam spectrometer without any requirement for a dichroic. This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs, using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout avoids a major drawback of the previous generation of catadioptric spectrometer designs. We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design, demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage is now set for construction of a prototype instrument with impressive performance.

  15. Turnable perfect absorption at infrared frequencies by a Graphene-hBN Hyper Crystal.

    PubMed

    Wu, Jipeng; Jiang, Leyong; Guo, Jun; Dai, Xiaoyu; Xiang, Yuanjiang; Wen, Shuangchun

    2016-07-25

    In this article, we have theoretically demonstrated that the perfect absorption at infrared frequencies can be achieved and controlled by using a graphene-hexagonal Boron Nitride (hBN) hyper crystal. hBN, the latest natural hyperbolic material, can be regarded as an excellent substrate to form a hyper crystal with graphene. Although the perfect absorption by a half-space of hBN crystal can be achieved due to its high optical anisotropy, but the perfect absorption can only appear at certain fixed wavenumber and incidence angle. By introducing a graphene-hBN hyper crystal, we can get perfect absorption at different wavenumbers and incidence angles by varying the Fermi energy level of graphene sheets via electrostatic biasing. We show that the perfect absorption can be realized at different Fermi energies for TM waves.

  16. PERFECTLY MATCHED LAYERS FOR ELASTIC WAVES IN CYLINDRICAL AND SPHERICAL COORDINATES. (R825225)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  17. Artificial perfect electric conductor-perfect magnetic conductor anisotropic metasurface for generating orbital angular momentum of microwave with nearly perfect conversion efficiency

    NASA Astrophysics Data System (ADS)

    Chen, Menglin L. N.; Jiang, Li Jun; Sha, Wei E. I.

    2016-02-01

    Orbital angular momentum (OAM) is a promising degree of freedom for fundamental studies in electromagnetics and quantum mechanics. The unlimited state space of OAM shows a great potential to enhance channel capacities of classical and quantum communications. By exploring the Pancharatnam-Berry phase concept and engineering anisotropic scatterers in a metasurface with spatially varying orientations, a plane wave with zero OAM can be converted to a vortex beam carrying nonzero OAM. In this paper, we proposed two types of novel perfect electric conductor-perfect magnetic conductor anisotropic metasurfaces. One is composed of azimuthally continuous loops and the other is constructed by azimuthally discontinuous dipole scatterers. Both types of metasurfaces are mounted on a mushroom-type high impedance surface. Compared to previous metasurface designs for generating OAM, the proposed ones achieve nearly perfect conversion efficiency. In view of the eliminated vertical component of electric field, the continuous metasurface shows very smooth phase pattern at the near-field region, which cannot be achieved by convectional metasurfaces composed of discrete scatterers. On the other hand, the metasurface with discrete dipole scatterers shows a great flexibility to generate OAM with arbitrary topological charges. Our work is fundamentally and practically important to high-performance OAM generation.

  18. Cosmological and spherically symmetric solutions with intersecting p-branes

    NASA Astrophysics Data System (ADS)

    Ivashchuk, V. D.; Melnikov, V. N.

    1999-12-01

    Multidimensional model describing the cosmological evolution and/or spherically symmetric configuration with n+1 Einstein spaces in the theory with several scalar fields and forms is considered. When electro-magnetic composite p-brane ansatz is adopted, n ``internal'' spaces are Ricci-flat, one space M0 has a nonzero curvature, and all p-branes do not ``live'' in M0, a class of exact solutions is obtained if certain block-orthogonality relations on p-brane vectors are imposed. A subclass of spherically symmetric solutions (containing nonextremal p-brane black holes) is considered. Post-Newtonian parameters are calculated.

  19. Comparison of large aperture telescopes with parabolic and spherical primaries

    NASA Technical Reports Server (NTRS)

    Korsch, D.

    1986-01-01

    Quasi-Cassegrain-type four-mirror telescopes are compared to conventional two-mirror Cassegrain telescopes for use as high performance, very large aperture space telescopes. Spherical and parabolic primaries with continuous as well as segmented surfaces are considered. Imaging characteristics and misalignment sensitivities serve as the principal criteria of comparison. The evaluation shows that parabolic primaries yield superior wide-field performance, whereas spherical primaries hold distinct advantages regarding manufacturability and regarding certain alignment aspects in the case of segmentation.

  20. Random perfect lattices and the sphere packing problem

    NASA Astrophysics Data System (ADS)

    Andreanov, A.; Scardicchio, A.

    2012-10-01

    Motivated by the search for best lattice sphere packings in Euclidean spaces of large dimensions we study randomly generated perfect lattices in moderately large dimensions (up to d=19 included). Perfect lattices are relevant in the solution of the problem of lattice sphere packing, because the best lattice packing is a perfect lattice and because they can be generated easily. Their number, however, grows superexponentially with the dimension, so to get an idea of their properties we propose to study a randomized version of the generating algorithm and to define a random ensemble with an effective temperature in a way reminiscent of a Monte Carlo simulation. We therefore study the distribution of packing fractions and kissing numbers of these ensembles and show how as the temperature is decreased the best known packers are easily recovered. We find that, even at infinite temperature, the typical perfect lattices are considerably denser than known families (like Ad and Dd), and we propose two hypotheses between which we cannot distinguish in this paper: one in which they improve the Minkowsky bound φ˜2-(0.84±0.06)d, and a competitor in which their packing fraction decreases superexponentially, namely, φ˜d-ad but with a very small coefficient a=0.06±0.04. We also find properties of the random walk which are suggestive of a glassy system already for moderately small dimensions. We also analyze local structure of network of perfect lattices conjecturing that this is a scale-free network in all dimensions with constant scaling exponent 2.6±0.1.

  1. Random perfect lattices and the sphere packing problem.

    PubMed

    Andreanov, A; Scardicchio, A

    2012-10-01

    Motivated by the search for best lattice sphere packings in Euclidean spaces of large dimensions we study randomly generated perfect lattices in moderately large dimensions (up to d=19 included). Perfect lattices are relevant in the solution of the problem of lattice sphere packing, because the best lattice packing is a perfect lattice and because they can be generated easily. Their number, however, grows superexponentially with the dimension, so to get an idea of their properties we propose to study a randomized version of the generating algorithm and to define a random ensemble with an effective temperature in a way reminiscent of a Monte Carlo simulation. We therefore study the distribution of packing fractions and kissing numbers of these ensembles and show how as the temperature is decreased the best known packers are easily recovered. We find that, even at infinite temperature, the typical perfect lattices are considerably denser than known families (like A(d) and D(d)), and we propose two hypotheses between which we cannot distinguish in this paper: one in which they improve the Minkowsky bound φ~2(-(0.84±0.06)d), and a competitor in which their packing fraction decreases superexponentially, namely, φ~d(-ad) but with a very small coefficient a=0.06±0.04. We also find properties of the random walk which are suggestive of a glassy system already for moderately small dimensions. We also analyze local structure of network of perfect lattices conjecturing that this is a scale-free network in all dimensions with constant scaling exponent 2.6±0.1.

  2. A perfect launch on a perfect Florida day!

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Trailing a column of flame and smoke that dwarfs it, Space Shuttle Endeavour leaps into the clear blue Florida sky on mission STS-99. Liftoff occurred at 12:43:40 p.m. EST. Known as the Shuttle Radar Topography Mission (SRTM), STS-99 will chart a new course to produce unrivaled 3-D images of the Earth's surface. The result of the SRTM could be close to 1 trillion measurements of the Earth's topography. The mission is expected to last 11days, with Endeavour landing at KSC Tuesday, Feb. 22, at 4:36 p.m. EST. This is the 97th Shuttle flight and 14th for Shuttle Endeavour.

  3. Computation of Thermally Perfect Compressible Flow Properties

    NASA Technical Reports Server (NTRS)

    Witte, David W.; Tatum, Kenneth E.; Williams, S. Blake

    1996-01-01

    A set of compressible flow relations for a thermally perfect, calorically imperfect gas are derived for a value of c(sub p) (specific heat at constant pressure) expressed as a polynomial function of temperature and developed into a computer program, referred to as the Thermally Perfect Gas (TPG) code. The code is available free from the NASA Langley Software Server at URL http://www.larc.nasa.gov/LSS. The code produces tables of compressible flow properties similar to those found in NACA Report 1135. Unlike the NACA Report 1135 tables which are valid only in the calorically perfect temperature regime the TPG code results are also valid in the thermally perfect, calorically imperfect temperature regime, giving the TPG code a considerably larger range of temperature application. Accuracy of the TPG code in the calorically perfect and in the thermally perfect, calorically imperfect temperature regimes are verified by comparisons with the methods of NACA Report 1135. The advantages of the TPG code compared to the thermally perfect, calorically imperfect method of NACA Report 1135 are its applicability to any type of gas (monatomic, diatomic, triatomic, or polyatomic) or any specified mixture of gases, ease-of-use, and tabulated results.

  4. Optical design study for NASA's spherical primary optical telescope (SPOT)

    NASA Astrophysics Data System (ADS)

    Howard, Joseph M.

    2004-10-01

    Several of NASA's future space telescopes project teams have chosen or are considering segmented primary mirrors as a part of their architecture. The James Webb Space Telescope (JWST) design employs a 6.5-meter conic primary mirror constructed of 18 hexagonal segments, where each hex is one of three off-axis surface profiles corresponding to its radial distance to the parent mirror axis. Other future mission concepts such as SAFIR (Single Aperture Far-Infra Red) and SUVO (Space Ultra Violet Optical telescope) are considering even larger segmented primary mirrors. The goal of the Spherical Primary Optical Telescope (SPOT) project discussed in this paper is to investigate the option of a spherical primary mirror for such future large aperture NASA missions. Ground-based telescopes such as the Hobby-Eberly have realized this design option, and the current baseline design for ESO's OWL project incorporates a 100-meter segmented spherical primary mirror. While the benefits of fabricating large numbers of identical spherical surface segments are obvious, the optical design for the telescope becomes more complex in order to correct the significant aberration resulting from a spherical primary surface. This paper briefly surveys design approaches of spherical primary telescopes. Image based performance comparisons are made, and examples are presented.

  5. QED with a spherical mirror

    SciTech Connect

    Hetet, G.; Blatt, R.; Slodicka, L.; Hennrich, M.; Glaetzle, A.

    2010-12-15

    We investigate the quantum electrodynamic (QED) properties of an atomic electron close to the focus of a spherical mirror. We first show that the spontaneous emission and excited-state level shift of the atom can be fully suppressed with mirror-atom distances of many wavelengths. A three-dimensional theory predicts that the spectral density of vacuum fluctuations can indeed vanish within a volume {lambda}{sup 3} around the atom, with the use of a far-distant mirror covering only half of the atomic emission solid angle. The modification of these QED atomic properties is also computed as a function of the mirror size, and large effects are found for only moderate numerical apertures. We also evaluate the long-distance ground-state energy shift (Casimir-Polder shift) and find that it scales as ({lambda}/R){sup 2} at the focus of a hemispherical mirror of radius R, as opposed to the well-known ({lambda}/R){sup 4} scaling law for an atom at a distance R from an infinite plane mirror. Our results are relevant for investigations of QED effects as well as free-space coupling to single atoms using high-numerical-aperture lenses.

  6. Quality metric for spherical panoramic video

    NASA Astrophysics Data System (ADS)

    Zakharchenko, Vladyslav; Choi, Kwang Pyo; Park, Jeong Hoon

    2016-09-01

    Virtual reality (VR)/ augmented reality (AR) applications allow users to view artificial content of a surrounding space simulating presence effect with a help of special applications or devices. Synthetic contents production is well known process form computer graphics domain and pipeline has been already fixed in the industry. However emerging multimedia formats for immersive entertainment applications such as free-viewpoint television (FTV) or spherical panoramic video require different approaches in content management and quality assessment. The international standardization on FTV has been promoted by MPEG. This paper is dedicated to discussion of immersive media distribution format and quality estimation process. Accuracy and reliability of the proposed objective quality estimation method had been verified with spherical panoramic images demonstrating good correlation results with subjective quality estimation held by a group of experts.

  7. Perfect commuting-operator strategies for linear system games

    NASA Astrophysics Data System (ADS)

    Cleve, Richard; Liu, Li; Slofstra, William

    2017-01-01

    Linear system games are a generalization of Mermin's magic square game introduced by Cleve and Mittal. They show that perfect strategies for linear system games in the tensor-product model of entanglement correspond to finite-dimensional operator solutions of a certain set of non-commutative equations. We investigate linear system games in the commuting-operator model of entanglement, where Alice and Bob's measurement operators act on a joint Hilbert space, and Alice's operators must commute with Bob's operators. We show that perfect strategies in this model correspond to possibly infinite-dimensional operator solutions of the non-commutative equations. The proof is based around a finitely presented group associated with the linear system which arises from the non-commutative equations.

  8. Applying Gradient Expansion to a Perfect Fluid and Higher Dimensions

    NASA Astrophysics Data System (ADS)

    Chiba, Takeshi

    1996-09-01

    We examine the nonlinear evolution of two types of spacetime by solving the Hamilton-Jacobi equation by the gradient expansion method to investigate the validity and limitation of the method itself. The first type is the nonlinear evolution of spacetime for an irrotational perfect fluid, and the second type is for an irrotational dust or an scalar field with an exponential potential inn-dimensional space. We find a recursion relation for the generating functional. Taking the comoving coordinate, the three-metric for perfect fluid is found up to the third order. The expression for the three-metric is in agreement with that of Comer et al. but the numerical coefficient is slightly different because of the different choice of coordinate condition. For a scalar field with an exponential potential in higher dimension, inhomogeneities decay during inflationary phase. The (n+1)-dimensional axisymmetric Szekeres solution is easily found as a byproduct.

  9. Double slotted socket spherical joint

    DOEpatents

    Bieg, Lothar F.; Benavides, Gilbert L.

    2001-05-22

    A new class of spherical joints is disclosed. These spherical joints are capable of extremely large angular displacements (full cone angles in excess of 270.degree.), while exhibiting no singularities or dead spots in their range of motion. These joints can improve or simplify a wide range of mechanical devices.

  10. Features of spherical torus plasmas

    SciTech Connect

    Peng, Y.K.M.; Strickler, D.J.

    1985-12-01

    The spherical torus is a very small aspect ratio (A < 2) confinement concept obtained by retaining only the indispensable components inboard to the plasma torus. MHD equilibrium calculations show that spherical torus plasmas with safety factor q > 2 are characterized by high toroidal beta (..beta../sub t/ > 0.2), low poloidal beta (..beta../sub p/ < 0.3), naturally large elongation (kappa greater than or equal to 2), large plasma current with I/sub p//(aB/sub t0/) up to about 7 MA/mT, strong paramagnetism (B/sub t//B/sub t0/ > 1.5), and strong plasma helicity (F comparable to THETA). A large near-omnigeneous region is seen at the large-major-radius, bad-curvature region of the plasma in comparison with the conventional tokamaks. These features combine to engender the spherical torus plasma in a unique physics regime which permits compact fusion at low field and modest cost. Because of its strong paramagnetism and helicity, the spherical torus plasma shares some of the desirable features of spheromak and reversed-field pinch (RFP) plasmas, but with tokamak-like confinement and safety factor q. The general class of spherical tori, which includes the spherical tokamak (q > 1), the spherical pinch (1 > q > O), and the spherical RFP (q < O), have magnetic field configurations unique in comparison with conventional tokamaks and RFPs. 22 refs., 12 figs.

  11. SPHERICAL SHOCK WAVES IN SOLIDS

    DTIC Science & Technology

    Contents: Introduction-Reasons for Studying Spherical Shock Waves, Physics of Cavity Expansion due to Explosive Impact, General Nature of Shock Waves...Governing Differential Equation of Self-Similar Motion; Application of the Theory of Self-Similar Motion to the Problem of Expansion of a Spherical

  12. Optimal mollifiers for spherical deconvolution

    NASA Astrophysics Data System (ADS)

    Hielscher, Ralf; Quellmalz, Michael

    2015-08-01

    This paper deals with the inversion of the spherical Funk-Radon transform, and, more generally, with the inversion of spherical convolution operators from the point of view of statistical inverse problems. This means we consider discrete data perturbed by white noise and aim at estimators with optimal mean square error for functions out of a Sobolev ball. To this end we analyze a specific class of estimators built upon the spherical hyperinterpolation operator, spherical designs and the mollifier approach. Eventually, we determine optimal mollifier functions with respect to the noise level, the number of data points and the smoothness of the original function. We complete this paper by providing a fast algorithm for the numerical computation of the estimator, which is based on the fast spherical Fourier transform, and by illustrating our theoretical results with numerical experiments.

  13. Consider a spherical cow

    SciTech Connect

    Harte, J.

    1985-01-01

    Consider a Spherical Cow describes relatively simple mathematical methods for developing quantitative answers to often complex environmental problems. Early chapters provide systematic insights into problem solving and identifying mathematical tools and models that lead to back of the envelope answers. Subsequent chapters treat increasingly complex problems. Solutions are sought at different levels, e.g., informed guesses, quantitative solutions based on detailed analytical models, and ultimately, critical evaluation of the consequences of removing simplifying assumptions from the models. The vehicle employed is a collection of 44 challenging problems, with clearly worked out solutions, plus ample exercises. The book, though directed at environmentalists, should appeal to chemists. Many of the problems are rooted in chemistry, including acid rain, the CO/sub 2/ greenhouse effect, chemical contamination, and the disturbing of cyclical chemical balances. Readers feeling a civic responsibility to think and speak more clearly on environmental issues will find the essential modeling and quantitative approaches valuable assets beyond the help provided by the usual courses in science and mathematics. In fact, the techniques of problem solving have broad applicability beyond the specific environmental examples covered in this text.

  14. Immunomodulatory spherical nucleic acids.

    PubMed

    Radovic-Moreno, Aleksandar F; Chernyak, Natalia; Mader, Christopher C; Nallagatla, Subbarao; Kang, Richard S; Hao, Liangliang; Walker, David A; Halo, Tiffany L; Merkel, Timothy J; Rische, Clayton H; Anantatmula, Sagar; Burkhart, Merideth; Mirkin, Chad A; Gryaznov, Sergei M

    2015-03-31

    Immunomodulatory nucleic acids have extraordinary promise for treating disease, yet clinical progress has been limited by a lack of tools to safely increase activity in patients. Immunomodulatory nucleic acids act by agonizing or antagonizing endosomal toll-like receptors (TLR3, TLR7/8, and TLR9), proteins involved in innate immune signaling. Immunomodulatory spherical nucleic acids (SNAs) that stimulate (immunostimulatory, IS-SNA) or regulate (immunoregulatory, IR-SNA) immunity by engaging TLRs have been designed, synthesized, and characterized. Compared with free oligonucleotides, IS-SNAs exhibit up to 80-fold increases in potency, 700-fold higher antibody titers, 400-fold higher cellular responses to a model antigen, and improved treatment of mice with lymphomas. IR-SNAs exhibit up to eightfold increases in potency and 30% greater reduction in fibrosis score in mice with nonalcoholic steatohepatitis (NASH). Given the clinical potential of SNAs due to their potency, defined chemical nature, and good tolerability, SNAs are attractive new modalities for developing immunotherapies.

  15. Immunomodulatory spherical nucleic acids

    PubMed Central

    Radovic-Moreno, Aleksandar F.; Chernyak, Natalia; Mader, Christopher C.; Nallagatla, Subbarao; Kang, Richard S.; Hao, Liangliang; Walker, David A.; Halo, Tiffany L.; Merkel, Timothy J.; Rische, Clayton H.; Anantatmula, Sagar; Burkhart, Merideth; Mirkin, Chad A.; Gryaznov, Sergei M.

    2015-01-01

    Immunomodulatory nucleic acids have extraordinary promise for treating disease, yet clinical progress has been limited by a lack of tools to safely increase activity in patients. Immunomodulatory nucleic acids act by agonizing or antagonizing endosomal toll-like receptors (TLR3, TLR7/8, and TLR9), proteins involved in innate immune signaling. Immunomodulatory spherical nucleic acids (SNAs) that stimulate (immunostimulatory, IS-SNA) or regulate (immunoregulatory, IR-SNA) immunity by engaging TLRs have been designed, synthesized, and characterized. Compared with free oligonucleotides, IS-SNAs exhibit up to 80-fold increases in potency, 700-fold higher antibody titers, 400-fold higher cellular responses to a model antigen, and improved treatment of mice with lymphomas. IR-SNAs exhibit up to eightfold increases in potency and 30% greater reduction in fibrosis score in mice with nonalcoholic steatohepatitis (NASH). Given the clinical potential of SNAs due to their potency, defined chemical nature, and good tolerability, SNAs are attractive new modalities for developing immunotherapies. PMID:25775582

  16. A spherical electrostatic orrery

    NASA Astrophysics Data System (ADS)

    Smetana, Carole; Alexander, David; Robertson, Scott; Vilkaitis, Kim; Walch, Bob

    1996-11-01

    An electrostatic orrery for studying Keplerian orbits has been constructed in which one or more negatively charged hollow glass microparticles orbit a 9.5-mm-diam metal sphere at +8-kV potential in a vacuum. The device is similar to an earlier cylindrical orrery in which particles orbit a rod [Biewer et al., Am. J. Phys. 62(9), 821-827 (1994)]. Electrically biased cylinders covering the rod supporting the sphere give nearly spherical potential surfaces inside the trap. Additional electrodes at the boundary are used to reduce the perturbation of gravity and to prevent motion resulting in collisions with the supporting rod. Orbits last approximately 10 min or about 104 revolutions. The orbiters are illuminated with a slide projector and can be seen with the naked eye as well as videotaped. The trap has been used to observe orbital precession, interparticle collisions, and the effects of time-independent perturbations. This apparatus provides an opportunity for the study and demonstration of orbital motion in a laboratory.

  17. Conditions for creating perfectly secure systems

    NASA Astrophysics Data System (ADS)

    Styugin, M.

    2016-11-01

    The present paper reviews a method for establishing secure information systems by complicating the possibility to research them for potential adversaries. A formalized model of a researcher and a definition of a research secure system are presented. A theorem for conditions required for creating a system perfectly secured from research. The Shannon's theorem of absolute security of perfect secrecy ciphers in cryptography is an instance of the theorem presented in the paper.

  18. Improved and perfect actions in discrete gravity

    SciTech Connect

    Bahr, Benjamin; Dittrich, Bianca

    2009-12-15

    We consider the notion of improved and perfect actions within Regge calculus. These actions are constructed in such a way that they - although being defined on a triangulation - reproduce the continuum dynamics exactly, and therefore capture the gauge symmetries of general relativity. We construct the perfect action in three dimensions with a cosmological constant, and in four dimensions for one simplex. We conclude with a discussion about Regge calculus with curved simplices, which arises naturally in this context.

  19. Labeling spherically symmetric spacetimes with the Ricci tensor

    NASA Astrophysics Data System (ADS)

    Ferrando, Joan Josep; Sáez, Juan Antonio

    2017-02-01

    We complete the intrinsic characterization of spherically symmetric solutions partially accomplished in a previous paper (Ferrando and Sáez 2010 Class. Quantum Grav. 27 205024). In this approach we consider every compatible algebraic type of the Ricci tensor, and we analyze specifically the conformally flat case for perfect fluid and Einstein–Maxwell solutions. As a direct application we obtain the ideal labeling (exclusively involving explicit concomitants of the metric tensor) of the Schwarzschild interior metric and the Vaidya solution. The Stephani universes and some significative subfamilies are also characterized.

  20. Persistent Perfect Entanglement in Atomic Systems

    NASA Astrophysics Data System (ADS)

    Ali Can, Muhammet

    2004-03-01

    It has been shown recently [1] that a pure entangled state of two-level atoms can be obtained in an optical resonator through the exchange by cavity photons. Unfortunately, the lifetime of such an entangled state, caused by the radiative decay time for the dipole transitions is very short. The situation can be improved through the use of three-level atoms with lambda-type transition [2]. In this case, the cavity field pumps transition between the lowest (ground) and highest (excited) states. Then, the decay of the excited state can populate the intermediate state. This is just the Raman-type process with emission of Stokes photon in atomic system. Because of the selection rules by the parity conservation, the dipole decay from the intermediate state to the ground state is forbidden. If the Stokes photons created by the transitions from the excited state to the ground state are discarded (through the use of cavity leakage of absorption), the final state of atomic system is stabile or at least durable. In the case of 2n three-level atoms, this can lead to the N-qubit perfect entangled state, where N=2j+1 and j is an odd ``spin'' corresponding to the SU(2) algebra in the Hilbert space H=(C2)^ otimes N In fact, these are the SU(2) phase states of odd ``spin'' have been discussed in [3] in the context of two-level atoms. The possibility to create and observe these states with present experimental technique is discussed. [1] A. Beige, S. Bose, D. Braun, S.F. Huelga, P.L. Knight, M.B. Plenio, and V. Verdal. J. Mod. Optics 47, 2583 (2000). [2] M.A. Can, A.A. Klyachko, and A.S. Shumovsky. Appl. Phys. Lett. 81, 5072 (2002). [3] M.A. Can, A.A. Klyachko, and A.S. Shumovsky. Phys. Rev. A 66, 022111 (2002).

  1. Directional decomposition of the acoustic wave equation for fluids and metafluids in spherical geometries, with application to transformational acoustics

    NASA Astrophysics Data System (ADS)

    Olsson, Peter

    2016-03-01

    A new directional decomposition of the acoustic 3D wave equation is derived for spherically symmetric geometries, where the wave fields do not need to possess such a symmetry. This provides an alternative basis for various applications of techniques like invariant embedding and time domain Green functions in spherically symmetric geometries. Contrary to previous results on spherical wave splittings, the new decomposition is given in a very explicit form. The wave equation considered incorporates effects from radially varying compressibility and density, but also from anisotropic density, a property of certain so called metafluids. By applying the new spherical wave splitting, we show that all spherically symmetric acoustic metafluid cloaks are diffeomorphic images of a homogeneous and isotropic spherical ball of perfect fluid.

  2. Cost-effective description of strong correlation: Efficient implementations of the perfect quadruples and perfect hextuples models.

    PubMed

    Lehtola, Susi; Parkhill, John; Head-Gordon, Martin

    2016-10-07

    Novel implementations based on dense tensor storage are presented for the singlet-reference perfect quadruples (PQ) [J. A. Parkhill et al., J. Chem. Phys. 130, 084101 (2009)] and perfect hextuples (PH) [J. A. Parkhill and M. Head-Gordon, J. Chem. Phys. 133, 024103 (2010)] models. The methods are obtained as block decompositions of conventional coupled-cluster theory that are exact for four electrons in four orbitals (PQ) and six electrons in six orbitals (PH), but that can also be applied to much larger systems. PQ and PH have storage requirements that scale as the square, and as the cube of the number of active electrons, respectively, and exhibit quartic scaling of the computational effort for large systems. Applications of the new implementations are presented for full-valence calculations on linear polyenes (CnHn+2), which highlight the excellent computational scaling of the present implementations that can routinely handle active spaces of hundreds of electrons. The accuracy of the models is studied in the π space of the polyenes, in hydrogen chains (H50), and in the π space of polyacene molecules. In all cases, the results compare favorably to density matrix renormalization group values. With the novel implementation of PQ, active spaces of 140 electrons in 140 orbitals can be solved in a matter of minutes on a single core workstation, and the relatively low polynomial scaling means that very large systems are also accessible using parallel computing.

  3. Cost-effective description of strong correlation: Efficient implementations of the perfect quadruples and perfect hextuples models

    NASA Astrophysics Data System (ADS)

    Lehtola, Susi; Parkhill, John; Head-Gordon, Martin

    2016-10-01

    Novel implementations based on dense tensor storage are presented for the singlet-reference perfect quadruples (PQ) [J. A. Parkhill et al., J. Chem. Phys. 130, 084101 (2009)] and perfect hextuples (PH) [J. A. Parkhill and M. Head-Gordon, J. Chem. Phys. 133, 024103 (2010)] models. The methods are obtained as block decompositions of conventional coupled-cluster theory that are exact for four electrons in four orbitals (PQ) and six electrons in six orbitals (PH), but that can also be applied to much larger systems. PQ and PH have storage requirements that scale as the square, and as the cube of the number of active electrons, respectively, and exhibit quartic scaling of the computational effort for large systems. Applications of the new implementations are presented for full-valence calculations on linear polyenes (CnHn+2), which highlight the excellent computational scaling of the present implementations that can routinely handle active spaces of hundreds of electrons. The accuracy of the models is studied in the π space of the polyenes, in hydrogen chains (H50), and in the π space of polyacene molecules. In all cases, the results compare favorably to density matrix renormalization group values. With the novel implementation of PQ, active spaces of 140 electrons in 140 orbitals can be solved in a matter of minutes on a single core workstation, and the relatively low polynomial scaling means that very large systems are also accessible using parallel computing.

  4. Evaluating Descent and Ascent Trajectories Near Non-Spherical Bodies

    NASA Technical Reports Server (NTRS)

    Werner, Robert A.

    2010-01-01

    Spacecraft landing on small bodies pass through regions where conventional gravitation formulations using exterior spherical harmonics are inaccurate. An investigation shows that a formulation using interior solid spherical harmonics might be satisfactory. Interior spherical harmonic expansions are usable inside an imaginary, empty sphere. For this application, such a sphere could be positioned in empty space above the intended landing site and rotating with the body. When the spacecraft is inside this sphere, the interior harmonic expansion would be used instead of the conventional, exterior harmonic expansion. Coefficients can be determined by a least-squares fit to gravitation measurements synthesized from conventional formulations. Due to their unfamiliarity, recurrences for interior, as well as exterior, expansions are derived. Hotine's technique for partial derivatives of exterior spherical harmonics is extended to interior harmonics.

  5. Spherical Panoramas for Astrophysical Data Visualization

    NASA Astrophysics Data System (ADS)

    Kent, Brian R.

    2017-05-01

    Data immersion has advantages in astrophysical visualization. Complex multi-dimensional data and phase spaces can be explored in a seamless and interactive viewing environment. Putting the user in the data is a first step toward immersive data analysis. We present a technique for creating 360° spherical panoramas with astrophysical data. The three-dimensional software package Blender and the Google Spatial Media module are used together to immerse users in data exploration. Several examples employing these methods exhibit how the technique works using different types of astronomical data.

  6. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Looking like a lighted taper against a cloud-streaked sky, Space Shuttle Atlantis belches a column of smoke as it blasts into space. In the foreground are patches of water and marsh between the Mosquito Lagoon on the north and Banana Creek on the south. In the background is the Atlantic Ocean. The perfect on-time liftoff of Atlantis occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbe d is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  7. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Bare branches frame the liftoff of Space Shuttle Atlantis on mission STS-106 to the International Space Station. Billows of smoke and steam are illuminated by the flames of the solid rocket boosters. The perfect on-time liftoff of Atlantis occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbe d is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  8. Directional Spherical Cherenkov Detector

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.; Wrbanek, Susan Y.

    2010-01-01

    A proposed radiation-detecting apparatus would provide information on the kinetic energies, directions, and electric charges of highly energetic incident subatomic particles. The apparatus was originally intended for use in measuring properties of cosmic rays in outer space, but could also be adapted to terrestrial uses -- for example, radiation dosimetry aboard high-altitude aircraft and in proton radiation therapy for treatment of tumors.

  9. A near-perfect invisibility cloak constructed with homogeneous materials.

    PubMed

    Li, Wei; Guan, Jianguo; Sun, Zhigang; Wang, Wei; Zhang, Qingjie

    2009-12-21

    A near-perfect, non-singular cylindrical invisibility cloak with diamond cross section is achieved by a two-step coordinate transformation. A small line segment is stretched and then blown up into a diamond space, and finally the cloak consisting of four kinds and eight blocks of homogeneous transformation media is obtained. Numerical simulations confirm the well performance of the cloak. The operation bandwidth of the cloak is also investigated. Our scheme is promising to create a simple and well-performed cloak in practice.

  10. On the perfectly matched layer and the DB boundary condition.

    PubMed

    Tedeschi, Nicola; Frezza, Fabrizio; Sihvola, Ari

    2013-10-01

    In this paper, we consider a particular uniaxial material able to achieve the DB boundary condition. We show how, for particular transverse electromagnetic properties, this material behaves like a perfectly matched layer (PML). Moreover, we find that, with an approximation, the material becomes passive, i.e., loses the active part of the permittivity and of the permeability typical of a PML. In this case, the uniaxial medium becomes realizable as a particular absorbing metamaterial. We present simulations with both guided and free-space waves to show the absorbing behavior of the proposed material.

  11. Proper projective symmetry in the most general non-static spherically symmetric four-dimensional Lorentzian manifolds

    NASA Astrophysics Data System (ADS)

    Shabbir, Ghulam; Mahomed, F. M.; Qureshi, M. A.

    2016-11-01

    A study of proper projective symmetry in the most general form of non-static spherically symmetric space-time is given using direct integration and algebraic techniques. In this study, we show that when the above space-time admits proper projective symmetry it becomes a very special class of static spherically symmetric space-times.

  12. Caustics for spherical waves

    NASA Astrophysics Data System (ADS)

    de Rham, Claudia; Motohashi, Hayato

    2017-03-01

    We study the development of caustics in shift-symmetric scalar field theories by focusing on simple waves with an S O (p )-symmetry in an arbitrary number of space dimensions. We show that the pure Galileon, the DBI-Galileon, and the extreme-relativistic Galileon naturally emerge as the unique set of caustic-free theories, highlighting a link between the caustic-free condition for simple S O (p )-waves and the existence of either a global Galilean symmetry or a global (extreme-)relativistic Galilean symmetry.

  13. Maximum mass of a barotropic spherical star

    NASA Astrophysics Data System (ADS)

    Fujisawa, Atsuhito; Saida, Hiromi; Yoo, Chul-Moon; Nambu, Yasusada

    2015-11-01

    The ratio of total mass {m}* to the surface radius {r}* of a spherical perfect fluid ball has an upper bound, {{Gm}}*/({c}2{r}*)≤slant {B}. Buchdahl (1959 Phys. Rev. 116 1027) obtained the value {{B}}{{Buch}}=4/9 under the assumptions that the object has a nonincreasing mass density in the outward direction and a barotropic equation of state. Barraco and Hamity (2002 Phys. Rev. D 65 124028) decreased Buchdahl's bound to a lower value, {{B}}{{BaHa}} = 3/8 (<4/9), by adding the dominant energy condition to Buchdahl's assumptions. In this paper, we further decrease Barraco-Hamity's bound to {{B}}{{new}}≃ 0.3636403 (<3/8) by adding the subluminal (slower than light) condition of sound speed. In our analysis we numerically solve the Tolman-Oppenheimer-Volkoff equations, and the mass-to-radius ratio is maximized by variation of mass, radius and pressure inside the fluid ball as functions of mass density.

  14. Relativistic perfect fluids in local thermal equilibrium

    NASA Astrophysics Data System (ADS)

    Coll, Bartolomé; Ferrando, Joan Josep; Sáez, Juan Antonio

    2017-05-01

    Every evolution of a fluid is uniquely described by an energy tensor. But the converse is not true: an energy tensor may describe the evolution of different fluids. The problem of determining them is called here the inverse problem. This problem may admit unphysical or non-deterministic solutions. This paper is devoted to solve the inverse problem for perfect energy tensors in the class of perfect fluids evolving in local thermal equilibrium (l.t.e.). The starting point is a previous result (Coll and Ferrando in J Math Phys 30:2918-2922, 1989) showing that thermodynamic fluids evolving in l.t.e. admit a purely hydrodynamic characterization. This characterization allows solving this inverse problem in a very compact form. The paradigmatic case of perfect energy tensors representing the evolution of ideal gases is studied in detail and some applications and examples are outlined.

  15. Overlapped optics induced perfect coherent effects

    NASA Astrophysics Data System (ADS)

    Li, Jian Jie; Zang, Xiao Fei; Mao, Jun Fa; Tang, Min; Zhu, Yi Ming; Zhuang, Song Lin

    2013-12-01

    For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.

  16. [THE RIGHT TO A CHROMOSOMICALLY PERFECT CHILD].

    PubMed

    Vago, Philippe

    2015-07-01

    After defining the terms "perfect," "chromosomically" and "right" we discuss on the scope and terms of the right to a chromosomically perfect child. This right is it addressed to a target population or to the general population? What are the exams available and the means of diagnosis or screening to be implemented? The practice of genetic testing being highly controlled, some rules are then discussed. All over the paper, a reflection is proposed on what is allowed versus what is possible with reference to ethics.

  17. Selective coherent perfect absorption in metamaterials

    SciTech Connect

    Nie, Guangyu; Shi, Quanchao; Zhu, Zheng; Shi, Jinhui

    2014-11-17

    We show multi-band coherent perfect absorption (CPA) in simple bilayered asymmetrically split ring metamaterials. The selectivity of absorption can be accomplished by separately excited electric and magnetic modes in a standing wave formed by two coherent counterpropagating beams. In particular, each CPA can be completely switched on/off by the phase of a second coherent wave. We propose a practical scheme for realizing multi-band coherent perfect absorption of 100% that is allowed to work from microwave to optical frequency.

  18. Generation of perfect vectorial vortex beams.

    PubMed

    Li, Peng; Zhang, Yi; Liu, Sheng; Ma, Chaojie; Han, Lei; Cheng, Huachao; Zhao, Jianlin

    2016-05-15

    We propose the concept of perfect vectorial vortex beams (VVBs), which not merely have intensity profile independent of the polarization order and the topological charge of spiral phase, but also have stable intensity profile and state of polarization (SoP) upon propagation. Utilizing a Sagnac interferometer, we approximately generate perfect VVBs with locally linear and elliptical polarizations, and demonstrate that such beams can keep their intensity profile and SoP at a certain propagation distance. These proposed VVBs can be expanded to encode information and quantum cryptography, as well as to enrich the conversion of spin and orbital angular momenta.

  19. Spherical primary optical telescope (SPOT) segments

    NASA Astrophysics Data System (ADS)

    Hall, Christopher; Hagopian, John; DeMarco, Michael

    2012-09-01

    The spherical primary optical telescope (SPOT) project is an internal research and development program at NASA Goddard Space Flight Center. The goals of the program are to develop a robust and cost effective way to manufacture spherical mirror segments and demonstrate a new wavefront sensing approach for continuous phasing across the segmented primary. This paper focuses on the fabrication of the mirror segments. Significant cost savings were achieved through the design, since it allowed the mirror segments to be cast rather than machined from a glass blank. Casting was followed by conventional figuring at Goddard Space Flight Center. After polishing, the mirror segments were mounted to their composite assemblies. QED Technologies used magnetorheological finishing (MRF®) for the final figuring. The MRF process polished the mirrors while they were mounted to their composite assemblies. Each assembly included several magnetic invar plugs that extended to within an inch of the face of the mirror. As part of this project, the interaction between the MRF magnetic field and invar plugs was evaluated. By properly selecting the polishing conditions, MRF was able to significantly improve the figure of the mounted segments. The final MRF figuring demonstrates that mirrors, in the mounted configuration, can be polished and tested to specification. There are significant process capability advantes due to polishing and testing the optics in their final, end-use assembled state.

  20. Spherically symmetric conformal gravity and ``gravitational bubbles''

    NASA Astrophysics Data System (ADS)

    Berezin, V. A.; Dokuchaev, V. I.; Eroshenko, Yu. N.

    2016-01-01

    The general structure of the spherically symmetric solutions in the Weyl conformal gravity is described. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions is found. It consists of two classes. The first one contains the solutions with constant two-dimensional curvature scalar of our specific metrics, and the representatives are the famous Robertson-Walker metrics. One of them we called the ``gravitational bubbles'', which is compact and with zero Weyl tensor. Thus, we obtained the pure vacuum curved space-times (without any material sources, including the cosmological constant) what is absolutely impossible in General Relativity. Such a phenomenon makes it easier to create the universe from ``nothing''. The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family. It appears that it can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We also investigated the general structure of the energy-momentum tensor in the spherical conformal gravity and constructed the vectorial equation that reveals clearly some features of non-vacuum solutions. Two of them are explicitly written, namely, the metrics à la Vaidya, and the electrovacuum space-time metrics.

  1. Spherically symmetric conformal gravity and ''gravitational bubbles''

    SciTech Connect

    Berezin, V.A.; Dokuchaev, V.I.; Eroshenko, Yu.N. E-mail: dokuchaev@inr.ac.ru

    2016-01-01

    The general structure of the spherically symmetric solutions in the Weyl conformal gravity is described. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions is found. It consists of two classes. The first one contains the solutions with constant two-dimensional curvature scalar of our specific metrics, and the representatives are the famous Robertson-Walker metrics. One of them we called the ''gravitational bubbles'', which is compact and with zero Weyl tensor. Thus, we obtained the pure vacuum curved space-times (without any material sources, including the cosmological constant) what is absolutely impossible in General Relativity. Such a phenomenon makes it easier to create the universe from ''nothing''. The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family. It appears that it can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We also investigated the general structure of the energy-momentum tensor in the spherical conformal gravity and constructed the vectorial equation that reveals clearly some features of non-vacuum solutions. Two of them are explicitly written, namely, the metrics à la Vaidya, and the electrovacuum space-time metrics.

  2. Gravity inversion in spherical coordinates using tesseroids

    NASA Astrophysics Data System (ADS)

    Uieda, Leonardo; Barbosa, Valeria C. F.

    2014-05-01

    Satellite observations of the gravity field have provided geophysicists with exceptionally dense and uniform coverage of data over vast areas. This enables regional or global scale high resolution geophysical investigations. Techniques like forward modeling and inversion of gravity anomalies are routinely used to investigate large geologic structures, such as large igneous provinces, suture zones, intracratonic basins, and the Moho. Accurately modeling such large structures requires taking the sphericity of the Earth into account. A reasonable approximation is to assume a spherical Earth and use spherical coordinates. In recent years, efforts have been made to advance forward modeling in spherical coordinates using tesseroids, particularly with respect to speed and accuracy. Conversely, traditional space domain inverse modeling methods have not yet been adapted to use spherical coordinates and tesseroids. In the literature there are a range of inversion methods that have been developed for Cartesian coordinates and right rectangular prisms. These include methods for estimating the relief of an interface, like the Moho or the basement of a sedimentary basin. Another category includes methods to estimate the density distribution in a medium. The latter apply many algorithms to solve the inverse problem, ranging from analytic solutions to random search methods as well as systematic search methods. We present an adaptation for tesseroids of the systematic search method of "planting anomalous densities". This method can be used to estimate the geometry of geologic structures. As prior information, it requires knowledge of the approximate densities and positions of the structures. The main advantage of this method is its computational efficiency, requiring little computer memory and processing time. We demonstrate the shortcomings and capabilities of this approach using applications to synthetic and field data. Performing the inversion of gravity and gravity gradient

  3. Unsteady Spherical Diffusion Flames in Microgravity

    NASA Technical Reports Server (NTRS)

    Atreya, Arvind; Berhan, S.; Chernovsky, M.; Sacksteder, Kurt R.

    2001-01-01

    The absence of buoyancy-induced flows in microgravity (mu-g) and the resulting increase in the reactant residence time significantly alters the fundamentals of many combustion processes. Substantial differences between normal gravity (ng) and (mu-g) flames have been reported in experiments on candle flames, flame spread over solids, droplet combustion, and others. These differences are more basic than just in the visible flame shape. Longer residence times and higher concentration of combustion products in the flame zone create a thermochemical environment that changes the flame chemistry and the heat and mass transfer processes. Processes such as flame radiation, that are often ignored in ng, become very important and sometimes even controlling. Furthermore, microgravity conditions considerably enhance flame radiation by: (i) the build-up of combustion products in the high-temperature reaction zone which increases the gas radiation, and (ii) longer residence times make conditions appropriate for substantial amounts of soot to form which is also responsible for radiative heat loss. Thus, it is anticipated that radiative heat loss may eventually extinguish the "weak" (low burning rate per unit flame area) mu-g diffusion flame. Yet, space shuttle experiments on candle flames show that in an infinite ambient atmosphere, the hemispherical candle flame in mu-g will burn indefinitely. This may be because of the coupling between the fuel production rate and the flame via the heat-feedback mechanism for candle flames, flames over solids and fuel droplet flames. Thus, to focus only on the gas-phase phenomena leading to radiative extinction, aerodynamically stabilized gaseous diffusion flames are examined. This enables independent control of the fuel flow rate to help identify conditions under which radiative extinction occurs. Also, spherical geometry is chosen for the mu-g experiments and modeling because: (i) It reduces the complexity by making the problem one

  4. Casimir effect of the electromagnetic field in D-dimensional spherically symmetric cavities

    SciTech Connect

    Teo, L. P.

    2010-10-15

    Eigenmodes of the electromagnetic field with perfectly conducting or infinitely permeable conditions on the boundary of a D-dimensional spherically symmetric cavity is derived explicitly. It is shown that there are (D-2) polarizations for TE modes and one polarization for TM modes, giving rise to a total of (D-1) polarizations. In case of a D-dimensional ball, the eigenfrequencies of the electromagnetic field with perfectly conducting boundary condition coincides with the eigenfrequencies of gauge 1-forms with relative boundary condition; whereas the eigenfrequencies of the electromagnetic field with infinitely permeable boundary condition coincides with the eigenfrequencies of gauge 1-forms with absolute boundary condition. Casimir energies of single and concentric spherical shells in D-dimensions are computed. The Casimir energy of concentric spherical shells can be written as a sum of the single spherical shell contributions and an interacting term, and the latter is free of divergence. The interacting term always gives rise to an attractive force between the two spherical shells. Its leading term is the Casimir force acting between two parallel plates of the same area, as expected by proximity force approximation.

  5. A uniform geometrical theory of diffraction for an edge in a perfectly conducting surface

    NASA Technical Reports Server (NTRS)

    Kouyoumjian, R. G.; Pathak, P. H.

    1974-01-01

    A compact dyadic diffraction coefficient for electromagnetic waves obliquely incident on a curved edge formed by perfectly conducting curved or plane surfaces is obtained. This diffraction coefficient remains valid in the transition regions adjacent to shadow and reflection boundaries, where the diffraction coefficients of Keller's original theory fail. Our method is based on Keller's method of the canonical problem, which in this case is the perfectly conducting wedge illuminated by plane, cylindrical, conical, and spherical waves. When the proper ray-fixed coordinate system is introduced, the dyadic diffraction coefficient for the wedge is found to be the sum of only two dyads, and it is shown that this is also true for the dyadic diffraction coefficients of higher order edges. One dyad contains the acoustic soft diffraction coefficient; the other dyad contains the acoustic hard diffraction coefficient. The expressions for the acoustic wedge diffraction coefficients contain Fresnel integrals, which ensure that the total field is continuous at shadow and reflection boundaries.

  6. The Present Perfect in World Englishes

    ERIC Educational Resources Information Center

    Yao, Xinyue; Collins, Peter

    2012-01-01

    This paper reports on a comprehensive corpus-based study of regional and stylistic variation in the distribution of the English present perfect. The data represents ten English varieties of both the Inner Circle and Outer Circle, covering four major text types: conversation, news reportage, academic and fictional writing. The results are discussed…

  7. Perfect Phylogeny Problems with Missing Values.

    PubMed

    Kirkpatrick, Bonnie; Stevens, Kristian

    2014-01-01

    The perfect phylogeny problem is of central importance to both evolutionary biology and population genetics. Missing values are a common occurrence in both sequence and genotype data, but they make the problem of finding a perfect phylogeny NPhard even for binary characters. We introduce new and efficient perfect phylogeny algorithms for broad classes of binary and multistate data with missing values. Specifically, we address binary missing data consistent with the rich data hypothesis (RDH) introduced by Halperin and Karp and give an efficient algorithm for enumerating phylogenies. This algorithm is useful for computing the probability of data with missing values under the coalescent model. In addition, we use the partition intersection (PI) graph and chordal graph theory to generalize the RDH to multi-state characters with missing values. For a bounded number of states, we provide a fixed parameter tractable algorithm for the perfect phylogeny problem with missing data. Utilizing the PI graph, we are able to show that under multiple biologically motivated models for character data, our generalized RDH holds with high probability, and we evaluate our results with extensive empirical analysis.

  8. The Ambiguity of the English Present Perfect.

    ERIC Educational Resources Information Center

    Michaelis, Laura A.

    1994-01-01

    Examines grammatical and discourse-pragmatic reflexes of the existential and resultative readings of the English present perfect and presents negative and positive arguments regarding its ambiguity. It is suggested that the resultative verb represents a formal idiom and that mastery of aspectual grammar entails knowledge of form-meaning pairings.…

  9. Perfect Day: A Meditation about Teaching

    ERIC Educational Resources Information Center

    Valadez, Gilbert

    2004-01-01

    When asked by a student in a seminar recently if he could remember a perfect day teaching elementary school, the author writes memories of one he distinctly remembers because he gained new insight into teaching on that particular day. After returning to work following the devastating loss of a younger 19 year-old brother in a car crash, he resumed…

  10. Perfect Day: A Meditation about Teaching

    ERIC Educational Resources Information Center

    Valadez, Gilbert

    2004-01-01

    When asked by a student in a seminar recently if he could remember a perfect day teaching elementary school, the author writes memories of one he distinctly remembers because he gained new insight into teaching on that particular day. After returning to work following the devastating loss of a younger 19 year-old brother in a car crash, he resumed…

  11. Maple Explorations, Perfect Numbers, and Mersenne Primes

    ERIC Educational Resources Information Center

    Ghusayni, B.

    2005-01-01

    Some examples from different areas of mathematics are explored to give a working knowledge of the computer algebra system Maple. Perfect numbers and Mersenne primes, which have fascinated people for a very long time and continue to do so, are studied using Maple and some questions are posed that still await answers.

  12. The Ambiguity of the English Present Perfect.

    ERIC Educational Resources Information Center

    Michaelis, Laura A.

    1994-01-01

    Examines grammatical and discourse-pragmatic reflexes of the existential and resultative readings of the English present perfect and presents negative and positive arguments regarding its ambiguity. It is suggested that the resultative verb represents a formal idiom and that mastery of aspectual grammar entails knowledge of form-meaning pairings.…

  13. Mechanical Energy Changes in Perfectly Inelastic Collisions

    ERIC Educational Resources Information Center

    Mungan, Carl E.

    2013-01-01

    Suppose a block of mass "m"[subscript 1] traveling at speed "v"[subscript 1] makes a one-dimensional perfectly inelastic collision with another block of mass "m"[subscript 2]. What else does one need to know to calculate the fraction of the mechanical energy that is dissipated in the collision? (Contains 1 figure.)

  14. The Present Perfect in World Englishes

    ERIC Educational Resources Information Center

    Yao, Xinyue; Collins, Peter

    2012-01-01

    This paper reports on a comprehensive corpus-based study of regional and stylistic variation in the distribution of the English present perfect. The data represents ten English varieties of both the Inner Circle and Outer Circle, covering four major text types: conversation, news reportage, academic and fictional writing. The results are discussed…

  15. Designing a perfect cornea: computational aspects

    NASA Astrophysics Data System (ADS)

    Rubinstein, Jacob; Wolansky, Gershon

    2002-12-01

    We analyze an algorithm for the design of a perfect cornea that exactly focuses a preselected object or a preselected wave front on the retina. The algorithm can be used, for example, in refractive surgery. We consider the sensitivity of the algorithm to various errors, including errors in the measurements of the aberrations, the original corneal topography and the ablation process.

  16. Maple Explorations, Perfect Numbers, and Mersenne Primes

    ERIC Educational Resources Information Center

    Ghusayni, B.

    2005-01-01

    Some examples from different areas of mathematics are explored to give a working knowledge of the computer algebra system Maple. Perfect numbers and Mersenne primes, which have fascinated people for a very long time and continue to do so, are studied using Maple and some questions are posed that still await answers.

  17. Mechanical Energy Changes in Perfectly Inelastic Collisions

    ERIC Educational Resources Information Center

    Mungan, Carl E.

    2013-01-01

    Suppose a block of mass "m"[subscript 1] traveling at speed "v"[subscript 1] makes a one-dimensional perfectly inelastic collision with another block of mass "m"[subscript 2]. What else does one need to know to calculate the fraction of the mechanical energy that is dissipated in the collision? (Contains 1 figure.)

  18. Spherical-wave expansions of piston-radiator fields.

    PubMed

    Wittmann, R C; Yaghjian, A D

    1991-09-01

    Simple spherical-wave expansions of the continuous-wave fields of a circular piston radiator in a rigid baffle are derived. These expansions are valid throughout the illuminated half-space and are useful for efficient numerical computation in the near-field region. Multipole coefficients are given by closed-form expressions which can be evaluated recursively.

  19. Stability and superluminality of spherical DBI Galileon solutions

    SciTech Connect

    Goon, Garrett L.; Hinterbichler, Kurt; Trodden, Mark

    2011-04-12

    We showed that, when considered as local modifications to gravity, such as in the solar system, there exists a region of parameter space in which spherically symmetric static solutions to a particular class of modified gravity theories exist and are stable.

  20. Stability and superluminality of spherical DBI Galileon solutions

    DOE PAGES

    Goon, Garrett L.; Hinterbichler, Kurt; Trodden, Mark

    2011-04-12

    We showed that, when considered as local modifications to gravity, such as in the solar system, there exists a region of parameter space in which spherically symmetric static solutions to a particular class of modified gravity theories exist and are stable.

  1. Imaging with classical spherical diffraction gratings: the quadrature configuration.

    PubMed

    Prieto-Blanco, Xesús; Montero-Orille, Carlos; González-Núñez, Héctor; Dolores Mouriz, María; López Lago, Elena; de la Fuente, Raúl

    2009-11-01

    We review the theory of spherical diffraction gratings with regard to their imaging properties in off-plane arrangements. Our study is restricted to gratings with equally spaced grooves, and it is focused on the quadrature configuration, where the incident and diffraction planes are orthogonal to each other. We identify regions of low astigmatism and propose some monochromator mounts.

  2. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Clouds on the horizon seem to wait for their rival Space Shuttle Atlantis as it churns billows of steam and smoke after launch. The perfect on-time liftoff of Atlantis on mission STS- 106 occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  3. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The clouds of steam and smoke generated from the launch of Space Shuttle Atlantis seem to blend with the sky. The launch is reflected in waters near Launch Pad 39B. The perfect on-time liftoff of Atlantis on mission STS-106 occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  4. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Space Shuttle Atlantis's solid rocket boosters trail brilliant flames that light up the clouds of smoke and steam and reflect in the waters Launch Pad 39B at launch. The perfect on-time liftoff of Atlantis on mission STS-106 occurred at 8:45:47 a.m. EDT. On the 11-day mission to the International Space Station, the seven- member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  5. A perfect launch of Atlantis on mission STS-106

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The waters near Launch Pad 39B reflect the brilliant red-orange flames from the solid rocket boosters as Space Shuttle Atlantis lifts off on its mission to the International Space Station. The perfect on-time launch occurred at 8:45:47 a.m. EDT. On the 11- day mission to the Station, the seven-member crew will perform support tasks on orbit, transfer supplies and prepare the living quarters in the newly arrived Zvezda Service Module. The first long-duration crew, dubbed '''Expedition One,''' is due to arrive at the Station in late fall. Landing of Atlantis is targeted for 4:45 a.m. EDT on Sept. 19.

  6. Transformation media producing quasi-perfect isotropic emission.

    PubMed

    Tichit, Paul-Henri; Burokur, Shah Nawaz; de Lustrac, André

    2011-10-10

    Using the idea of wave manipulation via transformation optics, we propose a way to create a quasi-perfect isotropic emission from a directional one. The manipulation is enabled by composite metamaterials that correspond to a space stretching around the source. It is shown that the directive radiation of a plane source larger than the operating wavelength can be transformed into an isotropic one by modifying the electromagnetic properties of the space around it. A set of parameters allowing practical realization of the proposed device is defined. Numerical simulations using Finite Element Method (FEM) are performed to illustrate the proposed coordinate transformation. This idea, which consists in strongly reducing the apparent size of a radiating source, can find various applications in novel antenna design techniques.

  7. Spherical demons: fast surface registration.

    PubMed

    Yeo, B T Thomas; Sabuncu, Mert; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina

    2008-01-01

    We present the fast Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizers for the modified demons objective function can be efficiently implemented on the sphere using convolution. Based on the one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast - registration of two cortical mesh models with more than 100k nodes takes less than 5 minutes, comparable to the fastest surface registration algorithms. Moreover, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different settings: (1) parcellation in a set of in-vivo cortical surfaces and (2) Brodmann area localization in ex-vivo cortical surfaces.

  8. Spherical Demons: Fast Surface Registration

    PubMed Central

    Yeo, B.T. Thomas; Sabuncu, Mert; Vercauteren, Tom; Ayache, Nicholas; Fischl, Bruce; Golland, Polina

    2009-01-01

    We present the fast Spherical Demons algorithm for registering two spherical images. By exploiting spherical vector spline interpolation theory, we show that a large class of regularizers for the modified demons objective function can be efficiently implemented on the sphere using convolution. Based on the one parameter subgroups of diffeomorphisms, the resulting registration is diffeomorphic and fast – registration of two cortical mesh models with more than 100k nodes takes less than 5 minutes, comparable to the fastest surface registration algorithms. Moreover, the accuracy of our method compares favorably to the popular FreeSurfer registration algorithm. We validate the technique in two different settings: (1) parcellation in a set of in-vivo cortical surfaces and (2) Brodmann area localization in ex-vivo cortical surfaces. PMID:18979813

  9. Stability analysis of self-similar behaviors in perfect fluid gravitational collapse

    SciTech Connect

    Mitsuda, Eiji; Tomimatsu, Akira

    2006-06-15

    Stability of self-similar solutions for gravitational collapse is an important problem to be investigated from the perspectives of their nature as an attractor, critical phenomena, and instability of a naked singularity. In this paper we study spherically symmetric non-self-similar perturbations of matter and metrics in spherically symmetric self-similar backgrounds. The collapsing matter is assumed to be a perfect fluid with the equation of state P={alpha}{rho}. We construct a single wave equation governing the perturbations, which makes their time evolution in arbitrary self-similar backgrounds analytically tractable. Further we propose an analytical application of this master wave equation to the stability problem by means of the normal mode analysis for the perturbations having the time dependence given by exp(i{omega}log vertical t vertical bar), and present some sufficient conditions for the absence of nonoscillatory unstable normal modes with purely imaginary {omega}.

  10. Basketballs as spherical acoustic cavities

    NASA Astrophysics Data System (ADS)

    Russell, Daniel A.

    2010-06-01

    The sound field resulting from striking a basketball is found to be rich in frequency content, with over 50 partials in the frequency range of 0-12 kHz. The frequencies are found to closely match theoretical expectations for standing wave patterns inside a spherical cavity. Because of the degenerate nature of the mode shapes, explicit identification of the modes is not possible without internal investigation with a microphone probe. A basketball proves to be an interesting application of a boundary value problem involving spherical coordinates.

  11. Radiance calibration of spherical integrators

    NASA Technical Reports Server (NTRS)

    Mclean, James T.; Guenther, Bruce W.

    1989-01-01

    Techniques for improving the knowledge of the radiance of large area spherical and hemispherical integrating energy sources have been investigated. Such sources are used to calibrate numerous aircraft and spacecraft remote sensing instruments. Comparisons are made between using a standard source based calibration method and a quantum efficient detector (QED) based calibration method. The uncertainty involved in transferring the calibrated values of the point source standard lamp to the extended source is estimated to be 5 to 10 percent. The use of the QED allows an improvement in the uncertainty to 1 to 2 percent for the measurement of absolute radiance from a spherical integrator source.

  12. Determining spherical lens correction for astronaut training underwater

    PubMed Central

    Porter, Jason; Gibson, C. Robert; Strauss, Samuel

    2013-01-01

    Purpose To develop a model that will accurately predict the distance spherical lens correction needed to be worn by National Aeronautics and Space Administration (NASA) astronauts while training underwater. The replica space suit’s helmet contains curved visors that induce refractive power when submersed in water. Methods Anterior surface powers and thicknesses were measured for the helmet’s protective and inside visors. The impact of each visor on the helmet’s refractive power in water was analyzed using thick lens calculations and Zemax optical design software. Using geometrical optics approximations, a model was developed to determine the optimal distance spherical power needed to be worn underwater based on the helmet’s total induced spherical power underwater and the astronaut’s manifest spectacle plane correction in air. The validity of the model was tested using data from both eyes of 10 astronauts who trained underwater. Results The helmet visors induced a total power of −2.737 D when placed underwater. The required underwater spherical correction (FW) was linearly related to the spectacle plane spherical correction in air (FAir): FW = FAir + 2.356 D. The mean magnitude of the difference between the actual correction worn underwater and the calculated underwater correction was 0.20 ± 0.11 D. The actual and calculated values were highly correlated (R = 0.971) with 70% of eyes having a difference in magnitude of < 0.25 D between values. Conclusions We devised a model to calculate the spherical spectacle lens correction needed to be worn underwater by National Aeronautics and Space Administration astronauts. The model accurately predicts the actual values worn underwater and can be applied (more generally) to determine a suitable spectacle lens correction to be worn behind other types of masks when submerged underwater. PMID:21623249

  13. Method for accurate optical alignment using diffraction rings from lenses with spherical aberration.

    PubMed

    Gwynn, R B; Christensen, D A

    1993-03-01

    A useful alignment method is presented that exploits the closely spaced concentric fringes that form in the longitudinal spherical aberration region of positive spherical lenses imaging a point source. To align one or more elements to a common axis, spherical lenses are attached precisely to the elements and the resulting diffraction rings are made to coincide. We modeled the spherical aberration of the lenses by calculating the diffraction patterns of converging plane waves passing through concentric narrow annular apertures. The validity of the model is supported by experimental data and is determined to be accurate for a prototype penumbral imaging alignment system developed at Lawrence Livermore National Laboratory.

  14. Euclidean, Spherical, and Hyperbolic Shadows

    ERIC Educational Resources Information Center

    Hoban, Ryan

    2013-01-01

    Many classical problems in elementary calculus use Euclidean geometry. This article takes such a problem and solves it in hyperbolic and in spherical geometry instead. The solution requires only the ability to compute distances and intersections of points in these geometries. The dramatically different results we obtain illustrate the effect…

  15. Euclidean, Spherical, and Hyperbolic Shadows

    ERIC Educational Resources Information Center

    Hoban, Ryan

    2013-01-01

    Many classical problems in elementary calculus use Euclidean geometry. This article takes such a problem and solves it in hyperbolic and in spherical geometry instead. The solution requires only the ability to compute distances and intersections of points in these geometries. The dramatically different results we obtain illustrate the effect…

  16. A Module in Spherical Trigonometry.

    ERIC Educational Resources Information Center

    Congleton, C. A.; Broome, L. E.

    1980-01-01

    This module, designed for use at the high school level as a four- to eight-hour topic, includes: the geometry of a sphere, the coordinate system used to describe points on the earth's surface, parallel and meridian sailing, and the solution of right spherical triangles. (Author/MK)

  17. Spherical-Bearing Analysis Program

    NASA Technical Reports Server (NTRS)

    Kleckner, R. J.

    1984-01-01

    Computer program SPHERBEAN, developed to predict thermomechanical performance characteristics of double-row spherical roller bearings over wide range of operating conditions. Analysis allows six degrees of freedom for each roller and three for each half of an optionally split cage. Program capabilities provide sufficient generality to allow detailed simulation of both high-speed and conventional bearing operation.

  18. Dispersion in Spherical Water Drops.

    ERIC Educational Resources Information Center

    Eliason, John C., Jr.

    1989-01-01

    Discusses a laboratory exercise simulating the paths of light rays through spherical water drops by applying principles of ray optics and geometry. Describes four parts: determining the output angles, computer simulation, explorations, model testing, and solutions. Provides a computer program and some diagrams. (YP)

  19. Dispersion in Spherical Water Drops.

    ERIC Educational Resources Information Center

    Eliason, John C., Jr.

    1989-01-01

    Discusses a laboratory exercise simulating the paths of light rays through spherical water drops by applying principles of ray optics and geometry. Describes four parts: determining the output angles, computer simulation, explorations, model testing, and solutions. Provides a computer program and some diagrams. (YP)

  20. A Module in Spherical Trigonometry.

    ERIC Educational Resources Information Center

    Congleton, C. A.; Broome, L. E.

    1980-01-01

    This module, designed for use at the high school level as a four- to eight-hour topic, includes: the geometry of a sphere, the coordinate system used to describe points on the earth's surface, parallel and meridian sailing, and the solution of right spherical triangles. (Author/MK)

  1. The undirected incomplete perfect phylogeny problem.

    PubMed

    Satya, Ravi Vijaya; Mukherjee, Amar

    2008-01-01

    The incomplete perfect phylogeny (IPP) problem and the incomplete perfect phylogeny haplotyping (IPPH) problem deal with constructing a phylogeny for a given set of haplotypes or genotypes with missing entries. The earlier approaches for both of these problems dealt with restricted versions of the problems, where the root is either available or can be trivially re-constructed from the data, or certain assumptions were made about the data. In this paper, we deal with the unrestricted versions of the problems, where the root of the phylogeny is neither available nor trivially recoverable from the data. Both IPP and IPPH problems have previously been proven to be NP-complete. Here, we present efficient enumerative algorithms that can handle practical instances of the problem. Empirical analysis on simulated data shows that the algorithms perform very well both in terms of speed and in terms accuracy of the recovered data.

  2. [Guide to perfect prescribing in Switzerland].

    PubMed

    Arnet, Isabelle; Hersberger, Kurt E

    2014-06-01

    An important initial step in the medication process is prescription writing. The more perfect it is, the more successfully can a therapy be performed. Imprecisions and missing information lead to unnecessary queries or to errors which are often randomly discovered during a later consultation. A "perfect prescription" serves every individual involved in the medication process. The prescription document contains the instructions for the patient, the pharmacist, the nurse, and other health professionals involved in the therapy. The prescription writing process is regulated by several laws and decrees which were enacted to assure the greatest possible drug safety. Deviations from the norm may be necessary in individual cases, which require an even more responsible prescribing and explicit indication.

  3. Nonminimal coupling of perfect fluids to curvature

    SciTech Connect

    Bertolami, Orfeu; Lobo, Francisco S. N.; Paramos, Jorge

    2008-09-15

    In this work, we consider different forms of relativistic perfect fluid Lagrangian densities that yield the same gravitational field equations in general relativity (GR). A particularly intriguing example is the case with couplings of the form [1+f{sub 2}(R)]L{sub m}, where R is the scalar curvature, which induces an extra force that depends on the form of the Lagrangian density. It has been found that, considering the Lagrangian density L{sub m}=p, where p is the pressure, the extra-force vanishes. We argue that this is not the unique choice for the matter Lagrangian density, and that more natural forms for L{sub m} do not imply the vanishing of the extra force. Particular attention is paid to the impact on the classical equivalence between different Lagrangian descriptions of a perfect fluid.

  4. The erythrocyte ghost is a perfect osmometer.

    PubMed

    Kwant, W O; Seeman, P

    1970-02-01

    The osmotic swelling of intact erythrocytes in hypotonic solutions was measured using microhematocrit tubes, Van Allen tubes, and a calibrated Coulter counter. In agreement with earlier workers the intact cells did not behave as perfect osmometers, the cells swelling less than predicted by the Boyle-van't Hoff law. Erythrocyte ghosts were prepared from fresh intact erythrocytes by one-step hemolysis in 0.25% NaCl at an extremely dilute concentration of cells and the membranes were sealed at 37 degrees . The ghosts were mixed with NaCl solutions of different osmolarities and the MCV (mean cell volume) of the shrunken cells immediately monitored by a calibrated Coulter counter. It was found that the MCV values of the shrunken ghosts were accurately predicted by the Boyle-van't Hoff law. These results indicate that these erythrocyte ghosts behaved as perfect osmometers.

  5. Explaining evolution via constrained persistent perfect phylogeny.

    PubMed

    Bonizzoni, Paola; Carrieri, Anna Paola; Della Vedova, Gianluca; Trucco, Gabriella

    2014-01-01

    The perfect phylogeny is an often used model in phylogenetics since it provides an efficient basic procedure for representing the evolution of genomic binary characters in several frameworks, such as for example in haplotype inference. The model, which is conceptually the simplest, is based on the infinite sites assumption, that is no character can mutate more than once in the whole tree. A main open problem regarding the model is finding generalizations that retain the computational tractability of the original model but are more flexible in modeling biological data when the infinite site assumption is violated because of e.g. back mutations. A special case of back mutations that has been considered in the study of the evolution of protein domains (where a domain is acquired and then lost) is persistency, that is the fact that a character is allowed to return back to the ancestral state. In this model characters can be gained and lost at most once. In this paper we consider the computational problem of explaining binary data by the Persistent Perfect Phylogeny model (referred as PPP) and for this purpose we investigate the problem of reconstructing an evolution where some constraints are imposed on the paths of the tree. We define a natural generalization of the PPP problem obtained by requiring that for some pairs (character, species), neither the species nor any of its ancestors can have the character. In other words, some characters cannot be persistent for some species. This new problem is called Constrained PPP (CPPP). Based on a graph formulation of the CPPP problem, we are able to provide a polynomial time solution for the CPPP problem for matrices whose conflict graph has no edges. Using this result, we develop a parameterized algorithm for solving the CPPP problem where the parameter is the number of characters. A preliminary experimental analysis shows that the constrained persistent perfect phylogeny model allows to explain efficiently data that do not

  6. VANDENBERG AFB, CALIF. - A worker in the NASA spacecraft processing facility on North Vandenberg Air Force Base adjust the supports on a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-03

    VANDENBERG AFB, CALIF. - A worker in the NASA spacecraft processing facility on North Vandenberg Air Force Base adjust the supports on a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  7. VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, Dr. Francis Everitt, principal investigator, and Brad Parkinson, co-principal investigator, both from Stanford University, hold one of the small gyroscopes used in the Gravity Probe B spacecraft. The GP-B towers behind them. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-10

    VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, Dr. Francis Everitt, principal investigator, and Brad Parkinson, co-principal investigator, both from Stanford University, hold one of the small gyroscopes used in the Gravity Probe B spacecraft. The GP-B towers behind them. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  8. VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base work on a solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-03

    VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base work on a solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  9. VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach supports to a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-03

    VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach supports to a solar array panel to be lifted and installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  10. VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with two solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-04

    VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with two solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  11. VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare to rotate the framework containing one of four solar panels to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-03

    VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare to rotate the framework containing one of four solar panels to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  12. VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with all four solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-04

    VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, the Gravity Probe B spacecraft is seen with all four solar array panels installed. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  13. VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach a solar array panel on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-03

    VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base attach a solar array panel on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  14. VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a balloon gently lifts the solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-04

    VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a balloon gently lifts the solar array panel to be installed on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  15. VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to attach the top of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-04

    VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, workers prepare to attach the top of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  16. VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare for the installation of solar array panel 3 on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-03

    VANDENBERG AFB, CALIF. - Workers in the NASA spacecraft processing facility on North Vandenberg Air Force Base prepare for the installation of solar array panel 3 on the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  17. VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a worker checks the installation of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

    NASA Image and Video Library

    2003-11-04

    VANDENBERG AFB, CALIF. - In the NASA spacecraft processing facility on North Vandenberg Air Force Base, a worker checks the installation of a solar array panel onto the Gravity Probe B spacecraft. Installing each array is a 3-day process and includes a functional deployment test. The Gravity Probe B mission is a relativity experiment developed by NASA’s Marshall Space Flight Center, Stanford University and Lockheed Martin. The spacecraft will test two extraordinary predictions of Albert Einstein’s general theory of relativity that he advanced in 1916: the geodetic effect (how space and time are warped by the presence of the Earth) and frame dragging (how Earth’s rotation drags space and time around with it). Gravity Probe B consists of four sophisticated gyroscopes that will provide an almost perfect space-time reference system. The mission will look in a precision manner for tiny changes in the direction of spin.

  18. Optimal Feedback Controlled Assembly of Perfect Crystals.

    PubMed

    Tang, Xun; Rupp, Bradley; Yang, Yuguang; Edwards, Tara D; Grover, Martha A; Bevan, Michael A

    2016-07-26

    Perfectly ordered states are targets in diverse molecular to microscale systems involving, for example, atomic clusters, protein folding, protein crystallization, nanoparticle superlattices, and colloidal crystals. However, there is no obvious approach to control the assembly of perfectly ordered global free energy minimum structures; near-equilibrium assembly is impractically slow, and faster out-of-equilibrium processes generally terminate in defective states. Here, we demonstrate the rapid and robust assembly of perfect crystals by navigating kinetic bottlenecks using closed-loop control of electric field mediated crystallization of colloidal particles. An optimal policy is computed with dynamic programming using a reaction coordinate based dynamic model. By tracking real-time stochastic particle configurations and adjusting applied fields via feedback, the evolution of unassembled particles is guided through polycrystalline states into single domain crystals. This approach to controlling the assembly of a target structure is based on general principles that make it applicable to a broad range of processes from nano- to microscales (where tuning a global thermodynamic variable yields temporal control over thermal sampling of different states via their relative free energies).

  19. How perfect is a neutron fluid?

    NASA Astrophysics Data System (ADS)

    Fu, Dan; Mekjian, Aram

    2011-04-01

    A perfect fluid has the lowest shear viscosity allowed by the uncertainty principle which also involves a study of the entropy density. Kinetic theory based on the Chapman-Enskog approach is used to obtain both the classical and quantum values of the viscosity of a neutron fluid. The interaction potential used in the study is an attractive square well with an inner hard core. The classical scattering angle and the phase shifts are calculated for this potential. The entropy density is based on the Sakur-Tetrode law plus corrections coming from two particle interactions obtained from a Beth-Ulhenbeck expression. Using these results for the viscosity and entropy density, the perfect fluid aspects of a neutron fluid are addressed. The viscosity to number density is also proportional to Planck's constant. The proportionality constant, called alpha, is found to be of the order of 1 in a quantum description of a neutron fluid. The value of the viscosity for a neutron fluid is near its unitary limit. For air at STP alpha is 7500, for water alpha is 300. The results for neutron matter suggest a near perfect fluid behavior. Supported by DOE-Grant DE-FG02Er-40987

  20. Study of striations in a spherically symmetric hydrogen discharge

    NASA Astrophysics Data System (ADS)

    Lowell Morgan, W.; Childs, Montgomery W.

    2015-10-01

    Experiments on a high power spherically symmetric positive corona discharge in molecular hydrogen are reported upon. These are collisional plasmas in the H2 pressure range of about 0.75 Torr to 3 Torr. Applied voltages ranged up to 600 V on the anode with currents ranging up to 3 A. As others have observed in prior published experiments going back to 1997, we have observed spherically symmetric striations or double layers. Others have observed such striations in O2, CO2, and in mixtures of N2 and acetone or methanol, or benzene. Like H2 all these gases, except N2 itself, readily dissociate and form negative ions by dissociative attachment with electrons. We propose that the striations are instabilities arising from copious formation of negative ions that modify the radial space charge and electric field distributions in such high aspect ratio spherical discharges.

  1. Spherical navigator registration using harmonic analysis for prospective motion correction.

    PubMed

    Wyatt, C L; Ari, N; Kraft, R A

    2005-01-01

    Spherical navigators are an attractive approach to motion compensation in Magnetic Resonance Imaging. Because they can be acquired quickly, spherical navigators have the potential to measure and correct for rigid motion during image acquisition (prospectively as opposed to retrospectively). A limiting factor to prospective use of navigators is the time required to estimate the motion parameters. This estimation problem can be separated into a rotational and translational component. Recovery of the rotational motion can be cast as a registration of functions defined on a sphere. Previous methods for solving this registration problem are based on optimization strategies that are iterative and require k-space interpolation. Such approaches have undesirable convergence behavior for prospective use since the estimation complexity depends on both the number of samples and the amount of rotation. We propose and demonstrate an efficient algorithm for recovery of rotational motion using spherical navigators. We decompose the navigator magnitude using the spherical harmonic transform. In this framework, rigid rotations can be recovered from an over-constrained system of equations, leading to a computationally efficient algorithm for prospective motion compensation. The resulting algorithm is compared to existing approaches in simulated and actual navigator data. These results show that the spherical harmonic based estimation algorithm is significantly faster than existing methods and so is suited for prospective motion correction.

  2. A Fast Spherical Filter with Uniform Resolution

    NASA Astrophysics Data System (ADS)

    Jakob-Chien, Rüdiger; Alpert, Bradley K.

    1997-09-01

    This paper introduces a fast algorithm for obtaining a uniform resolution representation of a function known at a latitude-longitude grid on the surface of a sphere, equivalent to a triangular, isotropic truncation of the spherical harmonic coefficients for the function. The proposedspectral truncation method,which is based on the fast multipole method and the fast Fourier transform, projects the function to a space with uniform resolution while avoiding surface harmonic transformations. The method requiresO(N2logN) operations forO(N2) grid points, as opposed toO(N3) operations for the standard spectral transform method, providing a reduced-complexity spectral method obviating the pole problem in the integration of time-dependent partial differential equations on the sphere. The filter's performance is demonstrated with numerical examples.

  3. Electronic Switching Spherical Array (ESSA) antenna systems

    NASA Technical Reports Server (NTRS)

    Hockensmith, R. P.

    1984-01-01

    ESSA (Electronic Switching Spherical Array) is an antenna system conceived, developed and qualified for linking satellite data transmissions with NASA's tracking and data relay satellites (TDRSS) and tracking and data acquisition satellites (TDAS). ESSA functions in the S band frequency region, cover 2 pi or more steradians with directional gain and operates in multiple selectable modes. ESSA operates in concert with the NASA's TDRS standard transponder in the retrodirective mode or independently in directional beam, program track and special modes. Organizations and projects to the ESSA applications for NASA's space use are introduced. Coverage gain, weight power and implementation and other performance information for satisfying a wide range of data rate requirements are included.

  4. Newtonian wormholes with spherical symmetry and tidal forces on test particles

    NASA Astrophysics Data System (ADS)

    Luz, Paulo; Lemos, José P. S.

    2015-06-01

    A spherically symmetric wormhole in Newtonian gravitation in curved space, enhanced with a connection between the mass density and the Ricci scalar, is presented. The wormhole, consisting of two connected asymptotically flat regions, inhabits a spherically symmetric curved space. The gravitational potential, gravitational field and the pressure that supports the fluid that permeates the Newtonian wormhole are computed. Particle dynamics and tidal effects in this geometry are studied. The possibility of having Newtonian black holes in this theory is sketched.

  5. Orthogonality of spherical harmonic coefficients

    NASA Technical Reports Server (NTRS)

    Mcleod, M. G.

    1980-01-01

    Orthogonality relations are obtained for the spherical harmonic coefficients of functions defined on the surface of a sphere. Following a brief discussion of the orthogonality of Fourier series coefficients, consideration is given to the values averaged over all orientations of the coordinate system of the spherical harmonic coefficients of a function defined on the surface of a sphere that can be expressed in terms of Legendre polynomials for the special case where the function is the sum of two delta functions located at two different points on the sphere, and for the case of an essentially arbitrary function. It is noted that the orthogonality relations derived have found applications in statistical studies of the geomagnetic field.

  6. Orthogonality of spherical harmonic coefficients

    NASA Technical Reports Server (NTRS)

    Mcleod, M. G.

    1980-01-01

    Orthogonality relations are obtained for the spherical harmonic coefficients of functions defined on the surface of a sphere. Following a brief discussion of the orthogonality of Fourier series coefficients, consideration is given to the values averaged over all orientations of the coordinate system of the spherical harmonic coefficients of a function defined on the surface of a sphere that can be expressed in terms of Legendre polynomials for the special case where the function is the sum of two delta functions located at two different points on the sphere, and for the case of an essentially arbitrary function. It is noted that the orthogonality relations derived have found applications in statistical studies of the geomagnetic field.

  7. Fresnel diffraction by spherical obstacles

    NASA Technical Reports Server (NTRS)

    Hovenac, Edward A.

    1989-01-01

    Lommel functions were used to solve the Fresnel-Kirchhoff diffraction integral for the case of a spherical obstacle. Comparisons were made between Fresnel diffraction theory and Mie scattering theory. Fresnel theory is then compared to experimental data. Experiment and theory typically deviated from one another by less than 10 percent. A unique experimental setup using mercury spheres suspended in a viscous fluid significantly reduced optical noise. The major source of error was due to the Gaussian-shaped laser beam.

  8. An almost 'perfectly' diffuse, 'perfect' reflector for far-infrared reflectance calibration

    NASA Technical Reports Server (NTRS)

    Smith, Sheldon M.

    1993-01-01

    Specular and diffuse reflectance measurements made near normal incidence of two very rough, solid aluminum surfaces are presented for the wavelength range from 2.2 to 512 microns. The diffuse measurements made at nonspecular angles by two different detectors indicate that between 33 and 201 microns the reflectance of one surface is nearly Lambertian (isotropic) with a bidirectional reflectance distribution function (BRDF) value within 32 percent of the theoretical value of (1/pi)/sr for a perfectly diffuse, perfect reflector. Photometric reflectance spectra at the specular angle show that between 6.9 and 100 microns the specular BRDF of these surfaces is within 5 percent of the theoretical value of (1/pi)/sr. At longer wavelengths of 235, 320, and 512 microns the specular reflectance rapidly departs from that of a perfectly diffuse, perfect reflector. The two samples studied have rms surface roughnesses of 44 and 60 microns. A durable metal surface with these near perfect reflectance characteristics can be advantageously used in the FIR as a black-body source, the interior surface of an integrating sphere, and most especially as an absolute calibration standard. BRDF measurements at 40 deg incidence, though still highly diffuse, show a significant departure from Lambertian reflectance.

  9. Comparison of elliptical and spherical mirrors for the grasshopper monochromators at SSRL

    SciTech Connect

    Waldhauer, A. P.

    1989-07-01

    A comparison of the performance of a spherical and elliptical mirror in the grasshopper monochromator is presented. The problem was studied by ray tracing and then tested using visible (/lambda/=633 nm) laser light. Calculations using ideal optics yield an improvement in flux by a factor of up to 2.7, while tests with visible light show an increase by a factor of 5 because the old spherical mirror is compared to a new, perfect elliptical one. The FWHM of the measured focus is 90 /mu/m with a spherical mirror, and 25 /mu/m with an elliptical one. Elliptical mirrors have been acquired and are now being installed in the two grasshoppers at SSRL.

  10. Comparison of elliptical and spherical mirrors for the grasshopper monochromators at SSRL

    NASA Astrophysics Data System (ADS)

    Waldhauer, A. P.

    1989-07-01

    A comparison of the performance of a spherical and elliptical mirror in the grasshopper monochromator is presented. The problem was studied by ray tracing and then tested using visible (λ=633 nm) laser light. Calculations using ideal optics yield an improvement in flux by a factor of up to 2.7, while tests with visible light show an increase by a factor of 5 because the old spherical mirror is compared to a new, perfect elliptical one. The FWHM of the measured focus is 90 μm with a spherical mirror, and 25 μm with an elliptical one. Elliptical mirrors have been acquired and are now being installed in the two grasshoppers at SSRL.

  11. Approach of spherical harmonics to the representation of the deformed su(1,1) algebra

    SciTech Connect

    Fakhri, H.; Ghaneh, T.

    2008-11-15

    The m-shifting generators of su(2) algebra together with a pair of l-shifting ladder symmetry operators have been used in the space of all spherical harmonics Y{sub l}{sup m}({theta},{phi}) in order to introduce a new set of operators, expressing the transitions between them. It is shown that the space of spherical harmonics whose l+2m or l-2m is given presents negative and positive irreducible representations of a deformed su(1,1) algebra, respectively. These internal symmetries also suggest new algebraic methods to construct the spherical harmonics in the framework of the spectrum-generating algebras.

  12. Perfect mixing of immiscible macromolecules at fluid interfaces

    NASA Astrophysics Data System (ADS)

    Sheiko, Sergei; Matyjaszewski, Krzysztof; Tsukruk, Vladimir; Carrillo, Jan-Michael; Rubinstein, Michael; Dobrynin, Andrey; Zhou, Jing

    2014-03-01

    Macromolecules typically phase separate unless their shapes and chemical compositions are tailored to explicitly drive mixing. But now our research has shown that physical constraints can drive spontaneous mixing of chemically different species. We have obtained long-range 2D arrays of perfectly mixed macromolecules having a variety of molecular architectures and chemistries, including linear chains, block-copolymer stars, and bottlebrush copolymers with hydrophobic, hydrophilic, and lipophobic chemical compositions. This is achieved by entropy-driven enhancement of steric repulsion between macromolecules anchored on a substrate. By monitoring the kinetics of mixing, we have proved that molecular intercalation is an equilibrium state. The array spacing is controlled by the length of the brush side chains. This entropic templating strategy opens new ways for generating patterns on sub-100 nm length scales with potential application in lithography, directed self-assembly, and biomedical assays. Financial support from the National Science Foundation DMR-0906985, DMR-1004576, DMR-1122483, and DMR-0907515.

  13. A Perfect Electromagnetic Cavity: High Quality Factor in Subwavelength Dimensions

    NASA Astrophysics Data System (ADS)

    Ginis, Vincent; Tassin, Philippe; Soukoulis, Costas M.; Veretennicoff, Irina

    2010-03-01

    Transformation optics has recently provided a new way to look at the interaction between light and matter. It uses the analogy between the macroscopic Maxwell's equations in complex dielectrics and the free-space Maxwell's equations on the background of an arbitrary metric to exploit the full potential of metamaterials, of which the most exciting examples are invisibility cloaks. In this contribution, we want to show how transformation optics can be applied to design a cavity with extraordinary properties. We have demonstrated theoretically the existence of eigenmodes whose wavelength is much larger than the characteristic dimensions of the cavity. Furthermore, our design avoids the bending losses observed in traditional microcavities, so that the quality factor is only limited by intrinsic absorption of the materials. Such a ``perfect cavity'' may be interesting for applications involving optical data storage or quantum optics, where it can be used to control the rate of spontaneous emission through the Purcell effect.

  14. Coherent perfect absorption in one-sided reflectionless media

    PubMed Central

    Wu, Jin-Hui; Artoni, M.; La Rocca, G. C.

    2016-01-01

    In optical experiments one-sided reflectionless (ORL) and coherent perfect absorption (CPA) are unusual scattering properties yet fascinating for their fundamental aspects and for their practical interest. Although these two concepts have so far remained separated from each other, we prove that the two phenomena are indeed strictly connected. We show that a CPA–ORL connection exists between pairs of points lying along lines close to each other in the 3D space-parameters of a realistic lossy atomic photonic crystal. The connection is expected to be a generic feature of wave scattering in non-Hermitian optical media encompassing, as a particular case, wave scattering in parity-time (PT) symmetric media. PMID:27759020

  15. Registering spherical navigators with spherical harmonic expansions to measure three-dimensional rotations in magnetic resonance imaging.

    PubMed

    Costa, Andreu F; Yen, Yi-Fen; Drangova, Maria

    2010-02-01

    Subject motion remains a challenging problem to overcome in clinical and research applications of magnetic resonance imaging (MRI). Subject motion degrades the quality of MR images and the integrity of experimental data. A promising method to correct for subject motion in MRI is the spherical navigator (SNAV) echo. Spherical navigators acquire k-space data on the surface of a sphere in order to measure three-dimensional (3D) rigid-body motion. Analysis begins by registering the magnitude of two SNAVs to determine the 3D rotation between them. Several different methods to register SNAV data exist, each with specific capabilities and limitations. In this study, we assessed the accuracy, precision and computational requirements of measuring rotations about all three coordinate axes by correlating the spherical harmonic expansions of SNAV data. We compare the results of this technique to previous SNAV studies and show that, although computationally expensive, the spherical harmonic technique is a highly accurate, precise and robust method to register SNAVs and detect 3D rotations in MRI. A key advantage to the spherical harmonic technique is the ability to optimize the accuracy, precision, processing time and memory requirements by adjusting parameters used in the registration. While present developments are aimed at improving the programming efficiency and memory handling of the algorithm, this registration technique is currently well suited for retrospective motion correction applications, such as removing motion-related image artifacts and aligning slices within a high-resolution 3D volume. Copyright 2010 Elsevier Inc. All rights reserved.

  16. Sphericity Tests and Repeated Measures Data.

    ERIC Educational Resources Information Center

    Robey, Randall R.; Barcikowski, Robert S.

    The mixed model analysis of variance assumes a mathematical property known as sphericity. Several preliminary tests have been proposed to detect departures from the sphericity assumption. The logic of the preliminary testing procedure is to conduct the mixed model analysis of variance if the preliminary test suggests that the sphericity assumption…

  17. The Perfect Aspect as a State of Being.

    ERIC Educational Resources Information Center

    Moy, Raymond H.

    English as second language (ESL) learners often avoid using the present perfect or use it improperly. In contrast with native speakers of English sampled from newspaper editorials, of whom 75 percent used the present perfect, only 22 percent of ESL college students used the present perfect correctly. This avoidance is due in part to lack of…

  18. Inversion of the Earth spherical albedo from radiation-pressure

    NASA Astrophysics Data System (ADS)

    Wilkman, Olli; Herranen, Joonas; Näränen, Jyri; Virtanen, Jenni; Koivula, Hannu; Poutanen, Markku; Penttilä, Antti; Gritsevich, Maria; Muinonen, Karri

    2017-04-01

    We are studying the retrieval of the spherical albedo and net radiation of the Earth from the perturbations caused by the planet's radiation on the dynamics of its satellites. The spherical or Bond albedo gives the ratio of the fluxes incident on and scattered by the planet. The net radiation represents the net heat input into the planet's climate system and drives changes in its atmospheric, surface, and ocean temperatures. The ultimate aim of the study is inverting the problem and estimating the Earth albedo based on observations of satellites, simultaneously improving the space-geodetic positioning accuracy. Here we investigate the effect of the spherical albedo on satellite orbits with the help of a simplified model. We simulate the propagation of satellite orbits using a new simulation software. The simulation contains the main perturbing forces on medium and high Earth orbits, used by, e.g., navigation satellites, including the radiation pressure of reflected sunlight from the Earth. An arbitrary satellite shape model can be used, and the rotation of the satellite is modeled. In this first study, we use a box-wing satellite model with a simple surface BRDF. We also assume a diffusely reflecting Earth with a single global albedo value. We vary the Earth albedo and search for systematic effects on different orbits. Thereafter, we estimate the dependence of the albedo accuracy on the satellite positioning and timing data available. We show that the inversion of the spherical albedo with reasonable accuracy is feasible from the current space-geodetic measurements.

  19. Designing perfect linear polarization converters using perfect electric and magnetic conducting surfaces.

    PubMed

    Zhou, Gaochao; Tao, Xudong; Shen, Ze; Zhu, Guanghao; Jin, Biaobing; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

    2016-12-13

    We propose a kind of general framework for the design of a perfect linear polarization converter that works in the transmission mode. Using an intuitive picture that is based on the method of bi-directional polarization mode decomposition, it is shown that when the device under consideration simultaneously possesses two complementary symmetry planes, with one being equivalent to a perfect electric conducting surface and the other being equivalent to a perfect magnetic conducting surface, linear polarization conversion can occur with an efficiency of 100% in the absence of absorptive losses. The proposed framework is validated by two design examples that operate near 10 GHz, where the numerical, experimental and analytic results are in good agreements.

  20. Designing perfect linear polarization converters using perfect electric and magnetic conducting surfaces

    PubMed Central

    Zhou, Gaochao; Tao, Xudong; Shen, Ze; Zhu, Guanghao; Jin, Biaobing; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

    2016-01-01

    We propose a kind of general framework for the design of a perfect linear polarization converter that works in the transmission mode. Using an intuitive picture that is based on the method of bi-directional polarization mode decomposition, it is shown that when the device under consideration simultaneously possesses two complementary symmetry planes, with one being equivalent to a perfect electric conducting surface and the other being equivalent to a perfect magnetic conducting surface, linear polarization conversion can occur with an efficiency of 100% in the absence of absorptive losses. The proposed framework is validated by two design examples that operate near 10 GHz, where the numerical, experimental and analytic results are in good agreements. PMID:27958313

  1. CHARGED TORI IN SPHERICAL GRAVITATIONAL AND DIPOLAR MAGNETIC FIELDS

    SciTech Connect

    Slany, P.; Kovar, J.; Stuchlik, Z.; Karas, V.

    2013-03-01

    A Newtonian model of non-conductive, charged, perfect fluid tori orbiting in combined spherical gravitational and dipolar magnetic fields is presented and stationary, axisymmetric toroidal structures are analyzed. Matter in such tori exhibits a purely circulatory motion and the resulting convection carries charges into permanent rotation around the symmetry axis. As a main result, we demonstrate the possible existence of off-equatorial charged tori and equatorial tori with cusps that also enable outflows of matter from the torus in the Newtonian regime. These phenomena qualitatively represent a new consequence of the interplay between gravity and electromagnetism. From an astrophysical point of view, our investigation can provide insight into processes that determine the vertical structure of dusty tori surrounding accretion disks.

  2. Dynamics of an initially spherical bubble rising in quiescent liquid

    NASA Astrophysics Data System (ADS)

    Tripathi, Manoj Kumar; Sahu, Kirti Chandra; Govindarajan, Rama

    2015-02-01

    The beauty and complexity of the shapes and dynamics of bubbles rising in liquid have fascinated scientists for centuries. Here we perform simulations on an initially spherical bubble starting from rest. We report that the dynamics is fully three-dimensional, and provide a broad canvas of behaviour patterns. Our phase plot in the Galilei-Eötvös plane shows five distinct regimes with sharply defined boundaries. Two symmetry-loss regimes are found: one with minor asymmetry restricted to a flapping skirt; and another with marked shape evolution. A perfect correlation between large shape asymmetry and path instability is established. In regimes corresponding to peripheral breakup and toroid formation, the dynamics is unsteady. A new kind of breakup, into a bulb-shaped bubble and a few satellite drops is found at low Morton numbers. The findings are of fundamental and practical relevance. It is hoped that experimenters will be motivated to check our predictions.

  3. Explaining evolution via constrained persistent perfect phylogeny

    PubMed Central

    2014-01-01

    Background The perfect phylogeny is an often used model in phylogenetics since it provides an efficient basic procedure for representing the evolution of genomic binary characters in several frameworks, such as for example in haplotype inference. The model, which is conceptually the simplest, is based on the infinite sites assumption, that is no character can mutate more than once in the whole tree. A main open problem regarding the model is finding generalizations that retain the computational tractability of the original model but are more flexible in modeling biological data when the infinite site assumption is violated because of e.g. back mutations. A special case of back mutations that has been considered in the study of the evolution of protein domains (where a domain is acquired and then lost) is persistency, that is the fact that a character is allowed to return back to the ancestral state. In this model characters can be gained and lost at most once. In this paper we consider the computational problem of explaining binary data by the Persistent Perfect Phylogeny model (referred as PPP) and for this purpose we investigate the problem of reconstructing an evolution where some constraints are imposed on the paths of the tree. Results We define a natural generalization of the PPP problem obtained by requiring that for some pairs (character, species), neither the species nor any of its ancestors can have the character. In other words, some characters cannot be persistent for some species. This new problem is called Constrained PPP (CPPP). Based on a graph formulation of the CPPP problem, we are able to provide a polynomial time solution for the CPPP problem for matrices whose conflict graph has no edges. Using this result, we develop a parameterized algorithm for solving the CPPP problem where the parameter is the number of characters. Conclusions A preliminary experimental analysis shows that the constrained persistent perfect phylogeny model allows to

  4. Design optimization of nanostrip metamaterial perfect absorbers

    NASA Astrophysics Data System (ADS)

    El-Aasser, Mostafa A.

    2014-01-01

    Metamaterial perfect absorber (MPA) promises many applications due to its capability of complete suppression of transmission or/and reflection. The complete dissipation of the incident electromagnetic energy by the absorptive meta-atoms makes it a unique candidate in many photonic and optoelectronic devices. An ultrathin metamaterial absorber that consists of a periodic nanostrip metal on top of a planar dielectric slab backed by a conducting metal plate is presented. The spectral absorptivity of MPA is investigated by the finite difference time domain method from visible to near-infrared. The various geometrical and material parameters of MPA are optimized for maximum absorption.

  5. Perfection of Apoferritin Crystals: An Advanced X-Ray Imaging and Diffraction Study

    NASA Technical Reports Server (NTRS)

    Hu, Z. W.; Thomas, B. R.; Chernov, A. A.; Chu, Y. S.

    2003-01-01

    Ferritin is a well-known iron-storage protein, and is a spherical shell that consists of 24 identical subunits packed in a 432 symmetry. The typically large protein size and its distinction from lysozyme as to chemical and physical characteristics make ferritin an attractive model protein for crystal growth and perfection investigation-as an alternative to the most widely studied lysozyme. In this contribution, the latest results obtained from coherence-based x-ray diffraction imaging and diffraction experiments will be presented on octahedral apoferritin (a demetalized form of ferritin) crystals grown from various growth conditions. Crystal specimens, which have the measured rocking-curve widths varying from a few arcseconds to several tens arcseconds (or more), are comparatively examined by intrinsically highly sensitive mapping of lattice perfection and defects. The richness of the observed defects and growth features offers insight into perfection and growth of protein crystals. Beautiful interference fringe patterns formed in diffraction images and fine oscillation structure of rocking curves observed will be discussed for understanding of physical origins and the underlying impact.

  6. Dual-band tunable perfect metamaterial absorber in the THz range.

    PubMed

    Yao, Gang; Ling, Furi; Yue, Jin; Luo, Chunya; Ji, Jie; Yao, Jianquan

    2016-01-25

    In this paper, a dual-band perfect absorber, composed of a periodically patterned elliptical nanodisk graphene structure and a metal ground plane spaced by a thin SiO(2) dielectric layer, is proposed and investigated. Numerical results reveal that the absorption spectrum of the graphene-based structure displays two perfect absorption peaks in the terahertz band, corresponding to the absorption value of 99% at 35μm and 97%at 59μm, respectively. And the resonance frequency of the absorber can be tunned by controlling the Fermi level of graphene layer. Further more, it is insensitive to the polarization and remains very high over a wide angular range of incidence around ±60(0). Compared with the previous graphene dual-band perfect absorption, our absorber only has one shape which can greatly simplify the manufacturing process.

  7. The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero.

    PubMed

    Zhang, G; Stillinger, F H; Torquato, S

    2016-11-28

    Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a "perfect glass". A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite.

  8. The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Stillinger, F. H.; Torquato, S.

    2016-11-01

    Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a “perfect glass”. A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite.

  9. The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero

    PubMed Central

    Zhang, G.; Stillinger, F. H.; Torquato, S.

    2016-01-01

    Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a “perfect glass”. A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite. PMID:27892452

  10. Metamaterial perfect absorber based hot electron photodetection.

    PubMed

    Li, Wei; Valentine, Jason

    2014-06-11

    While the nonradiative decay of surface plasmons was once thought to be only a parasitic process that limits the performance of plasmonic devices, it has recently been shown that it can be harnessed in the form of hot electrons for use in photocatalysis, photovoltaics, and photodetectors. Unfortunately, the quantum efficiency of hot electron devices remains low due to poor electron injection and in some cases low optical absorption. Here, we demonstrate how metamaterial perfect absorbers can be used to achieve near-unity optical absorption using ultrathin plasmonic nanostructures with thicknesses of 15 nm, smaller than the hot electron diffusion length. By integrating the metamaterial with a silicon substrate, we experimentally demonstrate a broadband and omnidirectional hot electron photodetector with a photoresponsivity that is among the highest yet reported. We also show how the spectral bandwidth and polarization-sensitivity can be manipulated through engineering the geometry of the metamaterial unit cell. These perfect absorber photodetectors could open a pathway for enhancing hot electron based photovoltaic, sensing, and photocatalysis systems.

  11. Achieving global perfect homeostasis through transporter regulation

    PubMed Central

    Springer, Michael

    2017-01-01

    Nutrient homeostasis—the maintenance of relatively constant internal nutrient concentrations in fluctuating external environments—is essential to the survival of most organisms. Transcriptional regulation of plasma membrane transporters by internal nutrient concentrations is typically assumed to be the main mechanism by which homeostasis is achieved. While this mechanism is homeostatic we show that it does not achieve global perfect homeostasis—a condition where internal nutrient concentrations are completely independent of external nutrient concentrations for all external nutrient concentrations. We show that the criterion for global perfect homeostasis is that transporter levels must be inversely proportional to net nutrient flux into the cell and that downregulation of active transporters (activity-dependent regulation) is a simple and biologically plausible mechanism that meets this criterion. Activity-dependent transporter regulation creates a trade-off between robustness and efficiency, i.e., the system's ability to withstand perturbation in external nutrients and the transporter production rate needed to maintain homeostasis. Additionally, we show that a system that utilizes both activity-dependent transporter downregulation and regulation of transporter synthesis by internal nutrient levels can create a system that mitigates the shortcomings of each of the individual mechanisms. This analysis highlights the utility of activity-dependent regulation in achieving homeostasis and calls for a re-examination of the mechanisms of regulation of other homeostatic systems. PMID:28414718

  12. Predicting perfect adaptation motifs in reaction kinetic networks.

    PubMed

    Drengstig, Tormod; Ueda, Hiroki R; Ruoff, Peter

    2008-12-25

    Adaptation and compensation mechanisms are important to keep organisms fit in a changing environment. "Perfect adaptation" describes an organism's response to an external stepwise perturbation by resetting some of its variables precisely to their original preperturbation values. Examples of perfect adaptation are found in bacterial chemotaxis, photoreceptor responses, or MAP kinase activities. Two concepts have evolved for how perfect adaptation may be understood. In one approach, so-called "robust perfect adaptation", the adaptation is a network property (due to integral feedback control), which is independent of rate constant values. In the other approach, which we have termed "nonrobust perfect adaptation", a fine-tuning of rate constant values is needed to show perfect adaptation. Although integral feedback describes robust perfect adaptation in general terms, it does not directly show where in a network perfect adaptation may be observed. Using control theoretic methods, we are able to predict robust perfect adaptation sites within reaction kinetic networks and show that a prerequisite for robust perfect adaptation is that the network is open and irreversible. We applied the method on various reaction schemes and found that new (robust) perfect adaptation motifs emerge when considering suggested models of bacterial and eukaryotic chemotaxis.

  13. Power drainage and energy dissipation in lossy but perfect lenses

    NASA Astrophysics Data System (ADS)

    Rosenblatt, Gilad; Orenstein, Meir

    2017-05-01

    It has recently been shown that passive lens designs can retain perfect lensing despite intrinsic loss in the comprising left-handed materials. Here we show that energy conservation is not at odds with the operation of such lossy perfect lenses: The irreversible transfer of electromagnetic power to the lossy material dictates that a smaller portion of the power emitted by the source arrives at the image, but image fidelity remains absolute. Moreover, the power that does arrive at the perfect image must drain from the system there. This is shown to apply to any layered perfect lens based on left-handed media, including the well-known Veselago lens. Combined with what is known about Maxwell's fisheye lens, our results suggest that power drainage is universal to all perfect lenses and is intrinsic to any perfect image. Properly addressing this unique power dynamics is therefore essential to any successful realization of practical perfect lenses with existing metamaterials.

  14. Compressible inviscid instability of rapidly expanding spherical material interfaces

    NASA Astrophysics Data System (ADS)

    Mankbadi, Mina R.; Balachandar, S.

    2012-03-01

    A high-order weighted essentially non-oscillatory scheme is employed to investigate the stability of a rapidly expanding material interface produced by a spherical shock tube. The flow structure is characterized by a forward moving primary shock, a backward moving secondary shock, and a spherical contact interface in-between. We consider herein the linear inviscid regime and focus on the development of the three-dimensional perturbations around the contact interface by solving a one-dimensional system of partial differential equations. Numerical simulations are performed to illustrate the effects of the contact interface's density discontinuity on the growth of the disturbances for various spherical wave numbers. In a spherical shock tube the instability is influenced by various mechanisms which include classical Rayleigh-Taylor (RT) effects, Bell-Plesset or geometry/curvature effects, the effects of impulsively accelerating the interface, and compressibility effects. Henceforth, the present instability will be referred to as non-classical RT instability to distinguish it from classical RT instability. For an extended intermediate time period, it can be shown that the small disturbances grow exponentially as in the classical RT instability. During this stage, the exponential growth rate increases with the spherical wave number, until it saturates for very large wave numbers due to the finite thickness limitation of the numerical representation of the contact interface. The results compare favorably with previous theoretical models; but indicate that in addition to compressibility, the space-time evolution of the contact interface's thickness plays a significant role. A parametric study is performed that varies the pressure and density ratios of the initial spherical container. The characteristics of the contact interface and the applicability of various instability theories is investigated for these regimes. Furthermore, varying the pressure and density ratios aids

  15. A Spherical Aerial Terrestrial Robot

    NASA Astrophysics Data System (ADS)

    Dudley, Christopher J.

    This thesis focuses on the design of a novel, ultra-lightweight spherical aerial terrestrial robot (ATR). The ATR has the ability to fly through the air or roll on the ground, for applications that include search and rescue, mapping, surveillance, environmental sensing, and entertainment. The design centers around a micro-quadcopter encased in a lightweight spherical exoskeleton that can rotate about the quadcopter. The spherical exoskeleton offers agile ground locomotion while maintaining characteristics of a basic aerial robot in flying mode. A model of the system dynamics for both modes of locomotion is presented and utilized in simulations to generate potential trajectories for aerial and terrestrial locomotion. Details of the quadcopter and exoskeleton design and fabrication are discussed, including the robot's turning characteristic over ground and the spring-steel exoskeleton with carbon fiber axle. The capabilities of the ATR are experimentally tested and are in good agreement with model-simulated performance. An energy analysis is presented to validate the overall efficiency of the robot in both modes of locomotion. Experimentally-supported estimates show that the ATR can roll along the ground for over 12 minutes and cover the distance of 1.7 km, or it can fly for 4.82 minutes and travel 469 m, on a single 350 mAh battery. Compared to a traditional flying-only robot, the ATR traveling over the same distance in rolling mode is 2.63-times more efficient, and in flying mode the system is only 39 percent less efficient. Experimental results also demonstrate the ATR's transition from rolling to flying mode.

  16. Physics of Spherical Torus Plasmas

    SciTech Connect

    Peng, Yueng Kay Martin

    2000-01-01

    Broad and important progress in plasma tests, theory, new experiments, and future visions of the spherical torus (ST, or very low aspect ratio tokamaks) have recently emerged. These have substantially improved our understanding of the potential properties of the ST plasmas, since the preliminary calculation of the ST magnetohydrodynamic equilibria more than a decade ago. Exciting data have been obtained from concept exploration level ST experiments of modest capabilities (with major radii up to 35 cm), making important scientific contributions to toroidal confinement in general. The results have helped approval and construction of new and/or more powerful ST experiments, and stimulated an increasing number of theoretical calculations of interest to magnetic fusion energy. Utilizing the broad knowledge base from the successful tokamak and advanced tokamak research, a wide range of new ST physics features has been suggested. These properties of the ST plasma will be tested at the 1 MA level with major radius up to similar to 80 cm in the new proof of principle devices National Spherical Torus Experiment (NSTX, U.S.) [M. Peng , European Conf. Abst. 22C, 451 (1998); S. M. Kaye , Fusion Technol. 36, 16 (1999); M. Ono , "Exploration of Spherical Torus Physics in the NSTX Device," 17th IAEA Fusion Energy Conf., paper IAEA-CN-69/ICP/01 (R), Yokohama, Japan (1998)], Mega Ampere Spherical Tokamak (MAST, U.K.) [A. C. Darke , Fusion Technol. 1, 799 (1995); Q. W. Morris , Proc. Int. Workshop on ST (Ioffe Inst., St. Petersburg, 1997), Vol. 1, p. 290], and Globus-M (R.F.) [V. K. Gusev , European Conf. Abst. 22C, 576 (1998)], which have just started full experimental operation. New concept exploration experiments, such as Pegasus (University of Wisconsin) [R. Fonck and the PEGASUS Team, Bull. Am. Phys. Soc. 44, 267 (1999)], Helicity Injected Tokamak-II (HIT-II, University of Washington) [T. R. Jarboe , Phys. Plasmas 5, 1807 (1998)], and Current Drive Experiment-Upgrade (CDX

  17. Electronic switching spherical array antenna

    NASA Technical Reports Server (NTRS)

    Stockton, R.

    1978-01-01

    This work was conducted to demonstrate the performance levels attainable with an ESSA (Electronic Switching Spherical Array) antenna by designing and testing an engineering model. The antenna was designed to satisfy general spacecraft environmental requirements and built to provide electronically commandable beam pointing capability throughout a hemisphere. Constant gain and beam shape throughout large volumetric coverage regions are the principle characteristics. The model is intended to be a prototype of a standard communications and data handling antenna for user scientific spacecraft with the Tracking and Data Relay Satellite System (TDRSS). Some additional testing was conducted to determine the feasibility of an integrated TDRSS and GPS (Global Positioning System) antenna system.

  18. APPARATUS FOR GRINDING SPHERICAL BODIES

    DOEpatents

    Burch, R.F. Jr.

    1963-09-24

    A relatively inexpensive device is described for grinding rough ceramic bodies into accurate spherical shapes using a conventional drill press and a belt sander. A horizontal disk with an abrasive-surfaced recess in its lower face is mounted eccentrically on a vertical shaft which is forced downward against a stop by a spring. Bodies to be ground are placed in the recess and are subjected to the abrasive action of the belt sander as the disk is rotated by the drill press. (AEC)

  19. Innovative Writing Instruction: Practice Makes Perfect! Realizing Classrooms as "Landscapes of Learning," Not Places of Perfection

    ERIC Educational Resources Information Center

    Ozier, Lance

    2011-01-01

    Pressure for students to produce writing perfection in the classroom often eclipses the emphasis placed on the need for students to practice writing. Occasions for students to choose, challenge, and reflect--to actually risk risking--are too often absent from conversations among students and teachers in countless English classrooms. Tom Romano…

  20. Innovative Writing Instruction: Practice Makes Perfect! Realizing Classrooms as "Landscapes of Learning," Not Places of Perfection

    ERIC Educational Resources Information Center

    Ozier, Lance

    2011-01-01

    Pressure for students to produce writing perfection in the classroom often eclipses the emphasis placed on the need for students to practice writing. Occasions for students to choose, challenge, and reflect--to actually risk risking--are too often absent from conversations among students and teachers in countless English classrooms. Tom Romano…

  1. The simple perfection of quantum correlation in human vision.

    PubMed

    Bouman, Maarten A

    2006-01-01

    A theory is presented that specifies the amount of light that is needed for the perception of any stimulus that is defined in space, time and color. For detection and discrimination mechanistic neural elements with deterministic procedures exist. Twin pairs of red and green cones are ordered in three sets along clockwise and counter clockwise revolving spirals and along circles around the center of the fovea. In the rod-free fovea the red pairs are ordered along the spirals and the green along the circles. Each cone is accompanied by--dependent on retinal eccentricity--up to 100 satellite rods. For the retinal signal processing such a receptor group constitutes a space-quantum in analogy with time-quanta of about 0.04 s. In the peripheral retina the red and green twin pairs of space-quanta are roughly ordered along and at random distributed over the spirals and circles. Over each time-quantum, the cone and rods of a space-quantum sum their responses in a common nerve circuit of the luminosity channel. The summation's results from twin pairs of the same set of space-quanta are correlated by two-fold spatio-temporal coincidence mechanisms in the retina. Their outcome signals the perception of light, movement and edge. In the fused binocular visual field the movement and edge signals of the three sets from both eyes perfectly join vectorially together, provided the responding pairs of space-quanta are binocularly in perfect register as they normally are. The receptor's Weber gain control makes the receptor an all-or-none-system. The space-quantum's De Vries gain control makes its sensitivity equal to the average of the poisson fluctuations in quantum absorption per time-quantum. The controls are based on, respectively, arithmetically feed forward and backward inhibitive nerve mechanisms. The thermal noise of the photo-pigment resets the controls. The response to the second quantum absorption in a time-quantum in the individual rod, red or green cone has accession to

  2. Spherical gravitational collapse in N dimensions

    SciTech Connect

    Goswami, Rituparno; Joshi, Pankaj S.

    2007-10-15

    We investigate here spherically symmetric gravitational collapse in a space-time with an arbitrary number of dimensions and with a general type I matter field, which is a broad class that includes most of the physically reasonable matter forms. We show that given the initial data for matter in terms of the initial density and pressure profiles at an initial surface t=t{sub i} from which the collapse evolves, there exist the rest of the initial data functions and classes of solutions of Einstein equations which we construct here, such that the space-time evolution goes to a final state which is either a black hole or a naked singularity, depending on the nature of initial data and evolutions chosen, and subject to validity of the weak energy condition. The results are discussed and analyzed in the light of the cosmic censorship hypothesis in black hole physics. The formalism here combines the earlier results on gravitational collapse in four dimensions in a unified treatment. Also the earlier work is generalized to higher-dimensional space-times to allow a study of the effect of the number of dimensions on the possible final outcome of the collapse in terms of either a black hole or naked singularity. No restriction is adopted on the number of dimensions, and other limiting assumptions such as self-similarity of space-time are avoided, in order to keep the treatment general. Our methodology allows us to consider to an extent the genericity and stability aspects related to the occurrence of naked singularities in gravitational collapse.

  3. The relativistic Boltzmann equation on a spherically symmetric gravitational field

    NASA Astrophysics Data System (ADS)

    Takou, Etienne; Ciake Ciake, Fidèle L.

    2017-10-01

    In this paper, we consider the Cauchy problem for the relativistic Boltzmann equation with near vacuum initial data where the distribution function depends on the time, the position and the impulsion. We consider this equation on a spherically symmetric gravitational field spacetime. The collision kernel considered here is for the hard potentials case. We prove the existence of a unique global (in time) mild solution in a suitable weighted space.

  4. Spherical shell model description of deformation and superdeformation

    NASA Astrophysics Data System (ADS)

    Poves, A.; Caurier, E.; Nowacki, F.; Zuker, A.

    2003-04-01

    Large-scale shell model calculations give at present a very accurate and comprehensive description of light and medium-light nuclei, specially when 0hbar ω spaces are adequate. The full pf-shell calculations have made it possible to describe many collective features in an spherical shell model context. Calculations including two major oscillator shells have proven able to describe also superdeformed bands.

  5. TURBULENT DYNAMOS IN SPHERICAL SHELL SEGMENTS OF VARYING GEOMETRICAL EXTENT

    SciTech Connect

    Mitra, Dhrubaditya; Tavakol, Reza; Brandenburg, Axel; Moss, David E-mail: brandenb@nordita.org

    2009-05-20

    We use three-dimensional direct numerical simulations of the helically forced magnetohydrodynamic equations in spherical shell segments in order to study the effects of changes in the geometrical shape and size of the domain on the growth and saturation of large-scale magnetic fields. We inject kinetic energy along with kinetic helicity in spherical domains via helical forcing using Chandrasekhar-Kendall functions. We take perfect conductor boundary conditions for the magnetic field to ensure that no magnetic helicity escapes the domain boundaries. We find dynamo action giving rise to magnetic fields at scales larger than the characteristic scale of the forcing. The magnetic energy exceeds the kinetic energy over dissipative timescales, similar to that seen earlier in Cartesian simulations in periodic boxes. As we increase the size of the domain in the azimuthal direction, we find that the nonlinearly saturated magnetic field organizes itself in long-lived cellular structures with aspect ratios close to unity. These structures tile the domain along the azimuthal direction, thus resulting in very small longitudinally averaged magnetic fields for large domain sizes. The scales of these structures are determined by the smallest scales of the domain, which in our simulations is usually the radial scale. We also find that increasing the meridional extent of the domains produces little qualitative change, except a marginal increase in the large-scale field. We obtain qualitatively similar results in Cartesian domains with similar aspect ratios.

  6. Spherical episodic ejection of material from a young star.

    PubMed

    Torrelles, J M; Patel, N A; Gómez, J F; Ho, P T; Rodríguez, L F; Anglada, G; Garay, G; Greenhill, L; Curiel, S; Cantó, J

    2001-05-17

    The exact processes by which interstellar matter condenses to form young stars are of great interest, in part because they bear on the formation of planets like our own from the material that fails to become part of the star. Theoretical models suggest that ejection of gas during early phases of stellar evolution is a key mechanism for removing excess angular momentum, thereby allowing material to drift inwards towards the star through an accretion disk. Such ejections also limit the mass that can be accumulated by the stellar core. To date, these ejections have been observed to be bipolar and highly collimated, in agreement with theory. Here we report observations at very high angular resolution of the proper motions of an arc of water-vapour masers near a very young, massive star in Cepheus. We find that the arc of masers can be fitted to a circle with an accuracy of one part in a thousand, and that the structure is expanding. Only a sphere will always produce a circle in projection, so our observations strongly suggest that the perfectly spherical ejection of material from this star took place about 33 years earlier. The spherical symmetry of the ejecta and its episodic nature are very surprising in the light of present theories.

  7. Perfect anti-reflection from first principles

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Ho; Q-Han Park

    2013-01-01

    Reducing unwanted reflections through impedance matching, called anti-reflection, has long been an important challenge in optics and electrical engineering. Beyond trial and error optimization, however, a systematic way to realize anti-reflection is still absent. Here, we report the discovery of an analytic solution to this long standing problem. For electromagnetic waves, we find the graded permittivity and permeability that completely remove any given impedance mismatch. We demonstrate that perfect broadband anti-reflection is possible when a dispersive, graded refractive index medium is used for the impedance-matching layer. We also present a design rule for the ultra-thin anti-reflection coating which we confirm experimentally by showing the anti-reflection behavior of an exemplary λ/25-thick coating made of metamaterials. This work opens a new path to anti-reflection applications in optoelectronic device, transmission line and stealth technologies.

  8. Perfect crystals grown from imperfect interfaces

    PubMed Central

    Falub, Claudiu V.; Meduňa, Mojmír; Chrastina, Daniel; Isa, Fabio; Marzegalli, Anna; Kreiliger, Thomas; Taboada, Alfonso G.; Isella, Giovanni; Miglio, Leo; Dommann, Alex; von Känel, Hans

    2013-01-01

    The fabrication of advanced devices increasingly requires materials with different properties to be combined in the form of monolithic heterostructures. In practice this means growing epitaxial semiconductor layers on substrates often greatly differing in lattice parameters and thermal expansion coefficients. With increasing layer thickness the relaxation of misfit and thermal strains may cause dislocations, substrate bowing and even layer cracking. Minimizing these drawbacks is therefore essential for heterostructures based on thick layers to be of any use for device fabrication. Here we prove by scanning X-ray nanodiffraction that mismatched Ge crystals epitaxially grown on deeply patterned Si substrates evolve into perfect structures away from the heavily dislocated interface. We show that relaxing thermal and misfit strains result just in lattice bending and tiny crystal tilts. We may thus expect a new concept in which continuous layers are replaced by quasi-continuous crystal arrays to lead to dramatically improved physical properties. PMID:23880632

  9. Perfect anti-reflection from first principles

    PubMed Central

    Kim, Kyoung-Ho; Q-Han Park

    2013-01-01

    Reducing unwanted reflections through impedance matching, called anti-reflection, has long been an important challenge in optics and electrical engineering. Beyond trial and error optimization, however, a systematic way to realize anti-reflection is still absent. Here, we report the discovery of an analytic solution to this long standing problem. For electromagnetic waves, we find the graded permittivity and permeability that completely remove any given impedance mismatch. We demonstrate that perfect broadband anti-reflection is possible when a dispersive, graded refractive index medium is used for the impedance-matching layer. We also present a design rule for the ultra-thin anti-reflection coating which we confirm experimentally by showing the anti-reflection behavior of an exemplary λ/25-thick coating made of metamaterials. This work opens a new path to anti-reflection applications in optoelectronic device, transmission line and stealth technologies. PMID:23320143

  10. Recent Results from RHIC: The Perfect Liquid

    SciTech Connect

    Westfall, Gary

    2006-07-19

    In the past two years we have witnessed a leap forward in the understanding high temperature, high density, and strongly interacting matter produced in ultra-relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Combining measurements of Au+Au, d+Au, and p+p collisions at energies up to 200 GeV per nucleon pair in the center of mass frame, the four RHIC experimental groups, STAR, PHENIX, PHOBOS, and BRAHMS, have produced impressive experimental evidence for the existence of a new form of matter. In this Colloquium, I will present an overview of recent experimental results from RHIC including evidence for thermalization, hydrodynamic behavior of a perfect fluid, the partonic origin of flow, and jet suppression. These measurements point to the observation of a hot, dense, strongly interacting matter produced in central Au+Au collisions at the highest available energies.

  11. Perfect anti-reflection from first principles.

    PubMed

    Kim, Kyoung-Ho; Park, Q-Han

    2013-01-01

    Reducing unwanted reflections through impedance matching, called anti-reflection, has long been an important challenge in optics and electrical engineering. Beyond trial and error optimization, however, a systematic way to realize anti-reflection is still absent. Here, we report the discovery of an analytic solution to this long standing problem. For electromagnetic waves, we find the graded permittivity and permeability that completely remove any given impedance mismatch. We demonstrate that perfect broadband anti-reflection is possible when a dispersive, graded refractive index medium is used for the impedance-matching layer. We also present a design rule for the ultra-thin anti-reflection coating which we confirm experimentally by showing the anti-reflection behavior of an exemplary λ/25-thick coating made of metamaterials. This work opens a new path to anti-reflection applications in optoelectronic device, transmission line and stealth technologies.

  12. Perfect crystals grown from imperfect interfaces.

    PubMed

    Falub, Claudiu V; Meduňa, Mojmír; Chrastina, Daniel; Isa, Fabio; Marzegalli, Anna; Kreiliger, Thomas; Taboada, Alfonso G; Isella, Giovanni; Miglio, Leo; Dommann, Alex; von Känel, Hans

    2013-01-01

    The fabrication of advanced devices increasingly requires materials with different properties to be combined in the form of monolithic heterostructures. In practice this means growing epitaxial semiconductor layers on substrates often greatly differing in lattice parameters and thermal expansion coefficients. With increasing layer thickness the relaxation of misfit and thermal strains may cause dislocations, substrate bowing and even layer cracking. Minimizing these drawbacks is therefore essential for heterostructures based on thick layers to be of any use for device fabrication. Here we prove by scanning X-ray nanodiffraction that mismatched Ge crystals epitaxially grown on deeply patterned Si substrates evolve into perfect structures away from the heavily dislocated interface. We show that relaxing thermal and misfit strains result just in lattice bending and tiny crystal tilts. We may thus expect a new concept in which continuous layers are replaced by quasi-continuous crystal arrays to lead to dramatically improved physical properties.

  13. LensPerfect Analysis of Abell 1689

    NASA Astrophysics Data System (ADS)

    Coe, Dan A.

    2007-12-01

    I present the first massmap to perfectly reproduce the position of every gravitationally-lensed multiply-imaged galaxy detected to date in ACS images of Abell 1689. This massmap was obtained using a powerful new technique made possible by a recent advance in the field of Mathematics. It is the highest resolution assumption-free Dark Matter massmap to date, with the resolution being limited only by the number of multiple images detected. We detect 8 new multiple image systems and identify multiple knots in individual galaxies to constrain a grand total of 168 knots within 135 multiple images of 42 galaxies. No assumptions are made about mass tracing light, and yet the brightest visible structures in A1689 are reproduced in our massmap, a few with intriguing positional offsets. Our massmap probes radii smaller than that resolvable in current Dark Matter simulations of galaxy clusters. And at these radii, we observe slight deviations from the NFW and Sersic profiles which describe simulated Dark Matter halos so well. While we have demonstrated that our method is able to recover a known input massmap (to limited resolution), further tests are necessary to determine the uncertainties of our mass profile and positions of massive subclumps. I compile the latest weak lensing data from ACS, Subaru, and CFHT, and attempt to fit a single profile, either NFW or Sersic, to both the observed weak and strong lensing. I confirm the finding of most previous authors, that no single profile fits extremely well to both simultaneously. Slight deviations are revealed, with the best fits slightly over-predicting the mass profile at both large and small radius. Our easy-to-use software, called LensPerfect, will be made available soon. This research was supported by the European Commission Marie Curie International Reintegration Grant 017288-BPZ and the PNAYA grant AYA2005-09413-C02.

  14. Acoustic source localization in mixed field using spherical microphone arrays

    NASA Astrophysics Data System (ADS)

    Huang, Qinghua; Wang, Tong

    2014-12-01

    Spherical microphone arrays have been used for source localization in three-dimensional space recently. In this paper, a two-stage algorithm is developed to localize mixed far-field and near-field acoustic sources in free-field environment. In the first stage, an array signal model is constructed in the spherical harmonics domain. The recurrent relation of spherical harmonics is independent of far-field and near-field mode strengths. Therefore, it is used to develop spherical estimating signal parameter via rotational invariance technique (ESPRIT)-like approach to estimate directions of arrival (DOAs) for both far-field and near-field sources. In the second stage, based on the estimated DOAs, simple one-dimensional MUSIC spectrum is exploited to distinguish far-field and near-field sources and estimate the ranges of near-field sources. The proposed algorithm can avoid multidimensional search and parameter pairing. Simulation results demonstrate the good performance for localizing far-field sources, or near-field ones, or mixed field sources.

  15. Wake control with permeable multilayer structures: The spherical symmetry case

    NASA Astrophysics Data System (ADS)

    Bowen, Patrick T.; Smith, David R.; Urzhumov, Yaroslav A.

    2015-12-01

    We explore the possibility of controlling the wake and drag of a spherical object independently of each other, using radial distributions of permeability in the Brinkman-Stokes formalism. By discretizing a graded-permeability shell into discrete, macroscopically homogeneous layers, we are able to sample the entire functional space of spherically-symmetric permeabilities and observe quick convergence to a certain manifold in the wake-drag coordinates. Monte Carlo samplings with 104-105 points have become possible thanks to our new algorithm, which is based on exact analytical solutions for the Stokes flow through an arbitrary multilayer porous sphere. The algorithm is not restricted to the Brinkman-Stokes equation and can be modified to account for other types of scattering problems for spherically-symmetric systems with arbitrary radial complexity. Our main practical finding for Stokes flow is that it is possible to reduce a certain measure of wake of a spherical object without any energy penalty and without active (power-consuming) force generation.

  16. Local Existence of Solutions of Self Gravitating Relativistic Perfect Fluids

    NASA Astrophysics Data System (ADS)

    Brauer, Uwe; Karp, Lavi

    2014-01-01

    This paper deals with the evolution of the Einstein gravitational fields which are coupled to a perfect fluid. We consider the Einstein-Euler system in asymptotically flat spacestimes and therefore use the condition that the energy density might vanish or tend to zero at infinity, and that the pressure is a fractional power of the energy density. In this setting we prove local in time existence, uniqueness and well-posedness of classical solutions. The zero order term of our system contains an expression which might not be a C ∞ function and therefore causes an additional technical difficulty. In order to achieve our goals we use a certain type of weighted Sobolev space of fractional order. In Brauer and Karp (J Diff Eqs 251:1428-1446, 2011) we constructed an initial data set for these of systems in the same type of weighted Sobolev spaces. We obtain the same lower bound for the regularity as Hughes et al. (Arch Ratl Mech Anal 63(3):273-294, 1977) got for the vacuum Einstein equations. However, due to the presence of an equation of state with fractional power, the regularity is bounded from above.

  17. Determination of the Magnetic Moment with Spherical Measurements and Spherical Harmonics Modelling

    NASA Astrophysics Data System (ADS)

    Dumond, O.; Bergé, R.

    2012-05-01

    The magnetic moment of space equipment is a needed input for spacecraft magnetic budgeting. In general, a maximum value is also specified. Most of the time, due to the complexity of the equipment, the accurate determination of this magnetic global dipole moment is not possible by analysis. The magnetic sources that compose an equipment can be numerous and of various natures (actuators, current loops in circuits and wires, components, etc.). An experimental determination of the magnetic moment is then necessary. The basic method of the "6 faces" is not adapted for complex equipment (i.e. composed of several elementary dipoles). Intespace and CNES have experimented in the CNES magnetic test facility a method of determination of the magnetic moment using spherical measurements and spherical harmonics modelling. This method has been validated with simulation results and measurements on an assembly of 3 magnets. This paper will also compare the results obtained with other methods of magnetic moment determination. Another advantage of this method is to allow the measurement close to the equipment and then extrapolate the field at another higher distance.

  18. Theoretical requirements for broadband perfect absorption of acoustic waves by ultra-thin elastic meta-films.

    PubMed

    Duan, Yuetao; Luo, Jie; Wang, Guanghao; Hang, Zhi Hong; Hou, Bo; Li, Jensen; Sheng, Ping; Lai, Yun

    2015-07-17

    We derive and numerically demonstrate that perfect absorption of elastic waves can be achieved in two types of ultra-thin elastic meta-films: one requires a large value of almost pure imaginary effective mass density and a free space boundary, while the other requires a small value of almost pure imaginary effective modulus and a hard wall boundary. When the pure imaginary density or modulus exhibits certain frequency dispersions, the perfect absorption effect becomes broadband, even in the low frequency regime. Through a model analysis, we find that such almost pure imaginary effective mass density with required dispersion for perfect absorption can be achieved by elastic metamaterials with large damping. Our work provides a feasible approach to realize broadband perfect absorption of elastic waves in ultra-thin films.

  19. Theoretical requirements for broadband perfect absorption of acoustic waves by ultra-thin elastic meta-films

    PubMed Central

    Duan, Yuetao; Luo, Jie; Wang, Guanghao; Hang, Zhi Hong; Hou, Bo; Li, Jensen; Sheng, Ping; Lai, Yun

    2015-01-01

    We derive and numerically demonstrate that perfect absorption of elastic waves can be achieved in two types of ultra-thin elastic meta-films: one requires a large value of almost pure imaginary effective mass density and a free space boundary, while the other requires a small value of almost pure imaginary effective modulus and a hard wall boundary. When the pure imaginary density or modulus exhibits certain frequency dispersions, the perfect absorption effect becomes broadband, even in the low frequency regime. Through a model analysis, we find that such almost pure imaginary effective mass density with required dispersion for perfect absorption can be achieved by elastic metamaterials with large damping. Our work provides a feasible approach to realize broadband perfect absorption of elastic waves in ultra-thin films. PMID:26184117

  20. Optimization of spherical facets for parabolic solar concentrators

    NASA Technical Reports Server (NTRS)

    White, J. E.; Erikson, R. J.; Sturgis, J. D.; Elfe, T. B.

    1986-01-01

    Solar concentrator designs which employ deployable hexagonal panels are being developed for space power systems. An offset optical configuration has been developed which offers significant system level advantages over previously proposed collector designs for space applications. Optical analyses have been performed which show offset reflector intercept factors to be only slightly lower than those for symmetric reflectors with the same slope error. Fluxes on the receiver walls are asymmetric but manageable by varying the tilt angle of the receiver. Greater producibility is achieved by subdividing the hexagonal panels into triangular mirror facets of spherical contour. Optical analysis has been performed upon these to yield near-optimum sizes and radii.

  1. Optimization of spherical facets for parabolic solar concentrators

    NASA Technical Reports Server (NTRS)

    White, J. E.; Erikson, R. J.; Sturgis, J. D.; Elfe, T. B.

    1986-01-01

    Solar concentrator designs which employ deployable hexagonal panels are being developed for space power systems. An offset optical configuration has been developed which offers significant system level advantages over previously proposed collector designs for space applications. Optical analyses have been performed which show offset reflector intercept factors to be only slightly lower than those for symmetric reflectors with the same slope error. Fluxes on the receiver walls are asymmetric but manageable by varying the tilt angle of the receiver. Greater producibility is achieved by subdividing the hexagonal panels into triangular mirror facets of spherical contour. Optical analysis has been performed upon these to yield near-optimum sizes and radii.

  2. Let's move to spheres! Why a spherical coordinate system is rewarding when analyzing particle increment statistics

    NASA Astrophysics Data System (ADS)

    Most, Sebastian; Nowak, Wolfgang; Bijeljic, Branko

    2016-04-01

    For understanding non-Fickian transport in porous media, thorough understanding of pore-scale processes is required. When using particle methods as research instruments, we need a detailed understanding of the dependence and memory between subsequent increments in particle motion. We are especially interested in the dependence and memory of the spatial increments (size and direction) at consecutive time steps. Understanding the increment statistics is crucial for the upscaling that always becomes essential for transport simulations at larger scales. Upscaling means averaging over a (representative elementary) volume to save limited computational resources. However, this averaging means a loss of detail and therefore dispersion models should compensate for this loss. Formulating an appropriate dispersion model requires a detailed understanding of the dependencies and memory effects in the transport process. Particle-based simulations for transport in porous media are usually conducted and analyzed in a Cartesian coordinate system. We will show that, for understanding the process physically and representing the process statistically, it is more appropriate to switch to a spherical coordinate system that moves with each particle. Increment statistics in a Cartesian coordinate system usually reveal that a large displacement in longitudinal direction triggers a large displacement in transverse direction as fast flow channels are not perfectly aligned with the Cartesian axis along the main flow direction. We can overcome this inherent link, typical for the Cartesian description by using the absolute displacements together with the direction of the particle movement, where the direction is determined by the angles azimuth and elevation. This can be understood as a Lagrangian spherical process description. The root of the dependence of the transport process is in the complex pore geometry. For some time past, high-resolution micro-CT scans of pore space geometry became the

  3. Archimedes' floating bodies on a spherical Earth

    NASA Astrophysics Data System (ADS)

    Rorres, Chris

    2016-01-01

    Archimedes was the first to systematically find the centers of gravity of various solid bodies and to apply this concept in determining stable configurations of floating bodies. In this paper, we discuss an error in a proof developed by Archimedes that involves determining whether a uniform, spherical cap will float stably with its base horizontal in a liquid on a spherical Earth. We present a simpler, corrected proof and discuss aspects of his proof regarding a spherical cap that is not uniform.

  4. Measuring Spherical Harmonic Coefficients on a Sphere

    SciTech Connect

    Pollaine, S; Haan, S W

    2003-05-16

    The eigenfunctions of Rayleigh-Taylor modes on a spherical capsule are the spherical harmonics Y{sub l,m} These can be measured by measuring the surface perturbations along great circles and fitting them to the first few modes by a procedure described in this article. For higher mode numbers, it is more convenient to average the Fourier power spectra along the great circles, and then transform them to spherical harmonic modes by an algorithm derived here.

  5. Space Shuttle Endeavour launch

    NASA Technical Reports Server (NTRS)

    1992-01-01

    A smooth countdown culminated in a picture-perfect launch as the Space Shuttle Endeavour (STS-47) climbed skyward atop a ladder of billowing smoke. Primary payload for the plarned seven-day flight was Spacelab-J science laboratory. The second flight of Endeavour marks a number of historic firsts: the first space flight of an African-American woman, the first Japanese citizen to fly on a Space Shuttle, and the first married couple to fly in space.

  6. Spherical collapse in chameleon models

    SciTech Connect

    Brax, Ph.; Steer, D.A. E-mail: rosenfel@ift.unesp.br

    2010-08-01

    We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse in principle depends on the initial comoving size of the inhomogeneity.

  7. Nonadiabatic charged spherical gravitational collapse

    SciTech Connect

    Di Prisco, A.; Herrera, L.; Le Denmat, G.; MacCallum, M. A. H.; Santos, N. O.

    2007-09-15

    We present a complete set of the equations and matching conditions required for the description of physically meaningful charged, dissipative, spherically symmetric gravitational collapse with shear. Dissipation is described with both free-streaming and diffusion approximations. The effects of viscosity are also taken into account. The roles of different terms in the dynamical equation are analyzed in detail. The dynamical equation is coupled to a causal transport equation in the context of Israel-Stewart theory. The decrease of the inertial mass density of the fluid, by a factor which depends on its internal thermodynamic state, is reobtained, with the viscosity terms included. In accordance with the equivalence principle, the same decrease factor is obtained for the gravitational force term. The effect of the electric charge on the relation between the Weyl tensor and the inhomogeneity of the energy density is discussed.

  8. Libsharp - spherical harmonic transforms revisited

    NASA Astrophysics Data System (ADS)

    Reinecke, M.; Seljebotn, D. S.

    2013-06-01

    We present libsharp, a code library for spherical harmonic transforms (SHTs), which evolved from the libpsht library and addresses several of its shortcomings, such as adding MPI support for distributed memory systems and SHTs of fields with arbitrary spin, but also supporting new developments in CPU instruction sets like the Advanced Vector Extensions (AVX) or fused multiply-accumulate (FMA) instructions. The library is implemented in portable C99 and provides an interface that can be easily accessed from other programming languages such as C++, Fortran, Python, etc. Generally, libsharp's performance is at least on par with that of its predecessor; however, significant improvements were made to the algorithms for scalar SHTs, which are roughly twice as fast when using the same CPU capabilities. The library is available at http://sourceforge.net/projects/libsharp/ under the terms of the GNU General Public License.

  9. Wormhole dynamics in spherical symmetry

    SciTech Connect

    Hayward, Sean A.

    2009-06-15

    A dynamical theory of traversable wormholes is detailed in spherical symmetry. Generically a wormhole consists of a tunnel of trapped surfaces between two mouths, defined as temporal outer trapping horizons with opposite senses, in mutual causal contact. In static cases, the mouths coincide as the throat of a Morris-Thorne wormhole, with surface gravity providing an invariant measure of the radial curvature or ''flaring-out''. The null energy condition must be violated at a wormhole mouth. Zeroth, first, and second laws are derived for the mouths, as for black holes. Dynamic processes involving wormholes are reviewed, including enlargement or reduction, and interconversion with black holes. A new area of wormhole thermodynamics is suggested.

  10. Spherical Parameterization Balancing Angle and Area Distortions.

    PubMed

    Nadeem, Saad; Su, Zhengyu; Zeng, Wei; Kaufman, Arie; Gu, Xianfeng

    2017-06-01

    This work presents a novel framework for spherical mesh parameterization. An efficient angle-preserving spherical parameterization algorithm is introduced, which is based on dynamic Yamabe flow and the conformal welding method with solid theoretic foundation. An area-preserving spherical parameterization is also discussed, which is based on discrete optimal mass transport theory. Furthermore, a spherical parameterization algorithm, which is based on the polar decomposition method, balancing angle distortion and area distortion is presented. The algorithms are tested on 3D geometric data and the experiments demonstrate the efficiency and efficacy of the proposed methods.

  11. Maximum entropy spherical deconvolution for diffusion MRI.

    PubMed

    Alexander, Daniel C

    2005-01-01

    This paper proposes a maximum entropy method for spherical deconvolution. Spherical deconvolution arises in various inverse problems. This paper uses the method to reconstruct the distribution of microstructural fibre orientations from diffusion MRI measurements. Analysis shows that the PASMRI algorithm, one of the most accurate diffusion MRI reconstruction algorithms in the literature, is a special case of the maximum entropy spherical deconvolution. Experiments compare the new method to linear spherical deconvolution, used previously in diffusion MRI, and to the PASMRI algorithm. The new method compares favourably both in simulation and on standard brain-scan data.

  12. Coherent perfect absorption and reflection in slow-light waveguides.

    PubMed

    Gutman, Nadav; Sukhorukov, Andrey A; Chong, Y D; de Sterke, C Martijn

    2013-12-01

    We identify a family of unusual slow-light modes occurring in lossy multimode grating waveguides, for which either the forward or backward mode components, or both, are degenerate. In the fully degenerate case, the response can be modulated between coherent perfect absorption (zero reflection) and perfect reflection by varying the wave amplitudes in a uniform input waveguide. The perfectly absorbed wave has anomalously short absorption length, scaling as the inverse one-third power of the absorptivity.

  13. Microwave signal amplification and Pierce instability on radial electron flows in cylindrical and spherical diodes

    SciTech Connect

    Gnavi, G.; Gratton, F.T. )

    1994-11-01

    Linear space charge perturbations of focused electron beams flowing between cylindrical and spherical electrodes on convergent or divergent trajectories are studied, and the amplification of high-frequency signals when the flow is modulated at one electrode is computed. It is shown that divergent beams give the largest amplification effect. The instability of electron beams drifting through grounded grids (Pierce instability in cylindrical or spherical diodes) is also considered. The instability threshold occurs at higher critical currents when the curvature of the electrodes is large. Results for planar electrodes are recovered in the limit of zero curvature devices. Spherical configurations have better signal amplification and stability properties than similar planar or cylindrical systems.

  14. Wavefronts, caustics, and ronchigrams of a spherical wave reflected by a spherical mirror.

    PubMed

    Castro-Ramos, Jorge; Marciano-Melchor, Magdalena; Marcelino-Aranda, Mariana; Román-Hernández, Edwin; Santiago-Santiago, José Guadalupe; Silva-Ortigoza, Gilberto; Silva-Ortigoza, Ramón; Suárez-Xique, Román; Zárate-Paz, José Miguel

    2013-02-01

    The aim of the present work is twofold: first we obtain analytical expressions for both the wavefronts and the caustic associated with the light rays reflected by a spherical mirror after being emitted by a point light source located at an arbitrary position in free space, and second, we describe, in detail, the structure of the ronchigrams when the grating or Ronchi ruling is placed at different relative positions to the caustic region and the point light source is located on and off the optical axis. We find that, in general, the caustic has two branches: one is a segment of a line, and the other is a two-dimensional surface. The wavefronts, at the caustic region, have self intersections and singularities. The ronchigrams exhibit closed-loop fringes when the grating is placed at the caustic region.

  15. Fast calculation of computer-generated spherical hologram by spherical harmonic transform

    NASA Astrophysics Data System (ADS)

    Sando, Y.; Barada, D.; Jackin, B. J.; Yatagai, T.

    2017-05-01

    This paper presents a fast calculation method for spherical computer-generated hologram by using a spherical harmonic transform. A three-dimensional (3D) object defined in the 3D Cartesian coordinate system is numerically Fourier transformed with fast Fourier transforms (FFTs). Fourier components on the spherical surface of the radius 1/λ are extracted. The wavefronts on the spherical surface can be calculated from the single spherical Fourier components. This paper reveals the analytical diffraction integral between the spherical Fourier components and the wavefront on the spherical surface. This diffraction integral is expressed in the form of convolution integral on the sphere and can be calculated very fast based on the spherical harmonic transform. By the numerical simulation, the validity and the effectiveness of our proposal has been verified.

  16. Perfect terahertz absorber using fishnet based metafilm

    SciTech Connect

    Azad, Abul Kalam; Shchegolkov, Dmitry Yu; Chen, Houtong; Taylor, Antoinette; Smirnova, E I; O' Hara, John F

    2009-01-01

    We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials with desired values. Although the initial idea of metamaterials was to obtain a negative index medium, however, the evolution of metamaterials (MMs) offers a variety of practically applicable devices for controlling electromagnetic wave such as tunable filters, modulators, phase shifters, compact antenna, absorbers, etc. Terahertz regime, a crucial domain of the electromagnetic wave, is suffering from the scarcity of the efficient devices and might take the advantage of metamaterials. Here, we demonstrate design, fabrication, and characterization of a terahertz absorber based on a simple fishnet metallic film separated from a ground mirror plane by a dielectric spacer. Such absorbers are in particular important for bolometric terahertz detectors, high sensitivity imaging, and terahertz anechoic chambers. Recently, split-ring-resonators (SRR) have been employed for metamaterial-based absorbers at microwave and THz frequencies. The experimental demonstration reveals that such absorbers have absorptivity close to unity at resonance frequencies. However, the downside of these designs is that they all employ resonators of rather complicated shape with many fine parts and so they are not easy to fabricate and are sensitive to distortions.

  17. Hypothesis: A perfect day conveys internal time.

    PubMed

    Groß, J V; Fritschi, L; Erren, T C

    2017-04-01

    In 2007 the International Agency for Research on Cancer [IARC] concluded "shift work that involves circadian disruption is probably carcinogenic to humans" (Group 2A). To investigate the "probable" causal link, information on individual chronobiology is needed to specify exposures to circadian disruption associated with shift work. In epidemiological studies this information is usually assessed by questionnaire. The most widely used Morningness-Eveningness-Questionnaire (MEQ) and MunichChronoTypeQuestionnaire (MCTQ) reveal information on circadian type (MEQ) and actual sleep behaviour (MCTQ). As a further option we suggest to obtain preferred sleep times by using what we call the perfect day (PD) approach. We hypothesize that a PD - as a day of completely preferred sleep behaviour - captures pristine internal time. We argue that the PD approach may measure internal time more accurately than the MEQ and MCTQ which convey influences by work and social time pressures. The PD approach may therefore reduce misclassifications of internal time and reveal circadian disruption caused by different shift systems.

  18. Natural melting within a spherical shell

    NASA Technical Reports Server (NTRS)

    Bahrami, Parviz A.

    1990-01-01

    Fundamental heat transfer experiments were performed on the melting of a phase change medium in a spherical shell. Free expansion of the medium into a void space within the sphere was permitted. A step function temperature jump on the outer shell wall was imposed and the timewise evolution of the melting process and the position of the solid-liquid interface was photographically recorded. Numerical integration of the interface position data yielded information about the melted mass and the energy of melting. It was found that the rate of melting and the heat transfer were significantly affected by the movement of the solid medium to the base of the sphere due to gravity. The energy transfer associated with melting was substantially higher than that predicted by the conduction model. Furthermore, the radio of the measured values of sensible energy in the liquid melt to the energy of melting were nearly proportional to the Stefan number. The experimental results are in agreement with a theory set forth in an earlier paper.

  19. Spherically symmetric solutions of the λ -R model

    NASA Astrophysics Data System (ADS)

    Loll, R.; Pires, L.

    2017-08-01

    We derive spherically symmetric solutions of the classical λ -R model, a minimal, anisotropic modification of general relativity with a preferred foliation and two local degrees of freedom. Starting from a 3 +1 decomposition of the four-metric in a general spherically symmetric ansatz, we perform a phase space analysis of the reduced model. We show that its constraint algebra is consistent with that of the full λ -R model, and also yields a constant mean curvature or maximal slicing condition as a tertiary constraint. Although the solutions contain the standard Schwarzschild geometry for the general relativistic value λ =1 or for vanishing mean extrinsic curvature K , they are in general nonstatic, incompatible with asymptotic flatness, and parametrized not only by a conserved mass. We show by explicit computation that the four-dimensional Ricci scalar of the solutions is in general time dependent and nonvanishing.

  20. A prototype spherical array for interior noise investigations

    NASA Astrophysics Data System (ADS)

    Williams, Earl G.; Houston, Brian H.; Herdic, Peter C.

    2002-11-01

    A spherical array of radius 0.2 m with 18 uniformly distributed microphone elements on a spherical surface has been constructed. Using the theory of nearfield acoustical holography the instantaneous pressure, velocity, and intensity fields are reconstructed throughout a volume of 0.6 m radius centered at the array origin in the frequency range of 0-600 Hz. Since the measurements are instantaneous the array is intended to be used to measure distributed sources that need not be coherent or stationary, ideally suited for source identification in the interior of an in-flight aircraft, an automobile or in interior spaces in naval vessels. Preliminary experiments with a loudspeaker demonstrate the accuracy of the volume-field reconstruction of the instantaneous fields. This array is a prototype of an array with many more elements which will have a wider frequency range and finer spatial resolution. [Work supported by NASA and ONR.

  1. The inverse spatial Laplacian of spherically symmetric spacetimes

    NASA Astrophysics Data System (ADS)

    Fernandes, Karan; Lahiri, Amitabha

    2017-09-01

    We derive the inverse spatial Laplacian for static, spherically symmetric backgrounds by solving Poisson’s equation for a point source. This is different from the electrostatic Green function, which is defined on the four dimensional static spacetime, while the equation we consider is defined on the spatial hypersurface of such spacetimes. This Green function is relevant in the Hamiltonian dynamics of theories defined on spherically symmetric backgrounds, and closed form expressions for the solutions we find are absent in the literature. We derive an expression in terms of elementary functions for the Schwarzschild spacetime, and comment on the relation of this solution with the known Green function of the spacetime Laplacian operator. We also find an expression for the Green function on the static pure de-Sitter space in terms of hypergeometric functions. We conclude with a discussion of the constraints of the electromagnetic field.

  2. Light-weight spherical submergence vessel

    NASA Technical Reports Server (NTRS)

    Baker, I.

    1974-01-01

    Design vessel with very low thickness-to-radius ratio to obtain low weight, and fabricate it with aid of precision tracer-lathe to limit and control imperfections in spherical shape. Vessel is thin-walled, spherical, monocoque shell constructed from hemispheres joined with sealed and bolted meridional flange.

  3. How Spherical Is a Cube (Gravitationally)?

    ERIC Educational Resources Information Center

    Sanny, Jeff; Smith, David

    2015-01-01

    An important concept that is presented in the discussion of Newton's law of universal gravitation is that the gravitational effect external to a spherically symmetric mass distribution is the same as if all of the mass of the distribution were concentrated at the center. By integrating over ring elements of a spherical shell, we show that the…

  4. Onthe static and spherically symmetric gravitational field

    NASA Astrophysics Data System (ADS)

    Gottlieb, Ioan; Maftei, Gheorghe; Mociutchi, Cleopatra

    Starting from a generalization of Einstein 's theory of gravitation, proposed by one of the authors (Cleopatra Mociutchi), the authors study a particular spherical symmetric case. Among other one obtain the compatibility conditions for the existence of the static and spherically symmetruic gravitational filed in the case of extended Einstein equation.

  5. How Spherical Is a Cube (Gravitationally)?

    ERIC Educational Resources Information Center

    Sanny, Jeff; Smith, David

    2015-01-01

    An important concept that is presented in the discussion of Newton's law of universal gravitation is that the gravitational effect external to a spherically symmetric mass distribution is the same as if all of the mass of the distribution were concentrated at the center. By integrating over ring elements of a spherical shell, we show that the…

  6. Spherical combustion clouds in explosions

    NASA Astrophysics Data System (ADS)

    Kuhl, A. L.; Bell, J. B.; Beckner, V. E.; Balakrishnan, K.; Aspden, A. J.

    2013-05-01

    This study explores the properties of spherical combustion clouds in explosions. Two cases are investigated: (1) detonation of a TNT charge and combustion of its detonation products with air, and (2) shock dispersion of aluminum powder and its combustion with air. The evolution of the blast wave and ensuing combustion cloud dynamics are studied via numerical simulations with our adaptive mesh refinement combustion code. The code solves the multi-phase conservation laws for a dilute heterogeneous continuum as formulated by Nigmatulin. Single-phase combustion (e.g., TNT with air) is modeled in the fast-chemistry limit. Two-phase combustion (e.g., Al powder with air) uses an induction time model based on Arrhenius fits to Boiko's shock tube data, along with an ignition temperature criterion based on fits to Gurevich's data, and an ignition probability model that accounts for multi-particle effects on cloud ignition. Equations of state are based on polynomial fits to thermodynamic calculations with the Cheetah code, assuming frozen reactants and equilibrium products. Adaptive mesh refinement is used to resolve thin reaction zones and capture the energy-bearing scales of turbulence on the computational mesh (ILES approach). Taking advantage of the symmetry of the problem, azimuthal averaging was used to extract the mean and rms fluctuations from the numerical solution, including: thermodynamic profiles, kinematic profiles, and reaction-zone profiles across the combustion cloud. Fuel consumption was limited to ˜ 60-70 %, due to the limited amount of air a spherical combustion cloud can entrain before the turbulent velocity field decays away. Turbulent kinetic energy spectra of the solution were found to have both rotational and dilatational components, due to compressibility effects. The dilatational component was typically about 1 % of the rotational component; both seemed to preserve their spectra as they decayed. Kinetic energy of the blast wave decayed due to the

  7. Sound Source Localization Using Non-Conformal Surface Sound Field Transformation Based on Spherical Harmonic Wave Decomposition

    PubMed Central

    Zhang, Lanyue; Ding, Dandan; Yang, Desen; Wang, Jia; Shi, Jie

    2017-01-01

    Spherical microphone arrays have been paid increasing attention for their ability to locate a sound source with arbitrary incident angle in three-dimensional space. Low-frequency sound sources are usually located by using spherical near-field acoustic holography. The reconstruction surface and holography surface are conformal surfaces in the conventional sound field transformation based on generalized Fourier transform. When the sound source is on the cylindrical surface, it is difficult to locate by using spherical surface conformal transform. The non-conformal sound field transformation by making a transfer matrix based on spherical harmonic wave decomposition is proposed in this paper, which can achieve the transformation of a spherical surface into a cylindrical surface by using spherical array data. The theoretical expressions of the proposed method are deduced, and the performance of the method is simulated. Moreover, the experiment of sound source localization by using a spherical array with randomly and uniformly distributed elements is carried out. Results show that the non-conformal surface sound field transformation from a spherical surface to a cylindrical surface is realized by using the proposed method. The localization deviation is around 0.01 m, and the resolution is around 0.3 m. The application of the spherical array is extended, and the localization ability of the spherical array is improved. PMID:28489065

  8. Sound Source Localization Using Non-Conformal Surface Sound Field Transformation Based on Spherical Harmonic Wave Decomposition.

    PubMed

    Zhang, Lanyue; Ding, Dandan; Yang, Desen; Wang, Jia; Shi, Jie

    2017-05-10

    Spherical microphone arrays have been paid increasing attention for their ability to locate a sound source with arbitrary incident angle in three-dimensional space. Low-frequency sound sources are usually located by using spherical near-field acoustic holography. The reconstruction surface and holography surface are conformal surfaces in the conventional sound field transformation based on generalized Fourier transform. When the sound source is on the cylindrical surface, it is difficult to locate by using spherical surface conformal transform. The non-conformal sound field transformation by making a transfer matrix based on spherical harmonic wave decomposition is proposed in this paper, which can achieve the transformation of a spherical surface into a cylindrical surface by using spherical array data. The theoretical expressions of the proposed method are deduced, and the performance of the method is simulated. Moreover, the experiment of sound source localization by using a spherical array with randomly and uniformly distributed elements is carried out. Results show that the non-conformal surface sound field transformation from a spherical surface to a cylindrical surface is realized by using the proposed method. The localization deviation is around 0.01 m, and the resolution is around 0.3 m. The application of the spherical array is extended, and the localization ability of the spherical array is improved.

  9. Electrostatic spherically symmetric configurations in gravitating nonlinear electrodynamics

    SciTech Connect

    Diaz-Alonso, J.; Rubiera-Garcia, D.

    2010-03-15

    We perform a study of the gravitating electrostatic spherically symmetric (G-ESS) solutions of Einstein field equations minimally coupled to generalized nonlinear Abelian gauge models in three space dimensions. These models are defined by Lagrangian densities which are general functions of the gauge field invariants, restricted by some physical conditions of admissibility. They include the class of nonlinear electrodynamics supporting electrostatic spherically symmetric (ESS) nontopological soliton solutions in absence of gravity. We establish that the qualitative structure of the G-ESS solutions of admissible models is fully characterized by the asymptotic and central-field behaviors of their ESS solutions in flat space (or, equivalently, by the behavior of the Lagrangian densities in vacuum and on the point of the boundary of their domain of definition, where the second gauge invariant vanishes). The structure of these G-ESS configurations for admissible models supporting divergent-energy ESS solutions in flat space is qualitatively the same as in the Reissner-Nordstroem case. In contrast, the G-ESS configurations of the models supporting finite-energy ESS solutions in flat space exhibit new qualitative features, which are discussed in terms of the Arnowitt-Deser-Misner mass, the charge, and the soliton energy. Most of the results concerning well-known models, such as the electrodynamics of Maxwell, Born-Infeld, and the Euler-Heisenberg effective Lagrangian of QED, minimally coupled to gravitation, are shown to be corollaries of general statements of this analysis.

  10. A complete analytical solution for the inverse instantaneous kinematics of a spherical-revolute-spherical (7R) redundant manipulator

    NASA Technical Reports Server (NTRS)

    Podhorodeski, R. P.; Fenton, R. G.; Goldenberg, A. A.

    1989-01-01

    Using a method based upon resolving joint velocities using reciprocal screw quantities, compact analytical expressions are generated for the inverse solution of the joint rates of a seven revolute (spherical-revolute-spherical) manipulator. The method uses a sequential decomposition of screw coordinates to identify reciprocal screw quantities used in the resolution of a particular joint rate solution, and also to identify a Jacobian null-space basis used for the direct solution of optimal joint rates. The results of the screw decomposition are used to study special configurations of the manipulator, generating expressions for the inverse velocity solution for all non-singular configurations of the manipulator, and identifying singular configurations and their characteristics. Two functions are therefore served: a new general method for the solution of the inverse velocity problem is presented; and complete analytical expressions are derived for the resolution of the joint rates of a seven degree of freedom manipulator useful for telerobotic and industrial robotic application.

  11. Wrinkling crystallography on spherical surfaces.

    PubMed

    Brojan, Miha; Terwagne, Denis; Lagrange, Romain; Reis, Pedro M

    2015-01-06

    We present the results of an experimental investigation on the crystallography of the dimpled patterns obtained through wrinkling of a curved elastic system. Our macroscopic samples comprise a thin hemispherical shell bound to an equally curved compliant substrate. Under compression, a crystalline pattern of dimples self-organizes on the surface of the shell. Stresses are relaxed by both out-of-surface buckling and the emergence of defects in the quasi-hexagonal pattern. Three-dimensional scanning is used to digitize the topography. Regarding the dimples as point-like packing units produces spherical Voronoi tessellations with cells that are polydisperse and distorted, away from their regular shapes. We analyze the structure of crystalline defects, as a function of system size. Disclinations are observed and, above a threshold value, dislocations proliferate rapidly with system size. Our samples exhibit striking similarities with other curved crystals of charged particles and colloids. Differences are also found and attributed to the far-from-equilibrium nature of our patterns due to the random and initially frozen material imperfections which act as nucleation points, the presence of a physical boundary which represents an additional source of stress, and the inability of dimples to rearrange during crystallization. Even if we do not have access to the exact form of the interdimple interaction, our experiments suggest a broader generality of previous results of curved crystallography and their robustness on the details of the interaction potential. Furthermore, our findings open the door to future studies on curved crystals far from equilibrium.

  12. Nanophotonics of isolated spherical particles

    NASA Astrophysics Data System (ADS)

    Geints, Yu. É.; Zemlyanov, A. A.; Panina, E. K.

    2010-09-01

    The problem of extreme focusing of an optical beam into the spatial region with wavelength dimensions is considered with the use of the special features of radiation interaction with isolated spherical particles. Results of numerical computations of the optical field intensity at the surface of silver particles of different radii upon exposure to laser radiation with different wavelengths are presented. It is demonstrated that the relative intensity of the plasmon optical field on the nanoparticle surface increases and the field focusing region decreases with increasing particle radius. Results of numerical computations illustrating the influence of the shell of composite nanoparticles comprising a dielectric core and a metal shell on the optical field intensity in the vicinity of the particle are presented. The problem of local optical foci of a transparent microparticle (photonic nanojets) is investigated. It is established that variation of the micron particle size, its optical properties, and laser radiation parameters allows the amplitude and spatial characteristics of the photonic nanojet region to be controlled efficiently.

  13. Ribozyme-Spherical Nucleic Acids

    PubMed Central

    Hao, Liangliang; Kouri, Fotini M.; Briley, William E.; Stegh, Alexander H.; Mirkin, Chad A.

    2015-01-01

    Ribozymes are highly structured RNA sequences that can be tailored to recognize and cleave specific stretches of mRNA. Their current therapeutic efficacy remains low due to their large size and structural instability compared to shorter therapeutically relevant RNA such as small interfering RNA (siRNA) and microRNA (miRNA). Herein, a synthetic strategy that makes use of the spherical nucleic acid (SNA) architecture to stabilize ribozymes and transfect them into live cells is reported. The properties of this novel ribozyme SNA are characterized in the context of the targeted knockdown of O6-methylguanine-DNA methyltransferase (MGMT), a DNA repair protein involved in chemotherapeutic resistance of solid tumors, foremost glioblastoma multiforme (GBM). Data showing the direct cleavage of full-length MGMT mRNA, knockdown of MGMT protein, and increased sensitization of GBM cells to therapy-mediated apoptosis, independent of transfection agents, provide compelling evidence for the promising properties of this new chemical architecture. PMID:26271335

  14. Study on Octahedral Spherical Hohlraum

    NASA Astrophysics Data System (ADS)

    Lan, Ke; Liu, Jie; Huo, Wenyi; Li, Zhichao; Yang, Dong; Li, Sanwei; Ren, Guoli; Chen, Yaohua; Jiang, Shaoen; He, Xian-Tu; Zhang, Weiyan

    2015-11-01

    In this talk, we report our recent study on octahedral spherical hohlraum which has six laser entrance holes (LEHs). First, our study shows that the octahedral hohlraums have robust high symmetry during the capsule implosion at hohlraum-to- capsule radius ratio larger than 3.7 and have potential superiority on low backscatter without supplementary technology. Second, we study the laser arrangement and constraints of the octahedral hohlraums and give their laser arrangement design for ignition facility. Third, we propose a novel octahedral hohlraum with LEH shields and cylindrical LEHs, in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport. Fourth, we study the sensitivity of capsule symmetry inside the octahedral hohlraums to laser power balance, pointing accuracy, deviations from the optimal position and target fabrication accuracy, and compare the results with that of tradiational cylinders and rugby hohlraums. Finally, we present our recent experimental studies on the octahedral hohlraums on SGIII prototype laser facility.

  15. Osmotic buckling of spherical capsules.

    PubMed

    Knoche, Sebastian; Kierfeld, Jan

    2014-11-07

    We study the buckling of elastic spherical shells under osmotic pressure with the osmolyte concentration of the exterior solution as a control parameter. We compare our results for the bifurcation behavior with results for buckling under mechanical pressure control, that is, with an empty capsule interior. We find striking differences for the buckling states between osmotic and mechanical buckling. Mechanical pressure control always leads to fully collapsed states with opposite sides in contact, whereas uncollapsed states with a single finite dimple are generic for osmotic pressure control. For sufficiently large interior osmolyte concentrations, osmotic pressure control is qualitatively similar to buckling under volume control with the volume prescribed by the osmolyte concentrations inside and outside the shell. We present a quantitative theory which also captures the influence of shell elasticity on the relationship between osmotic pressure and volume. These findings are relevant for the control of buckled shapes in applications. We show how the osmolyte concentration can be used to control the volume of buckled shells. An accurate analytical formula is derived for the relationship between the osmotic pressure, the elastic moduli and the volume of buckled capsules. This also allows use of elastic capsules as osmotic pressure sensors or deduction of elastic properties and the internal osmolyte concentration from shape changes in response to osmotic pressure changes. We apply our findings to published experimental data on polyelectrolyte capsules.

  16. Chemical waves on spherical surfaces

    NASA Astrophysics Data System (ADS)

    Maselko, Jerzy; Showalter, Kenneth

    1989-06-01

    THE concentric-circular and spiral patterns exhibited by the Belousov-Zhabotinsky (BZ) reaction in thin films of solution are representative of spatiotemporal behaviour in a two-dimensional, planar excitable medium1-6. Here we report BZ chemical waves propagating on the two-dimensional surface of a sphere. A wave on the surface of a single cation-exchange bead, loaded with ferroin and bathed in BZ reaction mixture containing no catalyst, develops to form a rotating spiral. Unlike spiral waves in thin films of solution, which typically wind out to connect with a twin rotating in the opposite direction, these waves rotate from pole to pole in a single direction. The spiral winds outward from a meandering source at one pole, crosses the equator, and undergoes self-annihilation as it winds into itself at the other pole. This behaviour, which is not possible in a two-dimensional planar configuration, arises from qualitative (negative to positive) and quantitative changes in wavefront curvature as the wave traverses the spherical surface. These observations of a single spiral wave contrast with theoretical predictions7,8 of counter-rotating spirals in this geometry.

  17. A multiband perfect absorber based on hyperbolic metamaterials.

    PubMed

    Sreekanth, Kandammathe Valiyaveedu; ElKabbash, Mohamed; Alapan, Yunus; Rashed, Alireza R; Gurkan, Umut A; Strangi, Giuseppe

    2016-05-18

    In recent years, considerable research efforts have been focused on near-perfect and perfect light absorption using metamaterials spanning frequency ranges from microwaves to visible frequencies. This relatively young field is currently facing many challenges that hampers its possible practical applications. In this paper, we present grating coupled-hyperbolic metamaterials (GC-HMM) as multiband perfect absorber that can offer extremely high flexibility in engineering the properties of electromagnetic absorption. The fabricated GC-HMMs exhibit several highly desirable features for technological applications such as polarization independence, wide angle range, broad- and narrow- band modes, multiband perfect and near perfect absorption in the visible to near-IR and mid-IR spectral range. In addition, we report a direct application of the presented system as an absorption based plasmonic sensor with a record figure of merit for this class of sensors.

  18. A multiband perfect absorber based on hyperbolic metamaterials

    PubMed Central

    Sreekanth, Kandammathe Valiyaveedu; ElKabbash, Mohamed; Alapan, Yunus; Rashed, Alireza R.; Gurkan, Umut A.; Strangi, Giuseppe

    2016-01-01

    In recent years, considerable research efforts have been focused on near-perfect and perfect light absorption using metamaterials spanning frequency ranges from microwaves to visible frequencies. This relatively young field is currently facing many challenges that hampers its possible practical applications. In this paper, we present grating coupled-hyperbolic metamaterials (GC-HMM) as multiband perfect absorber that can offer extremely high flexibility in engineering the properties of electromagnetic absorption. The fabricated GC-HMMs exhibit several highly desirable features for technological applications such as polarization independence, wide angle range, broad- and narrow- band modes, multiband perfect and near perfect absorption in the visible to near-IR and mid-IR spectral range. In addition, we report a direct application of the presented system as an absorption based plasmonic sensor with a record figure of merit for this class of sensors. PMID:27188789

  19. Lattice fluid dynamics from perfect discretizations of continuum flows

    SciTech Connect

    Katz, E.; Wiese, U.

    1998-11-01

    We use renormalization group methods to derive equations of motion for large scale variables in fluid dynamics. The large scale variables are averages of the underlying continuum variables over cubic volumes and naturally exist on a lattice. The resulting lattice dynamics represents a perfect discretization of continuum physics, i.e., grid artifacts are completely eliminated. Perfect equations of motion are derived for static, slow flows of incompressible, viscous fluids. For Hagen-Poiseuille flow in a channel with a square cross section the equations reduce to a perfect discretization of the Poisson equation for the velocity field with Dirichlet boundary conditions. The perfect large scale Poisson equation is used in a numerical simulation and is shown to represent the continuum flow exactly. For nonsquare cross sections one can use a numerical iterative procedure to derive flow equations that are approximately perfect. {copyright} {ital 1998} {ital The American Physical Society}

  20. WIND Validation Cases: Computational Study of Thermally-perfect Gases

    NASA Technical Reports Server (NTRS)

    DalBello, Teryn; Georgiadis, Nick (Technical Monitor)

    2002-01-01

    The ability of the WIND Navier-Stokes code to predict the physics of multi-species gases is investigated in support of future high-speed, high-temperature propulsion applications relevant to NASA's Space Transportation efforts. Three benchmark cases are investigated to evaluate the capability of the WIND chemistry model to accurately predict the aerodynamics of multi-species chemically non-reacting (frozen) gases. Case 1 represents turbulent mixing of sonic hydrogen and supersonic vitiated air. Case 2 consists of heated and unheated round supersonic jet exiting to ambient. Case 3 represents 2-D flow through a converging-diverging Mach 2 nozzle. For Case 1, the WIND results agree fairly well with experimental results and that significant mixing occurs downstream of the hydrogen injection point. For Case 2, the results show that the Wilke and Sutherland viscosity laws gave similar results, and the available SST turbulence model does not predict round supersonic nozzle flows accurately. For Case 3, results show that experimental, frozen, and 1-D gas results agree fairly well, and that frozen, homogeneous, multi-species gas calculations can be approximated by running in perfect gas mode while specifying the mixture gas constant and Ratio of Specific Heats.

  1. [Comment on] Toward a near-perfect AGU

    NASA Astrophysics Data System (ADS)

    Ilyas, M.

    For many months I have been troubled by the thought of a near-perfect AGU, deriving my inspiration from the AIP (consisting of eight big scientific societies), which has successfully organized journals in a very information-efficient manner and is able to avoid duplication in its four-dozenodd publications. This is a great value to members who wish to subscribe to individual journals for personal use.The recent Publications Committee letter (Eos, 62, 19, 489) inquiring whether AGU journals should be further split up along our disciplinary lines provided the stimulus for this note. I feel that there is a lot of publication overlap between AGU and AMS. JGR-Space Physics, and JGR-Oceans and Atmospheres duplicate to some extent the coverage of the Journal of Atmospheric Sciences, the Monthly Weather Review, and the Journal of Physical Oceanography. Similarly there is overlap between the third section of JGR and Geophysics, the bulletin of the Society of Exploration Geophysicists. Could there not be a federation of these societies, with one of its primary tasks to reorganize journal publication, cutting down, but not necessarily eliminating, duplication along the AIP lines? I suspect there are a number of other societies that should be included in such a federation.

  2. Kantowski-Sachs Einstein-æther perfect fluid models

    NASA Astrophysics Data System (ADS)

    Latta, Joey; Leon, Genly; Paliathanasis, Andronikos

    2016-11-01

    We investigate Kantowski-Sachs models in Einstein-æ ther theory with a perfect fluid source using the singularity analysis to prove the integrability of the field equations and dynamical system tools to study the evolution. We find an inflationary source at early times, and an inflationary sink at late times, for a wide region in the parameter space. The results by A.A. Coley, G. Leon, P. Sandin and J. Latta (JCAP 12 (2015) 010), are then re-obtained as particular cases. Additionally, we select other values for the non-GR parameters which are consistent with current constraints, getting a very rich phenomenology. In particular, we find solutions with infinite shear, zero curvature, and infinite matter energy density in comparison with the Hubble scalar. We also have stiff-like future attractors, anisotropic late-time attractors, or both, in some special cases. Such results are developed analytically, and then verified by numerics. Finally, the physical interpretation of the new critical points is discussed.

  3. Stability of Passive Locomotion in a Perfect Fluid

    NASA Astrophysics Data System (ADS)

    Jing, Fangxu; Kanso, Eva

    2010-11-01

    We investigate the effect of body elasticity on the stability of locomotion in a perfect fluid. Our motivation is to study fish swimming. Actual fish seem to alternate between actively flapping and passively responding to the surrounding fluid, referred to as Burst and Coast cycle. We study the stability of the coast (passive) phase. It's well known that the passive motion of a single elongated rigid body along its major axis of symmetry is unstable. The question is: can passive shape changes mediated by body elasticity stabilize the motion? The answer is yes. We consider an articulated body with finite number of rigid links, connected by hinge joints with torsional springs at the joints to emulate the elasticity of fish. The motion of the articulated body with constant velocity along its major axis of symmetry is a relative equilibrium. Upon analyzing the stability of this equilibrium, we discover that passive shape changes do stabilize the motion for appropriate combination of body geometry and spring elasticity. We plot the region of stability in aspect ratio - spring stiffness parameter space.

  4. The Perfect Mate for Safe Fueling

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Referred to as the "lifeline for any space launch vehicle" by NASA Space Launch Initiative Program Manager Warren Wiley, an umbilical is a large device that transports power, communications, instrument readings, and fluids such as propellants, pressurization gases, and coolants from one source to another. Numerous launch vehicles, planetary systems, and rovers require umbilical "mating". This process is a driving factor for dependable and affordable space access. With future-generation space vehicles in mind, NASA recently designed a smart, automated method for quickly and reliably mating and demating electrical and fluid umbilical connectors. The new umbilical concept is expected to replace NASA s traditional umbilical systems that release at vehicle lift-off (T-0). The idea is to increase safety by automatically performing hazardous tasks, thus reducing potential failure modes and the time and labor hours necessary to prepare for launch. The new system will also be used as a test bed for quick disconnect development and for advance control and leak detection. It incorporates concepts such as a secondary mate plate, robotic machine vision, and compliant motor motion control, and is destined to advance usage of automated umbilicals in a variety of aerospace and commercial applications.

  5. Computer Program for Thin Wire Antenna over a Perfectly Conducting Ground Plane. [using Galerkins method and sinusoidal bases

    NASA Technical Reports Server (NTRS)

    Richmond, J. H.

    1974-01-01

    A computer program is presented for a thin-wire antenna over a perfect ground plane. The analysis is performed in the frequency domain, and the exterior medium is free space. The antenna may have finite conductivity and lumped loads. The output data includes the current distribution, impedance, radiation efficiency, and gain. The program uses sinusoidal bases and Galerkin's method.

  6. Resonances of a submerged fluid-filled spherically isotropic microsphere with partial-slip interface condition

    NASA Astrophysics Data System (ADS)

    Tamadapu, Ganesh; Nordmark, Arne; Eriksson, Anders

    2015-07-01

    Motivated by the numerous applications of spherical shell models in micro and nano scales (such as microbubbles, bacterial cells, and viral capsids), we have considered the axisymmetric free vibrations of a spherically isotropic fluid-filled thick microspherical shell suspended in another unbounded fluid. A partial-slip condition is considered at the solid-fluid interface(s). Three-dimensional linear elasticity equations for the spherically isotropic shell dynamics and linearized Navier-Stokes equations for the two compressible viscous fluids are used in the analysis. The eigenvalue problem is discretized and solved to find the resonances and quality factors. A perfectly matched layer technique is used to separate the solid driven spectrum from the boundary reflecting spectrum. An example of air filled polymer shell suspended in water is presented. The added mass effect and partial-slip condition from water (air) on the frequencies and quality factors are found to be significant (negligible). Spherical isotropy is found to have major influence on the low frequency and large meridional wave number region of the resonance spectrum. High quality eigenmodes are observed due to very small viscous penetration depth compared to the shell size. In the thin-shell limit, the eigenvalue problem can have only two modes of vibration for any meridional wave number greater than or equal to two. This explains the reason for the second resonance frequency found for the quadrupole shape oscillations of various bacterium cells in the earlier work. The partial-slip condition is found to have very small influence on the first few modes of vibration. Surface tension is found to have significant influence only on the lowest frequency trend of the eigenspectrum. Perfectly matched layer technique used in the present analysis is found to be very effective in handling the boundary truncated problems.

  7. Modeling of the acoustic field of thermally induced ultrasonic emission from a spherical cavity surface.

    PubMed

    Wang, Dongdong; Hu, Hanping; Wang, Zedong

    2015-02-01

    Thermo-acoustic (TA) ultrasound has attracted considerable interest during the last decade for its many advantages over the conventional electro-acoustic ultrasound. In this paper, a general expression of the acoustic pressure field of thermally induced ultrasonic emission from a spherical cavity surface is derived by using a fully thermally-mechanically coupled TA model. The characteristics and regularities of ultrasound from spherical focusing TA emitter can therefore be studied in detail. It is found that, for the TA emission in sphere shell, wideband flat amplitude-frequency response pattern, the most important feature of TA ultrasound in an open space from a technical standpoint, is seriously disrupted by wave interference occurring in spherical cavity. The dependences of sound pressure of TA ultrasound in spherical cavity on the heating frequency, the inner radius of spherical cavity, the location in spherical cavity, and the thickness of TA sample layer, as well as the type and filling pressure of gas in cavity are given and discussed. The currently used planar TA solution is only the special case for spherical cavity with infinite radius of the analytical solution developed in this work, which would be of significance for more comprehensive guide to understanding and using TA ultrasound.

  8. MRS3D: 3D Spherical Wavelet Transform on the Sphere

    NASA Astrophysics Data System (ADS)

    Lanusse, F.; Rassat, A.; Starck, J.-L.

    2011-12-01

    Future cosmological surveys will provide 3D large scale structure maps with large sky coverage, for which a 3D Spherical Fourier-Bessel (SFB) analysis is natural. Wavelets are particularly well-suited to the analysis and denoising of cosmological data, but a spherical 3D isotropic wavelet transform does not currently exist to analyse spherical 3D data. We present a new fast Discrete Spherical Fourier-Bessel Transform (DSFBT) based on both a discrete Bessel Transform and the HEALPIX angular pixelisation scheme. We tested the 3D wavelet transform and as a toy-application, applied a denoising algorithm in wavelet space to the Virgo large box cosmological simulations and found we can successfully remove noise without much loss to the large scale structure. The new spherical 3D isotropic wavelet transform, called MRS3D, is ideally suited to analysing and denoising future 3D spherical cosmological surveys; it uses a novel discrete spherical Fourier-Bessel Transform. MRS3D is based on two packages, IDL and Healpix and can be used only if these two packages have been installed.

  9. Wrinkling crystallography on spherical surfaces

    PubMed Central

    Brojan, Miha; Terwagne, Denis; Lagrange, Romain; Reis, Pedro M.

    2015-01-01

    We present the results of an experimental investigation on the crystallography of the dimpled patterns obtained through wrinkling of a curved elastic system. Our macroscopic samples comprise a thin hemispherical shell bound to an equally curved compliant substrate. Under compression, a crystalline pattern of dimples self-organizes on the surface of the shell. Stresses are relaxed by both out-of-surface buckling and the emergence of defects in the quasi-hexagonal pattern. Three-dimensional scanning is used to digitize the topography. Regarding the dimples as point-like packing units produces spherical Voronoi tessellations with cells that are polydisperse and distorted, away from their regular shapes. We analyze the structure of crystalline defects, as a function of system size. Disclinations are observed and, above a threshold value, dislocations proliferate rapidly with system size. Our samples exhibit striking similarities with other curved crystals of charged particles and colloids. Differences are also found and attributed to the far-from-equilibrium nature of our patterns due to the random and initially frozen material imperfections which act as nucleation points, the presence of a physical boundary which represents an additional source of stress, and the inability of dimples to rearrange during crystallization. Even if we do not have access to the exact form of the interdimple interaction, our experiments suggest a broader generality of previous results of curved crystallography and their robustness on the details of the interaction potential. Furthermore, our findings open the door to future studies on curved crystals far from equilibrium. PMID:25535355

  10. Spherical Shell Vortex Model For Compound Drops

    NASA Astrophysics Data System (ADS)

    Shusser, Michael; Weihs, Daniel

    2003-11-01

    A new generalization of the classical solution for inviscid incompressible flow with vorticity known as Hill's spherical vortex is presented here. The new solution includes a concentric sphere inside the spherical body produced by Hill's vortex. The internal sphere can be filled with a different fluid,with limiting cases of a spherical cavity, or solid sphere. This solution is applicable to coated pill and pellet manfacture.The present solution also includes internal swirling about the axis parallel to the direction of oncoming flow.

  11. Computer code for determination of thermally perfect gas properties

    NASA Technical Reports Server (NTRS)

    Witte, David W.; Tatum, Kenneth E.

    1994-01-01

    A set of one-dimensional compressible flow relations for a thermally perfect, calorically imperfect gas is derived for the specific heat c(sub p), expressed as a polynomial function of temperature, and developed into the thermally perfect gas (TPG) computer code. The code produces tables of compressible flow properties similar to those of NACA Rep. 1135. Unlike the tables of NACA Rep. 1135 which are valid only in the calorically perfect temperature regime, the TPG code results are also valid in the thermally perfect calorically imperfect temperature regime which considerably extends the range of temperature application. Accuracy of the TPG code in the calorically perfect temperature regime is verified by comparisons with the tables of NACA Rep. 1135. In the thermally perfect, calorically imperfect temperature regime, the TPG code is validated by comparisons with results obtained from the method of NACA Rep. 1135 for calculating the thermally perfect calorically imperfect compressible flow properties. The temperature limits for application of the TPG code are also examined. The advantage of the TPG code is its applicability to any type of gas (monatomic, diatomic, triatomic, or polyatomic) or any specified mixture thereof, whereas the method of NACA Rep. 1135 is restricted to only diatomic gases.

  12. Visual Detection and Tracking System for a Spherical Amphibious Robot

    PubMed Central

    Guo, Shuxiang; Pan, Shaowu; Shi, Liwei; Guo, Ping; He, Yanlin; Tang, Kun

    2017-01-01

    With the goal of supporting close-range observation tasks of a spherical amphibious robot, such as ecological observations and intelligent surveillance, a moving target detection and tracking system was designed and implemented in this study. Given the restrictions presented by the amphibious environment and the small-sized spherical amphibious robot, an industrial camera and vision algorithms using adaptive appearance models were adopted to construct the proposed system. To handle the problem of light scattering and absorption in the underwater environment, the multi-scale retinex with color restoration algorithm was used for image enhancement. Given the environmental disturbances in practical amphibious scenarios, the Gaussian mixture model was used to detect moving targets entering the field of view of the robot. A fast compressive tracker with a Kalman prediction mechanism was used to track the specified target. Considering the limited load space and the unique mechanical structure of the robot, the proposed vision system was fabricated with a low power system-on-chip using an asymmetric and heterogeneous computing architecture. Experimental results confirmed the validity and high efficiency of the proposed system. The design presented in this paper is able to meet future demands of spherical amphibious robots in biological monitoring and multi-robot cooperation. PMID:28420134

  13. New results of the spherical convection experiment Geoflow IIc

    NASA Astrophysics Data System (ADS)

    Zaussinger, Florian; Egbers, Christoph; Krebs, Andreas; Travnikov, Vadim

    2017-04-01

    Thermal driven convection in spherical geometry is of main interest in geo- and astrophysical research. To capture certain aspects of convective processes we investigate the micro-gravity experiment GeoFlow-IIc, located on the ISS. This unique experimental setup consists of a bottom heated and top cooled spherical gap, filled with the silicon oil 1-Nonanol. However, rotation and varying temperature gradients can be applied, to spread the experimental parameter space. The main focus of the currently performed mission is the investigation of flow structures at the convective onset and the transition from laminar to turbulent flows. Since the ISS requirements makes it impossible to use tracer particles, the flow structures are captured by interferometry, whose outcome is analysed by an ground based adapted image processing technique. We present advanced post-processing techniques to capture and trace convective plumes to investigate their relative speed and the temporal behavior. Additionally, we are presenting latest results concerning non-unique convective patterns at the same Rayleigh number. The results are cautiously compared with theoretical assumptions of structural changes, which depend on initial perturbations and non-linear influences like the dielectrophoretic force field. Besides, numerical simulations in the same parameter regime are performed, which give the opportunity to deduce the internal structure of the experimental flow flied. The main focus of the presented results are the temporal evolution of convective plumes in the spherical gap, image capturing- and processing techniques and the non-unique pattern formation.

  14. Visual Detection and Tracking System for a Spherical Amphibious Robot.

    PubMed

    Guo, Shuxiang; Pan, Shaowu; Shi, Liwei; Guo, Ping; He, Yanlin; Tang, Kun

    2017-04-15

    With the goal of supporting close-range observation tasks of a spherical amphibious robot, such as ecological observations and intelligent surveillance, a moving target detection and tracking system was designed and implemented in this study. Given the restrictions presented by the amphibious environment and the small-sized spherical amphibious robot, an industrial camera and vision algorithms using adaptive appearance models were adopted to construct the proposed system. To handle the problem of light scattering and absorption in the underwater environment, the multi-scale retinex with color restoration algorithm was used for image enhancement. Given the environmental disturbances in practical amphibious scenarios, the Gaussian mixture model was used to detect moving targets entering the field of view of the robot. A fast compressive tracker with a Kalman prediction mechanism was used to track the specified target. Considering the limited load space and the unique mechanical structure of the robot, the proposed vision system was fabricated with a low power system-on-chip using an asymmetric and heterogeneous computing architecture. Experimental results confirmed the validity and high efficiency of the proposed system. The design presented in this paper is able to meet future demands of spherical amphibious robots in biological monitoring and multi-robot cooperation.

  15. Spherical means of solutions of partial differential equations in a conical region

    NASA Technical Reports Server (NTRS)

    Ting, L.

    1974-01-01

    The spherical means of the solutions of a linear partial differential equation Lu = f in a conical region are studied. The conical region is bounded by a surface generated by curvilinear ti surfaces. The spherical mean is the average of u over a constant ti surface. The conditions on the linear differential operator, L, and on the orthogonal coordinates (ti, eta, zeta) are established so that the spherical mean of the solution subjected to the appropriate boundary and initial conditions can be determined directly as a problem with only space variable. Conditions are then established so that the spherical mean of the solution in one concial region will be proportional to that of a known solution in another conical region. Applications to various problems of mathematical physics and their physical interpretations are presented.

  16. Laser Interferometer Space Antenna (LISA) Far Field Phase Patterns

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene; Obenschain, Arthur F. (Technical Monitor)

    2000-01-01

    The Laser Interferometer Space Antenna (LISA) consists of three spacecraft in orbit about the sun. The orbits are chosen such that the three spacecraft are always at (roughly) the vertices of a equilateral triangle with 5 million kilometer leg lengths. Even though the distances between the three spacecraft are 5 million kilometers, the expected phase shifts between any two beams, due to a gravitational wave, only correspond to a distance change of about 10 pico meters, which is about 10(exp -5) waves for a laser wavelength of 1064 nm. To obtain the best signal-to-noise ratio, noise sources such as changes in the apparent distances due to pointing jitter must be controlled carefully. This is the main reason for determining the far-field phase patterns of a LISA type telescope. Because of torque on the LISA spacecraft and other disturbances, continuous adjustments to the pointing of the telescopes are required. These pointing adjustments will be a "jitter" source. If the transmitted wave is perfectly spherical then rotations (Jitter) about its geometric center will not produce any effect at the receiving spacecraft. However, if the outgoing wave is not perfectly spherical, then pointing jitter will produce a phase variation at the receiving spacecraft. The following sections describe the "brute force" computational approach used to determine the scalar wave front as a function of exit pupil (Zernike) aberrations and to show the results (mostly graphically) of the computations. This approach is straightforward and produces believable phase variations to sub-pico meter accuracy over distances on the order of 5 million kilometers. As such this analyzes the far field phase sensitivity to exit pupil aberrations.

  17. Mode-coupling approach for the slow dynamics of a liquid on a spherical substrate.

    PubMed

    Vest, Julien-Piera; Tarjus, Gilles; Viot, Pascal

    2015-08-28

    We study the dynamics of a one-component liquid constrained on a spherical substrate, a 2-sphere, and investigate how the mode-coupling theory (MCT) can describe the new features brought by the presence of curvature. To this end we have derived the MCT equations in a spherical geometry. We find that, as seen from the MCT, the slow dynamics of liquids in curved space at low temperature does not qualitatively differ from that of glass-forming liquids in Euclidean space. The MCT predicts the right trend for the evolution of the relaxation slowdown with curvature but is dramatically off at a quantitative level.

  18. Highly dense and perfectly aligned single-walled carbon nanotubes fabricated by diamond wire drawing dies.

    PubMed

    Liu, Guangtong; Zhao, Yuanchun; Deng, Ke; Liu, Zheng; Chu, Weiguo; Chen, Jingran; Yang, Yanlian; Zheng, Kaihong; Huang, Haibo; Ma, Wenjun; Song, Li; Yang, Haifang; Gu, Changzhi; Rao, Guanghui; Wang, Chen; Xie, Sishen; Sun, Lianfeng

    2008-04-01

    We have developed a low-cost and effective method to align single-walled carbon nanotubes (SWNTs) using a series of diamond wire drawing dies. The obtained SWNTs are highly dense and perfectly aligned. X-ray diffraction (XRD) indicates that the highly dense and perfectly aligned SWNTs (HDPA-SWNTs) form a two-dimensional triangular lattice with a lattice constant of 19.62 A. We observe a sharp (002) reflection in the XRD pattern, which should be ascribed to an intertube spacing 3.39 A of adjacent SWNTs. Raman spectra reveal that the radical breath mode (RBM) of SWNTs with larger diameter in the HDPA-SWNTs is suppressed compared with that of as-grown SWNTs. The HDPA-SWNTs have a large density, approximately 1.09 g/cm 3, and a low resistivity, approximately 2 m Omega cm, at room temperature, as well as a large response to light illumination.

  19. Near-Perfect Adaptation in the E. coli Chemotaxis Signal Transduction Network

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Setayeshgar, Sima

    2007-03-01

    Biochemical reaction networks constitute the computing language of the cell, from converting external stimuli into appropriate intracellular signals to regulating gene expression. Precise adaptation is an important property of many signaling networks, allowing compensation for continued stimulation without saturation. Furthermore, a common feature of intracellular reaction networks is the ability to operate in a noisy environment where concentrations of key components, such as signaling molecules and enzymes controlling reaction rates are typically small and therefore fluctuations in their numbers are significant. In the context of the well- characterized E. coli chemotaxis signal transduction network, we present a new computational scheme that explores surfaces in the space of total protein concentrations and reaction rates on which (near-)perfect adaptation holds. The resulting dependencies between parameters provide conditions for (near-)perfect adaptation as well as ranges of numerical values for parameters not reliably known from experiments. We generalize the applicability of this scheme to other signaling networks.

  20. Protein-Precipitant-Specific Criteria for the Impact of Reduced Gravity on Crystal Perfection

    NASA Technical Reports Server (NTRS)

    Vekilov, Peter G.; Witherow, W. (Technical Monitor)

    2003-01-01

    The objective of this research is to provide quantitative criteria for the impact of reduced or enhanced convective transport on protein crystal perfection. Our earlier work strongly suggests that the magnitude of (lattice defect-inducing) fluctuations in the crystallization rate of proteins arise from the coupling of bulk transport and nonlinear interface kinetics. Hence, we surmised that, depending on the relative weight of bulk transport and interface kinetics in the control of the crystallization process on Earth, these fluctuations can either increase or decrease under reduced gravity conditions. The sign and magnitude of these changes depend on the specific protein-precipitant system. As a consequence, space environments can be either beneficial or detrimental for achieving structural perfection in protein crystals. The task objectives consist in systematic investigations of this hypothesis.

  1. Scheme for achieving coherent perfect absorption by anisotropic metamaterials.

    PubMed

    Zhang, Xiujuan; Wu, Ying

    2017-03-06

    We propose a unified scheme to achieve coherent perfect absorption of electromagnetic waves by anisotropic metamaterials. The scheme describes the condition on perfect absorption and offers an inverse design route based on effective medium theory in conjunction with retrieval method to determine practical metamaterial absorbers. The scheme is scalable to frequencies and applicable to various incident angles. Numerical simulations show that perfect absorption is achieved in the designed absorbers over a wide range of incident angles, verifying the scheme. By integrating these absorbers, we further propose an absorber to absorb energy from two coherent point sources.

  2. Metamaterial perfect absorber based on artificial dielectric "atoms".

    PubMed

    Liu, Xiaoming; Bi, Ke; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-09-05

    In this work, we numerically designed and then experimentally verified a metamaterial perfect absorber based on artificial dielectric "atoms". This metamaterial absorber is composed of dielectric ceramic material (SrTiO3) "atoms" embedded in a background matrix on a metal plate. The dielectric "atoms" couple strongly to the incident electric and magnetic fields at the Mie resonance mode, leading to the narrow perfect absorption band with simulated and experimental absorptivities of 99% and 98.5% at 8.96 GHz, respectively. The designed metamaterial perfect absorber is polarization insensitive and can operate in wide angle incidence.

  3. Nearly Perfect Fluidity in a High Temperature Superconductor

    DOE PAGES

    Rameau, J. D.; Reber, T. J.; Yang, H. -B.; ...

    2014-10-13

    Perfect fluids are characterized as having the smallest ratio of shear viscosity to entropy density, η/s, consistent with quantum uncertainty and causality. So far, nearly perfect fluids have only been observed in the quark-gluon plasma and in unitary atomic Fermi gases, exotic systems that are amongst the hottest and coldest objects in the known universe, respectively. We use angle resolved photoemission spectroscopy to measure the temperature dependence of an electronic analog of η/s in an optimally doped cuprate high-temperature superconductor, finding it too is a nearly perfect fluid around, and above, its superconducting transition temperature Tc.

  4. Nearly Perfect Fluidity in a High Temperature Superconductor

    SciTech Connect

    Rameau, J. D.; Reber, T. J.; Yang, H. -B.; Akhanjee, S.; Gu, G. D.; Johnson, P. D.; Campbell, S.

    2014-10-13

    Perfect fluids are characterized as having the smallest ratio of shear viscosity to entropy density, η/s, consistent with quantum uncertainty and causality. So far, nearly perfect fluids have only been observed in the quark-gluon plasma and in unitary atomic Fermi gases, exotic systems that are amongst the hottest and coldest objects in the known universe, respectively. We use angle resolved photoemission spectroscopy to measure the temperature dependence of an electronic analog of η/s in an optimally doped cuprate high-temperature superconductor, finding it too is a nearly perfect fluid around, and above, its superconducting transition temperature Tc.

  5. Lorentz force and radiation pressure on a spherical cloak

    SciTech Connect

    Chen Hongsheng; Wu, B.-I.; Zhang Baile; Luo Yu; Zhang Jingjing; Ran Lixin; Kemp, Brandon A.

    2009-07-15

    The mechanical behavior of a transformation based spherical cloak under wave illumination is derived. We show that the equatorial region of the cloak is subject to much higher stress than the polar regions, where the polar axis is defined along the wave propagation direction. These forces do not exist before transformation but stem from the squeezed electromagnetic space. The trajectory of the ray can be interpreted as a result of the recoil force that the cloak exerts upon the ray. The total radiation pressure on an ideal cloak is shown to be exactly zero, effecting a stationary cloak.

  6. A numerical optimization approach to generate smoothing spherical splines

    NASA Astrophysics Data System (ADS)

    Machado, L.; Monteiro, M. Teresa T.

    2017-01-01

    Approximating data in curved spaces is a common procedure that is extremely required by modern applications arising, for instance, in aerospace and robotics industries. Here, we are particularly interested in finding smoothing cubic splines that best fit given data in the Euclidean sphere. To achieve this aim, a least squares optimization problem based on the minimization of a certain cost functional is formulated. To solve the problem a numerical algorithm is implemented using several routines from MATLAB toolboxes. The proposed algorithm is shown to be easy to implement, very accurate and precise for spherical data chosen randomly.

  7. The buckling of spherical liposomes.

    PubMed

    Pamplona, D C; Greenwood, J A; Calladine, C R

    2005-12-01

    In the classical "first approximation" theory of thin-shell structures, the constitutive relations for a generic shell element--i.e. the elastic relations between the bending moments and membrane stresses and the corresponding changes in curvature and strain, respectively-are written as if an element of the shell is flat, although in reality it is curved. In this theory it is believed that discrepancies on account of the use of "flat" constitutive relations will be negligible provided the ratio shell-radius/thickness is of sufficiently large order. In the study of drawing of narrow, cylindrical "tethers" from liposomes it has been known for many years that it is necessary to use instead a constitutive law which explicitly describes a curved element in order to make sense of the mechanics; and indeed such tethers are generally of "thick-walled" proportions. In this paper we show that the proper constitutive relations for a curved element must also be used in the study, by means of shell equations, of the buckling of initially spherical thin-walled giant liposomes under exterior pressure: these involve the inclusion of what we call the "Mkappa" terms, which are not present in the standard "first-approximation" theory. We obtain analytical expressions for both the bifurcation buckling pressure and the slope of the post-buckling path, in terms of the dimensions and elastic constants of the lipid bi-layer, and also the initial state of bending moment in the vesicle. We explain physically how the initial bending moment can affect the bifurcation pressure, whereas it cannot in "first-approximation" theory. We use these results to map the conditions under which the vesicle buckles into an oblate, as distinct from a prolate ("rugby-ball") shape. Some of our results were obtained long ago by the use of energy methods; but our aim here has been to identify precisely what is lacking in "first-approximation" theory in relation to liposomes, and so to put the "shell equations

  8. How Spherical Is a Cube (Gravitationally)?

    NASA Astrophysics Data System (ADS)

    Sanny, Jeff; Smith, David

    2015-02-01

    An important concept that is presented in the discussion of Newton's law of universal gravitation is that the gravitational effect external to a spherically symmetric mass distribution is the same as if all of the mass of the distribution were concentrated at the center.1,2 By integrating over ring elements of a spherical shell, we show that the gravitational force on a point mass outside the shell is the same as that of a particle with the same mass as the shell at its center. This derivation works for objects with spherical symmetry while depending on the fact that the gravitational force between two point masses varies inversely as the square of their separation.3 If these conditions are not met, then the problem becomes more difficult. In this paper, we remove the condition of spherical symmetry and examine the gravitational force between two uniform cubes.

  9. Sphericity determination using resonant ultrasound spectroscopy

    DOEpatents

    Dixon, Raymond D.; Migliori, Albert; Visscher, William M.

    1994-01-01

    A method is provided for grading production quantities of spherical objects, such as roller balls for bearings. A resonant ultrasound spectrum (RUS) is generated for each spherical object and a set of degenerate sphere-resonance frequencies is identified. From the degenerate sphere-resonance frequencies and known relationships between degenerate sphere-resonance frequencies and Poisson's ratio, a Poisson's ratio can be determined, along with a "best" spherical diameter, to form spherical parameters for the sphere. From the RUS, fine-structure resonant frequency spectra are identified for each degenerate sphere-resonance frequency previously selected. From each fine-structure spectrum and associated sphere parameter values an asphericity value is determined. The asphericity value can then be compared with predetermined values to provide a measure for accepting or rejecting the sphere.

  10. FY 2005 Miniature Spherical Retroreflectors Final Report

    SciTech Connect

    Anheier, Norman C.; Bernacki, Bruce E.; Johnson, Bradley R.; Riley, Brian J.; Sliger, William A.

    2005-12-01

    Research done by the Infrared Photonics team at Pacific Northwest National Laboratory (PNNL) is focused on developing miniature spherical retroreflectors using the unique optical and material properties of chalcogenide glass to reduce both performance limiting spherical and chromatic aberrations. The optimized optical performance will provide efficient signal retroreflection that enables a broad range of remote detection scenarios for mid-wave infrared (MWIR) and long-wave infrared (LWIR) sensing applications. Miniature spherical retroreflectors can be developed to aid in the detection of signatures of nuclear proliferation or other chemical vapor or radiation signatures. Miniature spherical retroreflectors are not only well suited to traditional bistatic LIDAR methods for chemical plume detection and identification, but could enable remote detection of difficult semi-volatile chemical materials or low level radiation sources.

  11. Sphericity determination using resonant ultrasound spectroscopy

    DOEpatents

    Dixon, R.D.; Migliori, A.; Visscher, W.M.

    1994-10-18

    A method is provided for grading production quantities of spherical objects, such as roller balls for bearings. A resonant ultrasound spectrum (RUS) is generated for each spherical object and a set of degenerate sphere-resonance frequencies is identified. From the degenerate sphere-resonance frequencies and known relationships between degenerate sphere-resonance frequencies and Poisson's ratio, a Poisson's ratio can be determined, along with a 'best' spherical diameter, to form spherical parameters for the sphere. From the RUS, fine-structure resonant frequency spectra are identified for each degenerate sphere-resonance frequency previously selected. From each fine-structure spectrum and associated sphere parameter values an asphericity value is determined. The asphericity value can then be compared with predetermined values to provide a measure for accepting or rejecting the sphere. 14 figs.

  12. Spherical operator classification for coronary artery extraction.

    PubMed

    Geng, Chen; Yang, Jian; Dai, Yakang; Liu, Zhaobang; Dong, Yuefang

    2014-01-01

    Computed tomography angiography (CTA) is a major noninvasive technology for imaging coronary artery disease, and effective and accurate vessel tracking method can help radiologists diagnose the disease more accurately. In this paper, a novel 3D vessel tracking method based on CTA data is presented. The method is comprised of preprocessing, a novel spherical operator, and hierarchical clustering, where the spherical operator consists of rays that are casted different directions in a spherical coordinate system. The vascular boundary is extracted by the spherical operator, and the tracking direction is also obtained by the hierarchical clustering. The method is evaluated with the Rotterdam Coronary Artery Algorithm Evaluation Framework. Results indicate that our method outperforms current state-of-the-art methods in terms of the overlap ratio on the vessel tracking of coronary arteries in CTA data.

  13. Feasibility study for the Spherical Torus Experiment

    SciTech Connect

    Lazarus, E.A.; Attenberger, S.E.; Baylor, L.R.; Borowski, S.K.; Brown, R.L.; Carreras, B.A.; Charlton, L.A.; Chipley, K.K.; Dalton, G.R.; Fowler, R.H.

    1985-10-01

    The design of the Spherical Torus Experiment (STX) is discussed. The physics of the plasma are given in a magnetohydrodynamic model. The structural aspects and instrumentation of the device are described. 19 refs., 103 figs. (WRF)

  14. FY 2006 Miniature Spherical Retroreflectors Final Report

    SciTech Connect

    Anheier, Norman C.; Bernacki, Bruce E.; Krishnaswami, Kannan

    2006-12-28

    Research done by the Infrared Photonics team at Pacific Northwest National Laboratory (PNNL) is focused on developing miniature spherical retroreflectors using the unique optical and material properties of chalcogenide glass to reduce both performance limiting spherical aberrations. The optimized optical performance will provide efficient signal retroreflection that enables a broad range of remote detection scenarios for mid-wave infrared (MWIR) and long-wave infrared (LWIR) sensing applications. Miniature spherical retroreflectors can be developed to aid in the detection of signatures of nuclear proliferation or other chemical vapor or radiation signatures. Miniature spherical retroreflectors are not only well suited to traditional LIDAR methods for chemical plume detection and identification, but could enable remote detection of difficult semi-volatile chemical materials or low level radiation sources.

  15. Observation of spherical ion-acoustic solitons

    SciTech Connect

    Nakamura, Y.; Ooyama, M.; Ogino, T.

    1980-11-10

    Spherically converging positive and negative ion-acoustic pulses are investigated experimentally. Their behavior agrees with computer simulations based on the fluid model of plasma. Large positive pulses are identified as solitons.

  16. HFE and Spherical Cryostats MC Study

    SciTech Connect

    Brodsky, Jason P.

    2016-09-26

    The copper vessel containing the nEXO TPC is surrounded by a buffer of HFE, a liquid refrigerant with very low levels of radioactive element contamination. The HFE is contained within the cryostat’s inner vessel, which is in turn inside the outer vessel. While some HFE may be necessary for stable cooling of nEXO, it is possible that using substantially more than necessary for thermal reasons will help reduce backgrounds originating in the cryostats. Using a larger amount of HFE is accomplished by making the cryostat vessels larger. By itself, increasing the cryostat size somewhat increases the background rate, as the thickness of the cryostat wall must increase at larger sizes. However, the additional space inside the cryostat will be filled with HFE which can absorb gamma rays headed for the TPC. As a result, increasing the HFE reduces the number of backgrounds reaching the TPC. The aim of this study was to determine the relationship between HFE thickness and background rate. Ultimately, this work should support choosing a cryostat and HFE size that satisfies nEXO’s background budget. I have attempted to account for every consequence of changing the cryostat size, although naturally this remains a work in progress until a final design is achieved. At the moment, the scope of the study includes only the spherical cryostat design. This study concludes that increasing cryostat size reduces backgrounds, reaching neglible backgrounds originating from the cryostat at the largest sizes. It also shows that backgrounds originating from the inherent radioactivity of the HFE plateau quickly, so may be considered essentially fixed at any quantity of HFE.

  17. Spatial perception of sound fields recorded by spherical microphone arrays with varying spatial resolution.

    PubMed

    Avni, Amir; Ahrens, Jens; Geier, Matthias; Spors, Sascha; Wierstorf, Hagen; Rafaely, Boaz

    2013-05-01

    The area of sound field synthesis has significantly advanced in the past decade, facilitated by the development of high-quality sound-field capturing and re-synthesis systems. Spherical microphone arrays are among the most recently developed systems for sound field capturing, enabling processing and analysis of three-dimensional sound fields in the spherical harmonics domain. In spite of these developments, a clear relation between sound fields recorded by spherical microphone arrays and their perception with a re-synthesis system has not yet been established, although some relation to scalar measures of spatial perception was recently presented. This paper presents an experimental study of spatial sound perception with the use of a spherical microphone array for sound recording and headphone-based binaural sound synthesis. Sound field analysis and processing is performed in the spherical harmonics domain with the use of head-related transfer functions and simulated enclosed sound fields. The effect of several factors, such as spherical harmonics order, frequency bandwidth, and spatial sampling, are investigated by applying the repertory grid technique to the results of the experiment, forming a clearer relation between sound-field capture with a spherical microphone array and its perception using binaural synthesis regarding space, frequency, and additional artifacts. The experimental study clearly shows that a source will be perceived more spatially sharp and more externalized when represented by a binaural stimuli reconstructed with a higher spherical harmonics order. This effect is apparent from low spherical harmonics orders. Spatial aliasing, as a result of sound field capturing with a finite number of microphones, introduces unpleasant artifacts which increased with the degree of aliasing error.

  18. Compression dynamics of quasi-spherical wire arrays with different linear mass profiles

    SciTech Connect

    Mitrofanov, K. N. Aleksandrov, V. V.; Gritsuk, A. N.; Grabovski, E. V.; Frolov, I. N.; Laukhin, Ya. N.; Oleinik, G. M.; Ol’khovskaya, O. G.

    2016-09-15

    Results of experimental studies of the implosion of quasi-spherical wire (or metalized fiber) arrays are presented. The goal of the experiments was to achieve synchronous three-dimensional compression of the plasma produced in different regions of a quasi-spherical array into its geometrical center. To search for optimal synchronization conditions, quasi-spherical arrays with different initial profiles of the linear mass were used. The following dependences of the linear mass on the poloidal angle were used: m{sub l}(θ) ∝ sin{sup –1}θ and m{sub l}(θ) ∝ sin{sup –2}θ. The compression dynamics of such arrays was compared with that of quasi-spherical arrays without linear mass profiling, m{sub l}(θ) = const. To verify the experimental data, the spatiotemporal dynamics of plasma compression in quasi-spherical arrays was studied using various diagnostics. The experiments on three-dimensional implosion of quasi-spherical arrays made it possible to study how the frozen-in magnetic field of the discharge current penetrates into the array. By measuring the magnetic field in the plasma of a quasi-spherical array, information is obtained on the processes of plasma production and formation of plasma flows from the wire/fiber regions with and without an additionally deposited mass. It is found that penetration of the magnetic flux depends on the initial linear mass profile m{sub l}(θ) of the quasi-spherical array. From space-resolved spectral measurements and frame imaging of plasma X-ray emission, information is obtained on the dimensions and shape of the X-ray source formed during the implosion of a quasi-spherical array. The intensity of this source is estimated and compared with that of the Z-pinch formed during the implosion of a cylindrical array.

  19. Meanings and Distribution of the Perfect in Present-Day American English Prose.

    ERIC Educational Resources Information Center

    Dubois, Betty Lou

    This paper explores the meanings and distribution of the perfect in contemporary American English prose, with reference to problems encountered in teaching English as a second language. The English perfect comprises forms traditionally called present perfect tense, past perfect tense, and perfects of the infinitive, gerund and present participle.…

  20. PREPARATION OF SPHERICAL URANIUM DIOXIDE PARTICLES

    DOEpatents

    Levey, R.P. Jr.; Smith, A.E.

    1963-04-30

    This patent relates to the preparation of high-density, spherical UO/sub 2/ particles 80 to 150 microns in diameter. Sinterable UO/sub 2/ powder is wetted with 3 to 5 weight per cent water and tumbled for at least 48 hours. The resulting spherical particles are then sintered. The sintered particles are useful in dispersion-type fuel elements for nuclear reactors. (AEC)

  1. On Nonlinear Functionals of Random Spherical Eigenfunctions

    NASA Astrophysics Data System (ADS)

    Marinucci, Domenico; Wigman, Igor

    2014-05-01

    We prove central limit theorems and Stein-like bounds for the asymptotic behaviour of nonlinear functionals of spherical Gaussian eigenfunctions. Our investigation combines asymptotic analysis of higher order moments for Legendre polynomials and, in addition, recent results on Malliavin calculus and total variation bounds for Gaussian subordinated fields. We discuss applications to geometric functionals like the defect and invariant statistics, e.g., polyspectra of isotropic spherical random fields. Both of these have relevance for applications, especially in an astrophysical environment.

  2. Spherical cows in dark matter indirect detection

    NASA Astrophysics Data System (ADS)

    Bernal, Nicolás; Necib, Lina; Slatyer, Tracy R.

    2016-12-01

    Dark matter (DM) halos have long been known to be triaxial, but in studies of possible annihilation and decay signals they are often treated as approximately spherical. In this work, we examine the asymmetry of potential indirect detection signals of DM annihilation and decay, exploiting the large statistics of the hydrodynamic simulation Illustris. We carefully investigate the effects of the baryons on the sphericity of annihilation and decay signals for both the case where the observer is at 8.5 kpc from the center of the halo (exemplified in the case of Milky Way-like halos), and for an observer situated well outside the halo. In the case of Galactic signals, we find that both annihilation and decay signals are expected to be quite symmetric, with axis ratios very different from 1 occurring rarely. In the case of extragalactic signals, while decay signals are still preferentially spherical, the axis ratio for annihilation signals has a much flatter distribution, with elongated profiles appearing frequently. Many of these elongated profiles are due to large subhalos and/or recent mergers. Comparing to gamma-ray emission from the Milky Way and X-ray maps of clusters, we find that the gamma-ray background appears less spherical/more elongated than the expected DM signal from the large majority of halos, and the Galactic gamma ray excess appears very spherical, while the X-ray data would be difficult to distinguish from a DM signal by elongation/sphericity measurements alone.

  3. Characterization of spherical Si by photoluminescence measurement

    NASA Astrophysics Data System (ADS)

    Nagai, Takehiko; Liu, Zhengxin; Masuda, Atsushi; Kondo, Michio

    2007-05-01

    Spherical silicon (Si) with a size of ˜1mm diameter was fabricated by the dropping method for the applications of spherical Si solar cells. In this research work, we characterized spherical Si by means of photoluminescence (PL) measurement at 4 and 18K. The horn-type spherical Si crystals, formed under large undercooled conditions without a seeding technique, showed D-band luminescence originating from dislocations, whereas intrinsic PL bands of Si were not observed. In contrast, for the tear-type spherical Si crystals, formed under shadow undercooling by a seeding technique with Si powder, the boron (B) bound and Si intrinsic phonon-assisted PL bands were clearly observed both at 4 and 18K. Moreover, the intensity ratio of B bound exciton band to Si intrinsic phonon-assisted PL band showed good correlation to the minority carrier lifetime measured with microwave photoconductance decay method. These experimental results suggested that the crystallinity of the tear-type spherical Si is significantly improved by the seeding technique compared with the horn-type ones, which contain a large amount of B-related defects.

  4. Perfection and the Bomb: Nuclear Weapons, Teleology, and Motives.

    ERIC Educational Resources Information Center

    Brummett, Barry

    1989-01-01

    Uses Kenneth Burke's theory of perfection to explore the vocabularies of nuclear weapons in United States public discourse and how "the Bomb" as a God term has gained imbalanced ascendancy in centers of power. (MS)

  5. New exact perfect fluid solutions of Einstein's equations. II

    NASA Astrophysics Data System (ADS)

    Uggla, Claes; Rosquist, Kjell

    1990-12-01

    A family of new spatially homogeneous Bianchi type VIh perfect fluid solutions of the Einstein equations is presented. The fluid flow is orthogonal to the spatially homogeneous hypersurfaces, and the pressure is proportional to the energy density.

  6. Senseless demolition in progress, showing destruction of perfectly decent and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Senseless demolition in progress, showing destruction of perfectly decent and recyclable mill building. Problem exacerbated by high value of scrap iron. - Phoenix Iron Company, Rolling Mill, North of French Creek, west of Fairview Avenue, Phoenixville, Chester County, PA

  7. Perfection and the Bomb: Nuclear Weapons, Teleology, and Motives.

    ERIC Educational Resources Information Center

    Brummett, Barry

    1989-01-01

    Uses Kenneth Burke's theory of perfection to explore the vocabularies of nuclear weapons in United States public discourse and how "the Bomb" as a God term has gained imbalanced ascendancy in centers of power. (MS)

  8. Perfect Actions ---From the Theoretical Background to Recent Developments ---

    NASA Astrophysics Data System (ADS)

    Hasenfratz, P.

    This lecture note starts with a pedagogical introduction to the theoretical background and properties of perfect actions and ends with a discussion on the recent developments concerning chiral symmetry.

  9. Geodesic family of spherical instantons and cosmic quantum creation

    NASA Astrophysics Data System (ADS)

    Lapiedra, Ramon; Morales-Lladosa, Juan Antonio

    2015-09-01

    The Einstein field equations for any spherically symmetric metric and a geodesic perfect fluid source are cast in a canonical simple form, both for Lorentzian metrics and for instantons. Both kinds of metrics are explicitly written for the Lemaître-Tolman-Bondi family and for a general -Friedmann-Lemaître-Robertson-Walker universe. In the latter case (including of course the instanton version) we study whether the probability of quantum creation of our Universe vanishes or not. It is found, in accordance with previous results, that only the closed model can have a nonzero probability for quantum creation. To obtain this result, we resort to general assumptions, which are satisfied in the particular creation case considered by Vilenkin. On the other hand, Fomin and Tryon suggested that the energy of a quantically creatable universe should vanish. This is in accordance with the above result in which only the closed FLRW model is quantically creatable while the open and flat models are not. That is so since it can be seen that this closed model has vanishing energy while the open model and the limiting flat case (suitably perturbed) have both infinite energy.

  10. HUBBLE TRACKS 'PERFECT STORM' ON MARS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Two dramatically different faces of our Red Planet neighbor appear in these comparison images showing how a global dust storm engulfed Mars with the onset of Martian spring in the Southern Hemisphere. When NASA's Hubble Space Telescope imaged Mars in June, the seeds of the storm were caught brewing in the giant Hellas Basin (oval at 4 o'clock position on disk) and in another storm at the northern polar cap. When Hubble photographed Mars in early September, the storm had already been raging across the planet for nearly two months obscuring all surface features. The fine airborne dust blocks a significant amount of sunlight from reaching the Martian surface. Because the airborne dust is absorbing this sunlight, it heats the upper atmosphere. Seasonal global Mars dust storms have been observed from telescopes for over a century, but this is the biggest storm ever seen in the past several decades. Mars looks gibbous in the right photograph because it is 26 million miles farther from Earth than in the left photo (though the pictures have been scaled to the same angular size), and our viewing angle has changed. The left picture was taken when Mars was near its closest approach to Earth for 2001 (an event called opposition); at that point the disk of Mars was fully illuminated as seen from Earth because Mars was exactly opposite the Sun. Both images are in natural color, taken with Hubble's Wide Field Planetary Camera 2. Credit: NASA, James Bell (Cornell Univ.), Michael Wolff (Space Science Inst.), and the Hubble Heritage Team (STScI/AURA)

  11. Spherical classification of wavelet transformed EMG intensity patterns.

    PubMed

    von Tscharner, Vinzenz

    2009-10-01

    Electromyograms of different muscles can be submitted to a wavelet-transform and arranged in a Multi-Muscle Pattern (MMP). The MMP represents the intensity of the EMG signals of a number of muscles simultaneously in time/frequency space. As previously shown, the MMPs can be represented by points in an Euclidian vector space that was called pattern space. The variability of the MMPs is represented by the distribution of the scattered points in pattern space. The purpose of this study was to investigate the distribution of the points and use the properties of the distribution to classify MMPs. The first task was to test whether the points representing a group of MMPs were located between the inner and outer boundary of a sphere-like domain in whitened pattern space as theoretically predicted. The mean of these points and thus of the MMPs is represented by a point at the center of the sphere. The hypothesis was that the spheres representing points of the MMPs of barefoot and shod runners were sufficiently separated and distinguishable in pattern space to allow classification of the runners according to their shod condition. The results confirmed the hypothesis and revealed that the recognition rate was over 80%. One can conclude and generalize that the points representing MMPs recorded for a certain condition reside between the inner and outer boundary of the sphere. The classification based on the spherical feature represents a much better discrimination than one based on the distance from the mean.

  12. Competitive interaction between two different spherical sinks

    NASA Astrophysics Data System (ADS)

    McDonald, Nyrée; Strieder, William

    2004-10-01

    Competitive interactions within diverse mixed populations of chemically active sites are prevalent throughout nature, science, and engineering. Their effects are readily seen in the distribution of dead and surviving aerobic cells within a thick biofilm and particle shape changes during the growth and coarsening of crystals. Even in the most dilute case, competition for a reactant requires at least two spheres/cells, and the solution of the two-spherical sink problem is of interest for several reasons. The solution accurately describes lower cell concentration behavior (108 cells/l), and like the Smoluchowski diffusion-reaction treatment for a single sphere, the analysis is extremely helpful in understanding the fundamental phenomena of the effect on the first spherical sink of the presence of a second different spherical sink. In addition these exact solutions are required for the systematic extension to higher density behavior by rigorous expansions in the spherical sink densities. The method of the twin spherical expansion is used with a formal matrix elimination scheme to generate an exact solution for two distinct spherical sinks of differing sizes and kinetics. The two sinks exist in a medium, which supplies a reactant to the sinks via Fickian diffusion. The two sinks compete for the same reactant with different first-order reactions occurring at the surface of each sink. Earlier work focused on two spherical sinks of the same size with identical surface reaction kinetics. This work has been advanced to allow for diversity in the theory of cellular or reactive sink competition. A number of interesting higher order interactive phenomena are observed in this paper when the different reactive sinks are in close proximity.

  13. Numerical study of an ultra-broadband near-perfect solar absorber in the visible and near-infrared region.

    PubMed

    Wu, Dong; Liu, Chang; Liu, Yumin; Yu, Li; Yu, Zhongyuan; Chen, Lei; Ma, Rui; Ye, Han

    2017-02-01

    We propose and numerically investigate a novel ultra-broadband solar absorber by applying iron in a 2D simple metamaterial structure. The proposed structure can achieve the perfect absorption above 95% covering the wavelength range from 400 to 1500 nm. The average absorption reaches 97.8% over this wavelength range. The broadband perfect absorption is caused by the excitation of localized surface plasmon resonance and propagating surface plasmon resonance. We first propose and demonstrate that the iron is obviously beneficial to achieve impedance matching between the metamaterial structure and the free space over an ultra-broad frequency band in the visible and near-infrared region, which play an extremely important role to generate an ultra-broadband perfect absorption. In order to further broaden the absorption band, we also demonstrate the perfect absorption exceeding 92% for the 400-2000 nm range by adding the number of metal-dielectric pairs and using both gold and iron simultaneously in the proposed structure. The average absorption of the improved absorber reaches 96.4% over the range of 400-2000 nm. The metamaterial absorbers using iron are very promising for many applications, which can greatly broaden the perfect absorption band in the solar spectrum and, meanwhile, can enormously reduce the cost in the actual production.

  14. Comparison of the laser spot movement inside cylindrical and spherical hohlraums

    NASA Astrophysics Data System (ADS)

    Li, Zhichao; Yang, Dong; Li, Sanwei; Huo, Wen Yi; Lan, Ke; Liu, Jie; Ren, Guoli; Chen, Yao-Hua; Yang, Zhiwen; Guo, Liang; Hou, Lifei; Xie, Xuefei; Li, Yukun; Deng, Keli; Yuan, Zheng; Zhan, Xiayu; Yuan, Guanghui; Zhang, Haijun; Jiang, Baibin; Huang, Lizhen; Du, Kai; Zhao, Runchang; Li, Ping; Wang, Wei; Su, Jingqin; Jiang, Shaoen; Ding, Yongkun; He, Xian-Tu; Zhang, Weiyan

    2017-07-01

    Compared with cylindrical hohlraums, the octahedral spherical hohlraums have natural superiority in maintaining high radiation symmetry during the whole capsule implosion process in indirect drive inertial confinement fusion. However, the narrow space between laser beams and the hohlraum wall may disturb laser propagation inside the spherical hohlraum. In this work, the laser propagation inside the spherical hohlraum and cylindrical hohlraum is investigated experimentally by measuring laser spot movement at the SGIII-prototype laser facility. The experimental results show that the laser propagations inside the spherical hohlraum and the cylindrical hohlraum are totally different from each other due to different hohlraum structures. For the spherical hohlraum, although the laser energy is mainly deposited in the initial position of the laser spot during the whole laser pulse, some laser energies are absorbed by the ablated plasmas from the hohlraum wall. Because the laser beam is refracted by the thin plasmas near the laser entrance hole (LEH) region, the laser spot in the spherical hohlraum moves toward the opposite LEH. In contrast, the laser spot in the cylindrical hohlraum moves toward the LEH along the laser path due to the plasma expansion. When the laser is to be turned off, the accumulated plasmas near the LEH region in the cylindrical hohlraum absorb a majority of laser energy and hinder the laser arriving at the appointed position on the hohlraum wall.

  15. Summation by parts methods for spherical harmonic decompositions of the wave equation in any dimensions

    NASA Astrophysics Data System (ADS)

    Gundlach, Carsten; Martín-García, José M.; Garfinkle, David

    2013-07-01

    We investigate numerical methods for wave equations in n + 2 spacetime dimensions, written in spherical coordinates, decomposed in spherical harmonics on Sn, and finite-differenced in the remaining coordinates r and t. Such an approach is useful when the full physical problem has spherical symmetry, for perturbation theory about a spherical background, or in the presence of boundaries with spherical topology. The key numerical difficulty arises from lower order 1/r terms at the origin r = 0. As a toy model for this, we consider the flat space linear wave equation in the form \\dot{\\pi }=\\psi ^{\\prime }+p\\psi /r, \\dot{\\psi }=\\pi ^{\\prime }, where p = 2l + n and l is the leading spherical harmonic index. We propose a class of summation by parts (SBP) finite-differencing methods that conserve a discrete energy up to boundary terms, thus guaranteeing stability and convergence in the energy norm. We explicitly construct SBP schemes that are second- and fourth-order accurate at interior points and the symmetry boundary r = 0, and first- and second-order accurate at the outer boundary r = R.

  16. Spherical Coordinate Systems for Streamlining Suited Mobility Analysis

    NASA Technical Reports Server (NTRS)

    Benson, Elizabeth; Cowley, Matthew; Harvill, Lauren; Rajulu. Sudhakar

    2015-01-01

    demonstrated that a spherical coordinate system is helpful in describing and visualizing the motion of a space suit. The system is particularly useful in describing the motion of the shoulder, where multiple degrees of freedom can lead to very complex motion paths.

  17. Scientists Track 'Perfect Storm' on Mars

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Two dramatically different faces of our Red Planet neighbor appear in these comparison images showing how a global dust storm engulfed Mars with the onset of Martian spring in the Southern Hemisphere. When NASA's Hubble Space Telescope imaged Mars in June, the seeds of the storm were caught brewing in the giant Hellas Basin (oval at 4 o'clock position on disk) and in another storm at the northern polar cap.

    When Hubble photographed Mars in early September, the storm had already been raging across the planet for nearly two months obscuring all surface features. The fine airborne dust blocks a significant amount of sunlight from reaching the Martian surface. Because the airborne dust is absorbing this sunlight, it heats the upper atmosphere. Seasonal global Mars dust storms have been observed from telescopes for over a century, but this is the biggest storm ever seen in the past several decades.

    Mars looks gibbous in the right photograph because it is 26 million miles farther from Earth than in the left photo (though the pictures have been scaled to the same angular size), and our viewing angle has changed. The left picture was taken when Mars was near its closest approach to Earth for 2001 (an event called opposition); at that point the disk of Mars was fully illuminated as seen from Earth because Mars was exactly opposite the Sun.

    Both images are in natural color, taken with Hubble's Wide Field Planetary Camera 2.

  18. How perfect can protein interactomes be?

    PubMed

    Levy, Emmanuel D; Landry, Christian R; Michnick, Stephen W

    2009-03-03

    Any engineered device should certainly not contain nonfunctional components, for this would be a waste of energy and money. In contrast, evolutionary theory tells us that biological systems need not be optimized and may very well accumulate nonfunctional elements. Mutational and demographic processes contribute to the cluttering of eukaryotic genomes and transcriptional networks with "junk" DNA and spurious DNA binding sites. Here, we question whether such a notion should be applied to protein interactomes-that is, whether these protein interactomes are expected to contain a fraction of nonselected, nonfunctional protein-protein interactions (PPIs), which we term "noisy." We propose a simple relationship between the fraction of noisy interactions expected in a given organism and three parameters: (i) the number of mutations needed to create and destroy interactions, (ii) the size of the proteome, and (iii) the fitness cost of noisy interactions. All three parameters suggest that noisy PPIs are expected to exist. Their existence could help to explain why PPIs determined from large-scale studies often lack functional relationships between interacting proteins, why PPIs are poorly conserved across organisms, and why the PPI space appears to be immensely large. Finally, we propose experimental strategies to estimate the fraction of evolutionary noise in PPI networks.

  19. Scientists Track 'Perfect Storm' on Mars

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Two dramatically different faces of our Red Planet neighbor appear in these comparison images showing how a global dust storm engulfed Mars with the onset of Martian spring in the Southern Hemisphere. When NASA's Hubble Space Telescope imaged Mars in June, the seeds of the storm were caught brewing in the giant Hellas Basin (oval at 4 o'clock position on disk) and in another storm at the northern polar cap.

    When Hubble photographed Mars in early September, the storm had already been raging across the planet for nearly two months obscuring all surface features. The fine airborne dust blocks a significant amount of sunlight from reaching the Martian surface. Because the airborne dust is absorbing this sunlight, it heats the upper atmosphere. Seasonal global Mars dust storms have been observed from telescopes for over a century, but this is the biggest storm ever seen in the past several decades.

    Mars looks gibbous in the right photograph because it is 26 million miles farther from Earth than in the left photo (though the pictures have been scaled to the same angular size), and our viewing angle has changed. The left picture was taken when Mars was near its closest approach to Earth for 2001 (an event called opposition); at that point the disk of Mars was fully illuminated as seen from Earth because Mars was exactly opposite the Sun.

    Both images are in natural color, taken with Hubble's Wide Field Planetary Camera 2.

  20. Recent Progress on Spherical Torus Research

    SciTech Connect

    Ono, Masayuki; Kaita, Robert

    2014-01-01

    The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ~ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ~ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of attractive fusion energy power source. Since the start of the two megaampere class ST facilities in 2000, National Spherical Torus Experiment (NSTX) in the US and Mega Ampere Spherical Tokamak (MAST) in UK, active ST research has been conducted worldwide. More than sixteen ST research facilities operating during this period have achieved remarkable advances in all of fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.