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Sample records for light cone

  1. Berkeley Lighting Cone

    SciTech Connect

    Lask, Kathleen; Gadgil, Ashok

    2016-10-24

    A lighting cone is a simple metal cone placed on the fuel bed of a stove during ignition to act as a chimney, increasing the draft through the fuel bed. Many stoves tend to be difficult to light due to poor draft through the fuel bed, so lighting cones are used in various parts of the world as an inexpensive accessory to help with ignition.

  2. Light cone matrix product

    SciTech Connect

    Hastings, Matthew B

    2009-01-01

    We show how to combine the light-cone and matrix product algorithms to simulate quantum systems far from equilibrium for long times. For the case of the XXZ spin chain at {Delta} = 0.5, we simulate to a time of {approx} 22.5. While part of the long simulation time is due to the use of the light-cone method, we also describe a modification of the infinite time-evolving bond decimation algorithm with improved numerical stability, and we describe how to incorporate symmetry into this algorithm. While statistical sampling error means that we are not yet able to make a definite statement, the behavior of the simulation at long times indicates the appearance of either 'revivals' in the order parameter as predicted by Hastings and Levitov (e-print arXiv:0806.4283) or of a distinct shoulder in the decay of the order parameter.

  3. Light-cone quantization of quantum chromodynamics

    SciTech Connect

    Brodsky, S.J. ); Pauli, H.C. )

    1991-06-01

    We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism.

  4. Light-cones, almost light-cones and almost-complex light-cones

    NASA Astrophysics Data System (ADS)

    Newman, Ezra T.

    2017-08-01

    We point out (and then apply to a general situation) an unusual relationship among a variety of null geodesic congruences; (a) the generators of ordinary light-cones and (b) certain (related) shear-free but twisting congruences in Minkowski space-time as well as (c) asymptotically shear-free null geodesic congruences that exist in the neighborhood of Penrose's I^{ +} in Einstein or Einstein-Maxwell asymptotically flat-space-times. We refer to these geodesic congruences respectively as: Lignt-Cones (LCs), as "Almost-Complex"-Light-Cones (ACLCs), [though they are real they resemble complex light-cones in complex Minkowski space] and finally to a family of congruences in asymptotically flat-spaces as ` Almost Light-Cones' (ALC). The two essential points of resemblance among the three families are: (1) they are all either shear-free or asymptotically shear-free and (2) in each family the individual members of the family can be labeled by the points in a real or complex four-dimensional manifold. As an example, the Minkowski space LCs are labeled by the (real) coordinate value of their apex. In the case of (ACLCs) (complex coordinate values), the congruences will have non-vanishing twist whose magnitude is determined by the imaginary part of the complex coordinate values. In studies of gravitational radiation, Bondi-type of null surfaces and their associated Bondi coordinates have been almost exclusively used for calculations. It turns out that some surprising relations arise if, instead of the Bondi coordinates, one uses ALCs and their associated coordinate systems in the analysis of the Einstein-Maxwell equations in the neighborhood of I+. More explicitly and surprisingly, the asymptotic Bianchi Identities (arising directly from the Einstein equations), expressed in the coordinates of the ALCs, turn directly into many of the standard definitions and equations and relations of classical mechanics coupled with Maxwell's equations. These results extend and generalize the

  5. Perturbation theory in light-cone quantization

    SciTech Connect

    Langnau, A.

    1992-01-01

    A thorough investigation of light-cone properties which are characteristic for higher dimensions is very important. The easiest way of addressing these issues is by analyzing the perturbative structure of light-cone field theories first. Perturbative studies cannot be substituted for an analysis of problems related to a nonperturbative approach. However, in order to lay down groundwork for upcoming nonperturbative studies, it is indispensable to validate the renormalization methods at the perturbative level, i.e., to gain control over the perturbative treatment first. A clear understanding of divergences in perturbation theory, as well as their numerical treatment, is a necessary first step towards formulating such a program. The first objective of this dissertation is to clarify this issue, at least in second and fourth-order in perturbation theory. The work in this dissertation can provide guidance for the choice of counterterms in Discrete Light-Cone Quantization or the Tamm-Dancoff approach. A second objective of this work is the study of light-cone perturbation theory as a competitive tool for conducting perturbative Feynman diagram calculations. Feynman perturbation theory has become the most practical tool for computing cross sections in high energy physics and other physical properties of field theory. Although this standard covariant method has been applied to a great range of problems, computations beyond one-loop corrections are very difficult. Because of the algebraic complexity of the Feynman calculations in higher-order perturbation theory, it is desirable to automatize Feynman diagram calculations so that algebraic manipulation programs can carry out almost the entire calculation. This thesis presents a step in this direction. The technique we are elaborating on here is known as light-cone perturbation theory.

  6. Perturbation theory in light-cone quantization

    SciTech Connect

    Langnau, A.

    1992-01-01

    A thorough investigation of light-cone properties which are characteristic for higher dimensions is very important. The easiest way of addressing these issues is by analyzing the perturbative structure of light-cone field theories first. Perturbative studies cannot be substituted for an analysis of problems related to a nonperturbative approach. However, in order to lay down groundwork for upcoming nonperturbative studies, it is indispensable to validate the renormalization methods at the perturbative level, i.e., to gain control over the perturbative treatment first. A clear understanding of divergences in perturbation theory, as well as their numerical treatment, is a necessary first step towards formulating such a program. The first objective of this dissertation is to clarify this issue, at least in second and fourth-order in perturbation theory. The work in this dissertation can provide guidance for the choice of counterterms in Discrete Light-Cone Quantization or the Tamm-Dancoff approach. A second objective of this work is the study of light-cone perturbation theory as a competitive tool for conducting perturbative Feynman diagram calculations. Feynman perturbation theory has become the most practical tool for computing cross sections in high energy physics and other physical properties of field theory. Although this standard covariant method has been applied to a great range of problems, computations beyond one-loop corrections are very difficult. Because of the algebraic complexity of the Feynman calculations in higher-order perturbation theory, it is desirable to automatize Feynman diagram calculations so that algebraic manipulation programs can carry out almost the entire calculation. This thesis presents a step in this direction. The technique we are elaborating on here is known as light-cone perturbation theory.

  7. Hadronic wavefunctions in light-cone quantization

    SciTech Connect

    Hyer, Thomas

    1994-05-01

    The analysis of light-cone wavefunctions seems the most promising theoretical approach to a detailed understanding of the structure of relativistic bound states, particularly hadrons. However, there are numerous complications in this approach. Most importantly, the light-cone approach sacrifices manifest rotational invariance in exchange for the elimination of negative-energy states. The requirement of rotational invariance of the full theory places important constraints on proposed light-cone wavefunctions, whether they are modelled or extracted from some numerical procedure. A formulation of the consequences of the hidden rotational symmetry has been sought for some time; it is presented in Chapter 2. In lattice gauge theory or heavy-quark effective theory, much of the focus is on the extraction of numerical values of operators which are related to the hadronic wavefunction. These operators are to some extent interdependent, with relations induced by fundamental constraints on the underlying wavefunction. The consequences of the requirement of unitarity are explored in Chapter 3, and are found to have startling phenomenological relevance. To test model light-cone wavefunctions, experimental predictions must be made. The reliability of perturbative QCD as a tool for making such predictions has been questioned. In Chapter 4, the author presents a computation of the rates for nucleon-antinucleon annihilation, improving the reliability of the perturbative computation by taking into account the Sudakov suppression of exclusive processes at large transverse impact parameter. In Chapter 5, he develops the analysis of semiexclusive production. This work focuses on processes in which a single isolated meson is produced perturbatively and recoils against a wide hadronizing system. At energies above about 10 GeV, semiexclusive processes are shown to be the most sensitive experimental probes of hadronic structure.

  8. Light-cone observables and gauge-invariance in the geodesic light-cone formalism

    NASA Astrophysics Data System (ADS)

    Scaccabarozzi, Fulvio; Yoo, Jaiyul

    2017-06-01

    The remarkable properties of the geodesic light-cone (GLC) coordinates allow analytic expressions for the light-cone observables, providing a new non-perturbative way for calculating the effects of inhomogeneities in our Universe. However, the gauge-invariance of these expressions in the GLC formalism has not been shown explicitly. Here we provide this missing part of the GLC formalism by proving the gauge-invariance of the GLC expressions for the light-cone observables, such as the observed redshift, the luminosity distance, and the physical area and volume of the observed sources. Our study provides a new insight on the properties of the GLC coordinates and it complements the previous work by the GLC collaboration, leading to a comprehensive description of light propagation in the GLC representation.

  9. Light-cone quantization and hadron structure

    SciTech Connect

    Brodsky, S.J.

    1996-04-01

    Quantum chromodynamics provides a fundamental description of hadronic and nuclear structure and dynamics in terms of elementary quark and gluon degrees of freedom. In practice, the direct application of QCD to reactions involving the structure of hadrons is extremely complex because of the interplay of nonperturbative effects such as color confinement and multi-quark coherence. In this talk, the author will discuss light-cone quantization and the light-cone Fock expansion as a tractable and consistent representation of relativistic many-body systems and bound states in quantum field theory. The Fock state representation in QCD includes all quantum fluctuations of the hadron wavefunction, including fax off-shell configurations such as intrinsic strangeness and charm and, in the case of nuclei, hidden color. The Fock state components of the hadron with small transverse size, which dominate hard exclusive reactions, have small color dipole moments and thus diminished hadronic interactions. Thus QCD predicts minimal absorptive corrections, i.e., color transparency for quasi-elastic exclusive reactions in nuclear targets at large momentum transfer. In other applications, such as the calculation of the axial, magnetic, and quadrupole moments of light nuclei, the QCD relativistic Fock state description provides new insights which go well beyond the usual assumptions of traditional hadronic and nuclear physics.

  10. Light-Front-Quantized QCD in Light-Cone Gauge

    SciTech Connect

    Brodsky, Stanley J.

    2000-11-30

    The light-front (LF) quantization of QCD in light-cone gauge has a number of remarkable advantages, including explicit unitarity, a physical Fock expansion, the absence of ghost degrees of freedom, and the decoupling properties needed to prove factorization theorems in high momentum transfer inclusive and exclusive reactions. We present a systematic study of LF-quantized gauge theory following the Dirac method and construct the Dyson-Wick S-matrix expansion based on LF-time-ordered products. The gauge field is shown to satisfy the Lorentz condition as an operator equation as well as the light-cone gauge condition. Its propagator is found to be transverse with respect to both its four-momentum and the gauge direction. The propagator of the dynamical + part of the free fermionic field is shown to be causal and to not contain instantaneous terms. The interaction Hamiltonian of QCD can be expressed in a form resembling that of covariant theory, except for additional instantaneous interactions which can be treated systematically. The renormalization factors are shown to be scalars and we find Z1 = Z3 at one loop order. The running coupling constant and QCD {beta} function are also computed in the noncovariant light-cone gauge. Some comments on the relationship of our LF framework to the analytic effective charge and renormalization scheme defined by the pinch technique are made. LF quantization thus provides a consistent formulation of gauge theory, despite the fact that the hyperplanes x{sup {+-}} = 0 used to impose boundary conditions constitute characteristic surfaces of a hyperbolic partial differential equation.

  11. Light-cone averaging in cosmology: formalism and applications

    NASA Astrophysics Data System (ADS)

    Gasperini, M.; Marozzi, G.; Nugier, F.; Veneziano, G.

    2011-07-01

    We present a general gauge invariant formalism for defining cosmological averages that are relevant for observations based on light-like signals. Such averages involve either null hypersurfaces corresponding to a family of past light-cones or compact surfaces given by their intersection with timelike hypersurfaces. Generalized Buchert-Ehlers commutation rules for derivatives of these light-cone averages are given. After introducing some adapted ``geodesic light-cone'' coordinates, we give explicit expressions for averaging the redshift to luminosity-distance relation and the so-called ``redshift drift'' in a generic inhomogeneous Universe.

  12. Light-cone averaging in cosmology: formalism and applications

    SciTech Connect

    Gasperini, M.; Marozzi, G.; Veneziano, G.; Nugier, F. E-mail: giovanni.marozzi@college-de-france.fr E-mail: gabriele.veneziano@cern.ch

    2011-07-01

    We present a general gauge invariant formalism for defining cosmological averages that are relevant for observations based on light-like signals. Such averages involve either null hypersurfaces corresponding to a family of past light-cones or compact surfaces given by their intersection with timelike hypersurfaces. Generalized Buchert-Ehlers commutation rules for derivatives of these light-cone averages are given. After introducing some adapted ''geodesic light-cone'' coordinates, we give explicit expressions for averaging the redshift to luminosity-distance relation and the so-called ''redshift drift'' in a generic inhomogeneous Universe.

  13. Light-cone coordinates based at a geodesic world line

    SciTech Connect

    Preston, Brent; Poisson, Eric

    2006-09-15

    Continuing work initiated in an earlier publication [Phys. Rev. D 69, 084007 (2004)], we construct a system of light-cone coordinates based at a geodesic world line of an arbitrary curved spacetime. The construction involves (i) an advanced-time or a retarded-time coordinate that labels past or future light cones centered on the world line (ii) a radial coordinate that is an affine parameter on the null generators of these light cones, and (iii) angular coordinates that are constant on each generator. The spacetime metric is calculated in the light-cone coordinates, and it is expressed as an expansion in powers of the radial coordinate in terms of the irreducible components of the Riemann tensor evaluated on the world line. The formalism is illustrated in two simple applications, the first involving a comoving world line of a spatially flat cosmology, the other featuring an observer placed on the axis of symmetry of Melvin's magnetic universe.

  14. Light-cone quantized QCD in 1 + 1 dimensions

    SciTech Connect

    Hornbostel, K.; Brodsky, S.J.; Pauli, H.C.

    1988-10-01

    The QCD light-cone Hamiltonian is diagonalized in a discrete momentum-space basis. The spectra and wavefunctions for various coupling constants, numbers of color, and baryon number are computed. 20 refs., 8 figs.

  15. Enhanced light trapping in periodically truncated cone silicon nanowire structure

    NASA Astrophysics Data System (ADS)

    Kai, Qiu; Yuhua, Zuo; Tianwei, Zhou; Zhi, Liu; Jun, Zheng; Chuanbo, Li; Buwen, Cheng

    2015-10-01

    Light trapping plays an important role in improving the conversion efficiency of thin-film solar cells. The good wideband light trapping is achieved using our periodically truncated cone Si nanowire (NW) structures, and their inherent mechanism is analyzed and simulated by FDTD solution software. Ordered cylinder Si NW structure with initial size of 80 nm and length of 200 nm is grown by pattern transfer and selective epitaxial growth. Truncated cone Si NW array is then obtained by thermal oxidation treatment. Its mean reflection in the range of 300-900 nm is lowered to be 5% using 140 nm long truncated cone Si NW structure, compared with that of 20% using cylinder counterparts. It indicates that periodically truncated Si cone structures trap the light efficiently to enhance the light harvesting in a wide spectral range and have the potential application in highly efficient NW solar cells. Project supported by the National Natural Science Foundation of China (Nos. 51072194, 61021003, 61036001, 61376057).

  16. New Light on Growth Cone Navigation.

    PubMed

    Pollard, Thomas D

    2015-12-21

    Growth cones on neuronal process navigate over long distances to their targets in the developing nervous system. New work by Menon et al., 2015 in the current issue of Developmental Cell reveals that reversible ubiquitination of the actin filament polymerase called VASP is part of the guidance system. Copyright © 2015 Elsevier Inc. All rights reserved.

  17. Light-cone gauge for black-hole perturbation theory

    SciTech Connect

    Preston, Brent; Poisson, Eric

    2006-09-15

    The geometrical meaning of the Eddington-Finkelstein coordinates of Schwarzschild spacetime is well understood: (i) the advanced-time coordinate v is constant on incoming light cones that converge toward r=0 (ii) the angles {theta} and {phi} are constant on the null generators of each light cone (iii) the radial coordinate r is an affine-parameter distance along each generator, and (iv) r is an areal radius, in the sense that 4{pi}r{sup 2} is the area of each two-surface (v,r)=constant. The light-cone gauge of black-hole perturbation theory, which is formulated in this paper, places conditions on a perturbation of the Schwarzschild metric that ensure that properties (i)-(iii) of the coordinates are preserved in the perturbed spacetime. Property (iv) is lost, in general, but it is retained in exceptional situations that are identified in this paper. Unlike other popular choices of gauge, the light-cone gauge produces a perturbed metric that is expressed in a meaningful coordinate system; this is a considerable asset that greatly facilitates the task of extracting physical consequences. We illustrate the use of the light-cone gauge by calculating the metric of a black hole immersed in a uniform magnetic field. We construct a three-parameter family of solutions to the perturbative Einstein-Maxwell equations and argue that it is applicable to a broader range of physical situations than the exact, two-parameter Schwarzschild-Melvin family.

  18. String/flux tube duality on the light cone

    SciTech Connect

    Brower, Richard C.; Tan, C.-I; Thorn, Charles B.

    2006-06-15

    The equivalence of quantum field theory and string theory as exemplified by the AdS/CFT correspondence is explored from the point of view of light cone quantization. On the string side we discuss the light cone version of the static string connecting a heavy external quark source to a heavy external antiquark source, together with small oscillations about the static string configuration. On the field theory side we analyze the weak/strong coupling transition in a ladder diagram model of the quark-antiquark system, also from the point of view of the light cone. Our results are completely consistent with those obtained by more standard covariant methods in the limit of infinitely massive quarks.

  19. Light-cone Wilson loop in classical lattice gauge theory

    NASA Astrophysics Data System (ADS)

    Laine, M.; Rothkopf, A.

    2013-07-01

    The transverse broadening of an energetic jet passing through a non-Abelian plasma is believed to be described by the thermal expectation value of a light-cone Wilson loop. In this exploratory study, we measure the light-cone Wilson loop with classical lattice gauge theory simulations. We observe, as suggested by previous studies, that there are strong interactions already at short transverse distances, which may lead to more efficient jet quenching than in leading-order perturbation theory. We also verify that the asymptotics of the Wilson loop do not change qualitatively when crossing the light cone, which supports arguments in the literature that infrared contributions to jet quenching can be studied with dimensionally reduced simulations in the space-like domain. Finally we speculate on possibilities for full four-dimensional lattice studies of the same observable, perhaps by employing shifted boundary conditions in order to simulate ensembles boosted by an imaginary velocity.

  20. QCD Technology: Light-Cone Quantization and Commensurate Scale Relations

    SciTech Connect

    Brodsky, Stanley J.

    1999-09-03

    I discuss several theoretical tools which are useful for analyzing perturbative and non-perturbative problems in quantum chromodynamics, including (a) the light-cone Fock expansion, (b) the effective charge {alpha}{sub v}, (c) conformal symmetry, and (d) commensurate scale relations. Light-cone Fock-state wavefunctions encode the properties of a hadron in terms of its fundamental quark and gluon degrees of freedom. Given the proton's light-cone wavefunctions, one can compute not only the quark and gluon distributions measured in deep inelastic lepton-proton scattering, but also the multi-parton correlations which control the distribution of particles in the proton fragmentation region and dynamical higher twist effects. Light-cone wavefunctions also provide a systematic framework for evaluating exclusive hadronic matrix elements, including timelike heavy hadron decay amplitudes and form factors. The {alpha}{sub v} coupling, defined from the QCD heavy quark potential, provides a physical expansion parameter for perturbative QCD with an analytic dependence on the fermion masses which is now known to two-loop order. Conformal symmetry provides a template for QCD predictions, including relations between observables which are present even in a theory which is not scale invariant. Commensurate scale relations are perturbative QCD predictions based on conformal symmetry relating observable to observable at fixed relative scale. Such relations have no renormalization scale or scheme ambiguity.

  1. Riemannian light cone from vanishing birefringence in premetric vacuum electrodynamics

    SciTech Connect

    Laemmerzahl, Claus; Hehl, Friedrich W.

    2004-11-15

    We consider premetric electrodynamics with a local and linear constitutive law for the vacuum. Within this framework, we find quartic Fresnel wave surfaces for the propagation of light. If we require (i) the Fresnel equation to have only real solutions and (ii) the vanishing of birefringence in vacuum, then a Riemannian light cone is implied. No proper Finslerian structure can occur. This is generalized to dynamical equations of any order.

  2. The one loop gluon emission light cone wave function

    NASA Astrophysics Data System (ADS)

    Lappi, T.; Paatelainen, R.

    2017-04-01

    Light cone perturbation theory has become an essential tool to calculate cross sections for various small- x dilute-dense processes such as deep inelastic scattering and forward proton-proton and proton-nucleus collisions. Here we set out to do one loop calculations in an explicit helicity basis in the four dimensional helicity scheme. As a first process we calculate light cone wave function for one gluon emission to one-loop order in Hamiltonian perturbation theory on the light front. We regulate ultraviolet divergences with transverse dimensional regularization and soft divergences using a cut-off on longitudinal momentum. We show that when all the renormalization constants are combined, the ultraviolet divergences can be absorbed into the standard QCD running coupling constant, and give an explicit expression for the remaining finite part.

  3. Light-cone fluctuations in the cosmic string spacetime

    NASA Astrophysics Data System (ADS)

    Mota, H. F.; Bezerra de Mello, E. R.; Bessa, C. H. G.; Bezerra, V. B.

    2016-07-01

    In this paper we consider light-cone fluctuations arising as a consequence of the nontrivial topology of the locally flat cosmic string spacetime. By setting the light-cone along the z -direction we are able to develop a full analysis to calculate the renormalized graviton two-point function, as well as the mean square fluctuation in the geodesic interval function and the time delay (or advance) in the propagation of a light pulse. We found that all these expressions depend upon the parameter characterizing the conical topology of the cosmic string spacetime and vanish in the absence of it. We also point out that at large distances from the cosmic string the mean square fluctuation in the geodesic interval function is extremely small while in the opposite limit it logarithmically increases.

  4. Reflection of a polarized light cone

    NASA Astrophysics Data System (ADS)

    Brody, Jed; Weiss, Daniel; Berland, Keith

    2013-01-01

    We introduce a visually appealing experimental demonstration of Fresnel reflection. In this simple optical experiment, a polarized light beam travels through a high numerical-aperture microscope objective, reflects off a glass slide, and travels back through the same objective lens. The return beam is sampled with a polarizing beam splitter and produces a surprising geometric pattern on an observation screen. Understanding the origin of this pattern requires careful attention to geometry and an understanding of the Fresnel coefficients for S and P polarized light. We demonstrate that in addition to a relatively simple experimental implementation, the shape of the observed pattern can be computed both analytically and by using optical modeling software. The experience of working through complex mathematical computations and demonstrating their agreement with a surprising experimental observation makes this a highly educational experiment for undergraduate optics or advanced-lab courses. It also provides a straightforward yet non-trivial system for teaching students how to use optical modeling software.

  5. The second moment of the pion light cone wave function

    SciTech Connect

    Luigi del Debbio; Massimo di Pierro; Alex Dougall

    2003-09-25

    We present a preliminary result for second moment of the light cone wave function of the pion. This parameter is the subject of a discrepancy between theoretical predictions (coming from lattice and sum rules) and a recent experimental result (that remarkably agrees with purely perturbative predictions). In this work we exploit lattice hypercubic symmetries to remove power divergences and, moreover, implement a full 1-loop matching for all the contributing operators.

  6. Structure of the Nucleon Spin on the Light Cone

    SciTech Connect

    Pasquini, B.

    2008-10-13

    The spin structure of the nucleon is studied in a light-cone description of the nucleon where the Fock expansion is truncated to consider only valence quarks. Transverse momentum dependent parton distributions and transverse-spin densities, defined through the generalized parton distributions in the impact parameter space, are investigated as new tools to reveal the spin-spin and spin-orbit correlations for different quark and nucleon polarizations.

  7. Threshold pion photoproduction in a light-cone quark model

    NASA Astrophysics Data System (ADS)

    Konen, W.; Drechsel, D.

    1991-07-01

    The instantaneous and seagull graphs are calculated for pion photoproduction in a relativistic light-cone model of the nucleon. In both pseudoscalar and pseudovector coupling we find the ratios A (-): A (0): A (+) = 1: ( {-1}/{2}μ):( {-9}/{5}μ) in the nonrelativistic limit. These results correspond to the sum of seagull and Z-graph in the nonrelativistic quark model. In pseudovector coupling also the numerical results for realistic-model parameters are close to those values.

  8. Generalized heavy-to-light form factors in light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Meißner, Ulf-G.; Wang, Wei

    2014-03-01

    We study the form factors for a heavy meson into the S-wave Kπ/ππ system with an invariant mass below 1 GeV. The mesonic final state interactions are described in terms of the scalar form factors, which are obtained from unitarized chiral perturbation theory. Employing generalized light-cone distribution amplitudes, we compute the heavy-to-light transition using light-cone sum rules. Our approach simultaneously respects constraints from analyticity and unitarity, and also takes advantage of the power expansion in the 1/mb and the strong coupling constant.

  9. Light-cone averages in a Swiss-cheese universe

    NASA Astrophysics Data System (ADS)

    Marra, Valerio; Kolb, Edward W.; Matarrese, Sabino

    2008-01-01

    We analyze a toy Swiss-cheese cosmological model to study the averaging problem. In our Swiss-cheese model, the cheese is a spatially flat, matter only, Friedmann-Robertson-Walker solution (i.e., the Einstein-de Sitter model), and the holes are constructed from a Lemaître-Tolman-Bondi solution of Einstein’s equations. We study the propagation of photons in the Swiss-cheese model, and find a phenomenological homogeneous model to describe observables. Following a fitting procedure based on light-cone averages, we find that the expansion scalar is unaffected by the inhomogeneities (i.e., the phenomenological homogeneous model is the cheese model). This is because of the spherical symmetry of the model; it is unclear whether the expansion scalar will be affected by nonspherical voids. However, the light-cone average of the density as a function of redshift is affected by inhomogeneities. The effect arises because, as the universe evolves, a photon spends more and more time in the (large) voids than in the (thin) high-density structures. The phenomenological homogeneous model describing the light-cone average of the density is similar to the ΛCDM concordance model. It is interesting that, although the sole source in the Swiss-cheese model is matter, the phenomenological homogeneous model behaves as if it has a dark-energy component. Finally, we study how the equation of state of the phenomenological homogeneous model depends on the size of the inhomogeneities, and find that the equation-of-state parameters w0 and wa follow a power-law dependence with a scaling exponent equal to unity. That is, the equation of state depends linearly on the distance the photon travels through voids. We conclude that, within our toy model, the holes must have a present size of about 250 Mpc to be able to mimic the concordance model.

  10. Azimuthal spin asymmetries in light-cone constituent quark models

    SciTech Connect

    Boffi, S.; Pasquini, B.; Efremov, A. V.; Schweitzer, P.

    2009-05-01

    We present results for all leading-twist azimuthal spin asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to T-even transverse-momentum dependent parton distribution functions on the basis of a light-cone constituent quark model. Attention is paid to discuss the range of applicability of the model, especially with regard to the scale dependence of the observables and the transverse-momentum dependence of the distributions. We find good agreement with available experimental data and present predictions to be further tested by future CLAS, COMPASS, and HERMES data.

  11. Light-Cone Sum Rule Approach for Baryon Form Factors

    NASA Astrophysics Data System (ADS)

    Offen, Nils

    2016-10-01

    We present the state-of-the-art of the light-cone sum rule approach to Baryon form factors. The essence of this approach is that soft Feynman contributions are calculated in terms of small transverse distance quantities using dispersion relations and duality. The form factors are thus expressed in terms of nucleon wave functions at small transverse separations, called distribution amplitudes, without any additional parameters. The distribution amplitudes, therefore, can be extracted from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations.

  12. Entanglement swapping, light cones and elements of reality

    NASA Astrophysics Data System (ADS)

    Broadbent, Anne; Méthot, André Allan

    2007-05-01

    Recently, a number of two-participant all-versus-nothing Bell experiments have been proposed. Here, we give local realistic explanations for these experiments. More precisely, we examine the scenario where a participant swaps his entanglement with two other participants and then is removed from the experiment; we also examine the scenario where two particles are in the same light cone, i.e. belong to a single participant. Our conclusion is that, in both cases, the proposed experiments are not convincing proofs against local realism.

  13. Light-cone M5 and multiple M2-branes

    NASA Astrophysics Data System (ADS)

    Bandos, Igor A.; Townsend, Paul K.

    2008-12-01

    We present the light-cone gauge fixed Lagrangian for the M5-brane; it has a residual 'exotic' gauge invariance with the group of 5-volume preserving diffeomorphisms, SDiff5, as gauge group. For an M5-brane of topology \\bb{R}^2\\times M_3 , for closed 3-manifold M3, we find an infinite tension limit that yields an SO(8)-invariant (1 + 2)-dimensional field theory with 'exotic' SDiff3 gauge invariance. We show that this field theory is the Carrollian limit of the Nambu bracket realization of the 'BLG' model for multiple M2-branes.

  14. Geodesic-light-cone coordinates and the Bianchi I spacetime

    NASA Astrophysics Data System (ADS)

    Fleury, Pierre; Nugier, Fabien; Fanizza, Giuseppe

    2016-06-01

    The geodesic-light-cone (GLC) coordinates are a useful tool to analyse light propagation and observations in cosmological models. In this article, we propose a detailed, pedagogical, and rigorous introduction to this coordinate system, explore its gauge degrees of freedom, and emphasize its interest when geometric optics is at stake. We then apply the GLC formalism to the homogeneous and anisotropic Bianchi I cosmology. More than a simple illustration, this application (i) allows us to show that the Weinberg conjecture according to which gravitational lensing does not affect the proper area of constant-redshift surfaces is significantly violated in a globally anisotropic universe; and (ii) offers a glimpse into new ways to constrain cosmic isotropy from the Hubble diagram.

  15. Light-cone distribution amplitudes for heavy-quark hadrons

    NASA Astrophysics Data System (ADS)

    Bell, Guido; Feldmann, Thorsten; Wang, Yu-Ming; Yip, Matthew W. Y.

    2013-11-01

    We construct parametrizations of light-cone distribution amplitudes (LCDAs) for B-mesons and Λ b -baryons that obey various theoretical constraints, and which are simple to use in factorization theorems relevant for phenomenological applications in heavy-flavour physics. In particular, we find the eigenfunctions of the Lange-Neubert renormalization kernel, which allow for a systematic implementation of renormalization-group evolution effects for both B-meson and Λ b -baryon decays. We also present a new strategy to construct LCDA models from momentum-space projectors, which can be used to implement Wandzura-Wilczek-like relations, and which allow for a comparison with theoretical approaches that go beyond the collinear limit for the light-quark momenta in energetic heavy-hadron decays.

  16. Light-cone gauge for 1 + 1 strings

    NASA Astrophysics Data System (ADS)

    Smith, Eric

    1992-09-01

    Explicit construction of the light-cone gauge quantum theory of bosonic strings in 1 + 1 space-time dimensions reveals unexpected structures. One is the existence of a gauge choice that gives a free action at the price of propagating ghosts and a nontrivial BRST charge. Fixing this gauge leaves a U(1) Kac-Moody algebra of residual symmetry, generated by a conformal tensor of rank two and a conformal scalar. Another is that the BRST charge made from these currents is nilpotent when the action includes a linear dilaton background, independent of the particular value of the dilaton gradient. Space-time Lorentz invariance in this theory is still elusive, however, because of the linear dilaton background and the nature of the gauge symmetries.

  17. Equivalence of light-cone and conformal gauges in two-dimensional quantum gravity

    SciTech Connect

    Ahn, G.J.; Kim, W.T.; Park, Y.J.; Kim, K.Y. )

    1992-08-20

    In this paper, the authors show that the light-cone and conformal gauges are equivalent in the sense that the well known SL(2,R) current structure in the light-cone gauge is obtained from the results in the conformal one under a proper coordinate transformation. This result is due to the residual symmetry of the scalar field [Phi].

  18. Worldsheet theory of light-cone gauge noncritical strings on higher genus Riemann surfaces

    NASA Astrophysics Data System (ADS)

    Ishibashi, Nobuyuki; Murakami, Koichi

    2016-06-01

    It is possible to formulate light-cone gauge string field theory in noncritical dimensions. Such a theory corresponds to conformal gauge worldsheet theory with nonstandard longitudinal part. We study the longitudinal part of the worldsheet theory on higher genus Riemann surfaces. The results in this paper shall be used to study the dimensional regularization of light-cone gauge string field theory.

  19. The light-cone Fock state expansion and hadron physics phenomenology

    SciTech Connect

    Brodsky, S.J.

    1997-06-01

    The light-cone Fock expansion is defined in the following way: one first constructs the light-cone time evolution operator and the invariant mass operator in light-cone gauge from the QCD Lagrangian. The total longitudinal momentum and transverse momenta are conserved, i.e. are independent of the interactions. The matrix elements of the invariant mass operator on the complete orthonormal basis of the free theory can then be constructed. The matrix elements connect Fock states differing by 0, 1, or 2 quark or gluon quanta, and they include the instantaneous quark and gluon contributions imposed by eliminating dependent degrees of freedom in light-cone gauge. Applications of light-cone methods to QCD phenomenology are briefly described.

  20. Cone and Rod Loss in Stargardt Disease Revealed by Adaptive Optics Scanning Light Ophthalmoscopy

    PubMed Central

    Song, Hongxin; Rossi, Ethan A.; Latchney, Lisa; Bessette, Angela; Stone, Edwin; Hunter, Jennifer J.; Williams, David R.; Chung, Mina

    2015-01-01

    Importance Stargardt disease (STGD1) is characterized by macular atrophy and flecks in the retinal pigment epithelium. The causative ABCA4 gene encodes a protein localizing to photoreceptor outer segments. The pathologic steps by which ABCA4 mutations lead to clinically detectable retinal pigment epithelium changes remain unclear. We investigated early STGD1 using adaptive optics scanning light ophthalmoscopy. Observations Adaptive optics scanning light ophthalmoscopy imaging of 2 brothers with early STGD1 and their unaffected parents was compared with conventional imaging. Cone and rod spacing were increased in both patients (P <.001) with a dark cone appearance. No foveal cones were detected in the older brother. In the younger brother, foveal cones were enlarged with low density (peak cone density, 48.3 × 103 cones/mm2). The ratio of cone to rod spacing was increased in both patients, with greater divergence from normal approaching the foveal center, indicating that cone loss predominates centrally and rod loss increases peripherally. Both parents had normal photoreceptor mosaics. Genetic testing revealed 3 disease-causing mutations. Conclusions and Relevance This study provides in vivo images of rods and cones in STGD1. Although the primary clinical features of STGD1 are retinal pigment epithelial lesions, adaptive optics scanning light ophthalmoscopy reveals increased cone and rod spacing in areas that appear normal in conventional images, suggesting that photoreceptor loss precedes clinically detectable retinal pigment epithelial disease in STGD1. PMID:26247787

  1. Stray light in cone beam optical computed tomography: II. Reduction using a convergent light source.

    PubMed

    Dekker, Kurtis H; Battista, Jerry J; Jordan, Kevin J

    2016-04-07

    Optical cone beam computed tomography (CBCT) using a broad beam and CCD camera is a fast method for densitometry of 3D optical gel dosimeters. However, diffuse light sources introduce considerable stray light into the imaging system, leading to underestimation of attenuation coefficients and non-uniformities in CT images unless corrections are applied to each projection image. In this study, the light source of a commercial optical CT scanner is replaced with a convergent cone beam source consisting of almost exclusively image forming primary rays. The convergent source is achieved using a small isotropic source and a Fresnel lens. To characterize stray light effects, full-field cone beam CT imaging is compared to fan beam CT (FBCT) using a 1 cm high fan beam aperture centered on the optic axis of the system. Attenuating liquids are scanned within a large 96 mm diameter uniform phantom and in a small 13.5 mm diameter finger phantom. For the uniform phantom, cone and fan beam CT attenuation coefficients agree within a maximum deviation of (1  ±  2)% between mean values over a wide range from 0.036 to 0.43 cm(-1). For the finger phantom, agreement is found with a maximum deviation of (4  ±  2)% between mean values over a range of 0.1-0.47 cm(-1). With the convergent source, artifacts associated with refractive index mismatch and vessel optical features are more pronounced. Further optimization of the source size to achieve a balance between quantitative accuracy and artifact reduction should enable practical, accurate 3D dosimetry, avoiding time consuming 3D scatter measurements.

  2. Stray light in cone beam optical computed tomography: II. Reduction using a convergent light source

    NASA Astrophysics Data System (ADS)

    Dekker, Kurtis H.; Battista, Jerry J.; Jordan, Kevin J.

    2016-04-01

    Optical cone beam computed tomography (CBCT) using a broad beam and CCD camera is a fast method for densitometry of 3D optical gel dosimeters. However, diffuse light sources introduce considerable stray light into the imaging system, leading to underestimation of attenuation coefficients and non-uniformities in CT images unless corrections are applied to each projection image. In this study, the light source of a commercial optical CT scanner is replaced with a convergent cone beam source consisting of almost exclusively image forming primary rays. The convergent source is achieved using a small isotropic source and a Fresnel lens. To characterize stray light effects, full-field cone beam CT imaging is compared to fan beam CT (FBCT) using a 1 cm high fan beam aperture centered on the optic axis of the system. Attenuating liquids are scanned within a large 96 mm diameter uniform phantom and in a small 13.5 mm diameter finger phantom. For the uniform phantom, cone and fan beam CT attenuation coefficients agree within a maximum deviation of (1  ±  2)% between mean values over a wide range from 0.036 to 0.43 cm-1. For the finger phantom, agreement is found with a maximum deviation of (4  ±  2)% between mean values over a range of 0.1-0.47 cm-1. With the convergent source, artifacts associated with refractive index mismatch and vessel optical features are more pronounced. Further optimization of the source size to achieve a balance between quantitative accuracy and artifact reduction should enable practical, accurate 3D dosimetry, avoiding time consuming 3D scatter measurements.

  3. Modeling the role of mid-wavelength cones in circadian responses to light

    PubMed Central

    Dkhissi-Benyahya, Ouria; Gronfier, Claude; De Vanssay, Wena; Flamant, Frédéric; Cooper, Howard M.

    2007-01-01

    Summary Non-visual responses to light, such as photic entrainment of the circadian clock, involve intrinsically light sensitive melanopsin-expressing ganglion cells as well as rod and cone photoreceptors. However, previous studies have been unable to demonstrate a specific contribution of cones in the photic control of circadian responses to light. Using a mouse model that specifically lacks mid-wavelength (MW) cones we show that these photoreceptors play a significant role in light entrainment and in phase shifting of the circadian oscillator. The contribution of MW cones is mainly observed for light exposures of short duration and towards the longer wavelength region of the spectrum, consistent with the known properties of this opsin. Modelling the contributions of the various photoreceptors stresses the importance of considering the particular spectral, temporal and irradiance response domains of the photopigments when assessing their role and contribution in circadian responses to light. PMID:17329208

  4. Revisiting the equivalence of light-front and covariant QED in the light-cone gauge

    NASA Astrophysics Data System (ADS)

    Mantovani, Luca; Pasquini, Barbara; Xiong, Xiaonu; Bacchetta, Alessandro

    2016-12-01

    We discuss the equivalence between light-front time-ordered-perturbation theory and covariant quantum field theory in light-front quantization, in the case of quantum electrodynamics at one-loop level. In particular, we review the one-loop calculation of the vertex correction, fermion self-energy and vacuum polarization. We apply the procedure of integration by residue over the light-front energy in the loop to show how the perturbative expansion in covariant terms can be reduced to a sum of propagating and instantaneous diagrams of light-front time-ordered perturbation theory. The detailed proof of equivalence between the two formulations of the theory resolves the controversial question on which form should be used for the gauge-field propagator in the light-cone gauge in the covariant approach.

  5. Higher twist parton distributions from light-cone wave functions

    SciTech Connect

    Braun, V. M.; Lautenschlager, T.; Pirnay, B.; Manashov, A. N.

    2011-05-01

    We explore the possibility to construct higher-twist parton distributions in a nucleon at some low reference scale from convolution integrals of the light-cone wave functions (WFs). To this end we introduce simple models for the four-particle nucleon WFs involving three valence quarks and a gluon with total orbital momentum zero, and estimate their normalization (WF at the origin) using QCD sum rules. We demonstrate that these WFs provide one with a reasonable description of both polarized and unpolarized parton densities at large values of the Bjorken variable x{>=}0.5. Twist-three parton distributions are then constructed as convolution integrals of qqqg and the usual three-quark WFs. The cases of the polarized structure function g{sub 2}(x,Q{sup 2}) and single transverse spin asymmetries are considered in detail. We find that the so-called gluon pole contribution to twist-three distributions relevant for single spin asymmetry vanishes in this model, but is generated perturbatively at higher scales by the evolution, in the spirit of Glueck-Reya-Vogt parton distributions.

  6. The B3 Subunit of the Cone Cyclic Nucleotide-gated Channel Regulates the Light Responses of Cones and Contributes to the Channel Structural Flexibility*

    PubMed Central

    Ding, Xi-Qin; Thapa, Arjun; Ma, Hongwei; Xu, Jianhua; Elliott, Michael H.; Rodgers, Karla K.; Smith, Marci L.; Wang, Jin-Shan; Pittler, Steven J.; Kefalov, Vladimir J.

    2016-01-01

    Cone photoreceptor cyclic nucleotide-gated (CNG) channels play a pivotal role in cone phototransduction, which is a process essential for daylight vision, color vision, and visual acuity. Mutations in the cone channel subunits CNGA3 and CNGB3 are associated with human cone diseases, including achromatopsia, cone dystrophies, and early onset macular degeneration. Mutations in CNGB3 alone account for 50% of reported cases of achromatopsia. This work investigated the role of CNGB3 in cone light response and cone channel structural stability. As cones comprise only 2–3% of the total photoreceptor population in the wild-type mouse retina, we used Cngb3−/−/Nrl−/− mice with CNGB3 deficiency on a cone-dominant background in our study. We found that, in the absence of CNGB3, CNGA3 was able to travel to the outer segments, co-localize with cone opsin, and form tetrameric complexes. Electroretinogram analyses revealed reduced cone light response amplitude/sensitivity and slower response recovery in Cngb3−/−/Nrl−/− mice compared with Nrl−/− mice. Absence of CNGB3 expression altered the adaptation capacity of cones and severely compromised function in bright light. Biochemical analysis demonstrated that CNGA3 channels lacking CNGB3 were more resilient to proteolysis than CNGA3/CNGB3 channels, suggesting a hindered structural flexibility. Thus, CNGB3 regulates cone light response kinetics and the channel structural flexibility. This work advances our understanding of the biochemical and functional role of CNGB3 in cone photoreceptors. PMID:26893377

  7. Off-shell spinor-helicity amplitudes from light-cone deformation procedure

    NASA Astrophysics Data System (ADS)

    Ponomarev, Dmitry

    2016-12-01

    We study the consistency conditions for interactions of massless fields of any spin in four-dimensional flat space using the light-cone approach. We show that they can be equivalently rewritten as the Ward identities for the off-shell light-cone amplitudes built from the light-cone Hamiltonian in the standard way. Then we find a general solution of these Ward identities. The solution admits a compact representation when written in the spinor-helicity form and is given by an arbitrary function of spinor products, satisfying wellknown homogeneity constraints. Thus, we show that the light-cone consistent deformation procedure inevitably leads to a certain off-shell version of the spinor-helicity approach. We discuss how the relation between the two approaches can be employed to facilitate the search of consistent interaction of massless higher-spin fields.

  8. E{sub 7(7)} on the Light-Cone

    SciTech Connect

    Kim, Sung-Soo

    2008-11-23

    We study the E{sub 7(7)} on-shell duality symmetry of N = 8 supergravity in four dimensions and show that all physical fields transform under E{sub 7(7)} on the light-cone. We then use this symmetry to construct order {kappa}{sup 2} interactions in light-cone superspace, by requiring this E{sub 7(7)} transformations commutes with the supersymmetry transformations.

  9. The sine-Gordon model and the small. kappa. sup + region of light- cone perturbation theory

    SciTech Connect

    Griffin, P.A.

    1992-01-01

    The non-perturbative ultraviolet divergence of the sine-Gordon model is used to study the k{sup +} = 0 region of light-cone perturbation theory. The light-cone vacuum is shown to be unstable at the non- perturbative {beta}{sup 2} = 8{pi} critical point by a light-cone version of Coleman's variational method. Vacuum bubbles, which are k{sup +} = 0 diagram in light-cone field theory and are individually finite and non-vanishing for all {beta}, conspire to generate ultraviolet divergences of the light-cone energy density. The k{sup +} = 0 region of momentum also contributed to connected Green's functions: the connected two point function will not diverge, as it should, at the critical point unless diagrams which contribute only at k {sup +} = 0 are properly included. This analysis shows in a simple way how the k {sup +} = 0 region cannot be ignored even for connected diagrams. This phenomenon is expected to occur in higher dimensional gauge theories starting at two loop order in light-cone perturbation theory.

  10. Retinal cone and rod photoreceptor cells exhibit differential susceptibility to light-induced damage.

    PubMed

    Okano, Kiichiro; Maeda, Akiko; Chen, Yu; Chauhan, Vishal; Tang, Johnny; Palczewska, Grazyna; Sakai, Tsutomu; Tsuneoka, Hiroshi; Palczewski, Krzysztof; Maeda, Tadao

    2012-04-01

    All-trans-retinal and its condensation-products can cause retinal degeneration in a light-dependent manner and contribute to the pathogenesis of human macular diseases such as Stargardt's disease and age-related macular degeneration. Although these toxic retinoid by-products originate from rod and cone photoreceptor cells, the contribution of each cell type to light-induced retinal degeneration is unknown. In this study, the primary objective was to learn whether rods or cones are more susceptible to light-induced, all-trans-retinal-mediated damage. Previously, we reported that mice lacking enzymes that clear all-trans-retinal from the retina, ATP-binding cassette transporter 4 and retinol dehydrogenase 8, manifested light-induced retinal dystrophy. We first examined early-stage age-related macular degeneration patients and found retinal degenerative changes in rod-rich rather than cone-rich regions of the macula. We then evaluated transgenic mice with rod-only and cone-like-only retinas in addition to progenies of such mice inbred with Rdh8(-/-) Abca4(-/-) mice. Of all these strains, Rdh8(-/-) Abca4(-/-) mice with a mixed rod-cone population showed the most severe retinal degeneration under regular cyclic light conditions. Intense light exposure induced acute retinal damage in Rdh8(-/-) Abca4(-/-) and rod-only mice but not cone-like-only mice. These findings suggest that progression of retinal degeneration in Rdh8(-/-) Abca4(-/-) mice is affected by differential vulnerability of rods and cones to light. © 2012 The Authors. Journal of Neurochemistry © 2012 International Society for Neurochemistry.

  11. Reionization on large scales. IV. Predictions for the 21 cm signal incorporating the light cone effect

    SciTech Connect

    La Plante, P.; Battaglia, N.; Natarajan, A.; Peterson, J. B.; Trac, H.; Cen, R.; Loeb, A.

    2014-07-01

    We present predictions for the 21 cm brightness temperature power spectrum during the Epoch of Reionization (EoR). We discuss the implications of the 'light cone' effect, which incorporates evolution of the neutral hydrogen fraction and 21 cm brightness temperature along the line of sight. Using a novel method calibrated against radiation-hydrodynamic simulations, we model the neutral hydrogen density field and 21 cm signal in large volumes (L = 2 Gpc h {sup –1}). The inclusion of the light cone effect leads to a relative decrease of about 50% in the 21 cm power spectrum on all scales. We also find that the effect is more prominent at the midpoint of reionization and later. The light cone effect can also introduce an anisotropy along the line of sight. By decomposing the 3D power spectrum into components perpendicular to and along the line of sight, we find that in our fiducial reionization model, there is no significant anisotropy. However, parallel modes can contribute up to 40% more power for shorter reionization scenarios. The scales on which the light cone effect is relevant are comparable to scales where one measures the baryon acoustic oscillation. We argue that due to its large comoving scale and introduction of anisotropy, the light cone effect is important when considering redshift space distortions and future application to the Alcock-Paczyński test for the determination of cosmological parameters.

  12. Optical imaging of human cone photoreceptors directly following the capture of light.

    PubMed

    Bedggood, Phillip; Metha, Andrew

    2013-01-01

    Capture of light in the photoreceptor outer segment initiates a cascade of chemical events that inhibit neurotransmitter release, ultimately resulting in vision. The massed response of the photoreceptor population can be measured non-invasively by electrical recordings, but responses from individual cells cannot be measured without dissecting the retina. Here we used optical imaging to observe individual human cones in the living eye as they underwent bleaching of photopigment and associated phototransduction. The retina was simultaneously stimulated and observed with high intensity visible light at 1 kHz, using adaptive optics. There was marked variability between individual cones in both photosensitivity and pigment optical density, challenging the conventional assumption that photoreceptors act as identical subunits (coefficient of variation in rate of photoisomerization = 23%). There was also a pronounced inverse correlation between these two parameters (p<10(-7)); the temporal evolution of image statistics revealed this to be a dynamic relationship, with cone waveguiding efficiency beginning a dramatic increase within 3 ms of light onset. Beginning as early as 2 ms after light onset and including half of cells by ∼7 ms, cone intensity showed reversals characteristic of interference phenomena, with greater delays in reversal corresponding to cones with more photopigment (p<10(-3)). The timing of these changes is argued to best correspond with either the cessation of dark current, or to related events such as changes in intracellular cGMP. Cone intensity also showed fluctuations of high frequency (332±25 Hz) and low amplitude (3.0±0.85%). Other groups have shown similar fluctuations that were directly evoked by light; if this corresponds to the same phenomenon, we propose that the amplitude of fluctuation may be increased by the use of a bright flash followed by a brief pause, to allow recovery of cone circulating current.

  13. Optical Imaging of Human Cone Photoreceptors Directly Following the Capture of Light

    PubMed Central

    Bedggood, Phillip; Metha, Andrew

    2013-01-01

    Capture of light in the photoreceptor outer segment initiates a cascade of chemical events that inhibit neurotransmitter release, ultimately resulting in vision. The massed response of the photoreceptor population can be measured non-invasively by electrical recordings, but responses from individual cells cannot be measured without dissecting the retina. Here we used optical imaging to observe individual human cones in the living eye as they underwent bleaching of photopigment and associated phototransduction. The retina was simultaneously stimulated and observed with high intensity visible light at 1 kHz, using adaptive optics. There was marked variability between individual cones in both photosensitivity and pigment optical density, challenging the conventional assumption that photoreceptors act as identical subunits (coefficient of variation in rate of photoisomerization = 23%). There was also a pronounced inverse correlation between these two parameters (p<10−7); the temporal evolution of image statistics revealed this to be a dynamic relationship, with cone waveguiding efficiency beginning a dramatic increase within 3 ms of light onset. Beginning as early as 2 ms after light onset and including half of cells by ∼7 ms, cone intensity showed reversals characteristic of interference phenomena, with greater delays in reversal corresponding to cones with more photopigment (p<10−3). The timing of these changes is argued to best correspond with either the cessation of dark current, or to related events such as changes in intracellular cGMP. Cone intensity also showed fluctuations of high frequency (332±25 Hz) and low amplitude (3.0±0.85%). Other groups have shown similar fluctuations that were directly evoked by light; if this corresponds to the same phenomenon, we propose that the amplitude of fluctuation may be increased by the use of a bright flash followed by a brief pause, to allow recovery of cone circulating current. PMID:24260177

  14. Anomalous Light Cones and Valley Optical Selection Rules of Interlayer Excitons in Twisted Heterobilayers

    NASA Astrophysics Data System (ADS)

    Yu, Hongyi; Wang, Yong; Tong, Qingjun; Xu, Xiaodong; Yao, Wang

    2015-10-01

    We show that, because of the inevitable twist and lattice mismatch in heterobilayers of transition metal dichalcogenides, interlayer excitons have sixfold degenerate light cones anomalously located at finite velocities on the parabolic energy dispersion. The photon emissions at each light cone are elliptically polarized, with the major axis locked to the direction of exciton velocity, and helicity specified by the valley indices of the electron and the hole. These finite-velocity light cones allow unprecedented possibilities for optically injecting valley polarization and valley current, and the observation of both direct and inverse valley Hall effects, by exciting interlayer excitons. Our findings suggest potential excitonic circuits with valley functionalities, and unique opportunities to study exciton dynamics and condensation phenomena in semiconducting 2D heterostructures.

  15. Discretized light-cone quantization: e sup + e minus (. gamma. ) model for positronium

    SciTech Connect

    Kaluza, M. Center for Applied Mathematics and Theoretical Physics, University of Maribor, Krekova 2, YU-62000 Maribor, Slovenia ); Pauli, H.C. )

    1992-04-15

    The method of discretized light-cone quantization is applied to gauge theory in 3+1 dimensions and tested by calculating the spectrum and the wave functions for positronium. Working in a Fock-space expansion, only the electron-positron and the electron-positron-photon states are included. The light-cone Hamiltonian matrix is constructed blockwise, and diagonalized using the Bauer-Rutishauser simultaneous iteration algorithm for sparse matrices. At the current level of accuracy of about 10%, the model reproduces the binding energy and the charge radius of the positronium ground state for the coupling constant of {alpha}=0.3. The distribution functions for fermions and photons are presented for the ground state. In addition the light-cone Schroedinger equation has been solved.

  16. Light trapping above the light cone in a one-dimensional array of dielectric spheres

    NASA Astrophysics Data System (ADS)

    Bulgakov, Evgeny N.; Sadreev, Almas F.

    2015-08-01

    We demonstrate bound states in the first TE and TM diffraction continua (BSC) in a linear periodic array of dielectric spheres in air above the light cone. We classify the BSCs according to the symmetry specified by the azimuthal number m , the Bloch wave vector β directed along the array, and polarization. The most simple symmetry-protected TE and TM polarized BSCs have m =0 and β =0 and occur in a wide range of the radii of the spheres and dielectric constants. More complicated BSCs with m ≠0 and β =0 exist only for a selected radius of the spheres at a fixed dielectric constant. We also find robust Bloch BSCs with β ≠0 and m =0 . We present also the BSCs embedded into two and three diffraction continua. We show that the BSCs can be easily detected by the collapse of the Fano resonance for scattering of electromagnetic plane waves by the array.

  17. Learned arbitrary responses to light in mice without rods or cones

    NASA Astrophysics Data System (ADS)

    Mrosovsky, N.; Salmon, Peggy

    2002-10-01

    The aim of this investigation was to discover whether mice lacking classical photoreceptors (rods and cones) can nevertheless be trained to respond to light. Mice with the coneless (cl) transgene have an attenuated diphtheria toxin fused to a cone opsin promotor. Mutant mice homozygous for the retinal degeneration (rd) gene undergo loss of their rods. By mating these two strains, mice lacking both cones and rods can be generated (Lucas et al. 1999). Such coneless-rodless mice were able to use light as a signal to make a behavioural response to avoid impending shock. Nevertheless, especially initially, they used the light as a cue less often than wildtype controls, indicating that normally the rods and cones are used for such responses. However, other photoreceptors are able to take over this role to some extent. When the lights were covered with opaque material, the performance of rodless-coneless mice dropped to chance level, indicating that they had been using the light as a cue for avoidance.

  18. Light extraction enhancement of bulk GaN light-emitting diode with hemisphere-cones-hybrid surface.

    PubMed

    Sun, Bo; Zhao, Lixia; Wei, Tongbo; Yi, Xiaoyan; Liu, Zhiqiang; Wang, Guohong; Li, Jinmin; Yi, Futing

    2012-08-13

    InGaN flip-chip light-emitting diodes on bulk GaN substrate (FS-FCLEDs) with hemisphere-cones-hybrid surface were fabricated using both dry etching with CsCl nanoislands as mask and chemical wet etching. Compared with the corresponding flat LEDs, the light output power of FS-FCLEDs with combined nanostructures shows an enhancement factor of 1.9 at 350mA injection current. Finite-difference time-domain (FDTD) simulation results show that such enhancement of the output power is mainly attributed to the reduction of the total internal reflection and increase of the light scattering probability in the hemisphere-cones-hybrid surface, which is due to a combination effect of light diffraction at the nanocones edges, and light interference within the hemisphere and nanocones.

  19. Visual Arrestin 1 Contributes to Cone Photoreceptor Survival and Light Adaptation

    PubMed Central

    Brown, Bruce M.; Ramirez, Teresa; Rife, Lawrence

    2010-01-01

    Purpose. To evaluate morphologic and functional contributions of Arrestin 1 (Arr1) and Arrestin 4 (Arr4) in cone photoreceptors, the authors examined the phenotypes of visual arrestin knockout mice (Arr1−/−, Arr4−/−, Arr1−/−Arr4−/− [Arr-DKO]) reared in darkness. Methods. Retinal rods and cones were evaluated in wild-type (WT), Arr1−/−, Arr4−/−, and Arr-DKO mice using quantitative morphologic analysis, immunoblot, immunohistochemistry, TUNEL, and electroretinographic (ERG) techniques. Results. Compared with either Arr4−/− or WT, Arr1−/− and Arr-DKO mice had increased apoptotic nuclei in their retinal outer nuclear layer (ONL) at postnatal day (P) 22. By P60, cone density was significantly diminished, but the ONL appeared normal. After 1 minute of background illumination, cone ERG b-wave amplitudes were similar in WT and all Arr KO mice. However, by 3 minutes and continuing through 15 minutes of light adaptation, the cone b-wave amplitudes of WT and Arr4−/− mice increased significantly over those of the Arr1−/− and Arr-DKO mice, which demonstrated no cone b-wave amplitude increase. In contrast, ERG flicker analysis after the 15-minute light adaptation period demonstrated no loss in amplitude for either Arr1−/− or Arr4−/− mice, whereas Arr-DKO had significantly lower amplitudes. When Arr1 expression was restored in Arr1−/− mice (+p48Arr1−/−), normal cone density and light-adapted ERG b-wave amplitudes were observed. Conclusions. In the adult dark-reared Arr1−/− and Arr-DKO mice, viable cones diminish over time. Arr1 expression is essential for cone photoreceptor survival and light adaptation, whereas either Arr1 or Arr4 is necessary for maintaining normal flicker responses. PMID:20019357

  20. Speed, sensitivity, and stability of the light response in rod and cone photoreceptors: Facts and models

    PubMed Central

    Korenbrot, Juan I.

    2012-01-01

    The light responses of rod and cone photoreceptors in the vertebrate retina are quantitatively different, yet extremely stable and reproducible because of the extraordinary regulation of the cascade of enzymatic reactions that link photon absorption and visual pigment excitation to the gating of cGMP-gated ion channels in the outer segment plasma membrane. While the molecular scheme of the phototransduction pathway is essentially the same in rods and cones, the enzymes and protein regulators that constitute the pathway are distinct. These enzymes and regulators can differ in the quantitative features of their functions or in concentration if their functions are similar or both can be true. The molecular identity and distinct function of the molecules of the transduction cascade in rods and cones are summarized. The functional significance of these molecular differences is examined with a mathematical model of the signal-transducing enzymatic cascade. Constrained by available electrophysiological, biochemical and biophysical data, the model simulates photocurrents that match well the electrical photoresponses measured in both rods and cones. Using simulation computed with the mathematical model, the time course of light-dependent changes in enzymatic activities and second messenger concentrations in non-mammalian rods and cones are compared side by side. PMID:22658984

  1. Spin and orbital angular momenta of light reflected from a cone

    NASA Astrophysics Data System (ADS)

    Mansuripur, Masud; Zakharian, Armis R.; Wright, Ewan M.

    2011-09-01

    We examine several retro-reflecting optical elements, each involving two reflections. In the case of a hollow metallic cone having an apex angle of 90°, a circularly polarized incident beam acquires, upon reflection, the opposite spin angular momentum. However, no angular momentum is transferred to the cone, because the reflected beam picks up an orbital angular momentum that is twice as large but opposite in direction to that of its spin. A 90° cone made of a transparent material in which the incident light suffers two total internal reflections before returning may be designed to endow the retro-reflected beam with different mixtures of orbital and spin angular momenta. Under no circumstances, however, is it possible to transfer angular momentum from the light beam to the cone without either allowing absorption or breaking the axial symmetry of the cone. A simple example of broken symmetry is provided by a wedge-shaped metallic reflector having an apex angle of 90°, which picks up angular momentum upon reflecting a circularly polarized incident beam.

  2. Spin and orbital angular momenta of light reflected from a cone

    SciTech Connect

    Mansuripur, Masud; Wright, Ewan M.; Zakharian, Armis R.

    2011-09-15

    We examine several retro-reflecting optical elements, each involving two reflections. In the case of a hollow metallic cone having an apex angle of 90 deg., a circularly polarized incident beam acquires, upon reflection, the opposite spin angular momentum. However, no angular momentum is transferred to the cone, because the reflected beam picks up an orbital angular momentum that is twice as large but opposite in direction to that of its spin. A 90 deg. cone made of a transparent material in which the incident light suffers two total internal reflections before returning may be designed to endow the retro-reflected beam with different mixtures of orbital and spin angular momenta. Under no circumstances, however, is it possible to transfer angular momentum from the light beam to the cone without either allowing absorption or breaking the axial symmetry of the cone. A simple example of broken symmetry is provided by a wedge-shaped metallic reflector having an apex angle of 90 deg., which picks up angular momentum upon reflecting a circularly polarized incident beam.

  3. {kappa}K*{sup 0}{gamma}-vertex in light cone QCD sum rules

    SciTech Connect

    Gokalp, A.; Yilmaz, O.; Sarac, Y.

    2008-06-01

    We investigate the {kappa}K*{sup 0}{gamma}-vertex in the framework of light cone QCD sum rules. We estimate the coupling constant g{sub {kappa}}{sub K*{sup 0}}{sub {gamma}}, and compare our result with that used in the nonlinear chiral Lagrangian approach using the vector-meson dominance model in the SU(3) limit.

  4. Octet negative parity to octet positive parity electromagnetic transitions in light cone QCD

    NASA Astrophysics Data System (ADS)

    Aliev, T. M.; Savcı, M.

    2014-07-01

    Light cone QCD sum rules for the electromagnetic transition form factors among positive and negative parity octet baryons are derived. The unwanted contributions of the diagonal transitions among positive parity octet baryons are eliminated by combining the sum rules derived from different Lorentz structures. The Q2 dependence for the transversal and longitudinal helicity amplitudes are studied.

  5. Classical Yang-Mills Mechanics: Instant vs. Light-cone Form

    SciTech Connect

    Mladenov, D.

    2010-11-25

    Two different forms of relativistic dynamics, the instant and the light-cone form, for the pure SU(2) Yang-Mills field theory in 4-dimensional Minkowski space are examined under the supposition that the gauge fields depend on the time evolution parameter only. The obtained under that restriction of gauge potential space homogeneity mechanical matrix model, sometimes called Yang-Mills classical mechanics, is systematically studied in its instant and light-cone form of dynamics using the Dirac's generalized Hamiltonian approach. In the both cases the constraint content of the obtained mechanical systems is found. In contrast to its well-known instant-time counterpart the light-cone version of SU(2) Yang-Mills classical mechanics has in addition to the constraints generating the SU(2) gauge transformations the new first and second class constraints also. On account of all of these constraints a complete reduction in number of the degrees of freedom is performed. In the instant form of dynamics it is shown that after elimination of the gauge degrees of freedom from the classical SU(2) Yang-Mills mechanics the resulting unconstrained system represents the ID{sub 3} Euler-Calogero-Moser model with a certain external fourth-order potential, whereas in the light-cone form it is argued that the classical evolution of the unconstrained degrees of freedom is equivalent to a free one-dimensional particle dynamics.

  6. The Indispensability of Ghost Fields in the Light-Cone Gauge Quantization of Gauge Fields

    NASA Astrophysics Data System (ADS)

    Nakawaki, Y.; McCartor, G.

    1999-07-01

    We continue McCartor and Robertson's recent demonstration of the indispensability of ghost fields in the light-cone gauge quantization of gauge fields. It is shown that the ghost fields are indispensable in deriving well-defined antiderivatives and in regularizing the most singular component of the gauge field propagator. To this end it is sufficient to confine ourselves to noninteracting abelian fields. Furthermore, to circumvent dealing with constrained systems, we construct the temporal gauge canonical formulation of the free electromagnetic field in auxiliary coordinates xμ=(x-, x+, x1, x2), where x- = x0 cos {θ}-x3 sin θ x+ = x0 sin θ +x3 cos θ and x- plays the role of time. In so doing we can quantize the fields canonically without any constraints, unambiguously introduce ``static ghost fields" as residual gauge degrees of freedom and construct the light-cone gauge solution in the light-cone representation by simply taking the light-cone limit (θ --> (π / 4) ). As a by product we find that, with a suitable choice of vacuum, the Mandelstam-Leibbrandt form of the propagator can be derived in the θ=0 case (the temporal gauge formulation in the equal-time representation).

  7. Light-cone gauge superstring field theory in a linear dilaton background

    NASA Astrophysics Data System (ADS)

    Ishibashi, Nobuyuki

    2017-03-01

    The Feynman amplitudes of light-cone gauge superstring field theory suffer from various divergences. In order to regularize them, we study the theory in a linear dilaton background Φ =-i Q X1 with the number of spacetime dimensions fixed. We show that the theory with the Feynman i ɛ  (ɛ >0 ) and Q2>10 yields finite results.

  8. Impact of light therapy on rod and cone functions in healthy subjects.

    PubMed

    Gagné, Anne-Marie; Gagné, Philippe; Hébert, Marc

    2007-06-30

    Light therapy is an effective treatment for patients with seasonal affective disorders and is commonly used at an intensity of 10,000 lx. The aim of this study was to investigate the direct impact of light therapy on cones and rods photoreceptors using the electroretinogram (ERG) technique. Twelve healthy subjects were exposed for 60 min to three light conditions: 10,000 lx, 100 lx and 5 lx. ERG cone and rod luminance response functions were obtained immediately after exposures. Cone function was not affected by any light conditions. Maximal response achieved by the rods was significantly lower following the 100 lx and 10,000 lx conditions when compared with the 5 lx condition. Retinal rod sensitivity was significantly lower in the 10,000 lx condition when compared with the 12 lx condition. A decrease in rod function can readily be observed at 100 lx, that is, at regular indoor lighting. This decrease could be related to the triggering of retinal dopamine production, which would favour day vision over night vision. The further decrease in light sensitivity observed after 60 min at 10,000 lx may be perceived as a protective mechanism of the rod system against bright light.

  9. Light-cone pathology of theories with noncausal propagation

    SciTech Connect

    Singh, L.P.S.; Hagen, C.R.

    1983-02-15

    Couplings of fields with spin values 0, 1/2, and 1 are examined in light-front coordinates. It is found that all theories which have noncausal modes of propagation in ordinary spacetime suffer from loss of constraints.

  10. Sivers and Boer-Mulders functions in Light-Cone Quark Models

    SciTech Connect

    Pasquini, Barbara; Yuan, Feng

    2010-01-29

    Results for the naive-time-reversal-odd quark distributions in a light-cone quark model are presented. The final-state interaction effects are generated via single-gluon exchange mechanism. The formalism of light-cone wave functions is used to derive general expressions in terms of overlap of wave-function amplitudes describing the different orbital angular momentum components of the nucleon. In particular, the model predictions show a dominant contribution from S- and P-wave interference in the Sivers function and a significant contribution also from the interference of P and D waves in the Boer-Mulders function. The favourable comparison with existing phenomenological parametrizations motivates further applications to describe azimuthal asymmetries in hadronic reactions.

  11. Multiloop amplitudes of light-cone gauge NSR string field theory in noncritical dimensions

    NASA Astrophysics Data System (ADS)

    Ishibashi, Nobuyuki; Murakami, Koichi

    2017-01-01

    Feynman amplitudes of light-cone gauge superstring field theory are ill-defined because of various divergences. In a previous paper, one of the authors showed that taking the worldsheet theory to be the one in a linear dilaton background Φ = - iQX 1 with Feynman iɛ ( ɛ > 0) and Q 2 > 10 yields finite amplitudes. In this paper, we apply this worldsheet theory to dimensional regularization of the light-cone gauge NSR superstring field theory. We concentrate on the amplitudes for even spin structure with external lines in the (NS,NS) sector. We show that the multiloop amplitudes are indeed regularized in our scheme and that they coincide with the results in the first-quantized formalism through the analytic continuation Q → 0.

  12. The CST: Its Achievements and Its Connection to the Light Cone

    NASA Astrophysics Data System (ADS)

    Gross, Franz

    2017-03-01

    I review the applications of the Covariant Spectator Theory (CST) since its inception in 1969. Applications discussed here include calculations of NN scattering, 3N bound states, electromagnetic form factors of few-nucleon systems, and the recent successes in describing the dynamical generation of quark mass and the meson spectrum using a chirially invariant quark-antiquark interaction that includes confinement. The common origin of the Light Cone technique and the CST, which dates back to the 1970's, will be discussed.

  13. Free vector propagator in the light-cone gauge and the Mandelstam-Leibbrandt prescription

    SciTech Connect

    Bassetto, A. Istituto Nazionale di Fisica Nucleare, Sezione di Padova, Padova )

    1992-10-15

    We show that the Mandelstam-Leibbrandt causal prescription in the light-cone gauge leads to a free vector propagator which is a tempered distribution, at variance with the Cauchy principal-value prescription and other ones related to it by residual gauge transformations, which unavoidably entail infrared singularities already at the free level of the theory. In this respect the causal prescription seems to enjoy a privileged status.

  14. 21 cm signal from cosmic dawn - II. Imprints of the light-cone effects

    NASA Astrophysics Data System (ADS)

    Ghara, Raghunath; Datta, Kanan K.; Choudhury, T. Roy

    2015-11-01

    Details of various unknown physical processes during the cosmic dawn and the epoch of reionization can be extracted from observations of the redshifted 21 cm signal. These observations, however, will be affected by the evolution of the signal along the line of sight which is known as the `light-cone effect'. We model this effect by post-processing a dark matter N-body simulation with an 1D radiative transfer code. We find that the effect is much stronger and dramatic in presence of inhomogeneous heating and Ly α coupling compared to the case where these processes are not accounted for. One finds increase (decrease) in the spherically averaged power spectrum up to a factor of 3 (0.6) at large scales (k ˜ 0.05 Mpc- 1) when the light-cone effect is included, though these numbers are highly dependent on the source model. The effect is particularly significant near the peak and dip-like features seen in the power spectrum. The peaks and dips are suppressed and thus the power spectrum can be smoothed out to a large extent if the width of the frequency band used in the experiment is large. We argue that it is important to account for the light-cone effect for any 21-cm signal prediction during cosmic dawn.

  15. The application of light-cone quantization to quantum chromodynamics in one-plus-one dimensions

    SciTech Connect

    Hornbostel, K.J.

    1988-12-01

    Formal and computational aspects of light cone quantization are studied by application to quantum chromodynamics (QCD) in one spatial plus one temporal dimension. This quantization scheme, which has been extensively applied to perturbative calculations, is shown to provide an intuitively appealing and numerically tractable approach to non-perturbative computations as well. In the initial section, a light-cone quantization procedure is developed which incorporates fields on the boundaries. This allows for the consistent treatment of massless fermions and the construction of explicitly conserved momentum and charge operators. The next section, which comprises the majority of this work, focuses on the numerical solution of the light-cone Schrodinger equation for bound states. The state space is constructed and the Hamiltonian is evaluated and diagonalized by computer for arbitrary number of colors, baryon number and coupling constant strength. As a result, the full spectrum of mesons and baryons and their associated wavefunctions are determined. These results are compared with those which exist from other approaches to test the reliability of the method. The program also provides a preliminary test for the feasibility of, and an opportunity to develop approximation schemes for, an attack on three-plus-one dimensional QCD. Finally, analytic results are presented which include a discussion of integral equations for wavefunctions and their endpoint behavior. Solutions for hadronic masses and wavefunctions in the limits of both large and small quark mass are discussed. 49 refs., 32 figs., 10 tabs.

  16. Light-cone analysis of ungauged and topologically gauged BLG theories

    NASA Astrophysics Data System (ADS)

    Nilsson, Bengt E. W.

    2009-09-01

    We consider three-dimensional maximally superconformal Bagger-Lambert-Gustavsson (BLG) theory and its topologically gauged version (constructed recently in Gran and Nilsson (2009 J. High Energy Phys. JHEP03(2009)074 (arXiv:0809.4478 [hep-th]))) in the light-cone gauge. After eliminating the entire Chern-Simons gauge field, the ungauged BLG light-cone theory looks more conventional and, apart from the order of the interaction terms, resembles \\mathcal N=4 super-Yang-Mills theory in four dimensions. The light-cone superspace version of the BLG theory is given at the quadratic order together with a suggested form for the quartic terms. Some problems with constructing the sixth-order interaction terms are also discussed. In the topologically gauged case, we analyze the field equations related to the three Chern-Simons-type terms of \\mathcal N=8 conformal supergravity and discuss some of the special features of this theory and its couplings to BLG.

  17. Gluon structure function of a color dipole in the light-cone limit of lattice QCD

    SciTech Connect

    Gruenewald, D.; Ilgenfritz, E.-M.; Pirner, H. J.

    2009-10-01

    We calculate the gluon structure function of a color dipole in near-light-cone SU(2) lattice QCD as a function of x{sub B}. The quark and antiquark are external nondynamical degrees of freedom which act as sources of the gluon string configuration defining the dipole. We compute the color dipole matrix element of transversal chromo-electric and chromo-magnetic field operators separated along a direction close to the light cone, the Fourier transform of which is the gluon structure function. As vacuum state in the pure glue sector, we use a variational ground state of the near-light-cone Hamiltonian. We derive a recursion relation for the gluon structure function on the lattice similar to the perturbative Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation. It depends on the number of transversal links assembling the Schwinger string of the dipole. Fixing the mean momentum fraction of the gluons to the 'experimental value' in a proton, we compare our gluon structure function for a dipole state with four links with the next-to-leading-order MRST 2002 and the CTEQ AB-0 parametrizations at Q{sup 2}=1.5 GeV{sup 2}. Within the systematic uncertainty we find rather good agreement. We also discuss the low x{sub B} behavior of the gluon structure function in our model calculation.

  18. Scattering of glue by glue on the light-cone worldsheet: Helicity nonconserving amplitudes

    SciTech Connect

    Chakrabarti, D.; Qiu, J.; Thorn, C.B.

    2005-09-15

    We give the light-cone gauge calculation of the one-loop on-shell scattering amplitudes for gluon-gluon scattering which violate helicity conservation. We regulate infrared divergences by discretizing the p{sup +} integrations, omitting the terms with p{sup +}=0. Collinear divergences are absent diagram by diagram for the helicity nonconserving amplitudes. We also employ a novel ultraviolet regulator that is natural for the light-cone worldsheet description of planar Feynman diagrams. We show that these regulators give the known answers for the helicity nonconserving one-loop amplitudes, which do not suffer from the usual infrared vagaries of massless particle scattering. For the maximal helicity violating process we elucidate the physics of the remarkable fact that the loop momentum integrand for the on-shell Green function associated with this process, with a suitable momentum routing of the different contributing topologies, is identically zero. We enumerate the counterterms that must be included to give Lorentz covariant results to this order, and we show that they can be described locally in the light-cone worldsheet formulation of the sum of planar diagrams.

  19. Approximate light cone effects in a nonrelativistic quantum field theory after a local quench

    NASA Astrophysics Data System (ADS)

    Bertini, Bruno

    2017-02-01

    We study the spreading of correlations after a local quench in a nonrelativistic quantum field theory. We focus on noninteracting nonrelativistic fermions and study the time evolution after two identical systems in their ground states are suddenly joined together with a localized impurity at the junction. We find that, even if the quasiparticles of the system have unbounded dispersion, the correlations show light cone effects. We carry out a detailed study of these effects by developing an accurate asymptotic expansion of the two-point function and determining exactly the density of particles at any time after the quench. In particular, we find that the width of the light cone region is ∝t1 /2 . The structure of correlations, however, does not show a pure light cone form: "superluminal corrections" are much larger than in the bounded-dispersion case. These findings can be explained by inspecting the structure of excitations generated by the initial state. We show that a similar picture also emerges in the presence of a harmonic trapping potential and when more than two systems are suddenly joined at a single point.

  20. Black hole perturbation theory in a light cone gauge

    NASA Astrophysics Data System (ADS)

    Preston, Brent

    The metric of a Schwarzschild black hole immersed in a uniform magnetic field is studied using black hole perturbation theory in a light crone coordinate system that penetrates the event horizon and possesses a clear geometrical meaning. The magnetic field, which is distorted due to the presence of the black hole, has strength B which is assumed to be small compared to the curvature of the spacetime which allows the perturbed metric to be calculated to order B 2 only. The coordinates allow for an easy identification of the event horizon and the properties of the perturbed black hole are studied. To interpret this perturbed metric, the advanced coordinates are decomposed into irreducible parts which yields the metric of a perturbed black hole in the limit r >> 2 M . Finally we compare our perturbed solution to an exact solution. We show that our perturbed solution is able to match the exact solution but has the freedom to describe a larger class of physically relevant solutions.

  1. Automatic detection of cone photoreceptors in split detector adaptive optics scanning light ophthalmoscope images

    PubMed Central

    Cunefare, David; Cooper, Robert F.; Higgins, Brian; Katz, David F.; Dubra, Alfredo; Carroll, Joseph; Farsiu, Sina

    2016-01-01

    Quantitative analysis of the cone photoreceptor mosaic in the living retina is potentially useful for early diagnosis and prognosis of many ocular diseases. Non-confocal split detector based adaptive optics scanning light ophthalmoscope (AOSLO) imaging reveals the cone photoreceptor inner segment mosaics often not visualized on confocal AOSLO imaging. Despite recent advances in automated cone segmentation algorithms for confocal AOSLO imagery, quantitative analysis of split detector AOSLO images is currently a time-consuming manual process. In this paper, we present the fully automatic adaptive filtering and local detection (AFLD) method for detecting cones in split detector AOSLO images. We validated our algorithm on 80 images from 10 subjects, showing an overall mean Dice’s coefficient of 0.95 (standard deviation 0.03), when comparing our AFLD algorithm to an expert grader. This is comparable to the inter-observer Dice’s coefficient of 0.94 (standard deviation 0.04). To the best of our knowledge, this is the first validated, fully-automated segmentation method which has been applied to split detector AOSLO images. PMID:27231641

  2. Automatic detection of cone photoreceptors in split detector adaptive optics scanning light ophthalmoscope images.

    PubMed

    Cunefare, David; Cooper, Robert F; Higgins, Brian; Katz, David F; Dubra, Alfredo; Carroll, Joseph; Farsiu, Sina

    2016-05-01

    Quantitative analysis of the cone photoreceptor mosaic in the living retina is potentially useful for early diagnosis and prognosis of many ocular diseases. Non-confocal split detector based adaptive optics scanning light ophthalmoscope (AOSLO) imaging reveals the cone photoreceptor inner segment mosaics often not visualized on confocal AOSLO imaging. Despite recent advances in automated cone segmentation algorithms for confocal AOSLO imagery, quantitative analysis of split detector AOSLO images is currently a time-consuming manual process. In this paper, we present the fully automatic adaptive filtering and local detection (AFLD) method for detecting cones in split detector AOSLO images. We validated our algorithm on 80 images from 10 subjects, showing an overall mean Dice's coefficient of 0.95 (standard deviation 0.03), when comparing our AFLD algorithm to an expert grader. This is comparable to the inter-observer Dice's coefficient of 0.94 (standard deviation 0.04). To the best of our knowledge, this is the first validated, fully-automated segmentation method which has been applied to split detector AOSLO images.

  3. B ---> pi and B ---> K transitions from QCD sum rules on the light cone

    SciTech Connect

    Ball, P.

    1998-09-01

    I calculate the form factors describing semileptonic and penguin-induced decays of B mesons into light pseudoscalar mesons. The form factors are calculated from QCD sum rules on the light-cone including contributions up to twist 4, radiative corrections to the leading twist contribution and SU(3)-breaking effects. The theoretical uncertainty is estimated to be \\sim 15%. The heavy-quark-limit relations between semileptonic and penguin form factors are found to be valid in the full accessible range of momentum transfer.

  4. Particle-in-cell simulations of hot electron generation using defocused laser light in cone targets

    SciTech Connect

    Yang, Lei; Pasley, John

    2016-08-15

    The effects of defocusing a high intensity pulse of laser light on the generation of hot electrons in a cone are investigated using particle-in-cell simulations. The results indicate that defocused laser light can soften the electron energy spectrum and increase the coupling efficiency compared to the use of a laser in tight focus. It is shown that this is a consequence of the density profile of plasma produced by the laser prepulse, which is less dense in the case of the defocused laser. The relevance of this result to fast ignition inertial confinement fusion is discussed.

  5. The sine-Gordon model and the small {kappa}{sup +} region of light- cone perturbation theory

    SciTech Connect

    Griffin, P.A.

    1992-09-01

    The non-perturbative ultraviolet divergence of the sine-Gordon model is used to study the k{sup +} = 0 region of light-cone perturbation theory. The light-cone vacuum is shown to be unstable at the non- perturbative {beta}{sup 2} = 8{pi} critical point by a light-cone version of Coleman`s variational method. Vacuum bubbles, which are k{sup +} = 0 diagram in light-cone field theory and are individually finite and non-vanishing for all {beta}, conspire to generate ultraviolet divergences of the light-cone energy density. The k{sup +} = 0 region of momentum also contributed to connected Green`s functions: the connected two point function will not diverge, as it should, at the critical point unless diagrams which contribute only at k {sup +} = 0 are properly included. This analysis shows in a simple way how the k {sup +} = 0 region cannot be ignored even for connected diagrams. This phenomenon is expected to occur in higher dimensional gauge theories starting at two loop order in light-cone perturbation theory.

  6. Early light deprivation effects on human cone-driven retinal function.

    PubMed

    Esposito Veneruso, Paolo; Ziccardi, Lucia; Magli, Giulia; Parisi, Vincenzo; Falsini, Benedetto; Magli, Adriano

    2017-03-01

    To assess whether the early light deprivation induced by congenital cataract may influence the cone-driven retinal function in humans. Forty-one patients affected by congenital cataract (CC) who had undergone uncomplicated cataract extraction surgery and intraocular lens implant, and 14 healthy subjects (HS) were enrolled. All patients underwent complete ophthalmological and orthoptic evaluations and best-corrected visual acuity (BCVA) measurement; light-adapted full-field electroretinograms (ERG) and photopic negative responses (PhNR) were recorded to obtain a reliable measurement of the outer/inner retinal function and of the retinal ganglion cells' function respectively. Mean values of light-adapted ERG a- and b-wave and PhNR amplitude of CC eyes were significantly reduced and photopic ERG b-wave implicit time mean values were significantly delayed when compared to HS ones. When studying photopic ERG mean amplitudes at 5 ms, significant differences were found when comparing CC and control eyes. In CC eyes, statistically significant correlations were found between a- and b- wave amplitudes and PhNR amplitudes. No significant correlations were found between ERG parameters and BCVA, as well as between the age of CC patients at surgery and the time elapsed from lens extraction. No significant differences were found when functional parameters of bilateral and unilateral congenital cataract (uCC) eyes were compared, however uCC eyes showed significant differences when compared with contralateral healthy eyes. We found a significant impairment of cone-driven retinal responses in patients with a history of congenital cataract. These changes might result from the long-lasting effects of early light deprivation on the cone retinal pathways. Our findings support the relevance of retinal involvement in deficits induced by early light deprivation. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  7. Possible Roles of Glutamate Transporter EAAT5 in Mouse Cone Depolarizing Bipolar Cell Light Responses

    PubMed Central

    Tse, Dennis Y.; Chung, Inyoung; Wu, Samuel M.

    2015-01-01

    A remarkable feature of neuronal glutamate transporters (EAATs) is their dual functions of classical carriers and ligand-gated chloride (CI−) channels. CI− conductance is rapidly activated by glutamate in subtype EAAT5, which mediates light responses in depolarizing bipolar cells (DBC) in retinae of lower vertebrates. In this study, we examine whether EAAT5 also mediates the DBC light response in mouse. We took advantage of an infrared illuminated micro-injection system, and studied the effects of the EAAT blocker (TBOA) and a glutamate receptor agonist (LAP4) on the mouse electroretinogram (ERG) b-wave responses. Our results showed that TBOA and LAP4 shared similar temporal patterns of inhibition: both inhibited the ERG b-wave shortly after injection and recovered with similar time courses. TBOA inhibited the b-wave completely at mesopic light intensity with an IC50 value about 1 log unit higher than that of LAP4. The inhibitory effects of TBOA and LAP4 were found to be additive in the photopic range. Furthermore, TBOA alone inhibited the b-wave in the cone operative range in knockout mice lacking DBCRs at a low concentration that did not alter synaptic glutamate clearance activity. It also produced a stronger inhibition than that of LAP4 on the cone-driven b-wave measured with a double flash method in wildtype mice. These electrophysiological data suggest a significant role for EAAT5 in mediating cone-driven DBC light responses. Our immunohistochemistry data indicated the presence of postsynaptic EAAT5 on some DBCCs and some DBCRs, providing an anatomical basis for EAAT5’s role in DBC light responses. PMID:24972005

  8. Phosphorylation-independent Suppression of Light-activated Visual Pigment by Arrestin in Carp Rods and Cones*

    PubMed Central

    Tomizuka, Junko; Tachibanaki, Shuji; Kawamura, Satoru

    2015-01-01

    Visual pigment in photoreceptors is activated by light. Activated visual pigment (R*) is believed to be inactivated by phosphorylation of R* with subsequent binding of arrestin. There are two types of photoreceptors, rods and cones, in the vertebrate retina, and they express different subtypes of arrestin, rod and cone type. To understand the difference in the function between rod- and cone-type arrestin, we first identified the subtype of arrestins expressed in rods and cones in carp retina. We found that two rod-type arrestins, rArr1 and rArr2, are co-expressed in a rod and that a cone-type arrestin, cArr1, is expressed in blue- and UV-sensitive cones; the other cone-type arrestin, cArr2, is expressed in red- and green-sensitive cones. We quantified each arrestin subtype and estimated its concentration in the outer segment of a rod or a cone in the dark; they were ∼0.25 mm (rArr1 plus rArr2) in a rod and 0.6–0.8 mm (cArr1 or cArr2) in a cone. The effect of each arrestin was examined. In contrast to previous studies, both rod and cone arrestins suppressed the activation of transducin in the absence of visual pigment phosphorylation, and all of the arrestins examined (rArr1, rArr2, and cArr2) bound transiently to most probably nonphosphorylated R*. One rod arrestin, rArr2, bound firmly to phosphorylated pigment, and the other two, rArr1 and cArr2, once bound to phosphorylated R* but dissociated from it during incubation. Our results suggested a novel mechanism of arrestin effect on the suppression of the R* activity in both rods and cones. PMID:25713141

  9. Unsupervised identification of cone photoreceptors in non-confocal adaptive optics scanning light ophthalmoscope images

    PubMed Central

    Bergeles, Christos; Dubis, Adam M.; Davidson, Benjamin; Kasilian, Melissa; Kalitzeos, Angelos; Carroll, Joseph; Dubra, Alfredo; Michaelides, Michel; Ourselin, Sebastien

    2017-01-01

    Precise measurements of photoreceptor numerosity and spatial arrangement are promising biomarkers for the early detection of retinal pathologies and may be valuable in the evaluation of retinal therapies. Adaptive optics scanning light ophthalmoscopy (AOSLO) is a method of imaging that corrects for aberrations of the eye to acquire high-resolution images that reveal the photoreceptor mosaic. These images are typically graded manually by experienced observers, obviating the robust, large-scale use of the technology. This paper addresses unsupervised automated detection of cones in non-confocal, split-detection AOSLO images. Our algorithm leverages the appearance of split-detection images to create a cone model that is used for classification. Results show that it compares favorably to the state-of-the-art, both for images of healthy retinas and for images from patients affected by Stargardt disease. The algorithm presented also compares well to manual annotation while excelling in speed. PMID:28663928

  10. EML1 (CNG-modulin) controls light sensitivity in darkness and under continuous illumination in zebrafish retinal cone photoreceptors.

    PubMed

    Korenbrot, Juan I; Mehta, Milap; Tserentsoodol, Nomingerel; Postlethwait, John H; Rebrik, Tatiana I

    2013-11-06

    The ligand sensitivity of cGMP-gated (CNG) ion channels in cone photoreceptors is modulated by CNG-modulin, a Ca(2+)-binding protein. We investigated the functional role of CNG-modulin in phototransduction in vivo in morpholino-mediated gene knockdown zebrafish. Through comparative genomic analysis, we identified the orthologue gene of CNG-modulin in zebrafish, eml1, an ancient gene present in the genome of all vertebrates sequenced to date. We compare the photoresponses of wild-type cones with those of cones that do not express the EML1 protein. In the absence of EML1, dark-adapted cones are ∼5.3-fold more light sensitive than wild-type cones. Previous qualitative studies in several nonmammalian species have shown that immediately after the onset of continuous illumination, cones are less light sensitive than in darkness, but sensitivity then recovers over the following 15-20 s. We characterize light sensitivity recovery in continuously illuminated wild-type zebrafish cones and demonstrate that sensitivity recovery does not occur in the absence of EML1.

  11. EML1 (CNG-Modulin) Controls Light Sensitivity in Darkness and under Continuous Illumination in Zebrafish Retinal Cone Photoreceptors

    PubMed Central

    Mehta, Milap; Tserentsoodol, Nomingerel; Postlethwait, John H.; Rebrik, Tatiana I.

    2013-01-01

    The ligand sensitivity of cGMP-gated (CNG) ion channels in cone photoreceptors is modulated by CNG-modulin, a Ca2+-binding protein. We investigated the functional role of CNG-modulin in phototransduction in vivo in morpholino-mediated gene knockdown zebrafish. Through comparative genomic analysis, we identified the orthologue gene of CNG-modulin in zebrafish, eml1, an ancient gene present in the genome of all vertebrates sequenced to date. We compare the photoresponses of wild-type cones with those of cones that do not express the EML1 protein. In the absence of EML1, dark-adapted cones are ∼5.3-fold more light sensitive than wild-type cones. Previous qualitative studies in several nonmammalian species have shown that immediately after the onset of continuous illumination, cones are less light sensitive than in darkness, but sensitivity then recovers over the following 15–20 s. We characterize light sensitivity recovery in continuously illuminated wild-type zebrafish cones and demonstrate that sensitivity recovery does not occur in the absence of EML1. PMID:24198367

  12. A distinct contribution of short-wavelength-sensitive cones to light-evoked activity in the mouse pretectal olivary nucleus.

    PubMed

    Allen, Annette E; Brown, Timothy M; Lucas, Robert J

    2011-11-16

    Melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) combine inputs from outer-retinal rod/cone photoreceptors with their intrinsic phototransduction machinery to drive a wide range of so-called non-image-forming (NIF) responses to light. Defining the contribution of each photoreceptor class to evoked responses is vital for determining the degree to which our sensory capabilities depend on melanopsin and for optimizing NIF responses to benefit human health. We addressed this problem by recording electrophysiological responses in the mouse pretectal olivary nucleus (PON) (a target of ipRGCs and origin of the pupil light reflex) to a range of gradual and abrupt changes in light intensity. Dim stimuli drove minimal changes in PON activity, suggesting that rods contribute little under these conditions. To separate cone from melanopsin influences, we compared responses to short (460 nm) and longer (600/655 nm) wavelengths in mice carrying a red shifted cone population (Opn1mw®) or lacking melanopsin (Opn4⁻/⁻). Our data reveal a surprising difference in the quality of information available from medium- and short-wavelength-sensitive cones. The majority cone population (responsive to 600/655 nm) supported only transient changes in firing and responses to relatively sudden changes in light intensity. In contrast, cones uniquely sensitive to the shorter wavelength (S-cones) were better able to drive responses to gradual changes in illuminance, contributed a distinct off inhibition, and at least partially recapitulated the ability of melanopsin to sustain responses under continuous illumination. These data reveal a new role for S-cones unrelated to color vision and suggest renewed consideration of cone contributions to NIF vision at shorter wavelengths.

  13. The Gauge-Field Propagator in Light-Cone Gauge: Which is the Correct One?

    NASA Astrophysics Data System (ADS)

    Mantovani, L.; Bacchetta, A.; Pasquini, B.; Xiong, X.

    2017-03-01

    In the literature one can find two different expressions for the gauge-field propagator in light-cone gauge, containing the sum of three rather than two terms. The question of which of the two is the correct one has been a subject of debate. We propose a solution to this question by evaluating one-loop level processes in QED, both in the covariant approach in the light-cone gauge and in the light-front time-ordered perturbation theory (TOPT) approach, proving the equivalence between the two formulations of the theory. The form of the propagator turns out to be crucial in the proof, in particular as concerns its relation with the diagrams containing instantaneously propagating photons and instantaneous interactions. We show that the diagrams in light-front TOPT with instantaneous photons can be recovered in the covariant approach starting from the propagators with only two terms. Our proof of the equivalence clarifies which form should be used for the gauge-field propagator in the covariant approach. This result naturally applies to the QCD case also.

  14. Exclusive Processes in Quantum Chromodynamics and the Light-Cone Fock Representation

    SciTech Connect

    Brodsky, Stanley J.

    2000-12-07

    Exclusive processes provide a window into the bound state structure of hadrons in QCD as well as the fundamental processes which control hadron dynamics at the amplitude level. The natural calculus for describing bound state structure of relativistic composite systems needed for describing exclusive amplitudes is the light-cone Fock expansion which encodes the multi-quark, gluonic, and color correlations of a hadron in terms of frame-independent wavefunctions. In hard exclusive processes in which hadrons receive a large momentum transfer, perturbative QCD leads to factorization theorems which separate the physics of bound state structure from that of the relevant quark and gluonic hard-scattering reactions which underlie these reactions. At leading twist, the bound state physics is encoded in terms of universal ''distribution amplitudes,'' the fundamental theoretical quantities which describe the valence quark substructure of hadrons as well as nuclei. The combination of discretized light-cone quantization and transverse lattice methods are now providing nonperturbative predictions for the pion distribution amplitude. A basic feature of the gauge theory formalism is ''color transparency,'' the absence of initial and final state interactions of rapidly-moving compact color-singlet states. Other applications of the factorization formalism are briefly discussed, including semileptonic B decays, deeply virtual Compton scattering, and dynamical higher twist effects in inclusive reactions. A new type of jet production reaction, ''self-resolving diffractive interactions'' provide empirical constraints on the light-cone wavefunctions of hadrons in terms of their quark and gluon degrees of freedom as well as the composition of nuclei in terms of their nucleon and mesonic degrees of freedom.

  15. Light-induced resistance changes in retinal rods and cones of the tiger Salamander

    PubMed Central

    Lasansky, A.; Marchiafava, P. L.

    1974-01-01

    1. The electrical properties of retinal rods and cones of the larval tiger salamander were investigated with intracellular electrodes, and the cells identified by means of dye injections. 2. Both types of photoreceptors are hyperpolarized by illumination. Following stimulation with brief flashes of dim light, rod responses show a slower time course than cone responses; with bright flashes, rod responses can be recognized because of their long recovery time. 3. Values of input resistance were derived from the voltage displacement induced by constant current pulses in darkness or at the peak of the photoresponse. The input resistance following illumination was also calculated from the effect of steady polarizing currents on the amplitude of the photoresponse. 4. In darkness, the input resistance of the rod cells is time- and voltage-dependent, but the voltage—current relations of most cells have a linear region which includes the physiological limits of membrane potential. At the peak of the photoresponse, the input resistance (slope of the linear region of the v—i relations) is decreased. 5. Cone cells show approximately linear v—i relations. As reported by previous authors, illumination increases the input resistance. 6. These results support the current view that the cone photoresponse is the consequence of a reduction in the permeability of channels which in darkness shunt the membrane. In rods, however, it appears that the main effect of illumination is to increase the permeability of the membrane to ions for which the equilibrium potential is more negative than the membrane potential in darkness. ImagesFig. 1Fig. 2Fig. 3Fig. 4Fig. 5 PMID:4818491

  16. Strong coupling constant of negative parity octet baryons with light pseudoscalar mesons in light cone QCD sum rules

    NASA Astrophysics Data System (ADS)

    Aliev, T. M.; Savcı, M.

    2017-01-01

    The strong coupling constants of the π and K mesons with negative parity octet baryons are estimated within the light cone QCD sum rules. It is observed that all strong coupling constants, similarly to the case for the positive parity baryons, can be described in terms of three invariant functions, where two of them correspond to the well known F and D couplings in the SU(3)f symmetry, and the third function describes the SU(3)f symmetry violating effects. We compare our predictions on the strong coupling constants of pseudoscalar mesons of negative parity baryons with those corresponding to the strong coupling constants for the positive parity baryons.

  17. Light-cone Sum Rules in Soft-Collinear Effective Theory

    SciTech Connect

    De Fazio, Fulvia; Feldmann, Thorsten; Hurth, Tobias; /CERN /SLAC

    2005-06-20

    We derive light-cone sum rules (LCSRs) for exclusive B-meson decays into light energetic hadrons from correlation functions within soft-collinear effective theory (SCET). In these sum rules the short-distance scale refers to ''hard-collinear'' interactions with virtualities of order {Lambda}{sub QCD}m{sub b}. Hard scales (related to virtualities of order m{sub b}{sup 2}) are integrated out and enter via external coefficient functions in the sum rule. Soft dynamics is encoded in light-cone distribution amplitudes for the B-meson, which describe both the factorizable and non-factorizable contributions to exclusive B-meson decay amplitudes. As an example, we provide a detailed study of the SCET sum rule for the B {yields} {pi} transition form factor at large recoil, including radiative corrections from hard-collinear loop diagrams at first order in the strong coupling constant. We find remarkable conceptual and numerical differences with the heavy-quark limit of the conventional LCSR approach in QCD.

  18. Tree level semileptonic {sigma}{sub b} to nucleon decay in light cone QCD sum rules

    SciTech Connect

    Azizi, K.; Ozpineci, A.; Bayar, M.; Sarac, Y.

    2009-08-01

    Using the most general form of the interpolating current of the heavy spin 1/2, {sigma}{sub b} baryon and distribution amplitudes of the nucleon, the transition form factors of the semileptonic {sigma}{sub b}{yields}Nl{nu} decay are calculated in the framework of light-cone QCD sum rules. It is obtained that the form factors satisfy the heavy quark effective theory relations. The obtained results for the related form factors are used to estimate the decay rate of this transition.

  19. {kappa}K{sup +{pi}-} vertex in light cone QCD sum rules

    SciTech Connect

    Baytemir, G.; Sarac, Y.; Yilmaz, O.

    2010-05-01

    In this work we study the {kappa}K{sup +{pi}-} vertex in the framework of light cone QCD sum rules. We predict the coupling constant g{sub {kappa}K}{sup +}{sub {pi}}{sup -} to be g{sub {kappa}K}{sup +}{sub {pi}}{sup -}=(6.0{+-}1.0) GeV and estimate the scalar f{sub 0}-{sigma} mixing angle from the experimental ratio g{sup 2}({kappa}{yields}K{pi})/g{sup 2}({sigma}{yields}{pi}{pi}).

  20. The CST: Its Achievements and Its Connection to the Light Cone

    DOE PAGES

    Gross, Franz

    2017-01-19

    since its inception in 1969, I have reviewed applications of the Covariant Spectator Theory (CST). The applications I discuss here include calculations of NN scattering, 3N bound states, electro- magnetic form factors of few-nucleon systems, and the recent successes in describing the dynamical generation of quark mass and the meson spectrum using a chirially invariant quark-antiquark interaction that includes confinement. Furthermore I will discuss the common origin of the Light Cone technique and the CST, which dates back to the 1970's.

  1. Flavor changing neutral current transition of B to a1 with light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Momeni, S.; Khosravi, R.; Falahati, F.

    2017-01-01

    The B →a1ℓ+ℓ- decays occur by the electroweak penguin and box diagrams, which can be performed through the flavor changing neutral current (FCNC). We calculate the form factors of the FCNC B →a1 transitions in the light-cone sum rules approach, up to twist-4 distribution amplitudes of the axial vector meson a1. Forward-backward asymmetry, as well as branching ratios of B →a1ℓ+ℓ-, and B →a1γ decays are considered. A comparison is also made between our results and the predictions of other methods.

  2. g{sub VS}{gamma} coupling constant in light cone QCD

    SciTech Connect

    Aydin, C.; Keskin, F.; Yilmaz, A. H.; Aydin, S. H.

    2011-11-01

    We recalculated the coupling constants g{sub {phi}{sigma}{gamma}}, g{sub {phi}a{sub 0}{gamma}}, g{sub {omega}{sigma}{gamma}}, g{sub a{sub 0}{omega}{gamma}}, g{sub {rho}{sigma}{gamma}}, and g{sub a{sub 0}{rho}{gamma}} by taking into account the contributions of the three-particle up to twist-4 distribution amplitudes of the photon involving quark-gluon and quark-anti-quark-photon fields in the light-cone sum-rule framework.

  3. The geometry of the light-cone cell decomposition of moduli space

    SciTech Connect

    Garner, David Ramgoolam, Sanjaye

    2015-11-15

    The moduli space of Riemann surfaces with at least two punctures can be decomposed into a cell complex by using a particular family of ribbon graphs called Nakamura graphs. We distinguish the moduli space with all punctures labelled from that with a single labelled puncture. In both cases, we describe a cell decomposition where the cells are parametrised by graphs or equivalence classes of finite sequences (tuples) of permutations. Each cell is a convex polytope defined by a system of linear equations and inequalities relating light-cone string parameters, quotiented by the automorphism group of the graph. We give explicit examples of the cell decomposition at low genus with few punctures.

  4. Light Cone Sum Rules for gamma*N ->Delta Transition Form Factors

    SciTech Connect

    V.M. Braun; A. Lenz; G. Peters; A. Radyushkin

    2006-02-01

    A theoretical framework is suggested for the calculation of {gamma}* N {yields} {Delta} transition form factors using the light-cone sum rule approach. Leading-order sum rules are derived and compared with the existing experimental data. We find that the transition form factors in a several GeV region are dominated by the ''soft'' contributions that can be thought of as overlap integrals of the valence components of the hadron wave functions. The ''minus'' components of the quark fields contribute significantly to the result, which can be reinterpreted as large contributions of the quark orbital angular momentum.

  5. Renormalization-group evolution of the B-meson light-cone distribution amplitude.

    PubMed

    Lange, Björn O; Neubert, Matthias

    2003-09-05

    An integro-differential equation governing the evolution of the leading-order B-meson light-cone distribution amplitude is derived. The anomalous dimension in this equation contains a logarithm of the renormalization scale, whose coefficient is identified with the cusp anomalous dimension of Wilson loops. The exact solution of the evolution equation is obtained, from which the asymptotic behavior of the distribution amplitude is derived. These results can be used to resum Sudakov logarithms entering the hard-scattering kernels in QCD factorization theorems for exclusive B decays.

  6. The impact of QCD and light-cone quantum mechanics on nuclear physics

    SciTech Connect

    Brodsky, S.J.; Schlumpf, F.

    1994-12-01

    We discuss a number of novel applications of Quantum Chromodynamics to nuclear structure and dynamics, such as the reduced amplitude formalism for exclusive nuclear amplitudes. We particularly emphasize the importance of light-cone Hamiltonian and Fock State methods as a tool for describing the wavefunctions of composite relativistic many-body systems and their interactions. We also show that the use of covariant kinematics leads to nontrivial corrections to the standard formulae for the axial, magnetic, and quadrupole moments of nucleons and nuclei.

  7. Improved Light Cone Model calculation of strangeness asymmetry in the proton

    NASA Astrophysics Data System (ADS)

    Budnik, Garrett; Fox, Jordan; Tuppan, Sam

    2014-09-01

    We expect strangeness in the proton from the Heisenberg uncertainty principle, which allows for the proton to split into a meson and a baryon, such as a K and a Λ. Our goal is to accurately model the momentum distributions of the strange quarks and anti-strange quarks in the proton. We choose the Light Cone Model because it is a natural explanation for strangeness and for s (x) ≠ s (x) . In the Light Cone Model of Cao and Signal, α is a single parameter in the meson-baryon fluctuation functions f (y) and in the s and s distributions of the mesons and baryons. These functions are exponentials in which α is related to the spatial extent of the particles. Because the s and s are in different environments, we explore an array of values for α which reflect the sizes of the particles and study this effect on our model. We compare our results to global pdfs and experimental data from NuTeV, HERMES and ATLAS. We expect strangeness in the proton from the Heisenberg uncertainty principle, which allows for the proton to split into a meson and a baryon, such as a K and a Λ. Our goal is to accurately model the momentum distributions of the strange quarks and anti-strange quarks in the proton. We choose the Light Cone Model because it is a natural explanation for strangeness and for s (x) ≠ s (x) . In the Light Cone Model of Cao and Signal, α is a single parameter in the meson-baryon fluctuation functions f (y) and in the s and s distributions of the mesons and baryons. These functions are exponentials in which α is related to the spatial extent of the particles. Because the s and s are in different environments, we explore an array of values for α which reflect the sizes of the particles and study this effect on our model. We compare our results to global pdfs and experimental data from NuTeV, HERMES and ATLAS. This research has been supported in part by the Research in Undergraduate Institutions program of the National Science Foundation, Grant No. 1205686.

  8. Drell-Yan processes, transversity, and light-cone wave functions

    NASA Astrophysics Data System (ADS)

    Pasquini, B.; Pincetti, M.; Boffi, S.

    2007-08-01

    The unpolarized, helicity, and transversity distributions of quarks in the proton are calculated in the overlap representation of light-cone wave functions truncated to the lowest order Fock-space components with three valence quarks. The three distributions at the hadronic scale satisfy an interesting relation consistent with the Soffer inequality. Results are derived in a relativistic quark model including evolution up to the next-to-leading order. Predictions for the double transverse-spin asymmetry in Drell-Yan dilepton production initiated by proton-antiproton collisions are presented. Asymmetries of about 20% 30% are found in the kinematic conditions of the PAX experiment.

  9. Thermalization and light cones in a model with weak integrability breaking

    DOE PAGES

    Bertini, Bruno; Essler, Fabian H. L.; Groha, Stefan; ...

    2016-12-09

    Here, we employ equation-of-motion techniques to study the nonequilibrium dynamics in a lattice model of weakly interacting spinless fermions. Our model provides a simple setting for analyzing the effects of weak integrability-breaking perturbations on the time evolution after a quantum quench. We establish the accuracy of the method by comparing results at short and intermediate times to time-dependent density matrix renormalization group computations. For sufficiently weak integrability-breaking interactions we always observe prethermalization plateaus, where local observables relax to nonthermal values at intermediate time scales. At later times a crossover towards thermal behavior sets in. We determine the associated time scale,more » which depends on the initial state, the band structure of the noninteracting theory, and the strength of the integrability-breaking perturbation. Our method allows us to analyze in some detail the spreading of correlations and in particular the structure of the associated light cones in our model. We find that the interior and exterior of the light cone are separated by an intermediate region, the temporal width of which appears to scale with a universal power law t1/3.« less

  10. Thermalization and light cones in a model with weak integrability breaking

    SciTech Connect

    Bertini, Bruno; Essler, Fabian H. L.; Groha, Stefan; Robinson, Neil J.

    2016-12-09

    Here, we employ equation-of-motion techniques to study the nonequilibrium dynamics in a lattice model of weakly interacting spinless fermions. Our model provides a simple setting for analyzing the effects of weak integrability-breaking perturbations on the time evolution after a quantum quench. We establish the accuracy of the method by comparing results at short and intermediate times to time-dependent density matrix renormalization group computations. For sufficiently weak integrability-breaking interactions we always observe prethermalization plateaus, where local observables relax to nonthermal values at intermediate time scales. At later times a crossover towards thermal behavior sets in. We determine the associated time scale, which depends on the initial state, the band structure of the noninteracting theory, and the strength of the integrability-breaking perturbation. Our method allows us to analyze in some detail the spreading of correlations and in particular the structure of the associated light cones in our model. We find that the interior and exterior of the light cone are separated by an intermediate region, the temporal width of which appears to scale with a universal power law t1/3.

  11. Orbital structure of quarks inside the nucleon in the light-cone diquark model

    SciTech Connect

    Lu Zhun; Schmidt, Ivan

    2010-11-01

    We study the orbital angular momentum structure of the quarks inside the proton. By employing the light-cone diquark model and the overlap representation formalism, we calculate the chiral-even generalized parton distribution functions H{sub q}(x,{xi},{Delta}{sup 2}), H-tilde{sub q}(x,{xi},{Delta}{sup 2}), and E{sub q}(x,{xi},{Delta}{sup 2}) at zero skewedness for q=u and d quarks. In our model, E{sub u} and E{sub d} have opposite sign with similar size. Those generalized parton distribution functions are applied to calculate the orbital angular momentum distributions, showing that L{sub u}(x) is positive, while L{sub d}(x) is consistent with zero compared with L{sub u}(x). We introduce the impact parameter dependence of the quark orbital angular momentum distribution. It describes the position space distribution of the quark orbital angular momentum at given x. We found that the impact parameter dependence of the quark orbital angular momentum distribution is axially symmetric in the light-cone diquark model.

  12. Thermalization and light cones in a model with weak integrability breaking

    NASA Astrophysics Data System (ADS)

    Bertini, Bruno; Essler, Fabian H. L.; Groha, Stefan; Robinson, Neil J.

    2016-12-01

    We employ equation-of-motion techniques to study the nonequilibrium dynamics in a lattice model of weakly interacting spinless fermions. Our model provides a simple setting for analyzing the effects of weak integrability-breaking perturbations on the time evolution after a quantum quench. We establish the accuracy of the method by comparing results at short and intermediate times to time-dependent density matrix renormalization group computations. For sufficiently weak integrability-breaking interactions we always observe prethermalization plateaus, where local observables relax to nonthermal values at intermediate time scales. At later times a crossover towards thermal behavior sets in. We determine the associated time scale, which depends on the initial state, the band structure of the noninteracting theory, and the strength of the integrability-breaking perturbation. Our method allows us to analyze in some detail the spreading of correlations and in particular the structure of the associated light cones in our model. We find that the interior and exterior of the light cone are separated by an intermediate region, the temporal width of which appears to scale with a universal power law t1 /3.

  13. Spinon and bound-state excitation light cones in Heisenberg XXZ chains

    NASA Astrophysics Data System (ADS)

    de Paula, A. L.; Bragança, H.; Pereira, R. G.; Drumond, R. C.; Aguiar, M. C. O.

    2017-01-01

    We investigate the out-of-equilibrium dynamics after a local quench that connects two spin-1/2 XXZ chains prepared in the ground state of the Hamiltonian in different phases, one in the ferromagnetic phase and the other in the critical phase. We analyze the time evolution of the on-site magnetization and bipartite entanglement entropy via adaptive time-dependent density matrix renormalization group. In systems with short-range interactions, such as the one we consider, the velocity of information transfer is expected to be bounded, giving rise to a light-cone effect. Interestingly, our results show that, when the anisotropy parameter of the critical chain is sufficiently close to that of the isotropic ferromagnet, the light cone is determined by the velocity of spin-wave bound states that propagate faster than single-particle ("spinon") excitations. Furthermore, we investigate how the system approaches equilibrium in the inhomogeneous ground state of the connected system, in which the ferromagnetic chain induces a nonzero magnetization in the critical chain in the vicinity of the interface.

  14. Automated laser guidance of neuronal growth cones using a spatial light modulator.

    PubMed

    Carnegie, David J; Cizmár, Tomás; Baumgartl, Jörg; Gunn-Moore, Frank J; Dholakia, Kishan

    2009-11-01

    The growth cone of a developing neuron can be guided using a focused infra-red (IR) laser beam [1]. In previous setups this process has required a significant amount of user intervention to adjust continuously the laser beam to guide the growing neuron. Previously, a system using an acousto-optical deflector (AOD) has been developed to steer the beam [2]. However, to enhance the controllability of this system, here we demonstrate the use of a computer controlled spatial light modulator (SLM) to steer and manipulate the shape of a laser beam for use in guided neuronal growth. This new experimental setup paves the way to enable a comprehensive investigation into beam shaping effects on neuronal growth and we show neuronal growth initiated by a Bessel light mode. This is a robust platform to explore the biochemistry of this novel phenomenon.

  15. Three-quark light-cone amplitudes of the proton and quark orbital-motion-dependent observables

    NASA Astrophysics Data System (ADS)

    Ji, Xiangdong; Ma, Jian-Ping; Yuan, Feng

    2003-03-01

    We study the three-quark light-cone amplitudes of the proton including quarks' transverse momenta. We classify these amplitudes using a newly-developed method in which light-cone wave functions are constructed from a class of light-cone matrix elements. We derive the constraints on the amplitudes from parity and time-reversal symmetries. We use the amplitudes to calculate the physical observables which vanish when the quark orbital angular momentum is absent. These include transverse-momentum dependent parton distributions Δ qT( x, k⊥), qT( x, k⊥), δq( x, k⊥), and δqL( x, k⊥), twist-three parton distributions gT( x) and hL( x), helicity-flip generalized parton distributions E( x, ξ=0, Q2) and its associates, and the Pauli form factor F2( Q2).

  16. Light and electron microscopical visualization of anterogradely labelled corticospinal growth cones using a new combination of HRP staining techniques.

    PubMed

    Joosten, E A

    1991-05-01

    Up until now, the ultrastructural visualization of growth cones of developing long fibre tracts could only be achieved by horseradish peroxidase (HRP) application 'en route', resulting in axonal damage, which in turn may affect growth cone morphology. Besides, this technique results in labelling of passing fibres, thus hampering the identification of axon origin as well as the interpretation of growth cone configuration. In the present investigation a new combination of HRP staining and intensification techniques is presented which makes it possible to visualize anterogradely labelled corticospinal growth cones over long distances in developing rat spinal cord at the light as well as the electron microscopical level. HRP was applied to the originating cells of the corticospinal tract, located in the sensorimotor cortex, and after 24 h was visualized using a procedure which essentially consists of 3 subsequent steps: first a tetramethylbenzidine (TMB)/ammoniumheptamolybdate (AHM) reaction; second diaminobenzidine (DAB)/nickel (Ni) stabilization and finally glucose oxidase intensification. As was verified at the EM level, the staining procedure here described reveals a complete intense black staining of HRP-labelled growth cones of outgrowing corticospinal axons. Therefore, the method described here guarantees a correct analysis of growth cone morphology at the light microscopical and the ultrastructural level. The present procedure is especially valuable in studying the development of long central nervous fibre systems.

  17. Effects of Intraframe Distortion on Measures of Cone Mosaic Geometry from Adaptive Optics Scanning Light Ophthalmoscopy

    PubMed Central

    Cooper, Robert F.; Sulai, Yusufu N.; Dubis, Adam M.; Chui, Toco Y.; Rosen, Richard B.; Michaelides, Michel; Dubra, Alfredo; Carroll, Joseph

    2016-01-01

    Purpose To characterize the effects of intraframe distortion due to involuntary eye motion on measures of cone mosaic geometry derived from adaptive optics scanning light ophthalmoscope (AOSLO) images. Methods We acquired AOSLO image sequences from 20 subjects at 1.0, 2.0, and 5.0° temporal from fixation. An expert grader manually selected 10 minimally distorted reference frames from each 150-frame sequence for subsequent registration. Cone mosaic geometry was measured in all registered images (n = 600) using multiple metrics, and the repeatability of these metrics was used to assess the impact of the distortions from each reference frame. In nine additional subjects, we compared AOSLO-derived measurements to those from adaptive optics (AO)-fundus images, which do not contain system-imposed intraframe distortions. Results We observed substantial variation across subjects in the repeatability of density (1.2%–8.7%), inter-cell distance (0.8%–4.6%), percentage of six-sided Voronoi cells (0.8%–10.6%), and Voronoi cell area regularity (VCAR) (1.2%–13.2%). The average of all metrics extracted from AOSLO images (with the exception of VCAR) was not significantly different than those derived from AO-fundus images, though there was variability between individual images. Conclusions Our data demonstrate that the intraframe distortion found in AOSLO images can affect the accuracy and repeatability of cone mosaic metrics. It may be possible to use multiple images from the same retinal area to approximate a “distortionless” image, though more work is needed to evaluate the feasibility of this approach. Translational Relevance Even in subjects with good fixation, images from AOSLOs contain intraframe distortions due to eye motion during scanning. The existence of these artifacts emphasizes the need for caution when interpreting results derived from scanning instruments. PMID:26933523

  18. Effects of Intraframe Distortion on Measures of Cone Mosaic Geometry from Adaptive Optics Scanning Light Ophthalmoscopy.

    PubMed

    Cooper, Robert F; Sulai, Yusufu N; Dubis, Adam M; Chui, Toco Y; Rosen, Richard B; Michaelides, Michel; Dubra, Alfredo; Carroll, Joseph

    2016-02-01

    To characterize the effects of intraframe distortion due to involuntary eye motion on measures of cone mosaic geometry derived from adaptive optics scanning light ophthalmoscope (AOSLO) images. We acquired AOSLO image sequences from 20 subjects at 1.0, 2.0, and 5.0° temporal from fixation. An expert grader manually selected 10 minimally distorted reference frames from each 150-frame sequence for subsequent registration. Cone mosaic geometry was measured in all registered images (n = 600) using multiple metrics, and the repeatability of these metrics was used to assess the impact of the distortions from each reference frame. In nine additional subjects, we compared AOSLO-derived measurements to those from adaptive optics (AO)-fundus images, which do not contain system-imposed intraframe distortions. We observed substantial variation across subjects in the repeatability of density (1.2%-8.7%), inter-cell distance (0.8%-4.6%), percentage of six-sided Voronoi cells (0.8%-10.6%), and Voronoi cell area regularity (VCAR) (1.2%-13.2%). The average of all metrics extracted from AOSLO images (with the exception of VCAR) was not significantly different than those derived from AO-fundus images, though there was variability between individual images. Our data demonstrate that the intraframe distortion found in AOSLO images can affect the accuracy and repeatability of cone mosaic metrics. It may be possible to use multiple images from the same retinal area to approximate a "distortionless" image, though more work is needed to evaluate the feasibility of this approach. Even in subjects with good fixation, images from AOSLOs contain intraframe distortions due to eye motion during scanning. The existence of these artifacts emphasizes the need for caution when interpreting results derived from scanning instruments.

  19. Light cone in the two-dimensional transverse-field Ising model in time-dependent mean-field theory

    NASA Astrophysics Data System (ADS)

    Hafner, J.; Blass, B.; Rieger, H.

    2016-12-01

    We investigate the propagation of a local perturbation in the two-dimensional transverse-field Ising model with a time-dependent application of the mean-field theory based on the BBGKY hierarchy. We show that the perturbation propagates through the system with a finite velocity and that there is a transition from Manhattan to Euclidian metric, resulting in a light cone with an almost circular shape at sufficiently large distances. The propagation velocity of the perturbation defining the front of the light cone is discussed with respect to the parameters of the Hamiltonian and compared to exact results for the transverse-field Ising model in one dimension.

  20. Relativistic nuclear corrections to the spin structure function of the deuteron in the light-cone variables

    SciTech Connect

    Pavlov, F. F.

    2012-06-15

    The relativistic deuteron has been considered in the light-cone formalism as a system of two strongly interacting nucleons (two-nucleon approximation). The technique for the calculation of the average helicity of the proton in the deuteron has been considered in the light-cone variables. A receipt has been pro-posed for the consistent calculation of relativistic nuclear corrections to the average helicity of the proton in the deuteron and to the spin structure function of the deuteron g{sub 1}{sup D}. Relativistic-correction-induced change in the Bjorken sum rule has been discussed.

  1. Scattering of glue by glue on the light-cone worldsheet. II. Helicityconserving amplitudes

    SciTech Connect

    Chakrabarti, D.; Qiu, J.; Thorn, C. B.

    2006-08-15

    This is the second of a pair of articles on scattering of glue by glue,in which we give the light-cone gauge calculation of the one-loop on-shellhelicity conserving scattering amplitudes for gluon-gluon scattering (neglectingquark loops). The 1/p{sup +} factors in the gluon propagatorare regulated by replacing p{sup +} integrals with discretized sums omitting the p{sup +}=0 terms in each sum. We alsoemploy a novel ultraviolet regulator that is convenient for the light-coneworldsheet description of planar Feynman diagrams. The helicity conservingscattering amplitudes are divergent in the infrared. The infrared divergencesin the elastic one-loop amplitude are shown to cancel, in their contributionto cross sections, against ones in the cross section for unseen bremsstrahlunggluons. We include here the explicit calculation of the latter, because itassumes an unfamiliar form due to the peculiar way discretization of p{sup +} regulates infrared divergences. In resolving the infrareddivergences we employ a covariant definition of jets, which allows a transparentdemonstration of the Lorentz invariance of our final results. Because we usean explicit cutoff of the ultraviolet divergences in exactly four spacetimedimensions, we must introduce explicit counterterms to achieve this finalcovariant result. These counterterms are polynomials in the external momentaof the precise order dictated by power counting. We discuss the modificationsthey entail for the light-cone worldsheet action that reproduces the bareplanar diagrams of the gluonic sector of QCD. The simplest way to do thisis to interpret the QCD string as moving in six spacetime dimensions.

  2. Light-cone anisotropy in the 21 cm signal from the epoch of reionization

    NASA Astrophysics Data System (ADS)

    Zawada, Karolina; Semelin, Benoît; Vonlanthen, Patrick; Baek, Sunghye; Revaz, Yves

    2014-04-01

    Using a suite of detailed numerical simulations, we estimate the level of anisotropy generated by the time evolution along the light cone of the 21 cm signal from the epoch of reionization. Our simulations include the physics necessary to model the signal during both the late emission regime and the early absorption regime, namely X-ray and Lyman band 3D radiative transfer in addition to the usual dynamics and ionizing UV transfer. The signal is analysed using correlation functions perpendicular and parallel to the line of sight. We reproduce general findings from previous theoretical studies: the overall amplitude of the correlations and the fact that the light-cone anisotropy is visible only on large scales (100 comoving Mpc). However, the detailed behaviour is different. We find that, at three different epochs, the amplitudes of the correlations along and perpendicular to the line of sight differ from each other, indicating anisotropy. We show that these three epochs are associated with three events of the global reionization history: the overlap of ionized bubbles, the onset of mild heating by X-rays in regions around the sources, and the onset of efficient Lyman α coupling in regions around the sources. We find that a 20 × 20 deg2 survey area may be necessary to mitigate sample variance when we use the directional correlation functions. On a 100 Mpc (comoving) scale, we show that the light-cone anisotropy dominates over the anisotropy generated by peculiar velocity gradients computed in the linear regime. By modelling instrumental noise and limited resolution, we find that the anisotropy should be easily detectable by the Square Kilometre Array, assuming perfect foreground removal, the limiting factor being a large enough survey size. In the case of the Low-Frequency Array for radio astronomy, it is likely that only one anisotropy episode (ionized bubble overlap) will fall in the observing frequency range. This episode will be detectable only if sample

  3. Gauge-transformation properties of cosmological observables and its application to the light-cone average

    NASA Astrophysics Data System (ADS)

    Yoo, Jaiyul; Durrer, Ruth

    2017-09-01

    Theoretical descriptions of observable quantities in cosmological perturbation theory should be independent of coordinate systems. This statement is often referred to as gauge-invariance of observable quantities, and the sanity of their theoretical description is verified by checking its gauge-invariance. We argue that cosmological observables are invariant scalars under diffeomorphisms and their theoretical description is gauge-invariant, only at linear order in perturbations. Beyond linear order, they are usually not gauge-invariant, and we provide the general law for the gauge-transformation that the perturbation part of an observable does obey. We apply this finding to derive the second-order expression for the observational light-cone average in cosmology and demonstrate that our expression is indeed invariant under diffeomorphisms.

  4. On Quantization in Light-cone Variables Compatible with Wavelet Transform

    NASA Astrophysics Data System (ADS)

    Altaisky, M. V.; Kaputkina, N. E.

    2016-06-01

    Canonical quantization of quantum field theory models is inherently related to the Lorentz invariant partition of classical fields into the positive and the negative frequency parts u( x) = u +( x) + u -( x), performed with the help of Fourier transform in Minkowski space. That is the commutation relations are being established between nonlocalized solutions of field equations. At the same time the construction of divergence free physical theory requires the separation of the contributions of different space-time scales. In present paper, using the light-cone variables, we propose a quantization procedure which is compatible with separation of scales using continuous wavelet transform, as described in our previous paper (Altaisky, M.V., Kaputkina, N.E.: Phys. Rev. D 88, 025015 2013).

  5. Stochastic light-cone CTMRG: a new DMRG approach to stochastic models

    NASA Astrophysics Data System (ADS)

    Kemper, A.; Gendiar, A.; Nishino, T.; Schadschneider, A.; Zittartz, J.

    2003-01-01

    We develop a new variant of the recently introduced stochastic transfer matrix DMRG which we call stochastic light-cone corner-transfer-matrix DMRG (LCTMRG). It is a numerical method to compute dynamic properties of one-dimensional stochastic processes. As suggested by its name, the LCTMRG is a modification of the corner-transfer-matrix DMRG, adjusted by an additional causality argument. As an example, two reaction-diffusion models, the diffusion-annihilation process and the branch-fusion process are studied and compared with exact data and Monte Carlo simulations to estimate the capability and accuracy of the new method. The number of possible Trotter steps of more than 105 shows a considerable improvement on the old stochastic TMRG algorithm.

  6. B → Vℓ+ℓ- in the Standard Model from light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Bharucha, Aoife; Straub, David M.; Zwicky, Roman

    2016-08-01

    We present B q → ρ, B q → ω, B q → K ∗, B s → K ∗ and B s → ϕ form factors from light-cone sum rules (LCSR) at {O}({α}_s) for twist-2 and 3 and {O}({α}_s^0) for twist-4 with updated hadronic input parameters. Three asymptotic light-cone distribution amplitudes of twist-4 (and 5) are determined, necessary for the form factors to obey the equations of motion. It is argued that the latter constrain the uncertainty of tensor-to-vector form factor ratios thereby improving the prediction of zeros of helicity amplitudes of major importance for B → K ∗ℓℓ angular observables. We provide easy-to-use fits to the LCSR results, including the full error correlation matrix, in all modes at low q 2 as well as combined fits to LCSR and lattice results covering the entire kinematic range for B q → K ∗, B s → K ∗ and B s → ϕ. The error correlation matrix avoids the problem of overestimating the uncertainty in phenomenological applications. Using the new form factors and recent computations of non-factorisable contributions we provide Standard Model predictions for B → K ∗γ as well as B → K ∗ℓ+ℓ- and B s → ϕμ + μ - at low dilepton invariant mass. Employing our B → ( ρ,ω) form factor results we extract the CKM element | V ub| from the semileptonic decays B → ( ρ, ω)ℓ ν and find good agreement with other exclusive determinations.

  7. Generalized scaling function from light-cone gauge AdS 5 × S 5 superstring

    NASA Astrophysics Data System (ADS)

    Giombi, S.; Ricci, R.; Roiban, R.; Tseytlin, A. A.; Vergu, C.

    2010-06-01

    We revisit the computation of the 2-loop correction to the energy of a folded spinning string in AdS 5 with an angular momentum J in S 5 in the scaling limit ln S ≫ 1, J/{sqrt {λ ln S}} = {text{fixed}} . This correction gives the third term in the strong-coupling expansion of the generalized scaling function. The computation, using the AdS light-cone gauge approach developed in our previous paper, is done by expanding the AdS 5 × S 5 superstring partition function near the generalized null cusp world surface associated to the spinning string solution. The result corrects and extends the previous conformal gauge result of arXiv:0712.2479 and is found to be in complete agreement with the corresponding terms in the generalized scaling function as obtained from the asymptotic Bethe ansatz in arXiv:0805.4615 (and also partially from the quantum O(6) model and the Bethe ansatz data in arXiv:0809.4952). This provides a highly nontrivial strong coupling comparison of the Bethe ansatz proposal with the quantum AdS 5 × S 5 superstring theory, which goes beyond the leading semiclassical term effectively controlled by the underlying algebraic curve. The 2-loop computation we perform involves all the structures in the AdS light-cone gauge superstring action of hep-th/0009171 and thus tests its ultraviolet finiteness and, through the agreement with the Bethe ansatz, its quantum integrability. We do most of the computations for a generalized spinning string solution or the corresponding null cusp surface that involves both the orbital momentum and the winding in a large circle of S 5.

  8. Light-output enhancement of GaN-based light-emitting diodes with three-dimensional backside reflectors patterned by microscale cone array.

    PubMed

    Huang, Huamao; Hu, Jinyong; Wang, Hong

    2014-01-01

    Three-dimensional (3D) backside reflector, compared with flat reflectors, can improve the probability of finding the escape cone for reflecting lights and thus enhance the light-extraction efficiency (LEE) for GaN-based light-emitting diode (LED) chips. A triangle-lattice of microscale SiO2 cone array followed by a 16-pair Ti3O5/SiO2 distributed Bragg reflector (16-DBR) was proposed to be attached on the backside of sapphire substrate, and the light-output enhancement was demonstrated by numerical simulation and experiments. The LED chips with flat reflectors or 3D reflectors were simulated using Monte Carlo ray tracing method. It is shown that the LEE increases as the reflectivity of backside reflector increases, and the light-output can be significantly improved by 3D reflectors compared to flat counterparts. It can also be observed that the LEE decreases as the refractive index of the cone material increases. The 3D 16-DBR patterned by microscale SiO2 cone array benefits large enhancement of LEE. This microscale pattern was prepared by standard photolithography and wet-etching technique. Measurement results show that the 3D 16-DBR can provide 12.1% enhancement of wall-plug efficiency, which is consistent with the simulated value of 11.73% for the enhancement of LEE.

  9. An Automated Reference Frame Selection (ARFS) Algorithm for Cone Imaging with Adaptive Optics Scanning Light Ophthalmoscopy

    PubMed Central

    Salmon, Alexander E.; Cooper, Robert F.; Langlo, Christopher S.; Baghaie, Ahmadreza; Dubra, Alfredo; Carroll, Joseph

    2017-01-01

    Purpose To develop an automated reference frame selection (ARFS) algorithm to replace the subjective approach of manually selecting reference frames for processing adaptive optics scanning light ophthalmoscope (AOSLO) videos of cone photoreceptors. Methods Relative distortion was measured within individual frames before conducting image-based motion tracking and sorting of frames into distinct spatial clusters. AOSLO images from nine healthy subjects were processed using ARFS and human-derived reference frames, then aligned to undistorted AO-flood images by nonlinear registration and the registration transformations were compared. The frequency at which humans selected reference frames that were rejected by ARFS was calculated in 35 datasets from healthy subjects, and subjects with achromatopsia, albinism, or retinitis pigmentosa. The level of distortion in this set of human-derived reference frames was assessed. Results The average transformation vector magnitude required for registration of AOSLO images to AO-flood images was significantly reduced from 3.33 ± 1.61 pixels when using manual reference frame selection to 2.75 ± 1.60 pixels (mean ± SD) when using ARFS (P = 0.0016). Between 5.16% and 39.22% of human-derived frames were rejected by ARFS. Only 2.71% to 7.73% of human-derived frames were ranked in the top 5% of least distorted frames. Conclusion ARFS outperforms expert observers in selecting minimally distorted reference frames in AOSLO image sequences. The low success rate in human frame choice illustrates the difficulty in subjectively assessing image distortion. Translational Relevance Manual reference frame selection represented a significant barrier to a fully automated image-processing pipeline (including montaging, cone identification, and metric extraction). The approach presented here will aid in the clinical translation of AOSLO imaging. PMID:28392976

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

    PubMed

    Sabbah, Shai; Hawryshyn, Craig W

    2013-07-04

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

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

    PubMed Central

    2013-01-01

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

  12. Modulation of cone horizontal cell activity in the teleost fish retina. II. Role of interplexiform cells and dopamine in regulating light responsiveness.

    PubMed

    Yang, X L; Tornqvist, K; Dowling, J E

    1988-07-01

    Following the destruction of the terminals of the dopaminergic interplexiform cells by intraocular injections of 6-hydroxydopamine (6-OHDA), cone horizontal cells exhibited high light responsiveness in prolonged darkness and their responses to moderate and bright full-field flashes were as large as 60 mV. Furthermore, the light responsiveness of these cells in the 6-OHDA-treated retinas was not enhanced by background illumination. The application of dopamine (50 microM) by superfusion to 6-OHDA-treated retinas resulted in a decrease in light responsiveness and changes in response waveform of the cone horizontal cells. Twenty minutes following dopamine application the responses of the cone horizontal cells closely resembled the response of cells recorded in prolonged dark-adapted retinas. Dopamine caused similar changes in cone horizontal cells recorded in light-exposed retinas, but had no obvious effects on rod horizontal cells. The selective dopamine D1 receptor antagonist, Sch 23390, enhanced cone horizontal cell responsiveness when applied to prolonged dark-adapted retinas, mimicking background illumination. The light responsiveness of cone horizontal cells recorded after application of Sch 23390 was less than that for cells in retinas that had been exposed to background lights, but light responsiveness could not be further enhanced by background illumination. Another dopamine antagonist, (+)-butaclamol, was found to have effects similar to Sch 23390 on cone horizontal cells, but (-)-butaclamol, the inactive enantiomer, did not enhance the light responsiveness of these cells. The results suggest that the dopaminergic interplexiform cells play a crucial role in the regulation of cone horizontal cell responsiveness by prolonged darkness and background illumination. These cells may release dopamine tonically in the dark, which suppresses cone horizontal cell responsiveness. Background illumination may decrease dopamine release and liberate cone horizontal cells

  13. Determination of Rod and Cone Influence to the Early and Late Dynamic of the Pupillary Light Response

    PubMed Central

    Kostic, Corinne; Crippa, Sylvain V.; Martin, Catherine; Kardon, Randy H.; Biel, Martin; Arsenijevic, Yvan; Kawasaki, Aki

    2016-01-01

    Purpose This study aims to identify which aspects of the pupil light reflex are most influenced by rods and cones independently by analyzing pupil recordings from different mouse models of photoreceptor deficiency. Methods One-month-old wild type (WT), rodless (Rho−/−), coneless (Cnga3−/−), or photoreceptor less (Cnga3−/−; Rho−/− or Gnat1−/−) mice were subjected to brief red and blue light stimuli of increasing intensity. To describe the initial dynamic response to light, the maximal pupillary constriction amplitudes and the derivative curve of the first 3 seconds were determined. To estimate the postillumination phase, the constriction amplitude at 9.5 seconds after light termination was related to the maximal constriction amplitude. Results Rho−/− mice showed decreased constriction amplitude but more prolonged pupilloconstriction to all blue and red light stimuli compared to wild type mice. Cnga3−/− mice had constriction amplitudes similar to WT however following maximal constriction, the early and rapid dilation to low intensity blue light was decreased. To high intensity blue light, the Cnga3−/− mice demonstrated marked prolongation of the pupillary constriction. Cnga3−/−; Rho−/− mice had no pupil response to red light of low and medium intensity. Conclusions From specific gene defective mouse models which selectively voided the rod or cone function, we determined that mouse rod photoreceptors are highly contributing to the pupil response to blue light stimuli but also to low and medium red stimuli. We also observed that cone cells mainly drive the partial rapid dilation of the initial response to low blue light stimuli. Thus photoreceptor dysfunction can be derived from chromatic pupillometry in mouse models. PMID:27152964

  14. Chromatic organization of cone photoreceptors in the retina of rainbow trout: single cones irreversibly switch from UV (SWS1) to blue (SWS2) light sensitive opsin during natural development.

    PubMed

    Cheng, Christiana L; Flamarique, Iñigo Novales

    2007-12-01

    The retinas of salmonid fishes have single and double cones arranged in square to row formations termed mosaics. The square mosaic unit is formed by four double cones that make the sides of the square with a single (centre) cone in the middle, and a single (corner) cone at each corner of the square when present. Previous research using coho salmon-derived riboprobes on four species of anadromous Pacific salmon has shown that all single cones express a SWS1 (UV sensitive) visual pigment protein (opsin) at hatching, and that these cones switch to a SWS2 (blue light sensitive) opsin during the juvenile period. Whether this opsin switch applies to non-anadromous species, like the rainbow trout, is under debate as species-specific riboprobes have not been used to study opsin expression during development of a trout. As well, a postulated recovery of SWS1 opsin expression in the retina of adult rainbow trout, perhaps via a reverse process to that occurring in the juvenile, has not been investigated. Here, we used in situ hybridization with species-specific riboprobes and microspectrophotometry on rainbow trout retina to show that: (1) single cones in the juvenile switch opsin expression from SWS1 to SWS2, (2) this switch is not reversed in the adult, i.e. all single cones in the main retina continue to express SWS2 opsin, and (3) opsin switches do not occur in double cones: each member expresses one opsin, maximally sensitive to green (RH2) or red (LWS) light. The opsin switch in the single cones of salmonid fishes may be a general process of chromatic organization that occurs during retinal development of most vertebrates.

  15. Intrinsic strange distributions in the nucleon from the light-cone models

    NASA Astrophysics Data System (ADS)

    Salajegheh, Maral

    2015-10-01

    Precise knowledge of the strange and antistrange quark distributions of the nucleon is a major step toward better understanding of the strong interaction and the nucleon structure. Moreover, the s -s ¯ asymmetry in the nucleon plays an important role in some physical processes involving hadrons. The goal of this paper is the study of intrinsic strange contribution to the strange sea of the nucleon. To this aim, we calculate the intrinsic strange distributions from the various light-cone models, including Brodsky, Hoyer, Peterson, and Sakai (BHPS); scalar five-quark; and meson-baryon models and then compare their results. These models can lead to the rather different distributions for the intrinsic strange that are dominated in different values of x . Furthermore, the meson-baryon model leads to the s -s ¯ asymmetry that can be comparable in some situations to the result obtained from the global analysis of PDFs. We also present a simple parametrization for each model prediction of intrinsic strange distribution.

  16. The ρ-meson light-cone distribution amplitudes from lattice QCD

    NASA Astrophysics Data System (ADS)

    Braun, Vladimir M.; Bruns, Peter C.; Collins, Sara; Gracey, John A.; Gruber, Michael; Göckeler, Meinulf; Hutzler, Fabian; Pérez-Rubio, Paula; Schäfer, Andreas; Söldner, Wolfgang; Sternbeck, André; Wein, Philipp

    2017-04-01

    We present the results of a lattice study of the normalization constants and second moments of the light-cone distribution amplitudes of longitudinally and transversely polarized ρ mesons. The calculation is performed using two flavors of dynamical clover fermions at lattice spacings between 0.060 fm and 0.081 fm, different lattice volumes up to m π L = 6.7 and pion masses down to m π = 150 MeV. Bare lattice results are renormalized non-perturbatively using a variant of the RI'-MOM scheme and converted to the \\overline{MS} scheme. The necessary conversion coefficients, which are not available in the literature, are calculated. The chiral extrapolation for the relevant decay constants is worked out in detail. We obtain for the ratio of the tensor and vector coupling constants f ρ T / f ρ = 0.629(8) and the values of the second Gegenbauer moments a 2 ‖ = 0.132(27) and a 2 ⊥ = 0.101(22) at the scale μ = 2 GeV for the longitudinally and transversely polarized ρ mesons, respectively. The errors include the statistical uncertainty and estimates of the systematics arising from renormalization. Discretization errors cannot be estimated reliably and are not included. In this calculation the possibility of ρ → ππ decay at the smaller pion masses is not taken into account.

  17. Multi Dark Lens Simulations: weak lensing light-cones and data base presentation

    NASA Astrophysics Data System (ADS)

    Giocoli, Carlo; Jullo, Eric; Metcalf, R. Benton; de la Torre, Sylvain; Yepes, Gustavo; Prada, Francisco; Comparat, Johan; Göttlober, Stefan; Kyplin, Anatoly; Kneib, Jean-Paul; Petkova, Margarita; Shan, Huan Yuan; Tessore, Nicolas

    2016-09-01

    In this paper we present a large data base of weak lensing light cones constructed using different snapshots from the Big MultiDark simulation (BigMDPL). The ray-tracing through different multiple plane has been performed with the GLAMER code accounting both for single source redshifts and for sources distributed along the cosmic time. This first paper presents weak lensing forecasts and results according to the geometry of the VIPERS-W1 and VIPERS-W4 field of view. Additional fields will be available on our data base and new ones can be run upon request. Our data base also contains some tools for lensing analysis. In this paper we present results for convergence power spectra, one point and high order weak lensing statistics useful for forecasts and for cosmological studies. Covariance matrices have also been computed for the different realizations of the W1 and W4 fields. In addition we compute also galaxy-shear and projected density contrasts for different halo masses at two lens redshift according to the CFHTLS source redshift distribution both using stacking and cross-correlation techniques, finding very good agreement.

  18. Perturbative corrections to Λ b → Λ form factors from QCD light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Ming; Shen, Yue-Long

    2016-02-01

    We compute radiative corrections to Λ b → Λ from factors, at next-to-leading logarithmic accuracy, from QCD light-cone sum rules with Λ b -baryon distribution amplitudes. Employing the diagrammatic approach factorization of the vacuum-to-Λ b -baryon correlation function is justified at leading power in Λ /m b , with the aid of the method of regions. Hard functions entering the factorization formulae are identical to the corresponding matching coefficients of heavy-to-light currents from QCD onto soft-collinear effective theory. The universal jet function from integrating out the hard-collinear fluctuations exhibits richer structures compared with the one involved in the factorization expressions of the vacuum-to- B-meson correlation function. Based upon the QCD resummation improved sum rules we observe that the perturbative corrections at {O}({α}_s) shift the Λ b → Λ from factors at large recoil significantly and the dominant contribution originates from the next-to-leading order jet function instead of the hard coefficient functions. Having at hand the sum rule predictions for the Λ b → Λ from factors we further investigate several decay observables in the electro-weak penguin Λ b → Λ ℓ + ℓ - transitions in the factorization limit (i.e., ignoring the "non-factorizable" hadronic effects which cannot be expressed in terms of the Λ b → Λ from factors), including the invariant mass distribution of the lepton pair, the forward-backward asymmetry in the dilepton system and the longitudinal polarization fraction of the leptonic sector.

  19. Magnetic moment of the XQ state with JP C=1+± in light cone QCD sum rules

    NASA Astrophysics Data System (ADS)

    Agamaliev, A. K.; Aliev, T. M.; Savcı, M.

    2017-02-01

    The magnetic moments of the recently observed resonance Xb(5568 ) by D0 Collaboration and its partner with charm quark are calculated in the framework of the light cone QCD sum rules, by assuming that these resonances are represented as tetraquark states with quantum numbers JP C=1+±. The magnetic moment can play a critical role in the determination of the quantum numbers, as well as give useful information about the inner structure of these mesons.

  20. Radiative decays of negative parity heavy baryons in the framework of the light cone QCD sum rules

    NASA Astrophysics Data System (ADS)

    Agamaliev, A. K.; Aliev, T. M.; Savcı, M.

    2017-02-01

    The transition form factors responsible for the radiative ΣQ →ΛQ γ and ΞQ‧ →ΞQ γ decays of the negative parity baryons are examined within light cone QCD sum rules. The decay widths of the radiative transitions are calculated using the obtained results of the form factors. A comparison of our predictions on decay widths with the corresponding widths of positive parity baryons is given.

  1. Feynman rules for superfields in N = 1 and N = 2 supersymmetric Yang-Mills theories on the light cone

    SciTech Connect

    Ketov, S.V.

    1985-11-01

    This paper considers N = 1 supersymmetric Yang-Mills theories in dimensions d = 4 and d = 6 on the light cone. The N = 2 theory in d = 4 is obtained by dimensional reduction. The results are represented in the superfield formulation of Mandelstam. Feynman rules for the superfields are obtained. The well-known fact is confirmed that the n = 2 theory in d = 4 has only single-loop divergences in the gauge considered.

  2. Fabrication of a nano-cone array on a p-GaN surface for enhanced light extraction efficiency from GaN-based tunable wavelength LEDs.

    PubMed

    Soh, C B; Wang, B; Chua, S J; Lin, Vivian K X; Tan, Rayson J N; Tripathy, S

    2008-10-08

    We report on the fabrication of a nano-cone structured p-GaN surface for enhanced light extraction from tunable wavelength light emitting diodes (LEDs). Prior to p-contact metallization, self-assembled colloidal particles are deposited and used as a mask for plasma etching to create nano-cone structures on the p-GaN layer of LEDs. A well-defined periodic nano-cone array, with an average cone diameter of 300 nm and height of 150 nm, is generated on the p-GaN surface. The photoluminescence emission intensity recorded from the regions with the nano-cone array is increased by two times as compared to LEDs without surface patterning. The light output power from the LEDs with surface nano-cones shows significantly higher electroluminescence intensity at an injection current of 70 mA. This is due to the internal multiple scattering of light from the nano-cone sidewalls. Furthermore, we have shown that with an incorporation of InGaN nanostructures in the quantum well, the wavelength of these surface-patterned LEDs can be tuned from 517 to 488 nm with an increase in the injection current. This methodology may serve as a practical approach to increase the light extraction efficiency from wavelength tunable LEDs.

  3. Isolation of rod and cone contributions to cat ganglion cells by a method of light exchange.

    PubMed

    Rodieck, R W; Rushton, W A

    1976-01-01

    1. The great majority of cat retinal ganglion cells are known to receive signals from rods and from a single (green) cone type. The centre region of the receptive fields of these cells was stimulated by a spot that changed back and forth from orange to white. By adjusting the intensity of the white spot relative to that of the orange a condition could be established at which the photon-catch rate of the rods remained unchanged during the orange-white exchange. At this intensity setting, termed the rod isolept, rods are thus unstimulated by the exchange, however intense, and the ganglion-cell response was found to be due entirely to the green cones. At another intensity setting of the white spot relative to the orange (cone isolept), the photon catch of the green cones remained unchanged during the exchange and ganglion-cell responses were found to arise entirely from the rods. 2. A neutral wedge in the combined exchange beam (but not in the steady background that covered the whole receptive field) regulated the size of the exchange stimulus and thus the magnitude of the ganglion-cell discharge heard from a loud speaker to the exchange. Exchange threshold was the wedge setting at which this change in firing rate could only just be heard. 3. At the cone isolept, cones remain unstimulated however intense the exchange stimulus, and the rod increment threshold curve was determined over its full range from absolute threshold up to saturation. Likewise, at the rod isolept, the cone increment threshold curve was determined over the same intensity range as for the rods. Rod saturation was found to occur at the point where the cone increment threshold curve began to rise from its absolute threshold level toward its Weber region. 4. The exchange approach also enabled both rod and cone dark-adaptation curves following a strong bleaching exposure to be obtained in the same experiment by moving successively between the cone and rod isolepts. At the cone isolept the time course

  4. Single-shot real-time video recording of a photonic Mach cone induced by a scattered light pulse

    PubMed Central

    Liang, Jinyang; Ma, Cheng; Zhu, Liren; Chen, Yujia; Gao, Liang; Wang, Lihong V.

    2017-01-01

    Ultrafast video recording of spatiotemporal light distribution in a scattering medium has a significant impact in biomedicine. Although many simulation tools have been implemented to model light propagation in scattering media, existing experimental instruments still lack sufficient imaging speed to record transient light-scattering events in real time. We report single-shot ultrafast video recording of a light-induced photonic Mach cone propagating in an engineered scattering plate assembly. This dynamic light-scattering event was captured in a single camera exposure by lossless-encoding compressed ultrafast photography at 100 billion frames per second. Our experimental results are in excellent agreement with theoretical predictions by time-resolved Monte Carlo simulation. This technology holds great promise for next-generation biomedical imaging instrumentation. PMID:28116357

  5. Superparticle and superstring in AdS{sub 3} x S{sup 3} Ramond--Ramond background in the light-cone gauge

    SciTech Connect

    Metsaev, R. R.; Tseytlin, A. A.

    2001-07-01

    We discuss superparticle and superstring dynamics in AdS{sub 3} x S{sup 3} supported by R--R 3-form background using light-cone gauge approach. Starting with the superalgebra psu(1,1|2)(circle plus)psu (1,1|2) representing the basic symmetry of this background we find the light-cone superparticle Hamiltonian. We determine the harmonic decomposition of light-cone superfield describing fluctuations of type IIB supergravity fields expanded near AdS{sub 3} x S{sup 3} background and thus the corresponding Kaluza--Klein spectrum. We fix the fermionic and bosonic light-cone gauges in the covariant Green--Schwarz AdS{sub 3} x S{sup 3} superstring action and find the corresponding light-cone string Hamiltonian. We also obtain a realization of the generators of psu(1,1|2)(circle plus)psu (1,1|2) in terms of the superstring 2-d fields in the light-cone gauge.

  6. Blue light-induced retinal lesions, intraretinal vascular leakage and edema formation in the all-cone mouse retina.

    PubMed

    Geiger, P; Barben, M; Grimm, C; Samardzija, M

    2015-11-19

    Little is known about the mechanisms underlying macular degenerations, mainly for the scarcity of adequate experimental models to investigate cone cell death. Recently, we generated R91W;Nrl(-/-) double-mutant mice, which display a well-ordered all-cone retina with normal retinal vasculature and a strong photopic function that generates useful vision. Here we exposed R91W;Nrl(-/-) and wild-type (wt) mice to toxic levels of blue light and analyzed their retinas at different time points post illumination (up to 10 days). While exposure of wt mice resulted in massive pyknosis in a focal region of the outer nuclear layer (ONL), the exposure of R91W;Nrl(-/-) mice led to additional cell death detected within the inner nuclear layer. Microglia/macrophage infiltration at the site of injury was more pronounced in the all-cone retina of R91W;Nrl(-/-) than in wt mice. Similarly, vascular leakage was abundant in the inner and outer retina in R91W;Nrl(-/-) mice, whereas it was mild and restricted to the subretinal space in wt mice. This was accompanied by retinal swelling and the appearance of cystoid spaces in both inner and ONLs of R91W;Nrl(-/-) mice indicating edema in affected areas. In addition, basal expression levels of tight junction protein-1 encoding ZO1 were lower in R91W;Nrl(-/-) than in wt retinas. Collectively, our data suggest that exposure of R91W;Nrl(-/-) mice to blue light not only induces cone cell death but also disrupts the inner blood-retinal barrier. Macular edema in humans is a result of diffuse capillary leakage and microaneurysms in the macular region. Blue light exposure of the R91W;Nrl(-/-) mouse could therefore be used to study molecular events preceding edema formation in a cone-rich environment, and thus potentially help to develop treatment strategies for edema-based complications in macular degenerations.

  7. B{sub (s)}{yields}S transitions in the light cone sum rules with the chiral current

    SciTech Connect

    Sun Yanjun; Li Zuohong; Huang Tao

    2011-01-15

    We make a QCD light-cone sum rule assessment of B{sub (s)} semileptonic decays to a light scalar meson, B{sub (s)}{yields}Sl{nu}{sub l}, Sll(l=e,{mu},{tau}). Chiral current correlators are used and calculations are performed at leading order in {alpha}{sub s}. Having little knowledge of the ingredients of the scalar mesons, we confine ourself to the two-quark picture for them and work with the two possible scenarios. The resulting sum rules for the form factors receive no contributions from the twist-3 distribution amplitudes, in comparison with the calculation of the conventional light-cone sum rule approach where the twist-3 parts usually play an important role. We specify the range of the squared momentum transfer q{sup 2}, in which the operator product expansion for the correlators remains valid approximately. It is found that the form factors satisfy a relation consistent with the prediction of soft collinear effective theory. In the effective range we investigate behaviors of the form factors and differential decay widths and compare our calculations with the observations from other approaches.

  8. Stray light in cone beam optical computed tomography: I. Measurement and reduction strategies with planar diffuse source

    NASA Astrophysics Data System (ADS)

    Granton, Patrick V.; Dekker, Kurtis H.; Battista, Jerry J.; Jordan, Kevin J.

    2016-04-01

    Optical cone-beam computed tomographic (CBCT) scanning of 3D radiochromic dosimeters may provide a practical method for 3D dose verification in radiation therapy. However, in cone-beam geometry stray light contaminates the projection images, degrading the accuracy of reconstructed linear attenuation coefficients. Stray light was measured using a beam pass aperture array (BPA) and structured illumination methods. The stray-to-primary ray ratio (SPR) along the central axis was found to be 0.24 for a 5% gelatin hydrogel, representative of radiochromic hydrogels. The scanner was modified by moving the spectral filter from the detector to the source, changing the light’s spatial fluence pattern and lowering the acceptance angle by extending distance between the source and object. These modifications reduced the SPR significantly from 0.24 to 0.06. The accuracy of the reconstructed linear attenuation coefficients for uniform carbon black liquids was compared to independent spectrometer measurements. Reducing the stray light increased the range of accurate transmission readings. In order to evaluate scanner performance for the more challenging application to small field dosimetry, a carbon black finger gel phantom was prepared. Reconstructions of the phantom from CBCT and fan-beam CT scans were compared. The modified source resulted in improved agreement. Subtraction of residual stray light, measured with BPA or structured illumination from each projection further improved agreement. Structured illumination was superior to BPA for measuring stray light for the smaller 1.2 and 0.5 cm diameter phantom fingers. At the costs of doubling the scanner size and tripling the number of scans, CBCT reconstructions of low-scattering hydrogel dosimeters agreed with those of fan-beam CT scans.

  9. Pigment epithelium-derived factor protects cone photoreceptor-derived 661W cells from light damage through Akt activation.

    PubMed

    Rapp, Matthew; Woo, Grace; Al-Ubaidi, Muayyad R; Becerra, S Patricia; Subramanian, Preeti

    2014-01-01

    Pigment epithelium-derived factor (PEDF) can delay and prevent the death of photoreceptors in vivo. We investigated the survival activity of PEDF on cone photoreceptor-derived 661W cells in culture, the presence of PEDF receptor (PEDF-R) in these cells and the activation of prosurvival Akt. Cell death was induced by light exposure in the presence of 9-cis retinal. Cell viability assays showed that PEDF increased the number of 661W cells exposed to these conditions. Western blots showed that PEDF-treated 661W cells had a higher ratio of phosphorylated Akt to total Akt than untreated cells. The PEDF receptor PEDF-R was immunodetected in the plasma membrane fractions of 661W cells. The results demonstrated that PEDF can protect 661W cells against light-induced cell death and suggest that the binding of PEDF to cell surface PEDF-R triggers a prosurvival signaling pathway.

  10. Use of a local cone model to predict essential CSF light adaptation behavior used in the design of luminance quantization nonlinearities

    NASA Astrophysics Data System (ADS)

    Daly, Scott; Golestaneh, S. A.

    2015-03-01

    The human visual system's luminance nonlinearity ranges continuously from square root behavior in the very dark, gamma-like behavior in dim ambient, cube-root in office lighting, and logarithmic for daylight ranges. Early display quantization nonlinearities have been developed based on luminance bipartite JND data. More advanced approaches considered spatial frequency behavior, and used the Barten light-adaptive Contrast Sensitivity Function (CSF) modelled across a range of light adaptation to determine the luminance nonlinearity (e.g., DICOM, referred to as a GSDF {grayscale display function}). A recent approach for a GSDF, also referred to as an electrical-to-optical transfer function (EOTF), using that light-adaptive CSF model improves on this by tracking the CSF for the most sensitive spatial frequency, which changes with adaptation level. We explored the cone photoreceptor's contribution to the behavior of this maximum sensitivity of the CSF as a function of light adaptation, despite the CSF's frequency variations and that the cone's nonlinearity is a point-process. We found that parameters of a local cone model could fit the max sensitivity of the CSF model, across all frequencies, and are within the ranges of parameters commonly accepted for psychophysicallytuned cone models. Thus, a linking of the spatial frequency and luminance dimensions has been made for a key neural component. This provides a better theoretical foundation for the recently designed visual signal format using the aforementioned EOTF.

  11. The leading twist light-cone distribution amplitudes for the S-wave and P-wave Bc mesons

    NASA Astrophysics Data System (ADS)

    Xu, Ji; Yang, Deshan

    2016-07-01

    The light-cone distribution amplitudes (LCDAs) serve as important nonperturbative inputs for the study of hard exclusive processes. In this paper, we calculate ten LCDAs at twist-2 for the S-wave and P-wave B c mesons up to the next-to-leading order (NLO) of the strong coupling α s and leading order of the velocity expansion. Each one of these ten LCDAs is expressed as a product of a perturbatively calculable distribution and a universal NRQCD matrix-element. By use of the spin symmetry, only two NRQCD matrix-elements will be involved. The reduction of the number of non-perturbative inputs will improve the predictive power of collinear factorization.

  12. Reconsideration of the B →K* transition form factors within the QCD light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Cheng, Wei; Wu, Xing-Gang; Fu, Hai-Bing

    2017-05-01

    In this paper, we study the B →K* transition form factors (TFFs) within the QCD light-cone sum rules (LCSR) approach. Two correlators, i.e., the usual one and the right-handed one, are adopted in the LCSR calculation. The resultant LCSRs for the B →K* TFFs are arranged according to the twist structure of the K*-meson light-cone distribution amplitudes (LCDAs), whose twist-2, twist-3, and twist-4 terms behave quite differently by using different correlators. We observe that the twist-4 LCDAs, though generally small, shall have sizable contributions to the TFFs A1 /2, V , and T1; thus, the twist-4 terms should be kept for a sound prediction. We also observe that, even though different choices of the correlator lead to different LCSRs with different twist contributions, the large correlation coefficients for most of the TFFs indicate that the LCSRs for different correlators are close to each order, not only for their values at the large recoil point q2=0 but also for their ascending trends in the whole q2 region. Such a high degree of correlation is confirmed by their application to the branching fraction of the semileptonic decay B →K*μ+μ- . Thus, a proper choice of correlator may inversely provide a chance for probing uncertain LCDAs; i.e., the contributions from those LCDAs can be amplified to a certain degree via a proper choice of correlator, thus amplifying the sensitivity of the TFFs and, hence, their related observables, to those LCDAs.

  13. The MICE Grand Challenge light-cone simulation - III. Galaxy lensing mocks from all-sky lensing maps

    NASA Astrophysics Data System (ADS)

    Fosalba, P.; Gaztañaga, E.; Castander, F. J.; Crocce, M.

    2015-02-01

    In Paper I of this series, we presented a new N-body light-cone simulation from the MICE Collaboration, the MICE Grand Challenge (MICE-GC), containing about 70 billion dark-matter particles in a (3 h-1 Gpc)3 comoving volume, from which we built halo and galaxy catalogues using a Halo Occupation Distribution and Halo Abundance Matching technique, as presented in the companion Paper II. Given its large volume and fine mass resolution, the MICE-GC simulation also allows an accurate modelling of the lensing observables from upcoming wide and deep galaxy surveys. In the last paper of this series (Paper III), we describe the construction of all-sky lensing maps, following the `Onion Universe' approach, and discuss their properties in the light-cone up to z = 1.4 with sub-arcminute spatial resolution. By comparing the convergence power spectrum in the MICE-GC to lower mass-resolution (i.e. particle mass ˜1011 h-1 M⊙) simulations, we find that resolution effects are at the 5 per cent level for multipoles ℓ ˜ 103 and 20 per cent for ℓ ˜ 104. Resolution effects have a much lower impact on our simulation, as shown by comparing the MICE-GC to recent numerical fits by Takahashi. We use the all-sky lensing maps to model galaxy lensing properties, such as the convergence, shear, and lensed magnitudes and positions, and validate them thoroughly using galaxy shear auto and cross-correlations in harmonic and configuration space. Our results show that the galaxy lensing mocks here presented can be used to accurately model lensing observables down to arcminute scales. Accompanying this series of papers, we make a first public data release of the MICE-GC galaxy mock, the MICECAT v1.0, through a dedicated web-portal for the MICE simulations, http://cosmohub.pic.es, to help developing and exploiting the new generation of astronomical surveys.

  14. Relative contributions of rod and cone bipolar cell inputs to AII amacrine cell light responses in the mouse retina

    PubMed Central

    Pang, Ji-Jie; Abd-El-Barr, Muhammad M; Gao, Fan; Bramblett, Debra E; Paul, David L; Wu, Samuel M

    2007-01-01

    AII amacrine cells (AIIACs) are crucial relay stations for rod-mediated signals in the mammalian retina and they receive synaptic inputs from depolarizing and hyperpolarizing bipolar cells (DBCs and HBCs) as well as from other amacrine cells. Using whole-cell voltage-clamp technique in conjunction with pharmacological tools, we found that the light-evoked current response of AIIACs in the mouse retina is almost completely mediated by two DBC synaptic inputs: a 6,7-dinitro-quinoxaline-2,3-dione (DNQX)-resistant component mediated by cone DBCs (DBCCs) through an electrical synapse, and a DNQX-sensitive component mediated by rod DBCs (DBCRs). This scheme is supported by AIIAC current responses recorded from two knockout mice. The dynamic range of the AIIAC light response in the Bhlhb4−/− mouse (which lacks DBCRs) resembles that of the DNQX-resistant component, and that of the connexin36 (Cx36)−/− mouse resembles the DNQX-sensitive component. By comparing the light responses of the DBCCs with the DNQX-resistant AIIAC component, and light responses of the DBCRs with the DNQX-sensitive AIIAC component, we obtained the input–output relations of the DBCC→AIIAC electrical synapse and the DBCR→AIIAC chemical synapse. Similar to other glutamatergic chemical synapses in the retina, the DBCR→AIIAC synapse is non-linear. Its highest voltage gain (approximately 5) is found near the dark membrane potential, and it saturates for presynaptic signals larger than 5.5 mV. The DBCC→AIIAC electrical synapse is approximately linear (voltage gain of 0.92), consistent with the linear junctional conductance found in retinal electrical synapses. Moreover, relative DBCR and DBCC contributions to the AIIAC response at various light intensity levels are determined. PMID:17255172

  15. Relative contributions of rod and cone bipolar cell inputs to AII amacrine cell light responses in the mouse retina.

    PubMed

    Pang, Ji-Jie; Abd-El-Barr, Muhammad M; Gao, Fan; Bramblett, Debra E; Paul, David L; Wu, Samuel M

    2007-04-15

    AII amacrine cells (AIIACs) are crucial relay stations for rod-mediated signals in the mammalian retina and they receive synaptic inputs from depolarizing and hyperpolarizing bipolar cells (DBCs and HBCs) as well as from other amacrine cells. Using whole-cell voltage-clamp technique in conjunction with pharmacological tools, we found that the light-evoked current response of AIIACs in the mouse retina is almost completely mediated by two DBC synaptic inputs: a 6,7-dinitro-quinoxaline-2,3-dione (DNQX)-resistant component mediated by cone DBCs (DBC(C)s) through an electrical synapse, and a DNQX-sensitive component mediated by rod DBCs (DBC(R)s). This scheme is supported by AIIAC current responses recorded from two knockout mice. The dynamic range of the AIIAC light response in the Bhlhb4-/- mouse (which lacks DBC(R)s) resembles that of the DNQX-resistant component, and that of the connexin36 (Cx36)-/- mouse resembles the DNQX-sensitive component. By comparing the light responses of the DBC(C)s with the DNQX-resistant AIIAC component, and light responses of the DBC(R)s with the DNQX-sensitive AIIAC component, we obtained the input-output relations of the DBC(C)-->AIIAC electrical synapse and the DBC(R)-->AIIAC chemical synapse. Similar to other glutamatergic chemical synapses in the retina, the DBC(R)-->AIIAC synapse is non-linear. Its highest voltage gain (approximately 5) is found near the dark membrane potential, and it saturates for presynaptic signals larger than 5.5 mV. The DBC(C)-->AIIAC electrical synapse is approximately linear (voltage gain of 0.92), consistent with the linear junctional conductance found in retinal electrical synapses. Moreover, relative DBC(R) and DBC(C) contributions to the AIIAC response at various light intensity levels are determined.

  16. Delayed loss of cone and remaining rod photoreceptor cells due to impairment of choroidal circulation after acute light exposure in rats.

    PubMed

    Tanito, Masaki; Kaidzu, Sachiko; Anderson, Robert E

    2007-04-01

    To examine the long-term effects of acute photooxidative stress in the retina, retinal pigment epithelium (RPE), and choroid. Albino rats injected with either the protective antioxidant phenyl-N-tert-butylnitrone (PBN) or saline 30 minutes before exposure to 5 klx white fluorescent light for 6 hours were kept for up to 3 months in 5 lux cyclic light. Electroretinograms were recorded, and the outer nuclear layer (ONL) and the choroidal thickness and area were measured after hematoxylin-eosin (H&E) staining. The expression of rod, cone, and RPE cell markers was detected by Western blotting, and apoptosis was analyzed by TUNEL staining. Oxidative stress was analyzed by immunohistochemistry against 4-hydroxynonenal (4-HNE)-modified proteins. Retinal and choroidal ultrastructures were observed by transmission electron microscopy (TEM). Choroidal circulation was analyzed by in vivo staining of the choroidal layer by trypan blue. In the saline-injected animals, TUNEL- and 4-HNE-labeling in the ONL, RPE, and choroid were higher 24 hours and 7 days after light exposure, and ERG amplitude, ONL and choroidal thickness and area, and rhodopsin and RPE65 expression were lower 7 or more days after light exposure than in phenyl-N-tert-butylnitrone (PBN)-injected animals. In the saline-injected animals, the expression of mid-wavelength opsin and the presence of cone cells in the ONL and the choroidal circulation were preserved for 7 days after light exposure but started to decrease by 1 month and continued to decrease for 3 months after light exposure. An increase in TUNEL-positive cells was observed in the ONL at the inferior peripheral retina, just behind the iris, by 3 months after light exposure. Delayed loss of cone cells, remaining rod cells, and choroidal circulation were counteracted by PBN treatment. Although cone cells are resistant to cell damage induced by acute photooxidative stress, progressive loss of cone cells continued for up to 3 months after light exposure

  17. Exploring the evolution of reionization using a wavelet transform and the light cone effect

    NASA Astrophysics Data System (ADS)

    Trott, Cathryn M.

    2016-09-01

    The Cosmic Dawn and Epoch of Reionization, during which collapsed structures produce the first ionizing photons and proceed to reionize the intergalactic medium, span a large range in redshift (z ˜ 30-6) and time (tage ˜ 0.1-1.0 Gyr). Exploration of these epochs using the redshifted 21 cm emission line from neutral hydrogen is currently limited to statistical detection and estimation metrics (e.g. the power spectrum) due to the weakness of the signal. Brightness temperature fluctuations in the line-of-sight dimension are probed by observing the emission line at different frequencies, and their structure is used as a primary discriminant between the cosmological signal and contaminating foreground extragalactic and Galactic continuum emission. Evolution of the signal over the observing bandwidth leads to the `line cone effect' whereby the H I structures at the start and end of the observing band are not statistically consistent, yielding a biased estimate of the signal power, and potential reduction in signal detectability. We implement a wavelet transform to wide bandwidth radio interferometry experiments to probe the local statistical properties of the signal. We show that use of the wavelet transform yields estimates with improved estimation performance, compared with the standard Fourier Transform over a fixed bandwidth. With the suite of current and future large bandwidth reionization experiments, such as with the 300 MHz instantaneous bandwidth of the Square Kilometre Array, a transform that retains local information will be important.

  18. Nano-cones for broadband light coupling to high index substrates

    PubMed Central

    Buencuerpo, J.; Torné, L.; Álvaro, R.; Llorens, J. M.; Dotor, M. L.; Ripalda, J. M.

    2016-01-01

    The moth-eye structure has been proposed several times as an antireflective coating to replace the standard optical thin films. Here, we experimentally demonstrate the feasibility of a dielectric moth-eye structure as an antireflective coating for high-index substrates, like GaAs. The fabricated photonic crystal has Si3N4 cones in a square lattice, sitting on top of a TiO2 index matching layer. This structure attains 1.4% of reflectance power losses in the operation spectral range of GaAs solar cells (440–870 nm), a 12.5% relative reduction of reflection power losses in comparison with a standard bilayer. The work presented here considers a fabrication process based on laser interference lithography and dry etching, which are compatible with solar cell devices. The experimental results are consistent with scattering matrix simulations of the fabricated structures. In a broader spectral range (400–1800 nm), the simulation estimates that the nanostructure also significantly outperforms the standard bilayer coating (3.1% vs. 4.5% reflection losses), a result of interest for multijunction tandem solar cells. PMID:27924859

  19. Nano-cones for broadband light coupling to high index substrates

    NASA Astrophysics Data System (ADS)

    Buencuerpo, J.; Torné, L.; Álvaro, R.; Llorens, J. M.; Dotor, M. L.; Ripalda, J. M.

    2016-12-01

    The moth-eye structure has been proposed several times as an antireflective coating to replace the standard optical thin films. Here, we experimentally demonstrate the feasibility of a dielectric moth-eye structure as an antireflective coating for high-index substrates, like GaAs. The fabricated photonic crystal has Si3N4 cones in a square lattice, sitting on top of a TiO2 index matching layer. This structure attains 1.4% of reflectance power losses in the operation spectral range of GaAs solar cells (440–870 nm), a 12.5% relative reduction of reflection power losses in comparison with a standard bilayer. The work presented here considers a fabrication process based on laser interference lithography and dry etching, which are compatible with solar cell devices. The experimental results are consistent with scattering matrix simulations of the fabricated structures. In a broader spectral range (400–1800 nm), the simulation estimates that the nanostructure also significantly outperforms the standard bilayer coating (3.1% vs. 4.5% reflection losses), a result of interest for multijunction tandem solar cells.

  20. A Unitary and Renormalizable Theory of the Standard Model in Ghost-Free Light-Cone Gauge

    SciTech Connect

    Brodsky, Stanley J.

    2002-02-15

    Light-front (LF) quantization in light-cone (LC) gauge is used to construct a unitary and simultaneously renormalizable theory of the Standard Model. The framework derived earlier for QCD is extended to the Glashow, Weinberg, and Salam (GWS) model of electroweak interaction theory. The Lorentz condition is automatically satisfied in LF-quantized QCD in the LC gauge for the free massless gauge field. In the GWS model, with the spontaneous symmetry breaking present, we find that the 't Hooft condition accompanies the LC gauge condition corresponding to the massive vector boson. The two transverse polarization vectors for the massive vector boson may be chosen to be the same as found in QCD. The non-transverse and linearly independent third polarization vector is found to be parallel to the gauge direction. The corresponding sum over polarizations in the Standard model, indicated by K{sub {mu}{nu}}(k); has several simplifying properties similar to the polarization sum D{sub {mu}{nu}}(k) in QCD. The framework is ghost-free, and the interaction Hamiltonian of electroweak theory can be expressed in a form resembling that of covariant theory, except for few additional instantaneous interactions which can be treated systematically. The LF formulation also provides a transparent discussion of the Goldstone Boson (or Electroweak) Equivalence Theorem, as the illustrations show.

  1. Observation of trapped light induced by Dwarf Dirac-cone in out-of-plane condition for photonic crystals

    NASA Astrophysics Data System (ADS)

    Majumder, Subir; Biswas, Tushar; Bhadra, Shaymal K.

    2016-10-01

    Existence of out-of-plane conical dispersion for a triangular photonic crystal lattice is reported. It is observed that conical dispersion is maintained for a number of out-of-plane wave vectors (k z ). We study a case where Dirac like linear dispersion exists but the photonic density of states is not vanishing, called Dwarf Dirac cone (DDC) which does not support localized modes. We demonstrate the trapping of such modes by introducing defects in the crystal. Interestingly, we find by k-point sampling as well as by tuning trapped frequency that such a conical dispersion has an inherent light confining property and it is governed by neither of the known wave confining mechanisms like total internal reflection, band gap guidance. Our study reveals that such a conical dispersion in a non-vanishing photonic density of states induces unexpected intense trapping of light compared with those at other points in the continuum. Such studies provoke fabrication of new devices with exciting properties and new functionalities. Project supported by Director, CSIR-CGCRI, the DST, Government of India, and the CSIR 12th Plan Project (GLASSFIB), India.

  2. Design of an optical proximity sensor using multiple cones of light for measuring surface shape

    NASA Astrophysics Data System (ADS)

    Fuhrman, M.; Kanade, T.

    1984-04-01

    A noncontact multi-light source optical proximity sensor which can measure the distance, orientation, and curvature of a surface has been developed. Beams of light are sequentially focused from the ends of fiber optic cables onto a target surface. An analog light-sensor- a planar PIN diode area sensor chip - measures the position of the spots of light on the surface, and the 3-D locations of the spots are computed by triangulation. By fitting a surface to a set of points, the distance, orientation and curvature of the target surface is calculated. The number of light sources, and their positions and orientations were chosen so that the uncertainty in the measurement of distance would be within 0.05 mm and the uncertainty in surface orientation would be within 1.0 deg. Since there are no moving parts and the spot position sensor chip outputs the position of the spot directly without scanning its field of view, fast operation of the proximity sensor can be realized. Earlier prototype versions of the sensor can give approximately 1000 measurements of distance and 1.5 degrees for surface orientation. This proximity sensor will be useful for such applications as tracing an object surface by a robot manipulator with a specified distance and orientation relative to the surface.

  3. Optical Proximity Sensor Using Multiple Cones Of Light For Measuring Surface Shape

    NASA Astrophysics Data System (ADS)

    Fuhrman, Michael; Kanade, Takeo

    1984-10-01

    A noncontact multilight source optical proximity sensor that can measure the distance, orientation, and curvature of a surface has been developed. Beams of light are sequentially focused from the ends of fiber optic cables onto a target surface. An analog light sensor a planar pin diode area sensor chip measures the position of the spots of light on the surface, and the 3-D locations of the spots are computed by triangulation. By fitting a surface to a set of points, the distance, orientation, and curvature of the target surface are calculated. The number of light sources and their positions and orientations were chosen so that the uncertainty in the measurement of distance would be within 0.05 mm and the uncertainty in surface orientation would be within 1.0 °. Since there are no moving parts and the spot position sensor chip outputs the position of the spot directly without scanning its field of view, fast opera-tion of the proximity sensor can be realized. Earlier prototype versions of the sensor can give approximately 1000 measurements of distance and orientation per second with precision of 0.07 mm for distance and 1.5 ° for surface orientation. This proximity sensor will be useful for such applications as tracing an object surface by a robot manipulator with a specified distance and orientation relative to the surface.

  4. Investigating strangeness in the proton by studying the effects of Light Cone parton distributions in the Meson Cloud Model

    NASA Astrophysics Data System (ADS)

    Tuppan, Sam; Budnik, Garrett; Fox, Jordan

    2014-09-01

    The Meson Cloud Model (MCM) has proven to be a natural explanation for strangeness in the proton because of meson-baryon splitting into kaon-hyperon pairs. Total strangeness is predicted by integrated splitting functions, which represent the probability that the proton will fluctuate into a given meson-baryon pair. However, the momentum distributions s (x) and s (x) in the proton are determined from convolution integrals that depend on the parton distribution functions (PDFs) used for the mesons and baryons in the MCM. Theoretical calculations of these momentum distributions use many different forms for these PDFs. In our investigation, we calculate PDFs for K, K*, Λ, and Σ from two-body wave functions in a Light Cone Model (LCM) of the hadrons. We use these PDFs in conjunction with the MCM to create a hybrid model and compare our results to other theoretical calculations, experimental data from NuTeV, HERMES, ATLAS, and global parton distribution analyses. The Meson Cloud Model (MCM) has proven to be a natural explanation for strangeness in the proton because of meson-baryon splitting into kaon-hyperon pairs. Total strangeness is predicted by integrated splitting functions, which represent the probability that the proton will fluctuate into a given meson-baryon pair. However, the momentum distributions s (x) and s (x) in the proton are determined from convolution integrals that depend on the parton distribution functions (PDFs) used for the mesons and baryons in the MCM. Theoretical calculations of these momentum distributions use many different forms for these PDFs. In our investigation, we calculate PDFs for K, K*, Λ, and Σ from two-body wave functions in a Light Cone Model (LCM) of the hadrons. We use these PDFs in conjunction with the MCM to create a hybrid model and compare our results to other theoretical calculations, experimental data from NuTeV, HERMES, ATLAS, and global parton distribution analyses. This research has been supported in part by the

  5. A novel in vivo model of focal light emitting diode-induced cone-photoreceptor phototoxicity: neuroprotection afforded by brimonidine, BDNF, PEDF or bFGF.

    PubMed

    Ortín-Martínez, Arturo; Valiente-Soriano, Francisco Javier; García-Ayuso, Diego; Alarcón-Martínez, Luis; Jiménez-López, Manuel; Bernal-Garro, José Manuel; Nieto-López, Leticia; Nadal-Nicolás, Francisco Manuel; Villegas-Pérez, María Paz; Wheeler, Larry A; Vidal-Sanz, Manuel

    2014-01-01

    We have investigated the effects of light-emitting diode (LED)-induced phototoxicity (LIP) on cone-photoreceptors and their protection with brimonidine (BMD), brain-derived neurotrophic factor (BDNF), pigment epithelium-derived factor (PEDF), ciliary neurotrophic factor (CNTF) or basic fibroblast growth factor (bFGF). In anesthetized, dark adapted, adult albino rats a blue (400 nm) LED was placed perpendicular to the cornea (10 sec, 200 lux) and the effects were investigated using Spectral Domain Optical Coherence Tomography (SD-OCT) and/or analysing the retina in oriented cross-sections or wholemounts immune-labelled for L- and S-opsin and counterstained with the nuclear stain DAPI. The effects of topical BMD (1%) or, intravitreally injected BDNF (5 µg), PEDF (2 µg), CNTF (0.4 µg) or bFGF (1 µg) after LIP were examined on wholemounts at 7 days. SD-OCT showed damage in a circular region of the superotemporal retina, whose diameter varied from 1,842.4±84.5 µm (at 24 hours) to 1,407.7±52.8 µm (at 7 days). This region had a progressive thickness diminution from 183.4±5 µm (at 12 h) to 114.6±6 µm (at 7 d). Oriented cross-sections showed within the light-damaged region of the retina massive loss of rods and cone-photoreceptors. Wholemounts documented a circular region containing lower numbers of L- and S-cones. Within a circular area (1 mm or 1.3 mm radius, respectively) in the left and in its corresponding region of the contralateral-fellow-retina, total L- or S-cones were 7,118±842 or 661±125 for the LED exposed retinas (n = 7) and 14,040±1,860 or 2,255±193 for the fellow retinas (n = 7), respectively. BMD, BDNF, PEDF and bFGF but not CNTF showed significant neuroprotective effects on L- or S-cones. We conclude that LIP results in rod and cone-photoreceptor loss, and is a reliable, quantifiable model to study cone-photoreceptor degeneration. Intravitreal BDNF, PEDF or bFGF, or topical BMD afford significant cone neuroprotection in this model.

  6. A Novel In Vivo Model of Focal Light Emitting Diode-Induced Cone-Photoreceptor Phototoxicity: Neuroprotection Afforded by Brimonidine, BDNF, PEDF or bFGF

    PubMed Central

    García-Ayuso, Diego; Alarcón-Martínez, Luis; Jiménez-López, Manuel; Bernal-Garro, José Manuel; Nieto-López, Leticia; Nadal-Nicolás, Francisco Manuel; Villegas-Pérez, María Paz; Wheeler, Larry A.; Vidal-Sanz, Manuel

    2014-01-01

    We have investigated the effects of light-emitting diode (LED)-induced phototoxicity (LIP) on cone-photoreceptors and their protection with brimonidine (BMD), brain-derived neurotrophic factor (BDNF), pigment epithelium-derived factor (PEDF), ciliary neurotrophic factor (CNTF) or basic fibroblast growth factor (bFGF). In anesthetized, dark adapted, adult albino rats a blue (400 nm) LED was placed perpendicular to the cornea (10 sec, 200 lux) and the effects were investigated using Spectral Domain Optical Coherence Tomography (SD-OCT) and/or analysing the retina in oriented cross-sections or wholemounts immune-labelled for L- and S-opsin and counterstained with the nuclear stain DAPI. The effects of topical BMD (1%) or, intravitreally injected BDNF (5 µg), PEDF (2 µg), CNTF (0.4 µg) or bFGF (1 µg) after LIP were examined on wholemounts at 7 days. SD-OCT showed damage in a circular region of the superotemporal retina, whose diameter varied from 1,842.4±84.5 µm (at 24 hours) to 1,407.7±52.8 µm (at 7 days). This region had a progressive thickness diminution from 183.4±5 µm (at 12 h) to 114.6±6 µm (at 7 d). Oriented cross-sections showed within the light-damaged region of the retina massive loss of rods and cone-photoreceptors. Wholemounts documented a circular region containing lower numbers of L- and S-cones. Within a circular area (1 mm or 1.3 mm radius, respectively) in the left and in its corresponding region of the contralateral-fellow-retina, total L- or S-cones were 7,118±842 or 661±125 for the LED exposed retinas (n = 7) and 14,040±1,860 or 2,255±193 for the fellow retinas (n = 7), respectively. BMD, BDNF, PEDF and bFGF but not CNTF showed significant neuroprotective effects on L- or S-cones. We conclude that LIP results in rod and cone-photoreceptor loss, and is a reliable, quantifiable model to study cone-photoreceptor degeneration. Intravitreal BDNF, PEDF or bFGF, or topical BMD afford significant cone neuroprotection in this model

  7. The color cone.

    PubMed

    Logvinenko, Alexander D

    2015-02-01

    While the notion of a color cone can be found in writings of Maxwell, Helmholtz, Grassmann, and other scientists of the nineteenth century, it has not been clearly defined as yet. In this paper, the color cone is understood as the set of points in the cone excitation space produced by all possible lights. The spectral curve representing all the monochromatic lights is shown not to entirely belong to the color cone boundary, since its ends turn into the color cone interior. The monochromatic lights represented by the fragment of the spectral curve lying on the color cone boundary make up what is called the effective visible spectrum. The color cone is shown to be a convex hull of the conical surface through the fragment of the spectral curve representing the effective visible spectrum. The effective visible spectrum ends are shown to be determined by the photopigment spectral absorbance being independent of the prereceptor filters (e.g., the spectral transmittance of the lense and macular pigment).

  8. Exclusive C=+ charmonium production in e{sup +}e{sup -{yields}}H+{gamma} at B factories within the light cone formalism

    SciTech Connect

    Braguta, V. V.

    2010-10-01

    In this paper the cross sections of the processes e{sup +}e{sup -{yields}}H+{gamma}, H={eta}{sub c}, {eta}{sub c}{sup '}, {chi}{sub c0}, {chi}{sub c1}, {chi}{sub c2} are calculated. The calculation is carried out at the leading twist approximation of the light cone formalism. Within this approach the leading logarithmic radiative and relativistic corrections to the amplitudes are resummed. For the processes e{sup +}e{sup -{yields}{eta}}{sub c}, {eta}{sub c}{sup '}+{gamma} one-loop radiative corrections are taken into account. It is also shown that one-loop leading logarithmic radiative corrections calculated within the light cone formalism for the processes under study coincide with that obtained by direct calculations of one-loop diagrams within nonrelativistic QCD.

  9. Lensing in the geodesic light-cone coordinates and its (exact) illustration to an off-center observer in Lemaȋtre-Tolman-Bondi models

    SciTech Connect

    Fanizza, G.; Nugier, F. E-mail: fabienjean.nugier@unibo.it

    2015-02-01

    We present in this paper a new application of the geodesic light-cone (GLC) gauge for weak lensing calculations. Using interesting properties of this gauge, we derive an exact expression of the amplification matrix—involving convergence, magnification and shear—and of the deformation matrix—involving the optical scalars. These expressions are simple and non-perturbative as long as no caustics are created on the past light-cone and are, by construction, free from the thin lens approximation. We apply these general expressions on the example of an Lemaȋtre-Tolman-Bondi (LTB) model with an off-center observer and obtain explicit forms for the lensing quantities as a direct consequence of the non-perturbative transformation between GLC and LTB coordinates. We show their evolution in redshift after a numerical integration, for underdense and overdense LTB models, and interpret their respective variations in the simple non-curvature case.

  10. Cold knife cone biopsy

    MedlinePlus

    ... biopsy; Pap smear - cone biopsy; HPV - cone biopsy; Human papilloma virus - cone biopsy; Cervix - cone biopsy; Colposcopy - cone biopsy Images Female reproductive anatomy Cold cone biopsy Cold cone removal References American ...

  11. Massive Degeneracy and Goldstone Bosons: A Challenge for the Light Cone

    SciTech Connect

    Weinstein, Marvin; /SLAC

    2010-10-27

    Wherein it is argued that the light front formalism has problems dealing with Goldstone symmetries. It is further argued that the notion that in hadron condensates can explain Goldstone phenomena is false. This talk can be summarized as follows: (1) Exact symmetries can be realized in Wigner or Goldstone mode. (2) When a symmetry is realized in Wigner mode the states of the theory form degenerate irreducible representations of the symmetry group and the lowest energy state is unique. (3) When a symmetry is realized in Goldstone mode the lowest energy state of the theory is infinitely degenerate, the states of the theory do not form irreducible representations of the symmetry group and there are massless particles coupled by the conserved currents to any one of the possible ground states. (4) In finite volume the signal of a Goldstone realization of a symmetry is that the number of nearly degenerate states grows rapidly with increasing volume and the gap between these states shrinks exponentially with the volume. (5) The existence of a condensate such as the magnetization, for a ferromagnet, or the staggered magnetization for an anti-ferromagnet, signals a Goldstone symmetry. This is because this condensate transforms non-trivially under the symmetry transformations and so its existence implies the ground state isn't unique. (6) PCAC means that the pion, kaon and eta are would be Goldstone bosons of the theory where the quark masses are set to zero. This interpretation is overwhelmingly supported by experimental data. This means that these particles are really the wiggling of the order parameter or condensate. (7) Finally, in order for the Goldstone particle to exist there has to be something to wiggle every place where the particle can exist. This means that the condensate that is the order parameter for this Goldstone symmetry cannot be confined to the interior of hadrons. Thus, to reiterate, the challenge for the Light Front is to show how the formalism gives

  12. Dopamine Regulation of GABAA Receptors Contributes to Light/Dark Modulation of the ON-Cone Bipolar Cell Receptive Field Surround in the Retina.

    PubMed

    Chaffiol, Antoine; Ishii, Masaaki; Cao, Yu; Mangel, Stuart C

    2017-09-11

    Cone bipolar cells are interneurons that receive synaptic input from cone photoreceptor cells and provide the output of the first synaptic layer of the retina. These cells exhibit center-surround receptive fields, a prototype of lateral inhibition between neighboring sensory cells in which stimulation of the receptive field center excites the cell whereas stimulation of the surrounding region laterally inhibits the cell. This fundamental sensory coding mechanism facilitates spatial discrimination and detection of stimulus edges. However, although it is well established that the receptive field surround is strongest when ambient or background illumination is most intense, e.g., at midday, and that the surround is minimal following maintained darkness, the synaptic mechanisms that produce and modulate the surround have not been resolved. Using electrical recording of bipolar cells under experimental conditions in which the cells exhibited surround light responses, and light and electron microscopic immunocytochemistry, we show in the rabbit retina that bright-light-induced activation of dopamine D1 receptors located on ON-center cone bipolar cell dendrites increases the expression and activity of GABAA receptors on the dendrites of the cells and that surround light responses depend on endogenous GABAA receptor activation. We also show that maintained darkness and D1 receptor blockade following maintained illumination and D1 receptor activation result in minimal GABAA receptor expression and activity and greatly diminished surrounds. Modulation of the D1/GABAA receptor signaling pathway of ON-cBC dendrites by the ambient light level facilitates detection of spatial details on bright days and large dim objects on moonless nights. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Mimicking acceleration in the constant-bang-time Lemaître-Tolman model: Shell crossings, density distributions, and light cones

    NASA Astrophysics Data System (ADS)

    Krasiński, Andrzej

    2014-09-01

    The Lemaître-Tolman model with Λ=0 and constant bang time that imitates the luminosity distance-redshift relation of the ΛCDM model using the energy function E alone contains shell crossings. In this paper, the location in spacetime and the consequences of existence of the shell-crossing set (SCS) are investigated. The SCS would come into view of the central observer only at t ≈1064T to the future from now, where T is the present age of the Universe, but would not leave any recognizable trace in her observations. Light rays emitted near to the SCS are blueshifted at the initial points, but the blueshift is finite, and is overcompensated by later-induced redshifts if the observer is sufficiently far. The local blueshifts cause that z along a light ray is not a monotonic function of the comoving radial coordinate r. As a consequence, the angular diameter distance DA and the luminosity distance DL from the central observer fail to be functions of z; the relations DA(z) and DL(z) are multiple-valued in a vicinity of the SCS. The following quantities are calculated and displayed: (1) The distribution of mass density on a few characteristic hypersurfaces of constant time; some of them intersect the SCS. (2) The distribution of density along the past light cone of the present central observer. (3) A few light cones intersecting the SCS at characteristic instants. (4) The redshift profiles along several light cones. (5) The extremum-redshift hypersurface. (6) The DA(z) and DL(z) relations. (7) The last scattering time and its comparison with the ΛCDM last scattering epoch.

  14. Study of D →a0(980 )e+νe decay in the light-cone sum rules approach

    NASA Astrophysics Data System (ADS)

    Cheng, Xiao-Dong; Li, Hai-Bo; Wei, Bin; Xu, Yu-Guo; Yang, Mao-Zhi

    2017-08-01

    Within the QCD light-cone sum rule (LCSR) approach, we investigate the transition form factors of D →a0(980 ) up to the twist-3 light-cone distribution amplitudes (LCDAs) of the scalar meson a0(980 ) in the two-quark picture. Using these form factors, we calculate the differential decay widths and branching ratios of the D →a0(980 )e+νe semileptonic decays. We obtain B (D0→a0-(980 )e+νe)=(4.0 8-1.22+1.37)×10-4 and B (D+→a00(980 )e+νe)=(5.4 0-1.59+1.78)×10-4 . The results are sensitive to the a0(980 ) inner structure. These decays can be searched for at the BESIII experiment, and any experimental observations will be useful to identify internal quark contents of the a0(980 ) meson, which will shed light on understanding theoretical models.

  15. g{sub {Sigma}{sub Q{Sigma}{sub Q{pi}}}}coupling constant via light cone QCD sum rules

    SciTech Connect

    Azizi, K.; Bayar, M.; Ozpineci, A.; Sarac, Y.

    2010-10-01

    Using the most general form of the interpolating currents, the coupling constants g{sub {Sigma}{sub b{Sigma}{sub b{pi}}}}and g{sub {Sigma}{sub c{Sigma}{sub c{pi}}}}are calculated within the light cone QCD sum rules approach. It is found that g{sub {Sigma}{sub c{Sigma}{sub c{pi}=}}}-8.0{+-}1.7 and g{sub {Sigma}{sub b{Sigma}{sub b{pi}=}}}-11.0{+-}2.1.

  16. Naive time-reversal odd phenomena in semi-inclusive deep-inelastic scattering from light-cone constituent quark models

    SciTech Connect

    Barbara Pasquini, Peter Schweitzer

    2011-06-01

    We present results for leading-twist azimuthal asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to naively time-reversal odd transverse-momentum dependent parton distribution functions from the light-cone constituent quark model. We carefully discuss the range of applicability of the model, especially with regard to positivity constraints and evolution effects. We find good agreement with available experimental data from COMPASS and HERMES, and present predictions to be tested in forthcoming experiments at Jefferson Lab.

  17. Directional imaging of the retinal cone mosaic.

    PubMed

    Vohnsen, Brian; Iglesias, Ignacio; Artal, Pablo

    2004-05-01

    We describe a near-IR scanning laser ophthalmoscope that allows the retinal cone mosaic to be imaged in the human eye in vivo without the use of wave-front correction techniques. The method takes advantage of the highly directional quality of cone photoreceptors that permits efficient coupling of light to individual cones and subsequent detection of most directional components of the backscattered light produced by the light-guiding effect of the cones. We discuss details of the system and describe cone-mosaic images obtained under different conditions.

  18. Cone Heads

    ERIC Educational Resources Information Center

    Coy, Mary

    2005-01-01

    The author, a middle school art teacher, describes a sculpture project lesson involving Cone Heads (sculptures made from cardboard cones). Discussion of caricatures with exaggerated facial features and interesting profiles helped students understand that the more expressive the face, the better. This project took approximately four to five…

  19. On the problem of mass dependence of the two-point function of the real scalar free massive field on the light cone

    NASA Astrophysics Data System (ADS)

    Ullrich, Peter; Werner, Ernst

    2006-05-01

    We investigate the generally assumed inconsistency in light cone quantum field theory that the restriction of a massive, real scalar free field to the nullplane Σ = {x0 + x3 = 0} is independent of mass (Leutwyler, Klauder and Streit 1970 Nuovo Cimento A 66 536), but the restriction of the two-point function is mass dependent (see, e.g., Nakanishi and Yamawaki 1977 Nucl. Phys. B 122 15; Yamawaki K 1997 Proc. Int. Workshop New Nonperturbative Methods and Quantization on the Light Cone (Les Houches, France) Preprint hep-th/9707141). We resolve this inconsistency by showing that the two-point function has no canonical restriction to Σ in the sense of distribution theory. Only the so-called tame restriction of the two-point function, which we have introduced in (Ullrich P 2004 Uniqueness in the characteristic Cauchy problem of the Klein-Gordon equation and tame restrictions of generalized functions Preprint math-ph/0408022 (submitted)) exists. Furthermore, we show that this tame restriction is indeed independent of the mass. Hence the inconsistency is induced by the erroneous assumption that the two-point function has a (canonical) restriction to Σ.

  20. Polar Cone

    NASA Image and Video Library

    2006-07-10

    This MOC image shows a cone-shaped hill, perhaps a remnant of a material that was once more laterally extensive across the area, on a textured plain in the Hyperboreus Labyrinthus region in the north polar region of Mars

  1. The inhibitor of phagocytosis, O-phospho-L-serine, suppresses Müller glia proliferation and cone cell regeneration in the light-damaged zebrafish retina

    PubMed Central

    Bailey, Travis J.; Fossum, Sara L.; Fimbel, Shane M.; Montgomery, Jacob E.; Hyde, David R.

    2010-01-01

    The damaged zebrafish retina replaces lost neurons through a regenerative response that initiates with the asymmetric cell division of Müller glia to produce neuronal progenitor cells that proliferate and migrate to the damaged retinal layer, where they differentiate into the lost neuronal cell types. Because Müller glia are known to phagocytose apoptotic retinal cells during development, we tested if Müller glia engulfed apoptotic rod cell bodies in light-damaged retinas. After 24 hours of constant intense light, damaged retinas revealed both a strong nuclear TUNEL signal in photoreceptors and a weak cytoplasmic TUNEL signal in Müller glia, although Müller glial apoptosis is not observed in the light-damaged retina. Light damage of a rod-specific transgenic reporter line, Tg(XlRho:EGFP)fl1, resulted in some Müller glia containing both TUNEL signal and EGFP, which indicated that this subset of Müller glia engulfed apoptotic photoreceptor cell bodies. To determine if phagocytosis induced the Müller glial proliferative response in the light-damaged retina, we utilized O-phospho-L-serine (L-SOP), a molecule that mimics the phosphatidylserine head group and partially blocks microglial phagocytosis of apoptotic cells. Intravitreal injection of L-SOP immediately prior to beginning constant intense light treatment: i) did not significantly reduce light-induced photoreceptor cell death, ii) significantly reduced the number of PCNA-positive Müller glia, and iii) significantly reduced the number of cone photoreceptors in the regenerated retina relative to control retinas. Because L-SOP is also a specific group III metabotropic glutamate receptor (mGluR) agonist, we also tested if the more potent specific group III agonist, L-2-amino-4-phosphonobutyrate (L-AP4), the specific group III antagonist (RS)-α-Methylserine-O-phosphate (MSOP) or the specific group I antagonist, L-2-amino-3-phophonopropanoic acid (L-AP3) affected Müller glial proliferation. We found no

  2. Phytochemical and morphological characterization of hop (Humulus lupulus L.) cones over five developmental stages using high performance liquid chromatography coupled to time-of-flight mass spectrometry, ultrahigh performance liquid chromatography photodiode array detection, and light microscopy techniques.

    PubMed

    Kavalier, Adam R; Litt, Amy; Ma, Chunhui; Pitra, Nicholi J; Coles, Mark C; Kennelly, Edward J; Matthews, Paul D

    2011-05-11

    Hop (Humulus lupulus L.) inflorescences, commonly known as "hop cones", are prized for their terpenophenolic contents, used in beer production and, more recently, in biomedical applications. In this study we investigated morphological and phytochemical characteristics of hop cones over five developmental stages, using liquid chromatography coupled to time-of-flight mass spectrometry (LC-TOF-MS), and ultrahigh performance liquid chromatography photodiode array detection (UHPLC-PDA) methods to quantitate 21 polyphenolics and seven terpenophenolics. Additionally, we used light microscopy to correlate phytochemical quantities with changes in the morphology of the cones. Significant increases in terpenophenolics, concomitant with glandular trichome development and associated gross morphological changes, were mapped over development to fluctuations in contents of polyphenolic constituents and their metabolic precursor compounds. The methods reported here can be used for targeted metabolic profiling of flavonoids, phenolic acids, and terpenophenolics in hops, and are applicable to quantitation in other crops.

  3. Effect of light source instability on uniformity of 3D reconstructions from a cone beam optical CT scanner.

    PubMed

    Begg, J; Taylor, M L; Holloway, L; Kron, T; Franich, R D

    2014-12-01

    Temporally varying light intensity during acquisition of projection images in an optical CT scanner can potentially be misinterpreted as physical properties of the sample. This work investigated the impact of LED light source intensity instability on measured attenuation coefficients. Different scenarios were investigated by conducting one or both of the reference and data scans in a 'cold' scanner, where the light source intensity had not yet stabilised. Uniform samples were scanned to assess the impact on measured uniformity. The orange (590 nm) light source decreased in intensity by 29 % over the first 2 h, while the red (633 nm) decreased by 9 %. The rates of change of intensity at 2 h were 0.1 and 0.03 % respectively over a 5 min period-corresponding to the scan duration. The normalisation function of the reconstruction software does not fully account for the intensity differences and discrepancies remain. Attenuation coefficient inaccuracies of up to 8 % were observed for data reconstructed from projection images acquired with a cold scanner. Increased noise was observed for most cases where one or both of the scans was acquired without sufficient warm-up. The decrease in accuracy and increase in noise were most apparent for data reconstructed from reference and data scans acquired with a cold scanner on different days.

  4. Pion-photon transition form factor using light-cone sum rules: theoretical results, expectations, and a global-data fit

    NASA Astrophysics Data System (ADS)

    Bakulev, A. P.; Mikhailov, S. V.; Pimikov, A. V.; Stefanis, N. G.

    2011-10-01

    A global fit to the data from different collaborations (CELLO, CLEO, BaBar) on the pion-photon transition form factor is carried out using light-cone sum rules. The analysis includes the next-to-leading QCD radiative corrections and the twist-four contributions, while the main next-to-next-to-leading term and the twist-six contribution are taken into account in the form of theoretical uncertainties. We use the information extracted from the data to investigate the pivotal characteristics of the pion distribution amplitude. This is done by dividing the data into two sets: one containing all data up to 9 GeV 2, whereas the other incorporates also the high- Q tail of the BaBar data. We find that it is not possible to accommodate into the fit these BaBar data points with the same accuracy and conclude that it is difficult to explain these data in the standard scheme of OCD.

  5. Systematic estimation of theoretical uncertainties in the calculation of the pion-photon transition form factor using light-cone sum rules

    NASA Astrophysics Data System (ADS)

    Mikhailov, S. V.; Pimikov, A. V.; Stefanis, N. G.

    2016-06-01

    We consider the calculation of the pion-photon transition form factor Fγ*γπ0(Q2) within light-cone sum rules focusing attention to the low-mid region of momenta. The central aim is to estimate the theoretical uncertainties which originate from a wide variety of sources related to (i) the relevance of next-to-next-to-leading order radiative corrections (ii) the influence of the twist-four and the twist-six term (iii) the sensitivity of the results on auxiliary parameters, like the Borel scale M2, (iv) the role of the phenomenological description of resonances, and (v) the significance of a small but finite virtuality of the quasireal photon. Predictions for Fγ*γπ0(Q2) are presented which include all these uncertainties and found to comply within the margin of experimental error with the existing data in the Q2 range between 1 and 5 GeV2 , thus justifying the reliability of the applied calculational scheme. This provides a solid basis for confronting theoretical predictions with forthcoming data bearing small statistical errors.

  6. Short-time universal scaling and light-cone dynamics after a quench in an isolated quantum system in d spatial dimensions

    NASA Astrophysics Data System (ADS)

    Chiocchetta, Alessio; Tavora, Marco; Gambassi, Andrea; Mitra, Aditi

    2016-10-01

    We investigate the effects of fluctuations on the dynamics of an isolated quantum system represented by a (ϕ2)2 field theory with O (N ) symmetry after a quench in d >2 spatial dimensions. A perturbative renormalization-group approach involving a dimensional expansion in ɛ =4 -d is employed in order to study the evolution within a prethermal regime controlled by elastic dephasing. In particular, we focus on a quench from a disordered initial state to the critical point, which introduces an effective temporal boundary in the evolution. At this boundary, the relevant fields acquire an anomalous scaling dimension, while the evolution of both the order parameter and its correlation and response functions display universal aging. Since the relevant excitations propagate ballistically, a light cone in real space emerges. At longer times, the onset of inelastic scattering appears as secularly growing self-generated dissipation in the effective Keldysh field theory, with the strength of the dissipative vertices providing an estimate for the time needed to leave the prethermal regime.

  7. Low Activation and Fast Inactivation of Transducin in Carp Cones*

    PubMed Central

    Tachibanaki, Shuji; Yonetsu, Shin-Ichi; Fukaya, Satoshi; Koshitani, Yuki; Kawamura, Satoru

    2012-01-01

    Cone photoreceptors show lower light sensitivity and briefer light responses than rod photoreceptors. The light detection signal in these cells is amplified through a phototransduction cascade. The first step of amplification in the cascade is the activation of a GTP-binding protein, transducin (Tr), by light-activated visual pigment (R*). We quantified transducin activation by measuring the binding of GTPγS in purified carp rod and cone membrane preparations with the use of a rapid quench apparatus and found that transducin activation by an R* molecule is ∼5 times less efficient in cones than in rods. Transducin activation terminated in less than 1 s in cones, more quickly than in rods. The rate of GTP hydrolysis in Tr*, and thus the rate of Tr* inactivation, was ∼25 times higher in cones than in rods. This faster inactivation of Tr* ensures briefer light responses in cones. The expression level of RGS9 was found to be ∼20 times higher in cones than in rods, which explains higher GTP hydrolytic activity and, thus, faster Tr* inactivation in cones than in rods. Although carp rods and cones express rod- or cone-versions of visual pigment and transducin, these molecules themselves do not seem to induce the differences significantly in the transducin activation and Tr* inactivation in rods and cones. Instead, the differences seem to be brought about in a rod or cone cell-type specific manner. PMID:23045532

  8. GENERALIZED CONVEXITY CONES.

    DTIC Science & Technology

    Contents: Introduction The dual cone of C (psi sub 1,..., psi sub n) Extreme rays The cone dual to an intersection of generalized convexity cones... Generalized difference quotients and multivariate convexity Miscellaneous applications of generalized convexity.

  9. Modeling of light dynamic cone penetration test - Panda 3 ® in granular material by using 3D Discrete element method

    NASA Astrophysics Data System (ADS)

    Tran, Quoc Anh; Chevalier, Bastien; Benz, Miguel; Breul, Pierre; Gourvès, Roland

    2017-06-01

    The recent technological developments made on the light dynamic penetration test Panda 3 ® provide a dynamic load-penetration curve σp - sp for each impact. This curve is influenced by the mechanical and physical properties of the investigated granular media. In order to analyze and exploit the load-penetration curve, a numerical model of penetration test using 3D Discrete Element Method is proposed for reproducing tests in dynamic conditions in granular media. All parameters of impact used in this model have at first been calibrated by respecting mechanical and geometrical properties of the hammer and the rod. There is a good agreement between experimental results and the ones obtained from simulations in 2D or 3D. After creating a sample, we will simulate the Panda 3 ®. It is possible to measure directly the dynamic load-penetration curve occurring at the tip for each impact. Using the force and acceleration measured in the top part of the rod, it is possible to separate the incident and reflected waves and then calculate the tip's load-penetration curve. The load-penetration curve obtained is qualitatively similar with that obtained by experimental tests. In addition, the frequency analysis of the measured signals present also a good compliance with that measured in reality when the tip resistance is qualitatively similar.

  10. Inferred L/M cone opsin polymorphism of ancestral tarsiers sheds dim light on the origin of anthropoid primates

    PubMed Central

    Melin, Amanda D.; Matsushita, Yuka; Moritz, Gillian L.; Dominy, Nathaniel J.; Kawamura, Shoji

    2013-01-01

    Tarsiers are small nocturnal primates with a long history of fuelling debate on the origin and evolution of anthropoid primates. Recently, the discovery of M and L opsin genes in two sister species, Tarsius bancanus (Bornean tarsier) and Tarsius syrichta (Philippine tarsier), respectively, was interpreted as evidence of an ancestral long-to-middle (L/M) opsin polymorphism, which, in turn, suggested a diurnal or cathemeral (arrhythmic) activity pattern. This view is compatible with the hypothesis that stem tarsiers were diurnal; however, a reversion to nocturnality during the Middle Eocene, as evidenced by hyper-enlarged orbits, predates the divergence of T. bancanus and T. syrichta in the Late Miocene. Taken together, these findings suggest that some nocturnal tarsiers possessed high-acuity trichromatic vision, a concept that challenges prevailing views on the adaptive origins of the anthropoid visual system. It is, therefore, important to explore the plausibility and antiquity of trichromatic vision in the genus Tarsius. Here, we show that Sulawesi tarsiers (Tarsius tarsier), a phylogenetic out-group of Philippine and Bornean tarsiers, have an L opsin gene that is more similar to the L opsin gene of T. syrichta than to the M opsin gene of T. bancanus in non-synonymous nucleotide sequence. This result suggests that an L/M opsin polymorphism is the ancestral character state of crown tarsiers and raises the possibility that many hallmarks of the anthropoid visual system evolved under dim (mesopic) light conditions. This interpretation challenges the persistent nocturnal–diurnal dichotomy that has long informed debate on the origin of anthropoid primates. PMID:23536597

  11. Normal Perceptual Sensitivity Arising From Weakly Reflective Cone Photoreceptors

    PubMed Central

    Bruce, Kady S.; Harmening, Wolf M.; Langston, Bradley R.; Tuten, William S.; Roorda, Austin; Sincich, Lawrence C.

    2015-01-01

    Purpose To determine the light sensitivity of poorly reflective cones observed in retinas of normal subjects, and to establish a relationship between cone reflectivity and perceptual threshold. Methods Five subjects (four male, one female) with normal vision were imaged longitudinally (7–26 imaging sessions, representing 82–896 days) using adaptive optics scanning laser ophthalmoscopy (AOSLO) to monitor cone reflectance. Ten cones with unusually low reflectivity, as well as 10 normally reflective cones serving as controls, were targeted for perceptual testing. Cone-sized stimuli were delivered to the targeted cones and luminance increment thresholds were quantified. Thresholds were measured three to five times per session for each cone in the 10 pairs, all located 2.2 to 3.3° from the center of gaze. Results Compared with other cones in the same retinal area, three of 10 monitored dark cones were persistently poorly reflective, while seven occasionally manifested normal reflectance. Tested psychophysically, all 10 dark cones had thresholds comparable with those from normally reflecting cones measured concurrently (P = 0.49). The variation observed in dark cone thresholds also matched the wide variation seen in a large population (n = 56 cone pairs, six subjects) of normal cones; in the latter, no correlation was found between cone reflectivity and threshold (P = 0.0502). Conclusions Low cone reflectance cannot be used as a reliable indicator of cone sensitivity to light in normal retinas. To improve assessment of early retinal pathology, other diagnostic criteria should be employed along with imaging and cone-based microperimetry. PMID:26193919

  12. Fast electron generation in cones with ultraintense laser pulses

    SciTech Connect

    Van Woerkom, L.; Chowdhury, E.; Link, A.; Offermann, D.; Ovchinnikov, V.; Schumacher, D. W.; Akli, K. U.; Stephens, R. B.; Bartal, T.; Beg, F. N.; Chawla, S.; King, J. A.; Ma, T.; Chen, C. D.; Freeman, R. R.; Hey, D.; Key, M. H.; MacKinnon, A. J.; MacPhee, A. G.; Patel, P. K.

    2008-05-15

    Experimental results from copper cones irradiated with ultraintense laser light are presented. Spatial images and total yields of Cu K{sub {alpha}} fluorescence were measured as a function of the laser focusing properties. The fluorescence emission extends into the cone approximately 300 {mu}m from the cone tip and cannot be explained by ray tracing including cone wall absorption. In addition, the total fluorescence yield from cones is an order of magnitude higher than for equivalent mass foil targets. Indications are that the physics of the laser-cone interaction is dominated by preplasma created from the long duration, low-energy prepulse from the laser.

  13. Rod Phosphodiesterase-6 (PDE6) Catalytic Subunits Restore Cone Function in a Mouse Model Lacking Cone PDE6 Catalytic Subunit*

    PubMed Central

    Kolandaivelu, Saravanan; Chang, Bo; Ramamurthy, Visvanathan

    2011-01-01

    Rod and cone photoreceptor neurons utilize discrete PDE6 enzymes that are crucial for phototransduction. Rod PDE6 is composed of heterodimeric catalytic subunits (αβ), while the catalytic core of cone PDE6 (α′) is a homodimer. It is not known if variations between PDE6 subunits preclude rod PDE6 catalytic subunits from coupling to the cone phototransduction pathway. To study this issue, we generated a cone-dominated mouse model lacking cone PDE6 (Nrl−/− cpfl1). In this animal model, using several independent experimental approaches, we demonstrated the expression of rod PDE6 (αβ) and the absence of cone PDE6 (α′) catalytic subunits. The rod PDE6 enzyme expressed in cone cells is active and contributes to the hydrolysis of cGMP in response to light. In addition, rod PDE6 expressed in cone cells couples to the light signaling pathway to produce S-cone responses. However, S-cone responses and light-dependent cGMP hydrolysis were eliminated when the β-subunit of rod PDE6 was removed (Nrl−/− cpfl1 rd). We conclude that either rod or cone PDE6 can effectively couple to the cone phototransduction pathway to mediate visual signaling. Interestingly, we also found that functional PDE6 is required for trafficking of M-opsin to cone outer segments. PMID:21799013

  14. The Super-Cone

    ERIC Educational Resources Information Center

    Fülöp, Zsolt

    2009-01-01

    Using the concept of exploded and compressed numbers the author constructs the supercone which is able to turn upon the border of three dimensional space and breaks through it. The introduction of super-cone gives a possibility for students to see the properties of traditional cone while the super-cone is not a traditional cone. Moreover we show…

  15. Loss of cone cyclic nucleotide-gated channel leads to alterations in light response modulating system and cellular stress response pathways: a gene expression profiling study

    PubMed Central

    Ma, Hongwei; Thapa, Arjun; Morris, Lynsie M.; Michalakis, Stylianos; Biel, Martin; Frank, Mark Barton; Bebak, Melissa; Ding, Xi-Qin

    2013-01-01

    The cone photoreceptor cyclic nucleotide-gated (CNG) channel is essential for central and color vision and visual acuity. Mutations in the channel subunits CNGA3 and CNGB3 are associated with achromatopsia and cone dystrophy. We investigated the gene expression profiles in mouse retina with CNG channel deficiency using whole genome expression microarrays. As cones comprise only 2 to 3% of the total photoreceptor population in the wild-type mouse retina, the mouse lines with CNG channel deficiency on a cone-dominant background, i.e. Cnga3−/−/Nrl−/− and Cngb3−/−/Nrl−/− mice, were used in our study. Comparative data analysis revealed a total of 105 genes altered in Cnga3−/−/Nrl−/− and 92 in Cngb3−/−/Nrl−/− retinas, relative to Nrl−/− retinas, with 27 genes changed in both genotypes. The differentially expressed genes primarily encode proteins associated with cell signaling, cellular function maintenance and gene expression. Ingenuity pathway analysis (IPA) identified 26 and 9 canonical pathways in Cnga3−/−/Nrl−/− and Cngb3−/−/Nrl−/− retinas, respectively, with 6 pathways being shared. The shared pathways include phototransduction, cAMP/PKA-mediated signaling, endothelin signaling, and EIF2/endoplasmic reticulum (ER) stress, whereas the IL-1, CREB, and purine metabolism signaling were found to specifically associate with Cnga3 deficiency. Thus, CNG channel deficiency differentially regulates genes that affect cell processes such as phototransduction, cellular survival and gene expression, and such regulations play a crucial role(s) in the retinal adaptation to impaired cone phototransduction. Though lack of Cnga3 and Cngb3 shares many common pathways, deficiency of Cnga3 causes more significant alterations in gene expression. This work provides insights into how cones respond to impaired phototransduction at the gene expression levels. PMID:23740940

  16. Peripherin-2 differentially interacts with cone opsins in outer segments of cone photoreceptors.

    PubMed

    Nguyen, O N Phuong; Böhm, Sybille; Gießl, Andreas; Butz, Elisabeth S; Wolfrum, Uwe; Brandstätter, Johann H; Wahl-Schott, Christian; Biel, Martin; Becirovic, Elvir

    2016-06-15

    Peripherin-2 is a glycomembrane protein exclusively expressed in the light-sensing compartments of rod and cone photoreceptors designated as outer segments (OS). Mutations in peripherin-2 are associated with degenerative retinal diseases either affecting rod or cone photoreceptors. While peripherin-2 has been extensively studied in rods, there is only little information on its supramolecular organization and function in cones. Recently, we have demonstrated that peripherin-2 interacts with the light detector rhodopsin in OS of rods. It remains unclear, however, if peripherin-2 also binds to cone opsins. Here, using a combination of co-immunoprecipitation analyses, transmission electron microscopy (TEM)-based immunolabeling experiments, and quantitative fluorescence resonance energy transfer (FRET) measurements in cone OS of wild type mice, we demonstrate that peripherin-2 binds to both, S-opsin and M-opsin. However, FRET-based quantification of the respective interactions indicated significantly less stringent binding of peripherin-2 to S-opsin compared to its interaction with M-opsin. Subsequent TEM-studies also showed less co-localization of peripherin-2 and S-opsin in cone OS compared to peripherin-2 and M-opsin. Furthermore, quantitative FRET analysis in acutely isolated cone OS revealed that the cone degeneration-causing V268I mutation in peripherin-2 selectively reduced binding to M-opsin without affecting the peripherin-2 interaction to S-opsin or rhodopsin. The differential binding of peripherin-2 to cone opsins and the mutant-specific interference with the peripherin-2/M-opsin binding points to a novel role of peripherin-2 in cones and might contribute to understanding the differential penetrance of certain peripherin-2 mutations in rods and cones. Finally, our results provide a proof-of-principle for quantitative FRET measurements of protein-protein interactions in cone OS. © The Author 2016. Published by Oxford University Press. All rights reserved. For

  17. Recoverin depletion accelerates cone photoresponse recovery

    PubMed Central

    Zang, Jingjing; Keim, Jennifer; Kastenhuber, Edda; Gesemann, Matthias; Neuhauss, Stephan C. F.

    2015-01-01

    The neuronal Ca2+-binding protein Recoverin has been shown to regulate phototransduction termination in mammalian rods. Here we identify four recoverin genes in the zebrafish genome, rcv1a, rcv1b, rcv2a and rcv2b, and investigate their role in modulating the cone phototransduction cascade. While Recoverin-1b is only found in the adult retina, the other Recoverins are expressed throughout development in all four cone types, except Recoverin-1a, which is expressed only in rods and UV cones. Applying a double flash electroretinogram (ERG) paradigm, downregulation of Recoverin-2a or 2b accelerates cone photoresponse recovery, albeit at different light intensities. Exclusive recording from UV cones via spectral ERG reveals that knockdown of Recoverin-1a alone has no effect, but Recoverin-1a/2a double-knockdowns showed an even shorter recovery time than Recoverin-2a-deficient larvae. We also showed that UV cone photoresponse kinetics depend on Recoverin-2a function via cone-specific kinase Grk7a. This is the first in vivo study demonstrating that cone opsin deactivation kinetics determine overall photoresponse shut off kinetics. PMID:26246494

  18. The Cone-specific Visual Cycle

    PubMed Central

    Wang, Jin-Shan; Kefalov, Vladimir J

    2010-01-01

    Cone photoreceptors mediate our daytime vision and function under bright and rapidly-changing light conditions. As their visual pigment is destroyed in the process of photoactivation, the continuous function of cones imposes the need for rapid recycling of their chromophore and regeneration of their pigment. The canonical retinoid visual cycle through the retinal pigment epithelium cells recycles chromophore and supplies it to both rods and cones. However, shortcomings of this pathway, including its slow rate and competition with rods for chromophore, have led to the suggestion that cones might use a separate mechanism for recycling of chromophore. In the past four decades biochemical studies have identified enzymatic activities consistent with recycling chromophore in the retinas of cone-dominant animals, such as chicken and ground squirrel. These studies have led to the hypothesis of a cone-specific retina visual cycle. The physiological relevance of these studies was controversial for a long time and evidence for the function of this visual cycle emerged only in very recent studies and will be the focus of this review. The retina visual cycle supplies chromophore and promotes pigment regeneration only in cones but not in rods. This pathway is independent of the pigment epithelium and instead involves the Müller cells in the retina, where chromophore is recycled and supplied selectively to cones. The rapid supply of chromophore through the retina visual cycle is critical for extending the dynamic range of cones to bright light and for their rapid dark adaptation following exposure to light. The importance of the retina visual cycle is emphasized also by its preservation through evolution as its function has now been demonstrated in species ranging from salamander to zebrafish, mouse, primate, and human. PMID:21111842

  19. Turning cones off: the role of the 9-methyl group of retinal in red cones.

    PubMed

    Estevez, Maureen E; Ala-Laurila, Petri; Crouch, Rosalie K; Cornwall, M Carter

    2006-12-01

    Our ability to see in bright light depends critically on the rapid rate at which cone photoreceptors detect and adapt to changes in illumination. This is achieved, in part, by their rapid response termination. In this study, we investigate the hypothesis that this rapid termination of the response in red cones is dependent on interactions between the 9-methyl group of retinal and red cone opsin, which are required for timely metarhodopsin (Meta) II decay. We used single-cell electrical recordings of flash responses to assess the kinetics of response termination and to calculate guanylyl cyclase (GC) rates in salamander red cones containing native visual pigment as well as visual pigment regenerated with 11-cis 9-demethyl retinal, an analogue of retinal in which the 9-methyl group is missing. After exposure to bright light that photoactivated more than approximately 0.2% of the pigment, red cones containing the analogue pigment had a slower recovery of both flash response amplitudes and GC rates (up to 10 times slower at high bleaches) than red cones containing 11-cis retinal. This finding is consistent with previously published biochemical data demonstrating that red cone opsin regenerated in vitro with 11-cis 9-demethyl retinal exhibited prolonged activation as a result of slowed Meta II decay. Our results suggest that two different mechanisms regulate the recovery of responsiveness in red cones after exposure to light. We propose a model in which the response recovery in red cones can be regulated (particularly at high light intensities) by the Meta II decay rate if that rate has been inhibited. In red cones, the interaction of the 9-methyl group of retinal with opsin promotes efficient Meta II decay and, thus, the rapid rate of recovery.

  20. Non-image Forming Light Detection by Melanopsin, Rhodopsin, and Long-Middlewave (L/W) Cone Opsin in the Subterranean Blind Mole Rat, Spalax Ehrenbergi: Immunohistochemical Characterization, Distribution, and Connectivity

    PubMed Central

    Esquiva, Gema; Avivi, Aaron; Hannibal, Jens

    2016-01-01

    The blind mole rat, Spalax ehrenbergi, can, despite severely degenerated eyes covered by fur, entrain to the daily light/dark cycle and adapt to seasonal changes due to an intact circadian timing system. The present study demonstrates that the Spalax retina contains a photoreceptor layer, an outer nuclear layer (ONL), an outer plexiform layer (OPL), an inner nuclear layer (INL), an inner plexiform layer (IPL), and a ganglion cell layer (GCL). By immunohistochemistry, the number of melanopsin (mRGCs) and non-melanopsin bearing retinal ganglion cells was analyzed in detail. Using the ganglion cell marker RNA-binding protein with multiple splicing (RBPMS) it was shown that the Spalax eye contains 890 ± 62 RGCs. Of these, 87% (752 ± 40) contain melanopsin (cell density 788 melanopsin RGCs/mm2). The remaining RGCs were shown to co-store Brn3a and calretinin. The melanopsin cells were located mainly in the GCL with projections forming two dendritic plexuses located in the inner part of the IPL and in the OPL. Few melanopsin dendrites were also found in the ONL. The Spalax retina is rich in rhodopsin and long/middle wave (L/M) cone opsin bearing photoreceptor cells. By using Ctbp2 as a marker for ribbon synapses, both rods and L/M cone ribbons containing pedicles in the OPL were found in close apposition with melanopsin dendrites in the outer plexus suggesting direct synaptic contact. A subset of cone bipolar cells and all photoreceptor cells contain recoverin while a subset of bipolar and amacrine cells contain calretinin. The calretinin expressing amacrine cells seemed to form synaptic contacts with rhodopsin containing photoreceptor cells in the OPL and contacts with melanopsin cell bodies and dendrites in the IPL. The study demonstrates the complex retinal circuitry used by the Spalax to detect light, and provides evidence for both melanopsin and non-melanopsin projecting pathways to the brain. PMID:27375437

  1. Transformation of light double cones in the human retina: the origin of trichromatism, of 4D-spatiotemporal vision, and of patchwise 4D Fourier transformation in Talbot imaging

    NASA Astrophysics Data System (ADS)

    Lauinger, Norbert

    1997-09-01

    The interpretation of the 'inverted' retina of primates as an 'optoretina' (a light cones transforming diffractive cellular 3D-phase grating) integrates the functional, structural, and oscillatory aspects of a cortical layer. It is therefore relevant to consider prenatal developments as a basis of the macro- and micro-geometry of the inner eye. This geometry becomes relevant for the postnatal trichromatic synchrony organization (TSO) as well as the adaptive levels of human vision. It is shown that the functional performances, the trichromatism in photopic vision, the monocular spatiotemporal 3D- and 4D-motion detection, as well as the Fourier optical image transformation with extraction of invariances all become possible. To transform light cones into reciprocal gratings especially the spectral phase conditions in the eikonal of the geometrical optical imaging before the retinal 3D-grating become relevant first, then in the von Laue resp. reciprocal von Laue equation for 3D-grating optics inside the grating and finally in the periodicity of Talbot-2/Fresnel-planes in the near-field behind the grating. It is becoming possible to technically realize -- at least in some specific aspects -- such a cortical optoretina sensor element with its typical hexagonal-concentric structure which leads to these visual functions.

  2. The reliability of parafoveal cone density measurements

    PubMed Central

    Liu, Benjamin S; Tarima, Sergey; Visotcky, Alexis; Pechauer, Alex; Cooper, Robert F; Landsem, Leah; Wilk, Melissa A; Godara, Pooja; Makhijani, Vikram; Sulai, Yusufu N; Syed, Najia; Yasumura, Galen; Garg, Anupam K; Pennesi, Mark E; Lujan, Brandon J; Dubra, Alfredo; Duncan, Jacque L; Carroll, Joseph

    2014-01-01

    Background Adaptive optics scanning light ophthalmoscopy (AOSLO) enables direct visualisation of the cone mosaic, with metrics such as cone density and cell spacing used to assess the integrity or health of the mosaic. Here we examined the interobserver and inter-instrument reliability of cone density measurements. Methods For the interobserver reliability study, 30 subjects with no vision-limiting pathology were imaged. Three image sequences were acquired at a single parafoveal location and aligned to ensure that the three images were from the same retinal location. Ten observers used a semiautomated algorithm to identify the cones in each image, and this was repeated three times for each image. To assess inter-instrument reliability, 20 subjects were imaged at eight parafoveal locations on one AOSLO, followed by the same set of locations on the second AOSLO. A single observer manually aligned the pairs of images and used the semiautomated algorithm to identify the cones in each image. Results Based on a factorial study design model and a variance components model, the interobserver study's largest contribution to variability was the subject (95.72%) while the observer's contribution was only 1.03%. For the inter-instrument study, an average cone density intraclass correlation coefficient (ICC) of between 0.931 and 0.975 was calculated. Conclusions With the AOSLOs used here, reliable cone density measurements can be obtained between observers and between instruments. Additional work is needed to determine how these results vary with differences in image quality. PMID:24855115

  3. Photovoltage of Rods and Cones in the Macaque Retina

    NASA Astrophysics Data System (ADS)

    Schneeweis, David M.; Schnapf, Julie L.

    1995-05-01

    The kinetics, gain, and reliability of light responses of rod and cone photoreceptors are important determinants of overall visual sensitivity. In voltage recordings from photoreceptors in an intact primate retina, rods were found to be functionally isolated from each other, unlike the tightly coupled rods of cold-blooded vertebrates. Cones were observed to receive excitatory input from rods, which indicates that the cone pathway also processes rod signals. This input might be expected to degrade the spatial resolution of mesopic vision.

  4. CRALBP supports the mammalian retinal visual cycle and cone vision.

    PubMed

    Xue, Yunlu; Shen, Susan Q; Jui, Jonathan; Rupp, Alan C; Byrne, Leah C; Hattar, Samer; Flannery, John G; Corbo, Joseph C; Kefalov, Vladimir J

    2015-02-01

    Mutations in the cellular retinaldehyde-binding protein (CRALBP, encoded by RLBP1) can lead to severe cone photoreceptor-mediated vision loss in patients. It is not known how CRALBP supports cone function or how altered CRALBP leads to cone dysfunction. Here, we determined that deletion of Rlbp1 in mice impairs the retinal visual cycle. Mice lacking CRALBP exhibited M-opsin mislocalization, M-cone loss, and impaired cone-driven visual behavior and light responses. Additionally, M-cone dark adaptation was largely suppressed in CRALBP-deficient animals. While rearing CRALBP-deficient mice in the dark prevented the deterioration of cone function, it did not rescue cone dark adaptation. Adeno-associated virus-mediated restoration of CRALBP expression specifically in Müller cells, but not retinal pigment epithelial (RPE) cells, rescued the retinal visual cycle and M-cone sensitivity in knockout mice. Our results identify Müller cell CRALBP as a key component of the retinal visual cycle and demonstrate that this pathway is important for maintaining normal cone-driven vision and accelerating cone dark adaptation.

  5. Cone outer segment morphology and cone function in the Rpe65-/- Nrl-/- mouse retina are amenable to retinoid replacement.

    PubMed

    Kunchithapautham, Kannan; Coughlin, Beth; Crouch, Rosalie K; Rohrer, Bärbel

    2009-10-01

    RPE65, a major retinal pigment epithelium protein, is essential in generating 11-cis retinal, the chromophore for all opsins. Without chromophore, cone opsins are mislocalized and cones degenerate rapidly (e.g., Rpe65(-/-) mouse). Function, survival, and correct targeting of opsins is increased in Rpe65(-/-) cones on supplying 11-cis retinal. Here, we determine the consequences of 11-cis retinal withdrawal and supplementation on cone development in the all-cone Nrl(-/-) retina. Rpe65(-/-) Nrl(-/-), Nrl(-/-), and wild-type mice were examined. Cone structure was analyzed by using TUNEL assay, electron microscopy, and cone-specific antibodies. Cone function was assessed with light-adapted single-flash ERGs. Rpe65(-/-)Nrl(-/-) mice had an increased number of TUNEL-positive photoreceptors during programmed cell death compared with Nrl(-/-) mice, in addition to accelerated age-related degeneration. Cone function in Rpe65(-/-)Nrl(-/-) mice was minimal, and opsins were mislocalized. Treatment with 11-cis retinal restored cone function, promoted outer segment formation, and enabled opsin trafficking to outer segments. Eliminating Rpe65 prevented rosette formation in Nrl(-/-) retinas; supplementation of Rpe65(-/-)Nrl(-/-) mice with 11-cis retinal resulted in their reoccurrence. Taken together, function and opsin trafficking in Nrl(-/-) and wild-type cones are comparable, confirming and extending our findings that cone maturation and outer segment development are dependent on the presence of chromophore. The data on age-related cone death in Rpe65(-/-)Nrl(-/-) mice and the reintroduction of rosettes after 11-cis retinal injections confirm that outer segments, which for steric reasons appear to introduce rosettes in an all-cone retina, are essential for cell survival. These results are important for understanding and treating chromophore-related cone dystrophies.

  6. Modal content of living human cone photoreceptors

    PubMed Central

    Liu, Zhuolin; Kocaoglu, Omer P.; Turner, Timothy L.; Miller, Donald T.

    2015-01-01

    Decades of experimental and theoretical investigations have established that photoreceptors capture light based on the principles of optical waveguiding. Yet considerable uncertainty remains, even for the most basic prediction as to whether photoreceptors support more than a single waveguide mode. To test for modal behavior in human cone photoreceptors in the near infrared, we took advantage of adaptive-optics optical coherence tomography (AO-OCT, λc = 785 nm) to noninvasively image in three dimensions the reflectance profile of cones. Modal content of reflections generated at the cone inner segment and outer segment junction (IS/OS) and cone outer segment tip (COST) was examined over a range of cone diameters in 1,802 cones from 0.6° to 10° retinal eccentricity. Second moment analysis in conjunction with theoretical predictions indicate cone IS and OS have optical properties consistent of waveguides, which depend on segment diameter and refractive index. Cone IS was found to support a single mode near the fovea (≤3°) and multiple modes further away (>4°). In contrast, no evidence of multiple modes was found in the cone OSs. The IS/OS and COST reflections share a common optical aperture, are most circular near the fovea, show no orientation preference, and are temporally stable. We tested mode predictions of a conventional step-index fiber model and found that in order to fit our AO-OCT results required a lower estimate of the IS refractive index and introduction of an IS focusing/tapering effect. PMID:26417509

  7. Modal content of living human cone photoreceptors.

    PubMed

    Liu, Zhuolin; Kocaoglu, Omer P; Turner, Timothy L; Miller, Donald T

    2015-09-01

    Decades of experimental and theoretical investigations have established that photoreceptors capture light based on the principles of optical waveguiding. Yet considerable uncertainty remains, even for the most basic prediction as to whether photoreceptors support more than a single waveguide mode. To test for modal behavior in human cone photoreceptors in the near infrared, we took advantage of adaptive-optics optical coherence tomography (AO-OCT, λc = 785 nm) to noninvasively image in three dimensions the reflectance profile of cones. Modal content of reflections generated at the cone inner segment and outer segment junction (IS/OS) and cone outer segment tip (COST) was examined over a range of cone diameters in 1,802 cones from 0.6° to 10° retinal eccentricity. Second moment analysis in conjunction with theoretical predictions indicate cone IS and OS have optical properties consistent of waveguides, which depend on segment diameter and refractive index. Cone IS was found to support a single mode near the fovea (≤3°) and multiple modes further away (>4°). In contrast, no evidence of multiple modes was found in the cone OSs. The IS/OS and COST reflections share a common optical aperture, are most circular near the fovea, show no orientation preference, and are temporally stable. We tested mode predictions of a conventional step-index fiber model and found that in order to fit our AO-OCT results required a lower estimate of the IS refractive index and introduction of an IS focusing/tapering effect.

  8. Effects of light environment during growth on the expression of cone opsin genes and behavioral spectral sensitivities in guppies (Poecilia reticulata).

    PubMed

    Sakai, Yusuke; Ohtsuki, Hajime; Kasagi, Satoshi; Kawamura, Shoji; Kawata, Masakado

    2016-05-18

    The visual system is important for animals for mate choice, food acquisition, and predator avoidance. Animals possessing a visual system can sense particular wavelengths of light emanating from objects and their surroundings and perceive their environments by processing information contained in these visual perceptions of light. Visual perception in individuals varies with the absorption spectra of visual pigments and the expression levels of opsin genes, which may be altered according to the light environments. However, which light environments and the mechanism by which they change opsin expression profiles and whether these changes in opsin gene expression can affect light sensitivities are largely unknown. This study determined whether the light environment during growth induced plastic changes in opsin gene expression and behavioral sensitivity to particular wavelengths of light in guppies (Poecilia reticulata). Individuals grown under orange light exhibited a higher expression of long wavelength-sensitive (LWS) opsin genes and a higher sensitivity to 600-nm light than those grown under green light. In addition, we confirmed that variations in the expression levels of LWS opsin genes were related to the behavioral sensitivities to long wavelengths of light. The light environment during the growth stage alters the expression levels of LWS opsin genes and behavioral sensitivities to long wavelengths of light in guppies. The plastically enhanced sensitivity to background light due to changes in opsin gene expression can enhance the detection and visibility of predators and foods, thereby affecting survival. Moreover, changes in sensitivities to orange light may lead to changes in the discrimination of orange/red colors of male guppies and might alter female preferences for male color patterns.

  9. Cone visual pigments.

    PubMed

    Imamoto, Yasushi; Shichida, Yoshinori

    2014-05-01

    Cone visual pigments are visual opsins that are present in vertebrate cone photoreceptor cells and act as photoreceptor molecules responsible for photopic vision. Like the rod visual pigment rhodopsin, which is responsible for scotopic vision, cone visual pigments contain the chromophore 11-cis-retinal, which undergoes cis-trans isomerization resulting in the induction of conformational changes of the protein moiety to form a G protein-activating state. There are multiple types of cone visual pigments with different absorption maxima, which are the molecular basis of color discrimination in animals. Cone visual pigments form a phylogenetic sister group with non-visual opsin groups such as pinopsin, VA opsin, parapinopsin and parietopsin groups. Cone visual pigments diverged into four groups with different absorption maxima, and the rhodopsin group diverged from one of the four groups of cone visual pigments. The photochemical behavior of cone visual pigments is similar to that of pinopsin but considerably different from those of other non-visual opsins. G protein activation efficiency of cone visual pigments is also comparable to that of pinopsin but higher than that of the other non-visual opsins. Recent measurements with sufficient time-resolution demonstrated that G protein activation efficiency of cone visual pigments is lower than that of rhodopsin, which is one of the molecular bases for the lower amplification of cones compared to rods. In this review, the uniqueness of cone visual pigments is shown by comparison of their molecular properties with those of non-visual opsins and rhodopsin. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks. © 2013 Elsevier B.V. All rights reserved.

  10. GRK1-dependent phosphorylation of S and M opsins and their binding to cone arrestin during cone phototransduction in the mouse retina.

    PubMed

    Zhu, Xuemei; Brown, Bruce; Li, Aimin; Mears, Alan J; Swaroop, Anand; Craft, Cheryl M

    2003-07-09

    The shutoff mechanisms of the rod visual transduction cascade involve G-protein-coupled receptor (GPCR) kinase 1 (GRK1) phosphorylation of light-activated rhodopsin (R*) followed by rod arrestin binding. Deactivation of the cone phototransduction cascade in the mammalian retina is delineated poorly. In this study we sought to explore the potential mechanisms underlying the quenching of the phototransduction cascade in cone photoreceptors by using mouse models lacking rods and/or GRK1. Using the "pure-cone" retinas of the neural retina leucine zipper (Nrl) knock-out (KO, -/-) mice (Mears et al., 2001), we have demonstrated the light-dependent, multi-site phosphorylation of both S and M cone opsins by in situ phosphorylation and isoelectric focusing. Immunoprecipitation with affinity-purified polyclonal antibodies against either mouse cone arrestin (mCAR) or mouse S and M cone opsins revealed specific binding of mCAR to light-activated, phosphorylated cone opsins. To elucidate the potential role of GRK1 in cone opsin phosphorylation, we created Nrl and Grk1 double knock-out (Nrl-/-Grk1-/-) mice by crossing the Nrl-/- mice with Grk1-/- mice (Chen et al., 1999). We found that, in the retina of these mice, the light-activated cone opsins were neither phosphorylated nor bound with mCAR. Our results demonstrate, for the first time in a mammalian species, that cone opsins are phosphorylated and that CAR binds to phosphorylated cone opsins after light activation.

  11. Salamander Blue-sensitive Cones Lost During Metamorphosis†

    PubMed Central

    Chen, Ying; Znoiko, Sergey; DeGrip, Willem J.; Crouch, Rosalie K.; Ma, Jian-xing

    2009-01-01

    The tiger salamander lives in shallow water with bright light in the aquatic phase, and in dim tunnels or caves in the terrestrial phase. In the aquatic phase, there are five types of photoreceptors—two types of rods and three types of cones. Our previous studies showed that the green rods and blue-sensitive cones contain the same visual pigment and have the same absorbance spectra; however, the green rods have a larger photon-catch area and thus have higher light sensitivity than the blue-sensitive cones. Here we show that after metamorphosis, the terrestrial salamander looses the blue-sensitive cones, while the density of the green rods increases. Moreover, the size of the green rod outer segments is increased in the terrestrial phase, compared to that in the aquatic phase. This switch from the blue-sensitive cones to the green rods may represent an adaptation to the dim light environment of the terrestrial phase. PMID:18331398

  12. Rapid Measurement of Individual Cone Photoreceptor Pointing using Focus Diversity

    PubMed Central

    Morris, Hugh J.; Codona, Johanan L.; Blanco, Leonardo; Doble, Nathan

    2015-01-01

    A novel method is presented to rapidly measure the pointing direction of individual human cone photoreceptors using adaptive optics (AO) retinal imaging. For a fixed entrance pupil position, the focal plane is rapidly modulated to image the guided light in various axial planes. For cones with different pointing directions, this focus diversity will cause a shift in their apparent position, allowing for their relative pointing to be determined. For four normal human subjects, retinal images were acquired, registered and the positions of individual cones tracked throughout the dataset. Variation in cone tilt was 0.02 radians, agreeing with other objective measurements on the same subjects at the same retinal locations. PMID:26368692

  13. Cone sampling array models

    NASA Technical Reports Server (NTRS)

    Ahumada, Albert J., Jr.; Poirson, Allen

    1987-01-01

    A model is described for positioning cones in the retina. Each cone has a circular disk of influence, and the disks are tightly packed outward from the center. This model has three parameters that can vary with eccentricity: the mean radius of the cone disk, the standard deviation of the cone disk radius, and the standard deviation of postpacking jitter. Estimates for these parameters out to 1.6 deg are found by using measurements reported by Hirsch and Hylton (1985) and Hirsch and Miller (1987) of the positions of the cone inner segments of an adult macaque. The estimation is based on fitting measures of variation in local intercone distances, and the fit to these measures is good.

  14. Design of a Trichromatic Cone Array

    PubMed Central

    Klein, Jennifer M.; Sterling, Peter; Brainard, David H.; Balasubramanian, Vijay

    2010-01-01

    Cones with peak sensitivity to light at long (L), medium (M) and short (S) wavelengths are unequal in number on the human retina: S cones are rare (<10%) while increasing in fraction from center to periphery, and the L/M cone proportions are highly variable between individuals. What optical properties of the eye, and statistical properties of natural scenes, might drive this organization? We found that the spatial-chromatic structure of natural scenes was largely symmetric between the L, M and S sensitivity bands. Given this symmetry, short wavelength attenuation by ocular media gave L/M cones a modest signal-to-noise advantage, which was amplified, especially in the denser central retina, by long-wavelength accommodation of the lens. Meanwhile, total information represented by the cone mosaic remained relatively insensitive to L/M proportions. Thus, the observed cone array design along with a long-wavelength accommodated lens provides a selective advantage: it is maximally informative. PMID:20168996

  15. Microspectrophotometric evidence for cone monochromacy in sharks

    NASA Astrophysics Data System (ADS)

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks—the rays and chimaeras—are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λmax 484-518 nm) and cone (λmax 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  16. Highly efficient retinal metabolism in cones

    PubMed Central

    Miyazono, Sadaharu; Shimauchi-Matsukawa, Yoshie; Tachibanaki, Shuji; Kawamura, Satoru

    2008-01-01

    After bleaching of visual pigment in vertebrate photoreceptors, all-trans retinal is reduced to all-trans retinol by retinol dehydrogenases (RDHs). We investigated this reaction in purified carp rods and cones, and we found that the reducing activity toward all-trans retinal in the outer segment (OS) of cones is >30 times higher than that of rods. The high activity of RDHs was attributed to high content of RDH8 in cones. In the inner segment (IS) in both rods and cones, RDH8L2 and RDH13 were found to be the major enzymes among RDH family proteins. We further found a previously undescribed and effective pathway to convert 11-cis retinol to 11-cis retinal in cones: this oxidative conversion did not require NADP+ and instead was coupled with reduction of all-trans retinal to all-trans retinol. The activity was >50 times effective than the oxidizing activity of RDHs that require NADP+. These highly effective reactions of removal of all-trans retinal by RDH8 and production of 11-cis retinal by the coupling reaction are probably the underlying mechanisms that ensure effective visual pigment regeneration in cones that function under much brighter light conditions than rods. PMID:18836074

  17. Microspectrophotometric evidence for cone monochromacy in sharks.

    PubMed

    Hart, Nathan Scott; Theiss, Susan Michelle; Harahush, Blake Kristin; Collin, Shaun Patrick

    2011-03-01

    Sharks are apex predators, and their evolutionary success is in part due to an impressive array of sensory systems, including vision. The eyes of sharks are well developed and function over a wide range of light levels. However, whilst close relatives of the sharks-the rays and chimaeras-are known to have the potential for colour vision, an evolutionary trait thought to provide distinct survival advantages, evidence for colour vision in sharks remains equivocal. Using single-receptor microspectrophotometry, we measured the absorbance spectra of visual pigments located in the retinal photoreceptors of 17 species of shark. We show that, while the spectral tuning of the rod (wavelength of maximum absorbance, λ(max) 484-518 nm) and cone (λ(max) 532-561 nm) visual pigments varies between species, each shark has only a single long-wavelength-sensitive cone type. This suggests that sharks may be cone monochromats and, therefore, potentially colour blind. Whilst cone monochromacy on land is rare, it may be a common strategy in the marine environment: many aquatic mammals (whales, dolphins and seals) also possess only a single, green-sensitive cone type. It appears that both sharks and marine mammals may have arrived at the same visual design by convergent evolution. The spectral tuning of the rod and cone pigments of sharks is also discussed in relation to their visual ecology.

  18. CRALBP supports the mammalian retinal visual cycle and cone vision

    PubMed Central

    Xue, Yunlu; Shen, Susan Q.; Jui, Jonathan; Rupp, Alan C.; Byrne, Leah C.; Hattar, Samer; Flannery, John G.; Corbo, Joseph C.; Kefalov, Vladimir J.

    2015-01-01

    Mutations in the cellular retinaldehyde–binding protein (CRALBP, encoded by RLBP1) can lead to severe cone photoreceptor–mediated vision loss in patients. It is not known how CRALBP supports cone function or how altered CRALBP leads to cone dysfunction. Here, we determined that deletion of Rlbp1 in mice impairs the retinal visual cycle. Mice lacking CRALBP exhibited M-opsin mislocalization, M-cone loss, and impaired cone-driven visual behavior and light responses. Additionally, M-cone dark adaptation was largely suppressed in CRALBP-deficient animals. While rearing CRALBP-deficient mice in the dark prevented the deterioration of cone function, it did not rescue cone dark adaptation. Adeno-associated virus–mediated restoration of CRALBP expression specifically in Müller cells, but not retinal pigment epithelial (RPE) cells, rescued the retinal visual cycle and M-cone sensitivity in knockout mice. Our results identify Müller cell CRALBP as a key component of the retinal visual cycle and demonstrate that this pathway is important for maintaining normal cone–driven vision and accelerating cone dark adaptation. PMID:25607845

  19. Rod-cone interactions and analysis of retinal disease.

    PubMed Central

    Arden, G B; Hogg, C R

    1985-01-01

    Cone flicker threshold rises as the rods dark adapt, though the cone threshold to continuous light remains constant. The rise is normally about 1 log unit, but in certain patients who complain of night blindness it may be as great as 2.5 log units. In these persons the kinetics of the rod-cone interaction are those of the recovery of rod sensitivity. The rods impose a low-pass filter on the cones. This effect is absent in congenital nyctalopia and X-linked retinoschisis. We suggest that cone flicker is maintained through a feedback system involving horizontal cells, and when the rod dark current returns in dark adaptation this feedback is altered. Rod cone interaction thus tests rod dark current, and cases of abnormal interaction in patients with retinitis pigmentosa occur, which indicate that the transduction mechanism and the membrane dark current may be differentially affected. Images PMID:3873959

  20. Fast Electron Generation in Cones with Ultra-Intense Laser Pulses

    SciTech Connect

    Mackinnon, A; VanWoerkom, L; Akli, K; Bartal, T; Beg, F; Chawla, S; Chen, C; Chowdhury, E; Freeman, R; Hey, D; Key, M; King, J; Link, A; MacPhee, A; Offermann, D; Ovchinnikov, V; Patel, P; Schumacher, D; Stephens, R; Tsui, Y; Ma, T

    2007-12-07

    Experimental results from copper cones irradiated with ultra-intense laser light are presented. Spatial images and total yields of Cu K{sub {alpha}} fluorescence were measured as a function of the laser focusing properties. The fluorescence emission extends into the cone approximately 300 {micro}m from the cone tip and cannot be explained by ray tracing including cone wall absorption. In addition the total fluorescence yield from cones is an order of magnitude higher than for equivalent mass foil targets. Indications are that the physics of the laser cone interaction is dominated by preplasma created from the long duration, low energy pre-pulse from the laser.

  1. Restoration of cone vision in the CNGA3-/- mouse model of congenital complete lack of cone photoreceptor function.

    PubMed

    Michalakis, Stylianos; Mühlfriedel, Regine; Tanimoto, Naoyuki; Krishnamoorthy, Vidhyasankar; Koch, Susanne; Fischer, M Dominik; Becirovic, Elvir; Bai, Lin; Huber, Gesine; Beck, Susanne C; Fahl, Edda; Büning, Hildegard; Paquet-Durand, François; Zong, Xiangang; Gollisch, Tim; Biel, Martin; Seeliger, Mathias W

    2010-12-01

    Congenital absence of cone photoreceptor function is associated with strongly impaired daylight vision and loss of color discrimination in human achromatopsia. Here, we introduce viral gene replacement therapy as a potential treatment for this disease in the CNGA3(-/-) mouse model. We show that such therapy can restore cone-specific visual processing in the central nervous system even if cone photoreceptors had been nonfunctional from birth. The restoration of cone vision was assessed at different stages along the visual pathway. Treated CNGA3(-/-) mice were able to generate cone photoreceptor responses and to transfer these signals to bipolar cells. In support, we found morphologically that treated cones expressed regular cyclic nucleotide-gated (CNG) channel complexes and opsins in outer segments, which previously they did not. Moreover, expression of CNGA3 normalized cyclic guanosine monophosphate (cGMP) levels in cones, delayed cone cell death and reduced the inflammatory response of Müller glia cells that is typical of retinal degenerations. Furthermore, ganglion cells from treated, but not from untreated, CNGA3(-/-) mice displayed cone-driven, light-evoked, spiking activity, indicating that signals generated in the outer retina are transmitted to the brain. Finally, we demonstrate that this newly acquired sensory information was translated into cone-mediated, vision-guided behavior.

  2. Residual Foveal Cone Structure in CNGB3-Associated Achromatopsia

    PubMed Central

    Langlo, Christopher S.; Patterson, Emily J.; Higgins, Brian P.; Summerfelt, Phyllis; Razeen, Moataz M.; Erker, Laura R.; Parker, Maria; Collison, Frederick T.; Fishman, Gerald A.; Kay, Christine N.; Zhang, Jing; Weleber, Richard G.; Yang, Paul; Wilson, David J.; Pennesi, Mark E.; Lam, Byron L.; Chiang, John; Chulay, Jeffrey D.; Dubra, Alfredo; Hauswirth, William W.; Carroll, Joseph

    2016-01-01

    Purpose Congenital achromatopsia (ACHM) is an autosomal recessive disorder in which cone function is absent or severely reduced. Gene therapy in animal models of ACHM have shown restoration of cone function, though translation of these results to humans relies, in part, on the presence of viable cone photoreceptors at the time of treatment. Here, we characterized residual cone structure in subjects with CNGB3-associated ACHM. Methods High-resolution imaging (optical coherence tomography [OCT] and adaptive optics scanning light ophthalmoscopy [AOSLO]) was performed in 51 subjects with CNGB3-associated ACHM. Peak cone density and inter-cone spacing at the fovea was measured using split-detection AOSLO. Foveal outer nuclear layer thickness was measured in OCT images, and the integrity of the photoreceptor layer was assessed using a previously published OCT grading scheme. Results Analyzable images of the foveal cones were obtained in 26 of 51 subjects, with nystagmus representing the major obstacle to obtaining high-quality images. Peak foveal cone density ranged from 7,273 to 53,554 cones/mm2, significantly lower than normal (range, 84,733–234,391 cones/mm2), with the remnant cones being either contiguously or sparsely arranged. Peak cone density was correlated with OCT integrity grade; however, there was overlap of the density ranges between OCT grades. Conclusions The degree of residual foveal cone structure varies greatly among subjects with CNGB3-associated ACHM. Such measurements may be useful in estimating the therapeutic potential of a given retina, providing affected individuals and physicians with valuable information to more accurately assess the risk-benefit ratio as they consider enrolling in experimental gene therapy trials. (www.clinicaltrials.gov, NCT01846052.) PMID:27479814

  3. Fatty Acid Transport Protein 4 (FATP4) Prevents Light-Induced Degeneration of Cone and Rod Photoreceptors by Inhibiting RPE65 Isomerase

    PubMed Central

    Li, Songhua; Lee, Jungsoo; Zhou, Yongdong; Gordon, William C.; Hill, James M.; Bazan, Nicolas G.; Miner, Jeffrey H.; Jin, Minghao

    2013-01-01

    While Rhodopsin is essential for sensing light for vision, it also mediates light-induced apoptosis of photoreceptors in mouse. RPE65, which catalyzes isomerization of all-trans retinyl fatty acid esters to 11-cis retinol (11cROL) in the visual cycle, controls the rhodopsin regeneration rate and photoreceptor susceptibility to light-induced degeneration. Mutations in RPE65 have been linked to blindness in affected children. Despite such importance, the mechanism that regulates RPE65 function remains unclear. Through unbiased expression screening of a bovine retinal pigment epithelium (RPE) cDNA library, we have identified elongation of very long-chain fatty acids-like 1 (ELOVL1) and fatty acid transport protein 4 (FATP4), which each have very long-chain fatty acid acyl-CoA synthetase (VLCFA-ACS) activity, as negative regulators of RPE65. We found that the VLCFA derivative lignoceroyl (C24:0)-CoA inhibited synthesis of 11cROL, whereas palmitoyl (C16:0)-CoA promoted synthesis of 11cROL. We further found that competition of FATP4 with RPE65 for the substrate of RPE65 was also involved in the mechanisms by which FATP4 inhibits synthesis of 11cROL. FATP4 was predominantly expressed in RPE, and the FATP4-deficient RPE showed significantly higher isomerase activity. Consistent with these results, the regeneration rate of 11-cis retinaldehyde and the recovery rate for rod light sensitivity were faster in FATP4-deficient mice than wild-type mice. Moreover, FATP4-deficient mice displayed increased accumulation of the cytotoxic all-trans retinaldehyde and hyper susceptibility to light-induced photoreceptor degeneration. Our findings demonstrate that ELOVL1, FATP4, and their products comprise the regulatory elements of RPE65 and play important roles in protecting photoreceptors from degeneration induced by light damage. PMID:23407971

  4. Lighting.

    SciTech Connect

    United States. Bonneville Power Administration.

    1992-09-01

    Since lighting accounts for about one-third of the energy used in commercial buildings, there is opportunity to conserve. There are two ways to reduce lighting energy use: modify lighting systems so that they used less electricity and/or reduce the number of hours the lights are used. This booklet presents a number of ways to do both. Topics covered include: reassessing lighting levels, reducing lighting levels, increasing bulb & fixture efficiency, using controls to regulate lighting, and taking advantage of daylight.

  5. 2017 Eclipse Shadow Cones

    NASA Image and Video Library

    A solar eclipse occurs when the Moon's shadow falls on the Earth. The shadow comprises two concentric cones called the umbra and the penumbra. Within the smaller, central umbra, the Sun is complete...

  6. HSURIA Cone Centration.

    DTIC Science & Technology

    1981-09-01

    laser. b. Interferometer configuration. This configuration (Fig. 4) uses a Twyman -Green interferometer to measure the cone centration for comparison...autocollimator. The interferometer mode, as was explained in Section Ill-l, gave very little information about the alignment of the cone. c. Physical...the camera turning flat (5) must be removed and the centration sensor laser is used. The interferometer laser is turned off. For the interferometer

  7. Neuroprotectin D1 is synthesized in the cone photoreceptor cell line 661W and elicits protection against light-induced stress.

    PubMed

    Kanan, Y; Gordon, W C; Mukherjee, P K; Bazan, N G; Al-Ubaidi, M R

    2015-03-01

    Docosahexaenoic acid (DHA), an omega-3 fatty acid family member, is obtained by diet or synthesized from dietary essential omega-3 linolenic acid and delivered systemically to the choriocapillaris, from where it is taken up by the retinal pigment epithelium (RPE). DHA is then transported to the inner segments of photoreceptors, where it is incorporated in phospholipids during the biogenesis of outer segment disk and plasma membranes. As apical photoreceptor disks are gradually shed and phagocytized by the RPE, DHA is retrieved and recycled back to photoreceptor inner segments for reassembly into new disks. Under uncompensated oxidative stress, the docosanoid neuroprotectin D1 (NPD1), a potent mediator derived from DHA, is formed by the RPE and displays its bioactivity in an autocrine and paracrine fashion. The purpose of this study was to determine whether photoreceptors have the ability to synthesize NPD1, and whether or not this lipid mediator exerts bioactivity on these cells. For this purpose, 661W cells (mouse-derived photoreceptor cells) were used. First we asked whether these cells have the ability to form NPD1 by incubating cells with deuterium (d4)-labeled DHA exposed to dark and bright light treatments, followed by LC-MS/MS-based lipidomic analysis to identify and quantify d4-NPD1. The second question pertains to the potential bioactivity of these lipids. Therefore, cells were incubated with 9-cis-retinal in the presence of bright light that triggers cell damage and death. Following 9-cis-retinal loading, DHA, NPD1, or vehicle were added to the media and the 661W cells maintained either in darkness or under bright light. DHA and NPD1 were then quantified in cells and media. Regardless of lighting conditions, 661W cells acquired DHA from the media and synthesized 4-9 times as much d4-NPD1 under bright light treatment in the absence and presence of 9-cis-retinal compared to cells in darkness. Viability assays of 9-cis-retinal-treated cells demonstrated that

  8. Hurricane track forecast cones from fluctuations

    PubMed Central

    Meuel, T.; Prado, G.; Seychelles, F.; Bessafi, M.; Kellay, H.

    2012-01-01

    Trajectories of tropical cyclones may show large deviations from predicted tracks leading to uncertainty as to their landfall location for example. Prediction schemes usually render this uncertainty by showing track forecast cones representing the most probable region for the location of a cyclone during a period of time. By using the statistical properties of these deviations, we propose a simple method to predict possible corridors for the future trajectory of a cyclone. Examples of this scheme are implemented for hurricane Ike and hurricane Jimena. The corridors include the future trajectory up to at least 50 h before landfall. The cones proposed here shed new light on known track forecast cones as they link them directly to the statistics of these deviations. PMID:22701776

  9. Hurricane track forecast cones from fluctuations.

    PubMed

    Meuel, T; Prado, G; Seychelles, F; Bessafi, M; Kellay, H

    2012-01-01

    Trajectories of tropical cyclones may show large deviations from predicted tracks leading to uncertainty as to their landfall location for example. Prediction schemes usually render this uncertainty by showing track forecast cones representing the most probable region for the location of a cyclone during a period of time. By using the statistical properties of these deviations, we propose a simple method to predict possible corridors for the future trajectory of a cyclone. Examples of this scheme are implemented for hurricane Ike and hurricane Jimena. The corridors include the future trajectory up to at least 50 h before landfall. The cones proposed here shed new light on known track forecast cones as they link them directly to the statistics of these deviations.

  10. The absolute threshold of cone vision

    PubMed Central

    Koeing, Darran; Hofer, Heidi

    2013-01-01

    We report measurements of the absolute threshold of cone vision, which has been previously underestimated due to sub-optimal conditions or overly strict subjective response criteria. We avoided these limitations by using optimized stimuli and experimental conditions while having subjects respond within a rating scale framework. Small (1′ fwhm), brief (34 msec), monochromatic (550 nm) stimuli were foveally presented at multiple intensities in dark-adapted retina for 5 subjects. For comparison, 4 subjects underwent similar testing with rod-optimized stimuli. Cone absolute threshold, that is, the minimum light energy for which subjects were just able to detect a visual stimulus with any response criterion, was 203 ± 38 photons at the cornea, ∼0.47 log units lower than previously reported. Two-alternative forced-choice measurements in a subset of subjects yielded consistent results. Cone thresholds were less responsive to criterion changes than rod thresholds, suggesting a limit to the stimulus information recoverable from the cone mosaic in addition to the limit imposed by Poisson noise. Results were consistent with expectations for detection in the face of stimulus uncertainty. We discuss implications of these findings for modeling the first stages of human cone vision and interpreting psychophysical data acquired with adaptive optics at the spatial scale of the receptor mosaic. PMID:21270115

  11. Ideal illuminants for rod/L-cone color

    NASA Astrophysics Data System (ADS)

    McCann, John J.

    2006-01-01

    Humans see multicolor complex images with illuminants that have very low amounts of 400 to 580nm light when there is enough long-wave light greater than 590nm. Interactions between rods and long-wave (L) cones generate these colors. They are observed when there is insufficient light for a threshold response from M- and S-cones. This paper measures the spectral emission of a wood fire and a wax candle and it compares these low-color temperature spectral radiant exitances with the sensitivities of rods and long-wave cones. The paper reviews some of the literature on the evolution of human cone pigments and the early use of fire by hominids.

  12. Rod-cone interactions and the temporal impulse response of the cone pathway

    PubMed Central

    Zele, Andrew J.; Cao, Dingcai; Pokorny, Joel

    2008-01-01

    Dark-adapted rods suppress cone-mediated flicker detection. This study evaluates the effect that rod activity has on cone temporal processing by investigating whether rod mediated suppression changes the cone pathway impulse response function, regardless of the form of the temporal signal. Stimuli were generated with a 2-channel photostimulator that has four primaries for the central field and four primaries for the surround. Cone pathway temporal impulse response functions were derived from temporal contrast sensitivity data with periodic stimuli, and from two-pulse discrimination data in which pairs of briefly pulsed stimuli were presented successively at a series of stimulus onset asynchronies. Dark-adapted rods altered the amplitude and timing of cone pathway temporal impulse response functions, irrespective of whether they were derived from measurements with temporally periodic stimuli or in a brief presentation temporal resolution task with pulsed stimuli. Rod-cone interactions are a fundamental operation in visual temporal processing under mesopic light levels, acting to decrease the temporal bandwidth of the visual system. PMID:18486960

  13. The Na(+)/Ca(2+), K(+) exchanger 2 modulates mammalian cone phototransduction.

    PubMed

    Sakurai, Keisuke; Vinberg, Frans; Wang, Tian; Chen, Jeannie; Kefalov, Vladimir J

    2016-09-01

    Calcium ions (Ca(2+)) modulate the phototransduction cascade of vertebrate cone photoreceptors to tune gain, inactivation, and light adaptation. In darkness, the continuous current entering the cone outer segment through cGMP-gated (CNG) channels is carried in part by Ca(2+), which is then extruded back to the extracellular space. The mechanism of Ca(2+) extrusion from mammalian cones is not understood. The dominant view has been that the cone-specific isoform of the Na(+)/Ca(2+), K(+) exchanger, NCKX2, is responsible for removing Ca(2+) from their outer segments. However, indirect evaluation of cone function in NCKX2-deficient (Nckx2(-/-)) mice by electroretinogram recordings revealed normal photopic b-wave responses. This unexpected result suggested that NCKX2 may not be involved in the Ca(2+) homeostasis of mammalian cones. To address this controversy, we examined the expression of NCKX2 in mouse cones and performed transretinal recordings from Nckx2(-/-) mice to determine the effect of NCKX2 deletion on cone function directly. We found that Nckx2(-/-) cones exhibit compromised phototransduction inactivation, slower response recovery and delayed background adaptation. We conclude that NCKX2 is required for the maintenance of efficient Ca(2+) extrusion from mouse cones. However, surprisingly, Nckx2(-/-) cones adapted normally in steady background light, indicating the existence of additional Ca(2+)-extruding mechanisms in mammalian cones.

  14. Type 3 deiodinase, a thyroid-hormone inactivating enzyme, controls survival and maturation of cone photoreceptors

    PubMed Central

    Ng, Lily; Lyubarsky, Arkady; Nikonov, Sergei S.; Ma, Michelle; Srinivas, Maya; Kefas, Benjamin; St.Germain, Donald L.; Hernandez, Arturo; Pugh, Edward N.; Forrest, Douglas

    2010-01-01

    Maturation of the mammalian nervous system requires adequate provision of thyroid hormone and mechanisms that enhance tissue responses to the hormone. Here, we report that the development of cones, the photoreceptors for daylight and color vision, requires protection from thyroid hormone by type 3 deiodinase, a thyroid hormone-inactivating enzyme. Type 3 deiodinase, encoded by Dio3, is expressed in the immature mouse retina. In Dio3−/− mice, ~80% of cones are lost through neonatal cell death. Cones that express opsin photopigments for response to both short (S) and medium-long (M) wavelength light are lost. Rod photoreceptors, which mediate dim light vision, remain largely intact. Excessive thyroid hormone in wild type pups also eliminates cones. Cone loss is mediated by cone-specific thyroid hormone receptor β2 (TRβ2) as deletion of TRβ2 rescues cones in Dio3−/− mice. However, rescued cones respond to short but not longer wavelength light because TRβ2 under moderate hormonal stimulation normally induces M opsin and controls the patterning of M and S opsins over the retina. The results suggest that type 3 deiodinase limits hormonal exposure of the cone to levels that safeguard both cone survival and the patterning of opsins that is required for cone function. PMID:20203194

  15. Ultra-short pulses to signal neuronal growth cone machinery

    NASA Astrophysics Data System (ADS)

    Mathew, Manoj; Amat-Roldan, Ivan; Andres, Rosa; Cormack, Iain G.; Artigas, David; Soriano, Eduardo; Loza-Alvarez, Pablo

    2007-02-01

    Measurable change in the sensory motor machinery of growth cones are induced by non contact femtosecond laser. The focused laser beam with an average power of 3 mW was positioned at some distance away from the closest fillopodia of cortical neurons from primary cell cultures (mice E15). By identifying a set of preliminary parameters we were able to statistically analyze the phenomenological behavior of the fillopodia and classify the effects different conditions of laser light has on the growth cone. Results show that fillopodia become significantly biased towards the focused femtosecond laser light. The same experiment performed with continuous wave (CW) produced results which were indistinguishable from the case where there is no laser light present (placebo condition) indicating no clear effects of the CW laser light on the fillopodia at a distance. These findings show the potential for ultrashort pulsed light to become a new type of pathfinding cue for neuronal growth cones.

  16. Formation of shatter cones in MEMIN impact experiments

    NASA Astrophysics Data System (ADS)

    Wilk, J.; Kenkmann, T.

    2016-08-01

    Shatter cones are the only macroscopic feature considered as evidence for shock metamorphism. Their presence is diagnostic for the discovery and verification of impact structures. The occurrence of shatter cones is heterogeneous throughout the crater record and their geometry can diverge from the typical cone shape. The precise formation mechanism of shatter cones is still not resolved. In this study, we aim at better constraining the boundary conditions of shatter cone formation in impact experiments and test a novel approach to qualitatively and quantitatively describe shatter cone geometries by white light interferometry. We recovered several ejected fragments from MEMIN cratering experiments that show slightly curved, striated surfaces and conical geometries with apices of 36°-52°. These fragments fulfilling the morphological criteria of shatter cones were found in experiments with 20-80 cm sized target cubes of sandstone, quartzite and limestone, but not in highly porous tuff. Targets were impacted by aluminum, steel, and iron meteorite projectiles at velocities of 4.6-7.8 km s-1. The projectile sizes ranged from 2.5-12 mm in diameter and produced experimental peak pressures of up to 86 GPa. In experiments with lower impact velocities shatter cones could not be found. A thorough morphometric analysis of the experimentally generated shatter cones was made with 3D white light interferometry scans at micrometer accuracy. SEM analysis of the surfaces of recovered fragments showed vesicular melt films alternating with smoothly polished surfaces. We hypothesize that the vesicular melt films predominantly form at strain releasing steps and suggest that shatter cones are probably mixed mode fractures.

  17. The cone dysfunction syndromes

    PubMed Central

    Aboshiha, Jonathan; Dubis, Adam M; Hardcastle, Alison J; Michaelides, Michel

    2016-01-01

    The cone dysfunction syndromes are a heterogeneous group of inherited, predominantly stationary retinal disorders characterised by reduced central vision and varying degrees of colour vision abnormalities, nystagmus and photophobia. This review details the following conditions: complete and incomplete achromatopsia, blue-cone monochromatism, oligocone trichromacy, bradyopsia and Bornholm eye disease. We describe the clinical, psychophysical, electrophysiological and imaging findings that are characteristic to each condition in order to aid their accurate diagnosis, as well as highlight some classically held notions about these diseases that have come to be challenged over the recent years. The latest data regarding the genetic aetiology and pathological changes observed in the cone dysfunction syndromes are discussed, and, where relevant, translational avenues of research, including completed and anticipated interventional clinical trials, for some of the diseases described herein will be presented. Finally, we briefly review the current management of these disorders. PMID:25770143

  18. Insulin Receptor Signaling in Cones*

    PubMed Central

    Rajala, Ammaji; Dighe, Radhika; Agbaga, Martin-Paul; Anderson, Robert E.; Rajala, Raju V.S.

    2013-01-01

    In humans, age-related macular degeneration and diabetic retinopathy are the most common disorders affecting cones. In retinitis pigmentosa (RP), cone cell death precedes rod cell death. Systemic administration of insulin delays the death of cones in RP mouse models lacking rods. To date there are no studies on the insulin receptor signaling in cones; however, mRNA levels of IR signaling proteins are significantly higher in cone-dominant neural retina leucine zipper (Nrl) knock-out mouse retinas compared with wild type rod-dominant retinas. We previously reported that conditional deletion of the p85α subunit of phosphoinositide 3-kinase (PI3K) in cones resulted in age-related cone degeneration, and the phenotype was not rescued by healthy rods, raising the question of why cones are not protected by the rod-derived cone survival factors. Interestingly, systemic administration of insulin has been shown to delay the death of cones in mouse models of RP lacking rods. These observations led to the hypothesis that cones may have their own endogenous neuroprotective pathway, or rod-derived cone survival factors may be signaled through cone PI3K. To test this hypothesis we generated p85α−/−/Nrl−/− double knock-out mice and also rhodopsin mutant mice lacking p85α and examined the effect of the p85α subunit of PI3K on cone survival. We found that the rate of cone degeneration is significantly faster in both of these models compared with respective mice with competent p85α. These studies suggest that cones may have their own endogenous PI3K-mediated neuroprotective pathway in addition to the cone viability survival signals derived from rods. PMID:23673657

  19. A mouse model for studying cone photoreceptor pathologies.

    PubMed

    Samardzija, Marijana; Caprara, Christian; Heynen, Severin R; Willcox DeParis, Sarah; Meneau, Isabelle; Traber, Ghislaine; Agca, Cavit; von Lintig, Johannes; Grimm, Christian

    2014-07-17

    Due to the low abundance of cone photoreceptors in the mouse retina and the scarcity of alternative animal models, little is known about mechanisms of cone degeneration. Nrl knockout mice develop exclusively the cone-type of photoreceptors. However, the cone photoreceptor layer in Nrl(-/-) mice displays an irregular morphology with severe rosette formation. Retinas of Rpe65(-/-);Nrl(-/-) mice have no rosettes due to the lack of 11-cis-retinal, but also are not functional. To develop a model with a functional all-cone retina that is morphologically well structured, we generated R91W;Nrl(-/-) double-mutant mice, which express a hypomorphic Rpe65 allele (R91W). The following analyses were used to characterize the R91W;Nrl(-/-)mice: morphology by light and electron microscopy, protein distribution by immunofluorescence, cone function by electroretinography and optomotor response, RNA levels by RT-PCR, and chromophore levels by HPLC. Cone degeneration was assessed in R91W;Nrl(-/-) mice treated with MNU, and in triple R91W;Nrl(-/-);Cpfl1 and quadruple R91W;Nrl(-/-);Cpfl1;rd10 mutant mice. The all-cone retina of R91W;Nrl(-/-) mice is functional and relatively stable with only very slow age-related degeneration. Using triple and quadruple mutant mice, or a chemical treatment, we demonstrated that cone degeneration could be induced and analyzed in these mice. The reduced levels of visual chromophore prevented rosette formation and sustained function in the R91W;Nrl(-/-) retina. Thus, the R91W;Nrl(-/-) mouse allows study of the etiology of diseases related to cone degeneration in a "morphologically intact" and functional all-cone photoreceptor retina. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  20. The spatial arrangement of cones in the primate fovea

    NASA Astrophysics Data System (ADS)

    Mollon, J. D.; Bowmaker, J. K.

    1992-12-01

    THE retinae of Old World primates contain three classes of light-sensitive cone, which exhibit peak absorption in different spectral regions1-4. But how are the different types of cone arranged in the hexagonal mosaic of the fovea? This question has often been answered with artists' impressions5-7, but never with direct measurements. Staining for antibodies specific to the short-wave photopigment has revealed a sparse, semiregular array of cones8; but nothing is known about the arrangement of the more numerous long- and middle-wave cones. Are they randomly distributed, with chance aggregations of one type, as Hartridge postulated in these columns nearly 50 years ago9,10? Or do they exhibit a regular alternation, recalling the systematic mosaics seen in some non-mammalian species6,11? Or, conversely, is there positive clumping of particular cone types, as might be expected if local patches of cones were descended from a single precursor cell? We have made direct microspectrophotometric measurements of patches of foveal retina from Old World monkeys, and report here that the distribu tion of long- and middle-wave cones is locally random. These two cone types are present in almost equal numbers, and not in the ratio of 2:1 that has been postulated for the human fovea.

  1. Cone photopigment in older subjects: decreased optical density in early age-related macular degeneration

    NASA Astrophysics Data System (ADS)

    Elsner, Ann E.; Burns, Stephen A.; Weiter, John J.

    2002-01-01

    We measured changes to cone photoreceptors in patients with early age-related macular degeneration. The data of 53 patients were compared with normative data for color matching measurements of long- and middle-wavelength-sensitive cones in the central macula. A four-parameter model quantified cone photopigment optical density and kinetics. Cone photopigment optical density was on average less for the patients than for normal subjects and was uncorrelated with visual acuity. More light was needed to reduce the photopigment density by 50% in the steady state for patients. These results imply that cone photopigment optical density is reduced by factors other than slowed kinetics.

  2. Shatter Cones: (Mis)understood?

    NASA Astrophysics Data System (ADS)

    Osinski, G. R.; Ferrière, L.

    2016-08-01

    In this study we provide new observations of shatter cones from several complex impact craters in various target rocks and in different preservation states. We show that shatter cones are present in several stratigraphic settings.

  3. Optics of cone photoreceptors in the chicken (Gallus gallus domesticus).

    PubMed

    Wilby, David; Toomey, Matthew B; Olsson, Peter; Frederiksen, Rikard; Cornwall, M Carter; Oulton, Ruth; Kelber, Almut; Corbo, Joseph C; Roberts, Nicholas W

    2015-10-06

    Vision is the primary sensory modality of birds, and its importance is evident in the sophistication of their visual systems. Coloured oil droplets in the cone photoreceptors represent an adaptation in the avian retina, acting as long-pass colour filters. However, we currently lack understanding of how the optical properties and morphology of component structures (e.g. oil droplet, mitochondrial ellipsoid and outer segment) of the cone photoreceptor influence the transmission of light into the outer segment and the ultimate effect they have on receptor sensitivity. In this study, we use data from microspectrophotometry, digital holographic microscopy and electron microscopy to inform electromagnetic models of avian cone photoreceptors to quantitatively investigate the integrated optical function of the cell. We find that pigmented oil droplets primarily function as spectral filters, not light collection devices, although the mitochondrial ellipsoid improves optical coupling between the inner segment and oil droplet. In contrast, unpigmented droplets found in violet-sensitive cones double sensitivity at its peak relative to other cone types. Oil droplets and ellipsoids both narrow the angular sensitivity of single cone photoreceptors, but not as strongly as those in human cones.

  4. Optics of cone photoreceptors in the chicken (Gallus gallus domesticus)

    PubMed Central

    Wilby, David; Toomey, Matthew B.; Olsson, Peter; Frederiksen, Rikard; Cornwall, M. Carter; Oulton, Ruth; Kelber, Almut; Corbo, Joseph C.; Roberts, Nicholas W.

    2015-01-01

    Vision is the primary sensory modality of birds, and its importance is evident in the sophistication of their visual systems. Coloured oil droplets in the cone photoreceptors represent an adaptation in the avian retina, acting as long-pass colour filters. However, we currently lack understanding of how the optical properties and morphology of component structures (e.g. oil droplet, mitochondrial ellipsoid and outer segment) of the cone photoreceptor influence the transmission of light into the outer segment and the ultimate effect they have on receptor sensitivity. In this study, we use data from microspectrophotometry, digital holographic microscopy and electron microscopy to inform electromagnetic models of avian cone photoreceptors to quantitatively investigate the integrated optical function of the cell. We find that pigmented oil droplets primarily function as spectral filters, not light collection devices, although the mitochondrial ellipsoid improves optical coupling between the inner segment and oil droplet. In contrast, unpigmented droplets found in violet-sensitive cones double sensitivity at its peak relative to other cone types. Oil droplets and ellipsoids both narrow the angular sensitivity of single cone photoreceptors, but not as strongly as those in human cones. PMID:26423439

  5. Reconstruction from cone integral transforms

    NASA Astrophysics Data System (ADS)

    Palamodov, Victor

    2017-10-01

    The paper contains new reconstruction formulas for a function on 3D space from data of its cone integrals with fixed opening and integrable weight. In the case of cone integrals with the (non integrable) weight modelling photometric law, a reconstruction is obtained for the non redundant data of cones with the apex running on a curve.

  6. Cone on Olympus Mons

    NASA Image and Video Library

    2005-10-24

    This image from NASA 2001 Mars Odyssey spacecraft shows just a small part of the eastern flank of Olympus Mons. On the far left side of the image a small volcanic cone can be seen. The shadow helps to identify this feature.

  7. Evolutionary loss of cone photoreception in balaenid whales reveals circuit stability in the mammalian retina.

    PubMed

    Schweikert, Lorian E; Fasick, Jeffry I; Grace, Michael S

    2016-10-01

    The classical understanding of mammalian vision is that it occurs through "duplex" retinae containing both rod and cone photoreceptors, the signals from which are processed through rod- and/or cone-specific signaling pathways. The recent discovery of rod monochromacy in some cetacean lineages provides a novel opportunity to investigate the effects of an evolutionary loss of cone photoreception on retinal organization. Sequence analysis of right whale (Eubalaena glacialis; family Balaenidae) cDNA derived from long-wavelength sensitive (LWS) cone opsin mRNA identified several mutations in the opsin coding sequence, suggesting the loss of cone cell function, but maintenance of non-photosensitive, cone opsin mRNA-expressing cells in the retina. Subsequently, we investigated the retina of the closely related bowhead whale (Balaena mysticetus; family Balaenidae) to determine how the loss of cone-mediated photoreception affects light signaling pathways in the retina. Anti-opsin immunofluorescence demonstrated the total loss of cone opsin expression in B. mysticetus, whereas light microscopy, transmission electron microscopy, and bipolar cell (protein kinase C-α [PKC-α] and recoverin) immunofluorescence revealed the maintenance of cone soma, putative cone pedicles, and both rod and cone bipolar cell types. These findings represent the first immunological and anatomical evidence of a naturally occurring rod-monochromatic mammalian retina, and suggest that despite the loss of cone-mediated photoreception, the associated cone signaling structures (i.e., cone synapses and cone bipolar cells) may be maintained for multichannel rod-based signaling in balaenid whales. J. Comp. Neurol. 524:2873-2885, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  8. Stiles—Crawford effect and the bleaching of cone pigments

    PubMed Central

    Coble, J. R.; Rushton, W. A. H.

    1971-01-01

    1. The efficiency of light entering the eye through various points in the pupil (Stiles—Crawford effect) was studied using two criteria: (a) visual brightness judged by flicker fusion and (b) the rate of cone pigment bleaching measured by reflexion densitometry. 2. Both measurements were made in the same apparatus with the same geometry of presentation and both gave the same Stiles—Crawford effect. 3. This suggests that the densitometer measures pigment deep in the outer segments of the cones where light is absorbed for vision. 4. Foveal cones seem all to point in the same direction, since the fraction of pigment bleached by light entering the pupil at any one point is the same when measured by light entering anywhere. PMID:5571926

  9. Selective cone photoreceptor injury in acute macular neuroretinopathy.

    PubMed

    Hansen, Sean O; Cooper, Robert F; Dubra, Alfredo; Carroll, Joseph; Weinberg, David V

    2013-09-01

    To evaluate retinal structural and functional abnormalities in a patient with acute macular neuroretinopathy. An adaptive optics scanning light ophthalmoscope was used to image the photoreceptor mosaic and assess rod and cone structure. Spectral-domain optical coherence tomography was used to examine retinal lamination. Microperimetry was used to assess function across the macula. Microperimetry showed reduced function of localized areas within retinal lesions corresponding to subjective scotomas. Spectral-domain optical coherence tomography imaging revealed attenuation of two outer retinal bands typically thought to reflect photoreceptor structure. Adaptive optics scanning light ophthalmoscope images of the photoreceptor mosaic revealed a heterogeneous presentation within these lesions. There were areas containing non-waveguiding cones and other areas of decreased cone density where the remaining rods had expanded to fill in the vacant space. Within these lesions, cone densities were shown to be significantly lower than eccentricity-matched areas of normal retina, as well as accepted histologic measurements. A 6-month follow-up revealed no change in rod or cone structure. Imaging of acute macular neuroretinopathy using an adaptive optics scanning light ophthalmoscope shows a preferential disruption of cone photoreceptor structure within the region of decreased retinal sensitivity (as measured by microperimetry). Adaptive optics-based imaging tools provide a noninvasive way to assess photoreceptor structure at a level of detail that is not resolved by use of conventional spectral-domain optical coherence tomography or other clinical measures.

  10. Co-expression of murine opsins facilitates identifying the site of cone adaptation.

    PubMed

    Ekesten, Björn; Gouras, Peter; Hargitai, Janos

    2002-01-01

    Murine cones contain two opsins in the same cone, one ultraviolet (UV) and the other middle-wavelength sensitive (M). A long-wavelength flash only affecting M-opsin suppresses the cone electroretinogram (ERG) produced by light absorption of UV-cone opsin raising the hypothesis that activation of M-cone opsin suppresses UV-cone opsin responses in the same cone. Here we show that pharmacologic blockade of synaptic transmission in the superfused murine retina, which eliminates interaction from second-order neurons, fails to prevent suppression of the UV-opsin driven pathway by long-wavelength stimuli. This proves that the antagonism must be occurring in the same cone, co-expressing both opsins. Our results show that UV-opsin suppression successively ceases in presence of the M-opsin activating background light, which implies that cone light adaptation is controlled at the opsin stage, before activation of transducin. It also reveals the time course of a transient desensitization of cones due to post-opsin factors in the transduction cascade.

  11. Combination of rod and cone inputs in parasol ganglion cells of the magnocellular pathway

    PubMed Central

    Cao, Dingcai; Lee, Barry B.; Sun, Hao

    2010-01-01

    This study investigates how rod and cone inputs are combined in the magnocellular (MC) pathway in the mesopic luminance range, when both rods and cones are active. Responses of parafoveal MC ganglion cells from macaque retina were measured as a function of temporal frequency (0.62–20 Hz) or contrast (0.05–0.55) at mesopic light levels (0.2, 2, 20, and 200 td). Stimuli were of three modulation types: (1) isolated rod stimuli (only rod signals were modulated), (2) isolated cone stimuli (only cone luminance signals from long- and middle-wavelength sensitive cones were modulated), and (3) combined rod and cone stimuli (both rod and cone luminance signals were modulated in phase, as with conventional stimuli). The results showed that under mesopic conditions, the relative rod and cone inputs to the MC cells varied with light level and they are combined linearly prior to saturation. Further, rod contrast gain is relatively stable over the mesopic range while cone contrast gain increased with light level. Finally, the measured rod and cone inputs are consistent with the measured human temporal contrast sensitivity functions under comparable stimulation conditions. PMID:20884499

  12. Light

    NASA Astrophysics Data System (ADS)

    Vernon, C. G.

    2016-09-01

    Preface; 1. Historical; 2. Waves and wave-motion; 3. The behaviour of ripples; 4. The behaviour of light; 5. Refraction through glass blocks and prisms; 6. The imprinting of curvatures; 7. Simple mathematical treatment; 8. More advanced mathematical treatment; 9. The velocity of light; 10. The spectrum and colour; 11. Geometrical optics; 12. The eye and optical instruments; 13. Sources of light; 14. Interference, diffraction and polarisation; 15. Suggestions for class experiments; Index.

  13. Directionality of Individual Cone Photoreceptors in the Parafoveal Region

    PubMed Central

    Morris, Hugh J.; Blanco, Leonardo; Codona, Johanan L.; Li, Simone; Choi, Stacey S.; Doble, Nathan

    2015-01-01

    The pointing direction of cone photoreceptors can be inferred from the Stiles-Crawford Effect of the First Kind (SCE-I) measurement. Healthy retinas have tightly packed cones with a SCE-I function peak either centered in the pupil or with a slight nasal bias. Various retinal pathologies can change the profile of the SCE-I function implying that the arrangement or the light capturing properties of the cone photoreceptors are affected. Measuring the SCE-I may reveal early signs of photoreceptor change before actual cell apoptosis occurs. In vivo retinal imaging with adaptive optics (AO) was used to measure the pointing direction of individual cones at eight retinal locations in four control human subjects. Retinal images were acquired by translating an aperture in the light delivery arm through 19 different locations across a subject’s entrance pupil. Angular tuning properties of individual cones were calculated by fitting a Gaussian to the reflected intensity profile of each cone projected onto the pupil. Results were compared to those from an accepted psychophysical SCE-I measurement technique. The maximal difference in cone directionality of an ensemble of cones, ρ̄, between the major and minor axes of the Gaussian fit was 0.05 versus 0.29 mm−2 in one subject. All four subjects were found to have a mean nasal bias of 0.81 mm with a standard deviation of ±0.30 mm in the peak position at all retinal locations with mean ρ̄ value decreasing by 23% with increasing retinal eccentricity. Results show that cones in the parafoveal region converge towards the center of the pupillary aperture, confirming the anterior pointing alignment hypothesis. PMID:26494187

  14. Cone photoreceptor contributions to noise and correlations in the retinal output.

    PubMed

    Ala-Laurila, Petri; Greschner, Martin; Chichilnisky, E J; Rieke, Fred

    2011-09-18

    Transduction and synaptic noise generated in retinal cone photoreceptors determine the fidelity with which light inputs are encoded, and the readout of cone signals by downstream circuits determines whether this fidelity is used for vision. We examined the effect of cone noise on visual signals by measuring its contribution to correlated noise in primate retinal ganglion cells. Correlated noise was strong in the responses of dissimilar cell types with shared cone inputs. The dynamics of cone noise could account for rapid correlations in ganglion cell activity, and the extent of shared cone input could explain correlation strength. Furthermore, correlated noise limited the fidelity with which visual signals were encoded by populations of ganglion cells. Thus, a simple picture emerges: cone noise, traversing the retina through diverse pathways, accounts for most of the noise and correlations in the retinal output and constrains how higher centers exploit signals carried by parallel visual pathways. © 2011 Nature America, Inc. All rights reserved.

  15. Effect of rod–cone interactions on mesopic visual performance mediated by chromatic and luminance pathways

    PubMed Central

    Zele, Andrew J.; Maynard, Michelle L.; Joyce, Daniel S.; Cao, Dingcai

    2014-01-01

    We studied the effect of rod–cone interactions on mesopic visual reaction time (RT). Rod and cone photoreceptor excitations were independently controlled using a four-primary photostimulator. It was observed that (1) lateral rod–cone interactions increase the cone-mediated RTs; (2) the rod–cone interactions are strongest when rod sensitivity is maximal in a dark surround, but weaker with increased rod activity in a light surround; and (3) the presence of a dark surround nonselectively increased the mean and variability of chromatic (+L−M, S-cone) and luminance (L + M + S) RTs independent of the level of rod activity. The results demonstrate that lateral rod–cone interactions must be considered when deriving mesopic luminous efficiency using RT. PMID:24695205

  16. Mouse rods signal through gap junctions with cones

    PubMed Central

    Asteriti, Sabrina; Gargini, Claudia; Cangiano, Lorenzo

    2014-01-01

    Rod and cone photoreceptors are coupled by gap junctions (GJs), relatively large channels able to mediate both electrical and molecular communication. Despite their critical location in our visual system and evidence that they are dynamically gated for dark/light adaptation, the full impact that rod–cone GJs can have on cone function is not known. We recorded the photovoltage of mouse cones and found that the initial level of rod input increased spontaneously after obtaining intracellular access. This process allowed us to explore the underlying coupling capacity to rods, revealing that fully coupled cones acquire a striking rod-like phenotype. Calcium, a candidate mediator of the coupling process, does not appear to be involved on the cone side of the junctional channels. Our findings show that the anatomical substrate is adequate for rod–cone coupling to play an important role in vision and, possibly, in biochemical signaling among photoreceptors. DOI: http://dx.doi.org/10.7554/eLife.01386.001 PMID:24399457

  17. Shatter cones: Diagnostic impact signatures

    NASA Technical Reports Server (NTRS)

    Mchone, J. F.; Dietz, R. S.

    1988-01-01

    Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures).

  18. Shatter cones: Diagnostic impact signatures

    NASA Astrophysics Data System (ADS)

    McHone, J. F.; Dietz, R. S.

    Uniquely fractured target rocks known as shatter cones are associated with more than one half the world's 120 or so presently known impact structures. Shatter cones are a form of tensile rock failure in which a positive conical plug separates from a negative outer cup or mold and delicate ornaments radiating from an apex are preserved on surfaces of both portions. Although distinct, shatter cones are sometimes confused with other striated geologic features such as ventifacts, stylolites, cone-in-cone, slickensides, and artificial blast plumes. Complete cones or solitary cones are rare, occurrences are usually as swarms in thoroughly fractured rock. Shatter cones may form in a zone where an expanding shock wave propagating through a target decays to form an elastic wave. Near this transition zone, the expanding primary wave may strike a pebble or other inhomogeneity whose contrasting transmission properties produce a scattered secondary wave. Interference between primary and secondary scattered waves produce conical stress fields with axes perpendicular to the plane of an advancing shock front. This model supports mechanism capable of producing such shatter cone properties as orientation, apical clasts, lithic dependence, and shock pressure zonation. Although formational mechanics are still poorly understood, shatter cones have become the simplest geologic field criterion for recognizing astroblemes (ancient terrestrial impact structures).

  19. Radon Transform and Light-Cone Distributions

    NASA Astrophysics Data System (ADS)

    Teryaev, O. V.

    2016-08-01

    The relevance of Radon transform for generalized and transverse momentum dependent parton distributions is discussed. The new application for conditional (fracture) parton distributions and dihadron fragmentation functions is suggested.

  20. Spectral Tuning of Deep Red Cone Pigments†

    PubMed Central

    Amora, Tabitha L.; Ramos, Lavoisier S.; Galan, Jhenny F.; Birge, Robert R.

    2008-01-01

    Visual pigments are G-protein-coupled receptors that provide a critical interface between organisms and their external environment. Natural selection has generated vertebrate pigments that absorb light from the far-UV (360 nm) to the deep red (630 nm) while using a single chromophore, in either the A1 (11-cis-retinal) or A2 (11-cis-3,4-dehydroretinal) form. The fact that a single chromophore can be manipulated to have an absorption maximum across such an extended spectral region is remarkable. The mechanisms of wavelength regulation remain to be fully revealed, and one of the least well-understood mechanisms is that associated with the deep red pigments. We investigate theoretically the hypothesis that deep red cone pigments select a 6-s-trans conformation of the retinal chromophore ring geometry. This conformation is in contrast to the 6-s-cis ring geometry observed in rhodopsin and, through model chromophore studies, the vast majority of visual pigments. Nomographic spectral analysis of 294 A1 and A2 cone pigment literature absorption maxima indicates that the selection of a 6-s-trans geometry red shifts M/LWS A1 pigments by ~1500 cm−1 (~50 nm) and A2 pigments by ~2700 cm−1 (~100 nm). The homology models of seven cone pigments indicate that the deep red cone pigments select 6-s-trans chromophore conformations primarily via electrostatic steering. Our results reveal that the generation of a 6-s-trans conformation not only achieves a significant red shift but also provides enhanced stability of the chromophore within the deep red cone pigment binding sites. PMID:18370404

  1. Spectral tuning of deep red cone pigments.

    PubMed

    Amora, Tabitha L; Ramos, Lavoisier S; Galan, Jhenny F; Birge, Robert R

    2008-04-22

    Visual pigments are G-protein-coupled receptors that provide a critical interface between organisms and their external environment. Natural selection has generated vertebrate pigments that absorb light from the far-UV (360 nm) to the deep red (630 nm) while using a single chromophore, in either the A1 (11- cis-retinal) or A2 (11- cis-3,4-dehydroretinal) form. The fact that a single chromophore can be manipulated to have an absorption maximum across such an extended spectral region is remarkable. The mechanisms of wavelength regulation remain to be fully revealed, and one of the least well-understood mechanisms is that associated with the deep red pigments. We investigate theoretically the hypothesis that deep red cone pigments select a 6- s- trans conformation of the retinal chromophore ring geometry. This conformation is in contrast to the 6- s- cis ring geometry observed in rhodopsin and, through model chromophore studies, the vast majority of visual pigments. Nomographic spectral analysis of 294 A1 and A2 cone pigment literature absorption maxima indicates that the selection of a 6- s- trans geometry red shifts M/LWS A1 pigments by approximately 1500 cm (-1) ( approximately 50 nm) and A2 pigments by approximately 2700 cm (-1) ( approximately 100 nm). The homology models of seven cone pigments indicate that the deep red cone pigments select 6- s- trans chromophore conformations primarily via electrostatic steering. Our results reveal that the generation of a 6- s- trans conformation not only achieves a significant red shift but also provides enhanced stability of the chromophore within the deep red cone pigment binding sites.

  2. Cone rod dystrophies

    PubMed Central

    Hamel, Christian P

    2007-01-01

    Cone rod dystrophies (CRDs) (prevalence 1/40,000) are inherited retinal dystrophies that belong to the group of pigmentary retinopathies. CRDs are characterized by retinal pigment deposits visible on fundus examination, predominantly localized to the macular region. In contrast to typical retinitis pigmentosa (RP), also called the rod cone dystrophies (RCDs) resulting from the primary loss in rod photoreceptors and later followed by the secondary loss in cone photoreceptors, CRDs reflect the opposite sequence of events. CRD is characterized by primary cone involvement, or, sometimes, by concomitant loss of both cones and rods that explains the predominant symptoms of CRDs: decreased visual acuity, color vision defects, photoaversion and decreased sensitivity in the central visual field, later followed by progressive loss in peripheral vision and night blindness. The clinical course of CRDs is generally more severe and rapid than that of RCDs, leading to earlier legal blindness and disability. At end stage, however, CRDs do not differ from RCDs. CRDs are most frequently non syndromic, but they may also be part of several syndromes, such as Bardet Biedl syndrome and Spinocerebellar Ataxia Type 7 (SCA7). Non syndromic CRDs are genetically heterogeneous (ten cloned genes and three loci have been identified so far). The four major causative genes involved in the pathogenesis of CRDs are ABCA4 (which causes Stargardt disease and also 30 to 60% of autosomal recessive CRDs), CRX and GUCY2D (which are responsible for many reported cases of autosomal dominant CRDs), and RPGR (which causes about 2/3 of X-linked RP and also an undetermined percentage of X-linked CRDs). It is likely that highly deleterious mutations in genes that otherwise cause RP or macular dystrophy may also lead to CRDs. The diagnosis of CRDs is based on clinical history, fundus examination and electroretinogram. Molecular diagnosis can be made for some genes, genetic counseling is always advised. Currently

  3. The uniqueness of the solution of cone-like inversion models for halo CMEs

    NASA Astrophysics Data System (ADS)

    Zhao, X. P.

    2006-12-01

    Most of elliptic halo CMEs are believed to be formed by the Thompson scattering of the photospheric light by the 3-D cone-like shell of the CME plasma. To obtain the real propagation direction and angular width of the halo CMEs, such cone-like inversion models as the circular cone, the elliptic cone and the ice-cream cone models have been suggested recently. Because the number of given parameters that are used to characterize 2-D elliptic halo CMEs observed by one spacecraft are less than the number of unknown parameters that are used to characterize the 3-D elliptic cone model, the solution of the elliptic cone model is not unique. Since it is difficult to determine whether or not an observed halo CME is formed by an circular cone or elliptic cone shell, the solution of circular cone model may often be not unique too. To fix the problem of the uniqueness of the solution of various 3-D cone-like inversion models, this work tries to develop the algorithm for using the data from multi-spacecraft, such as the STEREO A and B, and the Solar Sentinels.

  4. Purification of cone outer segment for proteomic analysis on its membrane proteins in carp retina

    PubMed Central

    Fukagawa, Takashi; Takafuji, Kazuaki; Tachibanaki, Shuji

    2017-01-01

    Rods and cones are both photoreceptors in the retina, but they are different in many aspects including the light response characteristics and, for example, cell morphology and metabolism. These differences would be caused by differences in proteins expressed in rods and cones. To understand the molecular bases of these differences between rods and cones, one of the ways is to compare proteins expressed in rods and cones, and to find those expressed specifically or dominantly. In the present study, we are interested in proteins in the outer segment (OS), the site responsible for generation of rod- or cone-characteristic light responses and also the site showing different morphology between rods and cones. For this, we established a method to purify the OS and the inner segment (IS) of rods and also of cones from purified carp rods and cones, respectively, using sucrose density gradient. In particular, we were interested in proteins tightly bound to the membranes of cone OS. To identify these proteins, we analyzed proteins in some selected regions of an SDS-gel of washed membranes of the OS and the IS obtained from both rods and cones, with Liquid Chromatography-tandem Mass Spectrometry (LC-MS/MS) using a protein database constructed from carp retina. By comparing the lists of the proteins found in the OS and the IS of both rods and cones, we found some proteins present in cone OS membranes specifically or dominantly, in addition to the proteins already known to be present specifically in cone OS. PMID:28291804

  5. Retinal bipolar cells: temporal filtering of signals from cone photoreceptors.

    PubMed

    Burkhardt, Dwight A; Fahey, Patrick K; Sikora, Michael A

    2007-01-01

    The temporal dynamics of the response of neurons in the outer retina were investigated by intracellular recording from cones, bipolar, and horizontal cells in the intact, light-adapted retina of the tiger salamander (Ambystoma tigrinum), with special emphasis on comparing the two major classes of bipolars cells, the ON depolarizing bipolars (Bd) and the OFF hyperpolarizing bipolars (Bh). Transfer functions were computed from impulse responses evoked by a brief light flash on a steady background of 20 cd/m(2). Phase delays ranged from about 89 ms for cones to 170 ms for Bd cells, yielding delays relative to that of cones of about 49 ms for Bh cells and 81 ms for Bd cells. The difference between Bd and Bh cells, which may be due to a delay introduced by the second messenger G-protein pathway unique to Bd cells, was further quantified by latency measurements and responses to white noise. The amplitude transfer functions of the outer retinal neurons varied with light adaptation in qualitative agreement with results for other vertebrates and human vision. The transfer functions at 20 cd/m(2) were predominantly low pass with 10-fold attenuation at about 13, 14, 9.1, and 7.7 Hz for cones, horizontal, Bh, and Bd cells, respectively. The transfer function from the cone voltage to the bipolar voltage response, as computed from the above measurements, was low pass and approximated by a cascade of three low pass RC filters ("leaky integrators"). These results for cone-->bipolar transmission are surprisingly similar to recent results for rod-->bipolar transmission in salamander slice preparations. These and other findings suggest that the rate of vesicle replenishment rather than the rate of release may be a common factor shaping synaptic signal transmission from rods and cones to bipolar cells.

  6. Dark-induced cone outer segment damage in the neon tetra (Paracheirodon innesi).

    PubMed

    Lythgoe, J N; Shand, J

    1984-11-01

    The outer segment of the twin cones of the neon tetra show scrolling and vesiculation when exposed to 36 hr of continuous darkness. This disruption first begins as a rolling of the margins of the cone lamellae and proceeds to form a complex pattern of scrolls and vesicles. There is evidence that this damage can be repaired without having to return the animals to a normal light regime. Similar lamellar disruptions have been seen in the outer segments of both rods and cones of other species that have been exposed to various other light regimes including constant light.

  7. The Holographic Entropy Cone

    SciTech Connect

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; Stoica, Bogdan; Sully, James; Walter, Michael

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phase space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.

  8. The Holographic Entropy Cone

    DOE PAGES

    Bao, Ning; Nezami, Sepehr; Ooguri, Hirosi; ...

    2015-09-21

    We initiate a systematic enumeration and classification of entropy inequalities satisfied by the Ryu-Takayanagi formula for conformal field theory states with smooth holographic dual geometries. For 2, 3, and 4 regions, we prove that the strong subadditivity and the monogamy of mutual information give the complete set of inequalities. This is in contrast to the situation for generic quantum systems, where a complete set of entropy inequalities is not known for 4 or more regions. We also find an infinite new family of inequalities applicable to 5 or more regions. The set of all holographic entropy inequalities bounds the phasemore » space of Ryu-Takayanagi entropies, defining the holographic entropy cone. We characterize this entropy cone by reducing geometries to minimal graph models that encode the possible cutting and gluing relations of minimal surfaces. We find that, for a fixed number of regions, there are only finitely many independent entropy inequalities. To establish new holographic entropy inequalities, we introduce a combinatorial proof technique that may also be of independent interest in Riemannian geometry and graph theory.« less

  9. Kinematics of Cone-In-Cone Growth, with Implications for Timing and Formation Mechanism

    NASA Astrophysics Data System (ADS)

    Hooker, J. N.; Cartwright, J. A.

    2015-12-01

    Cone-in-cone is an enigmatic structure. Similar to many fibrous calcite veins, cone-in-cone is generally formed of calcite and present in bedding-parallel vein-like accumulations within fine-grained rocks. Unlike most fibrous veins, cone-in-cone contains conical inclusions of host-rock material, creating nested, parallel cones throughout. A long-debated aspect of cone-in-cone structures is whether the calcite precipitated with its conical form (primary cone-in-cone), or whether the cones formed afterwards (secondary cone-in-cone). Trace dolomite within a calcite cone-in-cone structure from the Cretaceous of Jordan supports the primary hypothesis. The host sediment is a siliceous mud containing abundant rhombohedral dolomite grains. Dolomite rhombohedra are also distributed throughout the cone-in-cone. The rhombohedra within the cones are randomly oriented yet locally have dolomite overgrowths having boundaries that are aligned with calcite fibers. Evidence that dolomite co-precipitated with calcite, and did not replace calcite, includes (i) preferential downward extension of dolomite overgrowths, in the presumed growth-direction of the cone-in-cone, and (ii) planar, vertical borders between dolomite crystals and calcite fibers. Because dolomite overgrows host-sediment rhombohedra and forms fibers within the cones, it follows that the host-sediment was included within the growing cone-in-cone as the calcite precipitated, and not afterward. The host-sediment was not injected into the cone-in-cone along fractures, as the secondary-origin hypothesis suggests. This finding implies that cone-in-cone in general does not form over multiple stages, and thus has greater potential to preserve the chemical signature of its original precipitation. Because cone-in-cone likely forms before complete lithification of the host, and because the calcite displaces the host material against gravity, this chemical signature can preserve information about early overpressures in fine

  10. Making An Impact: Shatter Cones

    ERIC Educational Resources Information Center

    Blank, Lisa M.; Plautz, Michael R.; Crews, Jeffrey W.

    2004-01-01

    In 1990, a group of geologists discovered a large number of shatter cones in southwestern Montana. Shatter cones are a type of metamorphosed rock often found in impact structures (the remains of a crater after a meteor impact and years of Earth activity). Scientists have discovered only 168 impact craters around the world. If rocks could talk,…

  11. Making An Impact: Shatter Cones

    ERIC Educational Resources Information Center

    Blank, Lisa M.; Plautz, Michael R.; Crews, Jeffrey W.

    2004-01-01

    In 1990, a group of geologists discovered a large number of shatter cones in southwestern Montana. Shatter cones are a type of metamorphosed rock often found in impact structures (the remains of a crater after a meteor impact and years of Earth activity). Scientists have discovered only 168 impact craters around the world. If rocks could talk,…

  12. Color vision, cones, and color-coding in the cortex.

    PubMed

    Conway, Bevil R

    2009-06-01

    Color processing begins with the absorption of light by cone photoreceptors, and progresses through a series of hierarchical stages: Retinal signals carrying color information are transmitted through the lateral geniculate nucleus of the thalamus (LGN) up to the primary visual cortex (V1). From V1, the signals are processed by the second visual area (V2); then by cells located in subcompartments ("globs") within the posterior inferior temporal (PIT) cortex, a brain region that encompasses area V4 and brain regions immediately anterior to V4. Color signals are then processed by regions deep within the inferior temporal (IT) cortex including area TE. As a heuristic, one can consider each of these stages to be involved in constructing a distinct aspect of the color percept. The three cone types are the basis for trichromacy; retinal ganglion cells that respond in an opponent fashion to activation of different cone classes are the basis for color opponency (these "cone-opponent" cells increase their firing rate above baseline to activation of one cone class and decrease their firing rate below baseline to activation of a different cone class); double-opponent neurons in the V1 generate local color contrast and are the building blocks for color constancy; glob cells elaborate the perception of hue; and IT integrates color perception in the context of behavior. Finally, though nothing is known, these signals presumably interface with motor programs and emotional centers of the brain to mediate the widely acknowledged emotional salience of color.

  13. Imaging modal content of cone photoreceptors using adaptive optics optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Liu, Zhuolin; Kocaoglu, Omer P.; Turner, Timothy L.; Miller, Donald T.

    2015-03-01

    It has been long established that photoreceptors capture light based on the principles of optical waveguiding. Yet after decades of experimental and theoretical investigations considerable uncertainty remains, even for the most basic prediction as to whether photoreceptors support more than a single waveguide mode. To test for modal behavior in human cone photoreceptors, we took advantage of adaptive-optics optical coherence tomography (AO-OCT, λc=785 nm) to noninvasively image in three dimensions the reflectance profiles generated in the inner and outer segments (IS, OS) of cones. Mode content was examined over a range of cone diameters by imaging cones from 0.6° to 10° retinal eccentricity (n = 1802). Fundamental to the method was extraction of reflections at the cone IS/OS junction and cone outer segment tip (COST). Modal content properties of size, circularity and orientation were quantified using second moment analysis. Analysis of the cone reflections indicates waveguide properties of cone IS and OS depend on segment diameter. Cone IS was found to support a single mode near the fovea (<=3°) and multiple modes further away (<4°). In contrast, no evidence of multiple modes was found in the cone OSs. The IS/OS and COST reflections share a common optical aperture, are most circular near the fovea, and show no orientation preference.

  14. Laser range profile of cones

    NASA Astrophysics Data System (ADS)

    Zhou, Wenzhen; Gong, Yanjun; Wang, Mingjun; Gong, Lei

    2016-10-01

    technology. Laser one-dimensional range profile can reflect the characteristics of the target shape and surface material. These techniques were motivated by applications of laser radar to target discrimination in ballistic missile defense. The radar equation of pulse laser about cone is given in this paper. This paper demonstrates the analytical model of laser one-dimensional range profile of cone based on the radar equation of the pulse laser. Simulations results of laser one-dimensional range profiles of some cones are given. Laser one-dimensional range profiles of cone, whose surface material with diffuse lambertian reflectance, is given in this paper. Laser one-dimensional range profiles of cone, whose surface mater with diffuse materials whose retroreflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. Laser one-dimensional range profiles of different pulse width of cone is given in this paper. The influences of surface material, pulse width, attitude on the one-dimensional range are analyzed. The laser two-dimensional range profile is two-dimensional scattering imaging of pulse laser of target. The two-dimensional range profile of roughness target can provide range resolved information. An analytical model of two-dimensional laser range profile of cone is proposed. The simulations of two-dimensional laser range profiles of some cones are given. Laser two-dimensional range profiles of cone, whose surface mater with diffuse lambertian reflectance, is given in this paper. Laser two-dimensional range profiles of cone, whose surface mater with diffuse materials whose retroreflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. The influence of pulse width, surface material on laser two-dimensional range profile is analyzed. Laser one-dimensional range profile and laser two-dimensional range profile are called as laser

  15. Reliability and Repeatability of Cone Density Measurements in Patients with Congenital Achromatopsia.

    PubMed

    Abozaid, Mortada A; Langlo, Christopher S; Dubis, Adam M; Michaelides, Michel; Tarima, Sergey; Carroll, Joseph

    2016-01-01

    Adaptive optics scanning light ophthalmoscopy (AOSLO) allows non-invasive assessment of the cone photoreceptor mosaic. Confocal AOSLO imaging of patients with achromatopsia (ACHM) reveals an altered reflectivity of the remaining cone structure, making identification of the cells more challenging than in normal retinas. Recently, a "split-detector" AOSLO imaging method was shown to enable direct visualization of cone inner segments in patients with ACHM. Several studies have demonstrated gene replacement therapy effective in restoring cone function in animal models of ACHM and human trials have on the horizon, making the ability to reliably assess cone structure increasingly important. Here we sought to examine whether absolute estimates of cone density obtained from split-detector and confocal AOSLO images differed from one another and whether the inter- and intra-observer reliability is significantly different between these modes. These findings provide an important foundation for evaluating the role of these images as tools to assess the efficacy of future gene therapy trials.

  16. Deletion of the p85alpha regulatory subunit of phosphoinositide 3-kinase in cone photoreceptor cells results in cone photoreceptor degeneration.

    PubMed

    Ivanovic, Ivana; Anderson, Robert E; Le, Yun Z; Fliesler, Steven J; Sherry, David M; Rajala, Raju V S

    2011-06-01

    Downregulation of the retinal insulin/mTOR pathway in mouse models of retinitis pigmentosa is linked to cone cell death, which can be delayed by systemic administration of insulin. A classic survival kinase linking extracellular trophic/growth factors with intracellular antiapoptotic pathways is phosphoinositide 3-kinase (PI3K), which the authors have shown to protect rod photoreceptors from stress-induced cell death. The role of PI3K in cones was studied by conditional deletion of its p85α regulatory subunit. Mice expressing Cre recombinase in cones were bred to mice with a floxed pi3k gene encoding the p85α regulatory subunit of the PI3K and were back-crossed to ultimately generate offspring with cone-specific p85α knockout (cKO). Cre expression and cone-specific localization were confirmed by Western blot analysis and immunohistochemistry (IHC), respectively. Cone structural integrity was determined by IHC using peanut agglutinin and an M-opsin-specific antibody. Electroretinography (ERG) was used to assess rod and cone photoreceptor function. Retinal structure was examined by light and electron microscopy. An age-related cone degeneration was found in cKO mice, evidenced by a reduction in photopic ERG amplitudes and loss of cone cells. By 12 months of age, approximately 78% of cones had died, and progressive disorganization of synaptic ultrastructure was noted in surviving cone terminals in cKO retinas. Rod viability was unaffected in p85α cKO mice. The present study suggests that PI3K signaling pathway is essential for cone survival in the mouse retina.

  17. Deletion of the p85α Regulatory Subunit of Phosphoinositide 3-Kinase in Cone Photoreceptor Cells Results in Cone Photoreceptor Degeneration

    PubMed Central

    Ivanovic, Ivana; Anderson, Robert E.; Le, Yun Z.; Fliesler, Steven J.; Sherry, David M.

    2011-01-01

    Purpose. Downregulation of the retinal insulin/mTOR pathway in mouse models of retinitis pigmentosa is linked to cone cell death, which can be delayed by systemic administration of insulin. A classic survival kinase linking extracellular trophic/growth factors with intracellular antiapoptotic pathways is phosphoinositide 3-kinase (PI3K), which the authors have shown to protect rod photoreceptors from stress-induced cell death. The role of PI3K in cones was studied by conditional deletion of its p85α regulatory subunit. Methods. Mice expressing Cre recombinase in cones were bred to mice with a floxed pi3k gene encoding the p85α regulatory subunit of the PI3K and were back-crossed to ultimately generate offspring with cone-specific p85α knockout (cKO). Cre expression and cone-specific localization were confirmed by Western blot analysis and immunohistochemistry (IHC), respectively. Cone structural integrity was determined by IHC using peanut agglutinin and an M-opsin–specific antibody. Electroretinography (ERG) was used to assess rod and cone photoreceptor function. Retinal structure was examined by light and electron microscopy. Results. An age-related cone degeneration was found in cKO mice, evidenced by a reduction in photopic ERG amplitudes and loss of cone cells. By 12 months of age, approximately 78% of cones had died, and progressive disorganization of synaptic ultrastructure was noted in surviving cone terminals in cKO retinas. Rod viability was unaffected in p85α cKO mice. Conclusions. The present study suggests that PI3K signaling pathway is essential for cone survival in the mouse retina. PMID:21398281

  18. Vesicle Pool Size at the Salamander Cone Ribbon Synapse

    PubMed Central

    Bartoletti, Theodore M.; Babai, Norbert

    2010-01-01

    Cone light responses are transmitted to postsynaptic neurons by changes in the rate of synaptic vesicle release. Vesicle pool size at the cone synapse constrains the amount of release and can thus shape contrast detection. We measured the number of vesicles in the rapidly releasable and reserve pools at cone ribbon synapses by performing simultaneous whole cell recording from cones and horizontal or off bipolar cells in the salamander retinal slice preparation. We found that properties of spontaneously occurring miniature excitatory postsynaptic currents (mEPSCs) are representative of mEPSCs evoked by depolarizing presynaptic stimulation. Strong, brief depolarization of the cone stimulated release of the entire rapidly releasable pool (RRP) of vesicles. Comparing charge transfer of the EPSC with mEPSC charge transfer, we determined that the fast component of the EPSC reflects release of ∼40 vesicles. Comparing EPSCs with simultaneous presynaptic capacitance measurements, we found that horizontal cell EPSCs constitute 14% of the total number of vesicles released from a cone terminal. Using a fluorescent ribeye-binding peptide, we counted ∼13 ribbons per cone. Together, these results suggest each cone contacts a single horizontal cell at ∼2 ribbons. The size of discrete components in the EPSC amplitude histogram also suggested ∼2 ribbon contacts per cell pair. We therefore conclude there are ∼20 vesicles per ribbon in the RRP, similar to the number of vesicles contacting the plasma membrane at the ribbon base. EPSCs evoked by lengthy depolarization suggest a reserve pool of ∼90 vesicles per ribbon, similar to the number of additional docking sites further up the ribbon. PMID:19923246

  19. Accommodation with and without short-wavelength-sensitive cones and chromatic aberration.

    PubMed

    Kruger, Philip B; Rucker, Frances J; Hu, Caitlin; Rutman, Hadassa; Schmidt, Nathan W; Roditis, Vasilios

    2005-05-01

    Accommodation was monitored while observers (23) viewed a square-wave grating (2.2 cycles/deg; 0.53 contrast) in a Badal optometer. The grating moved sinusoidally (0.2 Hz) to provide a stimulus between -1.00 D and -3.00 D during trials lasting 40.96 s. There were three illumination conditions: 1. Monochromatic 550 nm light to stimulate long-wavelength-sensitive cones (L-cones) and medium-wavelength-sensitive cones (M-cones) without chromatic aberration; 2. Monochromatic 550 nm light+420 nm light to stimulate long-, medium- and short-wavelength-sensitive cones (S-cones) with longitudinal chromatic aberration (LCA); 3. Monochromatic 550 nm light+420 nm light to stimulate L-, M- and S-cones viewed through an achromatizing lens. In the presence of LCA mean dynamic gain decreased (p=0.0003; ANOVA) and mean accommodation level was reduced (p=0.001; ANOVA). The reduction in gain and increased lag of accommodation in the presence of LCA could result from a blue-yellow chromatic signal or from a larger depth-of-focus.

  20. SWS (blue) cone hypersensitivity in a newly identified retinal degeneration.

    PubMed

    Jacobson, S G; Marmor, M F; Kemp, C M; Knighton, R W

    1990-05-01

    Photoreceptor-mediated mechanisms were studied in patients with a recently identified retinopathy typified by night blindness, cystoid maculopathy, and similar scotopic and photopic electroretinograms (ERGs). Dark-adapted spectral sensitivity functions were only partly explained as composites of rod and cone curves shifted to lower sensitivities; there was unusually high sensitivity from 400-460 nm. A rod mechanism, reduced in sensitivity by at least 3 log units, was detectable with dark adaptometry. No measurable rhodopsin was found with fundus reflectometry. Light-adapted spectral sensitivities were subnormal for wavelengths greater than 500 nm but supernormal from 420-460 nm. On a yellow adapting field, the supernormal spectrum approximated that of the short-wavelength-sensitive (SWS) cone system. With spectral ERGs, two mechanisms were demonstrated. Dark- and light-adapted ERGs to green, orange-yellow, and red stimuli had similar waveforms and coincident intensity-response functions on a photopic intensity axis. ERGs to blue and blue-green stimuli were similar, and intensity-response functions coincided on a SWS cone intensity axis. Patients varied in the degree to which rod and midspectral cone function were decreased and SWS cone function was increased.

  1. Response properties of cones from the retina of the tiger salamander.

    PubMed Central

    Perry, R J; McNaughton, P A

    1991-01-01

    1. Spectral sensitivity measurements using the suction electrode technique reveal three types of cone in the retina of the tiger salamander, showing maximum sensitivity at wavelengths 610 nm (red-sensitive cone), 444 nm (blue-sensitive cone) and below 400 nm (UV-sensitive cone). 2. The absolute sensitivities of red- and blue-sensitive cones to flashes of optimal wavelength are 0.022 and 0.33 pA photon-1 micron 2 respectively. 3. The time-to-peak of the dim flash response and the recovery of membrane current after a flash of any intensity are fastest in red-sensitive and slowest in blue-sensitive cones. 4. In blue- and UV-sensitive cones the flash response peaks progressively earlier as the flash strength is increased, as in rods. In red-sensitive cones, however, bright flash responses take longer to peak than dim flash responses. 5. In all three cone types, voltage clamping at -40 mV reduces the time-to-peak of the response to a bright flash, showing that the rising phase of the bright flash response is normally limited by the time constant of the cell. Under voltage clamp, all cones show a decrease in time-to-peak with increasing flash intensity. 6. Voltage clamping red-sensitive cones reveals two components of the rising phase of the response to a bright flash. Most of the current is rapidly suppressed by a bright flash, and represents the closure of light-sensitive channels. The residual current decays with a mean time constant of 20 ms, and is probably attributable to the decline of electrogenic Na(+)-Ca2+, K+ exchange. The amplitude of this exchange current suggests that the proportion of the dark current carried by calcium ions is greater in red-sensitive cones than in rods of the same species. 7. In UV-sensitive cones, a prominent oscillation of light-sensitive current is observed during the recovery from flashes of intermediate intensity. A similar, but slower and less prominent oscillation is usually seen in blue-sensitive cones. 8. When a red

  2. Response properties of cones from the retina of the tiger salamander.

    PubMed

    Perry, R J; McNaughton, P A

    1991-02-01

    1. Spectral sensitivity measurements using the suction electrode technique reveal three types of cone in the retina of the tiger salamander, showing maximum sensitivity at wavelengths 610 nm (red-sensitive cone), 444 nm (blue-sensitive cone) and below 400 nm (UV-sensitive cone). 2. The absolute sensitivities of red- and blue-sensitive cones to flashes of optimal wavelength are 0.022 and 0.33 pA photon-1 micron 2 respectively. 3. The time-to-peak of the dim flash response and the recovery of membrane current after a flash of any intensity are fastest in red-sensitive and slowest in blue-sensitive cones. 4. In blue- and UV-sensitive cones the flash response peaks progressively earlier as the flash strength is increased, as in rods. In red-sensitive cones, however, bright flash responses take longer to peak than dim flash responses. 5. In all three cone types, voltage clamping at -40 mV reduces the time-to-peak of the response to a bright flash, showing that the rising phase of the bright flash response is normally limited by the time constant of the cell. Under voltage clamp, all cones show a decrease in time-to-peak with increasing flash intensity. 6. Voltage clamping red-sensitive cones reveals two components of the rising phase of the response to a bright flash. Most of the current is rapidly suppressed by a bright flash, and represents the closure of light-sensitive channels. The residual current decays with a mean time constant of 20 ms, and is probably attributable to the decline of electrogenic Na(+)-Ca2+, K+ exchange. The amplitude of this exchange current suggests that the proportion of the dark current carried by calcium ions is greater in red-sensitive cones than in rods of the same species. 7. In UV-sensitive cones, a prominent oscillation of light-sensitive current is observed during the recovery from flashes of intermediate intensity. A similar, but slower and less prominent oscillation is usually seen in blue-sensitive cones. 8. When a red

  3. Rapid Recovery of Visual Function Associated with Blue Cone Ablation in Zebrafish

    PubMed Central

    Hagerman, Gordon F.; Noel, Nicole C. L.; Cao, Sylvia Y.; DuVal, Michèle G.; Oel, A. Phillip; Allison, W. Ted

    2016-01-01

    Hurdles in the treatment of retinal degeneration include managing the functional rewiring of surviving photoreceptors and integration of any newly added cells into the remaining second-order retinal neurons. Zebrafish are the premier genetic model for such questions, and we present two new transgenic lines allowing us to contrast vision loss and recovery following conditional ablation of specific cone types: UV or blue cones. The ablation of each cone type proved to be thorough (killing 80% of cells in each intended cone class), specific, and cell-autonomous. We assessed the loss and recovery of vision in larvae via the optomotor behavioural response (OMR). This visually mediated behaviour decreased to about 5% or 20% of control levels following ablation of UV or blue cones, respectively (P<0.05). We further assessed ocular photoreception by measuring the effects of UV light on body pigmentation, and observed that photoreceptor deficits and recovery occurred (p<0.01) with a timeline coincident to the OMR results. This corroborated and extended previous conclusions that UV cones are required photoreceptors for modulating body pigmentation, addressing assumptions that were unavoidable in previous experiments. Functional vision recovery following UV cone ablation was robust, as measured by both assays, returning to control levels within four days. In contrast, robust functional recovery following blue cone ablation was unexpectedly rapid, returning to normal levels within 24 hours after ablation. Ablation of cones led to increased proliferation in the retina, though the rapid recovery of vision following blue cone ablation was demonstrated to not be mediated by blue cone regeneration. Thus rapid visual recovery occurs following ablation of some, but not all, cone subtypes, suggesting an opportunity to contrast and dissect the sources and mechanisms of outer retinal recovery during cone photoreceptor death and regeneration. PMID:27893779

  4. Rapid Recovery of Visual Function Associated with Blue Cone Ablation in Zebrafish.

    PubMed

    Hagerman, Gordon F; Noel, Nicole C L; Cao, Sylvia Y; DuVal, Michèle G; Oel, A Phillip; Allison, W Ted

    2016-01-01

    Hurdles in the treatment of retinal degeneration include managing the functional rewiring of surviving photoreceptors and integration of any newly added cells into the remaining second-order retinal neurons. Zebrafish are the premier genetic model for such questions, and we present two new transgenic lines allowing us to contrast vision loss and recovery following conditional ablation of specific cone types: UV or blue cones. The ablation of each cone type proved to be thorough (killing 80% of cells in each intended cone class), specific, and cell-autonomous. We assessed the loss and recovery of vision in larvae via the optomotor behavioural response (OMR). This visually mediated behaviour decreased to about 5% or 20% of control levels following ablation of UV or blue cones, respectively (P<0.05). We further assessed ocular photoreception by measuring the effects of UV light on body pigmentation, and observed that photoreceptor deficits and recovery occurred (p<0.01) with a timeline coincident to the OMR results. This corroborated and extended previous conclusions that UV cones are required photoreceptors for modulating body pigmentation, addressing assumptions that were unavoidable in previous experiments. Functional vision recovery following UV cone ablation was robust, as measured by both assays, returning to control levels within four days. In contrast, robust functional recovery following blue cone ablation was unexpectedly rapid, returning to normal levels within 24 hours after ablation. Ablation of cones led to increased proliferation in the retina, though the rapid recovery of vision following blue cone ablation was demonstrated to not be mediated by blue cone regeneration. Thus rapid visual recovery occurs following ablation of some, but not all, cone subtypes, suggesting an opportunity to contrast and dissect the sources and mechanisms of outer retinal recovery during cone photoreceptor death and regeneration.

  5. Lighting

    SciTech Connect

    Audin, L.

    1994-12-31

    EPAct covers a vast territory beyond lighting and, like all legislation, also contains numerous {open_quotes}favors,{close_quotes} compromises, and even some sleight-of-hand. Tucked away under Title XIX, for example, is an increase from 20% to 28% tax on gambling winnings, effective January 1, 1993 - apparently as a way to help pay for new spending listed elsewhere in the bill. Overall, it is a landmark piece of legislation, about a decade overdue. It remains to be seen how the Federal Government will enforce upgrading of state (or even their own) energy codes. There is no mention of funding for {open_quotes}energy police{close_quotes} in EPAct. Merely creating such a national standard, however, provides a target for those who sincerely wish to create an energy-efficient future.

  6. A neuronal circuit for colour vision based on rod-cone opponency.

    PubMed

    Joesch, Maximilian; Meister, Markus

    2016-04-14

    In bright light, cone-photoreceptors are active and colour vision derives from a comparison of signals in cones with different visual pigments. This comparison begins in the retina, where certain retinal ganglion cells have 'colour-opponent' visual responses-excited by light of one colour and suppressed by another colour. In dim light, rod-photoreceptors are active, but colour vision is impossible because they all use the same visual pigment. Instead, the rod signals are thought to splice into retinal circuits at various points, in synergy with the cone signals. Here we report a new circuit for colour vision that challenges these expectations. A genetically identified type of mouse retinal ganglion cell called JAMB (J-RGC), was found to have colour-opponent responses, OFF to ultraviolet (UV) light and ON to green light. Although the mouse retina contains a green-sensitive cone, the ON response instead originates in rods. Rods and cones both contribute to the response over several decades of light intensity. Remarkably, the rod signal in this circuit is antagonistic to that from cones. For rodents, this UV-green channel may play a role in social communication, as suggested by spectral measurements from the environment. In the human retina, all of the components for this circuit exist as well, and its function can explain certain experiences of colour in dim lights, such as a 'blue shift' in twilight. The discovery of this genetically defined pathway will enable new targeted studies of colour processing in the brain.

  7. Circadian regulation of teleost retinal cone movements in vitro

    PubMed Central

    1994-01-01

    In the retinas of many species of lower vertebrates, retinal photoreceptors and pigment epithelium pigment granules undergo daily movements in response to both diurnal, and in the case of teleost cone photoreceptors, endogenous circadian signals. Typically, these cone movements take place at dawn and at dusk when teleosts are maintained on a cyclic light (LD) regime, and at expected dawn and expected dusk when animals are maintained in continuous darkness (DD). Because these movements are so strictly controlled, they provide an overt indicator of the stage of the underlying clock mechanism. In this study we report that both light-induced and circadian-driven cone myoid movements in the Midas cichlid (Cichlasoma citrinellum), occur normally in vitro. Many of the features of retinomotor movements found in vivo also occur in our culture conditions, including responses to light and circadian stimuli and dopamine. Circadian induced predawn contraction and maintenance of expected day position in response to circadian modulation, are also normal. Our studies suggest that circadian regulation of cone myoid movement in vitro is mediated locally by dopamine, acting via a D2 receptor. Cone myoid contraction can be induced at midnight and expected mid-day by dark culture with dopamine or the D2 receptor agonist LY171555. Further, circadian induced predawn contraction can be increased with either dopamine or LY171555, or may be reversed with the dopamine D2 antagonist, sulpiride. Sulpiride will also induce cone myoid elongation in retinal cultures at expected mid- day, but will not induce cone myoid elongation at dusk. In contrast, circadian cone myoid movements in vitro were unaffected by the D1 receptor agonist SCH23390, or the D1 receptor antagonist SKF38393. Our short-term culture experiments indicate that circadian regulation of immediate cone myoid movement does not require humoral control but is regulated locally within the retina. The inclusion of dopamine, or dopamine

  8. Rod and cone signals in the horizontal cells of the tiger salamander retina.

    PubMed Central

    Hanani, M; Vallerga, S

    1980-01-01

    1. Intracellular recordings of horizontal cell responses to monochromatic lights of various wave-lengths and intensities were made in the retina of the larval tiger salamander in order to determine the contributions of rod and cone activities to horizontal cell responses. 2. Under conditions of extensive dark adaptation, and with dim light stimulation, the horizontal cell responses reflected mainly rod activity. In the light-adapted state or at high light intensities the cone contribution was dominant. 3. Bright adapting flashes selectively suppressed the rod component of horizontal cell responses. 4. Intracellular recordings from rods and cones showed that interactions between the two receptor types are very small and cannot account for the large rod--cone mixed input observed in horizontal cells. It is concluded that this input is mediated by direct connexions between receptors and horizontal cells. PMID:7359420

  9. Feedback-induced glutamate spillover enhances negative feedback from horizontal cells to cones

    PubMed Central

    Vroman, Rozan; Kamermans, Maarten

    2015-01-01

    Key points In the retina, horizontal cells feed back negatively to cone photoreceptors. Glutamate released from cones can spill over to neighbouring cones. Here we show that cone glutamate release induced by negative feedback can also spill over to neighbouring cones. This glutamate activates the glutamate transporter-associated chloride current in these neighbouring cones, which leads to a change in their membrane potential and thus modulates their output. In this way, feedback-induced glutamate spillover enhances negative feedback from horizontal cells to cones, thus forming an additional feedback pathway. This effect will be particularly prominent in cones that are strongly hyperpolarized by light. Abstract Inhibition in the outer retina functions via an unusual mechanism. When horizontal cells hyperpolarize the activation potential of the Ca2+ current of cones shifts to more negative potentials. The underlying mechanism consists of an ephaptic component and a Panx1/ATP-mediated component. Here we identified a third feedback component, which remains active outside the operating range of the Ca2+ current. We show that the glutamate transporters of cones can be activated by glutamate released from their neighbours. This pathway can be triggered by negative feedback from horizontal cells to cones, thus providing an additional feedback pathway. This additional pathway is mediated by a Cl− current, can be blocked by either removing the gradient of K+ or by adding the glutamate transporter blocker TBOA, or low concentrations of Zn2+. These features point to a glutamate transporter-associated Cl− current. The pathway has a delay of 4.7 ± 1.7 ms. The effectiveness of this pathway in modulating the cone output depends on the equilibrium potential of Cl− (ECl) and the membrane potential of the cone. Because estimates of ECl show that it is around the dark resting membrane potential of cones, the activation of the glutamate transporter-associated Cl− current

  10. Ejecta evolution during cone impact

    NASA Astrophysics Data System (ADS)

    Marston, Jeremy; Vakarelski, Ivan; Thoroddsen, Sigurdur

    2013-11-01

    We present results from an experimental study of the impact of conical shaped bodies into a pool of liquid. By varying the cone angle, impact speed and liquid physical properties, we examine a broad parameter space and seek to find conditions when self-similarity can be observed during this phenomena. We use high-speed imaging to capture the early-time motion of the liquid ejecta which emanates from the tip of the cone and travels up along the cone surface. Surprisingly, we find that the detachment of the ejecta can be simply described by air entrainment relationships derived from coating experiments.

  11. Transonic Flow Past Cone Cylinders

    NASA Technical Reports Server (NTRS)

    Solomon, George E

    1955-01-01

    Experimental results are presented for transonic flow post cone-cylinder, axially symmetric bodies. The drag coefficient and surface Mach number are studied as the free-stream Mach number is varied and, wherever possible, the experimental results are compared with theoretical predictions. Interferometric results for several typical flow configurations are shown and an example of shock-free supersonic-to-subsonic compression is experimentally demonstrated. The theoretical problem of transonic flow past finite cones is discussed briefly and an approximate solution of the axially symmetric transonic equations, valid for a semi-infinite cone, is presented.

  12. Cone and Seed Maturation of Southern Pines

    Treesearch

    James P. Barnett

    1976-01-01

    If slightly reduced yields and viability are acceptable, loblolly and slash cone collections can begin 2 to 3 weeks before maturity if the cones are stored before processing. Longleaf(P. palestris Mill.) pine cones should be collected only when mature, as storage decreased germination of seeds from immature cones. Biochemical analyses to determine reducing sugar...

  13. Functional significance of the taper of vertebrate cone photoreceptors

    PubMed Central

    Hárosi, Ferenc I.

    2012-01-01

    Vertebrate photoreceptors are commonly distinguished based on the shape of their outer segments: those of cones taper, whereas the ones from rods do not. The functional advantages of cone taper, a common occurrence in vertebrate retinas, remain elusive. In this study, we investigate this topic using theoretical analyses aimed at revealing structure–function relationships in photoreceptors. Geometrical optics combined with spectrophotometric and morphological data are used to support the analyses and to test predictions. Three functions are considered for correlations between taper and functionality. The first function proposes that outer segment taper serves to compensate for self-screening of the visual pigment contained within. The second function links outer segment taper to compensation for a signal-to-noise ratio decline along the longitudinal dimension. Both functions are supported by the data: real cones taper more than required for these compensatory roles. The third function relates outer segment taper to the optical properties of the inner compartment whereby the primary determinant is the inner segment’s ability to concentrate light via its ellipsoid. In support of this idea, the rod/cone ratios of primarily diurnal animals are predicted based on a principle of equal light flux gathering between photoreceptors. In addition, ellipsoid concentration factor, a measure of ellipsoid ability to concentrate light onto the outer segment, correlates positively with outer segment taper expressed as a ratio of characteristic lengths, where critical taper is the yardstick. Depending on a light-funneling property and the presence of focusing organelles such as oil droplets, cone outer segments can be reduced in size to various degrees. We conclude that outer segment taper is but one component of a miniaturization process that reduces metabolic costs while improving signal detection. Compromise solutions in the various retinas and retinal regions occur between

  14. Embryonic markers of cone differentiation

    PubMed Central

    Rodgers, Helen M.; Belcastro, Marycharmain; Sokolov, Maxim

    2016-01-01

    Purpose Photoreceptor cells are born in two distinct phases of vertebrate retinogenesis. In the mouse retina, cones are born primarily during embryogenesis, while rod formation occurs later in embryogenesis and early postnatal ages. Despite this dichotomy in photoreceptor birthdates, the visual pigments and phototransduction machinery are not reactive to visual stimulus in either type of photoreceptor cell until the second postnatal week. Several markers of early cone formation have been identified, including Otx2, Crx, Blimp1, NeuroD, Trβ2, Rorβ, and Rxrγ, and all are thought to be involved in cellular determination. However, little is known about the expression of proteins involved in cone visual transduction during early retinogenesis. Therefore, we sought to characterize visual transduction proteins that are expressed specifically in photoreceptors during mouse embryogenesis. Methods Eye tissue was collected from control and phosducin-null mice at embryonic and early postnatal ages. Immunohistochemistry and quantitative reverse transcriptase-PCR (qPCR) were used to measure the spatial and temporal expression patterns of phosducin (Pdc) and cone transducin γ (Gngt2) proteins and transcripts in the embryonic and early postnatal mouse retina. Results We identified the embryonic expression of phosducin (Pdc) and cone transducin γ (Gngt2) that coincides temporally and spatially with the earliest stages of cone histogenesis. Using immunohistochemistry, the phosducin protein was first detected in the retina at embryonic day (E)12.5, and cone transducin γ was observed at E13.5. The phosducin and cone transducin γ proteins were seen only in the outer neuroblastic layer, consistent with their expression in photoreceptors. At the embryonic ages, phosducin was coexpressed with Rxrγ, a known cone marker, and with Otx2, a marker of photoreceptors. Pdc and Gngt2 mRNAs were detected as early as E10.5 with qPCR, although at low levels. Conclusions Visual transduction

  15. Visual Pigments of Goldfish Cones

    PubMed Central

    Hárosi, Ferenc I.; MacNichol, Edward F.

    1974-01-01

    Freshly isolated retinal photoreceptors of goldfish were studied microspectrophotometrically. Absolute absorptance spectra obtained from dark-adapted cone outer segments reaffirm the existence of three spectrally distinct cone types with absorption maxima at 455 ± 3,530 ± 3, and 625 ± 5 nm. These types were found often recognizable by gross cellular morphology. Side-illuminated cone outer segments were dichroic. The measured dichroic ratio for the main absorption band of each type was 2–3:1. Rapidly bleached cells revealed spectral and dichroic transitions in regions near 400–410, 435–455, and 350–360 nm. These photoproducts decay about fivefold as fast as the intermediates in frog rods. The spectral maxima of photoproducts, combined with other evidence, indicate that retinene2 is the chromophore of all three cone pigments. The average specific optical density for goldfish cone outer segments was found to be 0.0124 ± 0.0015/µm. The spectra of the blue-, and green-absorbing cones appeared to match porphyropsin standards with half-band width Δν = 4,832 ± 100 cm–1. The red-absorbing spectrum was found narrower, having Δν = 3,625 ± 100 cm–1. The results are consistent with the notion that visual pigment concentration within the outer segments is about the same for frog rods and goldfish cones, but that the blue-, and green-absorbing pigments possess molar extinctions of 30,000 liter/mol cm. The red-absorbing pigment was found to have extinction of 40,000 liter/mol cm, assuming invariance of oscillator strength among the three cone spectra. PMID:4817352

  16. Differential encoding of spatial information among retinal on cone bipolar cells

    PubMed Central

    Purgert, Robert J.

    2015-01-01

    The retina is the first stage of visual processing. It encodes elemental features of visual scenes. Distinct cone bipolar cells provide the substrate for this to occur. They encode visual information, such as color and luminance, a principle known as parallel processing. Few studies have directly examined whether different forms of spatial information are processed in parallel among cone bipolar cells. To address this issue, we examined the spatial information encoded by mouse ON cone bipolar cells, the subpopulation excited by increments in illumination. Two types of spatial processing were identified. We found that ON cone bipolar cells with axons ramifying in the central inner plexiform layer were tuned to preferentially encode small stimuli. By contrast, ON cone bipolar cells with axons ramifying in the proximal inner plexiform layer, nearest the ganglion cell layer, were tuned to encode both small and large stimuli. This dichotomy in spatial tuning is attributable to amacrine cells providing stronger inhibition to central ON cone bipolar cells compared with proximal ON cone bipolar cells. Furthermore, background illumination altered this difference in spatial tuning. It became less pronounced in bright light, as amacrine cell-driven inhibition became pervasive among all ON cone bipolar cells. These results suggest that differential amacrine cell input determined the distinct spatial encoding properties among ON cone bipolar cells. These findings enhance the known parallel processing capacity of the retina. PMID:26203104

  17. Differential encoding of spatial information among retinal on cone bipolar cells.

    PubMed

    Purgert, Robert J; Lukasiewicz, Peter D

    2015-09-01

    The retina is the first stage of visual processing. It encodes elemental features of visual scenes. Distinct cone bipolar cells provide the substrate for this to occur. They encode visual information, such as color and luminance, a principle known as parallel processing. Few studies have directly examined whether different forms of spatial information are processed in parallel among cone bipolar cells. To address this issue, we examined the spatial information encoded by mouse ON cone bipolar cells, the subpopulation excited by increments in illumination. Two types of spatial processing were identified. We found that ON cone bipolar cells with axons ramifying in the central inner plexiform layer were tuned to preferentially encode small stimuli. By contrast, ON cone bipolar cells with axons ramifying in the proximal inner plexiform layer, nearest the ganglion cell layer, were tuned to encode both small and large stimuli. This dichotomy in spatial tuning is attributable to amacrine cells providing stronger inhibition to central ON cone bipolar cells compared with proximal ON cone bipolar cells. Furthermore, background illumination altered this difference in spatial tuning. It became less pronounced in bright light, as amacrine cell-driven inhibition became pervasive among all ON cone bipolar cells. These results suggest that differential amacrine cell input determined the distinct spatial encoding properties among ON cone bipolar cells. These findings enhance the known parallel processing capacity of the retina. Copyright © 2015 the American Physiological Society.

  18. The retina visual cycle is driven by cis retinol oxidation in the outer segments of cones.

    PubMed

    Sato, Shinya; Frederiksen, Rikard; Cornwall, M Carter; Kefalov, Vladimir J

    2017-01-01

    Vertebrate rod and cone photoreceptors require continuous supply of chromophore for regenerating their visual pigments after photoactivation. Cones, which mediate our daytime vision, demand a particularly rapid supply of 11-cis retinal chromophore in order to maintain their function in bright light. An important contribution to this process is thought to be the chromophore precursor 11-cis retinol, which is supplied to cones from Müller cells in the retina and subsequently oxidized to 11-cis retinal as part of the retina visual cycle. However, the molecular identity of the cis retinol oxidase in cones remains unclear. Here, as a first step in characterizing this enzymatic reaction, we sought to determine the subcellular localization of this activity in salamander red cones. We found that the onset of dark adaptation of isolated salamander red cones was substantially faster when exposing directly their outer vs. their inner segment to 9-cis retinol, an analogue of 11-cis retinol. In contrast, this difference was not observed when treating the outer vs. inner segment with 9-cis retinal, a chromophore analogue which can directly support pigment regeneration. These results suggest, surprisingly, that the cis-retinol oxidation occurs in the outer segments of cone photoreceptors. Confirming this notion, pigment regeneration with exogenously added 9-cis retinol was directly observed in the truncated outer segments of cones, but not in rods. We conclude that the enzymatic machinery required for the oxidation of recycled cis retinol as part of the retina visual cycle is present in the outer segments of cones.

  19. A Cone Shaped Hill

    NASA Image and Video Library

    2015-10-14

    There are many hills and knobs on Mars that reveal aspects of the local geologic history. Typically, the hills in the relatively-smooth region surrounding this image are flat topped erosional remnants or mesas with irregular or even polyhedral margins. These landforms suggest wide spread erosion of the soft or weakly-cemented sedimentary layers. This hill stands out because of is circular inverted-cone shape and apparent dark streaks along its flanks visible in lower resolution images. Close inspection from HiRISE reveals that the fine soils sloping down from the peak are intersected with radiating lines of rock and eroding rubble. This formation is similar to lava intrusions that form in the core of a volcano. As lava is squeezed up into a central conduit, radiating fractures fill with lava forming rock units called dikes. As the lava cools inside the ground and in the fractures, it forms into a harder rock that is more resistant to erosion. Later, as the surrounding sediments and soils erode, the resistant volcanic rock remains standing to tell a story of what happened underground long ago. http://photojournal.jpl.nasa.gov/catalog/PIA20003

  20. The Repeatability of In Vivo Parafoveal Cone Density and Spacing Measurementsa

    PubMed Central

    Garrioch, Robert; Langlo, Christopher; Dubis, Adam M.; Cooper, Robert F.; Dubra, Alf; Carroll, Joseph

    2012-01-01

    Purpose To assess the repeatability and measurement error associated with cone density and nearest neighbor distance (NND) estimates in images of the parafoveal cone mosaic obtained with an adaptive optics scanning light ophthalmoscope (AOSLO). Methods Twenty-one participants with no known ocular pathology were recruited. Four retinal locations, approximately 0.65° eccentricity from the center of fixation were imaged 10 times in randomized order with an AOSLO. Cone coordinates in each image were identified using an automated algorithm (with or without manual correction), from which cone density and NND were calculated. Owing to naturally occurring fixational instability, the 10 images recorded from a given location did not overlap entirely. We thus analyzed each image set both before and after alignment. Results Automated estimates of cone density on the unaligned image sets showed a coefficient of repeatability of 11,769 cones/mm2 (17.1%). The primary reason for this variability appears to be fixational instability, as aligning the 10 images to include the exact same retinal area, results in an improved repeatability of 4,358 cones/mm2 (6.4%) using completely automated cone identification software. Repeatability improved further by manually identifying cones missed by the automated algorithm, with a coefficient of repeatability of 1,967 cones/mm2 (2.7%). NND showed improved repeatability, and was generally insensitive to the undersampling by the automated algorithm. Conclusions As our data were collected in a young, healthy population, this likely represents a best-case estimate for corresponding measurements in patients with retinal disease. Similar studies need to be carried out on other imaging systems (including those using different imaging modalities, wavefront correction technology, and/or cone identification software), as repeatability would be expected to be highly sensitive to initial image quality and the performance of cone identification algorithms

  1. Unusual cone and rod properties in subterranean African mole-rats (Rodentia, Bathyergidae).

    PubMed

    Peichl, Leo; Nemec, Pavel; Burda, Hynek

    2004-03-01

    We have determined the presence of spectral cone types, and the population densities of cones and rods, in subterranean mole-rats of the rodent family Bathyergidae, for which light and vision seems of little importance. Most mammals have two spectral cone types, a majority of middle- to long-wave-sensitive (L-) cones, and a minority of short-wave-sensitive (S-)cones. We were interested to see whether the subterranean bathyergids show the same pattern. In three species, Ansell's mole-rat Cryptomys anselli, the giant mole-rat Cryptomys mechowi and the naked mole-rat Heterocephalus glaber, spectral cone types and rods were assessed immunocytochemically with opsin-specific antibodies. All three species had rod-dominated retinae but possessed significant cone populations. A quantitative assessment in C. anselli and C. mechowi revealed surprisingly low photoreceptor densities of 100 000-150 000/mm(2), and high cone proportions, approximately 10% (8000-15 000/mm(2)). In all three species, the vast majority of the cones were strongly S-opsin-immunoreactive; L-opsin immunoreactivity was much fainter. In C. anselli, approximately 20% of the cones showed exclusive S-opsin label, approximately 10% exclusive L-opsin label and approximately 70% strong S-opsin and faint L-opsin double label (potential dual-pigment cones). This is the first observation in any mammal of an S-opsin dominance and low levels of L-opsin across the entire retina. It contrasts starkly with the situation in the muroid blind mole-rat Spalax ehrenbergi, which has been reported to possess L-opsin but no S-opsin. Evidently, within rodents an adaptation to subterranean life is compatible with very different spectral cone properties.

  2. Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency.

    PubMed

    Patterson, Emily J; Wilk, Melissa; Langlo, Christopher S; Kasilian, Melissa; Ring, Michael; Hufnagel, Robert B; Dubis, Adam M; Tee, James J; Kalitzeos, Angelos; Gardner, Jessica C; Ahmed, Zubair M; Sisk, Robert A; Larsen, Michael; Sjoberg, Stacy; Connor, Thomas B; Dubra, Alfredo; Neitz, Jay; Hardcastle, Alison J; Neitz, Maureen; Michaelides, Michel; Carroll, Joseph

    2016-07-01

    Mutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/M opsin gene mutations to clarify the link between color vision deficiency and cone dysfunction. We recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone mosaic obtained with adaptive optics scanning light ophthalmoscopy. The L/M opsin gene array was characterized in 16 subjects, including at least one subject from each family. There were six subjects with the LVAVA haplotype encoded by exon 3, seven with LIAVA, two with the Cys203Arg mutation encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array. Our findings provide a direct link between disruption of the cone mosaic and L/M opsin variants. We hypothesize that, in addition to large phenotypic differences between different L/M opsin variants, the ratio of expression of first versus downstream genes in the L/M array contributes to phenotypic diversity. While the L/M opsin mutations underlie the cone dysfunction in all of the subjects tested, the color vision defect can be caused either by the same mutation or a gene rearrangement at the same locus.

  3. Cone Photoreceptor Structure in Patients With X-Linked Cone Dysfunction and Red-Green Color Vision Deficiency

    PubMed Central

    Patterson, Emily J.; Wilk, Melissa; Langlo, Christopher S.; Kasilian, Melissa; Ring, Michael; Hufnagel, Robert B.; Dubis, Adam M.; Tee, James J.; Kalitzeos, Angelos; Gardner, Jessica C.; Ahmed, Zubair M.; Sisk, Robert A.; Larsen, Michael; Sjoberg, Stacy; Connor, Thomas B.; Dubra, Alfredo; Neitz, Jay; Hardcastle, Alison J.; Neitz, Maureen; Michaelides, Michel; Carroll, Joseph

    2016-01-01

    Purpose Mutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/M opsin gene mutations to clarify the link between color vision deficiency and cone dysfunction. Methods We recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone mosaic obtained with adaptive optics scanning light ophthalmoscopy. The L/M opsin gene array was characterized in 16 subjects, including at least one subject from each family. Results There were six subjects with the LVAVA haplotype encoded by exon 3, seven with LIAVA, two with the Cys203Arg mutation encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array. Conclusions Our findings provide a direct link between disruption of the cone mosaic and L/M opsin variants. We hypothesize that, in addition to large phenotypic differences between different L/M opsin variants, the ratio of expression of first versus downstream genes in the L/M array contributes to phenotypic diversity. While the L/M opsin mutations underlie the cone dysfunction in all of the subjects tested, the color vision defect can be caused either by the same mutation or a gene rearrangement at the same locus. PMID:27447086

  4. Optical influence of oil droplets on cone photoreceptor sensitivity.

    PubMed

    Wilby, David; Roberts, Nicholas W

    2017-03-17

    Oil droplets are spherical organelles found in the cone photoreceptors of vertebrates. They are generally assumed to focus incident light into the outer segment, and thereby improve light catch because of the droplets' spherical lens-like shape. However, using full-wave optical simulations of physiologically realistic cone photoreceptors from birds, frogs and turtles we find that pigmented oil droplets actually drastically reduce the transmission of light into the outer segment integrated across the full visible wavelength range of each species. Only transparent oil droplets improve light catch into the outer segments, and any enhancement is critically dependent on the refractive index, diameter of the oil droplet, and diameter and length of the outer segment. Furthermore, oil droplets are not the only optical elements found in cone inner segments. The ellipsoid, a dense aggregation of mitochondria situated immediately prior to the oil droplet, mitigates the loss of light at oil droplet surface. We describe a framework for integrating these optical phenomena into simple models of receptor sensitivity and the relevance of these observations to evolutionary appearance and loss of oil droplets is discussed.

  5. The p110α isoform of phosphoinositide 3-kinase is essential for cone photoreceptor survival.

    PubMed

    Rajala, Raju V S; Ranjo-Bishop, Michelle; Wang, Yuhong; Rajala, Ammaji; Anderson, Robert E

    2015-05-01

    Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that phosphorylates the 3'OH of the inositol ring of phosphoinositides (PIs). They are responsible for coordinating a diverse range of cellular functions. Class IA PI3K is a heterodimeric protein composed of a regulatory p85 and a catalytic p110 subunit. In this study, we conditionally deleted the p110α-subunit of PI3K in cone photoreceptor cells using the Cre-loxP system. Cone photoreceptors allow for color vision in bright light (daylight vision). Cone-specific deletion of p110α resulted in cone degeneration. Our studies suggest that PI3K signaling is essential for cone photoreceptor functions. Copyright © 2015 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  6. Shatter cones at sierra madera, Texas.

    PubMed

    Howard, K A; Offield, T W

    1968-10-11

    Shatter cones abound in the central uplift of Sierra Madera and they occur as far as 6.5 kilometers from the center. Apical angles average near 90 degrees. Whole cones and full cones represented by diversely oriented cone segments in any structural block show relatively uniform orientations of axes and a dominant direction of point. The cones predate faulting and folding in the central uplift, and, when beds are restored to horizontal, most cones point inward and upward, a pattern that supports the hypothesis of an impact origin.

  7. Non-dissipative electromagnetic media with two Lorentz null cones

    SciTech Connect

    Dahl, Matias F.

    2013-03-15

    We study Maxwell's equations on a 4-manifold where the electromagnetic medium is modeled by an antisymmetric (2/2 )-tensor with 21 real coefficients. In this setting the Fresnel surface is a fourth-order polynomial surface that describes the dynamical response of the medium in the geometric optics limit. For example, in an isotropic medium the Fresnel surface is a Lorentz null cone. The contribution of this paper is the pointwise description of all electromagnetic medium tensors {kappa} with real coefficients that satisfy the following three conditions: (i)medium {kappa} is invertible, (ii)medium {kappa} is skewon-free, or non-dissipative, (iii)the Fresnel surface of {kappa} is the union of two distinct Lorentz null cones. We show that there are only three classes of media with these properties and give explicit expressions in local coordinates for each class. - Highlights: Black-Right-Pointing-Pointer We find two new electromagnetic media classes for which the Fresnel surface decomposes into two light cones. Black-Right-Pointing-Pointer In a suitable setting we classify all electromagnetic media where this is the case. Black-Right-Pointing-Pointer We find an electromagnetic medium tensor with three different signal speeds in one direction. Black-Right-Pointing-Pointer The work is related to [5], which classifies all media with one light cone (in a suitable setting).

  8. Quantitative and Topographical Analysis of the Losses of Cone Photoreceptors and Retinal Ganglion Cells Under Taurine Depletion.

    PubMed

    Hadj-Saïd, Wahiba; Froger, Nicolas; Ivkovic, Ivana; Jiménez-López, Manuel; Dubus, Élisabeth; Dégardin-Chicaud, Julie; Simonutti, Manuel; Quénol, César; Neveux, Nathalie; Villegas-Pérez, María Paz; Agudo-Barriuso, Marta; Vidal-Sanz, Manuel; Sahel, Jose-Alain; Picaud, Serge; García-Ayuso, Diego

    2016-09-01

    Taurine depletion is known to induce photoreceptor degeneration and was recently found to also trigger retinal ganglion cell (RGC) loss similar to the retinal toxicity of vigabatrin. Our objective was to study the topographical loss of RGCs and cone photoreceptors, with a distinction between the two cone types (S- and L- cones) in an animal model of induced taurine depletion. We used the taurine transporter (Tau-T) inhibitor, guanidoethane sulfonate (GES), to induce taurine depletion at a concentration of 1% in the drinking water. Spectral-domain optical coherence tomography (SD-OCT) and electroretinograms (ERG) were performed on animals after 2 months of GES treatment administered through the drinking water. Retinas were dissected as wholemounts and immunodetection of Brn3a (RGC), S-opsin (S-cones), and L-opsin (L-cones) was performed. The number of Brn3a+ RGCs, and L- and S-opsin+ cones was automatically quantified and their retinal distribution studied using isodensity maps. The treatment resulted in a significant reduction in plasma taurine levels and a profound dysfunction of visual performance as shown by ERG recordings. Optical coherence tomography analysis revealed that the retina was thinner in the taurine-depleted group. S-opsin+cones were more affected (36%) than L-opsin+cones (27%) with greater cone cell loss in the dorsal area whereas RGC loss (12%) was uniformly distributed. This study confirms that taurine depletion causes RGC and cone loss. Electroretinograms results show that taurine depletion induces retinal dysfunction in photoreceptors and in the inner retina. It establishes a gradient of cell loss depending on the cell type from S-opsin+cones, L-opsin+cones, to RGCs. The greater cell loss in the dorsal retina and of the S-cone population may underline different cellular mechanisms of cellular degeneration and suggests that S-cones may be more sensitive to light-induced retinal toxicity enhanced by the taurine depletion.

  9. Acute Zonal Cone Photoreceptor Outer Segment Loss.

    PubMed

    Aleman, Tomas S; Sandhu, Harpal S; Serrano, Leona W; Traband, Anastasia; Lau, Marisa K; Adamus, Grazyna; Avery, Robert A

    2017-05-01

    The diagnostic path presented narrows down the cause of acute vision loss to the cone photoreceptor outer segment and will refocus the search for the cause of similar currently idiopathic conditions. To describe the structural and functional associations found in a patient with acute zonal occult photoreceptor loss. A case report of an adolescent boy with acute visual field loss despite a normal fundus examination performed at a university teaching hospital. Results of a complete ophthalmic examination, full-field flash electroretinography (ERG) and multifocal ERG, light-adapted achromatic and 2-color dark-adapted perimetry, and microperimetry. Imaging was performed with spectral-domain optical coherence tomography (SD-OCT), near-infrared (NIR) and short-wavelength (SW) fundus autofluorescence (FAF), and NIR reflectance (REF). The patient was evaluated within a week of the onset of a scotoma in the nasal field of his left eye. Visual acuity was 20/20 OU, and color vision was normal in both eyes. Results of the fundus examination and of SW-FAF and NIR-FAF imaging were normal in both eyes, whereas NIR-REF imaging showed a region of hyporeflectance temporal to the fovea that corresponded with a dense relative scotoma noted on light-adapted static perimetry in the left eye. Loss in the photoreceptor outer segment detected by SD-OCT co-localized with an area of dense cone dysfunction detected on light-adapted perimetry and multifocal ERG but with near-normal rod-mediated vision according to results of 2-color dark-adapted perimetry. Full-field flash ERG findings were normal in both eyes. The outer nuclear layer and inner retinal thicknesses were normal. Localized, isolated cone dysfunction may represent the earliest photoreceptor abnormality or a distinct entity within the acute zonal occult outer retinopathy complex. Acute zonal occult outer retinopathy should be considered in patients with acute vision loss and abnormalities on NIR-REF imaging, especially if

  10. Cone outer segment shedding in the goldfish retina characterized with the /sup 3/H-fucose technique

    SciTech Connect

    Balkema, G.W. Jr.; Bunt-Milam, A.H.

    1982-09-01

    After an intravitreal injection of /sup 3/H-fucose, red- and blue-sensitive cone outer segments (OSs) in the goldfish retina became heavily labeled, green-sensitive cone OSs showed light labeling, and rod OSs showed virtually no labeling. Fish were maintained in white light (light/dark: 12 hr/12 hr; 6 to 10 weeks) and were injected with /sup 3/H-fucose 24 hr before sacrifice. After light onset, only phagosomes with no label were found in the retinal pigment epithelium (RPE); after light offset, phagosomes with heavy, light, or no label were found in the RPE. A broad peak of cone OS shedding derived from all cone types was found beginning 2 hr after light offset and returning to baseline levels after 12 hr, with a maximum at 4 to 6 hr. When the white light was replaced with red light during the final 24 hr (irradiance matched to the white light at 625 nm), the green cones showed a reduction in shedding by 62%, the rods showed a 48% reduction in shedding, and the number of heavily labeled phagosomes was reduced by 24% (a value that may reflect normal and red cone shedding and a reduction in blue cone shedding). The results suggest that chromatic stimulation during the light period may influence the shedding response of a given class of cone OS. Finally, the /sup 3/H-fucose technique is useful for determination of the photoreceptor OS from which a given phagosome in the RPE originates in this species.

  11. Selective Stimulation of Penumbral Cones Reveals Perception in the Shadow of Retinal Blood Vessels

    PubMed Central

    Spitschan, Manuel; Aguirre, Geoffrey K.; Brainard, David H.

    2015-01-01

    In 1819, Johann Purkinje described how a moving light source that displaces the shadow of the retinal blood vessels to adjacent cones can produce the entopic percept of a branching tree. Here, we describe a novel method for producing a similar percept. We used a device that mixes 56 narrowband primaries under computer control, in conjunction with the method of silent substitution, to present observers with a spectral modulation that selectively targeted penumbral cones in the shadow of the retinal blood vessels. Such a modulation elicits a clear Purkinje-tree percept. We show that the percept is specific to penumbral L and M cone stimulation and is not produced by selective penumbral S cone stimulation. The Purkinje-tree percept was strongest at 16 Hz and fell off at lower (8 Hz) and higher (32 Hz) temporal frequencies. Selective stimulation of open-field cones that are not in shadow, with penumbral cones silenced, also produced the percept, but it was not seen when penumbral and open-field cones were modulated together. This indicates the need for spatial contrast between penumbral and open-field cones to create the Purkinje-tree percept. Our observation provides a new means for studying the response of retinally stabilized images and demonstrates that penumbral cones can support spatial vision. Further, the result illustrates a way in which silent substitution techniques can fail to be silent. We show that inadvertent penumbral cone stimulation can accompany melanopsin-directed modulations that are designed only to silence open-field cones. This in turn can result in visual responses that might be mistaken as melanopsin-driven. PMID:25897842

  12. Evaluating outer segment length as a surrogate measure of peak foveal cone density.

    PubMed

    Wilk, Melissa A; Wilk, Brandon M; Langlo, Christopher S; Cooper, Robert F; Carroll, Joseph

    2017-01-01

    Adaptive optics (AO) imaging tools enable direct visualization of the cone photoreceptor mosaic, which facilitates quantitative measurements such as cone density. However, in many individuals, low image quality or excessive eye movements precludes making such measures. As foveal cone specialization is associated with both increased density and outer segment (OS) elongation, we sought to examine whether OS length could be used as a surrogate measure of foveal cone density. The retinas of 43 subjects (23 normal and 20 albinism; aged 6-67years) were examined. Peak foveal cone density was measured using confocal adaptive optics scanning light ophthalmoscopy (AOSLO), and OS length was measured using optical coherence tomography (OCT) and longitudinal reflectivity profile-based approach. Peak cone density ranged from 29,200 to 214,000cones/mm(2) (111,700±46,300cones/mm(2)); OS length ranged from 26.3 to 54.5μm (40.5±7.7μm). Density was significantly correlated with OS length in albinism (p<0.0001), but not normals (p=0.99). A cubic model of density as a function of OS length was created based on histology and optimized to fit the albinism data. The model includes triangular cone packing, a cylindrical OS with a fixed volume of 136.6μm(3), and a ratio of OS to inner segment width that increased linearly with increasing OS length (R(2)=0.72). Normal subjects showed no apparent relationship between cone density and OS length. In the absence of adequate AOSLO imagery, OS length may be used to estimate cone density in patients with albinism. Whether this relationship exists in other patient populations with foveal hypoplasia (e.g., premature birth, aniridia, isolated foveal hypoplasia) remains to be seen. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Selective stimulation of penumbral cones reveals perception in the shadow of retinal blood vessels.

    PubMed

    Spitschan, Manuel; Aguirre, Geoffrey K; Brainard, David H

    2015-01-01

    In 1819, Johann Purkinje described how a moving light source that displaces the shadow of the retinal blood vessels to adjacent cones can produce the entopic percept of a branching tree. Here, we describe a novel method for producing a similar percept. We used a device that mixes 56 narrowband primaries under computer control, in conjunction with the method of silent substitution, to present observers with a spectral modulation that selectively targeted penumbral cones in the shadow of the retinal blood vessels. Such a modulation elicits a clear Purkinje-tree percept. We show that the percept is specific to penumbral L and M cone stimulation and is not produced by selective penumbral S cone stimulation. The Purkinje-tree percept was strongest at 16 Hz and fell off at lower (8 Hz) and higher (32 Hz) temporal frequencies. Selective stimulation of open-field cones that are not in shadow, with penumbral cones silenced, also produced the percept, but it was not seen when penumbral and open-field cones were modulated together. This indicates the need for spatial contrast between penumbral and open-field cones to create the Purkinje-tree percept. Our observation provides a new means for studying the response of retinally stabilized images and demonstrates that penumbral cones can support spatial vision. Further, the result illustrates a way in which silent substitution techniques can fail to be silent. We show that inadvertent penumbral cone stimulation can accompany melanopsin-directed modulations that are designed only to silence open-field cones. This in turn can result in visual responses that might be mistaken as melanopsin-driven.

  14. Shatter cones: (Mis)understood?

    PubMed Central

    Osinski, Gordon R.; Ferrière, Ludovic

    2016-01-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and “double” cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship Dsc = 0.4 Da, where Dsc is the maximum spatial extent of in situ shatter cones, and Da is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact. PMID:27532050

  15. Shatter cones: (Mis)understood?

    PubMed

    Osinski, Gordon R; Ferrière, Ludovic

    2016-08-01

    Meteorite impact craters are one of the most common geological features in the solar system. An impact event is a near-instantaneous process that releases a huge amount of energy over a very small region on a planetary surface. This results in characteristic changes in the target rocks, from vaporization and melting to solid-state effects, such as fracturing and shock metamorphism. Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events. They are one of the most used and trusted shock-metamorphic effects for the recognition of meteorite impact structures. Despite this, there is still considerable debate regarding their formation. We show that shatter cones are present in several stratigraphic settings within and around impact structures. Together with the occurrence of complete and "double" cones, our observations are most consistent with shatter cone formation due to tensional stresses generated by scattering of the shock wave due to heterogeneities in the rock. On the basis of field mapping, we derive the relationship D sc = 0.4 D a, where D sc is the maximum spatial extent of in situ shatter cones, and D a is the apparent crater diameter. This provides an important, new, more accurate method to estimate the apparent diameter of eroded complex craters on Earth. We have reestimated the diameter of eight well-known impact craters as part of this study. Finally, we suggest that shatter cones may reduce the strength of the target, thus aiding crater collapse, and that their distribution in central uplifts also records the obliquity of impact.

  16. In Vivo Two-Photon Fluorescence Kinetics of Primate Rods and Cones

    PubMed Central

    Sharma, Robin; Schwarz, Christina; Williams, David R.; Palczewska, Grazyna; Palczewski, Krzysztof; Hunter, Jennifer J.

    2016-01-01

    Purpose The retinoid cycle maintains vision by regenerating bleached visual pigment through metabolic events, the kinetics of which have been difficult to characterize in vivo. Two-photon fluorescence excitation has been used previously to track autofluorescence directly from retinoids and pyridines in the visual cycle in mouse and frog retinas, but the mechanisms of the retinoid cycle are not well understood in primates. Methods We developed a two-photon fluorescence adaptive optics scanning light ophthalmoscope dedicated to in vivo imaging in anesthetized macaques. Using pulsed light at 730 nm, two-photon fluorescence was captured from rods and cones during light and dark adaptation through the eye's pupil. Results The fluorescence from rods and cones increased with light exposure but at different rates. During dark adaptation, autofluorescence declined, with cone autofluorescence decreasing approximately 4 times faster than from rods. Rates of autofluorescence decrease in rods and cones were approximately 4 times faster than their respective rates of photopigment regeneration. Also, subsets of sparsely distributed cones were less fluorescent than their neighbors immediately following bleach at 565 nm and they were comparable with the S cone mosaic in density and distribution. Conclusions Although other molecules could be contributing, we posit that these fluorescence changes are mediated by products of the retinoid cycle. In vivo two-photon ophthalmoscopy provides a way to monitor noninvasively stages of the retinoid cycle that were previously inaccessible in the living primate eye. This can be used to assess objectively photoreceptor function in normal and diseased retinas. PMID:26903225

  17. Outcome measure for the treatment of cone photoreceptor diseases: orientation to a scene with cone-only contrast.

    PubMed

    Roman, Alejandro J; Cideciyan, Artur V; Matsui, Rodrigo; Sheplock, Rebecca; Schwartz, Sharon B; Jacobson, Samuel G

    2015-08-08

    Inherited retinal degenerations (IRDs) preferentially affecting cone photoreceptor function are being considered for treatment trials aiming to improve day vision. The purpose of the current work was to develop cone-specific visual orientation outcomes that can differentiate day vision improvement in the presence of retained night vision. A lighted wall (1.4 m wide, 2 m high) resembling a beaded curtain was formed with 900 individually addressable red, blue and green LED triplets placed in 15 vertical strips hanging 0.1 m apart. Under computer control, different combination of colors and intensities were used to produce the appearance of a door on the wall. Scotopically-matched trials were designed to be perceptible to the cone-, but not rod-, photoreceptor based visual systems. Unmatched control trials were interleaved at each luminance level to determine the existence of any vision available for orientation. Testing started with dark-adapted eyes and a scene luminance attenuated 8 log units from the maximum attainable, and continued with progressively increasing levels of luminance. Testing was performed with a three-alternative forced choice method in healthy subjects and patients with Leber congenital amaurosis (LCA) caused by mutations in GUCY2D, the gene that encodes retinal guanylate cyclase-1. Normal subjects could perform the orientation task using cone vision at 5 log attenuation and brighter luminance levels. Most GUCY2D-LCA patients failed to perform the orientation task with scotopically-matched test trials at any luminance level even though they were able to perform correctly with unmatched control trials. These results were consistent with a lack of cone system vision and use of the rod system under ambient conditions normally associated with cone system activity. Two GUCY2D-LCA patients demonstrated remnant cone vision but at a luminance level 2 log brighter than normal. The newly developed device can probe the existence or emergence of cone

  18. An analytical model of the influence of cone sensitivity and numerosity on the Rayleigh match

    PubMed Central

    Zhaoping, Li; Carroll, Joseph

    2016-01-01

    The Rayleigh match is defined by the range of mixtures of red and green lights that appear the same as an intensity-adjustable monochromatic yellow light. The perceptual match indicates that the red/green mixture and the yellow light have evoked the same respective cone absorptions in the L- and M-cone pathways. Going beyond the existing models (e.g., Pokorny et al 1973, He & Shevell, 1995; Thomas & Mollon, 2004; Barbur et al 2008), the Poisson noise in cone absorptions is proposed to make the matching proportion of red-green mixtures span a finite range, since any mixture in that range evokes cone absorptions that do not differ from those by a yellow light by more than the variations in the absorption noise. We derive a mathematical formula linking the match midpoint or match range with the sensitivities and numerosities of the two cones. The noise-free, exact, matching point, close to the mid-point of the matching range, depends only on the L- and M-cone sensitivities to each of the red, green, and yellow lights (these sensitivities in turn depend on the preferred wavelengths (λmax) and optical densities of the cone pigments and the various pre-receptor retinal light filtering properties). Meanwhile, the matching range depends on both these cone sensitivities and the relative numerosity of the L- and M-cones. The model predicts that, in normal trichromats, all other things being equal, the match range is smallest when the ratio r between L and M cone densities is r = R−1/2 with R as the ratio between the sensitivities of the L and M cones to the yellow light, i.e., when L and M cones are similarly abundant in typical cases, and as r departs from R−1/2 the match range increases. For example, when one cone type is 10 times more numerous, the match range increases 2-3 fold, depending on the sensitivities of the cones. Testing these model predictions requires either a large data set to identify the effect of one factor (e.g., cone numerosity) while averaging out

  19. Longitudinal evaluation of expression of virally delivered transgenes in gerbil cone photoreceptors

    PubMed Central

    Mauck, Matthew C.; Mancuso, Katherine; Kuchenbecker, James A.; Connor, Thomas B.; Hauswirth, William W.; Neitz, Jay; Neitz, Maureen

    2008-01-01

    Delivery of foreign opsin genes to cone photoreceptors using recombinant adeno-associated virus (rAAV) is a potential tool for studying the basic mechanisms underlying cone based vision and for treating vision disorders. We used an in vivo retinal imaging system to monitor, over time, expression of virally-delivered genes targeted to cone photoreceptors in the Mongolian gerbil (Meriones unguiculatus). Gerbils have a well-developed photopic visual system, with 11-14% of their photoreceptors being cones. We used replication deficient serotype 5 rAAV to deliver a gene for green fluorescent protein (GFP). In an effort to direct expression of the gene specifically to either S or M cones, the transgene was under the control of either the human X-chromosome opsin gene regulatory elements, i.e., an enhancer termed the Locus Control Region (LCR) and L promoter, or the human S-opsin promoter. Longitudinal fluorescence images reveal that gene expression is first detectable about 14 days post-injection, reaches a peak after about 3 months, and is observed more than a year post-injection if the initial viral concentration is sufficiently high. The regulatory elements are able to direct expression to a subpopulation of cones while excluding expression in rods and non-photoreceptor retinal cells. When the same viral constructs are used to deliver a human long-wavelength opsin gene to gerbil cones, stimulation of the introduced human photopigment with long-wavelength light produces robust cone responses. PMID:18598398

  20. The current state of knowledge about shatter cones: Introduction to the special issue

    NASA Astrophysics Data System (ADS)

    Baratoux, David; Reimold, Wolf Uwe

    2016-08-01

    Shatter cones are a fracture phenomenon that is exclusively associated with shock metamorphism and has also been produced in the laboratory in several shock experiments. The occurrence of shatter cones is the only accepted meso- to macroscopic recognition criterion for impact structures. Shatter cones exhibit a number of geometric characteristics (orientation, apical angles, striation angles, sizes) that can be best described as varied, from case to case. Possible links between geometric properties with impact or crater parameters have remained controversial and the lack of understanding of the mechanism of formation of shatter cones does not offer a physical framework to discuss or understand them. A database of shatter cone occurrences has been produced for this introduction paper to the special issue of Meteoritics and Planetary Science on shatter cones. Distribution of shatter cones with respect to crater size and lithology suggests that shatter cones do not occur in impact craters less than a few kilometers in diameter, with a few, currently questionable exceptions. All pertinent hypotheses of formation are presented and discussed. Several may be discarded in light of the most recent observations. The branching fracture mechanism and the interference models proposed, respectively, by Sagy et al. (2002) and Baratoux and Melosh (2003) require further evaluation. New observations, experiments, or theoretical considerations presented in this special issue promise an important step forward, based on a renewed effort to resolve the enigmatic origin of these important features.

  1. Evolutionary transformation of rod photoreceptors in the all-cone retina of a diurnal garter snake.

    PubMed

    Schott, Ryan K; Müller, Johannes; Yang, Clement G Y; Bhattacharyya, Nihar; Chan, Natalie; Xu, Mengshu; Morrow, James M; Ghenu, Ana-Hermina; Loew, Ellis R; Tropepe, Vincent; Chang, Belinda S W

    2016-01-12

    Vertebrate retinas are generally composed of rod (dim-light) and cone (bright-light) photoreceptors with distinct morphologies that evolved as adaptations to nocturnal/crepuscular and diurnal light environments. Over 70 years ago, the "transmutation" theory was proposed to explain some of the rare exceptions in which a photoreceptor type is missing, suggesting that photoreceptors could evolutionarily transition between cell types. Although studies have shown support for this theory in nocturnal geckos, the origins of all-cone retinas, such as those found in diurnal colubrid snakes, remain a mystery. Here we investigate the evolutionary fate of the rods in a diurnal garter snake and test two competing hypotheses: (i) that the rods, and their corresponding molecular machinery, were lost or (ii) that the rods were evolutionarily modified to resemble, and function, as cones. Using multiple approaches, we find evidence for a functional and unusually blue-shifted rhodopsin that is expressed in small single "cones." Moreover, these cones express rod transducin and have rod ultrastructural features, providing strong support for the hypothesis that they are not true cones, as previously thought, but rather are modified rods. Several intriguing features of garter snake rhodopsin are suggestive of a more cone-like function. We propose that these cone-like rods may have evolved to regain spectral sensitivity and chromatic discrimination as a result of ancestral losses of middle-wavelength cone opsins in early snake evolution. This study illustrates how sensory evolution can be shaped not only by environmental constraints but also by historical contingency in forming new cell types with convergent functionality.

  2. Evolutionary transformation of rod photoreceptors in the all-cone retina of a diurnal garter snake

    PubMed Central

    Schott, Ryan K.; Müller, Johannes; Yang, Clement G. Y.; Bhattacharyya, Nihar; Chan, Natalie; Xu, Mengshu; Morrow, James M.; Ghenu, Ana-Hermina; Loew, Ellis R.; Tropepe, Vincent; Chang, Belinda S. W.

    2016-01-01

    Vertebrate retinas are generally composed of rod (dim-light) and cone (bright-light) photoreceptors with distinct morphologies that evolved as adaptations to nocturnal/crepuscular and diurnal light environments. Over 70 years ago, the “transmutation” theory was proposed to explain some of the rare exceptions in which a photoreceptor type is missing, suggesting that photoreceptors could evolutionarily transition between cell types. Although studies have shown support for this theory in nocturnal geckos, the origins of all-cone retinas, such as those found in diurnal colubrid snakes, remain a mystery. Here we investigate the evolutionary fate of the rods in a diurnal garter snake and test two competing hypotheses: (i) that the rods, and their corresponding molecular machinery, were lost or (ii) that the rods were evolutionarily modified to resemble, and function, as cones. Using multiple approaches, we find evidence for a functional and unusually blue-shifted rhodopsin that is expressed in small single “cones.” Moreover, these cones express rod transducin and have rod ultrastructural features, providing strong support for the hypothesis that they are not true cones, as previously thought, but rather are modified rods. Several intriguing features of garter snake rhodopsin are suggestive of a more cone-like function. We propose that these cone-like rods may have evolved to regain spectral sensitivity and chromatic discrimination as a result of ancestral losses of middle-wavelength cone opsins in early snake evolution. This study illustrates how sensory evolution can be shaped not only by environmental constraints but also by historical contingency in forming new cell types with convergent functionality. PMID:26715746

  3. Two Shatter-Coned NWA Meteorites

    NASA Astrophysics Data System (ADS)

    McHone, J. F.; Shoemaker, C.; Killgore, M.; Killgore, K.

    2012-03-01

    Shatter cones are found in target rocks at more than 70 terrestrial impact sites and are regarded as reliable field criteria for meteoroid impact events. Shatter cones are now seen in chondritic meteorites and indicate early collision events.

  4. Cone Penetrometer N Factor Determination Testing Results

    SciTech Connect

    Follett, Jordan R.

    2014-03-05

    This document contains the results of testing activities to determine the empirical 'N Factor' for the cone penetrometer in kaolin clay simulant. The N Factor is used to releate resistance measurements taken with the cone penetrometer to shear strength.

  5. Direct rod input to cone BCs and direct cone input to rod BCs challenge the traditional view of mammalian BC circuitry

    PubMed Central

    Pang, Ji-Jie; Gao, Fan; Lem, Janis; Bramblett, Debra E.; Paul, David L.; Wu, Samuel M.

    2009-01-01

    Bipolar cells are the central neurons of the retina that transmit visual signals from rod and cone photoreceptors to third-order neurons in the inner retina and the brain. A dogma set forth by early anatomical studies is that bipolar cells in mammalian retinas receive segregated rod/cone synaptic inputs (either from rods or from cones), and here, we present evidence that challenges this traditional view. By analyzing light-evoked cation currents from morphologically identified depolarizing bipolar cells (DBCs) in the wild-type and three pathway-specific knockout mice (rod transducin knockout [Trα−/−], connexin36 knockout [Cx36−/−], and transcription factor beta4 knockout [Bhlhb4−/−]), we show that a subpopulation of rod DBCs (DBCR2s) receives substantial input directly from cones and a subpopulation of cone DBCs (DBCC1s) receives substantial input directly from rods. These results provide evidence of the existence of functional rod-DBCC and cone-DBCR synaptic pathways in the mouse retina as well as the previously proposed rod hyperpolarizing bipolar-cells pathway. This is grounds for revising the mammalian rod/cone bipolar cell dogma. PMID:20018684

  6. Direct fabrication of cone array microstructure on monocrystalline silicon surface by femtosecond laser texturing

    NASA Astrophysics Data System (ADS)

    Wang, Quanji; Zhou, Weidong

    2017-10-01

    Improving the utilization ratio of sunlight is a key factor for the development of solar cell. In this paper, a quasi uniform cone-array-like microstructure was directly fabricated on monocrystal silicon surface in atmosphere by using an alternative femtosecond laser texturing technique. The fabricated cone array like microstructure has a spike depth of up to 8 μm and is able to substantially reduce light reflection due to the effective optical coupling between the incident light with the cone array like microstructure. Compare to planar silicon wafer, the relative reflectance of the cone array structure has been decreased to less than 9% in the measured wavelength range from 400 to 1000 nm. This may be a promising method for the optimal fabrication of surface-microstructure photovoltaic material, such as solar cell, infrared sensor, etc.

  7. Internal Reflection Sensor for the Cone Penetrometer. Innovative Technology Summary Report

    SciTech Connect

    2001-09-01

    The Internal Reflection Sensor, developed by EIC Laboratories, Inc. as a cone penetrometer based technology, provides real-time detection of subsurface non-aqueous phase liquids (NAPLs). The internal reflection element is positioned against the wall of the cone penetrometer probe such that its sensing face is in contact with the soil or groundwater as the cone is pushed into the subsurface. When NAPL is present and in contact with the sensing face, the internally reflected light is diminished. This results in a decrease in the signal output by the detector - a positive indicator of NAPL presence.

  8. Small Molecules in the Cone Snail Arsenal.

    PubMed

    Neves, Jorge L B; Lin, Zhenjian; Imperial, Julita S; Antunes, Agostinho; Vasconcelos, Vitor; Olivera, Baldomero M; Schmidt, Eric W

    2015-10-16

    Cone snails are renowned for producing peptide-based venom, containing conopeptides and conotoxins, to capture their prey. A novel small-molecule guanine derivative with unprecedented features, genuanine, was isolated from the venom of two cone snail species. Genuanine causes paralysis in mice, indicating that small molecules and not just polypeptides may contribute to the activity of cone snail venom.

  9. Autonomous regulation of growth cone filopodia.

    PubMed

    Rehder, V; Cheng, S

    1998-02-05

    The fan-shaped array of filopodia is the first site of contact of a neuronal growth cone with molecules encountered during neuronal pathfinding. Filopodia are highly dynamic structures, and the "action radius" of a growth cone is strongly determined by the length and number of its filopodia. Since interactions of filopodia with instructive cues in the vicinity of the growth cone can have effects on growth cone morphology within minutes, it has to be assumed that a large part of the signaling underlying such morphological changes resides locally within the growth cone proper. In this study, we tested the hypothesis that two important growth cone parameters-namely, the length and number of its filopodia-are regulated autonomously in the growth cone. We previously demonstrated in identified neurons from the snail Helisoma trivolvis that filopodial length and number are regulated by intracellular calcium. Here, we investigated filopodial dynamics and their regulation by the second-messenger calcium in growth cones which were physically isolated from their parent neuron by neurite transection. Our results show that isolated growth cones have longer but fewer filopodia than growth cones attached to their parent cell. These isolated growth cones, however, are fully capable of undergoing calcium-induced cytoskeletal changes, suggesting that the machinery necessary to perform changes in filopodial length and number is fully intrinsic to the growth cone proper.

  10. Cone positioning device for oral radiation therapy.

    PubMed

    Mahanna, G K; Ivanhoe, J R; Attanasio, R A

    1994-06-01

    This article describes the fabrication and modification of a peroral cone-positioning device. The modification provides added cone stability and prevents tongue intrusion into the radiation field. This device provides a repeatable accurate cone/lesion relationship and the fabrication technique is simplified, accurate, and minimizes patient discomfort.

  11. Cone selectivity derived from the responses of the retinal cone mosaic to natural scenes.

    PubMed

    Wachtler, Thomas; Doi, Eizaburo; Lee, Te- Won; Sejnowski, Terrence J

    2007-06-18

    To achieve color vision, the brain has to process signals of the cones in the retinal photoreceptor mosaic in a cone-type-specific way. We investigated the possibility that cone-type-specific wiring is an adaptation to the statistics of the cone signals. We analyzed estimates of cone responses to natural scenes and found that there is sufficient information in the higher order statistics of L- and M-cone responses to distinguish between cones of different types, enabling unsupervised learning of cone-type specificity. This was not the case for a fourth cone type with spectral sensitivity between L and M cones, suggesting an explanation for the lack of strong tetrachromacy in heterozygous carriers of color deficiencies.

  12. Cone selectivity derived from the responses of the retinal cone mosaic to natural scenes

    PubMed Central

    Doi, Eizaburo; Lee, Te-Won; Sejnowski, Terrence J.

    2010-01-01

    To achieve color vision, the brain has to process signals of the cones in the retinal photoreceptor mosaic in a cone-type-specific way. We investigated the possibility that cone-type-specific wiring is an adaptation to the statistics of the cone signals. We analyzed estimates of cone responses to natural scenes and found that there is sufficient information in the higher order statistics of L- and M-cone responses to distinguish between cones of different types, enabling unsupervised learning of cone-type specificity. This was not the case for a fourth cone type with spectral sensitivity between L and M cones, suggesting an explanation for the lack of strong tetrachromacy in heterozygous carriers of color deficiencies. PMID:17685813

  13. DOS cones along atomic chains

    NASA Astrophysics Data System (ADS)

    Kwapiński, Tomasz

    2017-03-01

    The electron transport properties of a linear atomic chain are studied theoretically within the tight-binding Hamiltonian and the Green’s function method. Variations of the local density of states (DOS) along the chain are investigated. They are crucial in scanning tunnelling experiments and give important insight into the electron transport mechanism and charge distribution inside chains. It is found that depending on the chain parity the local DOS at the Fermi level can form cone-like structures (DOS cones) along the chain. The general condition for the local DOS oscillations is obtained and the linear behaviour of the local density function is confirmed analytically. DOS cones are characterized by a linear decay towards the chain which is in contrast to the propagation properties of charge density waves, end states and Friedel oscillations in one-dimensional systems. We find that DOS cones can appear due to non-resonant electron transport, the spin–orbit scattering or for chains fabricated on a substrate with localized electrons. It is also shown that for imperfect chains (e.g. with a reduced coupling strength between two neighboring sites) a diamond-like structure of the local DOS along the chain appears.

  14. Achromatic vector vortex beams from a glass cone

    PubMed Central

    Radwell, N.; Hawley, R. D.; Götte, J. B.; Franke-Arnold, S.

    2016-01-01

    The reflection of light is governed by the laws first described by Augustin-Jean Fresnel: on internal reflection, light acquires a phase shift, which depends on its polarization direction with respect to the plane of incidence. For a conical reflector, the cylindrical symmetry is echoed in an angular variation of this phase shift, allowing us to create light modes with phase and polarization singularities. Here we observe the phase and polarization profiles of light that is back reflected from a solid glass cone and, in the case of circular input light, discover that not only does the beam contain orbital angular momentum but can trivially be converted to a radially polarized beam. Importantly, the Fresnel coefficients are reasonably stable across the visible spectrum, which we demonstrate by measuring white light polarization profiles. This discovery provides a highly cost-effective technique for the generation of broadband orbital angular momentum and radially polarized beams. PMID:26861191

  15. Experimental Modeling of a Formula Student Carbon Composite Nose Cone.

    PubMed

    Fellows, Neil A

    2017-06-06

    A numerical impact study is presented on a Formula Student (FS) racing car carbon composite nose cone. The effect of material model and model parameter selection on the numerical deceleration curves is discussed in light of the experimental deceleration data. The models show reasonable correlation in terms of the shape of the deceleration-displacement curves but do not match the peak deceleration values with errors greater that 30%.

  16. The phosphorylation state of neuronal processes determines growth cone formation after neuronal injury.

    PubMed

    Geddis, Matthew S; Rehder, Vincent

    2003-10-15

    Growth cones are essential for neuronal pathfinding during embryonic development and again after injury, when they aid in neuronal regeneration. This study was aimed at investigating the role of kinases in the earliest events in neuronal regeneration, namely, the formation of new growth cones from injured neuronal processes. Neurites of identified snail neurons grown in vitro were severed, and the formation of growth cones was observed from the ends of such transected processes. Under control conditions, all neurites formed a new growth cone within 45 min of transection. In contrast, growth cone formation in the presence of a general kinase inhibitor, K252a, was significantly inhibited. Moreover, decreasing the phosphorylation state of neurites by activating protein phosphatases with C2-ceramide also reduced growth cone formation. Pharmacological analysis with specific kinase inhibitors suggested that targets of protein kinase C (PKC) and tyrosine kinase (PTK) phosphorylation control growth cone formation. Inhibition of PKC with calphostin C and cerebroside completely blocked growth cone formation, whereas the inhibition of PTK with erbstatin analog significantly reduced growth cone formation. In contrast, inhibitors of protein kinase A, protein kinase G, CaM-kinase II, myosin light-chain kinase, Rho kinase, and PI-3 kinase had little or no effect 45 min after transection. These results suggest that the transformation underlying the formation of a growth cone from an injured (transected) neurite stump is highly sensitive to the phosphorylation state of key target proteins. Therefore, injury-induced signaling events will determine the outcome of neuronal regeneration through their action on kinase and phosphatase activities.

  17. Circadian-clock driven cone-like photoreceptor phagocytosis in the neural retina leucine zipper gene knockout mouse.

    PubMed

    Krigel, Arthur; Felder-Schmittbuhl, Marie-Paule; Hicks, David

    2010-12-28

    Whereas much information is available on rod outer segment phagocytosis by the retinal pigmented epithelium (RPE), corresponding data for cones are quite limited, especially in laboratory models of normal rats and mice with very low cone numbers. To characterize the light and circadian control of cone photoreceptor phagocytosis in mice, we capitalized on the blue cone-like phenotype of neural retina leucine zipper gene (Nrl) null mice (Nrl(-/-)). Nrl(-/-) mice were maintained under standard cyclic light (12h:12h light-dark [LD] cycle; light=300 lux) for one month, then divided into two groups: 1) continued maintenance in LD (36 mice); or 2) transferred to constant darkness (DD; 21 mice) for 36 h. Animals were sacrificed every 3 h over 24 h, and their eyes were rapidly enucleated and fixed. Cryosections were stained using specific cone short-wavelength opsin antibodies. Phagosome numbers in the RPE were quantified with a morphometric system. We monitored the expression of c-mer proto-oncogene tyrosine kinase (MerTK) in wild-type and knockout mice using a specific MerTK antibody. In LD, cone phagocytosis showed a statistically significant peak of activity 1 h after light onset, 2-3 fold higher than at other times. In constant darkness, the temporal phagocytic profile resembled that of LD (significant peak at 1 h of subjective day), but the number of phagosomes was decreased at all time points. Immunostaining of MerTK in wild-type and Nrl(-/-) mice showed expression at the apical surface of the RPE. Cone-like outer segment phagocytosis in Nrl(-/-) mice shows a similar profile to that of rods in normal mice and other species. These data are the first to quantify blue cone-like photoreceptor phagocytosis under different lighting conditions in mice, and suggest this model may constitute a valuable system for investigating circadian regulation of cone function.

  18. cis Retinol oxidation regulates photoreceptor access to the retina visual cycle and cone pigment regeneration.

    PubMed

    Sato, Shinya; Kefalov, Vladimir J

    2016-11-15

    This study explores the nature of the cis retinol that Müller cells in the retina provide to cones for the regeneration of their visual pigment. We report that the retina visual cycle provides cones exclusively with 11-cis chromophore in both salamander and mouse and show that this selectivity is dependent on the 11-cis-specific cellular retinaldehyde binding protein (CRALBP) present in Müller cells. Even though salamander blue cones and green rods share the same visual pigment, only blue cones but not green rods are able to dark-adapt in the retina following a bleach and to use exogenous 9-cis retinol for pigment regeneration, suggesting that access to the retina visual cycle is cone-specific and pigment-independent. Our results show that the retina produces 11-cis retinol that can be oxidized and used for pigment regeneration and dark adaptation selectively in cones and not in rods. Chromophore supply by the retinal Müller cells (retina visual cycle) supports the efficient pigment regeneration required for cone photoreceptor function in bright light. Surprisingly, a large fraction of the chromophore produced by dihydroceramide desaturase-1, the putative all-trans retinol isomerase in Müller cells, appears to be 9-cis retinol. In contrast, the canonical retinal pigment epithelium (RPE) visual cycle produces exclusively 11-cis retinal. Here, we used the different absorption spectra of 9-cis and 11-cis pigments to identify the isoform of the chromophore produced by the visual cycle of the intact retina. We found that the spectral sensitivity of salamander and mouse cones dark-adapted in the isolated retina (with only the retina visual cycle) was similar to that of cones dark-adapted in the intact eye (with both the RPE and retina visual cycles) and consistent with pure 11-cis pigment composition. However, in mice lacking the cellular retinaldehyde binding protein (CRALBP), cone spectral sensitivity contained a substantial 9-cis component. Thus, the retina visual

  19. Journey of water in pine cones

    NASA Astrophysics Data System (ADS)

    Song, Kahye; Yeom, Eunseop; Seo, Seung-Jun; Kim, Kiwoong; Kim, Hyejeong; Lim, Jae-Hong; Joon Lee, Sang

    2015-05-01

    Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system.

  20. Journey of water in pine cones

    PubMed Central

    Song, Kahye; Yeom, Eunseop; Seo, Seung-Jun; Kim, Kiwoong; Kim, Hyejeong; Lim, Jae-Hong; Joon Lee, Sang

    2015-01-01

    Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system. PMID:25944117

  1. Inside the cone of protection

    SciTech Connect

    Stahmann, J.R.

    1983-01-01

    Although lightning cones of protection and cones of attraction have been used for over 100 years, much confusion still remains as to their effectiveness, particularly as applied to personnel protection. At Kennedy Space Center, a 1:1 cone of protection with a straight side is standard for structure or equipment protection. However, at the launch pad, where a 400-foot lightning lightning rod on top of an insulating mast is used for pad lightning protection, the idea developed that personnel within a 400-foot radius of this mast would be safe from lightning and those outside it would not. Since it is obvious that a person 395 feet (120.4 m.) from the mast is only slightly safer than one at 405 feet (123.5 m.), an investigation was initiated to calculate the probabilities of a person being struck by lightning as he moves closer to the mast inside the cone of protection. Since the risk does not go to zero outside the structure, the risk level can then be estimated. To arrive at the expected strike frequency, it was necessary to measure the strike frequencies at KSC. Krider and others have found a mean area density of cloud-to-ground lightning at KSC of about 4.6 + or - 3.1 flashes per sq km per month in the summer. An overall frequency is estimated as about 20 flashes per sq km per year. With these data, the risk of exposure at various distances from the lightning mast can be calculated. Assuming continuous exposure during thunderstorms, this risk varies from about one strike per person in 1,400 years near the tower to one stroke per person in 300 years at about 400 foot (122 m.).

  2. Cardiac cone-beam CT

    SciTech Connect

    Manzke, Robert . E-mail: robert.manzke@philips.com

    2005-10-15

    This doctoral thesis addresses imaging of the heart with retrospectively gated helical cone-beam computed tomography (CT). A thorough review of the CT reconstruction literature is presented in combination with a historic overview of cardiac CT imaging and a brief introduction to other cardiac imaging modalities. The thesis includes a comprehensive chapter about the theory of CT reconstruction, familiarizing the reader with the problem of cone-beam reconstruction. The anatomic and dynamic properties of the heart are outlined and techniques to derive the gating information are reviewed. With the extended cardiac reconstruction (ECR) framework, a new approach is presented for the heart-rate-adaptive gated helical cardiac cone-beam CT reconstruction. Reconstruction assessment criteria such as the temporal resolution, the homogeneity in terms of the cardiac phase, and the smoothness at cycle-to-cycle transitions are developed. Several reconstruction optimization approaches are described: An approach for the heart-rate-adaptive optimization of the temporal resolution is presented. Streak artifacts at cycle-to-cycle transitions can be minimized by using an improved cardiac weighting scheme. The optimal quiescent cardiac phase for the reconstruction can be determined automatically with the motion map technique. Results for all optimization procedures applied to ECR are presented and discussed based on patient and phantom data. The ECR algorithm is analyzed for larger detector arrays of future cone-beam systems throughout an extensive simulation study based on a four-dimensional cardiac CT phantom. The results of the scientific work are summarized and an outlook proposing future directions is given. The presented thesis is available for public download at www.cardiac-ct.net.

  3. Missile and Spacecraft Coning Instabilities

    DTIC Science & Technology

    2007-11-02

    181-192. "Mingori, D. L., and Yam, T., " Nutational Stability of a Spinning Space- craft with Internal Mass Motion and Axial Thrust," AIAA Paper 86...Nomenclature 1 Introduction 1 Equations of Motion 2 Yaw Moment Damping or Undamping 2 Spacecraft Precession Damper 3 Vehicle Coning with Axial ...with Axial Thrust and Variable Mass The variable mass accompanying thrust from a spin-stabilized rocket motor or PAM produces a destabilizing effect

  4. Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years

    PubMed Central

    Mariotti, Letizia; Devaney, Nicholas; Lombardo, Giuseppe; Lombardo, Marco

    2016-01-01

    Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation. PMID:27446708

  5. Imaging Ca2+ dynamics in cone photoreceptor axon terminals of the mouse retina.

    PubMed

    Kulkarni, Manoj; Schubert, Timm; Baden, Tom; Wissinger, Bernd; Euler, Thomas; Paquet-Durand, Francois

    2015-05-06

    Retinal cone photoreceptors (cones) serve daylight vision and are the basis of color discrimination. They are subject to degeneration, often leading to blindness in many retinal diseases. Calcium (Ca(2+)), a key second messenger in photoreceptor signaling and metabolism, has been proposed to be indirectly linked with photoreceptor degeneration in various animal models. Systematically studying these aspects of cone physiology and pathophysiology has been hampered by the difficulties of electrically recording from these small cells, in particular in the mouse where the retina is dominated by rod photoreceptors. To circumvent this issue, we established a two-photon Ca(2+) imaging protocol using a transgenic mouse line that expresses the genetically encoded Ca(2+) biosensor TN-XL exclusively in cones and can be crossbred with mouse models for photoreceptor degeneration. The protocol described here involves preparing vertical sections ("slices") of retinas from mice and optical imaging of light stimulus-evoked changes in cone Ca(2+) level. The protocol also allows "in-slice measurement" of absolute Ca(2+) concentrations; as the recordings can be followed by calibration. This protocol enables studies into functional cone properties and is expected to contribute to the understanding of cone Ca(2+) signaling as well as the potential involvement of Ca(2+) in photoreceptor death and retinal degeneration.

  6. Loss of Bmi1 causes anomalies in retinal development and degeneration of cone photoreceptors.

    PubMed

    Barabino, Andrea; Plamondon, Vicky; Abdouh, Mohamed; Chatoo, Wassim; Flamier, Anthony; Hanna, Roy; Zhou, Shufeng; Motoyama, Noboru; Hébert, Marc; Lavoie, Joëlle; Bernier, Gilbert

    2016-05-01

    Retinal development occurs through the sequential but overlapping generation of six types of neuronal cells and one glial cell type. Of these, rod and cone photoreceptors represent the functional unit of light detection and phototransduction and are frequently affected in retinal degenerative diseases. During mouse development, the Polycomb group protein Bmi1 is expressed in immature retinal progenitors and differentiated retinal neurons, including cones. We show here that Bmi1 is required to prevent post natal degeneration of cone photoreceptors and bipolar neurons and that inactivation of Chk2 or p53 could improve but not overcome cone degeneration in Bmi1(-/-) mice. The retinal phenotype of Bmi1(-/-) mice was also characterized by loss of heterochromatin, activation of tandem repeats, oxidative stress and Rip3-associated necroptosis. In the human retina, BMI1 was preferentially expressed in cones at heterochromatic foci. BMI1 inactivation in human embryonic stem cells was compatible with retinal induction but impaired cone terminal differentiation. Despite this developmental arrest, BMI1-deficient cones recapitulated several anomalies observed in Bmi1(-/-) photoreceptors, such as loss of heterochromatin, activation of tandem repeats and induction of p53, revealing partly conserved biological functions between mouse and man. © 2016. Published by The Company of Biologists Ltd.

  7. Understanding the changes of cone reflectance in adaptive optics flood illumination retinal images over three years.

    PubMed

    Mariotti, Letizia; Devaney, Nicholas; Lombardo, Giuseppe; Lombardo, Marco

    2016-07-01

    Although there is increasing interest in the investigation of cone reflectance variability, little is understood about its characteristics over long time scales. Cone detection and its automation is now becoming a fundamental step in the assessment and monitoring of the health of the retina and in the understanding of the photoreceptor physiology. In this work we provide an insight into the cone reflectance variability over time scales ranging from minutes to three years on the same eye, and for large areas of the retina (≥ 2.0 × 2.0 degrees) at two different retinal eccentricities using a commercial adaptive optics (AO) flood illumination retinal camera. We observed that the difference in reflectance observed in the cones increases with the time separation between the data acquisitions and this may have a negative impact on algorithms attempting to track cones over time. In addition, we determined that displacements of the light source within 0.35 mm of the pupil center, which is the farthest location from the pupil center used by operators of the AO camera to acquire high-quality images of the cone mosaic in clinical studies, does not significantly affect the cone detection and density estimation.

  8. Cone pigments in a North American marsupial, the opossum (Didelphis virginiana).

    PubMed

    Jacobs, Gerald H; Williams, Gary A

    2010-05-01

    Only two of the four cone opsin gene families found in vertebrates are represented in contemporary eutherian and marsupial species. Recent genetic studies of two species of South American marsupial detected the presence of representatives from two of the classes of cone opsin genes and the structures of these genes predicted cone pigments with respective peaks in the ultraviolet and long-wavelength portions of the spectrum. The Virginia opossum (Didelphis virginiana), a profoundly nocturnal animal, is the only marsupial species found in North America. The prospects for cone-based vision in this species were examined through recordings of the electroretinogram (ERG), a commonly examined retinal response to photic stimulation. Recorded under flickering-light conditions that elicit signals from cone photoreceptors, the spectral sensitivity of the opossum eye is well accounted for by contributions from the presence of a single cone pigment having peak absorption at 561-562 nm. A series of additional experiments that employed various chromatic adaptation paradigms were conducted in a search for possible contributions from a second (short-wavelength sensitive) cone pigment. We found no evidence that such a mechanism contributes to the ERG in this marsupial.

  9. Bursting the Taylor cone bubble

    NASA Astrophysics Data System (ADS)

    Pan, Zhao; Truscott, Tadd

    2014-11-01

    A soap bubble fixed on a surface and placed in an electric field will take on the shape of a cone rather than constant curvature (dome) when the electrical field is not present. The phenomenon was introduced by J. Zeleny (1917) and studied extensively by C.T. Wilson & G.I. Taylor (1925). We revisit the Taylor cone problem by studying the deformation and bursting of soap bubbles in a point charge electric field. A single bubble takes on the shape of a cone in the electric field and a high-speed camera equipped with a micro-lens is used to observe the unsteady dynamics at the tip. Rupture occurs as a very small piece of the tip is torn away from the bubble toward the point charge. Based on experiments, a theoretical model is developed that predicts when rupture should occur. This study may help in the design of foam-removal techniques in engineering and provide a better understanding of an electrified air-liquid interface.

  10. The Na+/Ca2+, K+ exchanger NCKX4 is required for efficient cone-mediated vision

    PubMed Central

    Vinberg, Frans; Wang, Tian; De Maria, Alicia; Zhao, Haiqing; Bassnett, Steven; Chen, Jeannie; Kefalov, Vladimir J

    2017-01-01

    Calcium (Ca2+) plays an important role in the function and health of neurons. In vertebrate cone photoreceptors, Ca2+ controls photoresponse sensitivity, kinetics, and light adaptation. Despite the critical role of Ca2+ in supporting the function and survival of cones, the mechanism for its extrusion from cone outer segments is not well understood. Here, we show that the Na+/Ca2+, K+ exchanger NCKX4 is expressed in zebrafish, mouse, and primate cones. Functional analysis of NCKX4-deficient mouse cones revealed that this exchanger is essential for the wide operating range and high temporal resolution of cone-mediated vision. We show that NCKX4 shapes the cone photoresponse together with the cone-specific NCKX2: NCKX4 acts early to limit response amplitude, while NCKX2 acts late to further accelerate response recovery. The regulation of Ca2+ by NCKX4 in cones is a novel mechanism that supports their ability to function as daytime photoreceptors and promotes their survival. DOI: http://dx.doi.org/10.7554/eLife.24550.001 PMID:28650316

  11. The effects of collapsing factors on F-actin content and microtubule distribution of Helisoma growth cones.

    PubMed

    Torreano, Paul J; Waterman-Storer, Clare M; Cohan, Christopher S

    2005-03-01

    Growth cone collapsing factors induce growth cone collapse or repulsive growth cone turning by interacting with membrane receptors that induce alterations in the growth cone cytoskeleton. A common change induced by collapsing factors in the cytoskeleton of the peripheral domain, the thin lamellopodial area of growth cones, is a decline in the number of radially aligned F-actin bundles that form the core of filopodia. The present study examined whether ML-7, a myosin light chain kinase inhibitor, serotonin, a neurotransmitter and TPA, an activator of protein kinase C, which induce growth cone collapse of Helisoma growth cones, depolymerized or debundled F-actin. We report that these collapsing factors had different effects. ML-7 induced F-actin reorganization consistent with debundling whereas serotonin and TPA predominately depolymerized and possibly debundled F-actin. Additionally, these collapsing factors induced the formation of a dense actin-ring around the central domain, the thicker proximal area of growth cones [Zhou and Cohan, 2001: J. Cell Biol. 153:1071-1083]. The formation of the actin-ring occurred subsequent to the loss of actin bundles. The ML-7-induced actin-ring was found to inhibit microtubule extension into the P-domain. Thus, ML-7, serotonin, and TPA induce growth cone collapse associated with a decline in radially aligned F-actin bundles through at least two mechanisms involving debundling of actin filaments and/or actin depolymerization.

  12. Arrestin 1 and Cone Arrestin 4 Have Unique Roles in Visual Function in an All-Cone Mouse Retina.

    PubMed

    Deming, Janise D; Pak, Joseph S; Shin, Jung-A; Brown, Bruce M; Kim, Moon K; Aung, Moe H; Lee, Eun-Jin; Pardue, Machelle T; Craft, Cheryl Mae

    2015-12-01

    Previous studies discovered cone phototransduction shutoff occurs normally for Arr1-/- and Arr4-/-; however, it is defective when both visual arrestins are simultaneously not expressed (Arr1-/-Arr4-/-). We investigated the roles of visual arrestins in an all-cone retina (Nrl-/-) since each arrestin has differential effects on visual function, including ARR1 for normal light adaptation, and ARR4 for normal contrast sensitivity and visual acuity. We examined Nrl-/-, Nrl-/-Arr1-/-, Nrl-/-Arr4-/-, and Nrl-/-Arr1-/-Arr4-/- mice with photopic electroretinography (ERG) to assess light adaptation and retinal responses, immunoblot and immunohistochemical localization analysis to measure retinal expression levels of M- and S-opsin, and optokinetic tracking (OKT) to measure the visual acuity and contrast sensitivity. Study results indicated that Nrl-/- and Nrl-/-Arr4-/- mice light adapted normally, while Nrl-/-Arr1-/- and Nrl-/-Arr1-/-Arr4-/- mice did not. Photopic ERG a-wave, b-wave, and flicker amplitudes followed a general pattern in which Nrl-/-Arr4-/- amplitudes were higher than the amplitudes of Nrl-/-, while the amplitudes of Nrl-/-Arr1-/- and Nrl-/-Arr1-/-Arr4-/- were lower. All three visual arrestin knockouts had faster implicit times than Nrl-/- mice. M-opsin expression is lower when ARR1 is not expressed, while S-opsin expression is lower when ARR4 is not expressed. Although M-opsin expression is mislocalized throughout the photoreceptor cells, S-opsin is confined to the outer segments in all genotypes. Contrast sensitivity is decreased when ARR4 is not expressed, while visual acuity was normal except in Nrl-/-Arr1-/-Arr4-/-. Based on the opposite visual phenotypes in an all-cone retina in the Nrl-/-Arr1-/- and Nrl-/-Arr4-/- mice, we conclude that ARR1 and ARR4 perform unique modulatory roles in cone photoreceptors.

  13. How empty is an empty loss cone?

    NASA Astrophysics Data System (ADS)

    Weissbein, Amir; Sari, Re'em

    2017-06-01

    We consider two-body relaxation in a spherical system with a loss cone. Considering two-dimensional angular momentum space, we focus on 'empty loss cone' systems, where the typical scattering during a dynamical time jd is smaller than the size of the loss cone jlc. As a result, the occupation number within the loss cone is significantly smaller than outside. Classical diffusive treatment of this regime predict exponentially small occupation number deep in the loss cone. We revisit this classical derivation of occupancy distribution of objects in the empty loss cone regime. We emphasize the role of the rare large scatterings and show that the occupancy does not decay exponentially within the loss cone, but it is rather flat, with a typical value ˜[(jd/jlc)]2ln -2(jlc/jmin ) compared to the occupation in circular angular momentum (where jmin is the smallest possible scattering). Implication are that although the loss cone for tidal break of Giants or binaries is typically empty, tidal events that occur significantly inside the loss cone (β ≳ 2) are almost as common as those with β ≅ 1, where β is the ratio between the tidal radius and the periastron. The probability for event with penetration factor >β decreases only as β-1 rather than exponentially. This effect has no influence on events characterized by full loss cone, such as tidal disruption event of ˜1 m⊙ main-sequence star.

  14. Impact of oral melatonin on the electroretinogram cone response

    PubMed Central

    2009-01-01

    Background In the eye, melatonin plays a role in promoting light sensitivity at night and modulating many aspects of circadian retinal physiology. It is also an inhibitor of retinal dopamine, which is a promoter of day vision through the cone system. Consequently, it is possible that oral melatonin (an inhibitor of retinal dopamine) taken to alleviate circadian disorders may affect cone functioning. Our aim was to assess the impact of melatonin on the cone response of the human retina using electroretinography (ERG). Methods Twelve healthy participants aged between 18 to 52 years old were submitted to a placebo-controlled, double-blind, crossover, and counterbalanced-order design. The subjects were tested on 2 sessions beginning first with a baseline ERG, followed by the administration of the placebo or melatonin condition and then, 30 min later, a second ERG to test the effect. Results Following oral melatonin administration, a significant decrease of about 8% of the cone maximal response was observed (mean 6.9 μV ± SEM 2.0; P = 0.0065) along with a prolonged b-wave implicit time of 0.4 ms ± 0.1, 50 minutes after ingestion. Conclusion Oral melatonin appears to reach the eye through the circulation. When it is administered at a time of day when it is not usually present, melatonin appears to reduce input to retinal cones. We believe that the impact of melatonin on retinal function should be taken into consideration when used without supervision in chronic self-medication for sleep or circadian disorder treatment. PMID:19922677

  15. Impact of oral melatonin on the electroretinogram cone response.

    PubMed

    Gagné, Anne-Marie; Danilenko, Konstantin V; Rosolen, Serge G; Hébert, Marc

    2009-11-19

    In the eye, melatonin plays a role in promoting light sensitivity at night and modulating many aspects of circadian retinal physiology. It is also an inhibitor of retinal dopamine, which is a promoter of day vision through the cone system. Consequently, it is possible that oral melatonin (an inhibitor of retinal dopamine) taken to alleviate circadian disorders may affect cone functioning. Our aim was to assess the impact of melatonin on the cone response of the human retina using electroretinography (ERG). Twelve healthy participants aged between 18 to 52 years old were submitted to a placebo-controlled, double-blind, crossover, and counterbalanced-order design. The subjects were tested on 2 sessions beginning first with a baseline ERG, followed by the administration of the placebo or melatonin condition and then, 30 min later, a second ERG to test the effect. Following oral melatonin administration, a significant decrease of about 8% of the cone maximal response was observed (mean 6.9 muV +/- SEM 2.0; P = 0.0065) along with a prolonged b-wave implicit time of 0.4 ms +/- 0.1, 50 minutes after ingestion. Oral melatonin appears to reach the eye through the circulation. When it is administered at a time of day when it is not usually present, melatonin appears to reduce input to retinal cones. We believe that the impact of melatonin on retinal function should be taken into consideration when used without supervision in chronic self-medication for sleep or circadian disorder treatment.

  16. Relationship Between Foveal Cone Specialization and Pit Morphology in Albinism

    PubMed Central

    Wilk, Melissa A.; McAllister, John T.; Cooper, Robert F.; Dubis, Adam M.; Patitucci, Teresa N.; Summerfelt, Phyllis; Anderson, Jennifer L.; Stepien, Kimberly E.; Costakos, Deborah M.; Connor, Thomas B.; Wirostko, William J.; Chiang, Pei-Wen; Dubra, Alfredo; Curcio, Christine A.; Brilliant, Murray H.; Summers, C. Gail; Carroll, Joseph

    2014-01-01

    Purpose. Albinism is associated with disrupted foveal development, though intersubject variability is becoming appreciated. We sought to quantify this variability, and examine the relationship between foveal cone specialization and pit morphology in patients with a clinical diagnosis of albinism. Methods. We recruited 32 subjects with a clinical diagnosis of albinism. DNA was obtained from 25 subjects, and known albinism genes were analyzed for mutations. Relative inner and outer segment (IS and OS) lengthening (fovea-to-perifovea ratio) was determined from manually segmented spectral domain-optical coherence tomography (SD-OCT) B-scans. Foveal pit morphology was quantified for eight subjects from macular SD-OCT volumes. Ten subjects underwent imaging with adaptive optics scanning light ophthalmoscopy (AOSLO), and cone density was measured. Results. We found mutations in 22 of 25 subjects, including five novel mutations. All subjects lacked complete excavation of inner retinal layers at the fovea, though four subjects had foveal pits with normal diameter and/or volume. Peak cone density and OS lengthening were variable and overlapped with that observed in normal controls. A fifth hyper-reflective band was observed in the outer retina on SD-OCT in the majority of the subjects with albinism. Conclusions. Foveal cone specialization and pit morphology vary greatly in albinism. Normal cone packing was observed in the absence of a foveal pit, suggesting a pit is not required for packing to occur. The degree to which retinal anatomy correlates with genotype or visual function remains unclear, and future examination of larger patient groups will provide important insight on this issue. PMID:24845642

  17. Relationship between foveal cone specialization and pit morphology in albinism.

    PubMed

    Wilk, Melissa A; McAllister, John T; Cooper, Robert F; Dubis, Adam M; Patitucci, Teresa N; Summerfelt, Phyllis; Anderson, Jennifer L; Stepien, Kimberly E; Costakos, Deborah M; Connor, Thomas B; Wirostko, William J; Chiang, Pei-Wen; Dubra, Alfredo; Curcio, Christine A; Brilliant, Murray H; Summers, C Gail; Carroll, Joseph

    2014-05-20

    Albinism is associated with disrupted foveal development, though intersubject variability is becoming appreciated. We sought to quantify this variability, and examine the relationship between foveal cone specialization and pit morphology in patients with a clinical diagnosis of albinism. We recruited 32 subjects with a clinical diagnosis of albinism. DNA was obtained from 25 subjects, and known albinism genes were analyzed for mutations. Relative inner and outer segment (IS and OS) lengthening (fovea-to-perifovea ratio) was determined from manually segmented spectral domain-optical coherence tomography (SD-OCT) B-scans. Foveal pit morphology was quantified for eight subjects from macular SD-OCT volumes. Ten subjects underwent imaging with adaptive optics scanning light ophthalmoscopy (AOSLO), and cone density was measured. We found mutations in 22 of 25 subjects, including five novel mutations. All subjects lacked complete excavation of inner retinal layers at the fovea, though four subjects had foveal pits with normal diameter and/or volume. Peak cone density and OS lengthening were variable and overlapped with that observed in normal controls. A fifth hyper-reflective band was observed in the outer retina on SD-OCT in the majority of the subjects with albinism. Foveal cone specialization and pit morphology vary greatly in albinism. Normal cone packing was observed in the absence of a foveal pit, suggesting a pit is not required for packing to occur. The degree to which retinal anatomy correlates with genotype or visual function remains unclear, and future examination of larger patient groups will provide important insight on this issue. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  18. Calcium regulates vesicle replenishment at the cone ribbon synapse.

    PubMed

    Babai, Norbert; Bartoletti, Theodore M; Thoreson, Wallace B

    2010-11-24

    Cones release glutamate-filled vesicles continuously in darkness, and changing illumination modulates this release. Because sustained release in darkness is governed by vesicle replenishment rates, we analyzed how cone membrane potential regulates replenishment. Synaptic release from cones was measured by recording postsynaptic currents in Ambystoma tigrinum horizontal or OFF bipolar cells evoked by depolarization of simultaneously voltage-clamped cones. We measured replenishment after attaining a steady state between vesicle release and replenishment using trains of test pulses. Increasing Ca(2+) currents (I(Ca)) by changing the test step from -30 to -10 mV increased replenishment. Lengthening -30 mV test pulses to match the Ca(2+) influx during 25 ms test pulses to -10 mV produced similar replenishment rates. Reducing Ca(2+) driving force by using test steps to +30 mV slowed replenishment. Using UV flashes to reverse inhibition of I(Ca) by nifedipine accelerated replenishment. Increasing [Ca(2+)](i) by flash photolysis of caged Ca(2+) also accelerated replenishment. Replenishment, but not the initial burst of release, was enhanced by using an intracellular Ca(2+) buffer of 0.5 mm EGTA rather than 5 mm EGTA, and diminished by 1 mm BAPTA. This suggests that although release and replenishment exhibited similar Ca(2+) dependencies, release sites are <200 nm from Ca(2+) channels but replenishment sites are >200 nm away. Membrane potential thus regulates replenishment by controlling Ca(2+) influx, principally by effects on replenishment mechanisms but also by altering releasable pool size. This in turn provides a mechanism for converting changes in light intensity into changes in sustained release at the cone ribbon synapse.

  19. Dirac cones and Dirac saddle points of bright excitons in monolayer transition metal dichalcogenides.

    PubMed

    Yu, Hongyi; Liu, Gui-Bin; Gong, Pu; Xu, Xiaodong; Yao, Wang

    2014-05-12

    In monolayer transition metal dichalcogenides, tightly bound excitons have been discovered with a valley pseudospin optically addressable through polarization selection rules. Here, we show that this valley pseudospin is strongly coupled to the exciton centre-of-mass motion through electron-hole exchange. This coupling realizes a massless Dirac cone with chirality index I = 2 for excitons inside the light cone, that is, bright excitons. Under moderate strain, the I = 2 Dirac cone splits into two degenerate I = 1 Dirac cones, and saddle points with a linear Dirac spectrum emerge. After binding an extra electron, the charged exciton becomes a massive Dirac particle associated with a large valley Hall effect protected from intervalley scattering. Our results point to unique opportunities to study Dirac physics, with exciton's optical addressability at specifiable momentum, energy and pseudospin. The strain-tunable valley-orbit coupling also implies new structures of exciton condensates, new functionalities of excitonic circuits and mechanical control of valley pseudospin.

  20. A pioneering growth cone in the embryonic zebrafish brain.

    PubMed Central

    Wilson, S W; Easter, S S

    1991-01-01

    During development of the nervous system, growth cones navigate very precisely to their appropriate, often distant, targets. In insects, the task of establishing the earliest pathways is accomplished by a small number of neurons, termed pioneers. These neurons have axons that lay down an early scaffold, which provides a substrate for many later-developing axons. Here we show that a similar type of cell exists in the embryonic vertebrate brain. Using light- and electron-microscopic techniques we have examined the formation of one of the earliest tracts in the zebrafish brain. We find that it is pioneered at a precise time by the growth cone of a single neuron present in a predictable location. These observations show a fundamental similarity in the establishment of axonal pathways in the central nervous systems of both invertebrates and vertebrates. Images PMID:2006169

  1. Cone Penetrometer Off-Surface Sensor

    SciTech Connect

    Smail, T.R.; French, p.J.; Huffman, R.K.; Hebert, P.S.

    1999-10-20

    Cone penetrometer technology accounts for approximately 50 percent of the subsurface drilling done at the Savannah River Site. This technology provides a means of collecting data for use in the characterization of the subsurface. The cone penetrometer consists of a steel cone attached to a pipe column that is hydraulically inserted into the ground. To allow researchers to accurately measure subsurface properties, without the inherent problems of cone penetrometer equipment, the Savannah River Technology Center has developed the Cone Penetrometer Off-Surface Sensor (CPOSS). The CPOSS design consists of a knife-blade mechanism mounted along the surface of a module capable of attaching to existing cone penetrometer equipment and being deployed at depths of up to 200 feet. CPOSS development is the subject of this report.

  2. Programming Retinal Stem Cells into Cone Photoreceptors

    DTIC Science & Technology

    2015-12-01

    to program human stem cells directly into cones. Using RNA -seq, we identified several genes that are upregulated in advance of the earliest...reverse vision loss. 15. SUBJECT TERMS Cone photoreceptor, retina, retinal stem cell, Otx2, Onecut1, Blimp1, RNA -seq., transcription factors, and...1 Keywords: 1. Cone photoreceptor 2. Retina 3. Retinal stem cell 4. Otx2 5. Onecut1 6. Blimp1 7. RNA -seq. 8. Transcription factors 9

  3. In Vivo Imaging of Human Cone Photoreceptor Inner Segments

    PubMed Central

    Scoles, Drew; Sulai, Yusufu N.; Langlo, Christopher S.; Fishman, Gerald A.; Curcio, Christine A.; Carroll, Joseph; Dubra, Alfredo

    2014-01-01

    Purpose. An often overlooked prerequisite to cone photoreceptor gene therapy development is residual photoreceptor structure that can be rescued. While advances in adaptive optics (AO) retinal imaging have recently enabled direct visualization of individual cone and rod photoreceptors in the living human retina, these techniques largely detect strongly directionally-backscattered (waveguided) light from normal intact photoreceptors. This represents a major limitation in using existing AO imaging to quantify structure of remnant cones in degenerating retina. Methods. Photoreceptor inner segment structure was assessed with a novel AO scanning light ophthalmoscopy (AOSLO) differential phase technique, that we termed nonconfocal split-detector, in two healthy subjects and four subjects with achromatopsia. Ex vivo preparations of five healthy donor eyes were analyzed for comparison of inner segment diameter to that measured in vivo with split-detector AOSLO. Results. Nonconfocal split-detector AOSLO reveals the photoreceptor inner segment with or without the presence of a waveguiding outer segment. The diameter of inner segments measured in vivo is in good agreement with histology. A substantial number of foveal and parafoveal cone photoreceptors with apparently intact inner segments were identified in patients with the inherited disease achromatopsia. Conclusions. The application of nonconfocal split-detector to emerging human gene therapy trials will improve the potential of therapeutic success, by identifying patients with sufficient retained photoreceptor structure to benefit the most from intervention. Additionally, split-detector imaging may be useful for studies of other retinal degenerations such as AMD, retinitis pigmentosa, and choroideremia where the outer segment is lost before the remainder of the photoreceptor cell. PMID:24906859

  4. Rod and cone visual pigments and phototransduction through pharmacological, genetic, and physiological approaches.

    PubMed

    Kefalov, Vladimir J

    2012-01-13

    Activation of the visual pigment by light in rod and cone photoreceptors initiates our visual perception. As a result, the signaling properties of visual pigments, consisting of a protein, opsin, and a chromophore, 11-cis-retinal, play a key role in shaping the light responses of photoreceptors. The combination of pharmacological, physiological, and genetic tools has been a powerful approach advancing our understanding of the interactions between opsin and chromophore and how they affect the function of visual pigments. The signaling properties of the visual pigments modulate many aspects of the function of rods and cones, producing their unique physiological properties.

  5. Cone opsins, colour blindness and cone dystrophy: Genotype-phenotype correlations.

    PubMed

    Gardner, J C; Michaelides, M; Hardcastle, A J

    2016-05-25

    X-linked cone photoreceptor disorders caused by mutations in the OPN1LW (L) and OPN1MW (M) cone opsin genes on chromosome Xq28 include a range of conditions from mild stable red-green colour vision deficiencies to severe cone dystrophies causing progressive loss of vision and blindness. Advances in molecular genotyping and functional analyses of causative variants, combined with deep retinal phenotyping, are unravelling genetic mechanisms underlying the variability of cone opsin disorders.

  6. The 9-methyl group of retinal is essential for rapid Meta II decay and phototransduction quenching in red cones

    PubMed Central

    Kolesnikov, Alexander V.; Ala-Laurila, Petri; Crouch, Rosalie K.; Govardovskii, Victor I.; Cornwall, M. Carter

    2009-01-01

    Cone photoreceptors of the vertebrate retina terminate their response to light much faster than rod photoreceptors. However, the molecular mechanisms underlying this rapid response termination in cones are poorly understood. The experiments presented here tested two related hypotheses: first, that the rapid decay rate of metarhodopsin (Meta) II in red-sensitive cones depends on interactions between the 9-methyl group of retinal and the opsin part of the pigment molecule, and second, that rapid Meta II decay is critical for rapid recovery from saturation of red-sensitive cones after exposure to bright light. Microspectrophotometric measurements of pigment photolysis, microfluorometric measurements of retinol production, and single-cell electrophysiological recordings of flash responses of salamander cones were performed to test these hypotheses. In all cases, cones were bleached and their visual pigment was regenerated with either 11-cis retinal or with 11-cis 9-demethyl retinal, an analogue of retinal lacking the 9-methyl group. Meta II decay was four to five times slower and subsequent retinol production was three to four times slower in red-sensitive cones lacking the 9-methyl group of retinal. This was accompanied by a significant slowing of the recovery from saturation in cones lacking the 9-methyl group after exposure to bright (>0.1% visual pigment photoactivated) but not dim light. A mathematical model of the turn-off process of phototransduction revealed that the slower recovery of photoresponse can be explained by slower Meta decay of 9-demethyl visual pigment. These results demonstrate that the 9-methyl group of retinal is required for steric chromophore–opsin interactions that favor both the rapid decay of Meta II and the rapid response recovery after exposure to bright light in red-sensitive cones. PMID:19635855

  7. The 9-methyl group of retinal is essential for rapid Meta II decay and phototransduction quenching in red cones.

    PubMed

    Estevez, Maureen E; Kolesnikov, Alexander V; Ala-Laurila, Petri; Crouch, Rosalie K; Govardovskii, Victor I; Cornwall, M Carter

    2009-08-01

    Cone photoreceptors of the vertebrate retina terminate their response to light much faster than rod photoreceptors. However, the molecular mechanisms underlying this rapid response termination in cones are poorly understood. The experiments presented here tested two related hypotheses: first, that the rapid decay rate of metarhodopsin (Meta) II in red-sensitive cones depends on interactions between the 9-methyl group of retinal and the opsin part of the pigment molecule, and second, that rapid Meta II decay is critical for rapid recovery from saturation of red-sensitive cones after exposure to bright light. Microspectrophotometric measurements of pigment photolysis, microfluorometric measurements of retinol production, and single-cell electrophysiological recordings of flash responses of salamander cones were performed to test these hypotheses. In all cases, cones were bleached and their visual pigment was regenerated with either 11-cis retinal or with 11-cis 9-demethyl retinal, an analogue of retinal lacking the 9-methyl group. Meta II decay was four to five times slower and subsequent retinol production was three to four times slower in red-sensitive cones lacking the 9-methyl group of retinal. This was accompanied by a significant slowing of the recovery from saturation in cones lacking the 9-methyl group after exposure to bright (>0.1% visual pigment photoactivated) but not dim light. A mathematical model of the turn-off process of phototransduction revealed that the slower recovery of photoresponse can be explained by slower Meta decay of 9-demethyl visual pigment. These results demonstrate that the 9-methyl group of retinal is required for steric chromophore-opsin interactions that favor both the rapid decay of Meta II and the rapid response recovery after exposure to bright light in red-sensitive cones.

  8. Ionic emission from Taylor cones

    NASA Astrophysics Data System (ADS)

    Castro Reina, Sergio

    Electrified Taylor cones have been seen as an efficient way to generate thrust for space propulsion. Especially the pure ionic regime (PIR) combines a very high specific impulse (thrust per unit mass) and efficiency, which is very important to reduce fuel transportation costs. The PIR has been primarily based on electrosprays of liquid metals [Swatik and Hendricks 1968, Swatik 1969]. However, emissions dominated by or containing exclusively ions have also been observed from nonmetallic purely ionic substances, initially sulfuric acid [Perel et al. 1969], and more recently room temperature molten salts referred to as ionic liquids (ILs) [Romero-Sanz et al. 2003]. The recent use of the liquid metal ion source (LMIS) with ILs, becoming this "new" source to be known as ionic liquid ion source (ILIS) [Lozano and Martinez-Sanchez 2005], has shown important differences on the emission from Taylor cones with the traditional hollow capillary. This new source seems to be more flexible than the capillary [Paulo, Sergio, carlos], although its low emission level (low thrust) is an important drawback from the space propulsion point of view. Throughout the thesis I have studied some aspects of the ionic emission from ionic liquid Taylor cones and the influence of the properties of the liquids and the characteristic of source on the emission. I have unraveled the reason why ILIS emits such low currents (˜200 nA) and found a way to solve this problem increasing the current up to capillary levels (˜1000 nA) [Castro and Fernandez de la Mora 2009]. I have also tried to reduce ion evaporation while reducing the emitted droplet size in order to increase the thrust generated while keeping the efficiency relatively high and I have measured the energy of evaporation of several cations composing ionic liquids, mandatory step to understand ionic evaporation.

  9. A simple retinal mechanism contributes to perceptual interactions between rod- and cone-mediated responses in primates.

    PubMed

    Grimes, William N; Graves, Logan R; Summers, Mathew T; Rieke, Fred

    2015-06-22

    Visual perception across a broad range of light levels is shaped by interactions between rod- and cone-mediated signals. Because responses of retinal ganglion cells, the output cells of the retina, depend on signals from both rod and cone photoreceptors, interactions occurring in retinal circuits provide an opportunity to link the mechanistic operation of parallel pathways and perception. Here we show that rod- and cone-mediated responses interact nonlinearly to control the responses of primate retinal ganglion cells; these nonlinear interactions, surprisingly, were asymmetric, with rod responses strongly suppressing subsequent cone responses but not vice-versa. Human psychophysical experiments revealed a similar perceptual asymmetry. Nonlinear interactions in the retinal output cells were well-predicted by linear summation of kinetically-distinct rod- and cone-mediated signals followed by a synaptic nonlinearity. These experiments thus reveal how a simple mechanism controlling interactions between parallel pathways shapes circuit output and perception.

  10. An ADAM9 mutation in canine cone-rod dystrophy 3 establishes homology with human cone-rod dystrophy 9

    PubMed Central

    Goldstein, Orly; Mezey, Jason G.; Boyko, Adam R.; Gao, Chuan; Wang, Wei; Bustamante, Carlos D.; Anguish, Lynne J.; Jordan, Julie Ann; Pearce-Kelling, Susan E.; Aguirre, Gustavo D.

    2010-01-01

    Purpose To identify the causative mutation in a canine cone-rod dystrophy (crd3) that segregates as an adult onset disorder in the Glen of Imaal Terrier breed of dog. Methods Glen of Imaal Terriers were ascertained for crd3 phenotype by clinical ophthalmoscopic examination, and in selected cases by electroretinography. Blood samples from affected cases and non-affected controls were collected and used, after DNA extraction, to undertake a genome-wide association study using Affymetrix Version 2 Canine single nucleotide polymorphism chips and 250K Sty Assay protocol. Positional candidate gene analysis was undertaken for genes identified within the peak-association signal region. Retinal morphology of selected crd3-affected dogs was evaluated by light and electron microscopy. Results A peak association signal exceeding genome-wide significance was identified on canine chromosome 16. Evaluation of genes in this region suggested A Disintegrin And Metalloprotease domain, family member 9 (ADAM9), identified concurrently elsewhere as the cause of human cone-rod dystrophy 9 (CORD9), as a strong positional candidate for canine crd3. Sequence analysis identified a large genomic deletion (over 20 kb) that removed exons 15 and 16 from the ADAM9 transcript, introduced a premature stop, and would remove critical domains from the encoded protein. Light and electron microscopy established that, as in ADAM9 knockout mice, the primary lesion in crd3 appears to be a failure of the apical microvilli of the retinal pigment epithelium to appropriately invest photoreceptor outer segments. By electroretinography, retinal function appears normal in very young crd3-affected dogs, but by 15 months of age, cone dysfunction is present. Subsequently, both rod and cone function degenerate. Conclusions Identification of this ADAM9 deletion in crd3-affected dogs establishes this canine disease as orthologous to CORD9 in humans, and offers opportunities for further characterization of the disease

  11. Nested-cone transformer antenna

    DOEpatents

    Ekdahl, Carl A.

    1991-01-01

    A plurality of conical transmission lines are concentrically nested to form n output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated.

  12. Nested-cone transformer antenna

    DOEpatents

    Ekdahl, C.A.

    1991-05-28

    A plurality of conical transmission lines are concentrically nested to form an output antenna for pulsed-power, radio-frequency, and microwave sources. The diverging conical conductors enable a high power input density across a bulk dielectric to be reduced below a breakdown power density at the antenna interface with the transmitting medium. The plurality of cones maintain a spacing between conductors which minimizes the generation of high order modes between the conductors. Further, the power input feeds are isolated at the input while enabling the output electromagnetic waves to add at the transmission interface. Thus, very large power signals from a pulse rf, or microwave source can be radiated. 6 figures.

  13. Digoxin-induced reversible dysfunction of the cone photoreceptors in monkeys.

    PubMed

    Kinoshita, Junzo; Iwata, Noriaki; Kimotsuki, Tomofumi; Yasuda, Mitsuya

    2014-02-10

    To investigate functional alteration of the retina induced by digoxin in monkeys. Digoxin was intravenously administered to cynomolgus monkeys and standard full-field electroretinograms (ERGs) were serially recorded. In other digoxin-treated monkeys, the rod and cone a-waves to high-intensity flashes were obtained and analyzed by the a-wave fitting model (a-wave analysis). The following responses were also recorded: dark- and light-adapted responses to flashes of different intensities (dark- and light-adapted luminance responses), photopic ERG elicited by long-duration stimulus (ON-OFF response), and the photopic negative response (PhNR). Delayed b-wave was observed in all responses of the standard full-field ERGs; amplitude of the b-wave was increased in the rod response, but was decreased in the single-flash cone response and the 30-Hz flicker. These changes recovered gradually after elimination of digoxin from the blood. Digoxin enhanced and delayed the b-wave in the dark-adapted luminance-response analysis regardless of stimulus intensity. In the light-adapted luminance-response analysis, digoxin attenuated the a- and b-waves only at high and middle stimulus intensity, respectively. The a-wave analysis revealed selective decrease in the maximum response parameter (Rmax) in the cone a-wave. Both the b- and d-waves of the ON-OFF response were delayed. The selectively reduced Rmax in the cone a-wave indicated dysfunction of the cone photoreceptors in digoxin-treated monkeys. Meanwhile, the enhanced and delayed rod response suggested alteration of retinal components other than the cone photoreceptors. These results may contribute to the understanding of digoxin-induced visual disturbances in humans. It is suggested that the cone function is markedly, but not exclusively, affected in the retina of such patients.

  14. Rainbow Enhancers Regulate Restrictive Transcription in Teleost Green, Red, and Blue Cones.

    PubMed

    Fang, Wei; Guo, Chuanyu; Wei, Xiangyun

    2017-03-15

    Photoreceptor-specific transcription of individual genes collectively constitutes the transcriptional profile that orchestrates the structural and functional characteristics of each photoreceptor type. It is challenging, however, to study the transcriptional specificity of individual photoreceptor genes because each gene's distinct spatiotemporal transcription patterns are determined by the unique interactions between a specific set of transcription factors and the gene's own cis-regulatory elements (CREs), which remain unknown for most of the genes. For example, it is unknown what CREs underlie the zebrafish mpp5b(ponli) (ponli) and crumbs2b (crb2b) apical polarity genes' restrictive transcription in the red, green, and blue (RGB) cones in the retina, but not in other retinal cell types. Here we show that the intronic enhancers of both the ponli and crb2b genes are conserved among teleost species and that they share sequence motifs that are critical for RGB cone-specific transcription. Given their similarities in sequences and functions, we name the ponli and crb2b enhancers collectively rainbow enhancers. Rainbow enhancers may represent a cis-regulatory mechanism to turn on a group of genes that are commonly and restrictively expressed in RGB cones, which largely define the beginning of the color vision pathway.SIGNIFICANCE STATEMENT Dim-light achromatic vision and bright-light color vision are initiated in rod and several types of cone photoreceptors, respectively; these photoreceptors are structurally distinct from each other. In zebrafish, although quite different from rods and UV cones, RGB cones (red, green, and blue cones) are structurally similar and unite into mirror-symmetric pentamers (G-R-B-R-G) by adhesion. This structural commonality and unity suggest that a set of genes is commonly expressed only in RGB cones but not in other cells. Here, we report that the rainbow enhancers activate RGB cone-specific transcription of the ponli and crb2b genes. This

  15. Possible Tuff Cones In Isidis Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Seabrook, A. M.; Rothery, D. A.; Bridges, J. C.; Wright, I. P.

    The Beagle 2 lander of the ESA Mars Express mission will touch down on the martian surface in December 2003 to conduct a primarily exobiological mission. The landing site will be within Isidis Planitia, an 1100 km diameter impact basin. Isidis contains many sub-kilometre-sized cones. These can be found singly, in clusters, and in straight or arcuate chains extending many kilometres. In some areas of the basin these cones can occupy over 10% of the surface, with the most densely populated areas being in the older western half of the basin. There are few cones around the basin rim. There is also variation in the erosional state of the cones both across the basin, and within smaller areas, implying a range in time of formation for the cones. We currently favour a tuff cone origin as an explanation for these features. Tuff cones on Earth are rooted volcanic features formed at vents by the interaction between magma or magmatic heat and surface or near-surface water. Lava flows likely to be associated with at least some of the cones if they had a cinder cone (rooted eruptions at vents in a dry environment) origin are absent. This suggests the involvement of suffi- cient volatiles both to explosively fragment the erupting magma, and to cool the ejecta enough to prevent the formation of clastogenic flows. If our tuff cone interpretation is correct, this has implications for the presence, abundance and long-term persistence of sub-surface volatiles (water or carbon dioxide) on Mars. An understanding of the mechanism of formation of the Isidis cones will assist the characterisation of the basin in preparation for the landing of Beagle 2, by providing information about the history of volatiles and volcanism in the basin, and the processes that resulted in the surface we see today.

  16. Structural characterization of tick cement cones collected from in vivo and artificial membrane blood-fed Lone Star ticks (Amblyomma americanum).

    PubMed

    Bullard, Rebekah; Allen, Paige; Chao, Chien-Chung; Douglas, Jessica; Das, Pradipta; Morgan, Sarah E; Ching, Wei-Mei; Karim, Shahid

    2016-07-01

    The Lone Star tick, Amblyomma americanum, is endemic to the southeastern United States and capable of transmitting pathogenic diseases and causing non-pathogenic conditions. To remain firmly attached to the host, the tick secretes a proteinaceous matrix termed the cement cone which hardens around the tick's mouthparts to assist in the attachment of the tick as well as to protect the mouthparts from the host immune system. Cement cones collected from ticks on a host are commonly contaminated with host skin and hair making analysis of the cone difficult. To reduce the contamination found in the cement cone, we have adapted an artificial membrane feeding system used to feed long mouthpart ticks. Cones collected from in vivo and membrane fed ticks are analyzed to determine changes in the cone morphology. Comparisons of the cement cones using light microscopy shows similar structures and color however using scanning electron microscopy the cones have drastically different structures. The in vivo cones contain fibrils, sheets, and are heavily textured whereas cones from membrane fed ticks are remarkably smooth with no distinct structures. Analysis of the secondary protein structures using FTIR-ATR show both in vivo and membrane fed cement cones contain β sheets but only in vivo cement cones contain helical protein structures. Additionally, proteomic analysis using LC-MS/MS identifies many proteins including glycine rich proteins, metalloproteases, and protease inhibitors. Proteomic analysis of the cones identified both secreted and non-secreted tick proteins. Artificial membrane feeding is a suitable model for increased collection of cement cones for proteomic analysis however, structurally there are significant differences. Copyright © 2016 Elsevier GmbH. All rights reserved.

  17. Patterning the cone mosaic array in zebrafish retina requires specification of ultraviolet-sensitive cones.

    PubMed

    Raymond, Pamela A; Colvin, Steven M; Jabeen, Zahera; Nagashima, Mikiko; Barthel, Linda K; Hadidjojo, Jeremy; Popova, Lilia; Pejaver, Vivek R; Lubensky, David K

    2014-01-01

    Cone photoreceptors in teleost fish are organized in precise, crystalline arrays in the epithelial plane of the retina. In zebrafish, four distinct morphological/spectral cone types occupy specific, invariant positions within a regular lattice. The cone lattice is aligned orthogonal and parallel to circumference of the retinal hemisphere: it emerges as cones generated in a germinal zone at the retinal periphery are incorporated as single-cell columns into the cone lattice. Genetic disruption of the transcription factor Tbx2b eliminates most of the cone subtype maximally sensitive to ultraviolet (UV) wavelengths and also perturbs the long-range organization of the cone lattice. In the tbx2b mutant, the other three cone types (red, green, and blue cones) are specified in the correct proportion, differentiate normally, and acquire normal, planar polarized adhesive interactions mediated by Crumbs 2a and Crumbs 2b. Quantitative image analysis of cell adjacency revealed that the cones in the tbx2b mutant primarily have two nearest neighbors and align in single-cell-wide column fragments that are separated by rod photoreceptors. Some UV cones differentiate at the dorsal retinal margin in the tbx2b mutant, although they are severely dysmorphic and are eventually eliminated. Incorporating loss of UV cones during formation of cone columns at the margin into our previously published mathematical model of zebrafish cone mosaic formation (which uses bidirectional interactions between planar cell polarity proteins and anisotropic mechanical stresses in the plane of the retinal epithelium to generate regular columns of cones parallel to the margin) reproduces many features of the pattern disruptions seen in the tbx2b mutant.

  18. Patterning the Cone Mosaic Array in Zebrafish Retina Requires Specification of Ultraviolet-Sensitive Cones

    PubMed Central

    Raymond, Pamela A.; Colvin, Steven M.; Jabeen, Zahera; Nagashima, Mikiko; Barthel, Linda K.; Hadidjojo, Jeremy; Popova, Lilia; Pejaver, Vivek R.; Lubensky, David K.

    2014-01-01

    Cone photoreceptors in teleost fish are organized in precise, crystalline arrays in the epithelial plane of the retina. In zebrafish, four distinct morphological/spectral cone types occupy specific, invariant positions within a regular lattice. The cone lattice is aligned orthogonal and parallel to circumference of the retinal hemisphere: it emerges as cones generated in a germinal zone at the retinal periphery are incorporated as single-cell columns into the cone lattice. Genetic disruption of the transcription factor Tbx2b eliminates most of the cone subtype maximally sensitive to ultraviolet (UV) wavelengths and also perturbs the long-range organization of the cone lattice. In the tbx2b mutant, the other three cone types (red, green, and blue cones) are specified in the correct proportion, differentiate normally, and acquire normal, planar polarized adhesive interactions mediated by Crumbs 2a and Crumbs 2b. Quantitative image analysis of cell adjacency revealed that the cones in the tbx2b mutant primarily have two nearest neighbors and align in single-cell-wide column fragments that are separated by rod photoreceptors. Some UV cones differentiate at the dorsal retinal margin in the tbx2b mutant, although they are severely dysmorphic and are eventually eliminated. Incorporating loss of UV cones during formation of cone columns at the margin into our previously published mathematical model of zebrafish cone mosaic formation (which uses bidirectional interactions between planar cell polarity proteins and anisotropic mechanical stresses in the plane of the retinal epithelium to generate regular columns of cones parallel to the margin) reproduces many features of the pattern disruptions seen in the tbx2b mutant. PMID:24465536

  19. Cone Storage and Seed Quality in Longleaf Pine

    Treesearch

    F.T. Bonner

    1987-01-01

    Immature cones of longleaf pine (Pinus palustris Mill.) can be stored for at least 5 weeks without adversely affecting extraction or seed quality. Cone moisture should be below 50 percent before using heat to open cones.

  20. Optimization of cone target geometry for fast ignition

    SciTech Connect

    Nakamura, Tatsufumi; Sakagami, Hitoshi; Johzaki, Tomoyuki; Nagatomo, Hideo; Mima, Kunioki; Koga, James

    2007-10-15

    Electron energy characteristics generated by the irradiation of ultraintense laser pulses onto solid targets are controlled by using cone targets. Two parameters characterizing the laser-cone interaction are introduced, which are cone angle and the ratio of the laser spot size to the cone tip size. By changing these parameters, the energy absorption rate, laser irradiance at the cone tip, and electron acceleration at the cone tip and side wall are controlled. The optimum cone targets for fast ignition are 30 deg. cone angle with double-cone geometry, and a tip size comparable to the core size, with the irradiation of a laser pulse with a spot size of about four times the cone tip size. Cone targets have the possibility to enhance the maximum energy of laser-accelerated protons by using a smaller angle cone depending on the laser f-number.

  1. Stability of hypersonic compression cones

    NASA Astrophysics Data System (ADS)

    Reed, Helen; Kuehl, Joseph; Perez, Eduardo; Kocian, Travis; Oliviero, Nicholas

    2012-11-01

    Our activities focus on the identification and understanding of the second-mode instability for representative configurations in hypersonic flight. These include the Langley 93-10 flared cone and the Purdue compression cone, both at 0 degrees angle of attack at Mach 6. Through application of nonlinear parabolized stability equations (NPSE) and linear parabolized stability equations (PSE) to both geometries, it is concluded that mean-flow distortion tends to amplify frequencies less than the peak frequency and stabilize those greater by modifying the boundary-layer thickness. As initial disturbance amplitude is increased and/or a broad spectrum disturbance is introduced, direct numerical simulations (DNS) or NPSE appear to be the proper choices to model the evolution, and relative evolution, because these computational tools include these nonlinear effects (mean-flow distortion). Support from AFOSR/NASA National Center for Hypersonic Research in Laminar-Turbulent Transition through Grant FA9550-09-1-0341 is gratefully acknowledged. The authors also thank Pointwise, AeroSoft, and Texas Advanced Computing Center (TACC).

  2. Panoramic cone beam computed tomography

    SciTech Connect

    Chang Jenghwa; Zhou Lili; Wang Song; Clifford Chao, K. S.

    2012-05-15

    Purpose: Cone-beam computed tomography (CBCT) is the main imaging tool for image-guided radiotherapy but its functionality is limited by a small imaging volume and restricted image position (imaged at the central instead of the treatment position for peripheral lesions to avoid collisions). In this paper, the authors present the concept of ''panoramic CBCT,'' which can image patients at the treatment position with an imaging volume as large as practically needed. Methods: In this novel panoramic CBCT technique, the target is scanned sequentially from multiple view angles. For each view angle, a half scan (180 deg. + {theta}{sub cone} where {theta}{sub cone} is the cone angle) is performed with the imaging panel positioned in any location along the beam path. The panoramic projection images of all views for the same gantry angle are then stitched together with the direct image stitching method (i.e., according to the reported imaging position) and full-fan, half-scan CBCT reconstruction is performed using the stitched projection images. To validate this imaging technique, the authors simulated cone-beam projection images of the Mathematical Cardiac Torso (MCAT) thorax phantom for three panoramic views. Gaps, repeated/missing columns, and different exposure levels were introduced between adjacent views to simulate imperfect image stitching due to uncertainties in imaging position or output fluctuation. A modified simultaneous algebraic reconstruction technique (modified SART) was developed to reconstruct CBCT images directly from the stitched projection images. As a gold standard, full-fan, full-scan (360 deg. gantry rotation) CBCT reconstructions were also performed using projection images of one imaging panel large enough to encompass the target. Contrast-to-noise ratio (CNR) and geometric distortion were evaluated to quantify the quality of reconstructed images. Monte Carlo simulations were performed to evaluate the effect of scattering on the image quality and

  3. Cone calorimeter evaluation of wood products

    Treesearch

    Robert H. White; Mark A. Dietenberger

    2004-01-01

    The Forest Products Laboratory uses the cone calorimeter for the initial evaluation of the flammability of untreated and fire retardant treated wood products. The results of various studies are reviewed using a model presented at the 12th Annual BBC Conference on Flame Retardancy. The model uses data from the cone calorimeter to provide measures of fire growth...

  4. A Hydraulically Operated Pine Cone Cutter

    Treesearch

    Carl W. Fatzinger; M.T. Proveaux

    1971-01-01

    Mature cones of slash pine (Pinus elliottii Engelm. var. elliottii) and longleaf pine (P. palustris Mill.) can be easily bisected along their longitudinal axes with the hydraulic pine cone cutter described. This cutter eliminates the two major problems of earlier models--undue operator fatigue and the...

  5. System design description cone penetrometer system

    SciTech Connect

    Seda, R.Y., Westinghouse Hanford

    1996-08-12

    The system design description documents in detail the design of the cone penetrometer system. The systems includes the cone penetrometer physical package, raman spectroscopy package and moisture sensor package. Information pertinent to the system design, development, fabrication and testing is provided.

  6. Cone penetrometer demonstration standard startup review checklist

    SciTech Connect

    KRIEG, S.A.

    1998-11-09

    Startup readiness for the Cone Penetrometer Demonstration in AX Tank Farm will be verified through the application of a Standard Startup Review Checklist. This is a listing of those items essential to demonstrating readiness to start the Cone Penetrometer Demonstration in AX Tank Farm.

  7. Morphology of pyroclastic cones and tectonics

    NASA Astrophysics Data System (ADS)

    Tibaldi, Alessandro

    1995-12-01

    The relationships between morphology and spatial distribution of 1315 Quaternary pyroclastic cones and coeval faulting of the volcanic substrate are analyzed in the following regions with different structural settings: Tepic Rift (Mexico), Ethiopian Rift, Mexican Volcanic Belt, Canary Archipelago, and Mount Etna. Field data and analog experiments of tephra cone emplacement and collapse enable the definition of a number of parameters which can be used to infer the geometry of the fracture feeding the magma to a pyroclastic cone. The strike of the feeding plane is directly related to: (1) the elongation of cone base and crater, (2) the location of depressions on the crater rim, and (3) the alignment of pyroclastic cones in relation to a given vent spacing. In addition, the strike and dip of faults affect the direction of cone breaching. These relationships are valid for volcanic substrate topographic surfaces with an inclination of less than 9° and are especially sensitive to fault escarpment and cone height, lava and cone density, and fault orientation with respect to the dip of the volcanic substrate topography. Relations 1 and 2 become more pronounced for regions undergoing extensional tectonics, where edifices also have a larger dimension. Whereas breaching in the direction of the fault dip is more widespread in regions under extension, breaching along the fault strike as well as the coincidence between fault strike and vent alignment are more frequent in regions with transcurrent or transtensional tectonics.

  8. Cone calorimeter tests of wood composites

    Treesearch

    Robert H. White; Kuma Sumathipala

    2013-01-01

    The cone calorimeter is widely used for the determination of the heat release rate (HRR) of building products and other materials. As part of an effort to increase the availability of cone calorimeter data on wood products, the U.S. Forest Products Laboratory and the American Wood Council conducted this study on composite wood products in cooperation with the Composite...

  9. Targeting gene expression to cones with human cone opsin promoters in recombinant AAV.

    PubMed

    Komáromy, A M; Alexander, J J; Cooper, A E; Chiodo, V A; Glushakova, L G; Acland, G M; Hauswirth, W W; Aguirre, G D

    2008-07-01

    Specific cone-directed therapy is of high priority in the treatment of human hereditary retinal diseases. However, not much information exists about the specific targeting of photoreceptor subclasses. Three versions of the human red cone opsin promoter (PR0.5, 3LCR-PR0.5 and PR2.1), and the human blue cone opsin promoter HB569, were evaluated for their specificity and robustness in targeting green fluorescent protein (GFP) gene expression to subclasses of cones in the canine retina when used in recombinant adeno-associated viral vectors of serotype 5. The vectors were administered by subretinal injection. The promoter PR2.1 led to most effective and specific expression of GFP in the long- and medium-wavelength-absorbing cones (L/M cones) of normal and diseased retinas. The PR0.5 promoter was not effective. Adding three copies of the 35-bp LCR in front of PR0.5 lead to weak GFP expression in L/M cones. The HB569 promoter was not specific, and GFP was expressed in a few L/M cones, some rods and the retinal pigment epithelium. These results suggest that L/M cones, the predominant class of cone photoreceptors in the retinas of dogs and most mammalian species can be successfully targeted using the human red cone opsin promoter.

  10. Camera Layout Design for the Upper Stage Thrust Cone

    NASA Technical Reports Server (NTRS)

    Wooten, Tevin; Fowler, Bart

    2010-01-01

    Engineers in the Integrated Design and Analysis Division (EV30) use a variety of different tools to aid in the design and analysis of the Ares I vehicle. One primary tool in use is Pro-Engineer. Pro-Engineer is a computer-aided design (CAD) software that allows designers to create computer generated structural models of vehicle structures. For the Upper State thrust cone, Pro-Engineer was used to assist in the design of a layout for two camera housings. These cameras observe the separation between the first and second stage of the Ares I vehicle. For the Ares I-X, one standard speed camera was used. The Ares I design calls for two separate housings, three cameras, and a lighting system. With previous design concepts and verification strategies in mind, a new layout for the two camera design concept was developed with members of the EV32 team. With the new design, Pro-Engineer was used to draw the layout to observe how the two camera housings fit with the thrust cone assembly. Future analysis of the camera housing design will verify the stability and clearance of the camera with other hardware present on the thrust cone.

  11. Unique characteristics of cones in Central Elysium Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Noguchi, Rina; Kurita, Kei

    2015-06-01

    Martian magmatism within recent several hundreds of millions years is still controversial. Central Elysium Planitia (CEP) is suspected as a site of the latest magmatism on Mars, but hot debates have been caused as for the origin of this flat plain. Cones in CEP are expected to be a key to resolve this controversy. In previous works, there are 2 models proposed for the origin of CEP cones: volcanic rootless cone (e.g. Jaeger et al., 2007) and periglacial pingo (e.g. Burr et al., 2002; Page et al., 2009). In this study, we described detail morphology, distribution and size of CEP cones by using high-resolution images and topographic data. CEP cones are classified into 3 morphological types: Single Cone (SC), Double Cone (DC), and Lotus Fruit Cone (LC). DC has an inner cone in the summit crater of the outer cone, and LC has several inner cones in the summit crater of the outer cone. Several cones have moat structure around the edifice with peripheral rise. DCs and LCs are located in very flat areas of Athabasca Valles in the vicinity of Cerberus Fossae, while SCs distribute in the entire region of CEP. We compared CEP cones with terrestrial rootless cones and pingos in aerial photos. In Lake Myvatn, Iceland, there exist rootless cones which resemble DCs and LCs in CEP. Based on the similarities with terrestrial analogies, we concluded that the most feasible origin of CEP cones is rootless cones.

  12. Mechanochemical regulation of growth cone motility

    PubMed Central

    Kerstein, Patrick C.; Nichol, Robert H.; Gomez, Timothy M.

    2015-01-01

    Neuronal growth cones are exquisite sensory-motor machines capable of transducing features contacted in their local extracellular environment into guided process extension during development. Extensive research has shown that chemical ligands activate cell surface receptors on growth cones leading to intracellular signals that direct cytoskeletal changes. However, the environment also provides mechanical support for growth cone adhesion and traction forces that stabilize leading edge protrusions. Interestingly, recent work suggests that both the mechanical properties of the environment and mechanical forces generated within growth cones influence axon guidance. In this review we discuss novel molecular mechanisms involved in growth cone force production and detection, and speculate how these processes may be necessary for the development of proper neuronal morphogenesis. PMID:26217175

  13. Diminished foraging performance of a mutant zebrafish with reduced population of ultraviolet cones

    PubMed Central

    Novales Flamarique, Iñigo

    2016-01-01

    Ultraviolet (UV) cones are photoreceptors that sense light in the range 300–450 nm and are found in the retinas of non-mammalian vertebrates and small mammals. Despite their widespread presence across taxa, the functions that these cones exert in the lives of animals remain largely unknown. In this study, I used the zebrafish lor (lots of rods) mutant, characterized by a diminished UV cone population compared to that of wild-type zebrafish, to test whether its foraging performance differed from that of the wild-type (control). The mean location distance and angle (variables that are reliable indicators of foraging performance) at which control fish detected zooplankton prey were, on average, 24 and 90% greater than corresponding measures for lor fish. Such inferior foraging performance of the mutant could be explained by reduced contrast perception of the prey, resulting from the diminished population of UV cones and associated sensitivity. Thus, UV cones enhance the foraging performance of zebrafish, a crucial ecological function that may explain why small zooplanktivorous fishes retain UV cones throughout their lives. PMID:26936243

  14. Linking impulse response functions to reaction time: Rod and cone reaction time data and a computational model

    PubMed Central

    Cao, Dingcai; Zele, Andrew J.; Pokorny, Joel

    2007-01-01

    Reaction times for incremental and decremental stimuli were measured at five suprathreshold contrasts for six retinal illuminance levels where rods alone (0.002–0.2 Trolands), rods and cones (2–20 Trolands) or cones alone (200 Trolands) mediated detection. A 4-primary photostimulator allowed independent control of rod or cone excitations. This is the first report of reaction times to isolated rod or cone stimuli at mesopic light levels under the same adaptation conditions. The main findings are: 1) For rods, responses to decrements were faster than increments, but cone reaction times were closely similar. 2) At light levels where both systems were functional, rod reaction times were ~20 ms longer. The data were fitted with a computational model that incorporates rod and cone impulse response functions and a stimulus-dependent neural sensory component that triggers a motor response. Rod and cone impulse response functions were derived from published psychophysical two-pulse threshold data and temporal modulation transfer functions. The model fits were accomplished with a limited number of free parameters: two global parameters to estimate the irreducible minimum reaction time for each receptor type, and one local parameter for each reaction time versus contrast function. This is the first model to provide a neural basis for the variation in reaction time with retinal illuminance, stimulus contrast, stimulus polarity, and receptor class modulated. PMID:17346763

  15. LSP Calculations of Cone-Wire Experiments

    SciTech Connect

    Town, R J; Cottrill, L A; Key, M H; Kruer, W L; Langdon, A B; Lasinski, B F; McCandless, B C; Myatt, J F; Park, H S; Remington, B A; Snavely, R A; Still, C H; Tabak, M; Welch, D R; Wilks, S C

    2005-06-13

    Recent experiments at the Institute of Laser Engineering (ILE) in Japan [1] and at Rutherford Appleton Laboratory (RAL) in the United Kingdom [2] have shown good coupling of short-pulse high-intensity laser light into high-energy electrons channeled down a narrow fiber. Such target configurations are being considered as backlighter targets on the National Ignition Facility (NIF). We will report on LSP calculations of these cone-wire experiments and other candidate target configurations. These calculations also give insight into the transport of MeV-electrons, which remains the critical issue for the achievement of fast ignition [3]. The LSP code uses a direct implicit particle-in-cell (PIC) algorithm in 2 or 3 dimensions to solve for beam particle transport, while treating the background particles as a fluid [4]. We have modified LSP to produce K{alpha} photons in a non-interfering manner and will show calculated absolute K{alpha} yields for the experiments reported by Key [2].

  16. Spectral tuning of rhodopsin and visual cone pigments.

    PubMed

    Zhou, Xiuwen; Sundholm, Dage; Wesołowski, Tomasz A; Kaila, Ville R I

    2014-02-19

    Retinal is the light-absorbing biochromophore responsible for the activation of vision pigments and light-driven ion pumps. Nature has evolved molecular tuning mechanisms that significantly shift the optical properties of the retinal pigments to enable their absorption of visible light. Using large-scale quantum chemical calculations at the density functional theory level combined with frozen density embedding theory, we show here how the protein environment of vision pigments tunes the absorption of retinal by electrostatically dominated interactions between the chromophore and the surrounding protein residues. The calculations accurately reproduce the experimental absorption maxima of rhodopsin and the red, green, and blue color pigments. We further identify key interactions responsible for the color-shifting effects by mutating the rhodopsin structure in silico, and we find that deprotonation of the retinyl is likely to be responsible for the blue-shifted absorption in the blue cone vision pigment.

  17. Cone penetrometer fiber optic raman spectroscopy probe assembly

    DOEpatents

    Kyle, Kevin R.; Brown, Steven B.

    2000-01-01

    A chemically and mechanically robust optical Raman spectroscopy probe assembly that can be incorporated in a cone penetrometer (CPT) for subsurface deployment. This assembly consists of an optical Raman probe and a penetrometer compatible optical probe housing. The probe is intended for in-situ chemical analysis of chemical constituents in the surrounding environment. The probe is optically linked via fiber optics to the light source and the detection system at the surface. A built-in broadband light source provides a strobe method for direct measurement of sample optical density. A mechanically stable sapphire window is sealed directly into the side-wall of the housing using a metallic, chemically resistant, hermetic seal design. This window permits transmission of the interrogation light beam and the resultant signal. The spectroscopy probe assembly is capable of accepting Raman, Laser induced Fluorescence, reflectance, and other optical probes with collimated output for CPT deployment.

  18. Rod sensitivity, cone sensitivity, and photoreceptor layer thickness in retinal degenerative diseases.

    PubMed

    Birch, David G; Wen, Yuquan; Locke, Kelly; Hood, Donald C

    2011-09-09

    To evaluate the effects of selective rod and/or cone loss on frequency-domain optical coherence tomography (fdOCT) measures of photoreceptor structure in patients with retinal degenerative diseases. Six patients with cone dystrophy (CD) and eight patients with retinitis pigmentosa (RP) were recruited from the Southwest Eye Registry on the basis of diagnosis and ERG findings. fdOCT horizontal line scans were segmented to obtain the thicknesses of the outer segments plus RPE (OS+) and the outer nuclear layer (ONL). The normalized product ONL*OS was obtained after dividing by mean ONL*OS values of 23 normal individuals. Visual field sensitivity profiles were obtained with a modified retinal perimeter, from the horizontal midline with short- and long-wave stimuli under dark- and light-adapted conditions. Patients with CD and normal rod-mediated sensitivity, but decreased cone-mediated sensitivity, showed normal ONL*OS outside the fovea. The total receptor layer was thinned in the fovea, consistent with loss in cone nuclei and Henle's fiber layer. Patients with RP and sensitivity in the dark that was mediated by cones showed ONL*OS thickness that was linearly related to cone sensitivity. ONL*OS thickness was linearly related to rod sensitivity in regions with greater loss of cone than rod sensitivity. Both rods and cones can support an intact IS/OS junction and normal photoreceptor thickness measures. The product of ONL and OS thicknesses is proportional to the sensitivity mediated by the less abnormal type of photoreceptor.

  19. Complex binding pathways determine the regeneration of mammalian green cone opsin with a locked retinal analogue.

    PubMed

    Alexander, Nathan S; Katayama, Kota; Sun, Wenyu; Salom, David; Gulati, Sahil; Zhang, Jianye; Mogi, Muneto; Palczewski, Krzysztof; Jastrzebska, Beata

    2017-06-30

    Phototransduction is initiated when the absorption of light converts the 11-cis-retinal chromophore to its all-trans configuration in both rod and cone vertebrate photoreceptors. To sustain vision, 11-cis-retinal is continuously regenerated from its all-trans conformation through a series of enzymatic steps comprising the "visual or retinoid" cycle. Abnormalities in this cycle can compromise vision because of the diminished supply of 11-cis-retinal and the accumulation of toxic, constitutively active opsin. As shown previously for rod cells, attenuation of constitutively active opsin can be achieved with the unbleachable analogue, 11-cis-6-membered ring (11-cis-6mr)-retinal, which has therapeutic effects against certain degenerative retinal diseases. However, to discern the molecular mechanisms responsible for this action, pigment regeneration with this locked retinal analogue requires delineation also in cone cells. Here, we compared the regenerative properties of rod and green cone opsins with 11-cis-6mr-retinal and demonstrated that this retinal analogue could regenerate rod pigment but not green cone pigment. Based on structural modeling suggesting that Pro-205 in green cone opsin could prevent entry and binding of 11-cis-6mr-retinal, we initially mutated this residue to Ile, the corresponding residue in rhodopsin. However, this substitution did not enable green cone opsin to regenerate with 11-cis-6mr-retinal. Interestingly, deletion of 16 N-terminal amino acids in green cone opsin partially restored the binding of 11-cis-6mr-retinal. These results and our structural modeling indicate that a more complex binding pathway determines the regeneration of mammalian green cone opsin with chromophore analogues such as 11-cis-6mr-retinal. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  20. Extrafoveal Cone Packing in Eyes With a History of Retinopathy of Prematurity

    PubMed Central

    Ramamirtham, Ramkumar; Akula, James D.; Soni, Garima; Swanson, Matthew J.; Bush, Jennifer N.; Moskowitz, Anne; Swanson, Emily A.; Favazza, Tara L.; Tavormina, Jena L.; Mujat, Mircea; Ferguson, R. Daniel; Hansen, Ronald M.; Fulton, Anne B.

    2016-01-01

    Purpose To study the density and packing geometry of the extrafoveal cone photoreceptors in eyes with a history of retinopathy of prematurity (ROP). We used a multimodal combination of adaptive optics (AO) scanning light ophthalmoscopy (SLO) and optical coherence tomography (OCT). Methods Cones were identified in subjects (aged 14–26 years) with a history of ROP that was either severe and treated by laser ablation of avascular peripheral retina (TROP; n = 5) or mild and spontaneously resolved, untreated (UROP; n = 5), and in term-born controls (CT; n = 8). The AO-SLO images were obtained at temporal eccentricities 4.5°, 9°, 13.5°, and 18° using both confocal and offset apertures with simultaneous, colocal OCT images. Effects of group, eccentricity, and aperture were evaluated and the modalities compared. Results In the SLO images, cone density was lower and the packing pattern less regular in TROP, relative to CT and UROP retinae. Although SLO image quality appeared lower in TROP, root mean square (RMS) wavefront error did not differ among the groups. In TROP eyes, cone discrimination was easier in offset aperture images. There was no evidence of cone loss in the TROP OCT images. Conclusions Low cone density in TROP confocal SLO images may have resulted from lower image quality. Since AO correction in these eyes was equivalent to that of the control group, and OCT imaging showed no significant cone loss, the optical properties of the inner retina or properties of the cones themselves are likely altered in a way that affects photoreceptor imaging. PMID:26868749

  1. Multiple rod-cone and cone-rod photoreceptor transmutations in snakes: evidence from visual opsin gene expression.

    PubMed

    Simões, Bruno F; Sampaio, Filipa L; Loew, Ellis R; Sanders, Kate L; Fisher, Robert N; Hart, Nathan S; Hunt, David M; Partridge, Julian C; Gower, David J

    2016-01-27

    In 1934, Gordon Walls forwarded his radical theory of retinal photoreceptor 'transmutation'. This proposed that rods and cones used for scotopic and photopic vision, respectively, were not fixed but could evolve into each other via a series of morphologically distinguishable intermediates. Walls' prime evidence came from series of diurnal and nocturnal geckos and snakes that appeared to have pure-cone or pure-rod retinas (in forms that Walls believed evolved from ancestors with the reverse complement) or which possessed intermediate photoreceptor cells. Walls was limited in testing his theory because the precise identity of visual pigments present in photoreceptors was then unknown. Subsequent molecular research has hitherto neglected this topic but presents new opportunities. We identify three visual opsin genes, rh1, sws1 and lws, in retinal mRNA of an ecologically and taxonomically diverse sample of snakes central to Walls' theory. We conclude that photoreceptors with superficially rod- or cone-like morphology are not limited to containing scotopic or photopic opsins, respectively. Walls' theory is essentially correct, and more research is needed to identify the patterns, processes and functional implications of transmutation. Future research will help to clarify the fundamental properties and physiology of photoreceptors adapted to function in different light levels. © 2016 The Author(s).

  2. [Recovery of rod and cone systems after retinal detachment surgery].

    PubMed

    Alexandridis, E

    1979-01-01

    The paper reports on the threshold values for light perception of circumscript retinal areas for different adaptation levels in patients successfully operated for retinal detachment. The examinations were carried out by means of the Tübingen projection perimeter, using the method of static perimetry in a meridian containing an approximately equal area of healthy and of formerly detached retina. The main aim of this examination was to establish whether both retinal photoreceptor systems recover within the same time after the operation. There is various evidence that the restitutions of the rod and cone systems do not occur at the same time.

  3. Chromatic Properties of Horizontal and Ganglion Cell Responses Follow a Dual Gradient in Cone Opsin Expression

    PubMed Central

    Yin, Lu; Smith, Robert G; Sterling, Peter; Brainard, David H.

    2007-01-01

    In guinea pig retina, immunostaining reveals a dual gradient of opsins: cones expressing opsin sensitive to medium wavelengths (M) predominate in the upper retina, whereas cones expressing opsin sensitive to shorter wavelengths (S) predominate in the lower retina. Whether these gradients correspond to functional gradients in postreceptoral neurons is essentially unknown. Using monochromatic flashes, we measured the relative weights with which M, S, and rod signals contribute to horizontal cell responses. For a background that produced 4.76 log10 photoisomerizations per rod per second (Rh*/rod/s), mean weights in superior retina were 52% (M), 2% (S), and 46% (rod). Mean weights in inferior retina were 9% (M), 50% (S), and 41% (rod). In superior retina, cone opsin weights agreed quantitatively with relative pigment density estimates from immunostaining. In inferior retina, cone opsin weights agreed qualitatively with relative pigment density estimates, but quantitative comparison was impossible because individual cones coexpress both opsins to varying and unquantifiable degrees. We further characterized the functional gradients in horizontal and brisk-transient ganglion cells using flickering stimuli produced by various mixtures of blue and green primary lights. Cone weights for both cell types resembled those obtained for horizontal cells using monochromatic flashes. Because the brisk-transient ganglion cell is thought to mediate behavioral detection of luminance contrast, our results are consistent with the hypothesis that the dual gradient of cone opsins assists achromatic contrast detection against different spectral backgrounds. In our preparation, rod responses did not completely saturate, even at background light levels typical of outdoor sunlight (5.14 log10 Rh*/rod/s). PMID:17122060

  4. Photocurrents of cone photoreceptors of the golden-mantled ground squirrel.

    PubMed

    Kraft, T W

    1988-10-01

    1. Visual transduction in photoreceptors of the ground squirrel, Citellus lateralis, was studied by recording membrane current from individual cones in small pieces of retina. 2. Brief flashes of light produced transient reductions of the dark current; saturating response amplitudes were up to 67 pA. A flash strength of about 11,000 photons microns-2 at lambda max was required to give a half-saturating response. The stimulus-response relation was well fitted by an exponential saturation curve. Responses below 20% of maximum behaved linearly. 3. The response to a dim flash in most cells had a time to peak of 20-30 ms and resembled the impulse response of a series of five low-pass filters. 4. The variance of the dim-flash response amplitude put an upper limit of 80 fA on the size of the single photon response. Estimates based on the effective collecting area suggest the single photon response to be of the order of 10 fA. 5. Flash responses of squirrel cones usually lacked the undershoot observed in primate cones, although in about 1/3 of the cells a small undershoot developed during recording. 6. Background lights slightly shortened the time to peak of the flash response and reduced the integration time. 7. Spectral sensitivity measurements showed two classes of cones with peak sensitivities at about 520 and 435 nm. Rod sensitivity peaked near 500 nm. Spectral univariance was obeyed by all three classes of cells. 8. The shapes of the spectral sensitivity curves of the rod and both types of cones were similar to each other when plotted on a log wave number scale, but differed significantly from similar plots of monkey and human cone spectra. 9. The kinetics and sensitivity of flash responses of the blue- and green-sensitive cones were indistinguishable.

  5. Cone Photoreceptors in Bass Retina Use Two Connexins to Mediate Electrical Coupling

    PubMed Central

    O’Brien, John; Bao Nguyen, H.; Mills, Stephen L.

    2008-01-01

    Electrical coupling via gap junctions is a common property of CNS neurons. In retinal photoreceptors, coupling plays important roles in noise filtering, intensity coding, and spatial processing. In many vertebrates, coupling is regulated during the course of light adaptation. To understand the mechanisms of this regulation, we studied photoreceptor gap junction proteins. We found that two connexins were expressed in bass cone photoreceptors. Connexin35 (Cx35) mRNA was present in many cell types including photoreceptors, amacrine, bipolar, and a few ganglion cells. Antibodies to Cx35 labeled abundant gap junctions in both the inner and outer plexiform layers. In the outer plexiform layer, numerous plaques co-localized with cone telodendria at crossing contacts and tip-to-tip contacts. Cx34.7 mRNA was found predominantly in the photoreceptor layer, primarily in cones. Cx34.7 immunolabeling was limited to small plaques immediately beneath cone pedicles, and did not co-localize with Cx35. Cx34.7 plaques were associated with a dense complex of cone membrane beneath the pedicles, including apparent contacts between telodendria and cone pedicles. Tracer coupling studies of the connexins expressed in HeLa cells showed that coupling through Cx35 gap junctions was reduced by protein kinase A (PKA) activation and enhanced by PKA inhibition through a more than five-fold activity range. Cx34.7 was too poorly expressed to study. PKA regulation suggests that coupling through Cx35 gap junctions can be controlled dynamically through dopamine receptor pathways during light adaptation. If Cx34.7 forms functional cell-cell channels between cones, it would provide a physically separate pathway for electrical coupling. PMID:15201336

  6. Elastic cone for Chinese calligraphy

    NASA Astrophysics Data System (ADS)

    Cai, Fenglei; Li, Haisheng

    2014-01-01

    The brush plays an important role in creating Chinese calligraphy. We regard a single bristle of a writing brush as an elastic rod and the brush tuft absorbing ink as an elastic cone, which naturally deforms according to the force exerted on it when painting on a paper, and the brush footprint is formed by the intersection region between the deformed tuft and the paper plane. To efficiently generate brush strokes, this paper introduces interpolation and texture mapping approach between two adjacent footprints, and automatically applies bristle-splitting texture to the stroke after long-time painting. Experimental results demonstrate that our method is effective and reliable. Users can create realistic calligraphy in real time.

  7. AAV-mediated cone rescue in a naturally occurring mouse model of CNGA3-achromatopsia.

    PubMed

    Pang, Ji-jing; Deng, Wen-Tao; Dai, Xufeng; Lei, Bo; Everhart, Drew; Umino, Yumiko; Li, Jie; Zhang, Keqing; Mao, Song; Boye, Sanford L; Liu, Li; Chiodo, Vince A; Liu, Xuan; Shi, Wei; Tao, Ye; Chang, Bo; Hauswirth, William W

    2012-01-01

    Achromatopsia is a rare autosomal recessive disorder which shows color blindness, severely impaired visual acuity, and extreme sensitivity to bright light. Mutations in the alpha subunits of the cone cyclic nucleotide-gated channels (CNGA3) are responsible for about 1/4 of achromatopsia in the U.S. and Europe. Here, we test whether gene replacement therapy using an AAV5 vector could restore cone-mediated function and arrest cone degeneration in the cpfl5 mouse, a naturally occurring mouse model of achromatopsia with a CNGA3 mutation. We show that gene therapy leads to significant rescue of cone-mediated ERGs, normal visual acuities and contrast sensitivities. Normal expression and outer segment localization of both M- and S-opsins were maintained in treated retinas. The therapeutic effect of treatment lasted for at least 5 months post-injection. This study is the first demonstration of substantial, relatively long-term restoration of cone-mediated light responsiveness and visual behavior in a naturally occurring mouse model of CNGA3 achromatopsia. The results provide the foundation for development of an AAV5-based gene therapy trial for human CNGA3 achromatopsia.

  8. AAV-Mediated Cone Rescue in a Naturally Occurring Mouse Model of CNGA3-Achromatopsia

    PubMed Central

    Dai, Xufeng; Lei, Bo; Everhart, Drew; Umino, Yumiko; Li, Jie; Zhang, Keqing; Mao, Song; Boye, Sanford L.; Liu, Li; Chiodo, Vince A.; Liu, Xuan; Shi, Wei; Tao, Ye; Chang, Bo; Hauswirth, William W.

    2012-01-01

    Achromatopsia is a rare autosomal recessive disorder which shows color blindness, severely impaired visual acuity, and extreme sensitivity to bright light. Mutations in the alpha subunits of the cone cyclic nucleotide-gated channels (CNGA3) are responsible for about 1/4 of achromatopsia in the U.S. and Europe. Here, we test whether gene replacement therapy using an AAV5 vector could restore cone-mediated function and arrest cone degeneration in the cpfl5 mouse, a naturally occurring mouse model of achromatopsia with a CNGA3 mutation. We show that gene therapy leads to significant rescue of cone-mediated ERGs, normal visual acuities and contrast sensitivities. Normal expression and outer segment localization of both M- and S-opsins were maintained in treated retinas. The therapeutic effect of treatment lasted for at least 5 months post-injection. This study is the first demonstration of substantial, relatively long-term restoration of cone-mediated light responsiveness and visual behavior in a naturally occurring mouse model of CNGA3 achromatopsia. The results provide the foundation for development of an AAV5-based gene therapy trial for human CNGA3 achromatopsia. PMID:22509403

  9. Regeneration of Cone Photoreceptors when Cell Ablation Is Primarily Restricted to a Particular Cone Subtype

    PubMed Central

    Fraser, Brittany; DuVal, Michèle G.; Wang, Hao; Allison, W. Ted

    2013-01-01

    We sought to characterize the regenerated cells, if any, when photoreceptor ablation was mostly limited to a particular cone subtype. This allowed us to uniquely assess whether the remaining cells influence specification of regenerating photoreceptors. The ability to replace lost photoreceptors via stem cell therapy holds promise for treating many retinal degenerative diseases. Zebrafish are potent for modelling this because they have robust regenerative capacity emanating from endogenous stem cells, and abundant cone photoreceptors including multiple spectral subtypes similar to human fovea. We ablated the homolog of the human S-cones, the ultraviolet-sensitive (UV) cones, and tested the hypothesis that the photoreceptors regenerating in their place take on identities matching those expected from normal cone mosaic development. We created transgenic fish wherein UV cones can be ablated by addition of a prodrug. Thus photoreceptors developed normally and only the UV cones expressed nitroreductase; the latter converts the prodrug metronidazole to a cell-autonomous neurotoxin. A significant increase in proliferation of progenitor cell populations (p<0.01) was observed when cell ablation was primarily limited to UV cones. In control fish, we found that BrdU primarily incorporated into rod photoreceptors, as expected. However the majority of regenerating photoreceptors became cones when retinal cell ablation was predominantly restricted to UV cones: a 2-fold increase in the relative abundance of cones (p = 0.008) was mirrored by a 35% decrease in rods. By primarily ablating only a single photoreceptor type, we show that the subsequent regeneration is biased towards restoring the cognate photoreceptor type. We discuss the hypothesis that, after cone death, the microenvironment formed by the remaining retinal cells may be influential in determining the identity of regenerating photoreceptors, though other interpretations are plausible. Our novel animal model provides

  10. Thyroid Hormone Signaling and Cone Photoreceptor Viability.

    PubMed

    Ma, Hongwei; Ding, Xi-Qin

    2016-01-01

    Thyroid hormone (TH) signaling regulates cell proliferation, differentiation, and apoptosis. In the retina, TH signaling plays a central role in cone opsin expression. TH signaling inhibits S opsin expression, stimulates M opsin expression, and promotes dorsal-ventral opsin patterning. TH signaling has also been associated with cone photoreceptor viability. Treatment with thyroid hormone triiodothyronine (T3) or induction of high T3 by deleting the hormone-inactivating enzyme type 3 iodothyronine deiodinase (DIO3) causes cone death in mice. This effect is reversed by deletion of the TH receptor (TR) gene. Consistent with the T3 treatment effect, suppressing TH signaling preserves cones in mouse models of retinal degeneration. The regulation of cone survival by TH signaling appears to be independent of its regulatory role in cone opsin expression. The mechanism by which TH signaling regulates cone viability remains to be identified. The current understanding of TH signaling regulation in photoreceptor viability suggests that suppressing TH signaling locally in the retina may represent a novel strategy for retinal degeneration management.

  11. Simultaneous measurement of current and calcium in the ultraviolet-sensitive cones of zebrafish.

    PubMed

    Leung, Yiu Tak; Fain, Gordon L; Matthews, Hugh R

    2007-02-15

    In rods and visible cone photoreceptors, multiple measurements cannot be made of intracellular Ca2+ concentration from the same cell using fluorescent dyes, because a single exposure of the measuring light bleaches too large a fraction of the rod or cone photopigment. We have therefore identified and characterized UV-sensitive cones of the zebrafish, whose wavelength of maximum sensitivity is at 360 nm which is far enough from the wavelength of our measuring light (514.5 nm) so that it has been possible to make multiple determinations of photocurrent and Ca2+ concentration from the same cells. We show that for a limited number of measurements, for which the bleaching of the cone photopigment is too small to affect flash kinetics, the outer segment Ca2+ concentration closely follows the wave form of the flash response convolved with the dominant time constant for Ca2+ removal by Na+-Ca2+-K+ exchange. For a larger number of measurements, significant acceleration of the response kinetics by pigment bleaching inevitably occurs, but the Ca2+ concentration nevertheless rises and falls in approximate agreement with the flash wave form. During exposure to steady background light, the Ca2+ concentration falls in proportion to the steady-state current for dim backgrounds at all times and for bright backgrounds at steady state. At early times following the onset of bright backgrounds, however, the Ca2+ concentration is markedly higher than expected from the current of the cone. We show this to be the result of light-dependent Ca2+ release by bright background light, which can be abolished by pre-exposure of the cone to the membrane-permeant acetoxymethyl ester of the Ca2+ chelator BAPTA. Our results therefore demonstrate that the cone outer segment Ca2+ concentration is predominantly a function of the rate of influx and efflux of Ca2+ across the plasma membrane, but that a release of Ca2+ in bright light most probably from buffer sites within the cell can transiently elevate

  12. Simultaneous measurement of current and calcium in the ultraviolet-sensitive cones of zebrafish

    PubMed Central

    Leung, Yiu Tak; Fain, Gordon L; Matthews, Hugh R

    2007-01-01

    In rods and visible cone photoreceptors, multiple measurements cannot be made of intracellular Ca2+ concentration from the same cell using fluorescent dyes, because a single exposure of the measuring light bleaches too large a fraction of the rod or cone photopigment. We have therefore identified and characterized UV-sensitive cones of the zebrafish, whose wavelength of maximum sensitivity is at 360 nm which is far enough from the wavelength of our measuring light (514.5 nm) so that it has been possible to make multiple determinations of photocurrent and Ca2+ concentration from the same cells. We show that for a limited number of measurements, for which the bleaching of the cone photopigment is too small to affect flash kinetics, the outer segment Ca2+ concentration closely follows the wave form of the flash response convolved with the dominant time constant for Ca2+ removal by Na+–Ca2+–K+ exchange. For a larger number of measurements, significant acceleration of the response kinetics by pigment bleaching inevitably occurs, but the Ca2+ concentration nevertheless rises and falls in approximate agreement with the flash wave form. During exposure to steady background light, the Ca2+ concentration falls in proportion to the steady-state current for dim backgrounds at all times and for bright backgrounds at steady state. At early times following the onset of bright backgrounds, however, the Ca2+ concentration is markedly higher than expected from the current of the cone. We show this to be the result of light-dependent Ca2+ release by bright background light, which can be abolished by pre-exposure of the cone to the membrane-permeant acetoxymethyl ester of the Ca2+ chelator BAPTA. Our results therefore demonstrate that the cone outer segment Ca2+ concentration is predominantly a function of the rate of influx and efflux of Ca2+ across the plasma membrane, but that a release of Ca2+ in bright light most probably from buffer sites within the cell can transiently

  13. Blue cone monochromacy: visual function and efficacy outcome measures for clinical trials.

    PubMed

    Luo, Xunda; Cideciyan, Artur V; Iannaccone, Alessandro; Roman, Alejandro J; Ditta, Lauren C; Jennings, Barbara J; Yatsenko, Svetlana A; Sheplock, Rebecca; Sumaroka, Alexander; Swider, Malgorzata; Schwartz, Sharon B; Wissinger, Bernd; Kohl, Susanne; Jacobson, Samuel G

    2015-01-01

    Blue Cone Monochromacy (BCM) is an X-linked retinopathy caused by mutations in the OPN1LW / OPN1MW gene cluster, encoding long (L)- and middle (M)-wavelength sensitive cone opsins. Recent evidence shows sufficient structural integrity of cone photoreceptors in BCM to warrant consideration of a gene therapy approach to the disease. In the present study, the vision in BCM is examined, specifically seeking clinically-feasible outcomes for a future clinical trial. BCM patients (n = 25, ages 5-72) were studied with kinetic and static chromatic perimetry, full-field sensitivity testing, and eye movement recordings. Vision at the fovea and parafovea was probed with chromatic microperimetry. Kinetic fields with a Goldmann size V target were generally full. Short-wavelength (S-) sensitive cone function was normal or near normal in most patients. Light-adapted perimetry results on conventional background lights were abnormally reduced; 600-nm stimuli were seen by rods whereas white stimuli were seen by both rods and S-cones. Under dark-adapted conditions, 500-nm stimuli were seen by rods in both BCM and normals. Spectral sensitivity functions in the superior retina showed retained rod and S-cone functions in BCM under dark-adapted and light-adapted conditions. In the fovea, normal subjects showed L/M-cone mediation using a 650-nm stimulus under dark-adapted conditions, whereas BCM patients had reduced sensitivity driven by rod vision. Full-field red stimuli on bright blue backgrounds were seen by L/M-cones in normal subjects whereas BCM patients had abnormally reduced and rod-mediated sensitivities. Fixation location could vary from fovea to parafovea. Chromatic microperimetry demonstrated a large loss of sensitivity to red stimuli presented on a cyan adapting background at the anatomical fovea and surrounding parafovea. BCM rods continue to signal vision under conditions normally associated with daylight vision. Localized and retina-wide outcome measures were examined to

  14. Sampling random directions within an elliptical cone

    NASA Astrophysics Data System (ADS)

    Hall, D. C.

    2017-10-01

    This work extends the spherical surface sampling algorithm in order to uniformly generate random directions within an elliptical cone. This has applications in Monte Carlo particle transport simulations, for example modeling asymmetric beam divergence or scattering interactions. Two methods are presented. The first obeys the strict boundary of the elliptical cone. The second relaxes this requirement, increasing the range of generated directions by up to 10% for elliptical cones of extreme eccentricity. However, the second method is able to generate directions beyond the equator.

  15. Sampling random directions within an elliptical cone.

    PubMed

    Hall, D C

    2017-10-01

    This work extends the spherical surface sampling algorithm in order to uniformly generate random directions within an elliptical cone. This has applications in Monte Carlo particle transport simulations, for example modeling asymmetric beam divergence or scattering interactions. Two methods are presented. The first obeys the strict boundary of the elliptical cone. The second relaxes this requirement, increasing the range of generated directions by up to 10% for elliptical cones of extreme eccentricity. However, the second method is able to generate directions beyond the equator.

  16. Cone penetrometer moisture probe acceptance test report

    SciTech Connect

    Barnes, G.A.

    1996-04-23

    This Acceptance Test Report (ATR) documents the results of WHC-SD-WM-ATP-146 (Prototype Cone Penetrometer Moisture Probe Acceptance Test Procedure) and WHC-SD-WM-ATP-145 (Cone Penetrometer Moisture Probe Acceptance Test Procedure). The master copy of WHC-SD-WM-ATP-145 can be found in Appendix A and the master copy of WHC-SD-WM-ATP-146 can be found in Appendix B. Also included with this report is a matrix showing design criteria of the cone penetrometer moisture probe and the verification method used (Appendix C).

  17. Unique photoreceptor arrangements in a fish with polarized light discrimination.

    PubMed

    Novales Flamarique, Iñigo

    2011-03-01

    In contrast to other vertebrates, some anchovies have cone photoreceptors with longitudinally oriented outer segment lamellae. These photoreceptors are axially dichroic (i.e., they are sensitive to the polarization of axially incident light) and form the basis of a polarization detection system in the northern anchovy, Engraulis mordax. Whether other cone types exist in the retina of this animal, and whether multiple cone opsins are expressed in the retinas of anchovies, is unknown. Likewise, a detailed examination of photoreceptor ultrastructure in nondichroic photoreceptors has not been carried out despite its importance to understand visual specializations within the retina and its use in the formulation of models to explain cellular structure. Here, I combined light and electron microscopy with immunohistochemical studies of opsin expression to infer mechanisms of lamellar formation and to evaluate the potential for color vision in the northern anchovy retina. Morphological observations revealed three cone formations: 1) continuous rows made up of alternating long and short (bilobed) cones with longitudinally oriented lamellae that are orthogonal between cone types; 2) continuous rows of alternating long and short cones in which only the short cones have longitudinally oriented lamellae; and 3) rows of triple cones with transversely oriented lamellae, each triple cone consisting of two lateral cones flanking a small central cone. Ultrastructure investigations supported two models of outer segment formation resulting in the longitudinally oriented lamellae of long and short cones. In the case of the long cone, lateral compression of the outer segment, potentially via the formation of guanine platelet stacks in neighboring pigment epithelium cells, results in a shape transformation from conical to cunate and a tilt from transverse to longitudinal lamellae. In the case of the short (bilobed) cone, membrane invaginations from the connecting ciliary structure grow

  18. Rods affect S-cone discrimination on the Farnsworth-Munsell 100-hue test.

    PubMed

    Knight, R; Buck, S L; Fowler, G A; Nguyen, A

    1998-11-01

    Rod influence on hue discrimination was assessed by the Farnsworth-Munsell 100-hue test. Rod influence was taken as the difference in error scores obtained after complete dark adaptation and during the cone plateau at three mesopic (23, 9, 3 td) and one standard (158 td) light level. On the FM 100, rods produced a differential discrimination loss along a tritan axis as compared with a red-green axis without any bias toward a rod confusion axis. Rods appear to impair discrimination mediated by S-cone pathways, which at moderate levels of illumination can differentially elevate tritan errors on the FM 100.

  19. Cone Quasi-Concave Multi-Objective Programming Theory and Dominance Cone Constructions.

    DTIC Science & Technology

    1988-08-01

    4 Cone Quasi-Concave Multi-Objective Prog ramm in(I Theory and Dominance Cone Constructions by A. Chames Z. M. Huang J. J. Rousseau 0. B. Sun 0. L...Report 606 Cone Quasi-Concave Multi-Objective Programming: Theory and Dominance Cone Constructions by A. Chames Z. M. Huang J. J. Rousseau D. B. Sun...permitted for any purpose of the U.S. Govemement. Tr% C CENTER FOR CYBERNETIC STUDIES cV- A. Chames , Director V 3 D 1 College of Business Administration

  20. Some inversion formulas for the cone transform

    NASA Astrophysics Data System (ADS)

    Terzioglu, Fatma

    2015-11-01

    Several novel imaging applications have lead recently to a variety of Radon type transforms, where integration is made over a family of conical surfaces. We call them cone transforms (in 2D they are also called V-line or broken ray transforms). Most prominently, they are present in the so called Compton camera imaging that arises in medical diagnostics, astronomy, and lately in homeland security applications. Several specific incarnations of the cone transform have been considered separately. In this paper, we address the most general (and overdetermined) cone transform, obtain integral relations between cone and Radon transforms in {{{R}}}n, and a variety of inversion formulas. In many applications (e.g., in homeland security), the signal to noise ratio is very low. So, if overdetermined data is collected (as in the case of Compton imaging), attempts to reduce the dimensionality might lead to essential elimination of the signal. Thus, our main concentration is on obtaining formulas involving overdetermined data.

  1. Mars Volcanic Cone with Hydrothermal Deposits

    NASA Image and Video Library

    2010-10-31

    This false color image from NASA Mars Reconnaissance Orbiter indicates that the volcanic cone in the Nili Patera caldera on Mars has hydrothermal mineral deposits on the southern flanks and nearby terrains.

  2. Homologies among Coniferophyte cones: further observations

    NASA Astrophysics Data System (ADS)

    Grauvogel-Stamm, Léa; Galtier, Jean

    1998-04-01

    A reinvestigation of the Triassic conifer pollen cone of Darneya shows evidence that clusters of pollen sacs are attached (adnate), at regular intervals, to the upper side of the stalk and that the distribution of stomata is restricted to the apical part of the abaxial side of the peltate scale. These features and others, such as the commissure visible on the stalk and the scale, suggest a dual nature of the male scale complex of Darneya which therefore is interpreted as an abaxial bract fused with an adaxial fertile shoot bearing several clusters of pollen sacs. This conifer pollen cone is thus considered as a compound strobilus (inflorescence) homologous with the female cone of the conifers and therefore with the cones, both male and female, of the cordaites.

  3. Shatter Cones from the MEMIN Impact Experiments

    NASA Astrophysics Data System (ADS)

    Wilk, J.; Kenkmann, T.

    2015-09-01

    We recovered shatter cone fragments from the MEMIN cratering experiments in sandstone, quartzite and limestone blocks. We analyzed the conical to hyperboloid, curved and striated fracture surfaces with SEM, WLI and produced µm-accurate 3D models.

  4. Arrestin 1 and Cone Arrestin 4 Have Unique Roles in Visual Function in an All-Cone Mouse Retina

    PubMed Central

    Deming, Janise D.; Pak, Joseph S.; Shin, Jung-a; Brown, Bruce M.; Kim, Moon K.; Aung, Moe H.; Lee, Eun-Jin; Pardue, Machelle T.; Craft, Cheryl Mae

    2015-01-01

    Purpose Previous studies discovered cone phototransduction shutoff occurs normally for Arr1−/− and Arr4−/−; however, it is defective when both visual arrestins are simultaneously not expressed (Arr1−/−Arr4−/−). We investigated the roles of visual arrestins in an all-cone retina (Nrl−/−) since each arrestin has differential effects on visual function, including ARR1 for normal light adaptation, and ARR4 for normal contrast sensitivity and visual acuity. Methods We examined Nrl−/−, Nrl−/−Arr1−/−, Nrl−/−Arr4−/−, and Nrl−/−Arr1−/−Arr4−/− mice with photopic electroretinography (ERG) to assess light adaptation and retinal responses, immunoblot and immunohistochemical localization analysis to measure retinal expression levels of M- and S-opsin, and optokinetic tracking (OKT) to measure the visual acuity and contrast sensitivity. Results Study results indicated that Nrl−/− and Nrl−/−Arr4−/− mice light adapted normally, while Nrl−/−Arr1−/− and Nrl−/−Arr1−/−Arr4−/− mice did not. Photopic ERG a-wave, b-wave, and flicker amplitudes followed a general pattern in which Nrl−/−Arr4−/− amplitudes were higher than the amplitudes of Nrl−/−, while the amplitudes of Nrl−/−Arr1−/− and Nrl−/−Arr1−/−Arr4−/− were lower. All three visual arrestin knockouts had faster implicit times than Nrl−/− mice. M-opsin expression is lower when ARR1 is not expressed, while S-opsin expression is lower when ARR4 is not expressed. Although M-opsin expression is mislocalized throughout the photoreceptor cells, S-opsin is confined to the outer segments in all genotypes. Contrast sensitivity is decreased when ARR4 is not expressed, while visual acuity was normal except in Nrl−/−Arr1−/−Arr4−/−. Conclusions Based on the opposite visual phenotypes in an all-cone retina in the Nrl−/−Arr1−/− and Nrl−/−Arr4−/− mice, we conclude that ARR1 and ARR4 perform unique

  5. Exploring the topographic evolution of cinder cones

    NASA Astrophysics Data System (ADS)

    Arrowsmith, R.; Zibart, S.; Gleeman, E.; Alfano, F.; Clarke, A. B.; De'Michieli Vitturi, M.; Dekko, R.

    2013-12-01

    The simple original form and monogenetic character of cinder cones make them interesting targets for the study of landscape evolution. Topographic metrics such as cone height-width ratios and histograms of topographic slope yield useful and portable characterizations of cinder cone relative ages. We explored the topographic evolution of cinder cones by simulating surface processes using numerical and physical experimentation approaches and by collecting high resolution topography over exemplary elements of the San Francisco Volcanic field in northern Arizona. We identified a clear distinction in cone form development between those composed of transport-limited cinder only and those with a capping hard agglutinated rim. We employed a fully 2 dimensional numerical implementation of non linear diffusion with spatially variable transport rates. The agglutinate was idealized as an annulus of diminished transport rate. In the laboratory, we used a simple erosion model consisting of fine mist over a cone of fine sand. The agglutinate was represented with a spray adhesive cap. Non-agglutinated cones show a steady decrease in height and increase in width over time, resulting in a lower height-to-width ratios and greater rounding of profiles than agglutinated cones. The presence of an agglutinate top lessens the degree of rounding, producing a concave profile with a resistant 'neck' as the cone flank erodes, in contrast with non-agglutinated cones which develop into convex-concave profiles. The resistant agglutinate protects itself and the material directly underneath it from erosion; this material stays in place while the sediments around it are transported downslope. The slope distributions start out as bimodal: flat and angle of repose. In the non-agglutinated case, the rounding of the cone and broadening of the base produces a more continuous slope distribution with overall progressive slope decrease from the angle of repose and slope increase from the flat base. The

  6. DEFORMATION OF SCORIA CONE BY CONDUIT PRESSURIZATION

    SciTech Connect

    E.S. Gaffney; B. Damjanac; D. Krier; G. Valentine

    2005-08-26

    A simplified mechanical model is used to simulate the deformation of a scoria cone due to pressurization of magma in a feeder conduit. The scoria cone is modeled as consisting of a cone of stabilized scoria with an axial region of loose scoria (height h{sub 1}), all overlying a vertically oriented cylindrical conduit intruded into rhyolite tuff country rock. For our analyses, the conduit is filled with basalt magma, usually with the upper length (h{sub 2}) solidified. The style of deformation of the cone depends on both h{sub 1} and h{sub 2}. If magma is prevented from hydrofracturing out of the conduit (as, for example, might be the case if the magma is surrounded by a solidified, but plastically deformable layer acting as a gasket backed up by the brittle country rock) pressures in the magma can build to 10s of MPa. When h{sub 1} is 100 m, not unusual for a small isolated basaltic cinder cone, the magma pressure needed to destabilize the cone when molten magma extends all the way to the original ground surface (h{sub 2} = 0) is only about one-third of the pressure when the upper part of the conduit is solidified (h{sub 2} = 25m). In the former case, almost the entire upper third of the cone is at failure in tension when the configuration becomes unstable. In the latter case, small portions of the surface of the cone are failing in tension when instability occurs, but a large volume in the central core of the cone is failing in shear or compressions. These results may provide insight into the status of volcanic plumbing, either past or present, beneath scoria cones. Field observations at the Lathrop Wells volcano in southern Nevada identify structures at the outer edge just below the crater rim that appear to be inward-dipping listric normal faults. This may indicate that, near the end of its active stage, the cone was close to failing in this fashion. A companion paper suggests that such a failure could have been quite energetic had it occurred.

  7. A novel mechanism of cone photoreceptor adaptation.

    PubMed

    Howlett, Marcus H C; Smith, Robert G; Kamermans, Maarten

    2017-04-01

    An animal's ability to survive depends on its sensory systems being able to adapt to a wide range of environmental conditions, by maximizing the information extracted and reducing the noise transmitted. The visual system does this by adapting to luminance and contrast. While luminance adaptation can begin at the retinal photoreceptors, contrast adaptation has been shown to start at later stages in the retina. Photoreceptors adapt to changes in luminance over multiple time scales ranging from tens of milliseconds to minutes, with the adaptive changes arising from processes within the phototransduction cascade. Here we show a new form of adaptation in cones that is independent of the phototransduction process. Rather, it is mediated by voltage-gated ion channels in the cone membrane and acts by changing the frequency response of cones such that their responses speed up as the membrane potential modulation depth increases and slow down as the membrane potential modulation depth decreases. This mechanism is effectively activated by high-contrast stimuli dominated by low frequencies such as natural stimuli. However, the more generally used Gaussian white noise stimuli were not effective since they did not modulate the cone membrane potential to the same extent. This new adaptive process had a time constant of less than a second. A critical component of the underlying mechanism is the hyperpolarization-activated current, Ih, as pharmacologically blocking it prevented the long- and mid- wavelength sensitive cone photoreceptors (L- and M-cones) from adapting. Consistent with this, short- wavelength sensitive cone photoreceptors (S-cones) did not show the adaptive response, and we found they also lacked a prominent Ih. The adaptive filtering mechanism identified here improves the information flow by removing higher-frequency noise during lower signal-to-noise ratio conditions, as occurs when contrast levels are low. Although this new adaptive mechanism can be driven by

  8. Substrate Deformation Predicts Neuronal Growth Cone Advance

    PubMed Central

    Athamneh, Ahmad I.M.; Cartagena-Rivera, Alexander X.; Raman, Arvind; Suter, Daniel M.

    2015-01-01

    Although pulling forces have been observed in axonal growth for several decades, their underlying mechanisms, absolute magnitudes, and exact roles are not well understood. In this study, using two different experimental approaches, we quantified retrograde traction force in Aplysia californica neuronal growth cones as they develop over time in response to a new adhesion substrate. In the first approach, we developed a novel method, to our knowledge, for measuring traction forces using an atomic force microscope (AFM) with a cantilever that was modified with an Aplysia cell adhesion molecule (apCAM)-coated microbead. In the second approach, we used force-calibrated glass microneedles coated with apCAM ligands to guide growth cone advance. The traction force exerted by the growth cone was measured by monitoring the microneedle deflection using an optical microscope. Both approaches showed that Aplysia growth cones can develop traction forces in the 100–102 nN range during adhesion-mediated advance. Moreover, our results suggest that the level of traction force is directly correlated to the stiffness of the microneedle, which is consistent with a reinforcement mechanism previously observed in other cell types. Interestingly, the absolute level of traction force did not correlate with growth cone advance toward the adhesion site, but the amount of microneedle deflection did. In cases of adhesion-mediated growth cone advance, the mean needle deflection was 1.05 ± 0.07 μm. By contrast, the mean deflection was significantly lower (0.48 ± 0.06 μm) when the growth cones did not advance. Our data support a hypothesis that adhesion complexes, which can undergo micron-scale elastic deformation, regulate the coupling between the retrogradely flowing actin cytoskeleton and apCAM substrates, stimulating growth cone advance if sufficiently abundant. PMID:26445437

  9. Causes and consequences of inherited cone disorders.

    PubMed

    Roosing, Susanne; Thiadens, Alberta A H J; Hoyng, Carel B; Klaver, Caroline C W; den Hollander, Anneke I; Cremers, Frans P M

    2014-09-01

    Hereditary cone disorders (CDs) are characterized by defects of the cone photoreceptors or retinal pigment epithelium underlying the macula, and include achromatopsia (ACHM), cone dystrophy (COD), cone-rod dystrophy (CRD), color vision impairment, Stargardt disease (STGD) and other maculopathies. Forty-two genes have been implicated in non-syndromic inherited CDs. Mutations in the 5 genes implicated in ACHM explain ∼93% of the cases. On the contrary, only 21% of CRDs (17 genes) and 25% of CODs (8 genes) have been elucidated. The fact that the large majority of COD and CRD-associated genes are yet to be discovered hints towards the existence of unknown cone-specific or cone-sensitive processes. The ACHM-associated genes encode proteins that fulfill crucial roles in the cone phototransduction cascade, which is the most frequently compromised (10 genes) process in CDs. Another 7 CD-associated proteins are required for transport processes towards or through the connecting cilium. The remaining CD-associated proteins are involved in cell membrane morphogenesis and maintenance, synaptic transduction, and the retinoid cycle. Further novel genes are likely to be identified in the near future by combining large-scale DNA sequencing and transcriptomics technologies. For 31 of 42 CD-associated genes, mammalian models are available, 14 of which have successfully been used for gene augmentation studies. However, gene augmentation for CDs should ideally be developed in large mammalian models with cone-rich areas, which are currently available for only 11 CD genes. Future research will aim to elucidate the remaining causative genes, identify the molecular mechanisms of CD, and develop novel therapies aimed at preventing vision loss in individuals with CD in the future.

  10. Comparative studies on the late bleaching processes of four kinds of cone visual pigments and rod visual pigment.

    PubMed

    Sato, Keita; Yamashita, Takahiro; Imamoto, Yasushi; Shichida, Yoshinori

    2012-05-29

    Visual pigments in rod and cone photoreceptor cells of vertebrate retinas are highly diversified photoreceptive proteins that consist of a protein moiety opsin and a light-absorbing chromophore 11-cis-retinal. There are four types of cone visual pigments and a single type of rod visual pigment. The reaction process of the rod visual pigment, rhodopsin, has been extensively investigated, whereas there have been few studies of cone visual pigments. Here we comprehensively investigated the reaction processes of cone visual pigments on a time scale of milliseconds to minutes, using flash photolysis equipment optimized for cone visual pigment photochemistry. We used chicken violet (L-group), chicken blue (M1-group), chicken green (M2-group), and monkey green (L-group) visual pigments as representatives of the respective groups of the phylogenetic tree of cone pigments. The S, M1, and M2 pigments showed the formation of a pH-dependent mixture of meta intermediates, similar to that formed from rhodopsin. Although monkey green (L-group) also formed a mixture of meta intermediates, pH dependency of meta intermediates was not observed. However, meta intermediates of monkey green became pH dependent when the chloride ion bound to the monkey green was replaced with a nitrate ion. These results strongly suggest that rhodopsin and S, M1, and M2 cone visual pigments share a molecular mechanism for activation, whereas the L-group pigment may have a special reaction mechanism involving the chloride-binding site.

  11. AIPL1, A protein linked to blindness, is essential for the stability of enzymes mediating cGMP metabolism in cone photoreceptor cells

    PubMed Central

    Kolandaivelu, Saravanan; Singh, Ratnesh K.; Ramamurthy, Visvanathan

    2014-01-01

    Defects in the photoreceptor-specific gene encoding aryl hydrocarbon receptor interacting protein like-1 (AIPL1) are linked to blinding diseases, including Leber congenital amaurosis (LCA) and cone dystrophy. While it is apparent that AIPL1 is needed for rod and cone function, the role of AIPL1 in cones is not clear. In this study, using an all-cone animal model lacking Aipl1, we show a light-independent degeneration of M- and S-opsin containing cones that proceeds in a ventral-to-dorsal gradient. Aipl1 is needed for stability, assembly and membrane association of cone PDE6, an enzyme crucial for photoreceptor function and survival. Furthermore, RetGC1, a protein linked to LCA that is needed for cGMP synthesis, was dramatically reduced in cones lacking Aipl1. A defect in RetGC1 is supported by our finding that cones lacking Aipl1 exhibited reduced levels of cGMP. These findings are in contrast to the role of Aipl1 in rods, where destabilization of rod PDE6 results in an increase in cGMP levels, which drives rapid rod degeneration. Our results illustrate mechanistic differences behind the death of rods and cones in retinal degenerative disease caused by deficiencies in AIPL1. PMID:24108108

  12. Distributional geometry of squashed cones

    NASA Astrophysics Data System (ADS)

    Fursaev, Dmitri V.; Patrushev, Alexander; Solodukhin, Sergey N.

    2013-08-01

    A regularization procedure developed by D. V. Fursaev and S. N. Solodukhin, [Phys. Rev. D 52, 2133 (1995)PRVDAQ0556-2821] for the integral curvature invariants on manifolds with conical singularities is generalized to the case of squashed cones. In general, the squashed conical singularities do not have rotational O(2) symmetry in a subspace orthogonal to a singular surface Σ so that the surface is allowed to have extrinsic curvatures. A new feature of the squashed conical singularities is that the surface terms in the integral invariants, in the limit of a small angle deficit, now depend also on the extrinsic curvatures of Σ. A case of invariants which are quadratic polynomials of the Riemann curvature is elaborated in different dimensions and applied to several problems related to entanglement entropy. The results are in complete agreement with computations of the logarithmic terms in entanglement entropy of 4D conformal theories [S. N. Solodukhin, Phys. Lett. B 665, 305 (2008)PYLBAJ0370-2693]. Among other applications of the suggested method are logarithmic terms in entanglement entropy of nonconformal theories and a holographic formula for entanglement entropy in theories with gravity duals.

  13. Photonic Landau levels on cones

    NASA Astrophysics Data System (ADS)

    Schine, Nathan; Ryou, Albert; Gromov, Andrey; Sommer, Ariel; Simon, Jonathan

    2016-05-01

    Creating photonic materials with nontrivial topological characteristics has seen burgeoning interest in recent years; however, a major route to topology, a magnetic field for continuum photons, has remained elusive. We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We will discuss the conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids.

  14. Photonic Landau levels on cones

    NASA Astrophysics Data System (ADS)

    Schine, Nathan; Ryou, Albert; Gromov, Andrey; Sommer, Ariel; Simon, Jonathan

    2016-05-01

    We present the first experimental realization of a bulk magnetic field for optical photons. By using a non-planar ring resonator, we induce an image rotation on each round trip through the resonator. This results in a Coriolis/Lorentz force and a centrifugal anticonfining force, the latter of which is cancelled by mirror curvature. Using a digital micromirror device to control both amplitude and phase, we inject arbitrary optical modes into our resonator. Spatial- and energy- resolved spectroscopy tracks photonic eigenstates as residual trapping is reduced, and we observe photonic Landau levels as the eigenstates become degenerate. We show that there is a conical geometry of the resulting manifold for photon dynamics and present a measurement of the local density of states that is consistent with Landau levels on a cone. While our work already demonstrates an integer quantum Hall material composed of photons, we have ensured compatibility with strong photon-photon interactions, which will allow quantum optical studies of entanglement and correlation in manybody systems including fractional quantum Hall fluids.

  15. Cone signals in monostratified and bistratified amacrine cells of adult zebrafish retina.

    PubMed

    Torvund, M M; Ma, T S; Connaughton, V P; Ono, F; Nelson, R F

    2017-05-01

    Strata within the inner plexiform layer (IPL) of vertebrate retinas are suspected to be distinct signaling regions. Functions performed within adult zebrafish IPL strata were examined through microelectrode recording and staining of stratified amacrine types. The stimulus protocol and analysis discriminated the pattern of input from red, green, blue, and UV cones as well as the light-response waveforms in this tetrachromatic species. A total of 36 cells were analyzed. Transient depolarizing waveforms at ON and OFF originated with bistratified amacrine types, whose dendritic planes branched either in IPL sublaminas a & b, or only within sublamina a. Monophasic-sustained depolarizing waveforms originated with types monostratified in IPL s4 (sublamina b). OFF responses hyperpolarized at onset, depolarized at offset, and in some cases depolarized during mid-stimulus. These signals originated with types monostratified in s1 or s2 (sublamina a). Bistratified amacrines received depolarizing signals only from red cones, at both ON and OFF, while s4 stratified ON cells combined red and green cone signals. The s1/s2 stratified OFF cells utilized hyperpolarizing signals from red, red and green, or red and blue cones at ON, but only depolarizing red cone signals at OFF. ON and OFF depolarizing transients from red cones appear widely distributed within IPL strata. "C-type" physiologies, depolarized by some wavelengths, hyperpolarized by others, in biphasic or triphasic spectral patterns, originated with amacrine cells monostratified in s5. Collectively, cells in this stratum processed signals from all cone types. J. Comp. Neurol. 525:1532-1557, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  16. Development of a Cone Penetrometer for Measuring Spectral Characteristics of Soils in Situ

    NASA Technical Reports Server (NTRS)

    Lee, Landris T., Jr.; Malone, Philip G.

    1993-01-01

    A patent was recently granted to the U.S. Army for an adaptation of a soil cone penetrometer that can be used to measure the spectral characteristics (fluorescence or reflectance) of soils adjacent to the penetrometer rod. The system can use a variety of light sources and spectral analytical equipment. A laser induced fluorescence measuring system has proven to be of immediate use in mapping the distribution of oil contaminated soil at waste disposal and oil storage areas. The fiber optic adaptation coupled with a cone penetrometer permits optical characteristics of the in-situ soil to be measured rapidly, safely, and inexpensively. The fiber optic cone penetrometer can be used to gather spectral data to a depth of approximately 25 to 30 m even in dense sands or stiff clays and can investigate 300 m of soil per day. Typical detection limits for oil contamination in sand is on the order of several hundred parts per million.

  17. Distinct and Atypical Intrinsic and Extrinsic Cell Death Pathways between Photoreceptor Cell Types upon Specific Ablation of Ranbp2 in Cone Photoreceptors

    PubMed Central

    Cho, Kyoung-in; Yu, Minzhong; Hao, Ying; Qiu, Sunny; Pillai, Indulekha C. L.; Peachey, Neal S.; Ferreira, Paulo A.

    2013-01-01

    Non-autonomous cell-death is a cardinal feature of the disintegration of neural networks in neurodegenerative diseases, but the molecular bases of this process are poorly understood. The neural retina comprises a mosaic of rod and cone photoreceptors. Cone and rod photoreceptors degenerate upon rod-specific expression of heterogeneous mutations in functionally distinct genes, whereas cone-specific mutations are thought to cause only cone demise. Here we show that conditional ablation in cone photoreceptors of Ran-binding protein-2 (Ranbp2), a cell context-dependent pleiotropic protein linked to neuroprotection, familial necrotic encephalopathies, acute transverse myelitis and tumor-suppression, promotes early electrophysiological deficits, subcellular erosive destruction and non-apoptotic death of cones, whereas rod photoreceptors undergo cone-dependent non-autonomous apoptosis. Cone-specific Ranbp2 ablation causes the temporal activation of a cone-intrinsic molecular cascade highlighted by the early activation of metalloproteinase 11/stromelysin-3 and up-regulation of Crx and CoREST, followed by the down-modulation of cone-specific phototransduction genes, transient up-regulation of regulatory/survival genes and activation of caspase-7 without apoptosis. Conversely, PARP1+-apoptotic rods develop upon sequential activation of caspase-9 and caspase-3 and loss of membrane permeability. Rod photoreceptor demise ceases upon cone degeneration. These findings reveal novel roles of Ranbp2 in the modulation of intrinsic and extrinsic cell death mechanisms and pathways. They also unveil a novel spatiotemporal paradigm of progression of neurodegeneration upon cell-specific genetic damage whereby a cone to rod non-autonomous death pathway with intrinsically distinct cell-type death manifestations is triggered by cell-specific loss of Ranbp2. Finally, this study casts new light onto cell-death mechanisms that may be shared by human dystrophies with distinct retinal spatial

  18. Distinct and atypical intrinsic and extrinsic cell death pathways between photoreceptor cell types upon specific ablation of Ranbp2 in cone photoreceptors.

    PubMed

    Cho, Kyoung-In; Haque, Mdemdadul; Wang, Jessica; Yu, Minzhong; Hao, Ying; Qiu, Sunny; Pillai, Indulekha C L; Peachey, Neal S; Ferreira, Paulo A

    2013-06-01

    Non-autonomous cell-death is a cardinal feature of the disintegration of neural networks in neurodegenerative diseases, but the molecular bases of this process are poorly understood. The neural retina comprises a mosaic of rod and cone photoreceptors. Cone and rod photoreceptors degenerate upon rod-specific expression of heterogeneous mutations in functionally distinct genes, whereas cone-specific mutations are thought to cause only cone demise. Here we show that conditional ablation in cone photoreceptors of Ran-binding protein-2 (Ranbp2), a cell context-dependent pleiotropic protein linked to neuroprotection, familial necrotic encephalopathies, acute transverse myelitis and tumor-suppression, promotes early electrophysiological deficits, subcellular erosive destruction and non-apoptotic death of cones, whereas rod photoreceptors undergo cone-dependent non-autonomous apoptosis. Cone-specific Ranbp2 ablation causes the temporal activation of a cone-intrinsic molecular cascade highlighted by the early activation of metalloproteinase 11/stromelysin-3 and up-regulation of Crx and CoREST, followed by the down-modulation of cone-specific phototransduction genes, transient up-regulation of regulatory/survival genes and activation of caspase-7 without apoptosis. Conversely, PARP1+ -apoptotic rods develop upon sequential activation of caspase-9 and caspase-3 and loss of membrane permeability. Rod photoreceptor demise ceases upon cone degeneration. These findings reveal novel roles of Ranbp2 in the modulation of intrinsic and extrinsic cell death mechanisms and pathways. They also unveil a novel spatiotemporal paradigm of progression of neurodegeneration upon cell-specific genetic damage whereby a cone to rod non-autonomous death pathway with intrinsically distinct cell-type death manifestations is triggered by cell-specific loss of Ranbp2. Finally, this study casts new light onto cell-death mechanisms that may be shared by human dystrophies with distinct retinal spatial

  19. Matrix theory interpretation of discrete light cone quantization string worldsheets

    PubMed

    Grignani; Orland; Paniak; Semenoff

    2000-10-16

    We study the null compactification of type-IIA string perturbation theory at finite temperature. We prove a theorem about Riemann surfaces establishing that the moduli spaces of infinite-momentum-frame superstring worldsheets are identical to those of branched-cover instantons in the matrix-string model conjectured to describe M theory. This means that the identification of string degrees of freedom in the matrix model proposed by Dijkgraaf, Verlinde, and Verlinde is correct and that its natural generalization produces the moduli space of Riemann surfaces at all orders in the genus expansion.

  20. "Light-cone" dynamics after quantum quenches in spin chains.

    PubMed

    Bonnes, Lars; Essler, Fabian H L; Läuchli, Andreas M

    2014-10-31

    Signal propagation in the nonequilibrium evolution after quantum quenches has recently attracted much experimental and theoretical interest. A key question arising in this context is what principles, and which of the properties of the quench, determine the characteristic propagation velocity. Here we investigate such issues for a class of quench protocols in one of the central paradigms of interacting many-particle quantum systems, the spin-1/2 Heisenberg XXZ chain. We consider quenches from a variety of initial thermal density matrices to the same final Hamiltonian using matrix product state methods. The spreading velocities are observed to vary substantially with the initial density matrix. However, we achieve a striking data collapse when the spreading velocity is considered to be a function of the excess energy. Using the fact that the XXZ chain is integrable, we present an explanation of the observed velocities in terms of "excitations" in an appropriately defined generalized Gibbs ensemble.

  1. Light cones in relativity: Real, complex, and virtual, with applications

    NASA Astrophysics Data System (ADS)

    Adamo, T. M.; Newman, E. T.

    2011-02-01

    We study geometric structures associated with shear-free null geodesic congruences in Minkowski space-time and asymptotically shear-free null geodesic congruences in asymptotically flat space-times. We show how in both the flat and asymptotically flat settings, complexified future null infinity IC+ acts as a “holographic screen,” interpolating between two dual descriptions of the null geodesic congruence. One description constructs a complex null geodesic congruence in a complex space-time whose source is a complex worldline, a virtual source as viewed from the holographic screen. This complex null geodesic congruence intersects the real asymptotic boundary when its source lies on a particular open-string type structure in the complex space-time. The other description constructs a real, twisting, shear-free or asymptotically shear-free null geodesic congruence in the real space-time, whose source (at least in Minkowski space) is in general a closed-string structure: the caustic set of the congruence. Finally we show that virtually all of the interior space-time physical quantities that are identified at null infinity I+ (center of mass, spin, angular momentum, linear momentum, and force) are given kinematic meaning and dynamical descriptions in terms of the complex worldline.

  2. Retinal cone and rod photoreceptor cells exhibit differential susceptibility to light–induced damage

    PubMed Central

    Okano, Kiichiro; Maeda, Akiko; Chen, Yu; Chauhan, Vishal; Tang, Johnny; Palczewska, Grazyna; Sakai, Tsutomu; Tsuneoka, Hiroshi; Palczewski, Krzysztof; Maeda, Tadao

    2012-01-01

    All-trans-retinal and its condensation-products can cause retinal degeneration in a light–dependent manner and contribute to the pathogenesis of human macular diseases such as Stargardt’s disease and age–related macular degeneration (AMD). Although these toxic retinoid by–products originate from rod and cone photoreceptor cells, the contribution of each cell type to light–induced retinal degeneration is unknown. Here the primary objective was to learn whether rods or cones are more susceptible to light–induced, all–trans–retinal–mediated damage. Previously, we reported that mice lacking enzymes that clear all–trans–retinal from the retina, ATP–binding cassette transporter 4 (ABCA4) and retinol dehydrogenase 8 (RDH8), manifested light-induced retinal dystrophy. We first examined early-stage-AMD patients and found retinal degenerative changes in rod-rich rather than cone-rich regions of the macula. We then evaluated transgenic mice with rod–only and cone–like–only retinas in addition to progenies of such mice inbred with Rdh8−/− Abca4−/− mice. Of all these strains, Rdh8−/− Abca4−/− mice with a mixed rod–cone population showed the most severe retinal degeneration under regular cyclic light conditions. Intense light exposure induced acute retinal damage in Rdh8−/− Abca4−/− and rod–only mice but not cone–like–only mice. These findings suggest that progression of retinal degeneration in Rdh8-/- Abca4-/- mice is affected by differential vulnerability of rods and cones to light. PMID:22220722

  3. Dephosphorylation during Bleach and Regeneration of Visual Pigment in Carp Rod and Cone Membranes*

    PubMed Central

    Yamaoka, Hiromi; Tachibanaki, Shuji; Kawamura, Satoru

    2015-01-01

    On absorption of light by vertebrate visual pigment, the chromophore, 11-cis retinal, is isomerized to all-trans retinal to activate the phototransduction cascade, which leads to a hyperpolarizing light response. Activated pigment is inactivated by phosphorylation on the protein moiety, opsin. Isomerized all-trans retinal is ultimately released from opsin, and the pigment is regenerated by binding to 11-cis retinal. In this pigment regeneration cycle, the phosphates incorporated should be removed in order that the pigment regains the capability of activating the phototransduction cascade. However, it is not clear yet how pigment dephosphorylation takes place in the regeneration cycle. First in this study, we tried to estimate the dephosphorylation activity in living carp rods and cones and found that the activity, which is present mainly in the cytoplasm in both rods and cones, is three times higher in cones than in rods. Second, we examined at which stage the dephosphorylation takes place; before or after the release of all-trans retinal, during pigment regeneration, or after pigment regeneration. For this purpose we prepared three types of phosphorylated substrates in purified carp rod and cone membranes: phosphorylated bleaching intermediate, phosphorylated opsin, and phosphorylated and regenerated pigment. We also examined the effect of pigment regeneration on the dephosphorylation. The results showed that the dephosphorylation does not show substrate preference in the regeneration cycle and suggested that the dephosphorylation takes place constantly. The results also suggest that, under bright light, some of the regenerated visual pigment remains phosphorylated to reduce the light sensitivity in cones. PMID:26286749

  4. Dephosphorylation during bleach and regeneration of visual pigment in carp rod and cone membranes.

    PubMed

    Yamaoka, Hiromi; Tachibanaki, Shuji; Kawamura, Satoru

    2015-10-02

    On absorption of light by vertebrate visual pigment, the chromophore, 11-cis retinal, is isomerized to all-trans retinal to activate the phototransduction cascade, which leads to a hyperpolarizing light response. Activated pigment is inactivated by phosphorylation on the protein moiety, opsin. Isomerized all-trans retinal is ultimately released from opsin, and the pigment is regenerated by binding to 11-cis retinal. In this pigment regeneration cycle, the phosphates incorporated should be removed in order that the pigment regains the capability of activating the phototransduction cascade. However, it is not clear yet how pigment dephosphorylation takes place in the regeneration cycle. First in this study, we tried to estimate the dephosphorylation activity in living carp rods and cones and found that the activity, which is present mainly in the cytoplasm in both rods and cones, is three times higher in cones than in rods. Second, we examined at which stage the dephosphorylation takes place; before or after the release of all-trans retinal, during pigment regeneration, or after pigment regeneration. For this purpose we prepared three types of phosphorylated substrates in purified carp rod and cone membranes: phosphorylated bleaching intermediate, phosphorylated opsin, and phosphorylated and regenerated pigment. We also examined the effect of pigment regeneration on the dephosphorylation. The results showed that the dephosphorylation does not show substrate preference in the regeneration cycle and suggested that the dephosphorylation takes place constantly. The results also suggest that, under bright light, some of the regenerated visual pigment remains phosphorylated to reduce the light sensitivity in cones.

  5. Genetic Dissection of Rod and Cone Pathways in the Dark-Adapted Mouse Retina

    PubMed Central

    Abd-El-Barr, Muhammad M.; Pennesi, Mark E.; Saszik, Shannon M.; Barrow, Andrew J.; Lem, Janis; Bramblett, Debra E.; Paul, David L.; Frishman, Laura J.; Wu, Samuel M.

    2009-01-01

    A monumental task of the mammalian retina is to encode an enormous range (>109-fold) of light intensities experienced by the animal in natural environments. Retinal neurons carry out this task by dividing labor into many parallel rod and cone synaptic pathways. Here we study the operational plan of various rod- and cone-mediated pathways by analyzing electroretinograms (ERGs), primarily b-wave responses, in dark-adapted wildtype, connexin36 knockout, depolarizing rod–bipolar cell (DBCR) knockout, and rod transducin alpha-subunit knockout mice [WT, Cx36(−/−), Bhlhb4(−/−), and Trα(−/−)]. To provide additional insight into the cellular origins of various components of the ERG, we compared dark-adapted ERG responses with response dynamic ranges of individual retinal cells recorded with patch electrodes from dark-adapted mouse retinas published from other studies. Our results suggest that the connexin36-mediated rod–cone coupling is weak when light stimulation is weak and becomes stronger as light stimulation increases in strength and that rod signals may be transmitted to some DBCCs via direct chemical synapses. Moreover, our analysis indicates that DBCR responses contribute about 80% of the overall DBC response to scotopic light and that rod and cone signals contribute almost equally to the overall DBC responses when stimuli are strong enough to saturate the rod bipolar cell response. Furthermore, our study demonstrates that analysis of ERG b-wave of dark-adapted, pathway-specific mutants can be used as an in vivo tool for dissecting rod and cone synaptic pathways and for studying the functions of pathway-specific gene products in the retina. PMID:19587322

  6. Rapid Retinal Release from a Cone Visual Pigment Following Photoactivation*

    PubMed Central

    Chen, Min-Hsuan; Kuemmel, Colleen; Birge, Robert R.; Knox, Barry E.

    2012-01-01

    As part of the visual cycle, the retinal chromophore in both rod and cone visual pigments undergoes reversible Schiff base hydrolysis and dissociation following photobleaching. We characterized light-activated retinal release from a short-wavelength sensitive cone pigment (VCOP) in 0.1% dodecyl maltoside using fluorescence spectroscopy. The half-time (t1/2) of retinal release from VCOP was 7.1 s, 250-fold faster than rhodopsin. VCOP exhibited pH-dependent release kinetics, with the t1/2 decreasing from 23 s to 4 s with pH 4.1 to 8, respectively. However, the Arrhenius activation energy (Ea) for VCOP derived from kinetic measurements between 4° and 20°C was 17.4 kcal/mol, similar to 18.5 kcal/mol for rhodopsin. There was a small kinetic isotope (D2O) effect in VCOP, but less than that observed in rhodopsin. Mutation of the primary Schiff base counterion (VCOPD108A) produced a pigment with an unprotonated chromophore (⌊max = 360 nm) and dramatically slowed (t1/2 ~ 6.8 min) light-dependent retinal release. Using homology modeling, a VCOP mutant with two substitutions (S85D/ D108A) was designed to move the counterion one alpha helical turn into the transmembrane region from the native position. This double mutant had a UV-visible absorption spectrum consistent with a protonated Schiff base (⌊max = 420 nm). Moreover, VCOPS85D/D108A mutant had retinal release kinetics (t1/2 = 7 s) and Ea (18 kcal/mol) similar to the native pigment exhibiting no pH-dependence. By contrast, the single mutant VCOPS85D had a ~3-fold decrease in retinal release rate compared to the native pigment. Photoactivated VCOPD108A had kinetics comparable to a rhodopsin counterion mutant, RhoE113Q, both requiring hydroxylamine to fully release retinal. These results demonstrate that the primary counterion of cone visual pigments is necessary for efficient Schiff base hydrolysis. We discuss how the large differences in retinal release rates between rod and cone visual pigments arise, not from

  7. Ecophysiological variables influencing Aleppo pine seed and cone production: a review.

    PubMed

    Ayari, Abdelaziz; Khouja, Mohamed Larbi

    2014-04-01

    The most interesting factors associated with seed and cone production of Aleppo pine were largely reviewed to identify broad patterns and potential effectiveness of reforestation efforts and planning. Aleppo pine cone production and seed yields are relatively variable, with differences between spatial and temporal influences. These differences are considered, mainly between (i) year, (ii) stand characteristics and (iii) individual tree measurements. Annual variability among populations was recorded for cone production per tree, based on influencing factors such as genetic characteristics, wetness, nutrient availability, insect pests and disease. In addition, some factors may affect Aleppo pine tree growth directly but may be affecting seed and cone production indirectly. Therefore, reduced stand density results in less competition among Aleppo pine trees and accompanying understory flora, which subsequently increases the stem diameter and other tree dimensions, including seed production. This review suggests that reforestation planning, particularly thinning, will result in improved tree morphology that will increase Aleppo pine seed and cone crops. Wildfire intensity and stand conditions such as light and soil nutrient status are also examined.

  8. Speed, Spatial, and Temporal Tuning of Rod and Cone Vision in Mouse

    PubMed Central

    Umino, Yumiko; Solessio, Eduardo; Barlow, Robert B.

    2009-01-01

    Rods and cones subserve mouse vision over a 100 million-fold range of light intensity (−6 to 2 log cd m −2). Rod pathways tune vision to the temporal frequency of stimuli (peak, 0.75 Hz) and cone pathways to their speed (peak, ~12°/s). Both pathways tune vision to the spatial components of stimuli (0.064–0.128 cycles/°). The specific photoreceptor contributions were determined by two-alternative, forced-choice measures of contrast thresholds for optomotor responses of C57BL/6J mice with normal vision, Gnat2cpfl3 mice without functional cones, and Gnat1−/− mice without functional rods. Gnat2cpfl3 mice (threshold,−6.0 log cd m −2) cannot see rotating gratings above −2.0 log cd m −2 (photopic vision), and Gnat1−/− mice (threshold, −4.0 log cd m −2) are blind below −4.0 log cd m −2 (scotopic vision). Both genotypes can see in the transitional mesopic range (−4.0 to −2.0 log cd m −2). Mouse rod and cone sensitivities are similar to those of human. This parametric study characterizes the functional properties of the mouse visual system, revealing the rod and cone contributions to contrast sensitivity and to the temporal processing of visual stimuli. PMID:18171936

  9. Circuitry to explain how the relative number of L and M cones shapes color experience

    PubMed Central

    Schmidt, Brian P.; Touch, Phanith; Neitz, Maureen; Neitz, Jay

    2016-01-01

    The wavelength of light that appears unique yellow is surprisingly consistent across people even though the ratio of middle (M) to long (L) wavelength sensitive cones is strikingly variable. This observation has been explained by normalization to the mean spectral distribution of our shared environment. Our purpose was to reconcile the nearly perfect alignment of everyone's unique yellow through a normalization process with the striking variability in unique green, which varies by as much as 60 nm between individuals. The spectral location of unique green was measured in a group of volunteers whose cone ratios were estimated with a technique that combined genetics and flicker photometric electroretinograms. In contrast to unique yellow, unique green was highly dependent upon relative cone numerosity. We hypothesized that the difference in neural architecture of the blue-yellow and red-green opponent systems in the presence of a normalization process creates the surprising dependence of unique green on cone ratio. We then compared the predictions of different theories of color vision processing that incorporate L and M cone ratio and a normalization process. The results of this analysis reveal that—contrary to prevailing notions--postretinal contributions may not be required to explain the phenomena of unique hues. PMID:27366885

  10. Sodium-dependent calcium extrusion and sensitivity regulation in retinal cones of the salamander.

    PubMed Central

    Nakatani, K; Yau, K W

    1989-01-01

    1. Membrane current was recorded from an isolated, dark-adapted salamander cone by sucking its inner segment into a tight-fitting glass pipette containing Ringer solution. The outer segment of the cell was exposed to a bath solution that could be changed rapidly. 2. After removing Na+ from the bath Ringer solution for a short period of time in darkness (the 'loading period'), a transient inward current was observed upon restoring it in bright light. A similar but longer-lasting current was observed when Na+ was restored in the light after a large Ca2+ influx was induced through the light-sensitive conductance in darkness. 3. The above transient current was not observed if Li+ or guanidinium was substituted for Na+ in the light, or if Ba2+ was substituted for Ca2+ during the dark loading period. However, a current was observed if Sr2+ was the substituting ion for Ca2+ during loading. These observations suggested that the current was associated with an electrogenic Na+-dependent Ca2+ efflux at the cone outer segment. 4. The saturated amplitude of the exchange current was 12-25 pA with a mean around 16 pA. This is very comparable to that measured in the outer segment of a salamander rod under similar conditions. 5. By comparing a known Ca2+ load in a cone outer segment to the subsequent charge transfer through the exchange, we estimated that the stoichiometry of the exchange was near 3Na+:1Ca2+. 6. With a small Ca2+ load, or in the presence of Cs+ around the inner segment, the final temporal decline of the Na+-Ca2+ exchange current was roughly exponential, with a mean time constant of about 100 ms. This decline is about four times faster than that measured in rods. We interpret the shorter time constant in cones to reflect a faster rate of decline of intracellular free Ca2+ in their outer segments resulting from the exchange activity. 7. In the absence of external Na+, and hence any Na+-dependent Ca2+ efflux, the absolute sensitivity of a cone to a dim flash was

  11. Cone-Deciphered Modes of Problem Solving Action (MPSA Cone): Alternative Perspectives on Diversified Professions.

    ERIC Educational Resources Information Center

    Lai, Su-Huei

    A conceptual framework of the modes of problem-solving action has been developed on the basis of a simple relationship cone to assist individuals in diversified professions in inquiry and implementation of theory and practice in their professional development. The conceptual framework is referred to as the Cone-Deciphered Modes of Problem Solving…

  12. Pulsating Electrohydrodynamic Cone-Jets: from Choked Jet to Oscillating Cone

    NASA Astrophysics Data System (ADS)

    Bober, David; Chen, Chuan-Hua

    2011-11-01

    Pulsating cone-jets occur in a variety of electrostatic spraying and printing systems. We report an experimental study of the pulsation frequency to reconcile two models based on a choked jet and an oscillating cone, respectively. The two regimes are demarcated by the ratio of the supplied flow rate (Qs) to the minimum flow rate (Qm) required for a steady Taylor cone-jet. When Qs Qm , the Taylor cone anchored at the nozzle experiences a capillary oscillation analogous to the Rayleigh mode of a free drop; the pulsation frequency in the oscillating cone regime plateaus to the capillary oscillation frequency which is independent of Qs /Qm .

  13. Cone opsin determines the time course of cone photoreceptor degeneration in Leber congenital amaurosis

    PubMed Central

    Zhang, Tao; Zhang, Ning; Baehr, Wolfgang; Fu, Yingbin

    2011-01-01

    Mutations in RPE65 or lecithin-retinol acyltransferase (LRAT) disrupt 11-cis-retinal recycling and cause Leber congenital amaurosis (LCA), the most severe retinal dystrophy in early childhood. We used Lrat−/−, a murine model for LCA, to investigate the mechanism of rapid cone degeneration. Although both M and S cone opsins mistrafficked as reported previously, mislocalized M-opsin was degraded whereas mislocalized S-opsin accumulated in Lrat−/− cones before the onset of massive ventral/central cone degeneration. As the ventral and central retina express higher levels of S-opsin than the dorsal retina in mice, our results may explain why ventral and central cones degenerate more rapidly than dorsal cones in Rpe65−/− and Lrat−/− LCA models. In addition, human blue opsin and mouse S-opsin, but not mouse M-opsin or human red/green opsins, aggregated to form cytoplasmic inclusions in transfected cells, which may explain why blue cone function is lost earlier than red/green-cone function in patients with LCA. The aggregation of short-wavelength opsins likely caused rapid cone degenerations through an endoplasmic reticulum stress pathway, as demonstrated in both the Lrat−/− retina and transfected cells. Replacing rhodopsin with S-opsin in Lrat−/− rods resulted in mislocalization and aggregation of S-opsin in the inner segment and the synaptic region of rods, ER stress, and dramatically accelerated rod degeneration. Our results demonstrate that cone opsins play a major role in determining the degeneration rate of photoreceptors in LCA. PMID:21555576

  14. Statistical analysis of cone penetration resistance of railway ballast

    NASA Astrophysics Data System (ADS)

    Saussine, Gilles; Dhemaied, Amine; Delforge, Quentin; Benfeddoul, Selim

    2017-06-01

    Dynamic penetrometer tests are widely used in geotechnical studies for soils characterization but their implementation tends to be difficult. The light penetrometer test is able to give information about a cone resistance useful in the field of geotechnics and recently validated as a parameter for the case of coarse granular materials. In order to characterize directly the railway ballast on track and sublayers of ballast, a huge test campaign has been carried out for more than 5 years in order to build up a database composed of 19,000 penetration tests including endoscopic video record on the French railway network. The main objective of this work is to give a first statistical analysis of cone resistance in the coarse granular layer which represents a major component of railway track: the ballast. The results show that the cone resistance (qd) increases with depth and presents strong variations corresponding to layers of different natures identified using the endoscopic records. In the first zone corresponding to the top 30cm, (qd) increases linearly with a slope of around 1MPa/cm for fresh ballast and fouled ballast. In the second zone below 30cm deep, (qd) increases more slowly with a slope of around 0,3MPa/cm and decreases below 50cm. These results show that there is no clear difference between fresh and fouled ballast. Hence, the (qd) sensitivity is important and increases with depth. The (qd) distribution for a set of tests does not follow a normal distribution. In the upper 30cm layer of ballast of track, data statistical treatment shows that train load and speed do not have any significant impact on the (qd) distribution for clean ballast; they increase by 50% the average value of (qd) for fouled ballast and increase the thickness as well. Below the 30cm upper layer, train load and speed have a clear impact on the (qd) distribution.

  15. Thermoelastic Damping in Cone Microcantilever Resonator

    NASA Astrophysics Data System (ADS)

    Li, Pu; Zhou, Hongyue

    2017-07-01

    Microbeams with continuous or discontinuous variable cross-section have been applied in Microelectromechanical Systems (MEMS) resonators, such as tapered microbeam, torsion microbeam and stepped microbeam. Thermoelastic damping (TED), which is verified as a fundamental energy lost mechanism for microresonators, is calculated by the Zener’s model and Lifshits and Roukes’s (LR) model in general. However, for non-uniform microbeam resonators, these two classical models are not suitable in some cases. On the basis of Zener’s theory, a TED model for cone microcantilever with rectangular cross-section has been derived in this study. The comparison of results obtained by the present model and Finite Element Method (FEM) model proves that the proposed model is able to predict TED value for cone microcantilever. In addition, TED in cone microcantilever is nearly same as TED in wedge microcantilever. The results show that quality factors (Q-factors) of cone microcantilever and wedge microcantilever are larger than Q-factor of uniform microbeam at low frequencies. The Debye peak value of a uniform microcantilever is equal to 0.5Δ E , while those of cone microcantilever and wedge microcantilever are about 0.438ΔE and 0.428ΔE, respectively.

  16. Strain engineering of Dirac cones in graphyne

    SciTech Connect

    Wang, Gaoxue; Kumar, Ashok; Pandey, Ravindra; Si, Mingsu

    2014-05-26

    6,6,12-graphyne, one of the two-dimensional carbon allotropes with the rectangular lattice structure, has two kinds of non-equivalent anisotropic Dirac cones in the first Brillouin zone. We show that Dirac cones can be tuned independently by the uniaxial compressive strain applied to graphyne, which induces n-type and p-type self-doping effect, by shifting the energy of the Dirac cones in the opposite directions. On the other hand, application of the tensile strain results into a transition from gapless to finite gap system for the monolayer. For the AB-stacked bilayer, the results predict tunability of Dirac-cones by in-plane strains as well as the strain applied perpendicular to the plane. The group velocities of the Dirac cones show enhancement in the resistance anisotropy for bilayer relative to the case of monolayer. Such tunable and direction-dependent electronic properties predicted for 6,6,12-graphyne make it to be competitive for the next-generation electronic devices at nanoscale.

  17. Whiskers, cones and pyramids created in sputtering by ion bombardment

    NASA Technical Reports Server (NTRS)

    Wehner, G. K.

    1979-01-01

    A thorough study of the role which foreign atoms play in cone formation during sputtering of metals revealed many experimental facts. Two types of cone formation were distinquished, deposit cones and seed cones. Twenty-six combinations of metals for seed cone formation were tested. The sputtering yield variations with composition for combinations which form seed cones were measured. It was demonstrated that whisker growth becomes a common occurrence when low melting point material is sputter deposited on a hot nonsputtered high melting point electrode.

  18. Light enhances learned fear

    PubMed Central

    Warthen, Daniel M.; Wiltgen, Brian J.; Provencio, Ignacio

    2011-01-01

    The ability to learn, remember, and respond to emotional events is a powerful survival strategy. However, dysregulated behavioral and physiological responses to these memories are maladaptive. To fully understand learned fear and the pathologies that arise during response malfunction we must reveal the environmental variables that influence learned fear responses. Light, a ubiquitous environmental feature, modulates cognition and anxiety. We hypothesized that light modulates responses to learned fear. Using tone-cued fear conditioning, we found that light enhances behavioral responses to learned fear in C57BL/6J mice. Mice in light freeze more in response to a conditioned cue than mice in darkness. The absence of significant freezing during a 2-wk habituation period and during intertrial intervals indicated that light specifically modulates freezing to the learned acoustic cue rather than the context of the experimental chamber. Repeating our assay in two photoreceptor mutant models, Pde6brd1/rd1 and Opn4−/− mice, revealed that light-dependent enhancement of conditioned fear is driven primarily by the rods and/or cones. By repeating our protocol with an altered lighting regimen, we found that lighting conditions acutely modulate responses when altered between conditioning and testing. This is manifested either as an enhancement of freezing when light is added during testing or as a depression of freezing when light is removed during testing. Acute enhancement, but not depression, requires both rod/cone- and melanopsin-dependent photoreception. Our results demonstrate a modulation by light of behavioral responses to learned fear. PMID:21808002

  19. Light enhances learned fear.

    PubMed

    Warthen, Daniel M; Wiltgen, Brian J; Provencio, Ignacio

    2011-08-16

    The ability to learn, remember, and respond to emotional events is a powerful survival strategy. However, dysregulated behavioral and physiological responses to these memories are maladaptive. To fully understand learned fear and the pathologies that arise during response malfunction we must reveal the environmental variables that influence learned fear responses. Light, a ubiquitous environmental feature, modulates cognition and anxiety. We hypothesized that light modulates responses to learned fear. Using tone-cued fear conditioning, we found that light enhances behavioral responses to learned fear in C57BL/6J mice. Mice in light freeze more in response to a conditioned cue than mice in darkness. The absence of significant freezing during a 2-wk habituation period and during intertrial intervals indicated that light specifically modulates freezing to the learned acoustic cue rather than the context of the experimental chamber. Repeating our assay in two photoreceptor mutant models, Pde6b(rd1/rd1) and Opn4(-/-) mice, revealed that light-dependent enhancement of conditioned fear is driven primarily by the rods and/or cones. By repeating our protocol with an altered lighting regimen, we found that lighting conditions acutely modulate responses when altered between conditioning and testing. This is manifested either as an enhancement of freezing when light is added during testing or as a depression of freezing when light is removed during testing. Acute enhancement, but not depression, requires both rod/cone- and melanopsin-dependent photoreception. Our results demonstrate a modulation by light of behavioral responses to learned fear.

  20. Neovascularization, enhanced inflammatory response, and age-related cone dystrophy in the Nrl-/-Grk1-/- mouse retina.

    PubMed

    Yetemian, Rosanne M; Brown, Bruce M; Craft, Cheryl M

    2010-12-01

    The effects of aging and light exposure on cone photoreceptor survival were compared between mouse retinas of neural retina leucine zipper knockout (Nrl(-/-)) mice and double-knockout mice lacking G-protein-coupled receptor kinase 1 (Nrl(-/-)Grk1(-/-)). Mice were reared in total darkness, ambient cyclic light, or constant light, and their retinas were evaluated from 1 to 9 months of age using immunohistochemistry, electroretinography, and fluorescein angiography. Retinal gene expression and statistically significant probe sets were categorized using analysis software. Select gene expression changes were confirmed with quantitative RT-PCR. In contrast to retinas from Nrl(-/-), those from Nrl(-/-)Grk1(-/-) exhibit a progressive loss of the outer nuclear layer, retinal physiology deficits, and a higher rate of degeneration with increasing age that is independent of environmental light exposure. Changes in retinal neovascularization occur in the Nrl(-/-)Grk1(-/-) at 1 month, before the onset of significant cone functional deficits. Microarray analyses demonstrate statistically significant changes in transcript levels of more than 400 genes, of which the oncostatin M signaling pathway and the inflammatory disease response network were identified. These data demonstrate that the loss of functional Grk1 on the enhanced S-cone Nrl(-/-) background exacerbates age-related cone dystrophy in a light-independent manner, mediated partly through the inflammatory response pathway and neovascularization. According to these findings, Grk1 helps to maintain a healthy cone environment, and the Nrl(-/-)Grk1(-/-) mouse allows examination of the alternative roles of Grk1 in cone photoreceptor homeostasis.

  1. Lentiviral Gene Transfer of Rpe65 Rescues Survival and Function of Cones in a Mouse Model of Leber Congenital Amaurosis

    PubMed Central

    Crippa, Sylvain V; Hauswirth, William W; Lem, Janis; Munier, Francis L; Seeliger, Mathias W; Wenzel, Andreas; Arsenijevic, Yvan

    2006-01-01

    Background RPE65 is specifically expressed in the retinal pigment epithelium and is essential for the recycling of 11-cis-retinal, the chromophore of rod and cone opsins. In humans, mutations in RPE65 lead to Leber congenital amaurosis or early-onset retinal dystrophy, a severe form of retinitis pigmentosa. The proof of feasibility of gene therapy for RPE65 deficiency has already been established in a dog model of Leber congenital amaurosis, but rescue of the cone function, although crucial for human high-acuity vision, has never been strictly proven. In Rpe65 knockout mice, photoreceptors show a drastically reduced light sensitivity and are subject to degeneration, the cone photoreceptors being lost at early stages of the disease. In the present study, we address the question of whether application of a lentiviral vector expressing the Rpe65 mouse cDNA prevents cone degeneration and restores cone function in Rpe65 knockout mice. Methods and Findings Subretinal injection of the vector in Rpe65-deficient mice led to sustained expression of Rpe65 in the retinal pigment epithelium. Electroretinogram recordings showed that Rpe65 gene transfer restored retinal function to a near-normal pattern. We performed histological analyses using cone-specific markers and demonstrated that Rpe65 gene transfer completely prevented cone degeneration until at least four months, an age at which almost all cones have degenerated in the untreated Rpe65-deficient mouse. We established an algorithm that allows prediction of the cone-rescue area as a function of transgene expression, which should be a useful tool for future clinical trials. Finally, in mice deficient for both RPE65 and rod transducin, Rpe65 gene transfer restored cone function when applied at an early stage of the disease. Conclusions By demonstrating that lentivirus-mediated Rpe65 gene transfer protects and restores the function of cones in the Rpe65−/− mouse, this study reinforces the therapeutic value of gene therapy

  2. Hygroscopic motions of fossil conifer cones

    PubMed Central

    Poppinga, Simon; Nestle, Nikolaus; Šandor, Andrea; Reible, Bruno; Masselter, Tom; Bruchmann, Bernd; Speck, Thomas

    2017-01-01

    Conifer cones represent natural, woody compliant structures which move their scales as passive responses to changes in environmental humidity. Here we report on water-driven opening and closing motions in coalified conifer cones from the Eemian Interglacial (approx. 126,000–113,000 years BP) and from the Middle Miocene (approx. 16.5 to 11.5 million years BP). These cones represent by far the oldest documented evidence of plant parts showing full functionality of such passive hydraulically actuated motion. The functional resilience of these structures is far beyond the biological purpose of seed dispersal and protection and is because of a low level of mineralization of the fossils. Our analysis emphasizes the functional-morphological integrity of these biological compliant mechanisms which, in addition to their biological fascination, are potentially also role models for resilient and maintenance-free biomimetic applications (e.g., adaptive and autonomously moving structures including passive hydraulic actuators). PMID:28074936

  3. Optimization over Multi-order Cones

    DTIC Science & Technology

    2011-02-01

    Department of Mathematics Technical Report 2011-1 Optimization over multi-order cones Baha ’ M. Alzalg and K. A. Ariyawansa February 2011 Postal...Prescribed by ANSI Std Z39-18 Optimization over multi-order cones Baha M. Alzalg∗ and K. A. Ariyawansa† Abstract In this paper we propose multi-order cone...that x ∈ Qnp , and x 〈n〉 〈p〉 y to mean that x− y 〈n〉 〈p〉 0. Given 1 ≤ pi ≤ ∞ for i = 1, 2, · · · , r. Let Q 〈n1,n2,··· ,nr〉 〈p1,p2,··· ,pr〉 := Qn1p1

  4. Hygroscopic motions of fossil conifer cones.

    PubMed

    Poppinga, Simon; Nestle, Nikolaus; Šandor, Andrea; Reible, Bruno; Masselter, Tom; Bruchmann, Bernd; Speck, Thomas

    2017-01-11

    Conifer cones represent natural, woody compliant structures which move their scales as passive responses to changes in environmental humidity. Here we report on water-driven opening and closing motions in coalified conifer cones from the Eemian Interglacial (approx. 126,000-113,000 years BP) and from the Middle Miocene (approx. 16.5 to 11.5 million years BP). These cones represent by far the oldest documented evidence of plant parts showing full functionality of such passive hydraulically actuated motion. The functional resilience of these structures is far beyond the biological purpose of seed dispersal and protection and is because of a low level of mineralization of the fossils. Our analysis emphasizes the functional-morphological integrity of these biological compliant mechanisms which, in addition to their biological fascination, are potentially also role models for resilient and maintenance-free biomimetic applications (e.g., adaptive and autonomously moving structures including passive hydraulic actuators).

  5. Hygroscopic motions of fossil conifer cones

    NASA Astrophysics Data System (ADS)

    Poppinga, Simon; Nestle, Nikolaus; Šandor, Andrea; Reible, Bruno; Masselter, Tom; Bruchmann, Bernd; Speck, Thomas

    2017-01-01

    Conifer cones represent natural, woody compliant structures which move their scales as passive responses to changes in environmental humidity. Here we report on water-driven opening and closing motions in coalified conifer cones from the Eemian Interglacial (approx. 126,000-113,000 years BP) and from the Middle Miocene (approx. 16.5 to 11.5 million years BP). These cones represent by far the oldest documented evidence of plant parts showing full functionality of such passive hydraulically actuated motion. The functional resilience of these structures is far beyond the biological purpose of seed dispersal and protection and is because of a low level of mineralization of the fossils. Our analysis emphasizes the functional-morphological integrity of these biological compliant mechanisms which, in addition to their biological fascination, are potentially also role models for resilient and maintenance-free biomimetic applications (e.g., adaptive and autonomously moving structures including passive hydraulic actuators).

  6. Tilted cone beam VCT reconstruction algorithm

    NASA Astrophysics Data System (ADS)

    Hsieh, Jiang; Tang, Xiangyang

    2005-04-01

    Reconstruction algorithms for volumetric CT have been the focus of many studies. Several exact and approximate reconstruction algorithms have been proposed for step-and-shoot and helical scanning trajectories to combat cone beam related artifacts. In this paper, we present a closed form cone beam reconstruction formula for tilted gantry data acquisition. Although several algorithms were proposed to compensate for errors induced by the gantry tilt, none of the algorithms addresses the case in which the cone beam geometry is first rebinned to a set of parallel beams prior to the filtered backprojection. Because of the rebinning process, the amount of iso-center adjustment depends not only on the projection angle and tilt angle, but also on the reconstructed pixel location. The proposed algorithm has been tested extensively on both 16 and 64 slice VCT with phantoms and clinical data. The efficacy of the algorithm is clearly demonstrated by the experiments.

  7. Assessing mechanical properties from cone indentation hardness

    NASA Astrophysics Data System (ADS)

    Dicarlo, Anthony Albert

    This dissertation investigates methods for assessing the mechanical properties of materials using hardness values obtained from cone indentations. A broad range of isotropic metallic materials was simulated using finite element analysis. In particular, the elastic and plastic bulk properties, which define the stress-strain behavior of materials that exhibit power law hardening, are studied. Other investigators have found that the Young's modulus, E, can be determined from the unloading data of a cone indentation. Therefore, the remaining properties of interest, in this study, are the yield strength, Y, and the work hardening exponent, n. Atkins and Tabor have conducted pioneering work in the area of determining the stress-strain behavior of a metallic material from cone indentation experiments. This work has been re-visited in this study using computational models implementing an expanded range of mechanical properties. Consequently, discrepancies in this prediction method were uncovered when the mechanical properties were outside of the original range studied. As a result, two new prediction methods have been developed using the data collected from the finite element simulations in conjunction with a regression technique. The first method correlates the non-dimensional hardness values, H/E, collected from five cone indentations to the non-dimensional mechanical properties, Y/E and n. The second method is similar in principle, but uses two hardness values as opposed to five. The yield strength can be estimated with a priori knowledge of E. Both of these methods are compared to the method developed by Atkins and Tabor. Although the majority of the work mentioned is focused on the macro-scale, bulk mechanical properties, there is some investigation of meso-scale cone indentations. At the meso-scale, the number of geometric dislocations is significant enough to noticeably increase the strength of a material. This length scale effect is studied for various angled cone

  8. Cloning and functional characterization of salamander rod and cone arrestins.

    PubMed

    Smith, W C; Gurevich, E V; Dugger, D R; Vishnivetskiy, S A; Shelamer, C L; McDowell, J H; Gurevich, V V

    2000-08-01

    To clone, localize, and determine functional binding characteristics of rod and cone arrestins from the retina of the tiger salamander (Ambystoma tigrinum). Two arrestins from salamander retina were cloned on the basis of their homology to known arrestins from other species. The expression pattern of these arrestins (SalArr1 and SalArr2) in the retina was determined by immunocytochemistry and in situ hybridization. SalArr1 and SalArr2 were expressed and functionally characterized. Both immunocytochemistry and in situ hybridization show that SalArr1 and SalArr2 localized specifically to rod and cone photoreceptors, respectively. SalArr1 demonstrated a characteristic high selectivity for light-activated phosphorylated rhodopsin (P-Rh*) and significant species selectivity, binding preferentially to amphibian rhodopsin over bovine rhodopsin. Mutant constitutively active forms of SalArr1 demonstrated a 2- to 4-fold increase in P-Rh* binding (compared with wild-type protein) and an even more dramatic (up to 25-fold) increase in binding to unphosphorylated Rh* and dark P-Rh. Constitutively active SalArr1 mutants also showed a reduced specificity for amphibian rhodopsin. The ability of Escherichia coli-expressed SalArr1, SalArr2, and an SalArr1-3A (L369A,V370A,F371A) mutant to bind to frog Rh* and P-Rh* and to compete with tritiated SalArr1 for amphibian P-Rh* was compared. SalArr1 and its mutant form bound to amphibian P-Rh* with high affinity (Ki = 179 and 74 nM, respectively), whereas the affinity of SalArr2 for P-Rh* was substantially lower (Ki = 9.1 microM). SalArr1 and SalArr2 are salamander rod and cone arrestins, respectively. Crucial regulatory elements in SalArr1 are conserved and play functional roles similar to those of their counterparts in bovine rod arrestin. Rod and cone arrestins are relatively specific for their respective receptors.

  9. Understanding Cone Photoreceptor Cell Death in Achromatopsia.

    PubMed

    Carvalho, Livia S; Vandenberghe, Luk H

    2016-01-01

    Colour vision is only achieved in the presence of healthy and functional cone photoreceptors found in the retina. It is an essential component of human vision and usually the first complaint patients undergoing vision degeneration have is the loss of daylight colour vision. Therefore, an understanding of the biology and basic mechanisms behind cone death under the degenerative state of retinal dystrophies and how the activation of the apoptotic pathway is triggered will provide valuable knowledge. It will also have broader applications for a spectrum of visual disorders and will be critical for future advances in translational research.

  10. Tantalum Cones in Revision Total Knee Arthroplasty.

    PubMed

    Kim, Eric G; Patel, Nirav K; Chughtai, Morad; Elmallah, Randa D K; Delanois, Ronald E; Harwin, Steven F; Mont, Michael A

    2016-11-01

    The best strategy to address large bony defects in revision total knee arthroplasty has yet to be determined. The relatively recent development of porous tantalum cones and their use to address massive bone loss in knee arthroplasty has shown promising short- and intermediate-term results. The purpose of this review is to present the current literature on: (1) basic science of porous tantalum, (2) classification and treatment for bone loss, (3) clinical results, and (4) evolution of newer generation cones. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  11. Contributions of Rod and Cone Pathways to Retinal Direction Selectivity Through Development

    PubMed Central

    Rosa, Juliana M.; Morrie, Ryan D.; Baertsch, Hans C.

    2016-01-01

    Direction selectivity is a robust computation across a broad stimulus space that is mediated by activity of both rod and cone photoreceptors through the ON and OFF pathways. However, rods, S-cones, and M-cones activate the ON and OFF circuits via distinct pathways and the relative contribution of each to direction selectivity is unknown. Using a variety of stimulation paradigms, pharmacological agents, and knockout mice that lack rod transduction, we found that inputs from the ON pathway were critical for strong direction-selective (DS) tuning in the OFF pathway. For UV light stimulation, the ON pathway inputs to the OFF pathway originated with rod signaling, whereas for visible stimulation, the ON pathway inputs to the OFF pathway originated with both rod and M-cone signaling. Whole-cell voltage-clamp recordings revealed that blocking the ON pathway reduced directional tuning in the OFF pathway via a reduction in null-side inhibition, which is provided by OFF starburst amacrine cells (SACs). Consistent with this, our recordings from OFF SACs confirmed that signals originating in the ON pathway contribute to their excitation. Finally, we observed that, for UV stimulation, ON contributions to OFF DS tuning matured earlier than direct signaling via the OFF pathway. These data indicate that the retina uses multiple strategies for computing DS responses across different colors and stages of development. SIGNIFICANCE STATEMENT The retina uses parallel pathways to encode different features of the visual scene. In some cases, these distinct pathways converge on circuits that mediate a distinct computation. For example, rod and cone pathways enable direction-selective (DS) ganglion cells to encode motion over a wide range of light intensities. Here, we show that although direction selectivity is robust across light intensities, motion discrimination for OFF signals is dependent upon ON signaling. At eye opening, ON directional tuning is mature, whereas OFF DS tuning is

  12. Contributions of Rod and Cone Pathways to Retinal Direction Selectivity Through Development.

    PubMed

    Rosa, Juliana M; Morrie, Ryan D; Baertsch, Hans C; Feller, Marla B

    2016-09-14

    Direction selectivity is a robust computation across a broad stimulus space that is mediated by activity of both rod and cone photoreceptors through the ON and OFF pathways. However, rods, S-cones, and M-cones activate the ON and OFF circuits via distinct pathways and the relative contribution of each to direction selectivity is unknown. Using a variety of stimulation paradigms, pharmacological agents, and knockout mice that lack rod transduction, we found that inputs from the ON pathway were critical for strong direction-selective (DS) tuning in the OFF pathway. For UV light stimulation, the ON pathway inputs to the OFF pathway originated with rod signaling, whereas for visible stimulation, the ON pathway inputs to the OFF pathway originated with both rod and M-cone signaling. Whole-cell voltage-clamp recordings revealed that blocking the ON pathway reduced directional tuning in the OFF pathway via a reduction in null-side inhibition, which is provided by OFF starburst amacrine cells (SACs). Consistent with this, our recordings from OFF SACs confirmed that signals originating in the ON pathway contribute to their excitation. Finally, we observed that, for UV stimulation, ON contributions to OFF DS tuning matured earlier than direct signaling via the OFF pathway. These data indicate that the retina uses multiple strategies for computing DS responses across different colors and stages of development. The retina uses parallel pathways to encode different features of the visual scene. In some cases, these distinct pathways converge on circuits that mediate a distinct computation. For example, rod and cone pathways enable direction-selective (DS) ganglion cells to encode motion over a wide range of light intensities. Here, we show that although direction selectivity is robust across light intensities, motion discrimination for OFF signals is dependent upon ON signaling. At eye opening, ON directional tuning is mature, whereas OFF DS tuning is significantly reduced due

  13. 125. Moses H. Cone Memorial Park. View of carriage trail ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    125. Moses H. Cone Memorial Park. View of carriage trail and flat top mountain from cone cemetery. Looking north-northeast. - Blue Ridge Parkway, Between Shenandoah National Park & Great Smoky Mountains, Asheville, Buncombe County, NC

  14. The First Three Dimensional Digital Models of Shatter Cones

    NASA Astrophysics Data System (ADS)

    Baratoux, D.; Bouley, S.; Reimold, W. U.; Baratoux, L.

    2014-09-01

    Shatter cones are used as a diagnostic evidence for impact, but model of formation is unclear. Geometrical parameters may offer critical tests. The first 3-D models of 30 shatter cones from 16 different impact structures are reported here.

  15. Shatter Cones Formed in a MEMIN Impact Cratering Experiment

    NASA Astrophysics Data System (ADS)

    Kenkmann, T.; Poelchau, M. H.; Trullenque, G.; Hoerth, T.; Schäfer, F.; Thoma, K.; Deutsch, A.

    2012-09-01

    Experimentally formed shatter cones help to constrain the physical boundary conditions required for their formation. We produced shatter cones in porous sandstone at 4.3 kJ shock loading. Their surfaces contain vesicular melt films.

  16. Basaltic Cone Suggests Constructional Origin of Some Guyots.

    PubMed

    Christensen, M N; Gilbert, C M

    1964-01-17

    A basaltic cinder cone was built beneath the waters of Mono Lake in Pleistocene time. This cone is now exposed. Its internal structure, external form, and petrography suggest that it was constructed with a flat top.

  17. Synaptic Transmission from Horizontal Cells to Cones Is Impaired by Loss of Connexin Hemichannels

    PubMed Central

    Klaassen, Lauw J.; Sun, Ziyi; Steijaert, Marvin N.; Bolte, Petra; Fahrenfort, Iris; Sjoerdsma, Trijntje; Klooster, Jan; Claassen, Yvonne; Shields, Colleen R.; Ten Eikelder, Huub M. M.; Janssen-Bienhold, Ulrike; Zoidl, Georg; McMahon, Douglas G.; Kamermans, Maarten

    2011-01-01

    In the vertebrate retina, horizontal cells generate the inhibitory surround of bipolar cells, an essential step in contrast enhancement. For the last decades, the mechanism involved in this inhibitory synaptic pathway has been a major controversy in retinal research. One hypothesis suggests that connexin hemichannels mediate this negative feedback signal; another suggests that feedback is mediated by protons. Mutant zebrafish were generated that lack connexin 55.5 hemichannels in horizontal cells. Whole cell voltage clamp recordings were made from isolated horizontal cells and cones in flat mount retinas. Light-induced feedback from horizontal cells to cones was reduced in mutants. A reduction of feedback was also found when horizontal cells were pharmacologically hyperpolarized but was absent when they were pharmacologically depolarized. Hemichannel currents in isolated horizontal cells showed a similar behavior. The hyperpolarization-induced hemichannel current was strongly reduced in the mutants while the depolarization-induced hemichannel current was not. Intracellular recordings were made from horizontal cells. Consistent with impaired feedback in the mutant, spectral opponent responses in horizontal cells were diminished in these animals. A behavioral assay revealed a lower contrast-sensitivity, illustrating the role of the horizontal cell to cone feedback pathway in contrast enhancement. Model simulations showed that the observed modifications of feedback can be accounted for by an ephaptic mechanism. A model for feedback, in which the number of connexin hemichannels is reduced to about 40%, fully predicts the specific asymmetric modification of feedback. To our knowledge, this is the first successful genetic interference in the feedback pathway from horizontal cells to cones. It provides direct evidence for an unconventional role of connexin hemichannels in the inhibitory synapse between horizontal cells and cones. This is an important step in resolving a

  18. Interferometry of a reflective axicon surface with a small cone angle using an optical inner surface

    NASA Astrophysics Data System (ADS)

    Gao, Huimin; Zhang, Xiaodong; Fang, Fengzhou

    2017-09-01

    Reflective axicons, widely used in optical alignment and Bessel-Gauss beam generation, require a highly accurate cone angle and surface metrology. However, current methods focus on the cone angle measurement and it is still difficult to measure the surface of a reflective axicon with a small cone angle. An interferometer measurement method using an optical inner surface is proposed to obtain the surface and cone angle simultaneously. The optical axis of the axicon and the optical inner surface should align together and be parallel to the beam light from the interferometer. The interference fringe would be obtained by the optical system consisting of the axicon and the optical inner surface. The theoretical model is established and analyzed through ray tracing theory, and is verified by optical simulation software. Fabrication errors in the axicon and the inner surface, and misalignment of the measurement setup are investigated systematically and separated in the measurement process. In the experiments, the reflective axicon with a cone angle of about 90° was measured by the proposed method, the results of which show good agreement with a stylus profiler (Taylor-Hobson PGI 3D) in cone angle trend and generatrix error. Experimental results prove the feasibility of the proposed method. This economical and effective method can be widely used with all types of reflective axicons, and it can obtain the surface error map of the axicon as well as the inner cylinder at the same time. The uncertainty and resolution of the proposed method is based on the performance of the interferometer. The uncertainty of alignment angle errors is less than 10-10 rad; the lateral resolution is 53.8 µm.

  19. Actions of EGTA and high calcium on the cones in the turtle retina.

    PubMed Central

    Bertrand, D; Fuortes, M G; Pochobradsky, J

    1978-01-01

    1. The effects of Ca2+ on the activity of retinal cones were investigated by recording intracellular responses from turtle retinae perfused with solutions containing different Ca2+ concentrations. 2. Lowering extracellular Ca2+ concentration with EGTA increased membrane conductance and evoked depolarization in darkness. 3. Responses to bright lights were increased by EGTA by an amount equal to the depolarization in darkness; responses to dim lights instead were usually reduced. In addition EGTA modified the time course of responses to flashes. These changes were especially evident during the later phases of the response. 4. A steady light applied during EGTA perfusion can restore the original membrane potential. The kinetics of responses in these conditions, however, differ profoundly from those prevailing Ca2+ concentrations evoked hyperpolarization of the cones and decreased the amplitude of their responses to bright lights. The time course of responses to flashes was not appreciably modified by high Ca2+. 6. A steady light which hyperpolarizes the cone membrane by the same amount as high Ca2+ has an equal effect on the amplitude of responses to bright flashes but has an entirely different action on response kinetics and on the amplitude of responses to dimmer flashes. 7. The effects of EGTA on resting potential, conductance and response amplitudecan be interpreted assuming that the drug opens channels which are normally closed by Ca2+ in darkness. Conversely, the changes caused by high Ca2+ suggest that raising the concentration of outside Ca2+ reduces the number of light-sensitive channels open in darkness. 8. The observation that Ca2+ and light have different effects on kinetics and sensitivities is difficult to reconcile with the hypothesis that Ca2+ is the substance liberated by light to cause photoresponses. Images Fig. 1 PMID:416204

  20. Successful gene therapy in the RPGRIP1-deficient dog: a large model of cone-rod dystrophy.

    PubMed

    Lhériteau, Elsa; Petit, Lolita; Weber, Michel; Le Meur, Guylène; Deschamps, Jack-Yves; Libeau, Lyse; Mendes-Madeira, Alexandra; Guihal, Caroline; François, Achille; Guyon, Richard; Provost, Nathalie; Lemoine, Françoise; Papal, Samantha; El-Amraoui, Aziz; Colle, Marie-Anne; Moullier, Philippe; Rolling, Fabienne

    2014-02-01

    For the development of new therapies, proof-of-concept studies in large animal models that share clinical features with their human counterparts represent a pivotal step. For inherited retinal dystrophies primarily involving photoreceptor cells, the efficacy of gene therapy has been demonstrated in canine models of stationary cone dystrophies and progressive rod-cone dystrophies but not in large models of progressive cone-rod dystrophies, another important cause of blindness. To address the last issue, we evaluated gene therapy in the retinitis pigmentosa GTPase regulator interacting protein 1 (RPGRIP1)-deficient dog, a model exhibiting a severe cone-rod dystrophy similar to that seen in humans. Subretinal injection of AAV5 (n = 5) or AAV8 (n = 2) encoding the canine Rpgrip1 improved photoreceptor survival in transduced areas of treated retinas. Cone function was significantly and stably rescued in all treated eyes (18-72% of those recorded in normal eyes) up to 24 months postinjection. Rod function was also preserved (22-29% of baseline function) in four of the five treated dogs up to 24 months postinjection. No detectable rod function remained in untreated contralateral eyes. More importantly, treatment preserved bright- and dim-light vision. Efficacy of gene therapy in this large animal model of cone-rod dystrophy provides great promise for human treatment.

  1. Cone-like rhodopsin expressed in the all-cone retina of the colubrid pine snake as a potential adaptation to diurnality.

    PubMed

    Bhattacharyya, Nihar; Darren, Benedict; Schott, Ryan K; Tropepe, Vincent; Chang, Belinda S W

    2017-07-01

    Colubridae is the largest and most diverse family of snakes, with visual systems that reflect this diversity, encompassing a variety of retinal photoreceptor organizations. The transmutation theory proposed by Walls postulates that photoreceptors could evolutionarily transition between cell types in squamates, but few studies have tested this theory. Recently, evidence for transmutation and rod-like machinery in an all-cone retina has been identified in a diurnal garter snake (Thamnophis), and it appears that the rhodopsin gene at least may be widespread among colubrid snakes. However, functional evidence supporting transmutation beyond the existence of the rhodopsin gene remains rare. We examined the all-cone retina of another colubrid, Pituophis melanoleucus, thought to be more secretive/burrowing than Thamnophis We found that P. melanoleucus expresses two cone opsins (SWS1, LWS) and rhodopsin (RH1) within the eye. Immunohistochemistry localized rhodopsin to the outer segment of photoreceptors in the all-cone retina of the snake and all opsin genes produced functional visual pigments when expressed in vitro Consistent with other studies, we found that P. melanoleucus rhodopsin is extremely blue-shifted. Surprisingly, P. melanoleucus rhodopsin reacted with hydroxylamine, a typical cone opsin characteristic. These results support the idea that the rhodopsin-containing photoreceptors of P. melanoleucus are the products of evolutionary transmutation from rod ancestors, and suggest that this phenomenon may be widespread in colubrid snakes. We hypothesize that transmutation may be an adaptation for diurnal, brighter-light vision, which could result in increased spectral sensitivity and chromatic discrimination with the potential for colour vision. © 2017. Published by The Company of Biologists Ltd.

  2. Restoration of cone vision in a mouse model of achromatopsia.

    PubMed

    Alexander, John J; Umino, Yumiko; Everhart, Drew; Chang, Bo; Min, Seok H; Li, Qiuhong; Timmers, Adrian M; Hawes, Norman L; Pang, Ji-Jing; Barlow, Robert B; Hauswirth, William W

    2007-06-01

    Loss of cone function in the central retina is a pivotal event in the development of severe vision impairment for many prevalent blinding diseases. Complete achromatopsia is a genetic defect resulting in cone vision loss in 1 in 30,000 individuals. Using adeno-associated virus (AAV) gene therapy, we show that it is possible to target cones and rescue both the cone-mediated electroretinogram response and visual acuity in the Gnat2 ( cpfl3 ) mouse model of achromatopsia.

  3. Slow Cone Reflectance Changes during Bleaching Determined by Adaptive Optics Scanning Laser Ophthalmoscope in Living Human Eyes.

    PubMed

    Hirota, Masakazu; Miyagawa, Suguru; Kanda, Hiroyuki; Endo, Takao; Lohmann, Tibor Karl; Miyoshi, Tomomitsu; Morimoto, Takeshi; Fujikado, Takashi

    2015-01-01

    To investigate the changes in the reflectance of human cone photoreceptors by an adaptive optics scanning laser ophthalmoscope (AO-SLO) during photobleaching. A custom-built AO-SLO with an observation light of 840-nm was used to measure the cone densities and the reflectance changes during bleaching by 630 nm red light emitting diodes. Measurements were made at 1° and 3° temporal to the fovea within an area of 1° × 1° in 8 eyes of 8 normal subjects. After dark-adaptation, images of the cone mosaics were recorded continuously for 5-min before, 5-min during, and after 5-min of light stimulation with a sampling rate of 5-Hz. The first positive peak (P1) was observed at 72.2 ± 15.0-s and a second positive peak (P2) at 257.5 ± 34.5-s at 1°. The increase of the reflectance of P1 was significantly larger at 1° (34.4 ± 13.9%) than at 3° (26.0 ± 10.5%; P = 0.03, Wilcoxon's signed rank test). The average cone density at 1° (51123.13 ± 1401.23 cells/mm2) was significantly larger than that at 3° (30876.13 ± 1459.28 cells/mm2; P <0.001, Wilcoxon's signed rank test). The changes in the reflectance of the cones during bleaching by red light had two peaks. The two peaks may be caused by regeneration of cone photopigment during bleaching.

  4. Human photoreceptor cone density measured with adaptive optics technology (rtx1 device) in healthy eyes: Standardization of measurements.

    PubMed

    Zaleska-Żmijewska, Anna; Wawrzyniak, Zbigniew M; Ulińska, Magdalena; Szaflik, Jerzy; Dąbrowska, Anna; Szaflik, Jacek P

    2017-06-01

    The anatomic structures of the anterior segment of the eye enable correct reception of stimuli by the retina, which contains receptors that receive light impulses and transmit them to the visual cortex. The aim of this study was to assess the effect of the size of the sampling window in an adaptive optics (AO) flood-illumination retinal camera (rtx1) on cone density measurements in the eyes of healthy individuals and to investigate the differences in cone density and spacing in different quadrants of the retina. Thirty-three subjects with no ophthalmic or systemic disease underwent a detailed ophthalmologic examination. Photographs of retinal fragments 3 degrees from the fovea were taken using the rtx1 AO retinal camera. We used sampling windows with 3 sizes (50 × 50, 100 × 100, and 250 × 250 μm). Cone density, spacing, and shape were determined using AOdetect software. The median (interquartile range) cone density was 19,269 (4964) cones/mm. There were statistically significant differences between measurements taken with the 50/50 and 250/250-m windows. There were no significant differences in the cone spacing results between any of the windows examined, but the measurements differed according to location between the superior and temporal quadrants. The most common cone shape was hexagonal (47.6%) for all window sizes and locations. These findings may help in the development of a normative database for variation in cone density in healthy subjects and to allow the best window to be chosen for obtain the most correct values for eccentricity measurements of 3 degrees. In our study, the optimal sampling window was 100 × 100 μm.

  5. Mouse Ganglion-Cell Photoreceptors Are Driven by the Most Sensitive Rod Pathway and by Both Types of Cones

    PubMed Central

    Weng, Shijun; Estevez, Maureen E.; Berson, David M.

    2013-01-01

    Intrinsically photosensitive retinal ganglion cells (ipRGCs) are depolarized by light by two mechanisms: directly, through activation of their photopigment melanopsin; and indirectly through synaptic circuits driven by rods and cones. To learn more about the rod and cone circuits driving ipRGCs, we made multielectrode array (MEA) and patch-clamp recordings in wildtype and genetically modified mice. Rod-driven ON inputs to ipRGCs proved to be as sensitive as any reaching the conventional ganglion cells. These signals presumably pass in part through the primary rod pathway, involving rod bipolar cells and AII amacrine cells coupled to ON cone bipolar cells through gap junctions. Consistent with this interpretation, the sensitive rod ON input to ipRGCs was eliminated by pharmacological or genetic disruption of gap junctions, as previously reported for conventional ganglion cells. A presumptive cone input was also detectable as a brisk, synaptically mediated ON response that persisted after disruption of rod ON pathways. This was roughly three log units less sensitive than the rod input. Spectral analysis revealed that both types of cones, the M- and S-cones, contribute to this response and that both cone types drive ON responses. This contrasts with the blue-OFF, ye