Environmental context explains Levy and Brownian movement patterns of marine predators

An optimal search theory, the so-called Levy-flight foraging hypothesis(1), predicts that predators should adopt search strategies known as Levy flights where prey is sparse and distributed unpredictably, but that Brownian movement is sufficiently efficient for locating abundant prey(2-4). Empirical studies have generated controversy because the accuracy of statistical methods that have been used to identify Levy behaviour has recently been questioned(5,6). Consequently, whether foragers exhibit Levy flights in the wild remains unclear. Crucially, moreover, it has not been tested whether observed movement patterns across natural landscapes having different expected resource distributions conform to the theory's central predictions. Here we use maximum-likelihood methods to test for Levy patterns in relation to environmental gradients in the largest animal movement data set assembled for this purpose. Strong support was found for Levy search patterns across 14 species of open-ocean predatory fish (sharks, tuna, billfish and ocean sunfish), with some individuals switching between Levy and Brownian movement as they traversed different habitat types. We tested the spatial occurrence of these two principal patterns and found Levy behaviour to be associated with less productive waters (sparser prey) and Brownian movements to be associated with productive shelf or convergence-front habitats (abundant prey). These results are consistent with the Levy-flight foraging hypothesis(1,7), supporting the contention(8,9) that organism search strategies naturally evolved in such a way that they exploit optimal Levy patterns.

Recueil de pièces historiques et littéraires.

Contient : 1 Traité d'Arras, entre Charles VII et Philippe le Bon, duc de Bourgogne. 21 septembre 1435 ; 2 Petit mémoire de ce qui fut résolu par Philippe le Bon, duc de Bourgogne, et Charles le Téméraire, comte de Charolais, sur le sort des villes de Dinan et de Liège. 25 août 1466 ; 3 « Ordonnances faictes en l'eschiquier de Normendie tenu à Rouen, au terme de Pasques, l'an 1463 » ; 4 Ratification faite à Paris, le 27 octobre 1465, par LOUIS XI, du traité conclu avec son frère Charles, duc de Guyenne, et autres seigneurs du royaume, qui avaient été cause de la ligue dite du Bien public. Cette ratification est suivie des noms des « trente six personnes ordonnées pour la cause dessus dite », et de la publication de ladite paix ; 5 Sommation faite par PHILIPPE LE BON, duc DE BOURGOGNE, aux Gantois de se remettre sous son obéissance, en acceptant les conditions qu'il leur avait fait proposer. « Donné en nostre host, le mardi XXIIIe jour de fevrier, l'an mil CCCCLIII » ; 6 Lettre de PHILIPPE LE BON, duc DE BOURGOGNE, à Louis XI. 25 juillet 1463 ; 7 Offres des Gantois à Philippe le Bon, « à fin de paix et avoir sa bonne grace ». 30 juillet 1453 ; 8 Version en prose du roman des Sept Sages ; 9 Histoire de Barlaam et Joasaph ; 10 Le Miroir de l'âme ; 11 « La Vie de saint Anthoine de Pade » ; 12 « C'est la complainte des trois estaz de France de la mort du roy Charles dernier passé[Charles VII], avec ses epitaphes » ; 13 « Les Fainctes du monde » ; 14 « Significacions moult notables et beaulx de la messe » ; 15 Arrêt du parlement de Paris, prononcé, le 19 décembre 1475, contre Louis de Luxembourg, comte de Saint-Pol ; 16 L'Échelle de charité ; 17 Trépassement Notre-Dame ; 18 « Incipit compassio beate Marie circa crucem, sicut ab ipsa revelatum fuit beato Augustino » ; 19 Conte dévot en quatrains monorimes d'une « dame... de Boullenoiz et d'un chevalier, qui allèrent en pèlerinage à Saint-Jacques de Galice ; 20 « Exemologesis, seu confessio generalis peccatorum valde pia, cum aliquot devotis orationibus » ; 21 Poésies latines en l'honneur : 1° de la sainte Vierge : a. « Laudes et oratio de beata virgine Maria. Salve, sancta mater Dei, radix vite, robur spei... » (fol. 230-232) ; b. « O miserum, cur valeo, cur non amore langueo... » (fol. 232 v°) ; c. « Oratio ad beatam virginem Mariam. O predulcis creatura, Majestatis scrinium... » (fol. 232 v°-233 v°) ; 2° du saint Sacrement : a. « Laudes et oratio de sacramento altaris. Ave, vivens hostia, veritas et vita... » (fol. 233 v° -234 v° ) ; b. « Oratio ad sacramentum altaris. Ad te suspirat anxius pauperculus inutilis... » (fol. 235) ; 22 Le Jeu des échecs moralisés ; 23 Histoire d'Hérode, de Judas et de Pilate ; 24 « Informacion envoyée par Francisco de Trane » (Traona) au « cardinal d'Avignon », Alain de Coëtivy, sur la prise de Constantinople par les Turcs, en 1453 ; 25 Lettre des Vénitiens au pape Nicolas V, faisant mention de la prise de Constantinople par les Turcs. 30 juin 1453 ; 26 Lettres « envoyées par le Turc à nostre saint père le pape... anno Machometi VIIIC.XL... », à l'occasion de la croisade que l'on faisait publier contre les Turcs. En latin ; 27 Lettres patentes de LOUIS XI, déchargeant les habitants de Rouen de l'impôt de 12 deniers par livre sur les marchandises déclarées, 29 août 1465, avec la vérification par les généraux et conseillers des finances, 14 septembre 1465 ; 28 Articles présentés par les ambassadeurs de Charles VII, roi de France, assemblés à Arras, aux ambassadeurs de Henri VI, roi d'Angleterre, et Philippe le Bon, duc de Bourgogne, pour parvenir à la paix générale, 7 septembre 1435, avec les lettres de pouvoir données par CHARLES VII à ses ambassadeurs, 6 juillet 1435 ; 29 Traité d'Arras. 20 septembre 1435

A new algorithm for OFDM joint data detection and phase noise cancellation

This paper proposes a new iterative algorithm for OFDM joint data detection and phase noise (PHN) cancellation based on minimum mean square prediction error. We particularly highlight the problem of "overfitting" such that the iterative approach may converge to a trivial solution. Although it is essential for this joint approach, the overfitting problem was relatively less studied in existing algorithms. In this paper, specifically, we apply a hard decision procedure at every iterative step to overcome the overfitting. Moreover, compared with existing algorithms, a more accurate Pade approximation is used to represent the phase noise, and finally a more robust and compact fast process based on Givens rotation is proposed to reduce the complexity to a practical level. Numerical simulations are also given to verify the proposed algorithm.

An on-line algorithm of uncertain time delay estimation in a continuous system

In this paper, we present an on-line estimation algorithm for an uncertain time delay in a continuous system based on the observational input-output data, subject to observational noise. The first order Pade approximation is used to approximate the time delay. At each time step, the algorithm combines the well known Kalman filter algorithm and the recursive instrumental variable least squares (RIVLS) algorithm in cascade form. The instrumental variable least squares algorithm is used in order to achieve the consistency of the delay parameter estimate, since an error-in-the-variable model is involved. An illustrative example is utilized to demonstrate the efficacy of the proposed approach.

OFDM joint data detection and phase noise cancellation based on minimum mean square prediction error

This paper proposes a new iterative algorithm for orthogonal frequency division multiplexing (OFDM) joint data detection and phase noise (PHN) cancellation based on minimum mean square prediction error. We particularly highlight the relatively less studied problem of "overfitting" such that the iterative approach may converge to a trivial solution. Specifically, we apply a hard-decision procedure at every iterative step to overcome the overfitting. Moreover, compared with existing algorithms, a more accurate Pade approximation is used to represent the PHN, and finally a more robust and compact fast process based on Givens rotation is proposed to reduce the complexity to a practical level. Numerical Simulations are also given to verify the proposed algorithm. (C) 2008 Elsevier B.V. All rights reserved.

Bose systems in spatially random or time-varying potentials

Bose systems, subject to the action of external random potentials, are considered. For describing the system properties, under the action of spatially random potentials of arbitrary strength, the stochastic mean-field approximation is employed. When the strength of disorder increases, the extended Bose-Einstein condensate fragments into spatially disconnected regions, forming a granular condensate. Increasing the strength of disorder even more transforms the granular condensate into the normal glass. The influence of time-dependent external potentials is also discussed. Fastly varying temporal potentials, to some extent, imitate the action of spatially random potentials. In particular, strong time-alternating potential can induce the appearance of a nonequilibrium granular condensate.

A Higher order and stable method for the numerical integration of Random Differential Equations

Trabalho apresentado no Congresso Nacional de Matemática Aplicada à Indústria, 18 a 21 de novembro de 2014, Caldas Novas - Goiás

Application of a meshless method in electromagnetics

An improved meshless method is presented with an emphasis on the detailed description of this new computational technique and its numerical implementations by investigating the usefulness of a commonly neglected parameter in this paper. Two approaches to enforce essential boundary conditions are also thoroughly investigated. Numerical tests on a mathematical function is carried out as a means of validating the proposed method. It will be seen that the proposed method is more robust than the conventional ones. Applications in solving electromagnetic problems are also presented.

LARGE-ORDER PERTURBATION EXPANSIONS FOR THE CHARGED HARMONIC-OSCILLATOR

The charged oscillator, defined by the Hamiltonian H = -d2/dr2+ r2 + lambda/r in the domain [0, infinity], is a particular case of the family of spiked oscillators, which does not behave as a supersingular Hamiltonian. This problem is analysed around the three regions lambda --> infinity, lambda --> 0 and lambda --> -infinity by using Rayleigh-Ritz large-order perturbative expansions. A path is found to connect the large lambda regions with the small lambda region by means of the renormalization of the series expansions in lambda. Finally, the Riccati-Pade method is used to construct an implicit expansion around lambda --> 0 which extends to very large values of Absolute value of lambda.

The application of interpolating MLS approximations to the analysis of MHD flows

The element-free Galerkin method (EFGM) is a very attractive technique for solutions of partial differential equations, since it makes use of nodal point configurations which do not require a mesh. Therefore, it differs from FEM-like approaches by avoiding the need of meshing, a very demanding task for complicated geometry problems. However, the imposition of boundary conditions is not straightforward, since the EFGM is based on moving-least-squares (MLS) approximations which are not necessarily interpolants. This feature requires, for instance, the introduction of modified functionals with additional unknown parameters such as Lagrange multipliers, a serious drawback which leads to poor conditionings of the matrix equations. In this paper, an interpolatory formulation for MLS approximants is presented: it allows the direct introduction of boundary conditions, reducing the processing time and improving the condition numbers. The formulation is applied to the study of two-dimensional magnetohydrodynamic flow problems, and the computed results confirm the accuracy and correctness of the proposed formulation. (C) 2002 Elsevier B.V. All rights reserved.

Some Extensions of M-Fractions Related to Strong Stieltjes Distributions

The purpose of this paper is to show the symmetric relations that appear between the coefficients of some even and odd extensions of the M-fractions related to a certain kind of symmetric strong Stieltjes distribution.

On the two point Padé table for a distribution

Some additional recurrence relations for the denominator polynomials of two point Padé approximants are derived. An example in which the coefficients of one of the two series, from which the Padé approximants are derived, are moments of a distribution is considered. For this example, properties of the denominator polynomials, and their zeros, are described.

Meromorphic continuation of functions and arbitrary distribution of interpolation points

We characterize the region of meromorphic continuation of an analytic function ff in terms of the geometric rate of convergence on a compact set of sequences of multi-point rational interpolants of ff. The rational approximants have a bounded number of poles and the distribution of interpolation points is arbitrary.

Método da propagação de feixe de ângulo largo para análise de guias de ondas ópticos não-lineares

Este trabalho propõe uma extensão do método de propagação de feixe (BPM - Beam Propagation Method) para a análise de guias de ondas ópticos e acopladores baseados em materiais não-lineares do tipo Kerr. Este método se destina à investigação de estruturas onde a utilização da equação escalar de Helmholtz (EEH) em seu limite paraxial não mais se aplica. Os métodos desenvolvidos para este fim são denominados na literatura como métodos de propagação de feixe de ângulo largo. O formalismo aqui desenvolvido é baseado na técnica das diferenças finitas e nos esquemas de Crank-Nicholson (CN) e Douglas generalizado (GD). Estes esquemas apresentam como característica o fato de apresentarem um erro de truncamento em relação ao passo de discretização transversal, Δx, proporcional a O(Δx2) para o primeiro e O(Δx4). A convergência do método em ambos esquemas é otimizada pela utilização de um algoritmo interativo para a correção do campo no meio não-linear. O formalismo de ângulo largo é obtido pela expansão da EEH para os esquemas CN e GD em termos de polinômios aproximantes de Padé de ordem (1,0) e (1,1) para CN e GD, e (2,2) e (3,3) para CN. Os aproximantes de ordem superior a (1,1) apresentam sérios problemas de estabilidade. Este problema é eliminado pela rotação dos aproximantes no plano complexo. Duas condições de contorno nos extremos da janela computacional são também investigadas: 1) (TBC - Transparent Boundary Condition) e 2) condição de contorno absorvente (TAB - Transparent Absorbing Boundary). Estas condições de contorno possuem a facilidade de evitar que reflexões indesejáveis sejam transmitidas para dentro da janela computacional. Um estudo comparativo da influência destas condições de contorno na solução de guias de ondas ópticos não-lineares é também abordada neste trabalho.

Semantics of query-driven communication of exact values

We address the question of how to communicate among distributed processes valuessuch as real numbers, continuous functions and geometrical solids with arbitrary precision, yet efficiently. We extend the established concept of lazy communication using streams of approximants by introducing explicit queries. We formalise this approach using protocols of a query-answer nature. Such protocols enable processes to provide valid approximations with certain accuracy and focusing on certain locality as demanded by the receiving processes through queries. A lattice-theoretic denotational semantics of channel and process behaviour is developed. Thequery space is modelled as a continuous lattice in which the top element denotes the query demanding all the information, whereas other elements denote queries demanding partial and/or local information. Answers are interpreted as elements of lattices constructed over suitable domains of approximations to the exact objects. An unanswered query is treated as an error anddenoted using the top element. The major novel characteristic of our semantic model is that it reflects the dependency of answerson queries. This enables the definition and analysis of an appropriate concept of convergence rate, by assigning an effort indicator to each query and a measure of information content to eachanswer. Thus we capture not only what function a process computes, but also how a process transforms the convergence rates from its inputs to its outputs. In future work these indicatorscan be used to capture further computational complexity measures. A robust prototype implementation of our model is available.