Random Primordial Magnetic Fields and the Gas Content of Dark Matter Halos

We recently predicted the existence of random primordial magnetic fields (RPMF) in the form of randomly oriented cells with dipole-like structure with a cell size $L_0$ and an average magnetic field $B_0$. Here we investigate models for primordial magnetic field with a similar web-like structure, and other geometries, differing perhaps in $L_0$ and $B_0$. The effect of RPMF on the formation of the first galaxies is investigated. The filtering mass, $M_F$, is the halo mass below which baryon accretion is severely depressed. We show that these RPMF could influence the formation of galaxies by altering the filtering mass and the baryon gas fraction of a halo, $f_g$. The effect is particularly strong in small galaxies. We find, for example, for a comoving B_0=0.1\muG, and a reionization epoch that starts at $z_s=11$ and ends at $z_e=8$, for $L_0=100\,\text{pc}$ at $z=12$, the $f_g$ becomes severely depressed for M<10^7\msun, whereas for $B_0=0$ the $f_g$ becomes severely depressed only for much smaller masses, M<10^5\msun. We suggest that the observation of $M_F$ and $f_g$ at high redshifts can give information on the intensity and structure of primordial magnetic fields.Comment: 7 pages, 10 figures, accepted for publication in MNRAS (several improvements after suggestions of the referee

Structural diversity of fruits: conceptual reflexions and taxonomic implications / Diversidade estrutural de frutos: reflexões conceituais e implicações taxonômicas

Fruit either originates solely from the ovary or ovary and other floral parts and inflorescence. Besides the ovary itself, the pedicle, bracteoles, receptacle, hypanthium, sepals, petals and inflorescence axis are included in the fruit development. Analysis was made in embedded historesin/paraffin material and sectioned in microtome. In the fruit ontogeny the pericarp either may be non-multiplicative or multiplicative. In the first case, the ovary wall differentiates in pericarp without the installation of meristem. Adaxial, middle or abaxial meristems can be installed in the multiplicative pericarp fruits from the periclinal cell divisions that occur in both the epidermis and the ovary mesophyll. Separation tissue takes place in the carpel margins and midrib in dehiscent fruits or it can remain as residual tissue in indehiscent fruits. Fruit classification is complex, and it may show divergence in nomenclature among fruit specialists. Structural fruit ontogeny can be a useful tool for its classification. Fruit structure has been used as diagnostic character of species, genera and tribes of angiosperms. Hypothesis about fruit evolution indicates that apocarpic fruit with follicles can be a basic evolutionary condition, at least among the sensu lato dicots. The Araucaria angustifolia pine seed is considered here as a fruit with protocarps/spermatocarps

Entre o Planejamento Estratégico Formal e Informal: um Estudo de Caso Exploratório sobre a Prática de Estratégia nas Organizações

Most studies on strategy formation have a constitutive contingency element that defines variables through which one could sort organizations into a certain order to indicate what type of strategy formation is more suitable for each (e.g. Mintzberg & McHugh, 1985). This almost prescriptive ordinance concerning the content, process and practice of strategy in organizations can lead one to the perception that it is possible to determine the pattern of strategy of formation in organizations through the simple analysis of some predetermined variables. Guided by the strategy-as-practice approach (Jarzabkowski, 2005, 2008; Whittington, 1996, 2006), this paper explores the practice of strategic planning based on an exploratory single case study in a project-based organization, through which it was possible to identify change processes that shaped different stages of the strategic planning practice over the years with distinct characteristics regarding its (in)formality. These processes were analyzed using an approach inspired on the structuration theory (Giddens, 1984), indicating that the adequate level of strategic planning formalization should be defined by the structuration of practice in its social dynamic

Critérios de divisibilidades

TCC (graduação) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Curso de Matemática.A matemática é fascinante para muitas pessoas pelas oportunidades que oferece para a criação e a descoberta assim como pela sua utilidade. È continuo e rápido o seu crescimento no sentido de satisfazer tanto a curiosidade quanto às necessidades de aplicação. Os estudantes podem desenvolver processos sistemáticos para tratar problemas, sejam ou não, de rotina ou de soluções imediatamente determináveis . Para achar os fatores de um determinado número podemos sempre tentar, mas será muito mais fácil se pudermos dizer simplesmente olhando para o número se ele tem ou não um dado fator. Foi pensando em resolver este problema que resolvi fazer meu trabalho de conclusão de Curso. O objetivo deste trabalho é servir como um material de pesquisa para estudantes e alunos interessados em desvendar os mistérios da teoria dos números. A apresentação é feita de tal forma que a matéria pode ser rapidamente compreendida pelos leitores

Métodos de Maz'ia e Landweber para o problema de Cauchy elíptico

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Matemática Pura e Aplicada, Florianópolis, 2015.Nesta dissertação foi trabalhado o clássico exemplo de problema mal posto, o problema de Cauchy elíptico para o operador de Laplace sobre um conjunto ? ? R2 suficientemente regular, onde os dados de Cauchy são fornecidos apenas sobre uma parte da fronteira, G1 ? ??. O objetivo é o de reconstruir o traço da H1(?)-solução da equação de Laplace sobre ??\G1. Para tal finalidade, foi analisado dois métodos iterativos; o método de Maz'ia que consiste em resolver sucessivamente problemas de valor de contorno misto (que são bem postos) utilizando os dados de Cauchy como parte das condições de fronteira e o método de Landweber, baseado na equação normal da condição de otimalidade de primeira ordem para resolver o problema de mínimos quadrados. Através de uma abordagem via análise funcional com uma topologia não usual foi demonstrado a análise de convergência para o método de Maz'ia sob dados exatos; por outro lado, para demonstrar que o método de Landweber é um método de regularização e obter taxa de convergência, a teoria de regularização clássica. Ao final, uma relação entre os métodos foi encontrada, a igualdade entre as iterações, possibilitando, assim, concluir a análise do método de Maz'ia, isto é, sob dados com ruídos. Palavras-chave: Problemas inversos, problemas mal postos, problema de Cauchy elíptico, métodos iterativos de regularização, método de Maz'ia, método de Landweber.Abstract : This dissertation deals with the classical ill-posed problem example, the elliptic Cauchy problem for the Laplace operator at a suficiently regular set ? ? R2, where the Cauchy data are given only at part of the boundary, G1 ? ??. The goal is to reconstruct the trace of H1 (?)-solution of the Laplace equation at ??\G1. For such purpose, two iterative methods are analyzed; the algorithm of Maz'ia is a method based on solving successively well-posed mixed boundary value problems using the given Cauchy data as part of the boundary data and the Landweber iteration, which is based on the normal equation of the first order optimality condition to solve the nonlinear least square problem. An approach via functional analysis with unusual topology was used to proof the convergence analysis under exact data; on the other hand, to show that Landweber iteration is a regularization method and to obtain a convergence rate, the classical regularization theory was widely used. At the end of this dissertation, a relation between the methods was found, the iterations are equal, allowing to complete the Maz'ia's method analysis, i.e., under noise data. Keywords: Inverse problems, ill-posed problems, elliptic Cauchy problem, iterative regularization methods, Maz'ia algorithm, Landweber iteration

Modelos Analíticos de Dispersão de Poluentes Atmosféricos

TCC (graduação) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Curso de Matemática.Neste Trabalho de Conclusão de Curso apresentamos e resolvemos dois modelos de dispersão atmosférica. Nosso objetivo foi aprender e praticar algumas das técnicas de resolução¸ de equações diferenciais parciais (EDPs), as transformadas de Laplace e função¸ de Green, aplicadas neste problema físico. Os modelos de dispersão atmosférica se referem `a descrição do transporte aéreo de partículas atmosféricas a partir da Lei da Conservação de Massa para a concentração das partículas (o que nos d´a um problema envolvendo EDPs), em que o termo dispersão ´e usado para descrever a combinação dos fenômenos de difusão e de advecção no fluxo de massa que ocorre com o ar próximo `a superfície da Terra, com a difusão sendo os movimentos de vórtices gerados pelo vento e a adveccao sendo o transporte de partículas causado pelas correntes de ar. Os dois modelos se referem a partículas atmosféricas cuja emissão da fonte pontual ´e constante e está sob vento unidirecional de velocidade também constante. A diferença entre os modelos ´e que para o primeiro não consideramos processos de remoção de partículas da atmosfera, enquanto que no segundo ´e considerado o mecanismo de deposição¸ ˜ao. Para o primeiro modelo, apresentamos todas as hipóteses simplificadoras para deduzirmos o modelo da pluma gaussiana, o qual resolvemos pelas transformadas de Laplace. Para o segundo, mostramos como a hipótese de considerar o fenômeno da deposição¸ ˜ao altera o problema de EDP e o resolvemos pelas transformadas de Laplace e função de Green

Inversion for subbottom sound velocity profiles in the deep and shallow ocean

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2005This thesis investigates the application of acoustic measurements in the deep and shallow ocean to infer the sound velocity profile (svp) in the seabed. For the deep water ocean, an exact method based on the Gelfand-Levitan integral equation is evaluated. The input data is the complex plane-wave reflection coefficient estimated from measurements of acoustic pressure in water. We apply the method to experimental data and estimate both the reflection coefficient and the seabed svp. A rigorous inversion scheme is hence applied in a realistic problem. For the shallow ocean, an inverse eigenvalue technique is developed. The input data are the eigenvalues associated with propagating modes, measured as a function of source-receiver range. We investigate the estimation of eigenvalues from acoustic fields measured in laterally varying environments. We also investigate the errors associated with estimating varying modal eigenvalues, analogous to the estimation of time-varying frequencies in multicomponent signals, using time-varying autoregressive (TVAR) methods. We propose and analyze two AR sequential estimators, one for model coefficients, another for the zeros of the AR characteristic polynomial. The decimation of the pressure field defined in a discrete range grid is analyzed as a tool to improve AR estimation. The nonlinear eigenvalue inverse problem of estimating the svp from a sequence of eigenvalues is solved by iterating linearized approximations. The solution to the inverse problem is proposed in the form of a Kalman filter. The resolution and variance of the eigenvalue inverse problem are analyzed in terms of the Cramer-Rao lower bound and the Backus-Gilbert (BG) resolution theory. BG theory is applied to the design of shallow-water experiments. A method is developed to compensate for the Doppler deviation observed in experiments with moving sources.I am grateful for the support of my work provided by the WHOI Academic Programs Office and the Office of Naval Research

Schopenhauer and Luhmann: Some Unlikely Similarities?

The purpose of this paper is to compare similarities between Schopenhauer's conception of the world as Representation and Niklas Luhmann's notion of society as Communication. We explore the similarities between the way in which Schopenhauer constructs his speculations on the comprehension of reality, and how Luhmann describes what he considers contemporary society’s intelligibility. The analyses presented here do not deal with the discussion of the nature of the Will and its manifestations in the process of construction of reality, which constitutes a relevant part of Schopenhauer's thought. At the end of our exposition we infer some points of convergence in these authors’ explanatory models, although it is not possible to deduce, in a direct and categorical way, a theoretical affiliation between them. Keywords: Schopenhauer. Representation. Luhmann. Communication. Systems. DOI: 10.7176/RHSS/12-16-06 Publication date:August 31st 202