On the choice of parameters in solar structure inversion

The observed solar p-mode frequencies provide a powerful diagnostic of the internal structure of the Sun and permit us to test in considerable detail the physics used in the theory of stellar structure. Amongst the most commonly used techniques for inverting such helioseismic data are two implementations of the optimally localized averages (OLA) method, namely the Subtractive Optimally Localized Averages (SOLA) and Multiplicative Optimally Localized Averages (MOLA). Both are controlled by a number of parameters, the proper choice of which is very important for a reliable inference of the solar internal structure. Here we make a detailed analysis of the influence of each parameter on the solution and indicate how to arrive at an optimal set of parameters for a given data set.Comment: 14 pages, 15 figures. Accepted for publication on MNRA

On The Determination of MDI High-Degree Mode Frequencies

The characteristic of the solar acoustic spectrum is such that mode lifetimes get shorter and spatial leaks get closer in frequency as the degree of a mode increases for a given order. A direct consequence of this property is that individual p-modes are only resolved at low and intermediate degrees, and that at high degrees, individual modes blend into ridges. Once modes have blended into ridges, the power distribution of the ridge defines the ridge central frequency and it will mask the true underlying mode frequency. An accurate model of the amplitude of the peaks that contribute to the ridge power distribution is needed to recover the underlying mode frequency from fitting the ridge. We present the results of fitting high degree power ridges (up to l = 900) computed from several two to three-month-long time-series of full-disk observations taken with the Michelson Doppler Imager (MDI) on-board the Solar and Heliospheric Observatory between 1996 and 1999. We also present a detailed discussion of the modeling of the ridge power distribution, and the contribution of the various observational and instrumental effects on the spatial leakage, in the context of the MDI instrument. We have constructed a physically motivated model (rather than some ad hoc correction scheme) resulting in a methodology that can produce an unbiased determination of high-degree modes, once the instrumental characteristics are well understood. Finally, we present changes in high degree mode parameters with epoch and thus solar activity level and discuss their significance.Comment: 59 pages, 38 figures -- High-resolution version at http://www-sgk.harvard.edu:1080/~sylvain/preprints/ -- Manuscript submitted to Ap

1D generalized statistics gas: A gauge theory approach

A field theory with generalized statistics in one space dimension is introduced. The statistics enters the scene through the coupling of the matter fields to a statistical gauge field, as it happens in the Chern-Simons theory in two dimensions. We study the particle-hole excitations and show that the long wave length physics of this model describes a gas obeying the Haldane generalized exclusion statistics. The statistical interaction is found to provide a way to describe the low-T critical properties of one-dimensional non-Fermi liquids.Comment: 8 pages, revte

Growth and phosphorus absorption by common bean 'Xodó' genotype under effect of glyphosate reduced rates.

Avaliou-se o efeito de subdoses de glyphosate no crescimento e na absorção de fósforo (P) pelo feijoeiro comum (Phaseolus vulgaris L.) cv. Xodó. O experimento foi conduzido em esquema fatorial 4 x 2 em blocos casualizados com quatro repetições, sendo o primeiro fator constituído pelas subdoses de 0; 4,32; 8,64 e 12,96 g ha-1 de equivalente ácido (e.a.) de glyphosate e o segundo fator constituído por doses de P no solo (50 e 250 mg dm-3). Avaliações foram realizadas 30 dias após a aplicação do glyphosate (DAA). A subdose de 12,96 g ha-1 estimulou o crescimento do feijoeiro comum cv. Xodó, assim como aumentou o teor de P no ramo e o conteúdo de P na parte aérea das plantas

The Several Guises of the BRST Symmetry

We present several forms in which the BRST transformations of QCD in covariant gauges can be cast. They can be non-local and even not manifestly covariant. These transformations may be obtained in the path integral formalism by non standard integrations in the ghost sector or by performing changes of ghost variables which leave the action and the path integral measure invariant. For different changes of ghost variables in the BRST and anti-BRST transformations these two transformations no longer anticommute.Comment: 3 pages, revte

Cuidados básicos com microscópios ópticos.

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