Cypsela or achene? Refining terminology by considering anatomical and historical factors

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Historical land-cover/use in different slope and riparian buffer zones in watersheds of the state of São Paulo, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

HBT interferometry: historical perspective

I review the history of HBT interferometry, since its discovery in the mid 1950's, up to the recent developments and results from BNL/RHIC experiments. I focus the discussion on the contributions to the subject given by members of our Brazilian group.

Comments on regularization ambiguities and local gauge symmetries

We study the regularization ambiguities in an exact renormalized (1 + 1)-dimensional field theory. We show a relation between the regularization ambiguities and the coupling parameters of the theory as well as their role in the implementation of a local gauge symmetry at quantum level.

Camponeses Brazil's Peasant Movement in Historical Perspective (1946-2004)

Comparison of the histories of three leading peasant organizations in the Pontal do Paranapanema region of Brazil-the Partido Comunista do Brasil (PCB) from 1945 to 1964, the Confederacao Nacional de Trabalhadores na Agricultura (CONTAG) from 1964 to 1984, and the Movimento dos Trabalhadores Rurais Sem-Terra (MST) from 1984 to 2004-suggests that continuity is as important as change in understanding Brazilian peasant movements. The MST has been considered a "new social movement" in that it has eschewed partisan politics, incorporated families as members rather than just male heads of household, had a national scope and a participatory decision-making structure, and been attuned to the international struggle over globalization. Placing it in historical perspective makes it clear, however, that this is not the first time that militants have organized around the concept of peasants as a political identity; that while the representation of peasants in the leadership of contemporary rural labor organizations may be greater than in the past, earlier peasant leaders also struggled on behalf of their class; that earlier peasant organizations had, if not a national presence, a substantial presence in the agricultural states of the time; and that attempts at international organization to unite peasant struggles around the globe are not entirely new. This is not to deny the innovative features of contemporary movements but to suggest that the investigation of past achievements will contribute to a fuller appreciation of these movements' conditions and prospects.

Ceramic materials in dentistry: historical evolution and current practice

Dental ceramics are presented within a simplifying framework allowing for facile understanding of their development, composition and indications. Engineering assessments of clinical function are dealt with and literature is reviewed on the clinical behaviour of all-ceramic systems. Practical aspects are presented regarding the choice and use of dental ceramics to maximize aesthetics and durability, emphasizing what we know and how we know it.

Pulsar test of a violation of discrete symmetries in gravitation

We determine an improved limit on C and P violation to the extended gravitational potential of Leitner and Okubo using the millisecond pulsar PSR 1937+214 data. © 1989.

Higher spin symmetries and w∞ algebra in the conformal affine Toda model

As recently shown the conformal affine Toda models can be obtained via hamiltonian reduction from a two-loop Kac-Moody algebra. In this paper we propose a systematic procedure to analyze the higher spin symmetries of the conformal affine Toda models. The method is based on an explicit construction of infinite towers of extended conformal symmetry generators. Two fundamental building blocks of this construction are special spin-one and -two primary fields characterizing the conformal structure of these models. The connection to the algebra of area preserving diffeomorphisms on a two-manifold (w∞ algebra) is established.

Toda and Volterra lattice equations from discrete symmetries of KP hierarchies

The discrete models of the Toda and Volterra chains are being constructed out of the continuum two-boson KP hierarchies. The main tool is the discrete symmetry preserving the Hamiltonian structure of the continuum models. The two-boson currents of KP hierarchy are being associated with sites of the corresponding chain by successive actions of discrete symmetry.

On discrete symmetries of the multi-boson KP hierarchies

We show that the multi-boson KP hierarchies possess a class of discrete symmetries linking them to discrete Toda systems. These discrete symmetries are generated by the similarity transformation of the corresponding Lax operator. This establishes a canonical nature of the discrete transformations. The spectral equation, which defines both the lattice system and the corresponding Lax operator, plays a key role in determining pertinent symmetry structure. We also introduce the concept of the square root lattice leading to a family of new pseudo-differential operators with covariance under additional Bäcklund transformations.

Symmetries and time evolution in discrete phase spaces: a soluble model calculation

Using the flexibility and constructive definition of the Schwinger bases, we developed different mapping procedures to enhance different aspects of the dynamics and of the symmetries of an extended version of the two-level Lipkin model. The classical limits of the dynamics are discussed in connection with the different mappings. Discrete Wigner functions are also calculated. © 1995.