Resistance of Cyanobacterial Fouling on Architectural Paint Films to Cleaning by Water Jet

Mortar panels painted with three different white acrylic coatings were exposed to the environment in urban (So Paulo) and rural (Pirassununga) sites in Brazil for 7 years. After this time, all panels were almost equally discoloured, and paint detachment was observed to only a small degree. The biofilms were composed mainly of cyanobacteria and filamentous fungi, principal genera being Gloeocapsa and Chroococcidiopsis of the cyanobacteria, and Cladosporium and Alternaria of the fungi. Two of the three paints in Pirassununga became covered by a pink film that contained red-encapsulated Gloeocapsa and clay particles. The third, an 800% elastomeric matt formulation, became discoloured with a grey, only slightly pink, film, although the same cyanobacteria were present. The levels of paint detachments from all films in both locations were low, with rating range of 0-1 of a maximum 5 (100% detachment). After high-pressure water jetting, paint detachments increased at both locations, up to 2 in Pirassununga and 3 in So Paulo. Discoloration decreased; L*A*B* analysis of surface discoloration showed that Delta E (alteration in colour from the original paint film) changed from 28-39 before cleaning to 13-16 afterwards. The pink coloration was not entirely removed from Pirassununga samples, suggesting that cyanobacterial cells are difficult to detach, and microscopic analysis of the biofilms confirmed that Gloeocapsa was still present as the principal contaminant on all surfaces, with Chroococcidiopsis being present as the second most common. Almost no fungi were detected after water jet application.

Local symmetries in gauge theories in a finite-dimensional setting

It is shown that the correct mathematical implementation of symmetry in the geometric formulation of classical field theory leads naturally beyond the concept of Lie groups and their actions on manifolds, out into the realm of Lie group bundles and, more generally, of Lie groupoids and their actions on fiber bundles. This applies not only to local symmetries, which lie at the heart of gauge theories, but is already true even for global symmetries when one allows for fields that are sections of bundles with (possibly) non-trivial topology or, even when these are topologically trivial, in the absence of a preferred trivialization. (C) 2012 Elsevier B.V. All rights reserved.

Gauge and integrable theories in loop spaces

We propose an integral formulation of the equations of motion of a large class of field theories which leads in a quite natural and direct way to the construction of conservation laws. The approach is based on generalized non-abelian Stokes theorems for p-form connections, and its appropriate mathematical language is that of loop spaces. The equations of motion are written as the equality of a hyper-volume ordered integral to a hyper-surface ordered integral on the border of that hyper-volume. The approach applies to integrable field theories in (1 + 1) dimensions, Chern-Simons theories in (2 + 1) dimensions, and non-abelian gauge theories in (2 + 1) and (3 + 1) dimensions. The results presented in this paper are relevant for the understanding of global properties of those theories. As a special byproduct we solve a long standing problem in (3 + 1)-dimensional Yang-Mills theory, namely the construction of conserved charges, valid for any solution, which are invariant under arbitrary gauge transformations. (C) 2012 Elsevier B.V. All rights reserved.

Effective potential for Horava-Lifshitz-like theories

We study the one-loop effective potential for some Horava-Lifshitz-like theories.

Higher spatial derivative field theories

In this work, we employ renormalization group methods to study the general behavior of field theories possessing anisotropic scaling in the spacetime variables. The Lorentz symmetry breaking that accompanies these models are either soft, if no higher spatial derivative is present, or it may have a more complex structure if higher spatial derivatives are also included. Both situations are discussed in models with only scalar fields and also in models with fermions as a Yukawa-like model.

Ward identities in Lifshitz-like field theories

In this work, we develop a normal product algorithm suitable to the study of anisotropic field theories in flat space, apply it to construct the symmetries generators and describe how their possible anomalies may be found. In particular, we discuss the dilatation anomaly in a scalar model with critical exponent z = 2 in six spatial dimensions.

QUASI-TOPOLOGICAL QUANTUM FIELD THEORIES AND Z(2) LATTICE GAUGE THEORIES

We consider a two-parameter family of Z(2) gauge theories on a lattice discretization T(M) of a three-manifold M and its relation to topological field theories. Familiar models such as the spin-gauge model are curves on a parameter space Gamma. We show that there is a region Gamma(0) subset of Gamma where the partition function and the expectation value h < W-R(gamma)> i of the Wilson loop can be exactly computed. Depending on the point of Gamma(0), the model behaves as topological or quasi-topological. The partition function is, up to a scaling factor, a topological number of M. The Wilson loop on the other hand, does not depend on the topology of gamma. However, for a subset of Gamma(0), < W-R(gamma)> depends on the size of gamma and follows a discrete version of an area law. At the zero temperature limit, the spin-gauge model approaches the topological and the quasi-topological regions depending on the sign of the coupling constant.

Uma arqueologia de diagramas cibernéticos

This paper investigates the use of explicit structures of information in architectural design. Particularly, it approaches the use of diagrams related to cybernetics and information theory in experimental practices in the 1960’s and 1970’s. It analyses the diagram of cybernetic control proposed by the cybernetician Gordon Pask for the Fun Palace, the diagrams produced by the utopian architect Yona Friedman in the conceptual description of the Flatwriter program and Christopher Alexander’s diagrams and his theories of Synthesis of Form and Pattern Language. Finally it establishes a brief parallel between current domestication and use of dataflow programming with the cybernetic diagrams, highlighting differences in their complexity approach.

Drawing and surface: freehand architectural drawing mediated by digital

This paper discusses the redefinition of the function of freehand drawing in the design process in view of intuitive digital media. It sets forth an interpretive analysis of an experiment with drawing on opaque tablets, carried out with a group of students of the Instituto de Arquitetura e Urbanismo da Universidade de São Paulo. After a brief review of the current debate on freehand drawing and the advent of digital media, we examine the experiment as a possible way to elicit facts that may contribute to the discussion. To this end, our research has concentrated on the intuitive use enabled by existing digital media. It is our intention that this empirical approximation becomes a pilot experiment for the use of digital tablets in the process of construction the gaze of the student in Architecture and Urbanism as a reflection on the different cognitive dimensions that constitute the practice of drawing and its reinterpretation to develop new ideas.

Dos diagramas aos parâmetros: transformações no design digital

The article is part of an ongoing theoretical research about the emergence of parametric architecture. It discusses some of the last developments in digital design from the transition of the discourse and operativity by “diagrams” to the theories and processes derived from “parameters”. Centered in Peter Eisenman’s and Patrik Schumacher’s propositions, it is in its horizon to comprehend what relations are established between “diagram” and “parameter” -­‐ similarities, complementarities and differences -­‐, contributing for the critical contextualization of theoretical movements and design processes in contemporary architecture.

Some aspects of self-duality and generalised BPS theories

If a scalar eld theory in (1+1) dimensions possesses soliton solutions obeying rst order BPS equations, then, in general, it is possible to nd an in nite number of related eld theories with BPS solitons which obey closely related BPS equations. We point out that this fact may be understood as a simple consequence of an appropriately generalised notion of self-duality. We show that this self-duality framework enables us to generalize to higher dimensions the construction of new solitons from already known solutions. By performing simple eld transformations our procedure allows us to relate solitons with di erent topological properties. We present several interesting examples of such solitons in two and three dimensions.