Evaluation of corrosion resistance and cytotoxicity of electrodeposited gold on various types of intermediate layers

Gold plated surfaces are widely applied in several technical and decorative fields. The two main issues regarding the discussion on the field of precious metal coatings concern the increase in the use of thinner gold layers and 'Ni free' substrates. In order to ensure the quality of the final products, the effects of the plated surfaces on their performance require thorough and accurate research. In this paper, the corrosion resistance of gold plated nickel, copper and bronze was investigated by electrochemical methods specifically potentiodynamic polarisation and electrochemical impedance spectroscopy in phosphate buffered saline. The cytotoxicity of the gold plated substrates was also evaluated and compared. The results showed that the substrate related to the best corrosion resistance and cytotoxicity among the tested ones was bronze, and the one with the lowest performance was nickel.

New historical archeointensity data from Brazil: Evidence for a large regional non-dipole field contribution over the past few centuries

We report new archeointensity data obtained from the analyses of baked clay elements (architectural and kiln brick fragments) sampled in Southeast Brazil and historically and/or archeologically dated between the end of the XVIth century and the beginning of the XXth century AD. The results were determined using the classical Thellier and Thellier protocol as modified by Coe, including partial thermoremanent magnetization (pTRM) and pTRM-tail checks, and the Triaxe protocol, which involves continuous high-temperature magnetization measurements. In both protocols, TRM anisotropy and cooling rate TRM dependence effects were taken into account for intensity determinations which were successfully performed for 150 specimens from 43 fragments, with a good agreement between intensity results obtained from the two procedures. Nine site-mean intensity values were derived from three to eight fragments and defined with standard deviations of less than 8%. The site-mean values vary from similar to 25 mu T to similar to 42 mu T and describe in Southeast Brazil a continuous decreasing trend by similar to 5 mu T per century between similar to 1600 AD and similar to 1900 AD. Their comparison with recent archeointensity results obtained from Northeast Brazil and reduced at a same latitude shows that: (1) the geocentric axial dipole approximation is not valid between these southeastern and northeastern regions of Brazil, whose latitudes differ by similar to 10 degrees, and (2) the available global geomagnetic field models (gufm1 models, their recalibrated versions and the CALSK3 models) are not sufficiently precise to reliably reproduce the non-dipole field effects which prevailed in Brazil for at least the 1600-1750 period. The large non-dipole contribution thus highlighted is most probably linked to the evolution of the South Atlantic Magnetic Anomaly (SAMA) during that period. Furthermore, although our dataset is limited, the Brazilian archeointensity data appear to support the view of a rather oscillatory behavior of the axial dipole moment during the past three centuries that would have been marked in particular by a moderate increase between the end of the XVIIIth century and the middle of the XIXth century followed by the well-known decrease from 1840 AD attested by direct measurements. (C) 2011 Elsevier B.V. All rights reserved.

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.