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Transmission electron microscopy has been a promising candidate for mapping atomic orbitals for a long time. Here, we explore its capabilities by a first-principles approach. For the example of defected graphene, exhibiting either an isolated vacancy or a substitutional nitrogen atom, we show that three different kinds of images are to be expected, depending on the orbital character. To judge the feasibility of visualizing orbitals in a real microscope, the effect of the optics' aberrations is simulated. We demonstrate that, by making use of energy filtering, it should indeed be possible to map atomic orbitals in a state-of-the-art transmission electron microscope.

This paper reports the preliminary results obtained from the data acquired during the diagnostic survey, begun in September 2011, to evaluate the state of conservation of the mural Tuttomondo (1989) by Keith Haring (1958-1990). Multispectral imaging technique, ultra-high resolution photography, ultraviolet (UV), visible (Vis), and near infrared (NIR) Fiber Optic Reflectance Spectroscopy (FORS), colorimetry, and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) analysis were performed directly on the mural or on samples taken from the mural to support the conservation intervention, which was focused on cleaning and the subsequent consolidation of the painting. These analyses were carried out as part of the research project "Preventive Conservation of Contemporary Art" (COPAC). The COPAC Project is a 2-year research project (2011-2013) financially supported by the Regione Toscana (Tuscany, Italy) in the PAR-FAS program, Disciplinary Framework Science and Technology for the Safeguard and Valorisation of Cultural Heritage. The COPAC 2 Project is a joint effort of research institutions, conservators, city councils, museums, and art collections in Tuscany. COPAC activities are focused mainly on the study of the materials used by contemporary artists to produce their artworks with a twofold goal: defining artworks materials and monitoring their conservation and/or their degradation processes over time. In order to achieve this goal the research team adopted a plan based on the use of several diagnostic methodologies for the study of selected contemporary artworks belonging to museums, galleries, and collections in Tuscany. The purpose of this approach was to acquire as much data as possible about artists' materials and techniques and, also, to monitor both the state-of-conservation of the artworks and the surrounding environmental conditions (Learner, T. 2005; Chiantore, O., Rava, A. 2013). All of the collected data will be used to evaluate the conservation-state of the artworks selected for investigation and to identify their risk factors in order to select the most appropriate preservation practices. The ultimate goal of the COPAC Project is to set up an interactive archive to manage and disseminate the acquired information for the benefit of all of the curatorial and technical participants.

In this paper, the effect of laser pulse energy on double-pulse laser induced breakdown spectroscopy signal is studied. In particular, the energy of the first pulse has been changed, while the second pulse energy is held fixed. A systematic study of the laser induced breakdown spectroscopy signal dependence on the interpulse delay is performed, and the results are compared with the ones obtained with a single laser pulse of energy corresponding to the sum of the two pulses. At the same time, the crater formed at the target surface is studied by video-confocal microscopy, and the variation in crater dimensions is correlated to the enhancement of the laser induced breakdown spectroscopy signal. The results obtained are consistent with the interpretation of the double-pulse laser induced breakdown spectroscopy signal enhancement in terms of the changes in ambient gas pressure produced by the shock wave induced by the first laser pulse.

Este trabalho é dedicado à análise das características do atrito e desgaste de compósitos carbono-carbono unidireccionais e bidireccionais em deslizamento como pares dissemelhantes na geometria pino-disco, tendo em conta a influência da velocidade de deslizamento (0.5v3.5 ms-1) e da temperatura de teste (22ºCT600ºC). No que respeita aos parâmetros tribológicos, o coeficiente de atrito caracterizou-se por valores próximos de 0.25 para o deslizamento à temperatura ambiente e diminuiu para aproximadamente 0.1 para os testes acima da temperatura ambiente. A amplitude de variação do coeficiente de atrito aumentou com a velocidade e foi praticamente nula para o deslizamento acima da temperatura ambiente. Para o coeficiente de desgaste foram obtidos valores inferiores a 10-6 mm3N-1m-1 para o deslizamento à temperatura ambiente e baixa velocidade, mas foi observada elevada degradação superficial para condições extremas de velocidade de deslizamento ou de temperatura de teste. A perda da resistência ao desgaste dos compósitos carbono-carbono foi devida essencialmente a mecanismos de fractura superficial e descoesão fibra-matriz.