On the tribological behaviour of metal/ceramic and metal/metal couplings

Corrosion, wear or the combined effects of these failure modes cost the industrial economies hundreds of billions of euros each year. One of the more effective ways to reduce damage due to corrosion and wear is to treat, or “engineer” the surface, so that it can perform functions that are distinct from those required by most materials. For example, steel is a very popular material, because it is inexpensive, strong and easily manufactured. Unfortunately, it is highly susceptible to corrosion in many environments and therefore needs to be coated in order to achieve a satisfactory life service. Small components can be painted, aluminized, electroplated, or clad with more corrosion resistant materials. For parts that also require wear strength, they can be thermally sprayed or coated with thin-films. Finally, when dealing with large components, the size, weight, and handling problems may limit the type of surface treatment to be considered. The aim of the research work presented in this PhD thesis was to study the interactions between the metal/ceramic and metal/metal coupling surfaces to improve the wear resistance of the materials in sliding motion. Most of my research work is included here as a collection of three papers submitted in the same format they were published or in a preprint version. Each paper is an individual piece of work with separate sections including: abstract, introduction, materials and experimental details, results and discussion, conclusions, and references. A failure analysis study was carried out on some specific mechanical components of diesel engines for industrial application. In order to increase the wear resistance of rocker arms, pushrods and valves, the deposition of ceramic coatings thermally sprayed was considered. Wear tests were performed on a plasma-sprayed ceramic coating in sliding motion against steel in order to understand the effect of a normal load applied, as well as the environmental conditions on the metal/ceramic coupling. Moreover, the influence of relative humidity on the tribological behaviour of two types of plasma-sprayed ceramic coatings and two types of HVOF-sprayed cermets in sliding motion against alumina, was evaluated through pin-on-disk testing. Different techniques for the microstructural examination were employed in this research study: Optical Microscopes (OM) and Scanning Electron Microscopes (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) microprobe were used and also X-ray Diffraction (XRD) was carried out to describe the morphology of worn surfaces and to identify the main wear mechanisms involved. In addition, surface roughness, Vickers microhardness and fracture toughness measurements were performed in order to characterise the materials subjected to wear testing

Effective elimination of Staphylococcal contamination from hospital surfaces by a bacteriophage-probiotic sanitation strategy: a monocentric study.

Persistent contamination of hospital surfaces and antimicrobial resistance (AMR) are recognized major causes of healthcare-associated infections (HAI). We recently showed that a probiotic-based sanitation (PCHS) can stably decrease surface pathogens and reduce AMR and HAIs. However, PCHS action is slow and non-specific. By contrast, bacteriophages have been proposed as a decontamination method as they can rapidly attack specific targets, but their routine application has never been tested. Here we analyzed the feasibility and effectiveness of phage addition to PCHS sanitation, aiming to obtain a rapid and stable abatement of specific pathogens in the hospital environment. Staphylococcal contamination in the bathrooms of General Medicine wards was analyzed, being such areas the most contaminated and Staphylococci the most prevalent bacteria in such settings. Results showed that a daily phage application by nebulization induced a rapid and significant decrease of Staphylococcus spp. load on treated surfaces, up to 97% more than PCHS alone (p<0.001), suggesting that such system might be considered as a part of prevention and control strategies, to counteract outbreaks of specific pathogens and prevent associated infections

Classification Trees for Ordinal Responses in R: The rpartScore Package

This paper introduces rpartScore (Galimberti, Soffritti, and Di Maso 2012), a new R package for building classification trees for ordinal responses, that can be employed whenever a set of scores is assigned to the ordered categories of the response. This package has been created to overcome some problems that produced unexpected results from the package rpartOrdinal (Archer 2010). Explanations for the causes of these unexpected results are provided. The main functionalities of rpartScore are described, and its use is illustrated through some examples

Tribunais de papel. O palimpsesto do romance policial e Sempreviva

The aim of this study is to analyze the way in which detective novel as a genre shapes narratives that discuss the function of law and, therefore, the existence of a(n) (im)possible justice, when it is (not) put into existence by the institutions responsible for it. The starting point of this analysis will be Antônio Callado's novel, Sempreviva, written in 1981 during the transitional period towards democracy when the Amnesty Law, institutionalizing an official amnesia, makes it difficult to access reality and to process trauma, identifying, instead of a change, the persistence of the past into the present

"Que lindo cenário!" Trasformazione della facciata nazionale durante l'Estado Novo

Con il presente studio si intende indagare i meccanismi di costruzione del paesaggio folclorico in epoca salazarista, mettendo in evidenza le continuità con i meccanismi di feticizzazione e compensazione già inaugurati sul finire del XIX secolo