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Dispositivi protesici medicali biocompatibili a base di leghe di cobalto e procedimento per la loro preparazione
No full textMateriali compositi a matrice metallica a base di titanio e loro impiego per la produzione di utensili da taglio
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Low content and free cobalt matrixes for diamond tools
No full textIn the present work several titanium alloys were evaluated as matrixes for diamond tools. The purpose is to find new metal matrixes
not containing cobalt or with the amount minimised. Due to the low expansion thermal coefficient of titanium, diamond composites were
produced by pressureless sintering, that means a relevant economic saving. The effect of different Ti–Ni ratio and of small aluminum and
cobalt additions on the mechanical properties of the alloys was investigated. The monolithic metal alloys and diamond composites were
characterized by density measurements. The structure was investigated by X-ray diffraction analysis (XRD), the microstructure by optical and
electron microscopy. Hardness as well as erosion tests were performed as mechanical characterization. The diamond retention capability and
the metal-diamond interface were evaluated by electron microscopy on the fracture surfaces of composites. Crack free composites, presenting
high relative density, were obtained. They show a strong diamond-metal interface. No graphitization evidence on diamond particles was
observed. Hardness value and an erosion resistance comparable with that of hot pressed cobalt was registered in some cases
Surface treatment on an implant cobalt alloy for high biocompatibility and wear resistance
No full textAbstract Total hip prostheses are implanted to younger and more active patients, so the open problem is to create implants which will enhance the implant survivorship and will offer greater longevity. From this point of view, metal-on-metal arthroprostheses are well performing. The volume of periprosthetic inflammatory tissues appears to be less than with metal-on-UHMPWE, however osteolysis often occurs and it is known that the levels of metal ions in the blood and urine are elevated in patients with metal-on-metal bearing. The aim of this research activity was the synthesis and characterization of surface modified cobalt alloys, in order to obtain a biocompatible material presenting at the same time good wear performances, low metal ion release and low toxicity. The surface chemical composition of an implant cobalt alloy (Biodur) was modified, producing relevant tantalum enrichment. Tantalum was chosen because of its low toxicity and high corrosion resistance. The chemical composition, morphology, roughness, crystallographic structure and wettability of the surface, as well as the interface of the modified layer with the substrate, were characterized. The mechanical behavior of the modified materials was investigated by scratch and pin-on-disc wear tests. The metal ion release of the modified surfaces was measured by in vitro experiments after wear tests
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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