Multifunctional TiO2 coatings developed by plasma electrolytic oxidation technique on a Ti20Nb20Zr4Ta alloy for dental applications.

A newly developed ß-Ti alloy based on the Ti-Nb-Zr-Ta system (Ti20Nb20Zr4Ta) has been subjected to Plasma Electrolytic Oxidation (PEO) treatment to obtain a multifunctional ceramic-like (TiO2) coating with superior tribocorrosion (wear and corrosion) resistance and improved biocompatibility. For this aim, elements such as Ca, P, and Ag NPs have been incorporated into the oxide film to obtain bioactive and biocide properties. The chemical composition and morphology of the TiO2-PEO coating was characterized, and its multifunctionality was addressed by several means, including antibacterial activity assessment, formation of bone-like apatite, metallic ion release evaluation, in vitro cellular response analysis, and corrosion and tribocorrosion tests in artificial saliva. The developed coatings enhanced the corrosion and tribocorrosion resistance of the bare alloy and exhibited antibacterial ability with low cytotoxicity and negligible ion release. Furthermore, they were able to sustain MC3T3-E1 preosteoblast viability/proliferation and osteogenic differentiation. Altogether, the results obtained demonstrate the potential of the TiO2 coating incorporating Ca, P, and Ag NPs to be used for dental applications.

Eco-friendly non-biocide-release coatings for marine biofouling prevention.

Environmental concerns have been changing the way of looking for solutions to problems. The hydrosphere, together with its biosphere, has been feeling the impact of many pollutants, used for instance in the marine industry for economic reasons or lack of knowledge of their effects. In particular biocides, applied as coatings in paints, are released into the waters becoming toxic and persistent extending their action to an area far beyond the initial coated surface they should protect. In order to minimize these side effects, two biocides, Irgarol (I) and Econea (E), were covalently attached to polyurethane (PU) and foul-release silicone based (PDMS) marine paints through an isocyanate linker. Their antifouling bioactivity was better in PDMS coatings, both for single (Econea) and combined biocides (E/I ratio = 1.5) with contents lower than 0.6 wt%. The treated samples remained almost clean after more than one year immersion in the Portuguese shore of the Atlantic Ocean, and after about 24 weeks under the tropical conditions of Singapore (Fouling rate < 1%). Complementary biofilm adhesion susceptibility tests against Pseudoalteromonas tunicata D2 showed adhesion reduction higher than 90% for PU formulations containing single biocides and close to 100% for PDMS with combined biocides. The eco-toxicity assessment evidenced a low environmental impact, in accordance with the European standards. In addition, shipping field trial tests showed the best antifouling performance for the Econea-based PDMS formulations (E = 0.6 wt%), which remained clean for about nine months in open seawaters, proving the efficacy of this non-release strategy, when applied under dynamic conditions.

Topsoil structure stability in a restored floodplain: Impacts of fluctuating water levels, soil parameters and ecosystem engineers.

Ecosystem services provided by floodplains are strongly controlled by the structural stability of soils. The development of a stable structure in floodplain soils is affected by a complex and poorly understood interplay of hydrological, physico-chemical and biological processes. This paper aims at analysing relations between fluctuating groundwater levels, soil physico-chemical and biological parameters on soil structure stability in a restored floodplain. Water level fluctuations in the soil are modelled using a numerical surface-water-groundwater flow model and correlated to soil physico-chemical parameters and abundances of plants and earthworms. Causal relations and multiple interactions between the investigated parameters are tested through structural equation modelling (SEM). Fluctuating water levels in the soil did not directly affect the topsoil structure stability, but indirectly through affecting plant roots and soil parameters that in turn determine topsoil structure stability. These relations remain significant for mean annual days of complete and partial (>25%) water saturation. Ecosystem functioning of a restored floodplain might already be affected by the fluctuation of groundwater levels alone, and not only through complete flooding by surface water during a flood period. Surprisingly, abundances of earthworms did not show any relation to other variables in the SEM. These findings emphasise that earthworms have efficiently adapted to periodic stress and harsh environmental conditions. Variability of the topsoil structure stability is thus stronger driven by the influence of fluctuating water levels on plants than by the abundance of earthworms. This knowledge about the functional network of soil engineering organisms, soil parameters and fluctuating water levels and how they affect soil structural stability is of fundamental importance to define management strategies of near-natural or restored floodplains in the future.

Estabilidad cardiovascular en la microcirugía laríngea y recuperación postoperatoria precoz: comparación entre remifentanilo-sevoflurano vs. remifentanilo-propofol / Cardiovascular and emergence characteristics between sevofluraneremifentanil and propofol-remifentanil in microlaryngeal surgery

Introducción: La microcirugía laríngea es un proceso de corta duración que se asocia con un importante estímulo adrenérgico y frecuentemente realizada en cirugía de día. Diferentes técnicas anestésicas han sido empleadas para el control hemodinámico. Sin embargo, ningún estudio previo ha comparado la eficacia de la combinación sevoflurano y remifentanilo frente a propofol y remifentanilo en el control de la respuesta hemodinámica y parámetros de recuperación. Material y métodos: 37 pacientes ASA I-III con edades comprendidas entre 23-77 años y programados para microcirugía laríngea fueron incluidos en el estudio. Los pacientes fueron randomizados en dos grupos: grupo S-R (sevoflurano y remifentanilo); grupo P-R (propofol y remifentanilo). La infusión de remifentanilo se ajustó para mantener los valores hemodinámicos alrededor de un 20 % de los valores basales (dosis de 0,2 a 0,6 µg/kg/min). Se registraron los parámetros hemodinámicos cada 3 minutos desde la inducción y durante la inserción del laringoscopio rígido. Se compararon los tiempos de extubación, de orientación y de dolor postoperatorio entre ambos grupos. Resultados: No hubo diferencias entre ambos grupos en los parámetros basales. No hubo diferencias entre ambos grupos en la evolución de los valores hemodinámicos tras la inducción y durante la inserción (..) (AU)

Introduction: Laryngeal microsurgery is a short procedure associated with a huge adrenergic response. Different anaesthetics techniques and drugs have been used to try blunting these haemodynamic changes. No previous investigation has directly compared the combination of sevoflurane and remifentanil with that propofol and remifentanil in laryngeal microsurgery. We aimed to compare the haemodynamic responses and emergence characteristics between this two anaesthetic combinations. Material and methods: 37 patients, ASA status I-III, age 23-77 years, scheduled for elective laryngeal microsurgery were included in the study. They were randomly allocated in two groups: Group S-R (sevoflurane-remifentanil) and group P-R (propofol-remifentanil). Remifentanil infusion was adjusted to maintain haemodynamic values around 20 % of baseline. (From 0.2-0.6 µg.kg-1.min-1). Haemodynamic data were measured every 3 minutes from induction and during insertion of the operating laryngoscope. Extubation times, orientation and pain after surgery were recorded. Results: There were no significant differences during baseline. The haemodynamic parameters were similar between the two groups at induction and during insertion of the operating laryngoscope. Thee were no differences in remifentanil requirements between both groups, and the extubation time was similar. More patients had an Aldrete score of 10 at five minutes after extubation in SR group vs. PR group (100 vs. 67 %, p = 0.018). In PACU a higher (..) (AU)

Characterization of Ti-C-N coatings deposited on Ti6Al4V for biomedical applications.

Ti6Al4V alloy is the most commonly employed implant material for orthopedic replacements due to its good mechanical properties close to those of bones, biocompatibility and its good corrosion resistance in biological media. Nevertheless, it does not exhibit good wear resistance, showing friction and wear even with soft tissues. This latter feature can lead to a premature failure of the implant with the subsequent component replacement. Therefore, a system with good tribological resistance is required for several medical applications. One possible alternative to solve tribological problems consists of protecting the alloy surface by means of biocompatible Ti-C-N coatings. In this work, five types of metallic Ti-C-N coatings deposited by physical vapor deposition (PVD) cathodic arc method on Ti6Al4V substrate have been studied. Different deposition conditions have been analyzed, and the superficial properties of films have been characterized. Additionally, tribological response of these films have been determined and compared with the substrate one under fretting conditions in simulated body fluid. The results indicate that Ti-C-N coatings improve the general response of the biomaterial.

Effect of the growth conditions on the optical and mechanical properties of TiO2 and Al2O3 films.

The mechanical and optical properties of TiO2 and Al2O3 films deposited by DC reactive magnetron sputtering were analysed as a function of the deposition conditions. Two different sputtering powers and three different voltages targets which influence the pressure and the deposition rate were studied. The voltage corresponds to two different percentages of the turn down set point of the hysteresis curve and fully poisoned condition. As their optical application is the main functionality of these coatings, the transparency and the refractive index were investigated. However, the mechanical properties are the key factors for determining the performance of these systems in use. For this, the wear resistance of these coatings was studied through the analysis of the evolution of the friction coefficient with time and the analysis of the wear track. The corrosion resistance has been also analysed through electrochemical studies. The results reveal that there is a clear influence of the studied deposition conditions on the mechanical and optical properties of these films. However, while general conclusions could be drawn for Al2O3 films, for TiO2 films the tendency is not so clear and further work needs to be performed.

Characterisation of tribocorrosion behaviour of multilayer PVD coatings.

The effect of repassivation on tribocorrosion behaviour of two multilayer coatings of different structures is studied experimentally by measuring the variation of instantaneous open-circuit potential during friction. One coating consists of alternating Cr and CrN layers, while another consists of alternated layers of CrN and ZrN. Analysis of the results showed that friction force, i.e. the rate of the mechanical energy supplied to the material in the contact zone, has no direct influence on the tribocorrosion behaviour; however, the wear rate does strongly influence the tribocorrosion. A simple phenomenological model of repassivation of the multilayer coating is developed assuming "surface coverage" approach. This model establishes the relationship between the rate of mechanical activation of material by friction and the behaviour of the open-circuit potential.