The electron transfer pathways for the enzymes involved in the four sequential steps of the denitrification pathway are reviewed. In addition, brief information on the electron transfer events is also provided on two enzymes that participate in the dissimilatory nitrate reduction to ammonia. The two main aspects discussed are the intra- and inter-molecular electron transfer pathways and the molecular recognition processes involving the redox partners. When available, information on the residues that are involved in these pathways is given, and their role in electron transfer and/or the formation of the transient electron transfer complexes is discussed. © The Royal Society of Chemistry 2017.

This book is devoted to denitrification, an anaerobic process that is used by a wide range of bacteria for energy generation. The overall process involves nitrate, which is present in soil or water, being reduced to gaseous dinitrogen. This initial chapter aims to place denitrification in the larger context of the nitrogen biogeochemical cycle (a bird's eye view). Detailed topics are developed through the many following contributions. Denitrification is a landscape for probing the structures, functions and mechanisms of action of a wide range of highly specialised metalloenzymes. These carry out, sequentially, four oxo-transfer reactions: NO3 - → NO2 - → NO → N2O → N2. The environmental implications of these processes are of particular relevance. Nitrate accumulation and the release of nitrous oxide into the atmosphere due to the excessive use of fertilisers in agriculture are examples of two environmental problems in which denitrification plays a central role. © The Royal Society of Chemistry 2017.

Nitrous oxide reductase is the enzyme that catalyses the last step of the denitrification pathway, reducing nitrous oxide to dinitrogen gas. This enzyme is a functional homodimer with two copper centres, CuA and a "CuZ centre", located in different domains. The CuA centre is the electron transferring centre, while the catalytic centre is the "CuZ centre", a unique metal centre in biology - a tetranuclear copper centre with a μ4-bridging sulphide. The enzyme has been isolated with the "CuZ centre" in two different forms, CuZ(4Cu2S) and CuZ∗(4Cu1S), with the first presenting an additional μ2-sulphur atom as a bridging ligand between CuI and CuIV of the "CuZ centre", whereas the second form was identified as a water-derived molecule. Spectroscopic analysis of CuZ∗(4Cu1S), together with computational studies, indicated that there is a hydroxide bound to CuI. Genomic analysis has identified the presence of two different types of nitrous oxide reductase, the typical and "atypical", with a single member of the last group having been isolated to date, from Wolinella succinogenes. Thus, here the structure of the "typical" nitrous oxide reductase with either CuZ(4Cu2S) or CuZ∗(4Cu1S), as well as its spectroscopic and catalytic properties, will be discussed. © The Royal Society of Chemistry 2017.

Abstract Ancient structures are part of the inheritance our elders left us. These historical inheritance needs to be preserved, so the historic structures need to be rehabilitated and restored, protecting the cultural patrimony and attending to the comfort and habitability required nowadays. In order to accomplish a good and economic rehabilitation is essential to study the behaviour of traditional structures elements (masonry and wood) in order to develop adequate assessment measures and techniques. In this context it was carried out an experimental campaign to characterize the tensile mechanical behavior of the woods from the �sequeiro� wood structure, integral part of the �Quinta de Lobeira de Cima� farm. This building from the 20th century is located in Minho, Portugal. Tensile Tests were carried out for two different species of wood, chestnut and oak. The tensile tests were performed to obtain the tensile strength parallel to the fibers, using the digital image correlation (DIC) for the extension measurement.

Glass samples with a molar composition (64+x)ZnO–(16−x)B2O3–20SiO2, where x=0 or 1, were successfully synthesized using a melt-quenching technique. Based on differential thermal analysis data, the produced glass samples were submitted to controlled heat-treatments at selected temperatures (610, 615 and 620 °C) during various times ranging from 8 to 30 h. The crystallization of willemite (Zn2SiO4) within the glass matrix was confirmed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Under specific heat-treatment conditions, transparent nanocomposite glass-ceramics were obtained, as confirmed by UV–vis spectroscopy. The influence of temperature, holding time and glass composition on crystal growth was investigated. The mean crystallite size was determined by image analysis on SEM micrographs. The results indicated an increase on the crystallite size and density with time and temperature. The change of crystallite size with time for the heat-treatments at 615 and 620 °C depended on the glass composition. Under fixed heat-treatment conditions, the crystallite density was comparatively higher for the glass composition with higher ZnO content. © 2016 Elsevier B.V.

Weathering imposes vital effects on stony monuments. Mostly, the degree of weathering is determined by simple test results, ignoring simultaneous effects of various weathering factors. Hence, the main purpose of this study is to develop prediction models with fuzzy inference systems to determine the weathering degree of the Persepolis stone, using various accelerated ageing tests in laboratory condition and to extrapolate the results to the natural condition, considering climatic information. The results suggest reliable conformity between the prediction of the weathering degree of the stone and the weathering degree observed in the Persepolis complex in natural condition.

Abstract This work addresses the determination of the cohesive law under mode I loading of bovine cortical bone tissue using the Double Cantilever Beam (DCB) test. Direct and inverse methods were proposed to assess the cohesive laws representative of bone fracture under mode I loading. The direct method combines the evolution of the strain energy release rate under mode I loading with the crack tip opening displacement that is monitored by digital image correlation technique. According to this method, the cohesive law is obtained by differentiation of such relation with respect to the crack opening. The inverse procedure is performed through a finite element analysis including cohesive zone modelling, conjointly with a developed optimization algorithm. This identification strategy does not require a pre-established shape of the cohesive law as with the conventional inverse based procedures, which is viewed as a novelty of this work. It was concluded that both methods provide consistent results, being appellative tools concerning systematic and methodical studies dedicated to bone fracture characterization.

Biodegradable polymers such as PLA have been studied for medical applications, human ligament repair is one of such cases. However, these materials can be applied in other sectors as aerospace, aeronautics, automotive, food packaging. PLA presents a relatively brittle on the mode I fracture behavior, being often blend with other biodegradable or non-degradable polymers to improve its fracture energy. For some existing applications, PLA components exhibit accumulated permanent deformation resulting from dynamic mechanical inputs, resulting on failure by laxity of parts. Aiming the improvement of PLA mechanical properties, the inclusion of carbon nanofillers into PLA matrix, in particular, CNT-COOH and GNP have been developed, due to their strong sp2 carbon-carbon bondings and their geometric arrangement that enhance mechanical properties of the polymer matrix. PLA and nanocomposites were produced by melt blending followed by compression moulding in a hot press, with small weight percentages of nanofillers added to the matrix. Nanocomposites dispersion was evaluated by SEM. Quasi static tensile tests were performed on a mechanical testing machine (Instron� ElectroPuls E1000) along with strain field measurements of specimens with centred crack with digital image correlation, revealing strain distribution along specimens.

This paper presents a control process and frequency adjustment based on the Magnetic Core Reactor prototype. For the past decades, there has been significant development in the technologies used in Wireless Power Transfer systems. In the Wireless Power Transfer systems it is essential that the operating frequency of the primary circuit be equal to the resonant frequency of the secondary circuit so there is the maximum energy transfer. The Magnetic Core Reactor allows controlling of the frequencies on both sides of the transmission and reception circuits. In addition, the assembly diagrams and test results are presented.

Fracture characterization of human cortical bone under mode II loading was analyzed using a miniaturized version of the end-notched flexure test. A data reduction scheme based on crack equivalent concept was employed to overcome uncertainties on crack length monitoring during the test. The crack tip shear displacement was experimentally measured using digital image correlation technique to determine the cohesive law that mimics bone fracture behavior under mode II loading. The developed procedure was validated by finite element analysis using cohesive zone modeling considering a trapezoidal with bilinear softening relationship. Experimental load-displacement curves, resistance curves and crack tip shear displacement versus applied displacement were used to validate the numerical procedure. The excellent agreement observed between the numerical and experimental results reveals the appropriateness of the proposed test and procedure to characterize human cortical bone fracture under mode II loading. The proposed methodology can be viewed as a novel valuable tool to be used in parametric and methodical clinical studies regarding features (e.g., age, diseases, drugs) influencing bone shear fracture under mode II loading.