The multicopper enzyme nitrous oxide reductase (N2OR) catalyzes the final step of denitrification, the two-electron reduction of N2O to N-2. This enzyme is a functional homodimer containing two different multicopper sites: CuA and CuZ. CuA is a binuclear copper site that transfers electrons to the tetranuclear copper sulfide CuZ, the catalytic site. In this study, Pseudomonas nautica cytochrome C-552 was identified as the physiological electron donor. The kinetic data show differences when physiological and artificial electron donors are compared [cytochrome vs methylviologen (MV)]. In the presence of cytochrome c(552), the reaction rate is dependent on the ET reaction and independent of the N2O concentration. With MV, electron donation is faster than substrate reduction. From the study of cytochrome c(552) concentration dependence, we estimate the following kinetic parameters: K-mc512 = 50.2 +/- 9.0 mu M and V-maxc551 1.8 +/- 10.6 units/mg. The N2O concentration dependence indicates a K-mN2O of 14.0 +/- 2.9 mu M using MV as the electron donor. The pH effect on the kinetic parameters is different when MV or cytochrome c(552) is used as the electron donor (pK(a) = 6.6 or 8.3, respectively). The kinetic study also revealed the hydrophobic nature of the interaction, and direct electron transfer studies showed that CuA is the center that receives electrons from the physiological electron donor. The formation of the electron transfer complex was observed by H-1 NMR protein-protein titrations and was modeled with a molecular docking program (BiGGER). The proposed docked complexes corroborated the ET studies giving a large number of solutions in which cytochrome c(552) is placed near a hydrophobic patch located around the CuA center.

The electron transport in n-type polycrystalline zinc oxide, nanocrystalline Zinc-Gallium-Oxygen and amorphous Indium-Zinc-Oxygen systems produced by rf magnetron sputtering at room temperature, under different oxygen partial pressure were investigated. It was found that the carrier transport is not band tail limited, being governed by metal cations irrespective to the film's structure. The highest net room temperature electron mobility was achieved on the amorphous films and noticed that for the single component oxides the mobility decreases as the carrier concentration increases, while the reverse behaviour was observed for the multicomponent oxides, independently of their structure. These behaviours are related to the role that negative charge defects in excess of 1010 cm- 2 generated on multicomponent oxides have on carriers scattering and so on their electronic performances. © 2007 Elsevier B.V. All rights reserved.

This paper describes a novel colorimetric method for detection of nucleic acid targets in a homogeneous format with improved sensitivity by means of a system based on the combination of a tunable monochromatic light source and an amorphous/nanocrystalline silicon photodetector that detects color and light intensity changes undergone by samples/assays containing tailored gold nanoparticles probes. This new low cost, portable, fast and simple optoelectronic platform, with the possibility to be re-used, permits detection of at least 400 fentomole of specific DNA sequences without target or signal amplification and was applied to the rapid detection of human pathogens in large variety of clinical samples such as Mycobacterium tuberculosis. © 2008 Elsevier B.V. All rights reserved.

Portugal has been providing dinosaur remains since, at least, 1863. The 18th century tiles depicting the legend of Our Lady in Cabo Espichel are probably the oldest known dinosaur track illustration. To our knowledge, the first remains found in Portugal were theropod teeth collected near Porto das Barcas (Late Jurassic of Lourinhã) in June 20th, 1863 by the geologist Carlos Ribeiro (1813-1882). The first dinosaur paper was written by Henri Sauvage (1842-1917) published in 1896. All remains collected since 19th century were gathered in a work signed by Albert de Lapparent (1905-1975) and Georges Zbyszewski (1909-1999 ) titled Les Dinosauriens du Portugal (1957) that was a significant milestone in the Portuguese dinosaur paleontology and gives the state-of-the-art by the time. Several dinosaurs are named, described, depicted and mapped in that monograph. The first track record is given by Jacinto Pedro Gomes (1844-1916) in 1916. Concerning the non-scientific literature referring to dinosaurs, in 1884 the newspaper Occidente reports the Bernissart findings in Belgium. In the 1959 occurs the first visit to Portugal of Walter Kühne (1911-1991) from the Free University of Berlin. Further visits and work granted the access to the Guimarota Mine and other Late Jurassic deposits in the 1960’s, 70’s and 80’s with a high number of publications. In the 1980’s and early 1990’s starts a progressive era for dinosaur paleontology in Portugal with the works of Peter Galton, Miguel Telles Antunes, the Natural History Museum, the Museum of Lourinhã and the New University of Lisbon, Oliver Rauhut, and others.

In this work, the mechanical characterization of ceramic products processed from red clay with different amounts of added coal fly ash was investigated. Coal fly ash produced by power plants is a waste material that constitutes an alternative source of minerals for the production of traditional building ceramics, as it is a complex mixture of several oxides such as SiO2, Al2O3, CaO, Fe2O3, Na2O, TiO2, which are usually present in the composition of such ceramics. A powder technology and firing route was followed for the processing of the clay and coal fly ash based ceramics. Different proportions of waste (10, 25 and 50%, by weight) were added to red clay, and then the mixed powders were pressed to form compacts that were fired at a selected temperature in the range 850-1,150°C. The effects of waste content and of heating conditions on the microstructure and mechanical characteristics of the obtained materials were investigated. The density, porosity, water absorption, flexural strength, hardness and fracture toughness of the produced materials were evaluated. A comparison was made between the properties of the produced ceramics with those of traditional ceramic materials used in construction, e.g. floor or wall tiles, and it was observed that the clay based products with coal fly ash additions may be used in similar applications. © 2007 Springer Science+Business Media B.V.

The paper presents the properties of zinc oxide thin films deposited on glass substrate via dip-coating technique. Zinc acetate dehydrate, ethanol and monoethanol amine were used as starting materials and N2 gas was used as thermal annealing atmosphere for film crystallization. The effect of withdrawal speed on the crystalline structure, morphology, zinc and nitrogen chemical states, optical, electrical and gas-sensing properties of the thin films has been investigated using X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, optical transmittance and photoreduction-ozone reoxidation data. © 2007 Elsevier B.V. All rights reserved.