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Tsipis E.V.,Technological and Nuclear Institute of Portugal | Kharton V.V.,University of Aveiro
Journal of Solid State Electrochemistry | Year: 2011

Continuing previous reviews on mixed-conducting electrodes for intermediate-temperature solid oxide fuel cells (IT SOFCs), this work presents a short overview of novel cathode and anode materials, their electrochemical performance in contact with oxygen anion- and proton-conducting solid electrolytes, and specific features determining possible applications. Priority was given mainly to recent research reports published during the last 2-5 years. Particular emphasis is focused on the relevant methodological aspects, potential limitations and drawbacks, and factors affecting electrode polarization and durability. Typical ranges of the polarization resistances, overpotentials, power densities in the cells with various current collectors, and the electrode materials total conductivity and thermal expansion are compared. The electrode compositions appraised in single-chamber and micro-SOFCs, hydrocarbon- and carbon-fueled cells, high-temperature electrolyzers, and other solid-electrolyte appliances are briefly covered in light of their similarity to the common SOFC materials discussed in the previous parts. © 2011 Springer-Verlag. Source

De la Rosa J.M.,Technological and Nuclear Institute of Portugal | Knicker H.,Institute Recursos Naturales y Agrobiologia
Soil Biology and Biochemistry | Year: 2011

In Mediterranean ecosystems, natural wildfires and prescribed burning play an important role. In order to obtain a better understanding of the impact of charcoal on the nitrogen (N) cycling in soil, 15N-enriched pyrogenic organic material (PyOM) obtained from "Lolium perenne" charred for 4min at 350°C was mixed with a typical Mediterranean agricultural soil and incubated for 72 days under controlled conditions. The main objectives were to analyze the availability of N from this material and to obtain more insight into the recalcitrance of PyOM in soils. Addition of artificially produced 15N-PyOM increased the biomass production and N retention. After 72 days of incubation time, 10% of the 15N added to the soil ( 15N add) was incorporated into new grass biomass. Solid-state 15N NMR spectroscopy revealed that at least some of this N derived from the degradation of pyrrole-type structures. Increase of the amide-N intensity in the solid-state 15N NMR spectrum of the incubated soils indicated further that some 15N from the PyOM was also incorporated into new microbial biomass. Our results confirmed a relatively low recalcitrance of N-rich PyOM. Since during its degradation, N is only slowly transferred into a plant-available form, it may contribute to the observed improvement of soil fertility by avoiding fast N losses due to leaching and volatilization as a slow N-release fertilizer. © 2011 Elsevier Ltd. Source

Vaz P.,Technological and Nuclear Institute of Portugal
Applied Radiation and Isotopes | Year: 2010

Over the last two decades, the utilization of Monte Carlo methods and techniques for modeling and simulating increasingly complex and sophisticated systems has grown at a sustained pace. This paper focuses on the applications of Monte Carlo simulation methods and techniques in the medical and nuclear energy fields, two of the sectors that impose stringent computational requirements. The prospects for the future evolution of Monte Carlo methods and techniques are addressed. Specific needs, features and capabilities are discussed. © 2009 Elsevier Ltd. All rights reserved. Source

Marques J.G.,Technological and Nuclear Institute of Portugal
Energy Conversion and Management | Year: 2010

Nuclear energy is attracting new interest around the world as countries look for low-carbon alternatives to fossil fuels to increase the diversity of their sources of energy and improve security of supply. Nuclear fission reactors provided approximately one sixth of the world's electricity needs in recent years. The vast majority of these reactors were built in the seventies and eighties. They are thus considered second generation systems, as they are based on experience gained with the first generation or prototypes built in the fifties and early sixties. Third generation reactors, developed in the nineties, are already a reality and will dominate the market in the coming decades. A significant research effort is underway on systems of the fourth generation. Better economics, improved use of natural resources, less production of radioactive waste, competitive production of hydrogen, and increased resistance to proliferation are within reach with these new systems. A review will be done on the most important features of third and fourth generation systems, together with a brief overview of the R&D challenges to be met. © 2010 Elsevier Ltd. All rights reserved. Source

Carvalho F.P.,Technological and Nuclear Institute of Portugal
Journal of Environmental Radioactivity | Year: 2011

The determination of 210Po and 210Pb was performed in marine organisms from the seashore to abyssal depths, encompassing a plethora of species from the microscopic plankton to the sperm whale. Concentrations of those radionuclides ranged from low values of about 5 × 10-1 Bq kg-1 (wet wt.) in jellyfish, to very high values of about of 3 × 104 Bq kg-1 (wet wt.) in the gut walls of sardines, with a common pattern of 210Po > 210Pb.These radionuclides are primarily absorbed from water and concentrated by phyto- and microzooplankton, and then are transferred to the next trophic level along marine food chains. Investigation in epipelagic, mesopelagic, bathypelagic and abyssobenthic organisms revealed that 210Po is transferred in the marine food webs with transfer factors ranging from 0.1 to 0.7, and numerically similar to those of the energy transfer in the marine food chains. As 210Po preferentially binds to amino acids and proteins, its transfer in food chains likely traces protein transfer and, thus, 210Po transfer factors are similar to ecotrophic coefficients. 210Pb is transferred less efficiently in marine food chains and this contributes to increased 210Po:210Pb activity ratios in some trophic levels. © 2010 Elsevier Ltd. Source

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