Heat capacity measurements on h.c.p. solid solutions of lanthanum in gadolinium have been performed in an adiabatic calorimeter over a wide temperature range, and the temperature-dependence of the ferromagnetic transition of Gd by alloying with La has been evaluated.
The lattice parameters of HgxBa2O4+δ were determined by X-ray powder diffraction as a function of temperature from 10 to 310 K. The fitting of the parameters yielded the thermal expansion coefficients of the superconducting oxide and demonstrated the anisotropy characteristics of the polycrystalline material. The effect of the irreversible loss of Hg on the lattice parameters is reported.
Mixed LaREO3 (RE ≡ Dy, Ho, Er, Tm, Yb, Lu) and NdGdO3 oxides were prepared by thermal decomposition of the corresponding co-precipitated mixed oxalates. The decomposition of La/RE and Nd/Gd oxalates was studied by means of differential thermal analysis and thermogravimetric (DTA-TG) measurements; in particular the last step, consisting of the loss of a CO2 molecule from the corresponding oxycarbonate, has been thoroughly investigated, as it is particularly interesting for the study of the formation temperature of mixed rare earth oxides. After the release of CO2, the oxides crystallize in a distorted perovskitic cell or one of the structures typical of rare earth sesquioxides, depending on the cationic size difference and on the average cationic radius. The mixed rare earth oxycarbonate decomposition has been studied in comparison to the decomposition of single rare earth oxycarbonates. A trend of the mixed oxides formation temperature as a function both of the average cationic size and of the cationic sizes difference has been observed and compared to the behaviour of single rare earth oxides.
This paper presents and discusses a new bibliometric indicator of research performance, designed with the fundamental concern of enabling cross-disciplinary comparisons. The indicator, called x-index, compares a researcher's output to a reference set of research output from top researchers, identified in the journals where the researcher has published. It reflects publication quantity and quality, uses a moderately sized data set, and works with a more refined definition of scientific fields. x-index was developed to rank researchers in a scientific excellence award in the Faculty of Engineering of the University of Porto. The data set collected for the 2009 edition of the award is used to study the indicator's features and design choices, and provides the basis for a discussion of its advantages and limitations.
Authors:G. A. Costa, E. A. Franceschi and A. Tawansi
Electrical resistivity, magnetic susceptibility, X-ray diffraction and differential thermal analysis have been performed over a wide temperature range on binary compounds RCu. Melting points or decomposition temperatures for RCu (R=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy) phases and a number of FeB-CsCl structural transitions are reported, and heats and entropies of transformation are evaluated. Large hysteresis effects are observed for the structural transformations at different temperatures.
Authors:J. Rodrigues Silva, A. de Melo Ferreira and A. da Costa
The biosorption of uranium by the seaweed Sargassum filipendula was investigated under dynamic conditions at various bed heights. Our results indicate that a bed height of 40.0 cm (111.9
g biomass) was the most efficient for long-term operation of the continuous system. Our results also indicate that the effluent
solutions produced are in accordance with Brazilian legislation for safe discharge of uranium in aqueous streams. The efficiency
of the process increased with an increase in bed height from 5.0 to 40.0 cm due to changes in the transfer zone. In treatment
of a real effluent contaminated with uranium, stable heavy metals and essential metals, 64% of the uranium was biosorbed,
as well as the stable heavy metals chromium, lead and barium. The essential metals calcium, magnesium, iron and manganese
were not biosorbed by the seaweed, in fact, their concentrations in the solution increased due to ion-exchange mechanisms
with the constituent polysaccharides of the biomass. Another important result was the 85–87% reduction of mass obtained after
drying and calcination of the biomass. This is a relevant indication that long-term storage of biomass loaded with radionuclides
and heavy metals is possible after concentration of the contaminants. In the present work, the reduction in total mass of
the loaded biomass was considerable, thus facilitating storage of the contaminated seaweed.
Authors:Márk Váczi, A. Costa, L. Rácz and J. Tihanyi
This study compared two training regimens in which knee extensor exercises were performed at different range of motion.
Sixteen males performed bouts of 90 maximal isokinetic eccentric contractions over 6 consecutive days (B1-B6) at either small (n=8) or large (n=8) range of motion. Average of peak torque (Mp) of each of the 90 contraction trials were calculated, plasma creatine kinase (CK) and lactate dehydrogenase (LDH) activities were measured before, 24 h, 48 h and 6 d after B1. Muscle soreness was evaluated every day during the experiment.
At B3 Mp reduced more in group L than in group S. From B1 to B6 group S increased Mp, while in group L Mp did not return to the baseline level. In both groups CK activity elevated 24 h following B1. CK activity was significantly higher in group L 6d after B1. In group L muscle soreness was higher at 48 h, 72 h, 4 d and 5 d after B1.
High-intensity, consecutive eccentric knee extensor exercise training at large range of motion may induce greater development of muscle damage and force deficit, than training at small range of motion. Training at small range of motion may induce early adaptation in voluntary torque production.
Authors:Chiara M. Franceschi, Giorgio A. Costa and Enrico Franceschi
It is well known, from ancient Egypt, that some pigments and colourants can change with time for light effect or chemical attack. Cennino Cennini in the fifteenth century in his book “Il libro dell'arte o trattato della pittura” describes the use of many pigments and their degradation. He was aware of the problems and was able to suggest the answers in the use of pigments on several supports, but he could not understand the physical–chemical reason of the alteration processes. In this study, we point out the aging effects in seven paintings, practically of the same period (1650–1655). We considered in particular green, white and blue pigments of the palette of Valerio Castello. About 150 spots were selected on works painted on four different supports, canvas, wood panel, copper and slate. For each point, several determinations were carried on the pigments and decomposition products, aiming to determine the state of conservation of the paintings, the nature of the pigments, their alteration and if the support can affect the kinetics of degradation.
Authors:J. Canotilho, F. Costa, A. Sousa, J. Redinha and M. Leitão
Enthalpies of solution of various terfenadine samples in methanol and in ethanol were measured. Samples were prepared by crystallization in different solvents. The calorimetric results give important information on crystal structure of the terfenadine forms and on the solute/solvent interactions of this compound with the solvents.