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The aim of this research was to test whether there is an inherent difficulty in understanding prohibition signs rather than obligation signs. In the experiment conducted, participants decided whether simple car movements presented on a computer screen were allowed or not according to either obligation or prohibition traffic signs. The information provided by obligation and prohibition signs at a T-junction can be understood as messages in the form: A "mandatory left turn" sign indicates that turning right is not allowed, the same as a "no right turn" sign. Both statements mark each of the relevant roads as "allowed" and "not-allowed" in exactly the same way. However, reasoning studies suggest dramatic differences in behaviour. Previous research showed a general advantage for obligation signs. In this study, the number of alternative roads indicated by these two kinds of traffic sign was controlled using different crossroad junctions. In those particular conditions, our results showed that there is no overall advantage for either obligation or prohibition signs. It depends on the manoeuvre performed by the vehicle. Obligation signs produce faster responses when the manoeuvre is allowed, whereas prohibition signs show faster reaction times when the manoeuvre is not allowed. Those results obtained with diagrammatic information are consistent with some cognitive theories, such as the mental model theory about reasoning with deontic propositions. (Contains 3 figures and 1 table.)

A comparative analysis of voltage control, frequency regulation and system restoration services provided in England, Wales, Nordic Countries, California, Argentina, Australia and Spain, is presented.

The business opportunities in electricity distribution networks are examined. In this context the incentives of the incumbent distribution company are compared with those of new entrants. The need to change the present regulations relating to electricity distribution is highlighted, as it would benefit even the end users.

The current and voltage harmonic spectrum, and power factor in gas discharge lamps: Sodium (Na)-high pressure and Mercury (Hg) in actual use in public street lighting have been measured. A sample of nearby 360 gas discharge lamps (Na, Hg) of different rated power was obtained by simple random sampling over a universe of approximately 15,000 lamps. An 'equivalent' current harmonic spectrum for gas discharge lamps is proposed, which is independent of the type of gas and the lamp rated power. This current spectrum can be used to integrate gas discharge lamp models for harmonic distortion level assessment in distribution networks. The relation of this equivalent current harmonic spectrum with: i) lamp voltage waveform, ii) type of lamp (Na, Hg), and iii) power factor-capacitor lamp, is analyzed.

The functional properties of two types of barium strontium titanate (BST) thin film capacitor structures were studied: one set of structures was made using pulsed-laser deposition (PLD) and the other using chemical solution deposition. While initial observations on PLD films looking at the behavior of Tm (the temperature at which the maximum dielectric constant was observed) and Tc* (from Curie-Weiss analysis) suggested that the paraelectric-ferroelectric phase transition was progressively depressed in temperature as BST film thickness was reduced, further work suggested that this was not the case. Rather, it appears that the temperatures at which phase transitions occur in the thin films are independent of film thickness. Further, the fact that in many cases three transitions are observable, suggests that the sequence of symmetry transitions that occur in the thin films are the same as in bulk single crystals. This new observation could have implications for the validity of the theoretically produced thin film phase diagrams derived by Pertsev et al. [Phys. Rev. Lett. 80, 1988 (1998)] and extended by Ban and Alpay [J. Appl. Phys. 91, 9288 (2002)]. In addition, the fact that Tm measured for virgin films does not correlate well with the inherent phase transition behavior, suggests that the use of Tm alone to infer information about the thermodynamics of thin film capacitor behavior, may not be sufficient. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Ba0.5Sr0.5TiO3 (BST) thin-films with various thicknesses and different strain conditions were made using pulsed laser deposition and characterized by x-ray diffraction. No phase-transition was found for the in-plane compressed BST films, on the contrary more phase transitions were observed on the stress-free BST films.

A modification to the Jiles-Atherton hysteresis model makes it possible to model magnetic effects of plastic deformation. With this model, it is shown how a narrow hysteresis with an almost steplike hysteresis curve for an undeformed specimen is sharply sheared by plastic deformation.

The natural attenuation of oil spill contaminated soils, with different exposure times, in Patagonian environment was evaluated by the use of several parameters to quantify the degree of changes in the composition. Column (CC) and gas chromatography (GC); UV-visible and 1H NMR techniques were used to determine compositional and structural indexes. The results show that the nC18/Phytane GC index, that was 1.5 for crude oil, decreased with exposure time to values between 0.97-0.17 in the residues. The percentages for the four aliphatic (H1 - H4) and the aromatic (HA) proton types, determined by 1H NMR, were: 12.9-34.4 (H1), 43.3-60.2 (H2), 4.24-24.2 (H3), 1.33-17.9 (H4), and 0.44-4.81 (HA), in crude oil and residues, respectively. Furthermore, the characterization of significant 1H NMR signals indicated the presence of carboxylic acid hydrogens in the polar fraction of the crude oil and of residues of two years age. The Principal Components Analysis (PCA) of the parameters determined by CC, GC and NMR showed that the first three principal components (1st, 2nd, and 3rd PC), accounted for more than 84% of variance. The 1st PC is largely influenced by H3, H1, H4, H2, and the nC18/Phytane GC parameter, in the order given. The evaluation of the different parameters by PCA suggests that 1H NMR is more useful than GC to evaluate the degree of the chemical transformations of oil spills in soils [ABSTRACT FROM AUTHOR]

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This article presents an update on a report by the U.S. Centers for Disease Control focusing on an outbreak of mumps, initiated in Iowa in 2005. This outbreak had spread to ten additional states by May, 2006. A summary of the preliminary data from the original article is presented concerning the progression of the outbreak across state lines, and updated recommendations for the control of the virus during the outbreak are also provided. The author suggests employing multiple doses of vaccines during an outbreak, especially for individuals born before 1957, with no previous history of vaccination.

A review is given of ceramic and single-crystal thin film ferroelectric oxides, emphasizing perovskite phases, together with some new developments on hafnia films. It is shown that single-crystal barium titanate films behave as bulk down to at least 77 nm, with no finite size effects, no phase transition temperature shifts, and no dielectric peak broadening or change from first- to second-order transitions, suggesting that the gradient defect model of Bratkovsky and Levanyuk correctly describes such effects as extrinsic in experimental studies of equally thin ceramic thin films. In ceramic barium–strontium titanate (BST) thin films, it is shown that there is also no intrinsic broadening or shifts in phase transitions, with sharp, unshifted, bulk-like transitions observed only as re-entrant upon warming from cryogenic temperatures; this shows that phase transitions in ceramic thin films are dominated by kinetics and not thermodynamics and are definitely not equilibrium measurements. At high fields (>1 GV/m), the films exhibit space charge-limited conduction; no variable-range hopping is observed, contrary to recent studies on SrTiO3. Some novel, unconventional switching processes are discussed, comparing the “perimeter effect” (non-equilibrium, ballistic) with Molotskii's equilibrium model. Theory and experiment are described for [3D] nanotubes, nanorods, and nano-ribbons (or micro-ribbons). The layered-structure-perovskite–pyrochlore conversion in bismuth titanate is described together with the PbO+TiO2 phase separation in lead zirconate titanate during electrical breakdown, as are novel HfO2 precursors that demonstrate enhanced temperature crystallization from the amorphous state and hence commercial advantages for front-end processing. [ABSTRACT FROM AUTHOR]

We invoke the onset of dislocations along the BaTiO3-SrTiO3 interface as reported by Wunderlich et al. to explain the non-monotonic behaviour of the dielectric permittivity as a function of superlattice periodicity and the less than four-fold in-plane symmetry at the dielectric maximum. At a periodicity of about 10/10, depending on composition and growth mechanism, several groups report a maximum of dielectric permittivity. In addition to that we observe in-plane symmetry less than tetragonal for 10/10 superlattices by HR-XRD, in contrast to initial low-resolution data from Tabata et al. thus challenging the assumption of unrelaxed strain all the way through the superlattice. The aim of this article is to link both effects to the increasing volume fraction of conducting layers close to the interface in series with the superlattice layers. [ABSTRACT FROM AUTHOR]

The low-temperature phase of TIH[sub 2]PO[sub 4] has been studied by X-ray diffraction. A structural model is proposed with space group P&1macr;. This model is compared with the structure of the antiferroelectric phase of TlD[sub 2]PO[sub 4] at room temperature to analyze the expected isomorphism at low temperature. Given the structural distortion of TlH[sub 2]PO[sub 4], such isomorphism present in the common high-temperature phase is not recovered in this phase. Through the analysis of the displacements of the PO[sub 4] groups there is some evidence that the ordering of the H atoms responsible for the appearance of antiferroelectricity seems to be incomplete. An exhaustive study of the detected ferroelastic domains is also performed. [ABSTRACT FROM AUTHOR]

Determines the equilibrium aqueous concentration and the distribution coefficients in soil samples containing oil residuals of different age. Dependence of residual behaviors on the co-solvent fraction and the age of the oil spill; Details on the modeling of environmental impact on polluted soils; Variation of polynuclear aromatic hydrocarbons concentrations in soils and sediments.