[en] A profile of Portugal's energy sector is presented and the energy balance (1993) in terms of oil, gas, coal, electricity and other sources is located. Topics discussed include the import of natural gas supplies from Algeria by 1996; the construction of a 400km natural gas pipeline; the breakup of the Electricidada de Portugal into separate units, and the impact of liberation and privatisation on the power sector. The first large-scale private power generation, and deregulation and competition in Portugal's oil industry are also examined in this article. (UK)

[en] Host-to-activator energy transfer efficiencies in rare-earth doped YBO_3 under vacuum ultraviolet excitation have been estimated using excitation and reflectance spectroscopy. From these data, relative electron–hole pair (e–h) trapping rate constants have been calculated for seven different lanthanide dopants. In addition, the energies of activator electronic states relative to YBO_3 band states were estimated using published empirical methods. From this, we find a correlation between e–h trapping efficiency and the energy of activator electronic states relative to YBO_3 conduction and valence band energies. - Highlights: • Relative e–h trapping rate constants are calculated for lanthanide dopants in YBO_3. • Dopant energy levels are estimated relative to the valence and conduction bands of YBO_3. • Dopants are classified as hole traps or electron traps. • A correlation between trapping efficiency and the energy of dopant trap is observed

[en] The effect of inorganic lead on two functions of cerebral microvessel endothelium, cell division and glucose analog uptake, was investigated. Lead concentrations considered to be toxic in humans inhibited both functions in cultured endothelial cells. Both effects were dependent on the length of lead exposure and dose over the range of 10(-4) to 10(-6) M lead acetate. After 4 days of exposure there were 76% fewer cells in 10(-4) M lead-exposed cultures relative to control cultures. After 4 days of exposure to 10(-5) M lead there were 55% fewer cells, and after 10(-6) M lead exposure there were 15% fewer cells. Two days after 10(-4) M lead exposure [methyl-3H]thymidine incorporation into endothelial cells was inhibited by 71%. Incorporation was inhibited 47% by 10(-5) M lead but 10(-6) M lead did not inhibit incorporation after 2 days of exposure. Glucose analog uptake was inhibited in both contact-inhibited and log-phase cells; however, the latter were more sensitive to lead and this increased sensitivity correlated with a higher lead content in this cell population. Both the specific carrier-mediated and the nonspecific components of glucose analog uptake were inhibited by exposure of the endothelial cells to lead. A lead exposure of 40 min produced a significant effect on the uptake mechanism. In order to manifest its effects the lead had to be present in serum-containing medium, suggesting that some serum component was necessary to present the lead to the endothelial cells. These findings imply that the initial target of inorganic lead in the CNS may be the plasma membrane of the capillary endothelial cells, and that lead may act by altering the physiological function of these membranes

[en] Coral microatolls allow for the reconstruction of relative sea level (RSL) and the inference of tectonic deformation along tropical coastlines over the Holocene. Microatolls track RSL with unparalleled vertical precision, and their annual banding allows us to count years precisely over an individual coral’s lifetime; however, RSL histories reconstructed from multiple corals depend on accurate and precise radiocarbon (14C) or uranium-thorium (230Th) ages. We collected coral microatoll slabs from sites in Ilocos Region, northwestern Luzon, Philippines, and dated them with 14C and 230Th techniques. Notably, initial RSL reconstructions for some sites disagreed markedly depending on the dating technique used. Attempts to replicate geochronologic analyses have shown that the coral skeletons are susceptible to diagenesis, complicating efforts to accurately determine coral ages. We are developing a strategy to overcome this limitation. We extracted multiple samples from each microatoll slab for paired 14C and 230Th dating. The number of annual bands separating any dated sample was used to further constrain the age of the coral; by subtracting the number of years from each dated sample, samples taken from different parts of the slab can produce independent estimates of the outermost preserved band. After excluding anomalously young replicate 14C ages and samples flagged as partly calcified by x-ray diffraction, we find that 230Th ages from a single coral disagree at 4σ in 4 of 8 cases, whereas calibrated 14C dates overlap at 2σ in 8 of 9 cases for an arbitrary radiocarbon marine reservoir correction, ∆R = 0 yr. Using OxCal and the Marine20 calibration curve, we apply Bayesian statistics to combine 14C and 230Th ages, to estimate ∆R, and to determine the coral ages using the best available data. We further analyze the ∆R value for each coral, and account for overdispersion and underdispersion, whilst generating a ∆R value per site, and an overall ∆R value (inclusive of all sites). We find no statistically significant difference in ∆R for each site, and we calculate an overall ∆R of -155 ± 117 yr for sites in Ilocos Region since the mid-Holocene, though century-scale variability in ∆R may occur. Additionally, to improve the reliability of our dates, our final dating strategy in OxCal is to apply the previously determined ∆R, to a code that places the corals in sequence (based on precise elevation measurements, morphological similarities, and coral die-down events), along with the 14C dates that are dated to the outermost preserved band.

[en] Highlights: • Performance decreases with uneven cross-flow in higher channel length ARs. • Smaller performance change due to uneven cross flow than in experiment. • Neutron radiography indicates more water buildup in high AR than low AR. • Liquid water handling probable cause of majority of performance variation. • Significant interaction between channel AR and stoichiometry for system performance. - Abstract: The goal of this study was to determine the main cause of performance improvement in decreasing aspect ratio interdigitated flow fields, where aspect ratio is the channel length to width ratio. An experimental test cell with an interdigitated flow field operated under various aspect ratios found increasing net power densities with decreasing aspect ratio, after accounting for parasitic pump losses. In-situ neutron radiography found there was more water present in high aspect ratio flow field designs than in low aspect ratio designs. It also found more water in the 1.5/2 stoichiometry conditions than in the 2/4 stoichiometry conditions further indicating liquid water is a probable cause of performance changes. A single phase model used to determine the difference in power from the changing distribution of cross flow found decreasing aspect ratio resulted in higher overall performance. The experiment had significantly greater losses in power density with increasing aspect ratio, indicating liquid water removal was the major contributor to the improvement in net power density rather than the distribution of cross flow. Designers of PEMFCs should use a low aspect ratio design for interdigitated flow fields, or include a water removal mechanism for situations where high aspect ratio is required.