Air density influence on the strength of external insulation underpositive impulses: experimental investigation up to an altitude of 3000m a.s.l

Research carried out to investigate the dependence of the strength of external insulation on air density is described, with particular reference to positive polarity impulses, generally of major interest for design and testing. New tests were carried out up to an altitude of about 3000 m above sea level, with particular attention to the influence of air density on the strength and on the discharge process. It was found that, for positive switching impulses, the variation of the breakdown voltage with air density is more marked at lower density values. It is noted that this trend is not fully taken into account by current correction methods. A refined correction approach is proposed to account for the above-mentioned aspects, with special attention to high altitudes     

Network reliability assessment using a cellular automata approach

Two cellular automata (CA) models that evaluate the s–t connectedness and shortest path in a network are presented. CA based algorithms enhance the performance of classical algorithms, since they allow a more reliable and straightforward parallel implementation resulting in a dynamic network evaluation, where changes in the connectivity and/or link costs can readily be incorporated avoiding recalculation from scratch. The paper also demonstrates how these algorithms can be applied for network reliability evaluation (based on Monte-Carlo approach) and for finding s–t path with maximal reliability.     

Technical note The application of selective principal components analysis (SPCA) to a Thematic Mapper (TM) image for the recognition of geomorphologic features configuration

Selective principal components analysis (SPCA) has been applied to highly- and/or little-correlated subgroups of bands. Its usefulness was demonstrated in two ways. First, the final result is a false colour composition based on the first order principal component of each highly correlated subgroup of bands, the resulting image containing more than 95 per cent of the total variance of the six TM bands used. Secondly, the second order principal component of pairs of little-correlated bands will show the information that is unique for each band. Both types of analysis have been applied to characterize the geomorphological units at a site in SW Spain. Both methodologies have demonstrated to be very useful in a difficult to access area, with high vegetation diversity covering quite different geomorphic features.     

Sensitivity of fire occurrence to meteorological variables in Mediterranean and Atlantic areas of Spain

Wildland fires are common in most areas of Spain, even in areas with a mesic climate. Weather plays a crucial role in fire, but the relationship between fire incidence and meteorological variables is not usually strong. Assessing the relationship between meteorological variables and fire from the recent past can eventually aid in evaluating fire risk in future climate scenarios. In this paper we report on the relationships between the number of fires and the surface burned per year and several yearly temperature and precipitation variables for three areas of Spain: North, Central and the Levant. The three areas differ in their climate as well as in the ignition sources. We used the fire records from 1974 to 1988. The relationships between meteorological and fire variables was tested by least square simple regression models. Our results show that some of the meteorological variables used are good predictors of either number of fires or surface burned in all three areas. The northern area was better related to meteorological variables than the Levant. Fire occurence in the northern and central areas was mainly related to temperature variables whereas in the Levant it was related to precipitation variables. Fires caused by pasture burning or by lightning had less relationship to meteorological variables than those caused accidentally. Fires caused by arsonists were very highly related to meteorological variables in all three areas. Fires caused by unknown sources had a similar pattern of relationships to that found for arsonist-caused fires. Our study indicates that the degree of relationship between meteorological variables and fire occurence may be related to the current climate and weather patterns of a given area.     

Trace element levels in whole blood samples from residents of the city Badajoz, Spain.

Copper, lead, cadmium, and zinc were determined by anodic stripping voltammetry after sample digestion and potentiometric stripping analysis was used for Pb and Cd determination in original samples. Selenium was determined by cathodic stripping voltammetry or hydride generation AAS. Element levels found in the whole blood sample in a group of 82 people are for Cd: 0.98 +/- 0.94 ng/ml; for Pb: 46.7 +/- 28.6 ng/ml; for Cu: 1.07 +/- 0.12 micrograms/ml; for Zn: 6.95 +/- 1.08 micrograms/ml, and for Se: 116 +/- 25 ng/ml. Analytical data have been correlated to age, sex, smokers or non-smokers, drinking and food habits.     

Phytoremediation potential of willow trees for aquifers contaminated with ethanol-blended gasoline

Ethanol-blended gasoline has been used in Brazil for 20 years and, probably, is going to be more widely used in North America due to the MtBE environmental effects on groundwater. The potential impacts caused by the presence of ethanol in UST spills are related to the co-solvency effect and the preferential degradation of ethanol over the BTEX compounds. These interactions may increase the length of dissolved hydrocarbon plumes and the costs associated with site remediation. This study investigates the advantages of phytoremediation to overcome the problems associated with the presence of ethanol in groundwater contaminanted with gasoline-ethanol mixtures. Experiments were performed under lab conditions with cuttings of Willow tree (Salix babylonica) cultivated hydroponically. Results showed that the cuttings were able to reduce ethanol and benzene concentrations by more than 99% in less than a week. The uptake of both contaminants was confirmed by blank controls and was significantly related to cuttings transpiration capacity. Sorption onto roots biomass also markedly affected the behavior of contaminants in solution. Experiments to evaluate plants' toxicity to ethanol indicated that plants were only affected when aqueous ethanol concentration reached 2000mgl(-1). Results suggest that phytoremediation can be a good complement to intrinsic remediation in shallow aquifer sites contaminated with ethanol-blended gasoline spills.     

The spatial and temporal variations in PM10 mass from six UK homes

People spend the majority of their time indoors mostly in the domestic environment, where their health may be effected by significant airborne particulate pollution. The indoor/outdoor air quality at six homes in Wales and Cornwall was investigated, based on different locations (urban, suburban, rural) and household characteristics (smokers, non-smokers). The spatial and temporal variations in PM10 mass were monitored for a calendar year, including ambient weather conditions. The activities of individuals within a household were also recorded. Monitoring of PM10 took place inside (kitchen, living room, bedroom) homes, along with concomitant collections outdoors. Samples were subjected to gravimetric analysis to determine PM10 concentrations and examined by scanning electron microscopy to identify the types of particles present on the filters. The results of the study show there are greater masses of PM10 indoors, and that the composition of the indoor PM10 is controlled by outdoor sources, and to a lesser extent by indoor anthropogenic activities, except in the presence of tobacco smokers. The indoor and outdoor PM10 collected was characterised as being a heterogeneous mixture of particles (soot, fibres, sea salt, smelter, gypsum, pollen and fungal spores).     

Structural changes in sardine (Sardina pilchardus) muscle during iced storage: Investigation by DRIFT spectroscopy

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy has been used for the first time to evaluate the postmortem changes in structure of components from sardine muscle in relation to quality loss. Sardines (Sardina pilchardus) were stored in ice for up to thirteen days. The spectroscopic study was focussed on the structural changes produced on the lipids and proteins.