Wet deposition of polychlorinated biphenyls in the eastern Mediterranean

The concentrations of polychlorinated biphenyls (PCBs) were measured in rain samples collected from a semiurban and a marine background site of the eastern Mediterranean. The concentration of sigmaPCB (sum of 54 PCB congeners) in the city of Heraklion (2.9 +/- 1.9 ng L(-1)) was not significantly higher than the corresponding concentration measured at the background sampling station of Finokalia (1.9 +/- 0.9 ng L(-1)). In both sites, the sum of tri- and tetrachlorinated congeners accounted for more than 55% of sigmaPCB in rainwater. For all samples, the percentage of particle-bound PCBs ranged between 6.6% and 63.8%, providing an average value of 31 +/- 18%. The washout ratios of particulate PCBs (WP) were constant for individual congeners regardless the degree of chlorination. Average WP values ranged between 1.9 x 10(5) and 5.2 x 10(5) while a value of 2.7(+/- 1.3) x 10(5) was deduced for sigmaPCB. The corresponding washout ratios for gaseous PCBs were substantially lower and ranged between 7 x 10(3) (PCB 99) and 1.3 x 10(5) (PCB 180). Washout ratios of gaseous PCBs were also calculated based on Henry's law, and they were found to be 30-920 times lower than those obtained from field measurements. On the basis of our data, the wet deposition flux of sigmaPCB in the eastern Mediterranean should approach 820 ng m(-2) yr(-1). This flux is similar with the values recently reported for several background sites of the United States and Europe, but it is 1 order of magnitude lower than the flux of PCBs measured in the western Mediterranean 16 yr ago.     

Contribution of biomass burning to atmospheric polycyclic aromatic hydrocarbons at three European background sites

Radiocarbon analysis of atmospheric polycyclic aromatic hydrocarbons (PAHs) from three background areas in Sweden, Croatia, and Greece was performed to apportion their origin between fossil and biomass combustion. Diagnostic ratios of PAHs implied that wood and coal combustion was relatively more important in the northern European site, while combustion of fossil fuels was the dominant source of PAHs to the two central-southern European background sites. The radiocarbon content (delta14C) of atmospheric PAHs in Sweden ranged between -388 per thousand and -381 per thousand, while more depleted values were observed for Greece (-914 per thousand) and Croatia (-888 per thousand). Using a 14C isotopic mass balance model it was calculated that biomass burning contributes nearly 10% of the total PAH burden in the studied southern European atmosphere with fossil fuel combustion making up the 90% balance. In contrast, biomass burning contributes about 50% of total PAHs in the atmosphere at the Swedish site. Our results suggest that the relative contributions of biomass burning and fossil fuels to atmospheric PAHs may differ considerably between countries, and therefore, different national control strategies might be needed if a further reduction of these pollutants is to be achieved on a continental-global scale.     

Development of [60] fullerene supported on silica catalysts for the photo-oxidation of alkenes

Simple or successive incipient wetness impregnation followed by heating at 180 °C is proved an efficient preparation method for dispersing effectively onto the silica surface various amounts of C₆₀ in the range 1–4% (w/w). BET, XRD, DRS, TGA, microelectrophoresis and photoluminescence have been used to characterize the photocatalysts prepared. A high dispersion was obtained for the quite stable supported C₆₀ phase, comprised mainly from relatively small or medium size C₆₀ clusters/aggregates. The photocatalytic activity was assessed in the singlet oxygen oxidation of alkenes by examining the photo-oxygenation of 2-methyl-2-heptene as a probe reaction. The catalytic tests were carried out at 0–5 °C in CH₃CN, under oxygen atmosphere and using a 300 W xenon lamp as the light source. The heterogeneous catalysts obtained were proved to be active in the photocatalytic oxidation of olefins via a ¹O₂ ene reaction. The catalysts exhibited significant conversion, turnover number and turnover frequency values, substantially higher than those achieved over the unsupported C₆₀. The conversion increases with the amount of the supported C₆₀ up to a value equal to 3% (w/w) and then it decreases whereas turnover number and turnover frequency decreases monotonically as the amount of the supported C₆₀ increases. The easy separation of these solid catalysts from the reaction mixture, the high activity and stability as well as the retained activity in subsequent catalytic cycles, make these supported catalysts suitable for a small-scale synthesis of fine chemicals.     

MeteoBayes: Effective Plan Recognition in a Weather Dialogue System

When you've called a voice portal for any kind of information retrieval, chances are that an automated system guided the entire interaction. It might have correctly identified your goal, but probably only after asking too many questions. MeteoBayes is a meteorological information dialogue system that lets you use natural language to direct the interaction. Based on Bayesian networks, MeteoBayes' inference engine attempts to identify user intentions by consulting its past dialogue repository. For unfamiliar words, MeteoBayes has an unknown-term disambiguation module that learns word similarities from texts to avoid unnecessary system inquiries, thus speeding up the understanding process     

Business Process Modelling and Design — A Formal Model and Methodology

This paper presents a formal framework for representing enterprise knowledge. The concepts of our framework (objectives and goals, roles and actors, actions and processes, responsibilities and constraints) allow business analysts to capture knowledge about an enterprise in a way that is both intuitive and mathematically formal. It also outlines the basic steps of a methodology that allows business analysts to go from high-level enterprise objectives, to detailed and formal specifications of business processes that can be enacted to realise these objectives. The formal language used means that the specifications can be verified as having certain correctness properties, e.g. that responsibilities assigned to roles are fulfilled, and constraints are maintained as a result of process execution.