A unified multimedia and semantic perspective for data retrieval in the semantic web

In recent years, the emerging diffusion of peer-to-peer networks is going beyond the single-domain paradigm like, for instance, the mono-thematic file sharing one (e.g. Napster for music). Peers are more and more heterogeneous data sources which need to share data with commercial, educational, and/or collaboration purposes, just to mention a few. Moreover, in current information processing applications data cannot be meaningfully searched by precise database queries that would return exact matches (e.g. when dealing with multimedia, proteomic, statistical data).     

Comparative study of humic acids flocculation with chitosan hydrochloride and chitosan glutamate

Flocculation of dissolved humic acids (HA) and their complexes with metal ions and organic pollutants is a crucial step in drinking water preparation due to significant undesirable effects of humic compounds on water quality. Constant demand for cheap, effective and environmentally friendly flocculants brings about the interest to natural cationic polymers which can be used to neutralize negative charge of humic colloids through polyelectrolyte complexes (PEC) formation. In this work, the interaction of HA with two types of soluble chitosan salts (hydrochloride and glutamate) at different pH and polymer ratios was studied with a focus on electrical charge of PEC formed and effectiveness of color removal in the flocculation process. For both chitosan forms flocculation window was found at pH close to the PEC isoelectric point (pI) in a wide concentration range; however, lower flocculant dose was required when chitosan glutamate was used.     

N-methyl-p-aminophenol (metol) ozonation in aqueous solution: kinetics, mechanism and toxicological characterization of ozonized samples

The ozonation of metol, one of the main constituents of photographic developers, has been studied in aqueous solution in the pH range 2.0–7.0. Main reaction mechanisms have been assessed on the basis of observed reaction intermediates and products at varying pH of the solution. The effect of manganese addition—Mn^II ions or solid MnO₂—to the reacting system has also been evaluated.

The capability of the ozonation treatment to reduce the toxicity of metol-containing aqueous solutions, with respect to selected organisms, such as algae, has also been studied according to reported standard procedures. The results of toxicological assessments show that high levels of detoxification are achieved after 20 min of ozonation treatment and that longer treatments cause an increase in the toxicity of the solution due to the formation of secondary reaction products. The adoption of proper chemical and fluid dynamic submodels enabled the estimation of the reaction kinetics of ozone that attack to the substrate.     

Relevance of side reactions in anaerobic reductive dechlorination microcosms amended with different electron donors

In this study we examined the relative importance of side reactions, i.e. the formation of volatile fatty acids (VFA), and the reduction of alternative electron acceptors (nitrate, sulfate, Fe(III)), in enhanced dechlorination microcosms, amended with different electron donors, namely lactate, butyrate, and H(2)+acetate mixture. Dechlorination reactions proceeded at low rates and consequently, nearly all of the reducing equivalents (over 99%) available from electron donor consumption were channeled to (side) reactions other than dechlorination. The relevance of these side reactions was more evident with lactate which was consumed at higher rate than other electron donors. Correspondingly, high levels of VFA and soluble Fe(II) accumulated in the supernatant of lactate-amended microcosms. Ecotoxicity experiments (Lepidium sativum germination tests) also indicated that the supernatant was much more toxic/inhibitory than that of other microcosms. Among the electron donors tested, the H(2)+acetate mixture, yielded the most promising results in terms of extent of dechlorination, negligible accumulation of by-products, and residual groundwater toxicity. Fluorescent In situ Hybridization analysis (FISH) confirmed that H(2)+acetate-amended microcosms were dominated by Dehalococcoides spp., while a higher biodiversity was observed in the cultures fed with lactate or butyrate. Overall, the average amount of donor that was required for the removal of 1micromol of chloride from the contaminant differed greatly among the donors, namely 2.13meq/micromolCl(-) for lactate, 1.01meq/micromolCl(-) for butyrate, and 0.39meq/micromolCl(-) for H(2)+acetate mixture. Interestingly, dechlorinating activity was observed under sulfate-reducing conditions; this suggests that it may not be necessary to deplete the sulfate from the groundwater, for instance by supplying an excess electron donor, in order to achieve substantial dechlorination. Finally, in this study we found that the pathway of anaerobic lactate degradation shifted from the production of acetate and H(2) during active sulfate reduction to acetate and propionate upon sulfate depletion. Energetic considerations that support this finding were presented.     

Maximizing the hydrogen yield in the catalyzed hydrolysis of pure borohydride powders

Around 10 wt% H₂ can be stored in a NaBH₄ based system at ambient temperature and atmospheric pressure. The hydrogen is released when water is added to an excess of NaBH₄(s)/cobalt (s)/NaOH(s) powder mixture. The heat evolved during the reaction increases the temperature from 25 up to 140 °C as monitored by an IR camera. This permits the formation of NaBO₂·H₂O with x ≈ 1/2, thermodynamically stable above 105 °C, rather than NaBO₂·4H₂O typically formed in excess water at room temperature. The presence of NaOH plays a crucial role in accelerating the reaction and increasing the temperature.     

Arsenic speciation and mobilization in CCA-contaminated soils: influence of organic matter content

A laboratory incubation experiment was conducted to investigate the influence of organic matter content on arsenic speciation and mobilization in chromated copper arsenate (CCA)-contaminated soils. The study was performed with four synthetic CCA-contaminated soils, with a range of organic matter content (mixture of peat moss and poultry manure) varying between 0.5% and 15% (w/w), under unsaturated and aerobic conditions for 40 days. Changes in water-soluble arsenic speciation (As(V), As(III), MMAA, DMAA) were monitored over time in soil extracts by HPLC-ICP-MS and in the soil solid phase (As(III), As(V)) by a solvent extraction method. Irrespective of organic matter content, As(V) was the predominant soil bound and aqueous phase arsenic species. However, over 40 days, a high soil organic matter content (7.5% and 15%) was able to entail formation of soil bound As(III). Moreover, total water-soluble arsenic was positively correlated with dissolved organic carbon (r(2)=0.88). However, the organic matter content did not influence arsenic speciation in the soluble fraction; neither As(V) reduction nor arsenic biomethylation occurred within 40 days. An increase in dissolved organic carbon content promoted both As(V) and As(III) solubilization in soils. Also, over time, organic matter contents of 7.5% and 15% entailed the persistence of soluble As(V), likely due to the high content of dissolved organic compounds which prevented its sorption onto soil. Based on this data, the environmental risk of aerobic CCA-contaminated soils rich in organic matter may be due to an enhanced availability of soluble As(V) over time, rather than to the formation of the more toxic and more mobile As(III).