Strong curvature singularities in quasispherical asymptotically de Sitter dust collapse

We study the occurrence, visibility, and curvature strength of singularities in dust-containing Szekeres spacetimes (which possess no Killing vectors) with a positive cosmological constant. We find that such singularities can be locally naked, Tipler strong, and develop from a non-zero-measure set of regular initial data. When examined along timelike geodesics, the singularity's curvature strength is found to be independent of the initial data.Comment: 16 pages, LaTeX, uses IOP package, 2 eps figures; accepted for publication in Class. Quantum Gra

Inoculum acclimation to oleate promotes the conversion of olive mill wastewater to methane

This work aims at selecting a suitable strategy to accelerate the start-up of the anaerobic treatment of olive mill wastewater (OMW) and to enhance the biogas production. Two anaerobic sludges were tested in toxicity and biodegradability batch experiments: biomass acclimated to oleate (BAO) and biomass non-acclimated (BNA). The results showed that the resistance to OMW toxicity was higher for the BAO than for the BNA. In the presence of OMW, the BNA was inhibited at all concentrations tested, whereas for the BAO no inhibition occurred at 5 and 10 g COD L−1. In fact, even at 25 g COD L−1 both substrates (acetate + OMW) were degraded. The biodegradation rate of OMW was higher in batch vials with the acclimated sludge. The results demonstrate that the use of an acclimated microbial consortium to LCFA compounds is a promising strategy to accelerate the start-up of the digestion process, and to improve the overall anaerobic treatment of a real oily wastewater such as OMW with simultaneous bioenergy production (biogas)

Marine Biodiversity and Ecosystem Health of Ilhas Selvagens, Portugal

In September 2015, National Geographic's Pristine Seas project, in conjunction with the Instituto Universitário-Portugal, The Waitt Institute, the University of Western Australia, and partners conducted a comprehensive assessment of the rarely surveyed Ilhas Selvagens to explore the marine environment, especially the poorly understood deep sea and open ocean areas, and quantify the biodiversity of the nearshore marine environment

Integrated system for macroalgae production and conversion into biogas

Recently research on energy from macroalgae is being reconsidered driven by the following factors: fuel price increase, CO2 mitigation policies and interest on renewable energy sources after the Kyoto protocol, and need for energy crops not competing with land for food production. However, the commercial expansion of this energy source is limited by its economic feasibility. In this presentation we analyse the development of integrated systems that promote synergies between macroalgae/biogas production and activities such as aquaculture and urban wastewater treatment. The recycling of nutrients and CO2 by macroalgae can be an opportunity to reduce the biomass-biogas production cost. Other advantage is the proximity between biomass production, conversion into energy and its consumption, thus avoiding energy losses and pollution in transportation. Experimental work is underway and includes batch tests to evaluate biodegradability of Ulva spp. and Gracilaria sp. and co-digestion of these macroalgae with sewage sludge from Beirolas wastewater treatment plant (WWTP). Furthermore, continuous co-digestion experiments are planned to be carried out in a 30 L experimental reactor to be placed in the same WWTP. The objectives are to reproduce sludge digestion in Beirolas WWTP and evaluate algae/sludge co-digestion performance. Preliminary results indicate methane yields in accordance with similar batch experiments, whereby our CH4 yields per volatile solids added range between 0.14-0.20 m3 CH4 kg-1 VSadded against 0.16-0.27 m3 CH4 kg-1 VSadded [1,2] depending on the algae species and pretreatment. Overall, Ulva sp. shows a better performance over Gracilaria sp. as also confirmed in other experiments [1]

Start-up and feeding strategy of an anaerobic sequencing batch reactor for olive mill wastewater treatment

Olive mill wastewater (OMW) is the effluent generated by olive oil industries, mainly produced in the Mediterranean areas. The production of olive oil generates huge amounts of wastewater. Anaerobic wastewater treatment processes appears as a promising technology for the treatment and energetic potential recovery of these high strength wastewaters since a renewable energy source (biogas) is generated. However, due to the high organic contents and presence of lipidic and phenolic compounds the treatment of OMW is sometimes toxic to the anaerobic microorganisms. Aiming at define the best strategy for the anaerobic sequencing batch reactor start-up, two reactors were operated with an hydraulic retention time of 10 days, fed with OMW at 5gCOD/L. In batch assays it was previously observed that when using an adapted microbial consortium to lipids, OMW was more efficiently converted to biogas and the overall methane production was higher. On the other hand an intermittent feeding start-up was proven to promote the degradation of long chain fatty acids to methane. Therefore, two reactors, R1 and R2 were inoculated with a biomass acclimated to oleate (BAO) and a biomass non-acclimated (BNA), respectively. The inoculum type effect on start-up efficiency and the benefits of an intermittent feeding were studied. In both reactors, the COD removal efficiency reached more than 80% after 50 days of operation. The reactor with BAO was more stable during the operation period than in the reactor with BNA. The inoculums effect was determinant in the initial phase of feeding, but, as expected, its effect was diluted after 30 days. The intermittent feeding was tested in R1. Promoting the degradation of the accumulated substrate was beneficial to increase the specific methanogenic activity of the sludge inside the reactor

Biomethanation potential of macroalgae Ulva spp. and Gracilaria spp. and in co-digestion with waste activated sludge

Biochemical methane potential of four species of Ulva and Gracilaria genus was assessed in batch assays at mesophilic temperature. The results indicate a higher specific methane production (per volatile solids) for one of the Ulva sp. compared with other macroalgae and for tests running with 2.5% of total solids (196 ± 9 L CH4 kg−1 VS). Considering that macroalgae can potentially be a post treatment of municipal wastewater for nutrients removal, co-digestion of macroalgae with waste activated sludge (WAS) was assessed. The co-digestion of macroalgae (15%) with WAS (85%) is feasible at a rate of methane production 26% higher than WAS alone without decreasing the overall biodegradability of the substrate (42–45% methane yield). The use of anoxic marine sediment as inoculum had no positive effect on the methane production in batch assays. The limiting step of the overall anaerobic digestion process was the hydrolysis.The authors acknowledge the financial support of the "Fundacao para a Ciencia e a Tecnologia" through the grant given to Jose Carlos Costa (SFRH/BDP/48962/2008) and Ana Nobre (SFRH/BPD/64582/2009)

Crystallographic and magnetic properties of UFe5.8Al6.2 single crystals

Single crystals of UFe5.8Al6.2 were characterised by X-ray and neutron diffraction, 57Fe Mössbauer spectroscopy and magnetisation. The structure refinement by X-ray and neutron diffraction shows a ThMn12-type structure, the Fe atoms fully occupying the 8f and partially occupying the 8j positions. Mössbauer spectra confirm these occupations and further indicate a magnetic ordering below 293 K. Magnetisation measurements show a ferromagnetic behaviour below 300 K, with a and b as easy directions and a spontaneous magnetisation of 10.4 [mu]B/f.u. at 5 K, due to the Fe occupation of 8j position. These single crystal results significantly differ from those previously obtained in UFe6Al6 polycrystalline samples obtained by melting and annealing.http://www.sciencedirect.com/science/article/B6TJJ-3V7WTYX-N/1/f7893080a7f27a628198f02aeb40fe2

Preparation of Poly(vinyl chloride) Latexes Using a Dual Surfactant System: The Effect in the Particle Size Distribution

The control of the average particle size and size distribution in the emulsion polymerization of vinyl chloride monomer is an important parameter to determine, not only the latex characteristics, but also the properties of the final dispersion powder in several industrial applications. It is possible to manipulate the particle size distribution (PSD) by applying a mixture of an anionic surfactant-fatty alcohol before the start of the free radical polymerization. Contrary to the procedures of the miniemulsion and the derivative diffusional swelling techniques, no kind of high shear is applied to the monomer and/or surfactant mixtures. In fact, the concentration and selection of the anionic surfactant, together with the fatty-alcohol, can play an interesting role on the final PSD of the polymer's particlesFCT; contract grant number SFRH/BDE/15534/200

Anaerobic digestion of OMW : intermittent feeding strategy and LCFA oxidation profile

ManuscriptAn intermittent feeding strategy was applied to the anaerobic treatment of raw olive mill wastewater (OMW). Two reactors were operated under influent concentrations of 5 to 50 g COD L-1. Two and one batch (feed-less) periods were applied to reactor R1 and R2, respectively, operating in continuous thenceforth. It was demonstrated that the intermittent feeding of OMW improved the mineralization of accumulated Long Chain Fatty Acids (LCFA) inside the reactor. Nevertheless, LCFA accumulated again when the organic loading rate was increased from 2 to 3 and 5 kg COD m-3 d-1. The profiles of LCFA, obtained with OMW digestion, were different from previous studies with synthetic effluents. At the beginning of reactors operation, oleate was the main LCFA compound (~50%) followed by palmitate. Afterwards, a shift in the LCFA pattern accumulation was noticed for both reactors. At periods with higher OMW concentrations (30-50 g COD L-1, 3-5 kg COD m-3 d-1) palmitate was the main LCFA accumulated with 69% at R1 and 54% at R2. For real oily wastewaters, a periodically batch period could be a practical solution to maintain low values of LCFA inside the reactor. The addition of a nitrogen source was essential to enhance the methane yield

Cytotoxicity profiling of deep eutectic solvents to human skin cells

The tailor-made character of deep eutectic solvents (DES) turns them very attractive to be used in several applications, including in health-related areas such as pharmaceutical, nutraceutical, and cosmetic industries. However, although DES has been touted as "green" solvents, several works proved that their potential toxicity should not be neglected. Using the premise of DES applicability in the cosmetic and pharmaceutical sectors, we chose two cell lines to work as a skin model (keratinocytes HaCaT and tumor melanocytes MNT-1), to assess DES cytotoxicity. The effect of three different hydrogen bond acceptors (HBA) ([Chol]Cl, [N1111]Cl and [N4444]Cl) and three different hydrogen bond donors (HBD) (hexanoic and butanoic acid, ethylene glycol, 1-propanol and urea) were evaluated through a common viability assay (MTT assay). Results were promising since [Chol]Cl and [N1111]Cl- based DES showed good biocompatibility for the tested cells. [N4444]Cl-based DES, however, showed cytotoxicity for both cell lines, with the HBA being the driver of the toxicity. Interestingly, some compounds increased cell viability in the HaCaT cell line, namely [Chol]Cl, ethylene glycol, hexanoic acid, urea, and all [Chol]Cl and [N1111]Cl-based DES and should be considered as targets for future studies. These results highlight their possible use in cosmetic or pharmaceutical formulations.publishe