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- Electrons or protons: what is the cause of forest fires in western europe on june 18, 2017?Publication . Radovanovic, Milan; Gomes, João; Yamashkin, Anatoly A.; Milenkovic, Milan; Stevančević, MilanForest fires in Portugal (June 17–24, 2017) destroyed 64 lives and caused considerable material damage. The coronal hole CH807 and the energy region S5710 were in the geoeffective position on the Sun immediately before the outbreak of fires. In the period that preceded it, as well as at the time of the fires, increased values of the solar wind (SW) parameters (temperature, speed and density of particles) were recorded. In addition, a geomagnetic disorder was recorded. The shape and size of the burning areas, as well as the low air pressure over Portugal indicate the possibility of the effect of positively charged particles that came from the area south, i.e. southwest of Portugal. Nevertheless, it is a specific case that would have to be investigated in more detail.
- Preliminary study on the use of biodiesel obtained from waste vegetable oils for blending with hydrotreated kerosene fossil fuel using Calcium Oxide (CaO) from natural waste materials as heterogeneous catalystPublication . Ozkan, Sila; Puna, Jaime; Gomes, João; Cabrita, T.; Palmeira, José; Santos, Maria TeresaIn this experimental work, calcium from natural seafood wastes was used as a heterogeneous catalyst separately or in a blend of "shell mix" for producing biodiesel. Several chemical reaction runs were conducted at varied reaction times ranging from 30 min to 8 h, at 60 degrees C, with a mass content of 5% (W-cat./W-oil) and a methanol/oil molar ratio of 12. After the purification process, the biodiesel with fatty acid methyl ester (FAME) weight content measured was higher than 99%, which indicated that it was a pure biodiesel. This work also showed that the inorganic solid waste shell mixture used as the heterogeneous catalyst can be reused three times and the reused mixture still resulted in a FAME content higher than 99%. After 40 different transesterification reactions were performed using liquid (waste cooking oils) and solid (calcium seafood shells) wastes for producing biodiesel, under the specific conditions stated above, we found a successful, innovative, and promising way to produce biodiesel. In addition, blends prepared with jet fuel A1 and biodiesel were recorded with no invalid results after certain tests, at 25 degrees C. In this case, except for the 10% blend, the added biodiesel had no significant effect on the viscosity (fluidity) of the biojet fuel.
- Exposure to airborne ultrafine particles from cooking in Portuguese homesPublication . Bordalo, J. C.; Gomes, João; Albuquerque, PaulaCooking was found to be a main source of submicrometer and ultrafine aerosols from gas combustion in stoves. Therefore, this study consisted of the determination of the alveolar deposited surface área due to aerosols resulting from commom domestic cooking activities (boiling fish; vegetables, or pasta, and frying hamburgers and eggs). The concentration of ultrafine particles during the cooking events significantly increased from a baseline of 42.7 um2 / cm3 (increased to 72.9 um2 / cm3 due to gas burning) to a maximun of 890.3 um2 / cm3 measured during fish boiling in water, and a maximun of 4500 um2 / cm3 during meat frying. This clearly show that a domestic activity such as cooking can lead expures as hight as those of occupational exposure activities.
- Characterization of airborne particles generated from metal active gas welding processPublication . Guerreiro, C.; Gomes, João; Carvalho, P.; Santos, T. J. G.; Miranda, R. M.; Albuquerque, PaulaThis study is focused on the characterization of particles emitted in the metal active gas welding of carbon steel using mixture of Ar + CO2, and intends to analyze which are the main process parameters that influence the emission itself. It was found that the amount of emitted particles (measured by particle number and alveolar deposited surface area) are clearly dependent on the distance to the welding front and also on the main welding parameters, namely the current intensity and heat input in the welding process. The emission of airborne fine particles seems to increase with the current intensity as fume-formation rate does. When comparing the tested gas mixtures, higher emissions are observed for more oxidant mixtures, that is, mixtures with higher CO2 content, which result in higher arc stability. These mixtures originate higher concentrations of fine particles (as measured by number of particles by cm 3 of air) and higher values of alveolar deposited surface area of particles, thus resulting in a more severe worker's exposure.
- Biodiesel glycerin valorization into oxygenated fuel additivesPublication . Soares Dias, A. P.; Fonseca, Frederico G.; Catarino, Mónica; Gomes, Joãorequires costly purification before commercialization. Production of oxygenated fuel additives is a potential route for glycerin valorization. Glycerin acetylation was carried out over heterogeneous acid catalysts (15%, glycerol weight basis) using glacial acetic acid (molar ratio=9). The catalysts, containing different amounts of phosphate species (P/Si from 10 to 20 atomic ratio), were prepared by wet impregnation of commercial silica with aqueous solutions of diammonium phosphate and ortho-phosphoric acid. X-ray diffraction patterns of calcined solids presented amorphous patterns like raw silica. The prepared catalysts presented, at 120 degrees C, glycerol conversion higher than 89.5% after 1 h of reaction, been diacetin the major product, with triacetin selectivities lower than 26.1%. Diacetin selectivity was found to be almost invariant with catalyst acidity thus underlining the relevance of catalyst porosity due to the large acetins molecules sizes. The slow rate of triacetin diffusion in narrow pores of catalyst might be responsible for the relatively low yield obtained. Surface phosphate species showed a slow rate of leaching in the reaction medium showing high catalyst stability.
- Monitoring exposure to airborne ultrafine particles in Lisbon, PortugalPublication . Gomes, João; Bordado, João Carlos Moura; Albuquerque, Paula.The aim of this study is to contribute to the assessment of exposure levels of ultrafine particles (UFP) in the urban environment of Lisbon, Portugal, due to automobile traffic, by monitoring lung-deposited alveolar surface area (resulting from exposure to UFP) in a major avenue leading to the town centre during late Spring, as well as in indoor buildings facing it. This study revealed differentiated patterns for week days and weekends, consistent with PM2.5 and PM10 patterns currently monitored by air quality stations in Lisbon. The observed ultrafine particulate levels could be directly related with the fluxes of automobile traffic. During a typical week, UFP alveolar deposited surface area varied between 35.0 and 89.2 mu m(2)/cm(3), which is comparable with levels reported for other towns such in Germany and United States. The measured values allowed the determination of the number of UFP per cm(3), which are comparable to levels reported for Madrid and Brisbane. In what concerns outdoor/indoor levels, we observed higher levels (32-63%) outdoor, which is somewhat lower than levels observed in houses in Ontario.
- Evaluation of the amount of nanoparticles emitted in welding fume from stainless steel using different shielding gasesPublication . Pacheco, Rita; Gomes, João; Miranda, R.; Quintino, M. L.The primary objective of this study was to correlate the emission of macro and nanoparticles released during the process of metal inert gas/metal active gas (MIG/MAG) of stainless steel with different gas mixtures. Using different gas mixtures with different heat inputs, it was possible to determine fume formation rates and surface areas of nanoparticles with alveolar lung deposition capacity. It was found, how the various transfer modes and the type of gas protection, in particular, the percentage of active elements in the in the chemical composition of the gas, affect the amount of fumes generated and also the generation of nanoparticles with a high capacity of deposition. The spray transfer mode always shows higher values of nanoparticles surface area, unlike the fume formation rates. Among the tested mixtures 82%Ar+18%CO2 generates higher emissions of nanoparticles as well as fume formation rates.
- Assessment of airborne nanoparticles emissions in the ceramic industryPublication . Esteves, H.; Gomes, João; M. Miranda, R.; Albuquerque, P.The aim of this study was to evaluate the occupational exposure to nanoparticles during the tasks performed in various jobs in the production processes of the national ceramic industry, analyze the collected data and seek to understand the specific occupational exposure situation of the workers in this sector. The study was developed in three different national production plants of ceramic, one of sanitary production, another of refractory bricks and another of ornamental ware (red paste). It is concluded that the values of occupational exposure to nanoparticles are high in all cases and that the nanoparticles are of very small size, with a strong capacity for alveolar penetration and, consequently, with a strong possibility of passing into the bloodstream, accumulating in the body.
- Study on the use of MgAl hydrotalcites as solid heterogeneous catalysts for biodiesel productionPublication . Gomes, João; Puna, Jaime; Gonçalves, Lissa M.; Bordado, JoãoThis paper, reports experimental work on the use of new heterogeneous solid basic catalysts for biodiesel production: double oxides of Mg and Al, produced by calcination, at high temperature, of MgAl lamellar structures, the hydrotalcites (HT). The most suitable catalyst system studied are hydrotalcite Mg:Al 2:1 calcinated at 507 degrees C and 700 degrees C, leading to higher values of FAME also in the second reaction stage. One of the prepared catalysts resulted in 97.1% Fatty acids methyl esters (FAME) in the 1st reaction step, 92.2% FAME in the 2nd reaction step and 34% FAME in the 3rd reaction step. The biodiesel obtained in the transesterification reaction showed composition and quality parameters within the limits specified by the European Standard EN 14214. 2.5% wt catalyst/oil and a molar ratio methanol:oil of 9:1 or 12:1 at 60 -65 degrees C and 4 h of reaction time are the best operating conditions achieved in this study. This study showed the potential of Mg/Al hydrotalcites as heterogeneous catalysts for biodiesel production. (C) 2011 Elsevier Ltd. All rights reserved.
- Determination of airborne nanoparticles from welding operationsPublication . Gomes, João; Albuquerque, Paula; Miranda, Rosa Maria Mendes; Vieira, Maria Teresa FreireThe aim of this study is to assess the levels of airborne ultrafine particles emitted in welding processes (tungsten inert gas [TIG], metal active gas [MAG] of carbon steel, and friction stir welding [FSW] of aluminum) in terms of deposited area in pulmonary alveolar tract using a nanoparticle surface area monitor (NSAM) analyzer. The obtained results showed the dependence of process parameters on emitted ultrafine particles and demonstrated the presence of ultrafine particles compared to background levels. Data indicated that the process that resulted in the lowest levels of alveolar deposited surface area (ADSA) was FSW, followed by TIG and MAG. However, all tested processes resulted in significant concentrations of ultrafine particles being deposited in humans lungs of exposed workers.