Influence of NaCl,Na2SO4 and O2 on power generation from microbial fuel cells with non-catalyzed carbon electrodes and natural inocula

Microbial fuel cells (MFCs) are facing several technological challenges before they can be considered as reliable energy sources. Although several feasible inocula, materials and catalysts have been employed to produce energy, the design of a MFC should be done under realistic conditions: abundant and economic feedstock. In this study, two different MFC designs (parallel plate and tank reactors) are tested with non-catalyzed carbon electrodes and natural inocula. In both approaches cathodic oxygen reduction is performed on two different non-catalyzed carbon materials: carbon fabric and reticulate vitreous carbon. This study shows that power and current densities can be boosted by systematically decreasing the catholyte resistance (by additions of NaCl or Na₂SO₄) and dissolved oxygen concentration. In the parallel plate cell configuration, a mixed culture coming from sludge wastewater was used and power outputs up to 73 mW m^?2 (2867 mW m^?3) coupled to 187 mA m^?2 (anode surface area), were achieved. In the Sediment MFC cell configuration, lagoon sediment was used as both organic source of energy and natural supply of bacteria. Under this approach, the concentration of the organic matter is limited but it is demonstrated that bacteria can be adapted to degrade acetate. Power outputs up to 3.9 mW m^?2 normalized to the anodic electrode footprint area, coupled to 13 mA m^?2 were achieved.     

What goes up: Recent trends in Mexican residential energy use

Energy use in the Mexican residential sector is steadily increasing. Important factors contributing to the increase include changes in the types of housing built, heating, cooling, water-heating equipment and other appliances.     

Heat recovery system to power an onboard NH3-H2O absorption refrigeration plant in trawler chiller fishing vessels

This paper is concerned with the design, modelling and parametric analysis of a gas-to-thermal fluid heat recovery system from engine exhausts in a trawler chiller fishing vessel to power an NH₃-H₂O absorption refrigeration plant for onboard cooling production. Synthetic oil was used as heat transfer fluid and recirculated. The major components of the system are fluid-to-solution and gas-to-fluid heat exchangers. Both heat exchangers and the complete system have been modelled. Models are implemented in several computer programs. These models have been used to study the influence of geometric design parameters and thermal operating conditions on heat exchangers and system thermal performance. The analysis of the results allowed us to find the optimum thermal operating conditions that minimise total heat transfer area. Optimal design based on real data was performed and the operating function of exhaust gases by-pass control was obtained and is presented.     

An investigation of hydrogen storage in a magnesium-based alloy processed by equal-channel angular pressing

Equal-Channel Angular Pressing (ECAP) can be successfully used to process Mg and Mg-based hydrides to produce bulk samples with enhanced hydrogen sorption properties. The primary advantages associated with ECAP processing are the shorter processing time, lower cost and the production of safer and more air-resistant bulk material by comparison with powders produced by high-energy ball milling. ECAP can produce special features for hydrogen absorption such as preferential textures, an increased density of defects and submicrometer grain sizes. In this research, ECAP was used to process a commercial AZ31 extruded alloy in order to evaluate its use as a hydrogen storage material. The ECAP was conducted under conditions of temperature and number of passes in order to avoid grain growth. Additional experiments were conducted on commercial coarse-grained magnesium to evaluate the effect of sample thickness on the sorption properties. The ECAP sample was evaluated in two different orientations and it is shown that better hydrogen properties are related to a refined microstructure allied to the (0001) texture.     

R1234yf Flow Boiling Heat Transfer Inside a 2.4-mm Microfin Tube

ABSTRACT

This paper presents an experimental study on R1234yf flow boiling inside a mini microfin tube with an inner diameter at the fin tip of 2.4 mm. R1234yf is a new refrigerant with an extremely low global warming potential (GWP <1), proposed as a possible substitute for the common R134a, whose GWP is about 1300. The mass flux was varied between 375 and 940 kg m^?2 s^?1, heat flux from 10 to 50 kW m^?2, and vapor quality from 0.1 to 1. The saturation temperature at the inlet of the test section was kept constant and equal to 30°C. The wide range of operative test conditions permitted highlighting the effects of mass flux, heat flux, and vapor quality on the thermal and hydraulic behavior during the flow boiling mechanism inside such a mini microfin tube. The results show that at low heat flux the phase-change process is mainly controlled by two-phase forced convection, and at high heat flux by nucleate boiling. The two-phase frictional pressure drop increases with increasing both mass velocity and vapor quality. Dry-out was observed only at the highest heat flux, at vapor qualities of around 0.94–0.95.     

Transglutaminase treatment of brown rice flour: A chromatographic, electrophoretic and spectroscopic study of protein modifications

Recently, it was shown that transglutaminase (TGase) treatment of brown rice (BR) flour results in textural improvements of gluten-free bread. In this study, changes in the protein profiles of BR flour and protein fractions induced by TGase treatment were investigated to better understand the activity and specificity of the enzyme. Size-exclusion HPLC (SE-HPLC) profiles of flour extracts, under reducing conditions, revealed the presence of macromolecular protein complexes, as well as low molecular weight proteins. After TGase treatments (10 U/g of proteins) a general reduction in peak intensities indicated the polymerisation of BR proteins into larger, insoluble complexes. Microchip capillary electrophoresis and two-dimensional (2D) gel electrophoresis revealed that the α and β glutelin subunits were primary substrates for the polymerisation reaction, whereas albumins and globulins were only slightly affected. SE-HPLC of the protein fractions revealed glutelins’ polymerisation into high molecular weight structures after TGase treatment. Dynamic light scattering measurements showed that new supramolecular aggregates of glutelins co-existed with the macromolecular complexes already present in the untreated fraction. Front-face fluorescence approaches indicated that TGase treatment caused a decrease in protein surface hydrophobicity of BR flour, but not of the glutelin suspensions. It is concluded that the large protein complexes resulting from glutelin polymerisation and the stronger hydrophobic interactions among proteins result in the improved textural properties of TGase-treated BR bread.     

Electronic tongue: a versatile tool for mineral and fruit-flavored waters recognition

Natural mineral waters (still), effervescent natural mineral waters (sparkling) and aromatized waters with fruit-flavors (still or sparkling) are an emerging market. In this work, the capability of a potentiometric electronic tongue, comprised with lipid polymeric membranes, to quantitatively estimate routinely quality physicochemical parameters (pH and conductivity) as well as to qualitatively classify water samples according to the type of water was evaluated. The study showed that a linear discriminant model, based on 21 sensors selected by the simulated annealing algorithm, could correctly classify 100 % of the water samples (leave-one out cross-validation). This potential was further demonstrated by applying a repeated K-fold cross-validation (guaranteeing that at least 15 % of independent samples were only used for internal-validation) for which 96 % of correct classifications were attained. The satisfactory recognition performance of the E-tongue could be attributed to the pH, conductivity, sugars and organic acids contents of the studied waters, which turned out in significant differences of sweetness perception indexes and total acid flavor. Moreover, the E-tongue combined with multivariate linear regression models, based on sub-sets of sensors selected by the simulated annealing algorithm, could accurately estimate water’s pH (25 sensors: R ² equal to 0.99 and 0.97 for leave-one-out or repeated K-folds cross-validation) and conductivity (23 sensors: R ² equal to 0.997 and 0.99 for leave-one-out or repeated K-folds cross-validation). So, the overall satisfactory results achieved, allow envisaging a potential future application of electronic tongue devices for bottled water analysis and classification.     

Determination of phenolic compounds of ‘Sikitita’ olive leaves by HPLC-DAD-TOF-MS. Comparison with its parents ‘Arbequina’ and ‘Picual’ olive leaves

‘Sikitita’ is a new olive cultivar developed in Spain by crossing the cultivars ‘Picual’ and ‘Arbequina’. The phenolic fraction of olive leaves (Olea europaea L.), is purported to have good anti-oxidative properties which help to prevent several health problems. To our knowledge, no studies are available on the phenolic fraction of ‘Sikitita’ olive leaves or any other new cultivar developed from breeding. Thus, the identification and quantification of the phenolic fraction of ‘Sikitita’ olive leaves by HPLC-DAD-MS were studied and compared with those of its parent cultivars. The three cultivars were grown under the same agronomic and environmental conditions in the same orchard. The quantification was performed using HPLC-DAD, whereas qualitative data were acquired using HPLC-MS. It was thus possible to identify 30 different compounds, two of which have been tentatively characterized for the first time in olive leaves of Spanish cultivars. Significant differences between cultivars were observed for almost all the compounds. Results for ‘Sikitita’ olive leaves presented a higher degree of similarity with respect to ‘Picual’ than to ‘Arbequina’. Further work will monitor the time course of phenolic compounds over the growth period.     

Higher-order communications for concurrent programming

In Pettorossi and Skowron (1983) a recursive-equations language is introduced. Its operational semantics is specified by means of computing agents which communicate and exchange messages. Those communications are, so to speak, zero-order, in the sense that the exchanged messages are values of a data structure, possibly defined by the programmer.

In this paper we extend that approach and we consider also ‘higher-order’ communications by allowing the exchange of agents behaviours, i.e. sets of computations, among computing agents. This extension leads to a new programming methodology which makes use of proofs of computing agents behaviours and their related strategies.     

Carbon dioxide fixation by microalgae cultivated in open bioreactors

The biofixation of carbon dioxide (CO₂) by microalgae has been proven to be an efficient and economical method, mainly due to the photosynthetic ability of these microorganisms to use this gas as a source of nutrients for their development. The aim of this work was to study the growth of Spirulina LEB18 and Chlorella kessleri microalgae, exposed to controlled and non-controlled conditions, with the injection of different concentrations of CO₂. The cultures was carried out in 6 L open raceway ponds, under controlled conditions at 30 °C and 39 μE m^?2 s^?1 and under non-controlled conditions, protected by a tunnel of transparent film. The experiments were subjected to CO₂ injections at concentrations of 0.038, 6, 12 and 18% (v/v). The highest concentration of biomass (4.95 g L^?1) and maximum daily fixation (0.21 g g^?1 d^?1) were obtained for Spirulina LEB18 in culture that was prepared in non-controlled conditions with an injection of 6% (v/v) of CO₂. C. kessleri had maximum (p < 0.0008) specific growth rate (0.84 d^?1) when grown with 18% (v/v) of CO₂ in non-controlled conditions of cultivation.