On the Consistency of a Fermion-Torsion Effective Theory

We discuss the possibility to construct an effective quantum field theory for an axial vector coupled to a Dirac spinor field. A massive axial vector describes antisymmetric torsion. The consistency conditions include unitarity and renormalizability in the low-energy region. The investigation of the Ward identities and the one- and two-loop divergences indicate serious problems arising in the theory. The final conclusion is that torsion may exist as a string excitation, but there are very severe restrictions for the existence of a propagating torsion field, subject to the quantization procedure, at low energies.Comment: LaTeX, 26 pages, 4 figure

Sustainability Assessment of indicators for integrated water resources management

The scientific community strongly recommends the adoption of indicators for the evaluation and monitoring of progress towards sustainable development. Furthermore, international organizations consider that indicators are powerful decision-making tools. Nevertheless, the quality and reliability of the indicators depends on the application of adequate and appropriate criteria to assess them. The general objective of this study was to evaluate how indicators related to water use and management perform against a set of sustainability criteria. Our research identified 170 indicators related to water use and management. These indicators were assessed by an international panel of experts that evaluated whether they fulfil the four sustainability criteria: social, economic, environmental, and institutional. We employed an evaluation matrix that classified all indicators according to the DPSIR (Driving Forces, Pressures, States, Impacts and Responses) framework. A pilot study served to test and approve the research methodology before carrying out the full implementation. The findings of the study show that 24 indicators comply with the majority of the sustainability criteria; 59 indicators are bi-dimensional (meaning that they comply with two sustainability criteria); 86 are one-dimensional indicators (fulfilling just one of the four sustainability criteria) and one indicator do not fulfil any of the sustainability criteria.Postprint (author's final draft

Trajectories in a space with a spherically symmetric dislocation

We consider a new type of defect in the scope of linear elasticity theory, using geometrical methods. This defect is produced by a spherically symmetric dislocation, or ball dislocation. We derive the induced metric as well as the affine connections and curvature tensors. Since the induced metric is discontinuous, one can expect ambiguity coming from these quantities, due to products between delta functions or its derivatives, plaguing a description of ball dislocations based on the Geometric Theory of Defects. However, exactly as in the previous case of cylindric defect, one can obtain some well-defined physical predictions of the induced geometry. In particular, we explore some properties of test particle trajectories around the defect and show that these trajectories are curved but can not be circular orbits.Comment: 11 pages, 3 figure

Network of recurrent events for the Olami-Feder-Christensen model

We numerically study the dynamics of a discrete spring-block model introduced by Olami, Feder and Christensen (OFC) to mimic earthquakes and investigate to which extent this simple model is able to reproduce the observed spatiotemporal clustering of seismicty. Following a recently proposed method to characterize such clustering by networks of recurrent events [Geophys. Res. Lett. {\bf 33}, L1304, 2006], we find that for synthetic catalogs generated by the OFC model these networks have many non-trivial statistical properties. This includes characteristic degree distributions -- very similar to what has been observed for real seismicity. There are, however, also significant differences between the OFC model and earthquake catalogs indicating that this simple model is insufficient to account for certain aspects of the spatiotemporal clustering of seismicity.Comment: 11 pages, 16 figure

Resources recovery in the dairy industry: bioelectricity production using a continuous microbial fuel cell

"Available online 19 April 2016"The increasing food demand and the exhaustion of non-renewable fuels provide new market opportunities in the agro-farming sector. Biological systems designed to add value to useless organic sub-products and to generate off-grid electricity may be one of the most interesting outcomes. Therefore, the capacity of some microorganisms to transfer electrons generated during organic carbon oxidation directly to an anode in a so-called microbial fuel cell (MFC) might be an asset in a sustainable management context. In this regard, the main goal of the present work was to evaluate the performance of a continuous MFC applied in a dairy industry. A maximum voltage of 576 mV was produced during continuous operation, corresponding to a power density of 92.2 mW·m-2 or 1.9 W·m-3. MFC was able to remove 1298±617 mg·L-1 of chemical oxygen demand (COD) at a hydraulic retention time of 8.4 h, and the maximum COD removal (63±5 %) was achieved after 20 days of continuous operation. In addition, the coulombic efficiency average was around 10.5±10% with a maximum of 24.2±1.5%. In average, the MFC was able to extract a specific energy of 8.95×102 kWh·kg-1 COD with a maximum output of 20.53×102 kWh·kg-1 COD. In conclusion, the MFC technology is a valuable option for simultaneous wastewater treatment and energy recovery and deserves to be tested and scaled-up in the dairy industry.Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, Project RECI/BBB-EBI/0179/ 2012 (FCOMP-01-0124-FEDER-027462)COMPETE 2020 (POCI- 01-0145-FEDER-006684)Program POPH/ESF - SFRH/BPD/80528/201

Assessment of electron transfer mechanisms during a long-term sediment microbial fuel cell operation

The decentralized production of bioelectricity as well as the bioremediation of contaminated sediments might be achieved by the incorporation of an anode into anaerobic sediments and a cathode suspended in the water column. In this context, a sediment microbial fuel cell microcosm was carried out using different configurations of electrodes and types of materials (carbon and stainless steel). The results showed a long-term continuous production of electricity (>300 days), with a maximum voltage of approximately 100 mV reached after ~30 days of operation. A twofold increase of voltage was noticed with a twofold increase of surface area (~30 mV to ~60 mV vs. 40 cm2 to 80 cm2), while a threefold increase was obtained after the substitution of a carbon anode by one of stainless steel (~20 mV to ~65 mV vs. 40 cm2 to 812 cm2). Cyclic voltammetry was used to evaluate sediment bacteria electroactivity and to determine the kinetic parameters of redox reactions. The voltammetric results showed that redox processes were limited by the diffusion step and corresponded to a quasi-reversible electron charge transfer. These results are encouraging and give important information for the further optimization of sediment microbial fuel cell performance towards the long-term operation of sediment microbial fuel cell devices.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 — Programa Operacional Regional doNorte. The authors also acknowledge the fellowship awarded to Gilberto Martins (SFRH/BPD/80528/2011) under the scope of the program POPH/ESF.info:eu-repo/semantics/publishedVersio