Ward Identities and chiral anomalies for coupled fermionic chains

Coupled fermionic chains are usually described by an effective model written in terms of bonding and anti-bonding spinless fields with linear dispersion in the vicinities of the respective Fermi points. We derive for the first time exact Ward Identities (WI) for this model, proving the existence of chiral anomalies which verify the Adler-Bardeen non-renormalization property. Such WI are expected to play a crucial role in the understanding of the thermodynamic properties of the system. Our results are non-perturbative and are obtained analyzing Grassmann functional integrals by means of Constructive Quantum Field Theory methods.Comment: TeX file, 26 pages, 7 figures. Published version, new section added to answer referee remarks and derive the Ward Identites, no modifications in the main resul

Light controlled magnetoresistance and magnetic field controlled photoresistance in CoFe film deposited on BiFeO3

We present a magnetoresistive-photoresistive device based on the interaction of a piezomagnetic CoFe thin film with a photostrictive BiFeO3 substrate that undergoes light-induced strain. The magnitude of the resistance and magnetoresistance in the CoFe film can be controlled by the wavelength of the incident light on the BiFeO3. Moreover, a light-induced decrease in anisotropic magnetoresistance is detected due to an additional magnetoelastic contribution to magnetic anisotropy of the CoFe film. This effect may find applications in photo-sensing systems, wavelength detectors and can possibly open a research development in light-controlled magnetic switching properties for next generation magnetoresistive memory devices.Comment: 5 pages, 4 figures, journal pape

Design of experiments to assess pre-treatment and co-digestion strategies that optimize biogas production from macroalgae Gracilaria vermiculophylla

A design of experiments was applied to evaluate different strategies to enhance the methane yield of macroalgae Gracilaria vermiculophylla. Biochemical Methane Potential (BMP) of G. vermiculophylla after physical pre-treatment (washing and maceration) reached 481 ± 9 L CH4 kg−1 VS, corresponding to a methane yield of 79 ± 2%. No significant effects were achieved in the BMP after thermochemical pre-treatment, although the seaweeds solubilisation increased up to 44%. Co-digestion with glycerol or sewage sludge has proved to be effective for increasing the methane production. Addition of 2% glycerol (w:w) increased the BMP by 18%, achieving almost complete methanation of the substrate (96 ± 3%). Co-digestion of seaweed and secondary sludge (15:85%, TS/TS) increased the BMP by 25% (605 ± 4 L CH4 kg−1 VS) compared to the seaweed individual digestion.The authors acknowledge the financial support of the Portuguese Science Foundation (FCT) and European Social Fund (ESF, POPH-QREN) through the grant given to Jose Carlos Costa (SFRH/BDP/48962/2008), and through the projects: FCOMP-01-0124-FEDER-027914 (PTDC/AAG-TEC/3048/2012), financed by FEDER through COMPETE - Programa Operacional Factores de Competitividade; and FCT Strategic Project PEst- OE/EQB/LA0023/2013, the FCT Project RECI/BBB-EBI/0179/2012 and the Project "BioEnv Biotechnology and Bioengineering for a sustainable world'', REF. NORTE-07-0124-FEDER-000048, co-funded by the Programa Operacional Regional do Norte (ON. 2 - O Novo Norte), QREN, FEDER. We would like to thank Dr. Rui Pereira (Algaplus), for providing the seaweed samples

Optimization of biogas production from Sargassum sp. using a design of experiments to assess the co-digestion with glycerol and waste frying oil

A Design of Experiments was adopted to assess the optimal conditions for methane production from the macroalgae Sargassum sp. co-digested with glycerol (Gly) and waste frying oil (WFO). Three variables were tested:% total solids of algae (%TSSargassumsp.), co-substrate concentration (gGly/WFO L-1); and, co-substrate type (Gly or WFO). The Biochemical Methane Potential (BMP) of Sargassum sp. was 181±1 L CH4 kg-1 COD. The co-digestion with Gly and WFO increased the BMP by 56% and 46%, respectively. The methane production rate (k), showed similar behaviour as the BMP, increasing 38% and 19% with Gly and WFO, respectively. The higher BMP (283±18 L CH4 kg-1 COD) and k (65.9±2.1 L CH4 kg-1 COD d-1) was obtained in the assay with 0.5% TS and 3.0 gGly L-1. Co-digestion with glycerol or WFO is a promising process to enhance the BMP from the macroalgae Sargassum sp.The authors acknowledge the financial support of the Portuguese Science Foundation (FCT) and European Social Fund (ESF, POPH-QREN) through the grant given to JoseCarlos Costa (SFRH/BDP/48962/2008), and through the project FCOMP-01-0124FEDER-027914 (PTDC/AAG-TEC/3048/2012), financed by FEDER through COMPETE -Programa Operacional Factores de Competitividade; and FCT Strategic Project PEst-OE/EQB/LA0023/2013, the FCT Project RECI/BBB-EBI/0179/2012 and the Project "BioEnv - Biotechnology and Bioengineering for a sustainable world'', REF. NORTE-07-0124-FEDER-000048, co-funded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER

Response surface design to study the influence of inoculum, particle size and inoculum to substrate ratio on the methane production from Ulex sp.

Ulex europaeus is one of the world worst invaders vegetal species and its suitability for biogas production is significant. The effect of three factors affecting the Biochemical Methane Potential (BMP, expressed as volume of CH4 per mass of volatile solids of waste) and the biodegradability rate (k, expressed in volume of CH4 per mass of VS and time) of U. europaeus was assessed by a Central Composite Face Centred Design. The BMP varied from 153 L kg1 to 308 L kg1. Inoculum to substrate ratio (ISR) and the type of inoculum had high influence on the final results. k varied from 14 L kg1 d1 to 49 L kg1 d1. The conditions that simultaneously maximized the BMP and k were an inoculum consisting in 55% (v) of granular sludge and 45 % (v) of suspended sludge from a sludge digester, an ISR of 4 g g1, and a particle size of 1.9 mm. Considering the average biomass production in shrub land areas, the potential energy production from U. europaeus is estimated in (36.9 ± 19.3) GJ ha1 yr1. For example, in Europe, a maximum energy supply of 7 EJ yr1 could be achieved from potentially harvestable shrub land areas.The authors acknowledge the financial support of the Portuguese Science Foundation (FCT) and European Social Fund (ESF, POPH-QREN) through the grant given to José Carlos Costa (SFRH/BDP/48962/2008), and through the project FCOMP-01-0124-FEDER-027914 (PTDC/AAG-TEC/3048/2012), financed by FEDER through COMPETE e Programa Operacional Factores de Competitividade; and FCT Strategic Project PEst-OE/EQB/LA0023/2013, the FCT Project RECI/BBB-EBI/0179/2012 and the Project “BioEnv e Biotechnology and Bioengineering for a sustainable world”, REF. NORTE-07-0124-FEDER-000048, co-funded by the Programa Operacional Regional do Norte (ON.2 e O Novo Norte), QREN, FEDER

Evaluation of different strategies to maximize biogas production from algae

Seaweeds (macroalgae) are a promising substrate for biogas production due to the high percentage of carbohydrates and high growth rate. Therefore, the biogas produced from the anaerobic digestion of seaweeds is a sustainable and renewable alternative source of bioenergy. Seaweeds are available in coastal areas and may also be produced in aquacultures. This work presents results of the biochemical methane potential (BMP) of the wild seaweed, Gracilaria vermiculophylla, as well as the effect of physical and thermochemical pre-treatments on their biodegradability. The codigestion with glycerol and sewage sludge was also studied. The BMP of G. vermiculophylla after a physical pre-treatment (washing and maceration) reached 481±9 L CH4 kg-1 VS, corresponding to a methane yield of 79±2%. Regarding the thermochemical pre-treatments, it was found that the increase of temperature (from 20 to 90ºC), NaOH concentration (from 0.1 to 0.5 g NaOH per g TS) and pressure (from 1 to 6 bar) caused an increase in the seaweeds solubilisation up to 44%. However, the subsequent methane production was not increased as expected, although a faster methane production rate was observed. The co-digestion of G. vermiculophylla with glycerol or sewage sludge has proved to be quite effective for increasing the methane production. Addition of 2% glycerol (w:w) increased the methane production by 18% (599±16 L CH4 kg-1 VS) and methane yield by 22%, achieving almost complete substrate methanation. Moreover, the codigestion of seaweed and secondary sludge (15:85%, TS/TS) caused an increase of 25% in the BMP (605 ± 4 L CH4 kg-1 VS), relatively to the individual digestion of algae. The addition of glycerol in this assay did not cause significant improvements