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

Higher Derivative Quantum Gravity with Gauss-Bonnet Term

Higher derivative theory is one of the important models of quantum gravity, renormalizable and asymptotically free within the standard perturbative approach. We consider the $4-\epsilon$ renormalization group for this theory, an approach which proved fruitful in $2-\epsilon$ models. A consistent formulation in dimension $n=4-\epsilon$ requires taking quantum effects of the topological term into account, hence we perform calculation which is more general than the ones done before. In the special $n=4$ case we confirm a known result by Fradkin-Tseytlin and Avramidi-Barvinsky, while contributions from topological term do cancel. In the more general case of $4-\epsilon$ renormalization group equations there is an extensive ambiguity related to gauge-fixing dependence. As a result, physical interpretation of these equations is not universal unlike we treat $\epsilon$ as a small parameter. In the sector of essential couplings one can find a number of new fixed points, some of them have no analogs in the $n=4$ case.Comment: LaTeX file, 30 pages, 5 figures. Several misprints in the intermediate expressions correcte

Symmetry aspects of fermions coupled to torsion and electromagnetic fields

We study and explore the symmetry properties of fermions coupled to dynamical torsion and electromagnetic fields. The stability of the theory upon radiative corrections as well as the presence of anomalies are investigated.Comment: 9 pages, LaTe

Renormalization Ambiguities and Conformal Anomaly in Metric-Scalar Backgrounds

We analyze the problem of the existing ambiguities in the conformal anomaly in theories with external scalar field in curved backgrounds. In particular, we consider the anomaly of self-interacting massive scalar field theory and of Yukawa model in the massless conformal limit. In all cases the ambiguities are related to finite renormalizations of a local non-minimal terms in the effective action. We point out the generic nature of this phenomenon and provide a general method to identify the theories where such an ambiguity can arise.Comment: RevTeX, 10 pages, no figures. Small comment and two references added. Accepted for publication in Physical Review

Microbially charged redox flow battery: coupling a bioelectrochemical cell with a redox flow battery

ISMET 6 - General Meeting of the International Society for Microbial Electrochemistry and TechnologyRedox flow batteries (RFB) are electrochemical systems applied in the conversion and storage of chemical energy in electricity. Red ox chemical species (in soluble form) are the main responsible for the energy storage. Quinones are electroactive molecules applied in RFB because of their chemical and physical properties. The aim of this work is to develop an innovative technology to generate and storage the energy resultant from Bioelectrochemical system (BES). The strategy outlined was coupling a BES with a RFB that present potential to combine bioenergy production and storage in a microbially charged redox flow battery. Firstly, a BES system was studied with Geobacter su/furreducens as biocatalyst to convert a quinone (2,6-anthraquinone) in its respective reduced form, acetate being the carbon source used. The BES presented current intensities around 500 mA.m·2 and power densities around 2 wm· 2. The reduction was assessed visually by a typical colour change (from yellow to dark red) and by cyclic voltammetry. Simultaneously, as a control, the 2,6-anthraquinone was electrochemically reduced applying and controlling the cathode potential where the reduction was also observed by colour change and by cyclic voltammetry. In an RFB, the quinone bioreduced in tlie BES and electrochemically reduced in the electrochemical cell were studied using potassium hexacyanoferrate as the second redox chemical species for discharging/charging cycles in the RFB as the proof of concept of the microbially charged redox flow battery. The study was performed in a 25 cm2 single red ox flow cell (RF) with a constant current density of 0.2 mA.cm2 where coulombic efficiency, voltage efficiency and energy efficiency were observed for 10 cycles.info:eu-repo/semantics/publishedVersio

Coupling a bioelectrochemical cell with a redox flow battery for sustainable energy production and storage

Book of Abstracts of CEB Annual Meeting 2017[Excerpt] Bioelectrochemical systems (BES) are devices capable to convert chemical energy into electricity through the degradation of different organic compounds using electroactive bacteria as biocatalyst. The ability of microorganisms to form biofilms in electrode surfaces allows the transport of electrons, resultant from the oxidation of carbon sources, to an terminal electron acceptor [1]. Redox flow batteries (RFB) are electrochemical systems applied in the conversion and storage of chemical energy in electricity. Redox chemical species (in soluble form) are the main responsible for the energy storage [2]. Quinones are electroactive molecules applied in RFB because of their chemical and physical properties. The aim of this work is to develop an innovative technology to generate and storage the energy resultant from BES. The strategy outlined is coupling a BES with a RFB that present potential to combine bioenergy production and storage in a microbially charged redox flow battery. [...]info:eu-repo/semantics/publishedVersio

Hazard assessment of storm events for the battery, New York

The environmental and socio-economic importance of coastal areas is widely recognized, but at present these areas face severe weaknesses and high-risk situations. The increased demand and growing human occupation of coastal zones have greatly contributed to exacerbating such weaknesses. Today, throughout the world, in all countries with coastal regions, episodes of waves overtopping and coastal flooding are frequent. These episodes are usually responsible for property losses and often put human lives at risk. The floods are caused by coastal storms primarily due to the action of very strong winds. The propagation of these storms towards the coast induces high water levels. It is expected that climate change phenomena will contribute to the intensification of coastal storms. In this context, an estimation of coastal flooding hazards is of paramount importance for the planning and management of coastal zones. Consequently, carrying out a series of storm scenarios and analyzing their impacts through numerical modeling is of prime interest to coastal decision-makers. Firstly, throughout this work, historical storm tracks and intensities are characterized for the northeastern region of United States coast, in terms of probability of occurrence. Secondly, several storm events with high potential of occurrence are generated using a specific tool of DelftDashboard interface for Delft3D software. Hydrodynamic models are then used to generate ensemble simulations to assess storms' effects on coastal water levels. For the United States’ northeastern coast, a highly refined regional domain is considered surrounding the area of The Battery, New York, situated in New York Harbor. Based on statistical data of numerical modeling results, a review of the impact of coastal storms to different locations within the study area is performed

Modelling the Recoherence of Mesoscopic Superpositions in Dissipative Environments

A model is presented to describe the recently proposed experiment (J. Raimond, M. Brune and S. Haroche Phys. Rev. Lett {\bf 79}, 1964 (1997)) where a mesoscopic superposition of radiation states is prepared in a high-Q cavity which is coupled to a similar resonator. The dynamical coherence loss of such state in the absence of dissipation is reversible and can in principle be observed. We show how this picture is modified due to the presence of the environmental couplings. Analytical expressions for the experimental conditional probabilities and the linear entropy are given. We conclude that the phenomenon can still be observed provided the ratio between the damping constant and the inter-cavities coupling does not exceed about a few percent. This observation is favored for superpositions of states with large overlap.Comment: 13 pages, 6 figure