Noise and Periodic Modulations in Neural Excitable Media

We have analyzed the interplay between noise and periodic modulations in a mean field model of a neural excitable medium. To this purpose, we have considered two types of modulations; namely, variations of the resistance and oscillations of the threshold. In both cases, stochastic resonance is present, irrespective of if the system is monostable or bistable.Comment: 13 pages, RevTex, 5 PostScript figure

Zinc(II) coordination polymers with pseudopeptidic ligands

Two new phenyl-bridged pseudopeptidic ligands have been prepared and structurally characterised. The nature of the ligands’ substituents play an important role in the nature of the solid state structure yielding either hydrogen bonded linked sheets of molecules or infinite hydrogen bonded networks. Both these ligands were reacted with a range of zinc(II) salts with the aim of synthesising coordination polymers and networks and exploring the role that anions could play in determining the final structure. The crystal structures of four of these systems (with ZnSO4 and ZnBr2) were determined; in one case, a 3D coordination network was obtained where zinc–ligand coordination bonds generated the 3D arrangements. Three other 3D networks were obtained by anion-mediated hydrogen bonding of coordination 1D chains or 2D sheets. These four very different structures highlight the important role played by the ligands’ substituents and the counteranions present in the system

Treatment of wastewater containing mineral oil by sorption onto granulated cork

The aim of this work is the development of a new method to remove oils from wastewaters, namely hydrocarbons. These contaminants, when present in high concentrations, are efficiently removed by physical and chemical processes, such as gravity separators, flocculation and flotation processes; however for low concentrations, these methods are not applicable [1]. Moreover, advanced separation processes such as membrane separation [2] and activated carbon adsorption [3] are expensive options for the treatment of oil-containing wastewaters. This new technique is based on oil and hydrocarbons’ sorption on cork granules.This work is supported by project HIDROCORK "Utilization of Cork Wastes and By-Products for Elimination of Oils and Fats from Waters", financed by QREN (National Strategic Reference Framework). This work is also partially supported by project PEst-C/EQBILA0020/2011, financed by FEDER through COMPETE_ Programa Operacional Factores de Competitividade and by FCT -Fundação para a Ciência e a Tecnologia

Studies on sorption and regeneration of granulated cork for oil and grease removal

The aim of this work is to develop a method to recover sorbed oil and grease from granulated cork, in order to promote biomass regeneration. Experimental procedure involved biomass saturation with oil, followed by chemical regeneration. Oil removal by elution was tested using HNO3 and NaOH solutions, cationic and anionic surfactants and organic solvents, namely carbon tetrachloride and n-hexane. Chemical desorption efficiency using organic solvents achieved values of 90 ± 6 % and 72 ± 6 % for CCl4 and n-hexane, respectively. Although the use of organic solvents proved to be an efficient process, it involves high costs and a negative environmental impact. Physical regeneration could be an alternative to the use of solvents for oil removal from granulated cork.This work is supported by project HIDROCORK “Utilization of Cork Wastes and By-Products for Elimination of Oils and Fats from Waters”, financed by QREN (National Strategic Reference Framework). This work is also partially supported by project PEst-C/EQB/LA0020/2011, financed by FEDER through COMPETE - Programa Operacional Factores de Competitividade and by FCT - Fundação para a Ciência e a Tecnologia. A. Pintor also acknowledges her PhD fellowship by FCT (SFRH / BD / 70142 / 2010)

Valorisation of cork by-products for the treatment of vegetal and animal oil containing wastewaters

In this study, cork granules, which are by-products of the cork processing industry, were used as biosorbents for the removal of vegetable and animal oils from water. Simple oil-in-water emulsions were created by ultrasonic emulsification and batch adsorption tests were performed by contacting cork with these emulsions for a defined period of time. A mass transfer model was able to predict adequately the kinetic data, using a Linear Driving Force approximation for intraparticle diffusion and equilibrium described by the Langmuir-Freundlich equation. Maximum sorption capacities for vegetable and animal oil, as calculated by the Langmuir-Freundlich model, were 5 ± 4 and 2.3 ± 0.9 g g-1, respectively. Therefore, expanded cork granules proved to be an efficient, low-cost sorbent for both vegetable and animal oilsThis work is supported by project HIDROCORK “Utilization of Cork Wastes and By-Products for Elimination of Oils and Fats from Waters”, supported by QREN (National Strategic Reference Framework). This work is also partially supported by project PEst-C/EQB/LA0020/2011, financed by FEDER through COMPETE -Programa Operacional Factores de Competitividade and by FCT -Fundação para a Ciência e a Tecnologia

Turning Carbon Dioxide and Ethane into Ethanol by Solar-Driven Heterogeneous Photocatalysis over RuO2- and NiO-co-Doped SrTiO3

[EN] The current work focused on the sunlight-driven thermo-photocatalytic reduction of carbon dioxide (CO2), the primary greenhouse gas, by ethane (C2H6), the second most abundant element in shale gas, aiming at the generation of ethanol (EtOH), a renewable fuel. To promote this process, a hybrid catalyst was prepared and properly characterized, comprising of strontium titanate (SrTiO3) co-doped with ruthenium oxide (RuO2) and nickel oxide (NiO). The photocatalytic activity towards EtOH production was assessed in batch-mode and at gas-phase, under the influence of different conditions: (i) dopant loading; (ii) temperature; (iii) optical radiation wavelength; (vi) consecutive uses; and (v) electron scavenger addition. From the results here obtained, it was found that: (i) the functionalization of the SrTiO3 with RuO2 and NiO allows the visible light harvest and narrows the band gap energy (ca. 14-20%); (ii) the selectivity towards EtOH depends on the presence of Ni and irradiation; (iii) the catalyst photoresponse is mainly due to the visible photons; (iv) the photocatalyst loses > 50% efficiency right after the 2nd use; (v) the reaction mechanism is based on the photogenerated electron-hole pair charge separation; and (vi) a maximum yield of 64 mu mol EtOH g(cat)(-1) was obtained after 45-min (85 mu mol EtOH g(cat)(-1) h(-1)) of simulated solar irradiation (1000 W m(-2)) at 200 degrees C, using 0.4 g L-1 of SrTiO3:RuO2:NiO (0.8 wt.% Ru) with [CO2]:[C2H6] and [Ru]:[Ni] molar ratios of 1:3 and 1:1, respectively. Notwithstanding, despite its exploratory nature, this study offers an alternative route to solar fuels' synthesis from the underutilized C2H6 and CO2.This work was financially supported by the Base Funding-UIDB/50020/2020 of the Associate Laboratory LSRE-LCM-funded by national funds through FCT/MCTES (PIDDAC). Larissa O. Paulista also wants to acknowledge for her doctoral fellowship (reference SFRH/BD/137639/2018), supported by FCT. Tania F. C. V. Silva and Vitor J. P. Vilar acknowledge the FCT Individual Call to Scientific Employment Stimulus 2017 (CEECIND/01386/2017 and CEECIND/01317/2017, respectively). Josep Albero and Hermenegildo Garcia are also grateful to the Spanish Ministry of Science and Innovation (RTI2018-098237-CO2-R1 and Severo Ochoa), Generalitat Valencia (Prometeo 2017/083) and European Union's Horizon 2020 research and innovation programme under grant agreement No 862453, project FlowPhotochem, by financial contribution.Paulista, LO.; Albero-Sancho, J.; Martins, RJE.; Boaventura, RAR.; Vilar, VJP.; Silva, TFCV.; García Gómez, H. (2021). Turning Carbon Dioxide and Ethane into Ethanol by Solar-Driven Heterogeneous Photocatalysis over RuO2- and NiO-co-Doped SrTiO3. Catalysts. 11(4):1-18. https://doi.org/10.3390/catal1104046111811

A New Approach to Non-Commutative U(N) Gauge Fields

Based on the recently introduced model of arXiv:0912.2634 for non-commutative U(1) gauge fields, a generalized version of that action for U(N) gauge fields is put forward. In this approach to non-commutative gauge field theories, UV/IR mixing effects are circumvented by introducing additional 'soft breaking' terms in the action which implement an IR damping mechanism. The techniques used are similar to those of the well-known Gribov-Zwanziger approach to QCD.Comment: 11 pages; v2 minor correction

Perturbing Topological Field Theories

The abelian Chern-Simons theory is perturbed by introducing local gauge-invariant interaction terms depending on the curvature. The computation of the correlation function of two Wilson lines for two smooth closed nonintersecting curves is reported up to four loops and is shown to be unaffected by radiative corrections. This result ensures the stability of the linking number of the two curves with respect to the local perturbations which may be added to the Chern-Simons action.Comment: 13 pages, 5 figures, corrected some typo

The Nondeterministic Waiting Time Algorithm: A Review

We present briefly the Nondeterministic Waiting Time algorithm. Our technique for the simulation of biochemical reaction networks has the ability to mimic the Gillespie Algorithm for some networks and solutions to ordinary differential equations for other networks, depending on the rules of the system, the kinetic rates and numbers of molecules. We provide a full description of the algorithm as well as specifics on its implementation. Some results for two well-known models are reported. We have used the algorithm to explore Fas-mediated apoptosis models in cancerous and HIV-1 infected T cells

An Algebraic Criterion for the Ultraviolet Finiteness of Quantum Field Theories

An algebraic criterion for the vanishing of the beta function for renormalizable quantum field theories is presented. Use is made of the descent equations following from the Wess-Zumino consistency condition. In some cases, these equations relate the fully quantized action to a local gauge invariant polynomial. The vanishing of the anomalous dimension of this polynomial enables us to establish a nonrenormalization theorem for the beta function $\beta_g$, stating that if the one-loop order contribution vanishes, then $\beta_g$ will vanish to all orders of perturbation theory. As a by-product, the special case in which $\beta_g$ is only of one-loop order, without further corrections, is also covered. The examples of the N=2,4 supersymmetric Yang-Mills theories are worked out in detail.Comment: 1+32 pages, LaTeX2e, typos correcte