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

Estudio comparativo de las epidermis foliares de las licopodiaceas ibericas I. Estomas

Se realiza un estudio comparativo de los estomas, tanto de los esporofilos como de los trofofilos, de Huperzia selago (L.) Bernh ex Schrank & Mart., Lycopodium annotinum L.,Lycopodium clavatum L., Diphasiastrum alpinum (L.) Holub y Lycopodiella inundata (L.) Holub aportando datos sobre la localización de los estomas en la lámina foliar, su distribución y número.A comparative study of stomates was made, both in sporophylles and trophophylles of Huperzia selago (L.) Bernh ex Schrank & Mart.,Lycopodium annotinum L. ,Lycopodium clavatum L.,Diphasiastrum alpinum (L.) Holub and Lycopodiella inundata (L.) Holub, giving new data about the localization of stomates on the foliar lamina, their distribution and number

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

Multiferroic behavior in the new double-perovskite Lu2_2MnCoO6_6

We present a new member of the multiferroic oxides, Lu$_2$MnCoO$_6$, which we have investigated using X-ray diffraction, neutron diffraction, specific heat, magnetization, electric polarization, and dielectric constant measurements. This material possesses an electric polarization strongly coupled to a net magnetization below 35 K, despite the antiferromagnetic ordering of the $S = 3/2$ Mn$^{4+}$ and Co$^{2+}$ spins in an $\uparrow \uparrow \downarrow \downarrow$ configuration along the c-direction. We discuss the magnetic order in terms of a condensation of domain boundaries between $\uparrow \uparrow$ and $\downarrow \downarrow$ ferromagnetic domains, with each domain boundary producing a net electric polarization due to spatial inversion symmetry breaking. In an applied magnetic field the domain boundaries slide, controlling the size of the net magnetization, electric polarization, and magnetoelectric coupling

Resonance phenomena of a solitonlike extended object in a bistable potential

We investigate the dynamics of a soliton that behaves as an extended particle. The soliton motion in an effective bistable potential can be chaotic in a similar way as the Duffing oscillator. We generalize the concept of geometrical resonance to spatiotemporal systems and apply it to design a nonfeedback mechanism of chaos control using localized perturbations.We show the existence of solitonic stochastic resonance.Comment: 3 postscript figure

Comportamento da renda e da mão-de-obra nas comunidades remanescentes dos quilombos de Oriximiná.

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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

Intensification of heterogeneous photocatalysis by applying a kenics® static mixer as catalyst support

Despite scientific community’s efforts, overcoming mass and photon transfer limitations remain a main challenge for heterogeneous photocatalysis with immobilized catalysts. Here, a Kenics® static mixer was used for the first time as catalyst support for heterogeneous photocatalysis in tubular reactors. This permitted not only to take advantage of the enhanced mass transfer supplied by the intense mixing, but also to provide a total illumination of the photocatalyst surface area with front-irradiation mechanism by using sunlight combined with compound parabolic collectors. Stainless steel Kenics® static mixers were coated with TiO2 or Fe2O3 photocatalyst and applied for oxytetracycline (OTC) degradation in aqueous solutions. The photocatalytic efficiency was evaluated as a function of different parameters: (i) catalyst deposition technique (dip coating or spray coating), (ii) photocatalyst film thickness, (iii) oxidant (H2O2) concentration, and (iv) number of static mixing elements.info:eu-repo/semantics/publishedVersio

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)