Dynamical mechanism of anticipating synchronization in excitable systems

We analyze the phenomenon of anticipating synchronization of two excitable systems with unidirectional delayed coupling which are subject to the same external forcing. We demonstrate for different paradigms of excitable system that, due to the coupling, the excitability threshold for the slave system is always lower than that for the master. As a consequence the two systems respond to a common external forcing with different response times. This allows to explain in a simple way the mechanism behind the phenomenon of anticipating synchronization.Comment: 4 pages including 7 figures. Submitted for publicatio

16α,17α-Ep­oxy-5α-hydr­oxy-6β-nitrooxy-20-oxopregnan-3β-yl acetate

The title steroid, C23H33NO8, is a pregnane derivative obtained regio-, stereo- and chemoselectively from the ring opening of the corresponding 5α,6α;16α,17α-diepoxide with bis­muth(III) nitrate. There are two symmetry-independent mol­ecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. All rings are trans-fused. The conformations of the six-membered rings are close to chair forms, while the five-membered ring adopts an envelope conformation. The mol­ecules are held together by an extensive O—H⋯O hydrogen-bonding network of chains runnning along the a axis

6β-Acetamido-5α-hydroxy­cholestan-3β-yl acetate

The title steroid, C31H53NO4, was prepared from the corresponding 5α,6α-epoxy­cholestane. The conformation of the six-membered rings is close to a chair form, while the five-membered ring adopts a twist conformation. The hydroxyl and acetamide groups are in axial positions. The nucleophilic species bound to the steroid nucleus at position 6 by the β-face, whereas the hydroxyl group at position 5 has α-orientation. All rings are trans-fused. The crystal packing shows that the mol­ecules related by twofold symmetry exist as O—H⋯O hydrogen-bonded dimers

3β-Acet­oxy-lup-20(29)-en-28-yl 1H-1,2,4-tri­azole-1-carboxyl­ate

The title triterpene, C35H53N3O4, is a C-28 carbamate derivative of 3β-acet­oxy­betulin prepared in a one-step reaction from the commercially available 1,1′-carbonyl-di(1,2,4-triazole) (CDT), crystallized from acetone/n-hexane. All rings are trans fused. The carbamate and acetate substituents are in axial and equatorial positions, respectively. A quantum chemical ab initio Roothaan Hartree–Fock calculation of the equilibrium geometry of the isolated mol­ecule gives values for bond lengths and valency angles in close agreement with experimental values. The calculation also reproduces the observed mol­ecular conformation, with puckering parameters that agree well with those determined from the crystallographic study

19β,28-Ep­oxy-18α-olean-3β-ol

The title triterpene, C30H50O2, is an 18α-oleanane derivative prepared by the Wagner–Meerwein rearrangement of betulin with Bi(OTf)3.xH2O (OTF is trifluoromethanesulfonate). There are two symmetry-independent mol­ecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. The conformation of the six-membered rings is close to a chair form, while the five-membered epoxide rings adopt envelope conformations. All rings are trans-fused. In the crystal, mol­ecules are held together by O—H⋯O hydrogen bonds. A quantum-mechanical ab initio Roothan Hartree–Fock calculation on the isolated mol­ecule gives values for bond lengths and valency angles close to the experimental values. The calculations also reproduce well the mol­ecular conformation with calculated puckering parameters that match well the observed values

Use of nanofiltration membrane technology for ceramic industry wastewater treatment

A study has been undertaken of an advanced wastewater treatment approach using polymer nanofiltration membranes, in an attempt to obtain water of sufficient quality to allow it to be reused in the same production process or, alternatively, to be discharged without any problems. The study has initially focused on the removal of organic matter (reduction of COD) and the most representative ions present in the wastewater, such as Na+ , Mg2+, Cl- , and SO4 2- . In a first part of the study, with a view to optimising the experimental phase, a simulation has been performed of the nanofiltration process using the NanoFlux software. Among other things, the simulation allows the most suitable membranes to be selected as a function of the permeate flow rate and desired level of retention in the substances to be removed. The subsequent experimentation was carried out in a laboratory tangential filtration system that works with flat membranes. It was found that retention values of about 90% were obtained for the studied substances, with a good permeate flow rate, using low operating pressures. These results demonstrate the feasibility of the studied technology and its potential as a treatment for improving ceramic industry wastewater qualit

Flexural and shear strengthening of reinforced concrete beams with a hybrid CFRP solution

An experimental program was carried out for assessing the performance of a hybrid solution composed by CFRP systems for the simultaneous flexural and shear strengthening of RC beams. CFRP laminates, applied according to NSM technique, are used for the flexural strengthening, while U‐shape CFRP discrete strips of wet lay‐up sheet, applied according to the EBR technique, are adopted for the shear strengthening. An anchorage system was applied at the extremities of these CFRP strips in an attempt of avoiding their premature debonding. The experimental results showed the hybrid strengthening solution is very effective, not only in terms of increasing the load carrying capacity of the beams, but also in assuring higher mobilization of the tensile capacity of the CFRP. The performance of the hybrid CFRP configuration that included the anchorage system for the shear strengthening was significantly higher than the one assured by other shear strengthening solutions that were applied in similar RC beams and tested until failure using the same test system adopted in this experimental program. The predictive performance of the ACI formulations proposed for estimating the contribution of CFRP systems for the flexural and shear resistance of RC beams was appraised considering the obtained experimental results.This work was supported by FEDER funds through the Operational Program for Competitiveness Factors ‐ COMPETE and National Funds through FCT ‐ Portuguese Foundation for Science and Technology under the project Spaflamis POCI‐01‐0145‐FEDER‐030956. The authors also acknowledges the support provided by the S&P® and “Empreiteiros Casais”

Implications of Halo Inside-out Growth on the X-Ray Properties of Nearby Galaxy Systems within the Preheating Scenario

We present an entirely analytic model for a preheated, polytropic intergalactic medium in hydrostatic equilibrium within a NFW dark halo potential in which the evolution of the halo structure between major merger events proceeds inside-out by accretion. This model is used to explain, within a standard $\Lambda$CDM cosmogony, the observed X-ray properties of nearby relaxed, non-cooling flow groups and clusters of galaxies. We find that our preferred solution to the equilibrium equations produces scaling relations in excellent agreement with observations, while simultaneously accounting for the typical structural characteristics of the distribution of the diffuse baryons. In the class of preheating models, ours stands out because it offers a unified description of the intrahalo medium for galaxy systems with total masses above \sm 2\times 10^{13}\msun, does not produce baryonic configurations with large isentropic cores, and reproduces faithfully the observed behavior of the gas entropy at large radii. All this is achieved with a moderate level of energy injection of about half a keV, which can be easily accommodated within the limits of the total energy released by the most commonly invoked feedback mechanisms, as well as with a polytropic index of 1.2, consistent with both many observational determinations and predictions from high-resolution gas-dynamical simulations of non-cooling flow clusters. More interestingly, our scheme offers a physical motivation for the adoption of this specific value of the polytropic index, as it is the one that best ensures the conservation after halo virialization of the balance between the total specific energies of the gas and dark matter components for the full range of masses investigated.Comment: 18 pages, 11 figures, accepted for publication in the Astrophysical Journa