Identification and nonlinearity compensation of hysteresis using NARX models

This paper deals with two problems: the identification and compensation of hysteresis nonlinearity in dynamical systems using nonlinear polynomial autoregressive models with exogenous inputs (NARX). First, based on gray-box identification techniques, some constraints on the structure and parameters of NARX models are proposed to ensure that the identified models display a key feature of hysteresis. In addition, a more general framework is developed to explain how hysteresis occurs in such models. Second, two strategies to design hysteresis compensators are presented. In one strategy, the compensation law is obtained through simple algebraic manipulations performed on the identified models. In the second strategy, the compensation law is directly identified from the data. Both numerical and experimental results are presented to illustrate the efficiency of the proposed procedures. Also, it has been found that the compensators based on gray-box models outperform the cases with models identified using black-box techniques.

     

Determination of S(IV) Oxoanions at Poly[Ru(5‐NO2‐Phen)2Cl] Tetrapyridylporphyrin Glassy Carbon Modified Electrode

Glassy carbon electrodes modified with conducting polymers of Ni(II), Zn(II) and metal free tetraruthenated porphyrin were evaluated for reduction and oxidation processes of S(IV) oxoanions in Na₂SO₃/water‐ethanol at pH 1.0 and 3.5, showing electrocatalytic activity. A Ni(II) film was able to reduce the S(IV) oxoanions selectively in presence of high concentration of gallic acid. The Ni(II) film was also used as an amperometric sensor toward S(IV) oxoanions reduction in white wine samples showing a detection and quantification limit of 1.40 mg L^?1 and 4.68 mg L^?1, respectively. These results are promising for the electrochemical determination of S(IV) using conducting polymers from these macrocycles.     

Characterization of PVC-Tetraruthenated Metalloporphyrins Modified Electrodes: Application as Electrocatalyst in the Nitrite Reduction

Summary: This paper describes the electrochemical reduction of nitrite ion in 0.1 M NaClO₄, on glassy carbon or ITO electrodes modified with mixtures PVC- tetraruthenated metalloporphyrins. This electrode is able to keep the extraordinary electrocatalytic properties of the macrocycle allowing multielectronic transfers and a great stability as a consequence of the inclusion of the macrocycles into a polymeric support such as PVC. On the other hand, the electrochemical reduction of nitrite ion on these modified electrodes studied by cyclic voltammetry shows an enhancement in the current values and lower overpotential compared with the activity of the bare glassy carbon electrode. Controlled potential electrolysis experiments verify the production of ammonia, hydrazine and hydroxylamine, showing the electrocatalytic character and the stability of this modified electrode.     

Electrocatalytic reduction of carbon dioxide on conducting glass electrode modified with polymeric porphyrin films containing transition metals in ionic liquid medium

Electrocatalytic reduction of carbon dioxide has been studied using modified electrodes with conducting polymers from tetra-amino-phenyl porphyrins containing transition metals (Zn(II) and Fe(III)), on an indium tin oxide electrode in BMImBF₄, as solvent and supporting electrolyte. Electropolymerized Fe porphyrin is active toward the reaction under survey, while Zn derivative shows poor activity. Spectroelectrochemistry experiments on electropolymerized Fe porphyrin films have shown intermediary species like Fe–CO₂ and Fe–CO at open-circuit potential. Potential-controlled bulk electrolysis carried out in ionic liquid shows that only carbon monoxide can be detected as reaction product in the gas phase and that Fe polymeric film shows a turnover number of 9.18, while the Zn film shows a value of 2.74, corroborating the poor activity observed in cyclic voltammetry.     

LOWDIN: The any particle molecular orbital code

LOWDIN is a computational program that implements the Any Particle Molecular Orbital (APMO) method. The current version of the code encompasses Hartree–Fock, second‐order Møller–Plesset, configuration interaction, density functional, and generalized propagator theories. LOWDIN input file offers a unique flexibility, allowing users to exploit all the programs' capabilities to study systems containing any type and number of quantum species. This review provides a basic introduction to LOWDIN's key computational details and capabilities. © 2013 Wiley Periodicals, Inc.     

Controlled Synthesis of meso‐Veratrylporphyrins under Acid‐Catalyzed Scrambling Conditions

5,15‐Bis(veratryl)porphyrin (1), 5,10,15‐tris(veratryl)porphyrin (2), and 5,10,15,20‐tetrakis(veratryl)porphyrin (3), C₃₆H₃₀N₄O₄, C₄₄H₃₈N₄O_6, and C₅₂H₄₆N₄O₈ were synthesized by an acid‐catalyzed, one‐pot reaction of meso‐dipyrromethane, 3,4‐di‐OCH₃‐benzaldehyde (veratraldehyde), and trifluoroacetic acid (TFA). These three different products were obtained as a result of scrambling reactions. The molecular structures have been characterized by elemental analysis, ESI mass spectra, 1D and 2D NMR techniques (¹H and ¹³C), and UV‐visible spectroscopy.     

Pattern formation and encoding rhythms analysis on a spiking/bursting neuronal network

In this work we study the formation of patterns of neuronal activity when some input are presented to the network. For this task a recently developed model of neuron is utilized. This model requires a very low computational effort but presents many characteristics of more complex models such as, spiking, bursting and sub-threshold oscillations, and therefore the realistic study of the behavior of big ensembles of neurons can be aborded, even under real time conditions. New results of the application of the wavelet transform technique to the analysis of pattern formation and the possible encoding of rhythms are presented; they show that this simple, low-computational, neuron model behaves much like more complex ones.     

Crystal structure of dibenzoyl diselenide.

C14H10O2Se2 is monoclinic, P2(1)/c. The unit-cell dimensions at 293 K are a = 12.795(2), b = 12.126(2), c = 9.0179(13)A, beta = 107.074(6)degrees, V = 1337.5(3)A3, and Z = 4. The R value is 0.048 for 2319 observed reflections. The dihedral angle between the plane C4-C7(O2)-Se1 and C9-C8(O1)-Se2 is 85.6(2)degrees, keeping the Se atom unshared electron pairs in a more stable configuration with the rest of the molecule. The packing in the crystal is entirely due to van der Waals forces.     

New chiral Schiff base–Cu(II) complexes as cyclopropanation catalysts

A series of chiral Schiff base ligands 1–4, derived from (1R,2S)-(+)-cis-1-amino-2-indanol and other chiral amines with substituted salycilaldehydes were synthesized and transformed to the corresponding Cu(II) complexes. Molecular structures of six Cu(II) complexes were determined by X-ray crystallographic studies. The structures show the metal ion in a distorted square planar geometry with dimeric or monomeric structures, depending on the ligand denticity. The potential use of these complexes in asymmetric Cyclopropanation was explored.