Papers by Maria Pilar Mareca
2016 11th Iberian Conference on Information Systems and Technologies (CISTI), 2016
2016 11th Iberian Conference on Information Systems and Technologies (CISTI), 2016
Bonding of benzene molecules on the surface of neutral and charged Fe7 clusters, which have penta... more Bonding of benzene molecules on the surface of neutral and charged Fe7 clusters, which have pentagonal bipyramids (PBP), was studied by means of all–electrons density functional calculations. Dispersion corrections were done with the BPW91-D2 method using the 6-311++G(2d,2p) basis sets. With two less coordinated equatorial sites (bonded to four iron atoms) and one axial site (bonded to five atoms), a triangular face of Fe7 emerges as the basic unit for the absorption of benzene moieties. Bonding of benzene (Bz) on such triangle yields the ground state (GS) for Fe7Bz, Fe7Bz–, and Fe7Bz+. Without dispersion, in the GS of Fe7Bz–, the ligand is η6 coordinated with a single equatorial iron site, and in the GSs of Fe7Bz2 and Fe7Bz2–, each benzene moiety is η6 bonded on opposite equatorial sites. However, BPW91-D2 yields GS structures for Fe7Bz2, Fe7Bz2–, and Fe7Bz2+, where the absorption is done on opposite triangles. Therefore, dispersion corrections are crucial for a proper study of Fe7Bz2. The multiplicities (M = 2S + 1, where S is the total spin) of these species, 17, 16, and 18, respectively, are smaller than those of Fe7(23), Fe7–(22) and Fe7+(24) showing important quenching of the magnetic moment of Fe7. Bond dissociation energies (BDE), in kcal/mol, for Fe7Bz (32.7), Fe7Bz+ (47.3), and Fe7Bz– (27.2) show bigger (smaller) values for the cation (anion). A similar picture was found for the BDEs of Fe7Bz2. Ionization energies, 5.37 and 4.94 eV, for m = 1 and 2 are smaller than that of Fe7, 6.00 eV; which is due to delocalization of the electrons through the network of 3d-π bonds. Electron affinities of Fe7Bz1,2 are also smaller that of Fe7, being mainly due to the increased repulsion.
This paper describes and analyzes how the cooperation of Engineering students in a Wikipedia edit... more This paper describes and analyzes how the cooperation of Engineering students in a Wikipedia editing project helped to improve their learning and understanding of Physics. This project aims to incorporate to the first University Courses other forms of learning, including specifically the communication of scientific concepts to other students and general audiences. Students have been in accordance to say that with the Wikipedia project have learned to work better together and helped them gain insight into the concepts of Physics.
Bonding in transition-metal molecules presents novel features: (i) s electron bonding is overcome... more Bonding in transition-metal molecules presents novel features: (i) s electron bonding is overcome by multiple d electron bonding, (ii) intraatomic exchange favoring atomic magnetization competes with bonding that tends to pair the electrons, and (iii) in the heteronuclear dimers, the ionic terms may be important due to strong charge-transfer effects. The NbIr heteronuclear diatomic molecule shows all these features clearly. The cellular multiple scattering-xαβ calculation presented in this paper shows the ground state to correspond to antiferromagnetic coupling between the highly magnetic Nb atom and the Ir atom. A one-electron charge transfer from Nb to Ir was found; the result is an ionic structure, Nb+Ir−, for the dimer. The computed equilibrium distance, 4.100 a.u., corresponds to a region where d bonding strongly overcomes the s bonding, which alone would have stabilized the molecule at 5.950 a.u. At intermediate interatomic separations, 5.35 a.u., the NbIr system has a state in which all molecular orbitals are bonding with a high hybridization between the ns and (n − 1)d electrons of each atom, resulting in a (almost entirely) covalent high multiple-bond formation for this meta-stable state of the dimer.
The weight of the chaotic non-linear dynamical systems is increasingly more important in sectors ... more The weight of the chaotic non-linear dynamical systems is increasingly more important in sectors such as sciences, engineering, health, and, even, economy. This fact pushes the educative community toward the challenge of designing learning methodologies which enables to understand of the chaotic phenomenon. In this paper we propose an educative software application, easily accessible for medium level undergraduates with some knowledge of the foundations of Chaos Theory. This MATLAB application (called CAOS SUITE) allows students to simulate the system’s temporal evolution, to see its corres-pondence in the phase space, to analyze the convergence problems in the Lyapunov’s exponents calculation, and to obtain the complexity degree of the studied system by means of the Kaplan-Yorke dimension. The dynamical systems analyzed cover from basics type Jerk to complex systems with Hyperchaos.
The XXI century companies are increasingly interested on in the development of complex processes ... more The XXI century companies are increasingly interested on in the development of complex processes on bioengineering and health sciences. In this context, it is essential for undergraduate and graduate students to understand the behavior of complex phenomena. However, nowadays, academic programs are limited to the study of linear systems and first-order approximations; while companies use sophisticated software applications applied to complex systems, whose results have to be interpreted. In order to bridge this gap, in this paper we propose a learning methodology based on working with simulation programs of non-linear dynamical systems and chaos to treat complexity, applied to bioengineering. In particular, in this work we make a software application to analyzing three interesting studies in the context of biological systems: a nonlinear electrical oscillator that is a paradigm of self-sustained oscillations, a heartbeat model based on this oscillator, and the Brusselator system to model autocatalytic biochemical reactions. As a result, we are proving how it is possible, with this application, to analyze the complex behavior and the anomalies in biological systems with this methodology. By means of the proposed software applications in this paper, we analyze and facilitate the learning involving models closer to the real world
A new four-dimensional, hyperchaotic dynamic system, based on Lorenz dynamics, is presented. Besi... more A new four-dimensional, hyperchaotic dynamic system, based on Lorenz dynamics, is presented. Besides, the most representative dynamics which may be found in this new system are located in the phase space and are analyzed here. The new system is especially designed to improve the complexity of Lorenz dynamics, which, despite being a paradigm to understand the chaotic dissipative flows, is a very simple example and shows great vulnerability when used in secure communications. Here, we demonstrate the vulnerability of the Lorenz system in a general way. The proposed 4D system increases the complexity of the Lorenz dynamics. The trajectories of the novel system include structures going from chaos to hyperchaos and chaotic-transient solutions. The symmetry and the stability of the proposed system are also studied. First return maps, Poincaré sections, and bifurcation diagrams allow characterizing the global system behavior and locating some coexisting structures. Numerical results about the first return maps, Poincaré cross sections, Lyapunov spectrum, and Kaplan-Yorke dimension demonstrate the complexity of the proposed equations.
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Papers by Maria Pilar Mareca