Electromechanical performance comparison for different CMUT element geometries

Conferencia celebrada en Sevilla (España) del 19 al 21 de septiembre del 2012.Different capacitive micromachined ultrasonic transducers (CMUTs) element geometries and fabrication techniques have been proposed through the years though the questions of which element geometry suits each application best as well as further geometrical, array and design parameter optimization techniques still remain open. This paper proposes a thorough comparison between square, hexagonal and circular CMUT elements and geometries through finite element method (FEM) simulations and provides results comparing their respective electromechanical parameters.Peer reviewe

Pushing the limits of concertedness. A waltz of wandering carbocations.

Among the array of complex terpene-forming carbocation cyclization/rearrangement reactions, the so-called "triple shift" reactions are among the most unexpected. Such reactions involve the asynchronous combination of three 1,n-shifts into a concerted process, e.g., a 1,2-alkyl shift followed by a 1,3-hydride shift followed by a second 1,2-alkyl shift. This type of reaction so far has been proposed to occur during the biosynthesis of diterpenes and the sidechains of sterols. Here we describe efforts to push the limits of concertedness in this type of carbocation reaction by designing, and characterizing with quantum chemical computations, systems that could couple additional 1,n-shift events to a triple shift leading, in principle to quadruple, pentuple, etc. shifts. While our designs did not lead to clear-cut examples of quadruple, etc. shifts, they did lead to reactions with surprisingly flat energy surfaces where more than five chemical events connect reactants and plausible products. Ab initio molecular dynamics simulations demonstrate that the formal minima on these surfaces interchange on short timescales, both with each other and with additional unexpected structures, allowing us a glimpse into a very complex manifold that allows ready access to great structural diversity

Notas corológicas de la provincia de Jaén. III. "Juncaceae"

Se presenta un catálogo de las especies de la familia Juncaceae existentes en la provincia de Jaén (España), que incluye 21 táxones, 6 de los cuales son primera cita provincial.In this paper we present a catalogue of Juncaceae species from the province of Jaén (S. E. Spain) wich includes 21 taxa, 6 are new in the zone

Dynamics of Coherent States in Regular and Chaotic Regimes of the Non-integrable Dicke Model

The quantum dynamics of initial coherent states is studied in the Dicke model and correlated with the dynamics, regular or chaotic, of their classical limit. Analytical expressions for the survival probability, i.e. the probability of finding the system in its initial state at time $t$, are provided in the regular regions of the model. The results for regular regimes are compared with those of the chaotic ones. It is found that initial coherent states in regular regions have a much longer equilibration time than those located in chaotic regions. The properties of the distributions for the initial coherent states in the Hamiltonian eigenbasis are also studied. It is found that for regular states the components with no negligible contribution are organized in sequences of energy levels distributed according to Gaussian functions. In the case of chaotic coherent states, the energy components do not have a simple structure and the number of participating energy levels is larger than in the regular cases.Comment: Contribution to the proceedings of the Escuela Latinoamericana de F\'isica (ELAF) Marcos Moshinsky 2017. (9 pages, 4 figures

A METHOD TO OBTAIN RELATIVELY UNIFORM BREADFRUIT TREES FROM A STOCKPLANT

A METHOD TO OBTAIN RELATIVELY UNIFORM BREADFRUIT TREES FROM A STOCKPLAN