Theoretical view on the origin and implications of structural distortions in polyoxometalates

Structural features of polyoxometalates (POMs) —versatile inorganic clusters of academic and technological interest— are discussed in the present article. POMs are, in general, very regular structures presenting a high symmetry in most cases. Distortions are, however, important for some electronic and magnetic properties. We herein discuss some particular geometric features that are crucial for the theoretical treatment and comprehension of well-known experimental phenomena. For instance, we have been able to understand and rationalize the geometrical distortions present in molybdenum POMs. Moreover, we can affirm that these geometrical distortions are caused by a pseudo Jahn Teller effect. In what concerns NMR chemical shifts, we present a discussion on the importance of geometry for the correct description of the signals and the key role played by the interatomic distances. Finally, a study on the adsorption of Keggin clusters on silver surfaces shows how the POM structure looses its regular shape to adapt to that new situation

L'Evolució dels mètodes de càlcul d'estructures durant el segle XX: dels mètodes gràfics a la irrupció dels computadors

The methods of calculation used in engineering, and specifically in structural design, have experienced a great development throughout the 20th century. From the manual methodologies to the present systems, mainly based on computer calculations, they have increased of unimaginable way the calculation capacity, as well as the precision, reliability and speed of calculation. The methods at the beginning of the century, that followed the previous graphical methods, with which they coexisted a long time, gave rise to iterative systems for solving equations. These methodologies evolved with the appearance of first computers, and the increase of the capacity of calculation, memory and speed, lead to an increase of the degree of sophistication and complexity of the used methods. In this article the basic characteristics of the evolution of the methods of analysis of structures and its implications for the professional and educational world are exposed. This evolution is exemplified through three significant methods: the graphical methods, the Cross method and the Finite Element Metho

Cuantificación del crecimiento de pliegues con sedimentos sintectónicos asociados: aplicación al anticlinal de Santarén (orógeno cubano, cuenca de antepaís de las Bahamas)

The Santaren anticline, located offshore, is the outermost structure of the Cuban fold and thrust belt. The detailed study of the geometry of the syntectonic sediments associated with this anticline has allowed us to document its kinematic evolution. A number of reverse modelling geometrical techniques have been used to quantify fold gr owth (crestal structural relief, shortening, limb dip, interlimb angle and axial plane dip) during different stages. The values obtained for each of these parameters have been plotted versus time in order to s h ow their evolution through time. The conclusions achieved from all these plots are consistent and enable us to understand how fold amplification took place. Thus, the data obtained indicate that fold gr owth initiated during Middle Eocene, or before, and it continued until present day. Fold amplification took place at extremately slow rates from Middle Miocene to present day, and perhaps faster during deposition of older growth strata. In particular, data concerning rotation of the southern limb and interlimb angle tightening support this hypothesis. The data presented in this paper regarding the Santaren anticline evolution disagree with previous plate tectonic models that postulate the end of tectonic activity in this region during Middle Eocene

Cuantificación del crecimiento de pliegues con sedimentos sintectónicos asociados: aplicación al anticlinal de Santarén (orógeno cubano, cuenca de antepaís de las Bahamas)

El estudio detallado de la geometría de los sedimentos sintectónicos asociados al crecimiento del anticlinal de Santaren, localizado bajo el mar en la parte más externa de la faja plegada cubana, ha permitido documentar la evolución cinemática de dicho pliegue. Para ello se han utilizado una serie de técnicas geométricas de modelización inversa que permiten cuantificar el crecimiento del pliegue en función de: el relieve estructural de la cresta, el acortamiento, el buzamiento de los flancos, el ángulo entre flancos y el buzamiento del plano axial para diferentes estadios durante el depósito de los sedimentos sintectónicos. Para cada uno de los parámetros, los valores obtenidos se representan en una gráfica con respecto a la edad correspondiente, y de esta manera se conoce su evolución a través del tiempo. Las conclusiones que se obtienen a partir de las diferentes gr á ficas son coherentes entre sí y permiten vislumbrar datos importantes de la evolución del pliegue. Así, los resultados obtenidos indican que el anticlinal se inició en el Eoceno Medio, o anteriormente, y su crecimiento perduró hasta la actualidad. El anticlinal creció de forma extremadamente lenta a partir del Mioceno Medio y tal vez lo hizo de forma mas rápida durante el depósito de los sedimentos sintectónicos más antiguos. En particular, los datos sobre la rotación del flanco sur del anticlinal y sobre la variación del ángulo entre flancos parecen estar de acuerdo con esta última hipótesis. Estos nuevos datos sobre la evolución del anticlinal de Santaren contradicen modelos previos que postulan que la deformación en esta región culminó en el Eoceno Medio.The Santaren anticline, located offshore, is the outermost structure of the Cuban fold and thrust belt. The detailed study of the geometry of the syntectonic sediments associated with this anticline has allowed us to document its kinematic evolution. A number of reverse modelling geometrical techniques have been used to quantify fold gr owth (crestal structural relief, shortening, limb dip, interlimb angle and axial plane dip) during different stages. The values obtained for each of these parameters have been plotted versus time in order to s h ow their evolution through time. The conclusions achieved from all these plots are consistent and enable us to understand how fold amplification took place. Thus, the data obtained indicate that fold gr owth initiated during Middle Eocene, or before, and it continued until present day. Fold amplification took place at extremately slow rates from Middle Miocene to present day, and perhaps faster during deposition of older growth strata. In particular, data concerning rotation of the southern limb and interlimb angle tightening support this hypothesis. The data presented in this paper regarding the Santaren anticline evolution disagree with previous plate tectonic models that postulate the end of tectonic activity in this region during Middle Eocene

Tutories de comunicacio intercultural per a la mobilitat internacional (alemany)

El projecte d´innovació docent que es presenta es porta a terme a la Facultat d´Economia i Empresa de la UB, i té com a objectiu desenvolupar la competència intercultural dels estudiants de mobilitat internacional (outgoers espanyols/catalans - incomers de païssos de parla alemanya) abans i durant la seva estada. Es presentaran les dues primeres fases del projecte, que consisteix en la realització de dues sessions presencials de tutories entre iguals i sensibilització i el treball en tàndems

Investigating the transformations of polyoxoanions using mass spectrometry and molecular dynamics

The reactions of [γ-SiW10O36]8– represent one of the most important synthetic gateways into a vast array of polyoxotungstate chemistry. Herein, we set about exploring the transformation of the lacunary polyoxoanion [β2-SiW11O39]8– into [γ-SiW10O36]8– using high-resolution electrospray mass spectrometry, density functional theory, and molecular dynamics. We show that the reaction proceeds through an unexpected {SiW9} precursor capable of undertaking a direct β → γ isomerization via a rotational transformation. The remarkably low-energy transition state of this transformation could be identified through theoretical calculations. Moreover, we explore the significant role of the countercations for the first time in such studies. This combination of experimental and the theoretical studies can now be used to understand the complex chemical transformations of oxoanions, leading to the design of reactivity by structural control

Experimental and numerical characterization of metallic studs

In this paper, the characterization of metallic studs used to mount lightweight double wall systems is studied both experimentally and numerically. The metallic studs are usually considered by introducing translational and rotational springs to couple the plasterboards composing the double wall. Therefore, the characterization involves determining these spring characteristics. The performance of this type of lightweight double wall in terms of sound transmission is presented in a companion paper. Different experimental setups have been investigated to determine the equivalent translational and rotational spring values. These experimental setups are described and involve the measurement of an input mobility. A finite element model of the laboratory tests has been developed. Shell and massive finite elements are employed in order to reproduce the experimental setups. A comparison of the measured and numerical results is shown. The FEM modelling is intended to help in developing new type of studs for double walls in order to obtain better sound transmission performance.Peer ReviewedPostprint (published version