Molecular tilting and columnar stacking of Fe phthalocyanine thin films on Au(111)

Scanning tunneling microscopy and x-ray absorption spectroscopic results at the Fe K edge of Fe phthalocyanine (FePc) thin films grown on Au substrates, together with theoretical calculations, allow us to refine the structure of the film. In particular, we show that the columnar stacking of the FePc molecules is different from that found in bulk ¿ and ß phases. Moreover, the molecules do not lay parallel to the surface of the substrate. These structural findings are relevant to understand magnetism of FePc films.The financial support of the Spanish financial agency MINECO MAT2011-2379 and MAT2014-53921-R, Aragonese DGA-IMANA E34 (co-funded by European Social Fund), as well as European Union FEDER funds is acknowledged. The sample preparation and initial structural characterization were supported by the Office of Basic Energy Science, U.S. Department of Energy, BES-DMS funded by the Department of Energy’s Office of Basic Energy Science, DMR under Grant No. DE FG03 87ER-45332 and NSF DMR 0847552.Peer Reviewe

Bartolomé de Las Casas y la idealización de las ciudades de los indios

En su discusión acerca del estatuto de los habitantes del Nuevo Mundo, Ginés de Sepúlveda y Bartolomé de Las Casas invocan razones tomadas del libro de la Política para justificar sus respectivas posiciones. El primero de ellos, sostiene que los indios corresponden a lo que Aristóteles entendía por esclavos por naturaleza. Aunque Sepúlveda no era partidario de esclavizarlos, sí consideraba legítimo someterlos por la fuerza, para civilizarlos y disponerlos a recibir la doctrina cristiana. Los españoles, por su parte, correspondían, según él, al modelo aristotélico de los amos por naturaleza. Las Casas, por su parte, busca destruir ambos supuestos. En el caso de los indios, hace ver que gozan de las virtudes que Aristóteles atribuye a los hombres libres y participan de la experiencia de la pólis, como se manifiesta por el carácter de sus ciudades, que Las Casas busca engrandecer, para conseguir que se asemejen al modelo aristotélico. Por otra parte, los vicios y el comportamiento de los conquistadores no corresponden a lo que sería propio de los hombres que son amos por naturaleza, con lo que termina por desmontar la construcción intelectual de su contradictorIn his discussion about the status of the inhabitants of the New World, Ginés de Sepúlveda and Bartolomé de Las Casas evoke arguments from the book I of Aristotle's Politics to justify their position. The first one says that the Indians correspond to what Aristotle understood as slaves by nature. Although Sepúlveda was not in favor of slavery, he considered that it was legitimate to submit them by force to civilize them and dispose them to receive the Christian doctrine. Spaniards, on their behalf, corresponded, according to him, to the Aristotelian model of the masters by nature. Las Casas, on the other hand, seeks to destroy both assumptions. In the case of the indians, he shows that they have virtues that Aristotle attributes to free men, and that they participate in the experience of the polis, thing that manifests itself by the characteristics of their cities, that Las Casas seeks to exalt to achieve a similarity to the Aristotelian model. On the other hand, the bad habits and behavior of the conquerors do not correspond to the ones that a master by nature should have, with which he ends up dismantling the intellectual construction of his contradictorFil: García Huidobro, Joaquín.Fil: Pérez Lasserre, Diego

A note on the link between public expenditures and distortionary taxation

This note deals with the optimal provision of a public good in the context of the Ramsey tax model. It is shown that the second-best level of public good provision is inefficiently low relative to a situation where additional expenditures can be financed by lump-sum taxation.distortionary taxation

Molecular tilting and columnar stacking of Fe phthalocyanine thin films on Au(111)

Scanning tunneling microscopy and x-ray absorption spectroscopic results at the Fe K edge of Fe phthalocyanine (FePc) thin films grown on Au substrates, together with theoretical calculations, allow us to refine the structure of the film. In particular, we show that the columnar stacking of the FePc molecules is different from that found in bulk a and ß phases. Moreover, the molecules do not lay parallel to the surface of the substrate. These structural findings are relevant to understand magnetism of FePc films

Aggregation state and magnetic properties of magnetite nanoparticles controlled by an optimized silica coating

The control of magnetic interactions is becoming essential to expand/improve the applicability of magnetic nanoparticles (NPs). Here, we show that an optimized microemulsion method can be used to obtain homogenous silica coatings on even single magnetic nuclei of highly crystalline Fe3-xO4 NPs (7 and 16nm) derived from a high-temperature method. We show that the thickness of this coating is controlled almost at will allowing much higher average separation among particles as compared to the oleic acid coating present on pristine NPs. Magnetic susceptibility studies show that the thickness of the silica coating allows the control of magnetic interactions. Specifically, as this effect is better displayed for the smallest particles, we show that dipole-dipole interparticle interactions can be tuned progressively for the 7 nm NPs, from almost non-interacting to strongly interacting particles at room temperature. The quantitative analysis of the magnetic properties unambiguously suggests that dipolar interactions significantly broaden the effective distribution of energy barriers by spreading the distribution of activation magnetic volumes. Published by AIP Publishing

Consumption Externalities and Pigouvian Ranking -- A Generalized Cobb-Douglas Example

This paper analyzes the impact of consumption externalities on the ``Pigouvian ranking,'' according to which the second-best level of public good provision is \emph{smaller} than the first-best level. Consumption externalities introduce exceptions to the Pigouvian ranking. Two necessary and sufficient conditions for reversal of the Pigouvian ranking are identified, when preferences for private goods (Cobb-Douglas) and the public good are weakly separable: (i) consumption generates a \emph{negative} externality, (ii) utility is not too concave in the subutility of private goods. If preferences are \emph{strongly} separable in the public good, the Pigouvian ranking is reversed if and only if the second-best consumption price is lower than the corrective (Pigouvian) consumption price.consumption externality public good provision, first-best, second-best, Pigouvian ranking

Status Effects, Public Goods Provision, and the Excess Burden

Most studies of the optimal provision of public goods or the excess burden from taxation assume that individual utility is independent of other individuals' consumption. This paper investigates public good provision and excess burden in a model that allows for interdependence in consumption in the form of status (relative consumption) effects. In the presence of such effects, consumption and labor taxes no longer are pure distortionary taxes but have a corrective tax element that addresses an externality from consumption. As a result, the marginal excess burden of consumption taxes is lower than in the absence of status effects, and will be negative if the consumption tax rate is below the "Pigouvian" rate. Correspondingly, when consumption or labor tax rates are below the Pigouvian rate, the second-best level of public goods provision is above the first-best level, contrary to findings from models without status effects. For plausible functional forms and parameters relating to status effects, the marginal excess burden from existing U.S. labor taxes is substantially lower than in most prior studies, and is negative in some cases.status effects, excess burden, deadweight loss, public goods provision, corrective taxation, consumption externality, first best, second best