Investigation of the electrical and electrochemical properties of nanocomposites from V2O5, polypyrrole, and polyaniline

In this work, an investigation of the electrical and electrochemical properties responsible for the energy storage capability of nanocomposites has been carried out. We demonstrate that, in the case of the V2O5 xerogel and the nanocomposites polypyrrole (Ppy)/V2O5 and polyaniline (PANI)/V2O5, the quadratic logistic equation (QLE) can be used to fit the inverse of the resistance values as a function of the injected charge in non-steady-state conditions. This contributes to a phenomenological understanding of the lithium ion and electron transport. The departure of the experimental curve from the fitting observed for the V2O5 xerogel can be attributed to the trapping sites formed during the lithium electroinsertion, which was observed by electrochemical impedance spectroscopy. The amount of trapping sites was obtained on the basis of the QLE. Similar values used to fit the inverse of the resistance were also used to fit the absorbance changes, which is also associated with the small polaron hopping from the V(IV) to the V(V) sites. On the other hand, there was good agreement between the experimental and the theoretical data when the profile of the inverse of the resistance as a function of the amount of inserted lithium ions of the nanocomposites Ppy/V2O5 and PANI/ V2O5 was concerned. We suggest that the presence of the conducting polymers is responsible for the different electrical profile of the V2O5 xerogel compared with those of the nanocomposites. In the latter case, interactions between the lithium ions and oxygen atoms from V2O5 are shielded, thus decreasing the trapping effect of lithium ions in the V2O5 sites. The different values of the lithium ion diffusion coefficient into these intercalation materials are in agreement with this hypothesis.

Ferromagnetism, paramagnetism, and a Curie-Weiss metal in an electron-doped Hubbard model on a triangular lattice

Motivated by the unconventional properties and rich phase diagram of NaxCoO2 we consider the electronic and magnetic properties of a two-dimensional Hubbard model on an isotropic triangular lattice doped with electrons away from half-filling. Dynamical mean-field theory (DMFT) calculations predict that for negative intersite hopping amplitudes (t < 0) and an on-site Coulomb repulsion, U, comparable to the bandwidth, the system displays properties typical of a weakly correlated metal. In contrast, for t > 0 a large enhancement of the effective mass, itinerant ferromagnetism, and a metallic phase with a Curie-Weiss magnetic susceptibility are found in a broad electron doping range. The different behavior encountered is a consequence of the larger noninteracting density of states (DOS) at the Fermi level for t > 0 than for t < 0, which effectively enhances the mass and the scattering amplitude of the quasiparticles. The shape of the DOS is crucial for the occurrence of ferromagnetism as for t > 0 the energy cost of polarizing the system is much smaller than for t < 0. Our observation of Nagaoka ferromagnetism is consistent with the A-type antiferromagnetism (i.e., ferromagnetic layers stacked antiferromagnetically) observed in neutron scattering experiments on NaxCoO2. The transport and magnetic properties measured in NaxCoO2 are consistent with DMFT predictions of a metal close to the Mott insulator and we discuss the role of Na ordering in driving the system towards the Mott transition. We propose that the Curie-Weiss metal phase observed in NaxCoO2 is a consequence of the crossover from a bad metal with incoherent quasiparticles at temperatures T > T-* and Fermi liquid behavior with enhanced parameters below T-*, where T-* is a low energy coherence scale induced by strong local Coulomb electron correlations. Our analysis also shows that the one band Hubbard model on a triangular lattice is not enough to describe the unusual properties of NaxCoO2 and is used to identify the simplest relevant model that captures the essential physics in NaxCoO2. We propose a model which allows for the Na ordering phenomena observed in the system which, we propose, drives the system close to the Mott insulating phase even at large dopings.

A new integrable model of strongly correlated electrons with Hubbard-like interaction

A new completely integrable model of strongly correlated electrons is proposed which describes two competitive interactions: one is the correlated one-particle hopping, the other is the Hubbard-like interaction. The integrability follows from the fact that the Hamiltonian is derivable from a one-parameter family of commuting transfer matrices. The Bethe ansatz equations are derived by algebraic Bethe ansatz method.

Temperature dependence of polaronic transport through single molecules and quantum dots

Motivated by recent experiments on electric transport through single molecules and quantum dots, we investigate a model for transport that allows for significant coupling between the electrons and a boson mode isolated on the molecule or dot. We focus our attention on the temperature-dependent properties of the transport. In the Holstein picture for polaronic transport in molecular crystals the temperature dependence of the conductivity exhibits a crossover from coherent (band) to incoherent (hopping) transport. Here, the temperature dependence of the differential conductance on resonance does not show such a crossover, but is mostly determined by the lifetime of the resonant level on the molecule or dot.

Group displays in pale-winged starlings

Cliff-nesting pale-winged starlings (Onychognathus nabouroup) gather on the cliff tops to perform Group Displays which include both aggressive and courtship elements: Hopping, Wing Stretching, Wing Drooping, Wing Flicking, Staring, Head Forward Threat and Butterfly Fluttering. These displays occur throughout the year, most frequently in the late afternoon. We suggest that this behaviour may be important in pair formation, and in establishing dominance relationships between birds breeding at the same site.

alpha-conotoxins PnIA and [A10L] PnIA stabilize different states of the alpha 7-L247T nicotinic acetylcholine receptor

The effects of the native alpha-conotoxin PnIA, its synthetic derivative [ A10L] PnIA and alanine scan derivatives of [ A10L] PnIA were investigated on chick wild type alpha7 and alpha7-L247T mutant nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes. PnIA and [A10L] PnIA inhibited acetylcholine (ACh)-activated currents at wtalpha7 receptors with IC50 values of 349 and 168 nM, respectively. Rates of onset of inhibition were similar for PnIA and [ A10L] PnIA; however, the rate of recovery was slower for [ A10L] PnIA, indicating that the increased potency of [ A10L] PnIA at alpha7 receptors is conveyed by its slower rate of dissociation from the receptors. All the alanine mutants of [ A10L] PnIA inhibited ACh-activated currents at wtalpha7 receptors. Insertion of an alanine residue between position 5 and 13 and at position 15 significantly reduced the ability of [ A10L] PnIA to inhibit ACh-evoked currents. PnIA inhibited the non-desensitizing ACh-activated currents at alpha7-L247T receptors with an IC50 194 nM. In contrast, [ A10L] PnIA and the alanine mutants potentiated the ACh-activated current alpha7-L247T receptors and in addition [ A10L] PnIA acted as an agonist. PnIA stabilized the receptor in a state that is non-conducting in both the wild type and mutant receptors, whereas [ A10L] PnIA stabilized a state that is non-conducting in the wild type receptor and conducting in the alpha7-L247T mutant. These data indicate that the change of a single amino acid side-chain, at position 10, is sufficient to change the toxin specificity for receptor states in the alpha7-L247T mutant.

Boletim eletr??nico de bibliografias especializadas: igualdade de g??nero

A 2?? edi????o de 2013 do Boletim Eletr??nico de Bibliografias Especializadas destaca o tema Igualdade de G??nero. O documento traz indica????es de pu-blica????es do acervo da Biblioteca Graciliano Ramos/ENAP com reflex??es acerca das desi-gualdades entre homens e mulheres e suas consequ??ncias ?? sociedade. O objetivo ?? dar publicidade a esses materiais, visando a con-tribuir para uma melhor compreens??o do com-plexo cen??rio de defini????o das prioridades p??blicas e da formula????o de pol??ticas p??blicas governamentais comprometidas com a pers-pectiva de g??nero, em seus diversos aspectos. De acordo com a Organiza????o das Na????es Unidas para a Educa????o, a Ci??ncia e a Cultura (Unesco), os direitos das mulheres devem ser entendidos como direitos humanos e cultu-rais fundamentais. J?? a Pol??tica Nacional para as Mulheres, coordenada pela Secre-taria Especial de Pol??ticas para as Mulhe-res (SPM), da Presid??ncia da Rep??blica, tem como pressupostos e princ??pios a equi-dade, a autonomia das mulheres, a laicida-de do Estado, a universalidade das pol??ti-cas, a justi??a social, a transpar??ncia dos atos p??blicos, a participa????o e o controle social.

Boletim eletr??nico de bibliografias especializadas: pol??tica energ??tica - setor el??trico

A implementa????o de uma Pol??tica Energ??tica ?? essencial para o desenvolvimento do Pa??s, na medida em que estabelece metas, meios e diretrizes para melhorar a confiabilidade e a qualidade do suprimento energ??tico. Ela define ainda o papel dos diversos agentes e institui????es que atuam na ??rea energ??tica brasileira. A exist??ncia de tal pol??tica ?? condi????o fundamental para garantir o planejamento das atividades energ??ticas, tanto do lado da produ????o quanto do consumo, sem comprometer o meio ambiente e a qualidade de vida das pr??ximas gera????es. Em fun????o da import??ncia da pol??tica energ??tica ao desenvolvimento sustent??vel e ?? melhoria do bemestar da popula????o brasileira, a 1?? edi????o de 2013 do Boletim Eletr??nico de Bibliografias Especializadas destaca o tema Pol??tica Energ??tica - Setor El??trico, com indica????es de publica????es pertencentes ao acervo da Biblioteca Graciliano Ramos/ENAP. O intuito ?? divulgar obras que possam auxiliar gestores, servidores e trabalhadores da ??rea de Energia no Brasil em seus processos decis??rios, assim como obras que tratam da rica hist??ria do setor e seus planos para o futuro.

Boletim eletr??nico de bibliografias especializadas: gest??o de risco

O tema escolhido ?? Gest??o de Risco, que aborda quest??es emergenciais como a identifica????o de fatores cr??ticos para o sucesso da gest??o e a avalia????o de oportunidades em contextos adversos, imprescind??vel ao planejamento e ?? implementa????o de pol??ticas p??blicas.

Boletim eletr??nico de bibliografias especializadas: gest??o de conflito

O assunto ?? de extrema import??ncia para os processos de avalia????o e enfrentamento de situa????es de diverg??ncias de modo a prevenir seus efeitos negativos, bem como extrair os aspectos positivos, buscando, assim, comunica????o e negocia????o de maneira estrat??gica.

Boletim eletr??nico de bibliografias especializadas: gest??o de crise

O terceiro Boletim de Bibliografias Especializadas apresenta o tema ???Gest??o de Crise???, com indica????es de livros e artigos de revistas sobre o tema pertencentes ao acervo da Biblioteca. Essas publica????es mostram que a gest??o de crise ?? uma problem??tica com a qual toda administra????o deve preocupar-se. Afinal, crise ?? um evento imprevis??vel capaz de provocar preju??zos significativos a uma institui????o e, consequentemente, aos seus integrantes. Uma quest??o que se apresenta ??: depois da crise instaurada, como gerenci??-la? O conhecimento das caracter??sticas de uma crise possibilitar?? compreend??-la melhor e facilitar?? o ??rduo esfor??o em gerenci??-la.

Boletim eletr??nico de bibliografias especializadas: inova????o na gest??o p??blica

O 4?? Boletim Eletr??nico de Bibliografias Especializadas destaca o tema ???Inova????o na Gest??o P??blica???, com indica????es de livros e artigos de revistas pertencentes ao acervo da Biblioteca. O intuito ?? divulgar obras que auxiliem servidores p??blicos na transforma????o de processos de trabalho para melhor atender ao cidad??o.

Boletim eletr??nico de bibliografias especializadas:acesso ?? informa????o p??blica

A Lei de Acesso ?? Informa????o (n??12.527/2011) entra em vigor hoje, dia 16 de maio, e traz importantes mudan??as para a administra????o p??blica. A nova legisla????o proporciona, ao cidad??o brasileiro, o acesso amplo ??s informa????es e a documentos p??blicos sob a guarda do Estado. A partir dessa data, todo cidad??o poder??, a qualquer momento, solicitar informa????es diversas, sem necessidade de motiva????o para seu uso, garantindo, assim, o exerc??cio de seu direito constitucional ao acesso ?? informa????o p??blica. A Lei estabelece que o acesso seja a regra e o sigilo, a exce????o. Diante desse cen??rio, o 5?? Boletim Eletr??nico de Bibliografias Especializadas destaca o tema ???Acesso ?? informa????o???, com indica????es de publica????es pertencentes ao acervo da Biblioteca Graciliano Ramos/ENAP. O intuito ?? divulgar obras que auxiliem servidores p??blicos na compreens??o dos princ??pios da nova Lei e na mudan??a da cultura do sigilo, ainda presente na gest??o da informa????o p??blica.

Boletim eletr??nico de bibliografias especializadas:gest??o da informa????o e do conhecimento

O acesso ?? Informa????o proporcionado pela Lei n??12.527/2011, que entrou em vigor dia 16 de maio, pela qual o cidad??o brasileiro teve garantido o seu direito ao acesso amplo ??s informa????es e a documentos p??blicos, tamb??m provocou o incentivo necess??rio para aprofundar a discuss??o de temas importantes, relacionados ?? informa????o p??blica como a gest??o documental, a seguran??a da informa????o, a gest??o da informa????o e a gest??o do conhecimento. Este Boletim tem por objetivo indicar livros e artigos que tratam da tem??tica, e possam auxiliar os servidores p??blicos nesta discuss??o, uma vez que, gerenciar o conhecimento tornou-se uma necessidade e uma responsabilidade da Administra????o P??blica para que ela possa aumentar a efetividade dos servi??os p??blicos e melhorar a sociedade a qual ela serve.