Excitation Spectrum of One-dimensional Extended Ionic Hubbard Model

We use Perturbative Continuous Unitary Transformations (PCUT) to study the one dimensional Extended Ionic Hubbard Model (EIHM) at half-filling in the band insulator region. The extended ionic Hubbard model, in addition to the usual ionic Hubbard model, includes an inter-site nearest-neighbor (n.n.) repulsion, $V$. We consider the ionic potential as unperturbed part of the Hamiltonian, while the hopping and interaction (quartic) terms are treated as perturbation. We calculate total energy and ionicity in the ground state. Above the ground state, (i) we calculate the single particle excitation spectrum by adding an electron or a hole to the system. (ii) the coherence-length and spectrum of electron-hole excitation are obtained. Our calculations reveal that for V=0, there are two triplet bound state modes and three singlet modes, two anti-bound states and one bound state, while for finite values of $V$ there are four excitonic bound states corresponding to two singlet and two triplet modes. The major role of on-site Coulomb repulsion $U$ is to split singlet and triplet collective excitation branches, while $V$ tends to pull the singlet branches below the continuum to make them bound states.Comment: 10 eps figure

Estudo comparado da morfologia externa de Zaretis itys itylus (Westwood) e Agrias claudina annetta (Gray) (Lepidoptera, Nymphalidae, Charaxinae) I. Cabeça, apêndices e região cervical Comparative study of the external morphology of Zaretis itys itylus (Westwood) and Agrias claudina annetta (Gray) (Lepidoptera, Nymphalidae, Charaxinae). I. Head, appendages and cervical region

Realizou-se um estudo detalhado e comparado da morfologia externa da cabeça, apêndices e região cervical, de duas espécies de Charaxinae, Zaretis itys itylus (Westwood, 1850) e Agrias claudina annetta (Gray, 1832). Os resultados obtidos foram comparados com outros já publicados e relacionados com morfologia externa de outras subfamílias de Nymphalidae (Brassolinae, Morphinae, Danainae e Ithomiinae).<br>Two species of Charaxinae, Zaretis itys itylus (Westwood, 1850) and Agrias claudina annetta (Gray, 1832) were subject of a detailed and comparative study of external morphology of the head, appendages and cervical region. The results obtained were compared with other studies published and related to the external morphology of other Nymphalidae subfamilies (Brassolinae, Morphinae, Danainae and Ithomiinae)

Morfologia externa do adulto de Actinote melanisans (Nymphalidae: Heliconiinae: Acraeini)

A morfologia externa do adulto de A. melanisans Oberthür, 1917 é descrita e ilustrada. Os resultados obtidos foram comparados com outros já publicados para a morfologia externa de Nymphalidae (Danainae, Brassolinae/Brassolini sensu CASAGRANDE (2004), Morphinae/Morphini sensu LAMAS (2004a), Ithomiinae e Charaxinae). É apresentado um padrão para a caracterização morfológica do gênero, sendo esse o primeiro estudo detalhado de morfologia de uma espécie de Acraeini, agregando informações úteis para subsidiar a análise filogenética das espécies Neotropicais.<br>The external morphology of adult A. melanisans Oberthür, 1917 is described and illustrated. The results obtained were compared with other studies already published on the external morphology of Nymphalidae - Danainae: Brassolinae: Brassolini sensu CASAGRANDE (2004), Morphinae: Morphini sensu LAMAS (2004a), Ithomiinae and Charaxinae. A pattern for the morphological characterization of the genus is presented. It is the first detailed study of the morphology of a species of Acraeini, therefore contributing with information on characters useful for the phylogenetic analysis of the Neotropical species

Analysis of Lead in Soils Adjacent to an Interstate Highway in Tampa, Florida

In order to assess the amount and distribution of lead pollution in soils adjacent to a major interstate highway serving the city of Tampa, Florida, a total of 224 samples were collected from 32 transects perpendicular to the roadway. The lead content was measured using atomic absorption spectrophotometry. The highest levels of lead were found at distances of 81, 243, and 729 cm from the road. The results show that there is a weak negative correlation between soil lead and the distance from the roadside, as well as with traffic density. The weakness of the relationship is a result of confounding variables such as turbulence and other microclimatic factors, downslope movement of soils overtime, and human action such as construction and highway landscaping. Nevertheless, over one-third of the samples collected in the study area contain more than 500 μg g−1 lead, levels considered to be hazardous by the United States Centers for Disease Control and the Environmental Protection Agency