Electronic Structure and Valence Band Spectra of Bi4Ti3O12

The x-ray photoelectron valence band spectrum and x-ray emission valence-band spectra (Ti K _beta_5, Ti L_alpha, O K_alpha) of Bi4Ti3O12 are presented (analyzed in the common energy scale) and interpreted on the basis of a band-structure calculation for an idealized I4/mmm structure of this material.Comment: 6 pages + 7 PostScript figures, RevTex3.0, to be published in Phys.Rev.B52 (Oct.95). Figures also available via anonymous ftp at ftp://ftp.physik.uni-osnabrueck.de/pub/apostnik/BiTiO

Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors

Layered d-metal pnictide oxides are a unique class of compounds which consists of characteristic d-metal pnictide layers and metal oxide layers. More than 100 of these layered compounds, including the recently discovered Fe-based superconducting pnictide oxides, can be classified into 9 structure types. These structure types and the chemical and physical properties of the characteristic d-metal pnictide layers and metal oxide layers of the layered d-metal pnictide oxides are reviewed and discussed. Furthermore, possible approaches to design new superconductors based on these layered d-metal pnictide oxides are proposed.Comment: 29 pages including 6 tables and 2 figure

Electronic structure and ferroelectricity in SrBi2Ta2O9

The electronic structure of SrBi2Ta2O9 is investigated from first-principles, within the local density approximation, using the full-potential linearized augmented plane wave (LAPW) method. The results show that, besides the large Ta(5d)-O(2p) hybridization which is a common feature of the ferroelectric perovskites, there is an important hybridization between bismuth and oxygen states. The underlying static potential for the ferroelectric distortion and the primary source for ferroelectricity is investigated by a lattice-dynamics study using the Frozen Phonon approach.Comment: 17 pages, 7 figures. Phys. Rev. B, in pres

Cerambycidae (Coleoptera) collected with light trap at 45 meters height over an Amazon forest canopy and the description of four new species

A list of 69 species of Cerambycidae collected at 45 m height in a metallic tower of 50 m height, in a "platô de terra firme", in the Cueiras River basin, "Estação Experimental de Silvicultura Tropical, km 14 do núcleo ZF-2" in Manaus, Amazonas, Brazil. The collections were carried out monthly from January to December of 2004, during three nights of lunar transition third quarter monn/new moon from 18 p.m. to 6 a.m. The insects were collected over a vertical white sheet illuminated by a 250 watts mixed light and a 20 watts black-light (BLB) lamps. Were collected Prioninae (12 species), Disteniidae (one species), Cerambycinae (27 species) and Lamiinae (29 species). New species described: Physopleurus rafaeli, sp. nov. (Prioninae, Macrotomini); Oncideres tuberosa sp. nov. (Lamiinae, Onciderini),Plistonax rafaeli sp. nov. (Lamiinae, Acanthoderini) e Hemiloapis mena sp. nov. (Lamiinae, Hemilophini). Notes for Oncideres phaetusa Dillon & Dillon, 1946, a modified key to the species of Physopleurus Lacordaire, 1869 and a key to the species of Hemiloapis Galileo & Martins, 2004 are presented.É apresentada uma relação das 69 espécies de Cerambycidae coletados a 45 m numa torre metálica de 50 m que ultrapassa a maioria das copas das árvores, num platô de terra firme, na bacia do Rio Cueiras, Estação Experimental de Silvicultura Tropical, km 14 do núcleo ZF-2 em Manaus, Amazonas, Brasil. As coletas foram realizadas de janeiro a dezembro de 2004, durante três noites de transição lunar minguante/nova de cada mês, das 18 às 6 horas. Os insetos foram capturados em um lençol iluminado com lâmpada de 250 watts, luz mista de vapor de mecúrio e lâmpada de 20 watts BLB. Foram coletados Prioninae (12 espécies), Disteniinae (uma espécie), Cerambycinae (27 espécies) e Lamiinae (29 espécies). Novas espécies descritasPhysopleurus rafaeli, sp. nov. (Prioninae, Macrotomini); Oncideres tuberosa sp. nov. (Lamiinae, Onciderini), Plistonax rafaeli sp. nov. (Lamiinae, Acanthoderini) e Hemiloapis mena sp. nov. (Lamiinae, Hemilophini). São apresentadas notas em Oncideres phaetusa Dillon & Dillon, 1946, chave que modifica aquela para as espécies de Physopleurus Lacordaire, 1869 e chave para as espécies de Hemiloapis Galileo & Martins, 2004