Electron microscopy study of lizard spermiogenesis in Tropidurus torquatus (Lacertilia)

In the course of an investigation on lizard spermiogenesis, the authors have observed events connected with the differentiation of the acrosome and middle-piece of the spermatozoa. Some differences from other reptilians were found as well as: the presence of a subacrosomal space, the absence of the fibrous sheath in the middle-piece, and a very short neck in the mature spermatozoa.

Single top quark at future hadron colliders: Complete signal and background study

We perform a detailed theoretical study including decays and jet fragmentation of all the important modes of single top quark production and all the basic background processes at the upgraded Fermilab Tevatron and CERN LHC colliders. Special attention is paid to the complete tree level calculation of the QCD fake background which was not considered in previous studies. An analysis of the various kinematical distributions for the signal and backgrounds allow us to work out a set of cuts for an efficient background suppression and extraction of the signal. It is shown that the signal to background ratio after optimized cuts could reach about 0.4 at the Tevatron and 1 at the LHC. The remaining after cuts signal rate at the LHC for the lepton+jets signature is expected to be about 6.1 pb and will be enough to study single top quark physics even during LHC operation at a low luminosity. ©1999 The American Physical Society.

Contracted GTF basis sets applied to the theoretical interpretation of the Raman spectrum of hexaaquachromium(III) ion

Contracted GTF basis sets designed with aid of the Generator Coordinate Hartree-Fock (GCHF) method for H(2S), O2-(1S), and Cr3+(4F) atomic species are applied to perform theoretical interpretation of the Raman spectrum of hexaaquachromium(III) ion. The 16s, 16s 10p, and 24s17p13d GTF basis sets were contracted to [4s] for H atom, [6s4p], and [9s6p3d] for O2- and Cr3+, respectively, by Dunning's scheme. For Cr3+, the [9s6p3d] basis set was enriched with f polarization function and used in combination com [4s] and [6s4p] in the study of our interest. The results obtained in this report show that the contracted GTF basis sets used are a useful alternative for the theoretical interpretation of Raman spectrum of hexaaquachromium(III) ion and that GCHF method is an effective alternative to selection of GTF basis sets for theoretical study of vibrational properties of poliatomic species. © 2003 Elsevier Science B.V. All rights reserved.

Theoretical and experimental evaluation of the influence of the length of drill rods in the SPT-T test

The influence of soil drill rod length on the N value in the SPT-T test has been studied extensively by Mello (1971), Schmertmann & Palacios (1979), Odebrecht et al. (2002) and Cavalcante (2002). This paper presents an analysis of the Standard Penetration Test supplemented with torque measurement (SPT-T). A theoretical study of the resistance of the rod material to torsion and bending indicated that the shear stress caused by the rod self-weight represents less than 1% of that caused by the torsional moment. An experimental study with electric torquemeters attached to a horizontal rod system, as well as two field tests in the vertical direction, were also carried out to compare and substantiate the results. The purpose of these tests was to analyze changes along the length of the rod in response to successive increments at 1-meter intervals. Torque measurements were taken at each increment of the length to ascertain the accuracy of the theoretical data. The difference between the applied torque and the measured torque at the end of rod system was lower than the minimum scale of mechanical torquemeters used in practice.

A theoretical investigation of the structural and eletronic properties of orthorhombic CaZrO3

A CaZrO3 (CZO) powder was prepared by the soft chemical, polymeric precursor method (PPM). The CZO crystalline structure was investigated by powder X-ray diffraction (XDR), Retvield Refinament data, Raman spectra and ultraviolet–visible absorption spectroscopy. A theoretical study was performed using a periodic quantum mechanical calculation (CRYSTAL09 program). The periodic model built for the crystalline CZO structure was consistent with the experimental data obtained from structural and electronic properties. These results show that the material has an orthorhombic structure with experimental and theoretical gap values of 5.7 eV and 6.2 eV, respectively. In this article, we discuss the hybridization process of the oxygen p-orbitals and of the zirconium d-orbitals and analyze their band structures and density of states (partial and total).

Juízos e valores morais: a perspectiva de investigação dos modelos organizadores do pensamento

As ideias propostas neste estudo teórico têm como objetivo ampliar as perspectivas de investigação sobre juízos e valores morais. Após uma reflexão crítica sobre teorias que contribuíram com importantes conceitos no campo da Psicologia Moral, foram feitos alguns apontamentos que nos parecem promissores nessa área, tendo por referencial teórico-metodológico a Teoria dos Modelos Organizadores do Pensamento. Essa teoria procura destacar que apenas os recursos cognitivos operatórios não são suficientes para explicar como o sujeito apreende e julga a realidade. Nessa perspectiva, conclui-se como fundamental o papel dos conteúdos na organização das representações mentais relacionadas aos juízos e valores morais.

Desenvolvimento de um protótipo de um atlas escolar interativo: projeto e produção

This paper aims at presenting an Interactive School Atlas prototype which was developed for cartography and environmental education. The methodology was based on the theoretical study about child mental development of Piaget theory, in order to elaborate strategies that allow the student a better comprehension about the spatial information understanding. It was defined as study case of sixth grade students, because they belong to the Formal Operation stage, in which the children reach the needed mental operations for understanding cartographic key concepts. This Atlas was developed in two stages: cartographic design and Atlas production. The Atlas implementation was developed seeking the use of Multimedia Cartography and animation resources that may attract students and teachers, instigating them to explore the tools and strategies to lead users to a correct interpretation of map contents. The Atlas was implemented by using the Macromedia Flash and Visual Basic softwares and the MapObjects library. Though the map has bot been evaluated yet, one should point out that it was designed according to the theoretical and methodological knowledge of the cognitive development and its relationship to cartographic conceptions, aiming at adapting the product to children cognitive skills.

Magnetic properties of synthetic eumelanin - Preliminary results

We report an experimental and theoretical study of magnetic properties of synthetic eumelanin. The magnetization curves are determined by using both a vibrating sample magnetometer and a superconducting quantum interferometer device in an extended range of magnetic fields ranging from -10 kOe to 10 kOe at different temperatures. We find that the eumelanin magnetization can be qualitatively explained in terms of a simple model of dipolar spheres with an intrinsic magnetic moment. The latter one is experimentally measured by using X-band electron paramagnetic resonance. Our findings indicate that synthetic melanins are superparamagnetic.

Strutural and optical approach of CdS@ZnS core-shell system

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Resiliência no trabalho contemporâneo: promoção e/ou desgaste da saúde mental

Este estudo teórico resgata a concepção processual e contextual de resiliência, a qual compreende esse fenômeno enquanto relação complexa entre indivíduo e ambiente na produção de fatores de risco e no provimento de fatores protetores da subjetividade do indivíduo, buscando aplicá-la à realidade organizacional, haja vista que o mundo do trabalho contemporâneo demanda uma força de trabalho específica, qual seja, o trabalhador flexível, polivalente, sujeito a mudanças - portanto, um trabalhador resiliente. A partir dessas considerações, realiza-se um processo de reflexão sobre as situações em que a resiliência pode ser promotora de saúde mental, bem como acerca dos contextos que contribuem para o processo de adoecimento do trabalhador, buscando aventar possibilidades de atuação do profissional psicólogo diante de um contexto de trabalho adverso, considerando-se que o principal objetivo dessa atuação profissional é garantir a proteção/promoção da saúde e qualidade de vida no ambiente de trabalho.

A metodologia sistêmica na geografia agrária: um estudo sobre a territorialização dos assentamentos rurais

Este artigo tem como objetivo demonstrar a importância da metodologia sistêmica em pesquisas nas Ciências Humanas, em especial na Geografia Agrária, através da avaliação das alterações socioeconômicas e territoriais dos assentamentos rurais. O artigo foi divido em partes, primeiro foi realizado um estudo teórico da metodologia sistêmica e em seguida, a aplicação dessa metodologia para avaliar os impactos da territorialização dos assentamentos rurais, na organização espacial de Candiota no estado do Rio Grande do Sul.

The role of defect states in the creation of photoluminescence in SrTiO3

We discuss the nature of visible photoluminescence at room temperature in amorphous strontium titanate in the light of the results of a recent experimental and quantum mechanical theoretical study. Our calculation of the electronic structure involves the use of first-principles molecular calculations to simulate the variation of the electronic structure in the strontium titanate crystalline phase, which is known to have a direct band gap, and we also make an in-depth examination of amorphous strontium titanate. The results of our simulations of amorphous strontium titanate indicate that the formation of five-fold coordination in the amorphous system may introduce delocalized electronic levels in the highest occupied molecular orbital and the lowest unoccupied molecular orbital. These delocalized electronic levels are ascribed to the formation of a tail in the absorbance-spectrum curve. Optical absorption measurements experimentally showed the presence of a tail. The results are interpreted by the nature of these exponential optical edges and tails associated with defects promoted by the disordered structure of the amorphous material. We associate them with localized states in the band gap.

Mechanisms behind blue, green, and red photoluminescence emissions in CaWO4 and CaMoO4 powders

A combined experimental and theoretical study was conducted to analyze the photoluminescence (PL) properties of ordered and disordered CaWO4 (CW) and CaMoO4 (CM) powders. Two mechanisms were found to be responsible for photoluminescence emission in CW and CM powders. The first one, in the disordered powders, was caused by oxygen complex vacancies [MO3 center dot V-O(x)], [MO3 center dot V-O(center dot)] and [MO3 center dot V-O(center dot center dot)], where M=W or Mo, which leads to additional levels in the band gap. The second mechanism, in ordered powders, was caused by an intrinsic slight distortion of the [WO4] or [MoO4] tetrahedral in the short range. (c) 2007 American Institute of Physics.

BaZrO3 Photoluminescence Property: An Ab Initio Analysis of Structural Deformation and Symmetry Changes

This article reports a theoretical study based on experimental results for barium zirconate, BaZrO3 (BZ) thin films, using periodic mechanic quantum calculations to analyze the symmetry change in a structural order-disorder simulation. Four periodic models were simulated using CRYSTAL98 code to represent the ordered and disordered BZ structures. The results were analyzed in terms of the energy level diagrams and atomic orbital distributions to explain and understand the BZ photoluminescence properties (PL) at room temperature for the disordered structure based on structural deformation and symmetry changes. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 111: 694-701, 2011