Comparison of the Spherical Averaged Pseudopotential Model with the Stabilized Jellium Model

We compare Kohn-Sham results (density, cohesive energy, size and effect of charging) of the Spherical Averaged Pseudopotential Model with the Stabilized Jellium Model for clusters of sodium and aluminum with less than 20 atoms. We find that the Stabilized Jellium Model, although conceptually and practically more simple, gives better results for the cohesive energy and the elastic stiffness. We use the Local Density Approximation as well as the Generalized Gradient Approximation to the exchange and correlation energies.Comment: 13 pages, latex, 8 figures, compressed postscript version available at http://www.fis.uc.pt/~vieir

Differential elastic electron scattering cross sections for CCl₄ by 1.5–100 eV energy electron impact

We report absolute elastic differential, integral and momentum transfer cross sections for electron interactions with CCl₄. The incident electron energy range is 1.5-100 eV, and the scattered electron angular range for the differential measurements varies from 15°-130°. The absolute scale of the differential cross section was set using the relative flow technique with helium as the reference species. Comparison with previous total cross sections shows good agreement. Atomic-like behaviour in this scattering system is shown here for the first time, and is further investigated by comparing the CCl₄ elastic cross sections to recent results on the halomethanes and atomic chlorine at higher impact energies [H. Kato, T. Asahina, H. Masui, M. Hoshino, H. Tanaka, H. Cho, O. Ingólfsson, F. Blanco, G. Garcia, S. J. Buckman, and M. J. Brunger, J. Chem. Phys. 132, 074309 (2010)].This work was conducted under the support of the Japanese Ministry of Education, Sport, Culture and Technology. H.K. acknowledges the Japan Society for the Promotion of Science (JSPS) for his fellowships as grants-in-aid for scientific research. S.J.B also acknowledges the JSPS Invitation Fellowship for Research in Japan

Electron transfer driven decomposition of adenine and selected analogs as probed by experimental and theoretical methods

We report on a combined experimental and theoretical study of electron transfer induced decomposition of adenine and a selection of analogue molecules in collisions with potassium atoms (K). Time-of-flight negative ion mass spectra have been obtained in a wide collision energy range (6–68 eV in the centre-of-mass frame), providing a comprehensive investigation of the fragmentation patterns of purine, adenine, 9-methyl adenine, 6-dimethyl adenine and 2-D adenine. Following our recent communication about selective hydrogen loss from the transient negative ions (TNI) produced in these collisions [T. Dunha et al. J. Chem. Phys. 148, 021101 (2018)], this work focuses on the production of smaller fragment anions. In the low-energy part of the present range, several dissociation channels that are accessible in free electron attachment experiments are absent from the present mass spectra, notably NH2 loss from adenine and 9-methyl adenine. This can be understood in terms of a relatively long transit time of the K+ cation in the vicinity of the TNI tending to enhance the likelihood of intramolecular electron transfer. In this case, the excess energy can be redistributed through the available degrees of freedom inhibiting fragmentation pathways. Ab initio theoretical calculations were performed for 9-methyl adenine (9-mAd) and adenine (Ad) in the presence of a potassium atom and provided a strong basis for the assignment the lowest unoccupied molecular orbitals accessed in the collision process

Avaliação de cultivares de soja no município de Querência-MT.

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Explorando...: a complexidade do corpo humano: guião didáctico para professores: 1º ciclo

O presente livro faz parte da Coleção “Ensino Experimental das Ciências”, um conjunto de textos concebidos para apoiar a formação de professores(as) com vista à generalização do ensino das Ciências no 1.º Ciclo do Ensino Básico (CEB). Trata-se de um livro de suporte à Educação em Ciências para os primeiros níveis de escolaridade desenvolvido tendo por base orientações recentes a nível nacional e internacional

Avaliação do Impacte do Programa de Formação em Ensino Experimental das Ciências: Um estudo de âmbito nacional: Relatório Final

O Programa de Formação em Ensino Experimental das Ciências para Professores do 1.º Ciclo do Ensino Básico (PFEEC), desenvolveu-se ao longo de quatro anos letivos, entre 2006 e 2010, envolvendo um plano de formação contínua, de âmbito nacional, e a produção e disponibilização de recursos didáticos para Formadores de Professores e para Professores do 1.º ciclo. O programa alicerçou-se no reconhecimento de que o Ensino Experimental das Ciências, nos primeiros anos de escolaridade, é fundamental para o desenvolvimento da literacia científica dos alunos e para o desenvolvimento de capacidades necessárias ao exercício de uma cidadania informada. Todos os materiais produzidos no âmbito deste Programa estão ao dispor de toda a comunidade educativa, na página da DGE, podendo ser utilizados na Formação de Professores bem como na prática letiva dos professores deste nível de ensino. O programa envolveu ainda a dotação financeira das escolas de 1.º ciclo participantes para o apetrechamento do equipamento laboratorial considerado imprescindível ao desenvolvimento do trabalho experimental neste nível de escolaridade. Participaram no Programa um total de 5141 professores formandos, 4245 escolas e 149 359 alunos. Tendo em conta o conhecimento científico-pedagógico proporcionado aos professores por este Programa, bem como o apetrechamento das escolas envolvidas e os recursos produzidos, considerou-se importante levar a efeito um estudo, que permitisse avaliar o seu impacte nas práticas docentes e nos resultados de aprendizagens dos alunos. O relatório final que agora se apresenta é o resultado desse estudo, o qual foi coordenado pela Professora Isabel Martins, a quem competiu constituir e dirigir a equipa de investigação. Nele se descreve o modo como o estudo de avaliação, conduzido a nível nacional, foi desenvolvido, bem como os resultados e conclusões alcançados

Survival of probiotic microbial strains in a cheese matrix during ripening: Simulation of rates of salt diffusion and microorganism survival

The growth and survival behaviours of Bifidobacterium lactis and Lactobacillus acidophilus in a semi-hard Gouda cheese at various axial locations during 9 wk of ripening at 13 °C were assessed using non-linear regression analysis. The final average salt levels ranged in 2–4%(w/w). Viable numbers of both probiotic strains underwent a slow decline during the first 3 wk followed by a sharper decrease towards the end of ripening; such decrease was more substantial for the outer than for the inner cheese portions. Salt transport was successfully described by Fick's second law of diffusion, and the cheese was considered as a finite slab for modelling purposes. Salt diffusivity remained constant with time and was estimated to be 0.2 cm2/day. Theoretical salt concentration profiles were in good agreement with experimental data. The mathematical models postulated and fitted to the microbial viability data encompassed both a linear relationship between specific death rate and salt concentration and a constant death rate, following a methodology of increasing model complexity. Decision on the better model was taken based on a F-test of the ratio of incremental sum of squares of residuals to sum of squares of residuals of the more complex model, and it was concluded that viability of the probiotic strains was better described by a first order process independent of local salt concentration. Prediction of profiles of viable numbers of B. lactis and L. acidophilus in cheese with respect to both ripening time and axial location for several overall salt concentrations is useful in attempts to predict potential viability by the time of consumption

Multilayered interface in Ti/Macor (R) machinable glass-ceramic joints

Macor® machinable glass-ceramic and commercially pure (cp.) titanium were joined by active metal brazing, using a 64Ag–34.5Cu–1.5Ti (wt.%) filler alloy. The influence of the brazing temperature and holding stage on the microstructure and hardness profile of the interface, as well as on the shear strength of the joint, were assessed. Brazing was performed in a high vacuum furnace at 850, 890 and 930°C for 10 and 30 min. The reaction between the braze alloy and both materials led to the formation of a multilayered interface. The interfacial microstructure was analysed in a scanning electronic microscope (SEM) and the composition of each reaction layer was investigated by energy dispersive X-ray scans (EDS). The interfacial hardness profile was determined by a series of microhardness tests on each reaction layer. The mechanical strength of the joint was assessed from shear tests conducted at room temperature. Brazing at 850°C with a 10 min holding stage produced stronger joints, with an average shear strength of more than 85% of the glass-ceramic bulk strength