THERMAL POST-BUCKLING OF SLENDER ELASTIC RODS WITH DIFFERENT BOUNDARY CONDITIONS

This paper presents mathematical formulation, critical buckling temperature and analytical and numerical solutions for the thermal post-buckling behavior of slender rods subjected to uniform thermal load. The material is assumed to be linear elastic, homogeneous and isotropic. Furthermore, large displacements are considered hence the formulation is geometrically non-linear. Three different boundary conditions are assumed: (i) double-hinged non-movable, (ii) hinged non-movable at one end, whereas at the other end longitudinal displacement is constrained by a linear spring, and (iii) double-fixed non-movable. The governing equations are derived from geometrical compatibility, equilibrium of forces and moments, constitutive equations and strain-displacement relation, yielding a set of six first-order non-linear ordinary differential equations with boundary conditions specified at both ends, which constitutes a complex boundary value problem. The buckling and post-buckling solutions are respectively accomplished assuming infinitesimal and finite rotations. The results are presented in non-dimensional graphs for a range of temperature gradients and different values of slenderness ratios, and it is shown that this parameter governs the rod post-buckling response. The influence of the boundary conditions is evaluated through graphic results for deformed configuration, maximum deflection, maximum inclination angle and maximum curvature in the rod

Switching of +/-360deg domain wall states in a nanoring by an azimuthal Oersted field

We demonstrate magnetic switching between two $360^\circ$ domain wall vortex states in cobalt nanorings, which are candidate magnetic states for robust and low power MRAM devices. These $360^\circ$ domain wall (DW) or "twisted onion" states can have clockwise or counterclockwise circulation, the two states for data storage. Reliable switching between the states is necessary for any realistic device. We accomplish this switching by applying a circular Oersted field created by passing current through a metal atomic force microscope tip placed at the center of the ring. After initializing in an onion state, we rotate the DWs to one side of the ring by passing a current through the center, and can switch between the two twisted states by reversing the current, causing the DWs to split and meet again on the opposite side of the ring. A larger current will annihilate the DWs and create a perfect vortex state in the rings.Comment: 5 pages, 5 figure

Como implantar e conduzir uma horta de pequeno porte.

Esta publicação mostra passo a passo, de maneira simples, didática e prática, como produzir de forma sustentável hortaliças com a finalidade de subsistência em áreas de até 500 metros quadrados. Todas as recomendações são baseadas em trabalhos técnico-científicos e em casos de sucesso obtidos na região de Corumbá e Ladário, MS.bitstream/item/71563/1/CAR05.pdfCartilha

Revestimentos decorativos pelo efeito SPR obtido pela adição de Au a matrizes dieléctricas

A SPR (ressonância dos plasmões de superfície) originada pela introdução de nanopartículas metálicas em matrizes dieléctricas possui um elevado leque de aplicações, sendo alvo de uma actividade intensa de investigação. De modo a tirar partido da forte extinção da luz em certas gamas do visível que estes sistemas proporcionam, foi objectivo deste trabalho desenvolver revestimentos nanocompósitos com efeito SPR para aplicações decorativas. Para tal, recorreu-se à técnica de pulverização catódica reactiva para depositar os revestimentos nanocompósitos consistindo em nanopartículas de Au dispersas em matrizes de WO3 e Al2O3. Por outro lado, pela aplicação de tratamentos térmicos pós-deposição foi promovido o crescimento das nanopartículas de Au. A incorporação crescente de diferentes teores em Au na matriz permitiu a presença de nanopartículas com tamanhos maiores. Além disso, os tratamentos térmicos influenciaram com sucesso o crescimento das nanopartículas de Au na matriz, permitindo alterar a posição, forma e intensidade dos picos de SPR e, onsequentemente, a coloração obtida para as amostras. Contudo, também as propriedades estruturais e dieléctricas da matriz foram afectadas pela temperatura de recozimento, como por exemplo um aumento do índice de refracção que promoveu um deslocamento da posição dos picos de SPR para o “vermelho” (sistema W-O+Au). Nos resultados alcançados houve por isso um efeito combinado entre o crescimento das nanopartículas e a variação do índice de refracção da matriz. Através da variação de três parâmetros, matriz, composição química e temperatura de recozimento, foi possível depositar revestimentos nanocompósitos de WO3+Au e AlO+Au com diferentes cores pelo ajuste dos picos de SPR das nanopartículas de Au.The deposition of thin films consisting of metallic clusters embedded in dielectric matrixes can originate a strong SPR (Surface Plasmon Resonance) signal that has a wide range of applications, being the subject of an intense research nowadays. The main idea of this research work was to utilize the strong extinction of light that arises in these systems in certain zones of the visible spectrum for decorative coatings. Nanocomposite coatings consisting of Au clusters embedded in a WO3 or Al2O3 matrix were prepared by reactive sputtering with different Au contents. The higher the Au contents in the coatings the larger the nanoparticles were. By further annealing these samples at increasing temperatures, the Au segregation in the matrix was promoted. Both events permit to determine the SPR peak position along with its shape and intensity and, consequently, the optical properties of the coatings. Moreover, the thermal treatments also influenced the optical characteristics of the matrix, e.g. the refractive index was increased, leading to the redishing of the SPR position. Thus, the final results attained in the SPR peak shape, intensity and position for each case were mainly due to a combined effect between the Au cluster size and the refractive index of the oxide matrix. By varying the three major experimental parameters, the oxide matrix, the Au composition and the annealing temperature, it was possible to achieve nanocomposite coatings of WO3+Au and AlO+Au with different colours by tailoring the SPR peak shape and position.FCT - DECOMAT (PTDC/CTM/70037/2006), FEDER, através do programa COMPETE - Programa Operacional Factores de Competitividade

Field-dependent anisotropic magnetoresistance and planar Hall effect in epitaxial magnetite thin films

A systematic study of the temperature and magnetic field dependence of the longitudinal and transverse resistivities of epitaxial thin films of magnetite (Fe3O4) is reported. The anisotropic magnetoresistance (AMR) and the planar Hall effect (PHE) are sensitive to the in-plane orientation of current and magnetization with respect to crystal axes in a way consistent with the cubic symmetry of the system. We also show that the AMR exhibit sign reversal as a function of temperature, and that it shows significant field dependence without saturation up to 9 T. Our results provide a unified description of the anisotropic magnetoresistance effects in epitaxial magnetite films and illustrate the need for a full determination of the resistivity tensor in crystalline systems

Theory of magnetic domains in uniaxial thin films

For uniaxial easy axis films, properties of magnetic domains are usually described within the Kittel model, which assumes that domain walls are much thinner than the domains. In this work we present a simple model that includes a proper description of the magnetostatic energy of domains and domain walls and also takes into account the interaction between both surfaces of the film. Our model describes the behavior of domain and wall widths as a function of film thickness, and is especially well suited for the strong stripe phase. We prove the existence of a critical value of magneto-crystalline anisotropy above which stripe domains exist for any film thickness and justify our model by comparison with exact results. The model is in good agreement with experimental data for hcp cobalt.Comment: 15 pages, 7 figure

Pelidnota filippiniae Soula, 2009 (Coleoptera: Melolonthidae: Rutelinae): um novo desfolhador de acácia-australiana, Racosperma mangium (Willd.) Pedley (Fabaceae), na Amazônia Oriental, Brasil.

Plantios de acácia-australiana, Racosperma mangium (Willd.) Pedley (Fabaceae), são opção para reflorestamentos comerciais na Amazônia. O trabalho objetiva, pela primeira vez, reportar e descrever injúrias causadas por Pelidnota filippiniae Soula, 2009 (Coleoptera: Melolonthidae: Rutelinae) em plantio experimental em Dom Eliseu, Pará. Observações mensais foram feitas de 2006 a 2009. A maior incidência ocorreu no início do período chuvoso, em outubro e novembro, nos primeiros anos do plantio, quando diferentes intensidades de desfolha foram observadas. Embora danos significativos não tenham sido constatados, P. filippiniae tem potencial para causar prejuízos à cultura. Recomendam-se monitoramentos mensais nesse período e a catação manual do inseto para evitar maiores danos

Efficacy of dignity therapy for depression and anxiety in terminally-ill patients: early results of a randomized controlled trial

Objective: Dignity therapy (DT) is a short-term psychotherapy developed for patients living with a life-limiting illness. Our aim was to determine the influence of DT on symptoms of depression and anxiety in people with a life-threatening disease with high level of distress, referred to an inpatient palliative care unit. Method: This was an open-label randomized controlled trial. Sixty terminally ill patients were randomly assigned to one of two groups: intervention group (DT+ standard palliative care [SPC]) or control group (SPC alone). The main outcomes were symptoms of depression and anxiety, measured with the Hospital Anxiety and Depression Scale, assessed at baseline, day 4, day 15, and day 30 of follow-up. Results: Of the 60 participants, 29 were randomized to DT and 31 to SPC. Baseline characteristics were similar between the two groups. DT was associated with a significant decrease in depressive symptoms at day 4 and day 15 (mean = −4.46, 95% CI, −6.91–2.02, p = 0.001; mean= −3.96, 95% CI, −7.33 to −0.61; p = 0.022, respectively), but not at day 30 (mean = −3.33, 95% CI, −7.32–0.65, p = 0.097). DT was also associated with a significant decrease in anxiety symptoms at each follow-up (mean= −3.96, 95% CI, −6.66 to −1.25, p = 0.005; mean= −6.19, 95% CI, −10.49 to −1.88, p = 0.006; mean = −5.07, 95% CI, −10.22 to −0.09, p = 0.054, respectively). Significance of results: DT appears to have a short-term beneficial effect on the depression and anxiety symptoms that often accompany patients at the end of their lives. Future research with larger samples compared with other treatments is needed to better understand the potential benefits of this psychotherapy