Single-domain versus two-domain configuration in thin ferromagnetic prisms

Thin ferromagnetic elements in the form of rectangular prisms are theoretically investigated in order to study the transition from single-domain to two-domain state, with changing the in-plane aspect ratio p. We address two main questions: first, how general is the transition; second, how the critical value p_c depends on the physical parameters. We use two complementary methods: discrete-lattice calculations and a micromagnetic continuum approach. Ultrathin films do not appear to split in two domains. Instead, thicker films may undergo the above transition. We have used the continuum approach to analyze recent Magnetic Force Microscopy observations in 30 nm-thick patterned Permalloy elements, finding a good agreement for p_c.Comment: 22 pages, 5 figure

Dipolar ground state of planar spins on triangular lattices

An infinite triangular lattice of classical dipolar spins is usually considered to have a ferromagnetic ground state. We examine the validity of this statement for finite lattices and in the limit of large lattices. We find that the ground state of rectangular arrays is strongly dependent on size and aspect ratio. Three results emerge that are significant for understanding the ground state properties: i) formation of domain walls is energetically favored for aspect ratios below a critical valu e; ii) the vortex state is always energetically favored in the thermodynamic limit of an infinite number of spins, but nevertheless such a configuration may not be observed even in very large lattices if the aspect ratio is large; iii) finite range approximations to actual dipole sums may not provide the correct ground sta te configuration because the ferromagnetic state is linearly unstable and the domain wall energy is negative for any finite range cutoff.Comment: Several short parts have been rewritten. Accepted for publication as a Rapid Communication in Phys. Rev.

The authors' reply

We appreciate Dr West's comments on our paper1; he has given us the opportunity to clarify some points that seem unresolved

Multivessel revascularisation in ST-elevation myocardial infarction: Too early to change the guidelines

Multivessel revascularisation in ST-elevation myocardial infarction: too early to change the guideline

Análise comparativa de lajes utilizando softwares de cálculo estrutural e a tecnologia BIM

In the field of civil engineering, the diversity of materials available on the market is growing every day, along with constant changes in technologies, it is up to the structural engineer to analyze the structure, the construction system, the technology used and the most suitable materials. This work comtemplate the study of the behavior of solid slabs, slabs latticed in one direction and ribbed slabs, using structural calculation programs Eberick and TQS, and an architectural reference model in IFC file to carry out the study on the platform BIM. With the ultimate goal of analyzing the characteristics, structural behaviors, performance and material consumption of each construction system, as well as analyzing and comparing the results obtained in the two programs and the positive and negative aspects of carrying out a structural project with the architecture in IFC file. Initially, the basic concepts necessary for carrying out a structural design in reinforced concrete are presented, the construction systems adopted, the calculation models used, the normative concepts, the computer programs, the design criteria and the pre-dimensioning of the elements. Then, structural models were launched with three types of slabs in Eberick and TQS, incompatibilities were corrected and structures were processed. After processing, a comparative analysis of the distribution of vertical loads, maximum loads on foundations, arrows, vibrations and material consumption was performed. After the analysis, it was concluded that the lattice slabs generated smaller vertical loads and less loads on the foundations, when compared to the other models. In relation to the arrows, the lattice slab with EPS filling was the one that presented the greatest vertical displacements, followed by the ribbed slabs and finally by the solid slabs. It was also observed that the solid slabs showed better behavior in relation to the limit state of vibrations. In the consumption of materials, the most economical slab was the model that contained lattice slabs, followed by ribbed slabs and then solid slabs. When comparing the software, a higher percentage of steel loading and consumption was observed in the Eberick software when compared to the TQS. Finally, the positive aspects of developing the project on the BIM platform were reported, which allowed an immediate visualization of the structure inserted in the architecture, thus allowing the incompatibilities to be more noticeable and for integrated projects to be generated.Trabalho de Conclusão de Curso (Graduação)Na área da engenharia civil, vem crescendo a cada dia a diversidade de materiais disponíveis no mercado juntamente as mudanças constantes nas tecnologias, compete ao engenheiro estrutural analisar a estrutura, o sistema construtivo, a tecnologia utilizada e os materiais mais adequados. Neste trabalho aborda-se o estudo do comportamento de lajes maciças, lajes treliçadas em uma direção e lajes nervuradas, utilizando-se dos softwares de cálculo estrutural Eberick e TQS, e de um modelo arquitetônico de referência em arquivo IFC para realizar o estudo na plataforma BIM. Com o objetivo final de analisar as características, os comportamentos estruturais, o desempenho e o consumo de material de cada sistema construtivo, assim como analisar e comparar os resultados obtidos nos dois programas e os aspectos positivos e negativos de se realizar um projeto estrutural com a arquitetura em arquivo IFC. Inicialmente apresentam-se os conceitos básicos necessários para a realização de um projeto estrutural em concreto armado, os sistemas construtivos adotados, os modelos de cálculos utilizados, os conceitos normativos, os programas computacionais, os critérios de projetos e o pré-dimensionamento dos elementos. Em seguida realizou-se o lançamento estrutural dos modelos com três tipos de lajes no Eberick e no TQS, foram corrigidas as incompatibilidades e processou-se as estruturas. Após o processamento, realizou-se a análise comparativa de distribuição de cargas verticais, cargas máximas nas fundações, flechas, vibrações e consumo de materiais. Feita a análise concluiu-se que as lajes treliçadas geraram carregamentos verticais menores e menos cargas nas fundações, quando comparada aos outros modelos. Em relação as flechas, a laje treliçada com enchimento em EPS foi a que apresentou maiores deslocamentos verticais, seguido das lajes nervuradas e por últimos das lajes maciças. Observou-se também que as lajes maciças apresentaram melhor comportamento em relação ao estado-limite de vibrações. No consumo de materiais, a laje mais econômica foi o modelo que continha lajes treliçadas, seguido das lajes nervuradas e depois das lajes maciças. No comparativo entre os softwares observou-se um percentual maior de carregamentos e consumo de aço no software Eberick quando comparado com o TQS. E por fim, foi relatado os aspectos positivos de se desenvolver o projeto na plataforma BIM, que permitiu uma visualização imediata da estrutura inserida na arquitetura, permitindo desse modo que as incompatibilidades fossem mais perceptíveis e que fossem gerados projetos integrados

A Numerical Framework For Nonlinear Peridynamics On Two-dimensional Manifolds Based On Implicit P-(Ec)k Schemes

In this manuscript, an original numerical procedure for the nonlinear peridynamics on arbitrarily--shaped two-dimensional (2D) closed manifolds is proposed. When dealing with non parameterized 2D manifolds at the discrete scale, the problem of computing geodesic distances between two non-adjacent points arise. Here, a routing procedure is implemented for computing geodesic distances by re-interpreting the triangular computational mesh as a non-oriented graph; thus returning a suitable and general method. Moreover, the time integration of the peridynamics equation is demanded to a P-(EC)$^k$ formulation of the implicit $\beta$-Newmark scheme. The convergence of the overall proposed procedure is questioned and rigorously proved. Its abilities and limitations are analyzed by simulating the evolution of a two-dimensional sphere. The performed numerical investigations are mainly motivated by the issues related to the insurgence of singularities in the evolution problem. The obtained results return an interesting picture of the role played by the nonlocal character of the integrodifferential equation in the intricate processes leading to the spontaneous formation of singularities in real materials

Application of a new photocatalytic nanomaterial obtained by Pulse Laser Ablation for Polychrome Paintings Conservation: a feasibility study

This works aims to present a preliminary study about the application on painting of TiO2 nanoparticles for self-cleaning and protective purposes. We firstly assessed the photocatalytic activity of the TiO2 nanoparticles, obtained by Pulsed Laser Ablation, by the discoloration of dye. After, the colloidal dispersion is applied to painting samples prepared in laboratory, according to old recipes and using the most-used historical binders and pigments, in order to verify the cleaning efficiency by discoloration of the chromatic markers. The spectrophotometric analysis is performed studying the Spectral Reflectance Factor trend and the color coordinates