A nonlinear elasticity phantom containing spherical inclusions

The strain image contrast of some in vivo breast lesions changes with increasing applied load. This change is attributed to differences in the nonlinear elastic properties of the constituent tissues suggesting some potential to help classify breast diseases by their nonlinear elastic properties. A phantom with inclusions and long-term stability is desired to serve as a test bed for nonlinear elasticity imaging method development, testing, etc. This study reports a phantom designed to investigate nonlinear elastic properties with ultrasound elastographic techniques. The phantom contains four spherical inclusions and was manufactured from a mixture of gelatin, agar and oil. The phantom background and each of the inclusions have distinct Young's modulus and nonlinear mechanical behavior. This phantom was subjected to large deformations (up to 20%) while scanning with ultrasound, and changes in strain image contrast and contrast-to-noise ratio between inclusion and background, as a function of applied deformation, were investigated. The changes in contrast over a large deformation range predicted by the finite element analysis (FEA) were consistent with those experimentally observed. Therefore, the paper reports a procedure for making phantoms with predictable nonlinear behavior, based on independent measurements of the constituent materials, and shows that the resulting strain images (e. g., strain contrast) agree with that predicted with nonlinear FEA.

Cadmium Uptake by Lettuce (Lactuca sativa L.) as Basis for Derivation of Risk Limits in Soils

The availability and uptake of Cd by lettuce (Lactuca sativa L.) in two common tropical soils (before and after liming) were studied in order to derive human health-based risk soil concentration. Cadmium concentrations ranging from 1 to 12 mg kg(-1) were added to samples from a clayey Oxisol and a sandy-loam Ultisol under glasshouse conditions. After incubation, a soil sample was taken from each pot, the concentration of Cd in the soil was determined, lettuce was grown during 36 d, and the edible parts were harvested and analyzed for Cd. A positive linear correlation was observed between total soil Cd and the Cd concentration in lettuce. The amount of Cd absorbed by lettuce grown in the Ultisol was about twice the amount absorbed in the Oxisol. Liming increased the soil pH and slightly reduced Cd availability and uptake. CaCl2 extraction was better than DTPA to reflect differences in binding strength of Cd between limed and unlimed soils. Risk Cd concentrations in the Ultisol were lower than in the Oxisol, reflecting the greater degree of uptake from the Ultisol. The derived risk Cd values were dependent on soil type and the exposure scenario.

Quatro Desenhos de Frank Lloyd Wright

O objetivo deste trabalho é discutir aspectos do processo de projeto e sua representação gráfica, num momento em que softwares de projeto 3D vem se tornando hegemônicos na prática do arquiteto e no ensino de arquitetura, em contraponto às práticas de desenho em prancheta. Os motivos e circunstâncias não são objeto do trabalho, cujo foco está numa prática de projeto e representação gráfica 2D, mas que tem muito a contribuir para o debate do quadro acima: os desenhos de projeto de Frank Lloyd Wright. Casos de estudo: quatro pranchas desenhadas por FLLW. É importante notar que, no vasto quadro da historiografia wrightiana, análises e interpretações originais, pioneiras, da arquitetura vem surgindo nas últimas décadas, mas ainda há poucos textos sobre desenhos e representação gráfica do arquiteto. Este constitui uma primeira aproximação do autor acerca de tema que oferece abrangente potencial. São exemplos em que, na relação imagem-objeto, a representação bidimensional constrói o projeto tridimensional. A arquitetura emerge como experimentação sem cair na especulação formal. Demonstram uma prática mais lenta, reflexiva e laboriosa do que a oferecida pelos software 3D atuais – mas onde cada traço, textura e grafismo implica um significado de espaço e materialidade.