Colloidal particle aggregation in three dimensions

Colloidal systems are of importance not only for everyday products, but also for the development of new advanced materials. In many applications, it is crucial to understand and control colloidal interaction. In this paper, we study colloidal particle aggregation of silica nanoparticles, where the data are given in a three-dimensional micrograph obtained by high-angle annular dark field scanning transmission electron microscopy tomography. We investigate whether dynamic models for particle aggregation, namely the diffusion limited cluster aggregation and the reaction limited cluster aggregation models, can be used to construct structures present in the scanning transmission electron microscopy data. We compare the experimentally obtained silica aggregate to the simulated postaggregated structures obtained by the dynamic models. In addition, we fit static Gibbs point process models, which are commonly used models for point patterns with interactions, to the silica data. We were able to simulate structures similar to the silica structures by using Gibbs point process models. By fitting Gibbs models to the simulated cluster aggregation patterns, we saw that a smaller probability of aggregation would be needed to construct structures similar to the observed silica particle structure.     

TEXTURE OF TABLE OLIVES AND PIMENTOS

Mechanical and chemical methods applied to quantifying the texture of table olives and pimientos are reviewed, and examples are given of studies on factors affecting the texture of these products (such as fruit maturity and processing) in which these methods have been used. The four instruments found applicable to olives are: Christel Texturometer, FFL Penetrometer, IG Texturometer and Kramer Shear Press (compression and shear/compression cells). The latter has also been used with pimientos. Advantages and disadvantages of each are discussed. Additional work is needed on correlating the mechanical tests with sensory evaluation. The chemical methods involve quantification of pectic substances and their degradation products.     

Joint Maneuvers

With half the students seeking a transfer degree to five-year design schools and the other half looking for basic vocational instruction to pursue careers in the construction industry, teaching at community and junior colleges presents a unique opportunity to combine design and construction issues in a single assignment. This article documents a class taught in the Architecture Department at Pasadena City College. Working in groups of three for an entire semester, students with different backgrounds and interests merged their skills to produce a single structure that was both conscientiously designed and properly constructed.