Shape Of Individual Particles Research Articles

Kinetic model for the chemical dissolution of multiparticle systems

A kinetic model is designed to interpret fraction reacted/time curves obtained from leaching multiparticle concentrates. The effect of individual particle shape on fraction reacted/time curves was determined by comparing data obtained from leaching a sphere and numerous irregular particles of malachite made by breaking up blocks of ore. All the leaching processes were carried out under the same experimental conditions. Finally, a kinetic model is presented which includes both size and shape of the particles. Experimental results show that fraction reacted/time curves are nearly the same for all particles with the same initial size/shape factor ratio. The importance of the solid's shape in interpreting heterogeneous kinetic data is clearly shown.

Shearing Strengths of Kaolinite, Illite, and Montmorillonite

During the years 1957-1970, over 400 S and R triaxial compression tests were performed using sedimented, slurried, or remolded specimens of kaolinite, illite, montmorillonite, prepared with several adsorbed cations and ranges in pore- water electrolyte concentration and pH, to study the relative effects of physicochemical variables on the shearing properties. The strengths were found to be controlled mainly by physical effects related to the size and shape of individual particles. Diffuse double-layer forces were never found to be significant for calcium clays. They were also insignificant for sodium kaolinite but were effective in reducing the strength of sodium illite, and caused major loss in strength for sodium montmorillonite by causing a great decrease in particle thickness thus leading to highly flexible particles of low physical strength. /ASCE/

The reactions of bacterial viruses with their host cells

In its early stages the study of a sector of nature may be divided into two branches. In one we inquire what an object under investigation is; we want to know its morphology and its relation to other more or less similar objects. In the other branch we study what the object does and how it came to be what it is. Thus in chemistry we have molecular structure on the one hand and kinetics of reaction on the other. In biology, anatomy and embryology may be taken as examples of the two points of view. As a science progresses certain relations between structure and function begin to emerge, and eventually the pursuit of these relations may become the major interest in the field. The study of viruses is a very young science indeed. In recent years much progress has been made toward a better understanding of those phases of the virus problem concerned with the infectious agent or virus particle (7). Improved methods of isolation, culture, concentration and assay have made purified preparations of many viruses available in relatively large quantities for physical and chemical characterization. Application of the ultracentrifuge and diffusion techniques gives indirect evidence of the mean sizes and shapes of virus particles in solution; the electron microscope has made possible direct observation of sizes and shapes of individual particles in the dry state (7, 8, 53, 56, 68, 69, 72) ; and x-ray diffraction has given clues to the atomic architecture of certain plant virus particles (11). It has turned out that this segment of biological material includes particles as small as 10 mu and as large as 200 mu in diameter. The morphologies of the viruses range from relatively large cell-like structures (vaccinia), some of them being tadpole-shaped (T2 bacteriophage), to simple rods (tobacco mosaic) and spheres (bushy stunt). On the other hand, the particles of any particular strain of virus exhibit a remarkable uniformity in size and structure.