Direct mineral tracer activation in positron emission particle tracking of a flotation cell

Understanding the complex interplay of physics and chemistry inside a flotation cell is the ultimate goal of most flotation research. Key to the development of a model of flotation is the ability to validate it from measurements of a real flotation system. This work uses positron emission particle tracking (PEPT) to track directly activated mineral particles, hydrophobic and hydrophilic, in a lab-scale flotation cell. In contrast to other particle activation methods the direct activation technique allows mineral particles with their original surface characteristics to be used in PEPT experiments. In this work the flotation separation investigated was the separation of hematite from quartz from a synthetic ore using a combination of an oleic acid collector and sodium silicate depressant. This work represents the first time in which particles of typical flotation size (−106 + 90 μm diameter) with real bulk mineral properties and surface chemistry have been tracked in a flotation cell. The results illustrate small particles flow behaviour in the cell for a hydrophilic particle. The trajectory and velocities of the tracer particle are shown as it is transported inside the flotation cell

γδ T-cell clones from intestinal intraepithelial lymphocytes inhibit development of CTL responses ex vivo

Oral administration of antigen induces a state of tolerance that is associated with activation of CD8(+) T cells that can transfer unresponsiveness to naïve syngeneic hosts. These T cells are not lytic, but they inhibit development of antibody, CD4(+) T helper cell, and CD8(+) cytotoxic T lymphocyte (CTL) responses upon adoptive transfer into naïve, syngeneic mice. In addition, we have shown that depletion of γδ T cells by injection of the anti-δ chain antibody (GL3) down modulates the expression of γδ T-cell receptor (TCR) and inhibits the induction of oral tolerance to ovalbumin. Oral administration of antigen also fails to induce tolerance in TCR δ-chain knockout mice suggesting that γδ T cells play a critical, active role in tolerance induced by orally administered antigen. To further study the contribution of γδ T cells to tolerance, murine γδ T cells were isolated from intraepithelial lymphocytes (IEL) of the small intestine by stimulation with splenic filler cells, concanavalin A and growth factors. γδ IEL lines demonstrated lytic activity in a redirected lysis assay. γδ T-cell clones express different γδ TCR genes and secrete large amounts of interleukin (IL)-10, but little or no IL-2, IL-4, or interferon-γ. γδ IEL clones expressed transforming growth factor-β1 and macrophage migration inhibitory factor, as well as IL-10, mRNA. Moreover, γδ T-cell clones potently inhibited the generation of CTL responses by secreted molecules rather than by direct cell-to-cell contact