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We describe a new device in which an accurately measured force is applied to individual adherent cells while the topography of the adhesion zone is simultaneously monitored. The force is applied via a flexible glass micropipette, attached by suction to the cell under study, and is calculated directly from the measured pipette deflection. Regions of close contact in the adhesion zone are observed using interference reflection microscopy. We have used the device to measure the force required to detach human red blood cells from hydrophobic and hydrophilic glass surfaces, and to detach Dictyostelium discoideum amoebae from a hydrophobic glass surface. The measured forces per unit length of contact perimeter are within an order of magnitude of the tensions required for membrane rupture.

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Before the development of performance-enhancing admixtures, flowable fill mixes bled off excess mix water to consolidate after placement. The presence of significant amounts of material finer than 0.075 mm in the aggregate impeded bleeding, and therefore, most specifying agencies limited the percentage allowed to less than ten. New performance-enhancing admixtures limit strength, prevent segregation, and enhance workability by entraining large percentages of stable air bubbles in flowable fill mixtures. Flowable fill mixtures containing these admixtures do not bleed and, therefore, could possibly use aggregates containing greater than 10% finer than 0.075 mm. It was determined that aggregate containing up to 21% finer than 0.075 mm could be used to produce a flowable fill mix meeting National Ready Mixed Concrete Association performance recommendations.

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