The concentration of solute molecules at the surface of a liquid is a factor in heterogeneous reactions, surface tension, and Marangoni-effect-driven surface flows. Increasingly, X-ray photoelectron spectroscopy (XPS) has enabled surface concentrations to be measured. In prior work, we employed statistical mechanics to derive expressions for surface tension as a function of solute activity in a binary solution. Here we use a Gibbs relation to derive concomitant expressions for surface concentration. Surface tension data from the literature for five alcohols are used to identify parameters in the surface tension equation. These parameters are then used in the surface concentration equation to predict surface concentrations. Comparison of these predictions to those measured with XPS shows a factor of three difference between measured and predicted surface concentrations. Potential reasons for the discrepancy are discussed, including lack of surface-bulk equilibrium in the measurements.
Endoscopic biopsy forceps are the key to minimally invasive procedures to an endoscopic surgeon. These surgeons have to maneuver forceps with cutting performance through the body while maintaining minimal damage to the narrow channels during insertion. The amount of precision the user needs to successfully perform endoscopic surgery is high enough to create a preference amongst surgeons. Physicians are often not involved in the purchasing decision on the instruments, but they usually can provide their preference of instrument mainly based on the subjective perception of how an instrument feels or works in their hands. To base discussions between surgeons and purchasing departments on quantitative data of forceps use performance, this study aims to provide a performance testing method for different instruments such as different brands, designs, reusable or single-use, or instruments in different wear stages. Ultimately, this will allow to determine which instrument performs with the maximum efficiency at the lowest cost. First, findings in the literature on forceps failure, wear and testing are described. Then, the forceps design and handling during a biopsy are investigated. A preliminary test set-up is introduced for a repeatable biopsy test for endoscopic forceps. Different tissue types and samples can be used in the test stand to define an ideal acceleration profile for the forceps during biopsy and the cut can be analyzed by microscopy afterwards. A sensor on the operator’s wrist measures acceleration and jerk while pulling at the forceps, which will give new insight into the performance of different forceps types and forceps in different wear states, independent from forceps’ brand, design or wear states.
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