C627

Gustaaf A. van der Hoeven, Energy efficient landscaping, Kansas State University, November 1982

C568

Gustaaf A. van der Hoeven, Landscaping the farmstead, Kansas State University, December 1983

Colloid-oil-water-interface interactions in the presence of multiple salts: charge regulation and dynamics

We theoretically and experimentally investigate colloid-oil-water-interface interactions of charged, sterically stabilized, poly(methyl-methacrylate) colloidal particles dispersed in a low-polar oil (dielectric constant $\epsilon=5-10$) that is in contact with an adjacent water phase. In this model system, the colloidal particles cannot penetrate the oil-water interface due to repulsive van der Waals forces with the interface whereas the multiple salts that are dissolved in the oil are free to partition into the water phase. The sign and magnitude of the Donnan potential and/or the particle charge is affected by these salt concentrations such that the effective interaction potential can be highly tuned. Both the equilibrium effective colloid-interface interactions and the ion dynamics are explored within a Poisson-Nernst-Planck theory, and compared to experimental observations.Comment: 13+2 pages, 5+3 figures; V2: small clarifications in the tex

Lost in the crowd?:An investigation into where microwork is conducted and classifying worker types

The global expansion of the platform economy raised questions about where and by whom different forms of platform work are performed in Europe. This study focuses on microworking – that is, where an anonymous ‘crowd’ completes piecemeal digital work. Specifically, we address two questions about microworking in the EU-27: Where is microworking performed? Who is performing it? Based on the geolocation of 5,239 workers active on six prominent microworking platforms, we identify variation in the relative prevalence of microworking across the EU. Furthermore, we build on existing research to provide a more granular understanding of different classes of microworkers, in terms of diversity and (income) dependency. Four distinct classes of microworkers emerge through statistical modelling of eight relevant diversity and dependency indicators: age, gender, education, citizenship, experience, hours per week, personal income earned, household income. We label these classes Explorers, Enthusiasts, Supplementers, and Dependents. The identification of these emergent classes and varied prevalence of microworking across the EU, suggest the importance of heterogeneity to both the future study and regulation of microwork.</p

Pricing in the hotel and catering sector

A model explaining gross margins in the hotel and catering sector is developed. A cost-mark-up model for the retail sector is used as a starting point. Although we have to reject the hypothesis of mark-up pricing in the hotel and catering sector, the model proves a useful instrument to discriminate between such influences as sales composition, costs and their various components, scale and demand conditions on price setting. Our empirical evidence stems from the Dutch hotel and catering sector (1977 through 1981)