Phoretic Motion of Spheroidal Particles Due To Self-Generated Solute Gradients

We study theoretically the phoretic motion of a spheroidal particle, which generates solute gradients in the surrounding unbounded solvent via chemical reactions active on its surface in a cap-like region centered at one of the poles of the particle. We derive, within the constraints of the mapping to classical diffusio-phoresis, an analytical expression for the phoretic velocity of such an object. This allows us to analyze in detail the dependence of the velocity on the aspect ratio of the polar and the equatorial diameters of the particle and on the fraction of the particle surface contributing to the chemical reaction. The particular cases of a sphere and of an approximation for a needle-like particle, which are the most common shapes employed in experimental realizations of such self-propelled objects, are obtained from the general solution in the limits that the aspect ratio approaches one or becomes very large, respectively.Comment: 18 pages, 5 figures, to appear in European Physical Journal

Toward a kinship perspective on entrepreneurship

This paper develops a theoretical framework for analyzing the role of kinship in entrepreneurship. Kinship, we argue, is a key-ingredient of the social and cultural environment of entrepreneurs, and therefore essential in understanding how and why entrepreneurship happens. Building on qualitative research conducted among Cambodian Chinese entrepreneurs in Phnom Penh, we define kinship as interpersonal ties grounded in relatedness. We distinguish different categories of kinship ties that involve different levels of relatedness and are used for different aspects of entrepreneurship, and we identify different types of reciprocity and trust as the sociocultural dynamics that buttress kinship involvement in entrepreneurship

Population planning and change in Singapore

10.1007/BF02331919Population and Environment163237-25