Oil-in-oil emulsions stabilised solely by solid particles

A brief review of the stabilisation of emulsions of two immiscible oils is given. We then describe the use of fumed silica particles coated with either hydrocarbon or fluorocarbon groups in acting as sole stabilisers of emulsions of various vegetable oils with linear silicone oils (PDMS) of different viscosity. Transitional phase inversion of emulsions, containing equal volumes of the two oils, from silicone-invegetable (S/V) to vegetable-in-silicone (V/S) occurs upon increasing the hydrophobicity of the particles. Close to inversion, emulsions are stable to coalescence and gravity-induced separation for at least one year. Increasing the viscosity of the silicone oil enables stable S/V emulsions to be prepared even with relatively hydrophilic particles. Predictions of emulsion type from calculated contact angles of a silica particle at the oil–oil interface are in agreement with experiment provided a small polar contribution to the surface energy of the oils is included. We also show that stable multiple emulsions of V/S/V can be prepared in a two-step procedure using two particle types of different hydrophobicity. At fixed particle concentration, catastrophic phase inversion of emulsions from V/S to S/V can be effected by increasing the volume fraction of vegetable oil. Finally, in the case of sunflower oil + 20 cS PDMS, the study is extended to particles other than silica which differ in chemical type, particle size and particle shape. Consistent with the above findings, we find that only sufficiently hydrophobic particles (clay, zinc oxide, silicone, calcium carbonate) can act as efficient V/S emulsion stabilisers

Public and private provision of infrastructure and economic development.

This paper examines the role of infrastructure in long run economic growth. The paper consists of two sections, the first concentrates on the theoretical role of government spending in models of growth and the second details examples of private participation in infrastructure development. Using a simple endogenous growth model we find that while the hypothesized benefits of infrastructure expenditures may be large they require care in matching appropriate financing. As the development and maintenance of infrastructure will continue to be pivotal to the long term success of growing economies, we emphasize the lessons on financing and the caveats of private participation to those who are exploring innovative mechanisms for infrastructure design.

Slime mould imitation of Belgian transport networks: redundancy, bio-essential motorways, and dissolution

Belgium is amongst few artificial countries, established on purpose, when Dutch and French speaking parts were joined in a single unit. This makes Belgium a particularly interesting testbed for studying bio-inspired techniques for simulation and analysis of vehicular transport networks. We imitate growth and formation of a transport network between major urban areas in Belgium using the acellular slime mould Physarum polycephalum. We represent the urban areas with the sources of nutrients. The slime mould spans the sources of nutrients with a network of protoplasmic tubes. The protoplasmic tubes represent the motorways. In an experimental laboratory analysis we compare the motorway network approximated by P. polycephalum and the man-made motorway network of Belgium. We evaluate the efficiency of the slime mould network and the motorway network using proximity graphs

Understanding the U.S. Export Boom

U.S. exports grew at a rate of 8.2% per year from 1987-1994, far faster than the economy as a whole or even the manufacturing sector. This paper examines the source of this export boom and argues that the boom itself has been less remarkable for the rate of growth of exports than for the striking increase in export intensity. This increase in export intensity has occurred both in the aggregate and for individual plants across a wide range of industries. Competing explanations for the rise in exports are tested with a comprehensive plant level data set. Changes in exchange rates and rises in foreign income are the dominant sources for the export increase, while productivity increases in U.S. plants play a relatively small role. The results suggest that slower growth rates of U.S. trading partners and an appreciation of the dollar will have strong negative effects on the growth rate of U.S. manufacturing exports.

Who Dies? International Trade, Market Structure, and Industrial Restructuring

This paper examines the role of changing factor endowments in the growth and decline of industries and regions. The implications of an endowment-based Heckscher-Ohlin trade model for plant entry and exit are tested on 20 years of data for the entire US manufacturing sector. The trade model provides predictions for which industries will see growth through the positive net entry of plants. A multi-region version of the same model has predictions for which regions will see high turnover and net entry of plants. In a country such as the U.S. that is augmenting both its physical and human capital, the least capital-intensive, least skill-intensive industries are correctly predicted to have the lowest rate of net entry. In addition, increases in regional capital and skill intensity are associated with higher probabilities of shutdown, especially for plants in industries with low initial capital and skill intensities.

Dry oil powders and oil foams stabilised by fluorinated clay platelet particles

A series of platelet sericite particles coated to different extents with a fluorinating agent has been characterised and their behaviour in mixtures with air and oil studied. The material which forms by vigorous shaking depends on both the surface tension of the oil and the surface energy of the particles which control their degree of wetting. Oil dispersions are formed in liquids of relatively low tension (<22 mN m−1), e.g. hexane and cyclomethicone, for all particles. Particle-stabilised air-in-oil foams form in liquids of higher tension, e.g. dodecane and phenyl silicone, where the advancing three-phase contact angle θ, measured on a planar substrate composed of the particles into the liquid, lies between ca. 65° and 120°. For oils of tension above 27 mN m−1 like squalane and liquid paraffin with particles for which θ > 70°, we have discovered that dry oil powders in which oil drops stabilised by particles dispersed in air (oil-in-air) can be prepared by gentle mixing up to a critical oil : particle ratio (COPR) and do not leak oil. These powders, containing up to 80 wt% oil, release the encapsulated oil when sheared on a substrate. For many of the systems forming oil powders, stable liquid oil marbles can also be prepared. Above the COPR, catastrophic phase inversion occurs yielding an ultra-stable air-in-oil foam. We thus demonstrate the ability to disperse oil drops or air bubbles coated with particles within novel materials

Intermediaries in International Trade: direct versus indirect modes of export

This paper contributes to the relatively new literature on the role of intermediaries in international trade. Using Italian firm-level data, we document significant differences between exporters of different types and highlight the role of country-specific fixed cost in the choice of direct versus indirect modes of export. Recent theoretical work suggests that intermediaries are typically providing solutions to country-specific fixed costs. Our empirical results largely confirm this relationship. Measures of country fixed costs are positively associated with intermediary exports both in the aggregate and within firms. In contrast, proxies for variable trade costs are largely not correlated with differences between direct and indirect exports.heterogeneous firms, international trade, intermediation, wholesalers

Disaster resilience and children: managing food security in Zimbabwe's Binga District

The growing recognition of the vulnerability of children to disasters has added a new impetus to the concept of their involvement in disaster risk reduction programs. Involving children in disaster risk reduction is among those aspects promoted in the Hyogo Framework for Action 2005–2015 to enhance the resilience of disaster-affected communities. This article presents the results from a research study which investigated the involvement of children in disaster risk reduction programs in Binga District, Zimbabwe, focusing on food security. The results suggest that children are an invaluable part of human agency in disaster contexts, especially in view of increasing numbers of children orphaned by HIV and AIDS. Yet their involvement is still contested. Unless family and cultural pressures imposed on children are recognized and managed in disaster risk programming, the potential of children’s involvement is likely to be missed in building disaster-resilient communities

Intermediaries in international trade : Direct versus indirect modes of export

This paper contributes to the relatively new literature on the role of intermediaries in international trade. Using Italian firm-level data, we document significant differences between exporters of different types and highlight the role of country-specific fixed cost in the choice of direct versus indirect modes of export. Recent theoretical work suggests that intermediaries are typically providing solutions to country-specific fixed costs. Our empirical results largely confirm this relationship. Measures of country fixed costs are positively associated with intermediary exports both in the aggregate and within firms. In contrast, proxies for variable trade costs are largely not correlated with differences between direct and indirect exports.

A Note on the Empirical Implementation of the Lens Condition

Deardorff [Journal of International Economics 36 (1994) 167-175] offers an intuitively appealing test for factor price equality (FPE). He demonstrates that FPE is impossible if the set (i.e., lens) of points defined by regional factor abundance vectors does not lie within the set of points defined by goods' input intensities. This note demonstrates that empirical implementation of the lens condition is problematic if the "true" number of either goods or regions is unknown. We show that satisfaction of the lens condition is more likely when goods are relatively disaggregate compared to regions.