A Simple Method for Measuring Fine-to-Ultrafine Aerosols Using Bipolar Charge Equilibrium.

Low-cost methods for measuring airborne microparticles and nanoparticles (aerosols) have remained elusive despite the increasing concern of health impacts from ambient, urban, and indoor sources. While bipolar ion sources are common in smoke alarms, this work is the first to exploit the mean charge on an aerosol resulting from a bipolar charge equilibrium and establish experimentally its correlation to properties of the aerosol particle size distribution. The net current produced from this mean particle charge is demonstrated to be linearly proportional to the product of the mean particle diameter and total number concentration (i ∼ Nd̅) for two bipolar ion sources (85Kr and 241Am). This conclusion is supported by simple equations derived from well-established bipolar charging theory. The theory predicts that the mean charge on the aerosol particles reaches an equilibrium, which, importantly, is independent of the concentration of charging ions. Furthermore, in situ measurements of a roadside aerosol demonstrate that the sensing method yields results in good agreement (R2 = 0.979) with existing portable and laboratory-grade aerosol instruments. The simplicity, stability, and cost of the bipolar ion source overcome challenges of other portable sensors, increasing the feasibility of widespread sensor deployment to monitor ultrafine particle characteristics, which are relevant to lung deposition and by extension, human health

African Women\u27s Movements and Struggles over Land

Access to land and other property is crucial to the livelihoods of women across the African continent. Women need land for residence, to grow crops and raise livestock, and to operate businesses and to secure access to and control over property which can provide them with a degree of stability in otherwise precarious and uncertain times. This chapter reviews contemporary women’s struggles for land and property rights in Africa. Drawing from country-focused, regional, and continental analyses, it addresses collective efforts by women’s and land rights movements to increase women’s access to and control over property through policy advocacy, litigation, and education; discusses the barriers to gender-equitable land and property rights reforms; and suggests that women property claimants may be propelling a shift toward more gender equitable property norms and practices in many places. The chapter concludes that supportive public policies and social institutional changes are both necessary to ensure that women have access to and control over the property necessary to their livelihoods. It further highlights the need for more research on the property struggles of differently situated African women such as those without children, those living in informal settlements, and those who are queer or trans, as well as on the counter-mobilization against women’s property rights movements