Public-private partnerships for biosecurity: an opportunity for risk sharing

Private efforts to prevent and control biological pests and infectious diseases can be a public good, and so incentivising private biosecurity management actions is both desirable and problematic. Compensation contracts can encourage biosecurity efforts, provide support against the collapse of economic sectors, and create an insurance network. We conceptualise a novel biosecurity instrument relying on formal compensation private–public partnerships using contract theory. Our framework explains how the public sector can harness increased private biosecurity measures by making payments to agents which depend both on their performance and that of the other stakeholders. Doing so allows the government to spread the risk across signatory agents. The framework also improves our understanding of government involvement due to public effects of biosecurity, influenced by the private agents’ capacity to derive private benefit from their own efforts on monitoring and control. Lastly, these theoretical results provide a foundation for further study of contractual responsibility sharing for pest management

Why Metrics Matter: Evaluating Policy Choices for Reactive Nitrogen in the Chesapeake Bay Watershed

Despite major efforts, the reduction of reactive nitrogen (Nr) using traditional metrics and policy tools for the Chesapeake Bay has slowed in recent years. In this article, we apply the concept of the Nitrogen Cascade to the chemically dynamic nature and multiple sources of Nr to examine the temporal and spatial movement of different forms of Nr through multiple ecosystems and media. We also demonstrate the benefit of using more than the traditional mass fluxes to set criteria for action. The use of multiple metrics provides additional information about where the most effective intervention point might be. Utilizing damage costs or mortality metrics demonstrates that even though the mass fluxes to the atmosphere are lower than direct releases to terrestrial and aquatic ecosystems, total damage costs to <i>all</i> ecosystems and health are higher because of the cascade of Nr and the associated damages, and because they exact a higher human health cost. Abatement costs for reducing Nr releases into the air are also lower. These findings have major implications for the use of multiple metrics and the additional benefits of expanding the scope of concern beyond the Bay itself and support improved coordination between the Clean Air and Clean Water Acts while restoring the Chesapeake Bay

Fracture Mechanics of Composite Solid Rocket Propellant Grains: Material Testing

reserved4Following a detailed literature survey on the fracture-mechanics properties of solid rocket propellants, this paper reports on an innovative set of fracture tests performed on a composite solid propellant based on ammonium perchlorate hydroxyl-terminated polybutadiene. After a short summary on standard linear–viscoelastic mechanical characterization, results on both linear–elastic fracture-mechanics (characterized by the fracture toughness KIC) and nonlinear fracture-mechanics (characterized by GF) tests are reported. Test results for linear–elastic fracturemechanics simulations have been obtained using middle-tension specimens. A practical methodology to separate the amount of strain energy lost through viscous processes from other sources is given and provides an effective method to apply the toughness-test validity criteria of the American Society for Testing and Materials E399 norm to propellants and other thermoviscoelastic materials. Measurements to determine the linear fracture-mechanics properties of the propellant have been carried out applying the wedge-splitting test methodology. Master curves for the toughness, the critical crack-opening displacement, and the fracture energy have been generated to correlate test data. Results are coherent with Shapery’s theory of fracture for viscoelastic materials. Results can be used within finite element simulations to assess the safety and integrity of a solid-propellant rocket motor under various loads, such as thermal cycling and ignition, assuming stationary conditions.G. Tussiwand Sandri; V. E. Saouma; R. Terzenbach; L. T. De LucaTussiwand, Giuseppe; V. E., Saouma; R., Terzenbach; DE LUCA, Luig