The Reducts of the Homogeneous Binary Branching C-relation

Let (L;C) be the (up to isomorphism unique) countable homogeneous structure carrying a binary branching C-relation. We study the reducts of (L;C), i.e., the structures with domain L that are first-order definable in (L;C). We show that up to existential interdefinability, there are finitely many such reducts. This implies that there are finitely many reducts up to first-order interdefinability, thus confirming a conjecture of Simon Thomas for the special case of (L;C). We also study the endomorphism monoids of such reducts and show that they fall into four categories.Comment: 39 pages, 4 figure

Sustained Release of Persulfate and Iron(II) Ions from Inert Inorganic Materials for Groundwater Remediation

Contamination of groundwater, initiated from years of human negligence, continues to persist despite major advancements in water remediation technologies. The generated groundwater plumes can continuously replenish contaminants such as dense nonaqueous phase liquids (DNAPLs) through the aid of slow-moving water. Thus, long-term treatment of this flow system has proven to be problematic. A selection of sophisticated sustained diffusion technologies is needed to help prevent further damage to this prominent freshwater source. Here, a novel in-situ chemical oxidation (ISCO) method was designed to incorporate persulfate into silica mediums such as zeolite, diatom, and silica flour for the treatment of groundwater contaminants at polluted sites. By controlling the release of a strong oxidant solely through inorganic materials, the oxidizing potential is preserved in contrast to being released through organic mediums. Several methods of making the pellets as well as different types of pellets with a range of release time for persulfate have been developed, offering a selection of both methods and pellets for the controlled release of persulfate. Inorganic sol-gel, consisting of primarily silicon dioxide, was used as an adhesive for added internal support for the pellets. A chlorinated DNAPL known as trichloroethylene (TCE) was selected for testing this method. The feasibility of controlling the release of ferrous sulfate as an activator for persulfate was also briefly investigated. Batch treatment of 15 mg L-1 of TCE solutions showed 73.0-99% degradation and a maximum persulfate release time of over 25 hours from persulfate-containing pellets. The purpose of this work is to show that these safe and inexpensive methods are potential prospects with further optimization and system scale-up for the continuous treatment of the groundwater in the near future

Risk preferences and development revisited

A

Optimal consumption policies in illiquid markets

We investigate optimal consumption policies in the liquidity risk model introduced in Pham and Tankov (2007). Our main result is to derive smoothness results for the value functions of the portfolio/consumption choice problem. As an important consequence, we can prove the existence of the optimal control (portfolio/consumption strategy) which we characterize both in feedback form in terms of the derivatives of the value functions and as the solution of a second-order ODE. Finally, numerical illustrations of the behavior of optimal consumption strategies between two trading dates are given.Illiquid market; optimal consumption; integrodifferential equations; viscosity solutions; semiconcavity; sub(super) differentials; optimal control

Making Sense of a Senseless War

A review of: A Dirty War in West Africa: The RUF and the Destruction of Sierra Leone by Lansana Gberie. Bloomington, IN: Indiana University Press, 2005. and Young Soldiers: Why They Choose to Fight by Rachel Brett and Irma Specht. Boulder, CO: Lynne Rienner Publishers, 2005

The Limits of Intervention—Humanitarian or Otherwise

A review of: The Dark Sides of Virtue: Reassessing International Humanitarianism by David Kennedy. Princeton: Princeton University Press, 2004. 400 pp. and At the Point of a Gun: Democratic Dreams and Armed Intervention by David Rieff. New York: Simon & Schuster, 2005. 288 pp

Legitimacy, Justice, and the Future of Africa

A review of: Human Rights, the Rule of Law, and Development in Africa edited by Paul Tiyambe Zeleza and Philip J. McConnaughay. Philadelphia: University of Pennsylvania Press, 2004. 308 pp