Insights from the Field: Forests for Water

This issue brief describes analyses by the World Resources Institute (WRI) in support of emerging payments for watershed services (PWS) programs in two major watersheds in Maine and North Carolina and insights gleaned from work in progress. The three pilot initiatives discussed represent different approaches to establishing PWS programs that protect forests and other green infrastructure elements. In the Neuse River Basin in North Carolina, WRI is working with partners to identify beneficiaries and their water-related dependencies. We learned that clear documentation of the risks that beneficiaries face from water pollution, drought, and watershed degradation will help jump-start their participation in emerging PWS programs. In the Sebago Lake Watershed in Maine, WRI is finalizing a methodology for "green-gray" analysis that will provide beneficiaries a way to identify cost-effective green infrastructure solutions to water infrastructure demands of the 21 st century. Green infrastructure comprises all natural, seminatural and artificial networks of multifunctional ecological systems within, around, and between urban areas at all spatial scales. We learned that, to convince public investment managers to invest in green rather than gray, it is important to make the financial and business case using the same basic methodologies that are used for calculating the costs and benefits of conventional gray approaches. WRI is also working to develop PWS programs that help the city of Raleigh meet streetscape, conservation development, tree conservation, storm water management, and water quality goals contained in its Unified Development Ordinance in a least cost manner. We learned that market-based solutions like PWS can play a large role in land-use planning processes and that these processes may represent a large untapped demand driver for PWS programs throughout the Sout

Climate Change and Conflict: the Darfur Conflict and Syrian Civil War

As the impacts of climate change grow more apparent, policy makers and scholars have become increasingly interested in the relationship between climate change and conflict, but their analyses have shown ambiguous results. In this thesis, I analyze this relationship in two cases: the Sudan Darfur Conflict (2003-present) and the Syrian Civil War (2011-present). I argue that climate change functioned as an intermediate variable in each case, influencing other factors known to have contributed to the conflict. I find that climate change would have been unlikely to cause either conflict in isolation. Rather, climate change exacerbated the conflicts by making the factors that led to them more severe

van der Waals dispersion power laws for cleavage, exfoliation and stretching in multi-scale, layered systems

Layered and nanotubular systems that are metallic or graphitic are known to exhibit unusual dispersive van der Waals (vdW) power laws under some circumstances. In this letter we investigate the vdW power laws of bulk and finite layered systems and their interactions with other layered systems and atoms in the electromagnetically non-retarded case. The investigation reveals substantial difference between `cleavage' and `exfoliation' of graphite and metals where cleavage obeys a $C_2 D^{-2}$ vdW power law while exfoliation obeys a $C_3 \log(D/D_0) D^{-3}$ law for graphitics and a $C_{5/2} D^{-5/2}$ law for layered metals. This leads to questions of relevance in the interpretation of experimental results for these systems which have previously assumed more trival differences. Furthermore we gather further insight into the effect of scale on the vdW power laws of systems that simultaneously exhibit macroscopic and nanoscopic dimensions. We show that, for metallic and graphitic layered systems, the known "unusual" power laws can be reduced to standard or near standard power laws when the effective scale of one or more dimension is changed. This allows better identification of the systems for which the commonly employed `sum of $C_6 D^{-6}$' type vdW methods might be valid such as layered bulk to layered bulk and layered bulk to atom

An assessment of the corrosion resistance of powder sprayed titanium coatings

Aluminium and stainless steels are susceptible to pitting corrosion in sea water. Mild steel is susceptible to corrosion in general. Titanium however, has good corrosion resistance in chloride solutions and thus is not susceptible to pitting in sea water. The following is an assessment of the corrosion resistance of Titanium powder coatings. Potentiostatic electrochemical experiments were carried out on three substrates (stainless steel, mild steel and Aluminium) coated using two spray methods (plasma and HVOF). A discussion of the results was given with reference to the polarisation curves that were created, SEM images, XRD results, estimates of porosity, and Pourbaix diagrams. It was concluded that the plasma coating provides the best corrosion resistance due to the fact that it had less porosity than HVOF and that it is made up of Titanium oxides. Also, the corrosion mechanism for the coatings is pitting of the substrates at the end of pores. The extent of this is far greater for the HVOF than the plasma coating. It was found that features found in the polarisation curves for the substrates are present in the curves for coatings. This is more evident in the HVOF polarisation curves. Mild steel benefited the most from the Titanium coatings compared to the substrate (more so for the plasma coating). Finally, the plasma coating improves the substrate based on corrosion rate and thermodynamics, except for Aluminium which remains the same thermodynamically

Thermal and Chemical Evolution of Collapsing Filaments

Intergalactic filaments form the foundation of the cosmic web that connect galaxies together, and provide an important reservoir of gas for galaxy growth and accretion. Here we present very high resolution two-dimensional simulations of the thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from hydrogen, oxygen, and carbon. We study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity. In low-redshift, $Z \approx 0.1 Z_\odot$ filaments, the evolution is determined completely by the initial cooling time. If this is sufficiently short, the center of the filament always collapses to form dense, cold core containing a substantial fraction of molecules. In high-redshift, $Z=10^{-3} Z_\odot$ filaments, the collapse proceeds much more slowly. This is due mostly to the lower initial temperatures, which leads to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient. Finally, we study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby starbusting dwarf galaxy thought to be fueled by the accretion of filament gas. In contrast to our fiducial case, a substantial density peak forms at the center of the potential. This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occur. We find that we achieve similar accretion rates as NGC 5253 but our two-dimensional simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.Comment: 17 pages, 9 figures. ApJ in pres