Formation of iron sulfide at faecal pellets and other microniches within suboxic surface sediment.

Faecal pellet deposition and bioturbation may lead to heterogeneously distributed particles of localized highly reactive organic matter (microniches) being present below the oxygen penetration depth. Where O2, NO3-, and Fe/Mn oxyhydroxides become depleted within these microniches or where they exist in zones of sulfate reduction, significant localized peaks in sulfide concentration can occur. These discrete zones of sulfide evolution can cause formation of iron sulfides that would not be predicted by analysis of the ‘bulk’ sediment. Using a reaction-transport model developed specifically for investigating spherical microniches, and incorporating 3D diffusion, we investigated how the rate constants of organic matter (OM) degradation, particle porosity and niche lifetime, affect dissolved sulfide and iron concentrations, and formation of iron sulfide at such niches. For all of the modelled scenarios the saturation index for iron sulfide is positive, indicating favourable conditions for FeS precipitation in all niches. Those simulations within the microniche lifetime range of 2.5 to 5 days gave comparable concentration ratios of sulfide to iron in solution within the niche to experimentally observed values. Our model results provide insight into the mechanisms of preservation of OM, including soft tissue, in the paleo record, by predicting the conditions that result in preferential deposition of precipitates at the edge of microniches. Decreases in porosity, shorter niche lifetimes and increases in OM degradation rate constants, all tend to increase the likelihood that FeS precipitation will preferentially occur at the edges of a niche, rather than uniformly throughout the niche volume

Starting Positions, Reform Speed, and Economic Outcomes in Transitioning Economies

At the end of the 1980s and beginning of the 1990s 26 countries in Eastern Europe, the former Soviet Union and Mongolia initiated market reform policies. During the 1980's the average annual growth in real GDP for these countries was about 2.9%, while for the period 1990-1997, the average growth rate was -5.7%. During the same period China was implementing a relatively slow and gradual policy of economic reform and their economy responded with very high real GDP growth. From these experiences it was commonly concluded that rapid economic reform led to (at least) a short-term economic decline and that the more gradual implementation of reforms is more appropriate for countries starting with a long legacy of central planning. However, the above statistics and analysis ignore some interesting variations among the 26 CEE/FSU/Mongolian economies. The reform experience within this sample varies considerably from the rapid implementation observed in Slovenia and Poland to the very slow reforms observed in Belarus and Ukraine. And the results have varied as well. Average real annual GDP growth (1990/1997) for Slovenia was 1.4%, for Poland 4.1% while for Belarus it was -6.1% and for Ukraine it was -13.1%. The World Bank has constructed indices of reform speed for these 26 transitioning economies and the relation between reform speed and economic growth rates, as shown in the above figure, is positive. The conclusion drawn is that these countries all started with unfavorable "starting positions", were about to suffer economic decline even with no change in economic policy, and those countries implementing more rapid market reforms suffered from less of a decline. One could point to the economic declines in Cuba and North Korea during this period as "control cases" of what would have happened if no economic reforms had been implemented.http://deepblue.lib.umich.edu/bitstream/2027.42/39664/3/wp280.pd

Transverse mode control and switching in gas laser arrays

Theoretical and experimental investigations of multiple transverse mode laser oscillation involving spatially varying gain and loss are carried out. The effect of gain and loss distribution on mode competition is analyzed. Numerical examples are given for a CO2 waveguide laser array. Experimental results of CO2 laser arrays are found to be consistent with the theory, and robust in-phase coupled mode array operation has been achieved

The Silicon Meta-shell X-ray Mirror Technology Development Roadmap for the Lynx Mission

This document presents a roadmap for advancing the silicon meta-shell optics (SMO). It describes an overall strategy and key technical elements to be developed to meet the four-fold Lynx requirements: (1) angular resolution, (2) effective area, (3) mass, and (4) production schedule and cost. It also describes the building and testing of an engineering unit whose successful completion will retire all risks, technical, logistical, schedule, and cost, associated with building and delivering a mirror assembly for the Lynx mission. All of this work, designed to advance this technology to TRL 6, will be completed by Preliminary Design Review (PDR) to ensure that the flight mirror assembly production process will be but a repetition of a set of well-defined and mature steps, leading to on-time and on-budget delivery of a mirror assembly for the Lynx mission

An Agent Based Simulation of Smart Metering Technology Adoption

Based on the classic behavioural theory “the Theory of Planned Behaviour”, we develop an agent-based model to simulate the diffusion of smart metering technology in the electricity market. We simulate the emergent adoption of smart metering technology under different management strategies and economic regulations. Our research results show that in terms of boosting the take-off of smart meters in the electricity market, choosing the initial users on a random and geographically dispersed basis and encouraging meter competition between energy suppliers can be two very effective strategies. We also observe an “S-curve” diffusion of smart metering technology and a “lock-in” effect in the model. The research results provide us with insights as to effective policies and strategies for the roll-out of smart metering technology in the electricity market

Band Gap Formation and Tunability in Stretchable Serpentine Interconnects

Serpentine interconnects are highly stretchable and frequently used in flexible electronic systems. In this work, we show that the undulating geometry of the serpentine interconnects will generate phononic band gaps to manipulate elastic wave propagation. The interesting effect of `bands-sticking-together' is observed. We further illustrate that the band structures of the serpentine interconnects can be tuned by applying pre-stretch deformation. The discovery offers a way to design stretchable and tunable phononic crystals by using metallic interconnects instead of the conventional design with soft rubbers and unfavorable damping.Comment: 12 pages, 8 figure