Relaxation and reconstruction on (111) surfaces of Au, Pt, and Cu

We have theoretically studied the stability and reconstruction of (111) surfaces of Au, Pt, and Cu. We have calculated the surface energy, surface stress, interatomic force constants, and other relevant quantities by ab initio electronic structure calculations using the density functional theory (DFT), in a slab geometry with periodic boundary conditions. We have estimated the stability towards a quasi-one-dimensional reconstruction by using the calculated quantities as parameters in a one-dimensional Frenkel-Kontorova model. On all surfaces we have found an intrinsic tensile stress. This stress is large enough on Au and Pt surfaces to lead to a reconstruction in which a denser surface layer is formed, in agreement with experiment. The experimentally observed differences between the dense reconstruction pattern on Au(111) and a sparse structure of stripes on Pt(111) are attributed to the details of the interaction potential between the first layer of atoms and the substrate.Comment: 8 pages, 3 figures, submitted to Physical Review

Using the past to constrain the future: how the palaeorecord can improve estimates of global warming

Climate sensitivity is defined as the change in global mean equilibrium temperature after a doubling of atmospheric CO2 concentration and provides a simple measure of global warming. An early estimate of climate sensitivity, 1.5-4.5{\deg}C, has changed little subsequently, including the latest assessment by the Intergovernmental Panel on Climate Change. The persistence of such large uncertainties in this simple measure casts doubt on our understanding of the mechanisms of climate change and our ability to predict the response of the climate system to future perturbations. This has motivated continued attempts to constrain the range with climate data, alone or in conjunction with models. The majority of studies use data from the instrumental period (post-1850) but recent work has made use of information about the large climate changes experienced in the geological past. In this review, we first outline approaches that estimate climate sensitivity using instrumental climate observations and then summarise attempts to use the record of climate change on geological timescales. We examine the limitations of these studies and suggest ways in which the power of the palaeoclimate record could be better used to reduce uncertainties in our predictions of climate sensitivity.Comment: The final, definitive version of this paper has been published in Progress in Physical Geography, 31(5), 2007 by SAGE Publications Ltd, All rights reserved. \c{opyright} 2007 Edwards, Crucifix and Harriso

Low-Cost Hydrogen Distributed Production System Development

H{sub 2}Gen, with the support of the Department of Energy, successfully designed, built and field-tested two steam methane reformers with 578 kg/day capacity, which has now become a standard commercial product serving customers in the specialty metals and PV manufacturing businesses. We demonstrated that this reformer/PSA system, when combined with compression, storage and dispensing (CSD) equipment could produce hydrogen that is already cost-competitive with gasoline per mile driven in a conventional (non-hybrid) vehicle. We further showed that mass producing this 578 kg/day system in quantities of just 100 units would reduce hydrogen cost per mile approximately 13% below the cost of untaxed gasoline per mile used in a hybrid electric vehicle. If mass produced in quantities of 500 units, hydrogen cost per mile in a FCEV would be 20% below the cost of untaxed gasoline in an HEV in the 2015-2020 time period using EIA fuel cost projections for natural gas and untaxed gasoline, and 45% below the cost of untaxed gasoline in a conventional car. This 20% to 45% reduction in fuel cost per mile would accrue even though hydrogen from this 578 kg/day system would cost approximately $4.14/kg, well above the DOE hydrogen cost targets of$2.50/kg by 2010 and $2.00/kg by 2015. We also estimated the cost of a larger, 1,500 kg/day SMR/PSA fueling system based on engineering cost scaling factors derived from the two H{sub 2}Gen products, a commercial 115 kg/day system and the 578 kg/day system developed under this DOE contract. This proposed system could support 200 to 250 cars per day, similar to a medium gasoline station. We estimate that the cost per mile from this larger 1,500 kg/day hydrogen fueling system would be 26$2.87/kg, still above the DOE's 2010 $2.50/kg target. We also began laboratory testing of reforming ethanol, which we showed is currently the least expensive approach to making renewable hydrogen. Extended testing of neat ethanol in micro-reactors was successful, and we also were able to reform E-85 acquired from a local fueling station for 2,700 hours, although some modifications were required to handle the 15% gasoline present in E-85. We began initial tests of a catalyst-coated wall reformer tube that showed some promise in reducing the propensity to coke with E-85. These coated-wall tests ran for 350 hours. Additional resources would be required to commercialize an ethanol reformer operating on E-85, but there is no market for such a product at this time, so this ethanol reformer project was moth-balled pending future government or industry support. The two main objectives of this project were: (1) to design, build and test a steam methane reformer and pressure swing adsorption system that, if scaled up and mass produced, could potentially meet the DOE 2015 cost and efficiency targets for on-site distributed hydrogen generation, and (2) to demonstrate the efficacy of a low-cost renewable hydrogen generation system based on reforming ethanol to hydrogen at the fueling station

Photocatalysis to promote cell-free biocatalytic reactions

Cofactors assist enzymes to catalyze reactions and are indispensable and ubiquitous in nature, playing a central role in metabolic pathways. In biocatalysis, common redox cofactors such as nicotinamide, flavin and heme can be activated by light or synthetized to vary redox potentials, leading to different types of reactions for the formation of interesting chiral products, unattainable through classical chemical methods. This chapter will focus on light-driven cell-free biocatalytic reactions activated via their redox cofactors.</p

Influence of increasing populations of Double-crested Cormorants on soil nutrient characteristics of nesting islands in western Lake Erie

Animals can influence the structure of an ecosystem by changing the levels of nutrient input. This is of particular importance for the islands of western Lake Erie, which are relatively nutrient poor, but have experienced increases in nutrient input from growing double-crested cormorant (Phalacrocorax auritus) populations. The objectives of this study were to evaluate changes in soil characteristics (nutrients [nitrate (NO 3), total P], pH, and δ 13C [as a tracer of cormorant-associated nutrients]) across a gradient of cormorant nest density on two islands (Middle and East Sister) in western Lake Erie. For both islands, soil pH decreased and P concentrations increased with nest density. On Middle Island, soil nitrate concentrations increased with cormorant nest density, and varied with breeding phen

Nesting cormorants and temporal changes in Island habitat

Double-crested cormorant (Phalacrocorax auritus) populations have increased greatly across North America. The interior North America subpopulation is the largest with many birds nesting on the Laurentian Great Lakes. Lake Erie supports a large number of breeding pairs tha