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Abstract Natural gas has been promoted as a ‘‘bridge’’ fuel toward a low-carbon future by offering near-term emissions reductions at lower cost. Existing literature is inconclusive on the short-term emissions benefits of more abundant natural gas. The long-lived nature of natural gas infrastructure also threatens to lock in emissions levels well above longer-term targets. If natural gas can offer short-to-medium term benefits, how much of a bridge should we build? Using ARTIMAS, a foresighted computable general equilibrium model of the US economy, we interact scenarios developed by the EMF-34 study group related to abundant natural gas, low-cost renewables, and a carbon tax to examine the role of natural gas in a carbon-constrained future. We find that abundant natural gas alone does not have a significant impact on CO2 emissions. We also find that, under a higher carbon tax, natural gas investment of approximately $10 billion per year declines to zero at a tax of about $40/ton and existing natural gas assets face significant risk of impairment. Last, the presence of abundant natural gas lowers the marginal welfare cost of abating small amounts of CO2 but is likely to raise the cost of abatement levels consistent with common climate objectives. The integrated welfare costs of climate policy depend on how much abatement we must undertake.

In this study, the effect of recycling the non-condensable gases (NCG) in the catalytic pyrolysis of hybrid poplar using FCC catalyst was investigated. A 50mm bench scale fluidized bed reactor at 475°C with a weight hourly space velocity (WHSV) of 2h(-1) and a gas recycling capability was used for the studies. Model fluidizing gas mixtures of CO/N(2), CO(2)/N(2), CO/CO(2)/N(2) and H(2)/N(2) were used to determine their independent effects. Recycling of the NCG in the process was found to potentially increase the liquid yield and decrease char/coke yield. The model fluidizing gases increased the liquid yield and the CO(2)/N(2) fluidizing gas had the lowest char/coke yield. The (13)C-NMR analysis showed that recycling of NCG increases the aromatic fractions and decreases the methoxy, carboxylic and sugar fractions. Recycling of NCG increased the higher heating value and the pH of the bio-oil as well as decreased the viscosity and density.

Numerous studies have examined relationships between primary production and biodiversity at higher trophic levels. However, altered production in plant communities is often tightly linked with concomitant shifts in diversity and composition, and most studies have not disentangled the direct effects of production on consumers. Furthermore, when studies do examine the effects of plant production on animals in terrestrial systems, they are primarily confined to a subset of taxonomic or functional groups instead of investigating the responses of the entire community. Using natural monocultures of the salt marsh cordgrass Spartina alterniflora, we were able to examine the impacts of increased plant production, independent of changes in plant composition and/or diversity, on the trophic structure, composition, and diversity of the entire arthropod community. If arthropod species richness increased with greater plant production, we predicted that it would be driven by: (1) an increase in the number of rare species, and/or (2) an increase in arthropod abundance. Our results largely supported our predictions: species richness of herbivores, detritivores, predators, and parasitoids increased monotonically with increasing levels of plant production, and the diversity of rare species also increased with plant production. However, rare species that accounted for this difference were predators, parasitoids, and detritivores, not herbivores. Herbivore species richness could be simply explained by the relationship between abundance and diversity. Using nonmetric multidimensional scaling (NMDS) and analysis of similarity (ANOSIM), we also found significant changes in arthropod species composition with increasing levels of production. Our findings have important implications in the intertidal salt marsh, where human activities have increased nitrogen runoff into the marsh, and demonstrate that such nitrogen inputs cascade to affect community structure, diversity, and abundance in higher trophic levels.

The detection of island formation in power networks is prerequisite for the study of security analysis and control. We develop a combined graph-theoretic-algebraic approach to detect island formation in power system networks under multiple line outages. We construct the approach by gaining insights into the topological impacts of outaged lines on system connectivity from the use of power transfer distribution factor information. We develop a one-to-one relationship between minimal cutsets and a matrix of the generalized line outage distribution factors for multiple line outages. This relationship requires computations on lower order matrices and so is able to provide rapidly essential information. The proposed approach detects the island formation and identifies the subset of outaged lines that is the causal factor. Furthermore, for cases in which the set of outaged lines does not result in system separation, the method has the ability to identify whether a set of candidate line outages separates the system. Consequently, the need for establishing nodal system connectivity is bypassed. We illustrate the capabilities of the proposed approach on two large-scale networks. The proposed approach provides an effective tool for both real-time and offline environments for security analysis and control

Anaerobic bio-digestion/energy generation complexes using animal waste raw materials represent an important component of renewable energy initiatives and policies worldwide, and are significant contributors to broaden sustainability efforts. In such projects bio-power feasibility depends heavily on generation complex access to biomass which is of costly transportation. As a result, an important component of renewable energy planning is the optimization of a logistics system to guarantee low-cost access to animal waste. This access is a function of local characteristics including number and geographic location of organic waste sources, operating and maintenance costs of the generation facility, energy prices, and marginal contribution of biomass collected and delivered to the anaerobic bio-digestion unit. Because biomass exhibits high transportation costs per unit of energy ultimately generated, and because different types of biomass have different biogas-generating properties, design of the supply logistics system can be the determinant factor towards economic viability of energy generation from an anaerobic bio-digestion plant. Indeed, to address this problem it is helpful to consider the farms, the logistics system, the anaerobic bio-digestion plant, and the generation plant as subsystems in an integrated system. Additionally, the existence of an outlet for manure may allow farmers to significantly raise boundaries of one constraint they face, namely disposing of animal waste, therefore permitting increases in farm production capacity. This paper suggests and outlines a systematic methodology to address the design of such systems.

Objective The current guidelines suggest alcohol septal ablation (ASA) is less effective in hypertrophic obstructive cardiomyopathy (HOCM) patients with severe left ventricular hypertrophy, despite acknowledging that systematic data are lacking. Therefore, we analysed patients in the Euro-ASA registry to test this statement. Methods We compared the short-term and long-term outcomes of patients with basal interventricular septum (IVS) thickness <30 mm Hg to those with ≥30 mm Hg treated using ASA in nine European centres. Results A total of 1519 patients (57±14 years, 49% women) with symptomatic HOCM were treated, including 67 (4.4%) patients with IVS thickness ≥30 mm. The occurrence of short-term major adverse events were similar in both groups. The mean follow-up was 5.4±4.3 years and 5.1±4.1 years, and the all-cause mortality rate was 2.57 and 2.94 deaths per 100 person-years of follow-up in the IVS <30 mm group and the IVS ≥30 mm group (p=0.047), respectively. There were no differences in dyspnoea (New York Heart Association class III/IV 12% vs 16%), residual left ventricular outflow tract gradient (16±20 vs 16±16 mm Hg) and repeated septal reduction procedures (12% vs 18%) in the IVS <30 mm group and IVS ≥30 mm group, respectively (p=NS for all). Conclusions The short-term results and the long-term relief of dyspnoea, residual left ventricular outflow obstruction and occurrence of repeated septal reduction procedures in patients with basal IVS ≥30 mm is similar to those with IVS <30mm. However, long-term all-cause and cardiac mortality rates are worse in the ≥30 mm group.

Abstract 1. 1. Excitation difference spectra techniques have been utilized to study energy transfer in enzymes. Definite evidence for tyrosine to tryptophan energy transfer is found in alcohol:NAD oxidoreductase (EC 1.1.1.1) and α-1,4-glucan-4-glucano-hydrolase ( Bacillus subtilus ) (EC 3.2.1.1), but not in α-chymotrypsin (EC 3.4.4.5), papain (EC 3.4.4.10), α-1,4-glucan-4-glucanohydrolase ( Aspergillus oryzae ) (EC 3.2.1.1), pepsin (EC 3.4.4.1), and carboxypeptidase A (EC 3.4.2.1). 2. 2. The phosphorescence excitation spectra provide direct experimental evidence that the enzyme emission in the region from 350 to 390 nm in due to tyrosine residues. Futhermore, these data suggest that the emitting tyrosine residues in the enzymes appear to be in an aqueous-like environment and therefore presumbly exposed to the solvent. 3. 3. Phosphorescence excitation difference spectra indicate that those tyrosine residues which are responsible for transferring energy to tryptophan residues are probably in a non-aqueous environment. 4. 4. Neither the relative tyrosine/tryptophan phosphrescence yields, nor the absolute yields in the enzymes could be simply correlated with the properties of the free amino acids.

Abstract Onshore wind power is cost competitive with conventional sources of electricity, but offshore wind power is more expensive, in part due to the added costs of offshore installation. Estimating the installation cost of future projects in the U.S. is an important component of capital cost and provides guidance on expected decommissioning expenditures. The purpose of this paper is to develop a model of the installation costs of offshore wind projects on the U.S. Outer Continental Shelf. Offshore wind farms are characterized in terms of four primary variables – nameplate capacity, turbine capacity, distance to port and distance to shore – which are employed in empirical models of installation. A bottom-up approach is used based on current technologies and expected market conditions for the period 2012–2017 to estimate stage-specific installation costs. The installation costs at three planned U.S. wind farms (Cape Wind, Bluewater Delaware, and Coastal Point Galveston) are estimated and range from $130,000 to $370,000 per MW. Sensitivity analyses are performed to identify the variables most responsible for uncertainty and risk. Cost is relatively insensitive to distance to port, but unit costs decline significantly with larger turbine capacity, and increase with the time required for installation. The limitations of the analysis are described.

Moss-associated N2 fixation by epiphytic microbes is a key biogeochemical process in nutrient-limited high-latitude ecosystems. Abiotic drivers, such as temperature and moisture, and the identity of host mosses are critical sources of variation in N2 fixation rates. An understanding of the potential interaction between these factors is essential for predicting N inputs as moss communities change with the climate. To further understand the drivers and results of N2 fixation rate variation, we obtained natural abundance values of C and N isotopes and an associated rate of N2 fixation with 15N2 gas incubations in 34 moss species collected in three regions across Alaska, USA. We hypothesized that δ15N values would increase toward 0‰ with higher N2 fixation to reflect the increasing contribution of fixed N2 in moss biomass. Second, we hypothesized that δ13C and N2 fixation would be positively related, as enriched δ13C signatures reflect abiotic conditions favorable to N2 fixation. We expected that the magnitude of these relationships would vary among types of host mosses, reflecting differences in anatomy and habitat. We found little support for our first hypothesis, with only a modest positive relationship between N2 fixation rates and δ15N in a structural equation model. We found a significant positive relationship between δ13C and N2 fixation only in Hypnales, where the probability of N2 fixation activity reached 95% when δ13C values exceeded - 30.4‰. We conclude that moisture and temperature interact strongly with host moss identity in determining the extent to which abiotic conditions impact associated N2 fixation rates.