435 research outputs found
Economic implications of open versus closed cycle cooling for new steam electric power plants : a national and regional survey
Originally published as the author's thesis (M.S.), M.I.T., Dept. of Civil Engineering, 1979.Current and anticipated thermal pollution regulations will prevent
many new steam electric power plants from operating with once-through
cooling. Alternative cooling systems acceptable from an environmental
view fail to operate with the same efficiencies, in terms of resources
consumed per Kwh of electricity produced, offered by once-through
cooling systems. As a consequence there are clear conflicts between
meeting environmental objectives and meeting minimum cost and minimum
resource consumption objectives. This report examines, at both the
regional and national level, the costs of satisfying environmental objec-
tives through the existing thermal pollution regulations.
This study forecasts the costs of operating those megawatts of
new generating capacity to be installed between the years 1975 and 2000
which will be required to install closed cycle cooling solely to
comply with thermal regulations. A regionally disaggregated approach
is used in the forecasts in order to preserve as much of the anticipated
inter-regional variation in future capacity growth rates and economic
trends as possible. The net costs of closed cycle cooling over once-
through cooling are based on comparisons of the costs of owning and
operating optimal closed and open-cycle cooling configurations in
separate regions, using computer codes to simulate joint power plant/
cooling system operation. The expected future costs of current thermal
pollution regulations are determined for the mutually exclusive -
collectively exhaustive eighteen Water Resources Council Regions within
the contiguous U.S., and are expressed in terms of additional dollar
expenditures, water losses and energy consumption. These costs are then
compared with the expected resource commitments associated with the
normal operation of the steam electric power industry. It is found that
while energy losses appear to be small, the dollar costs could threaten
the profitability of those utility systems which have historically used
once-through cooling extensively throughout their system. In addition
the additional water demands of closed cycle cooling are likely to disrupt
the water supplies in those coastal areas having few untapped freshwater
supplies available
Testing an hypothesis of hybrid zone movement for toads in France
Hybrid zone movement may result in substantial unidirectional introgression of selectively neutral material from the local to the advancing species, leaving a genetic footprint. This genetic footprint is represented by a trail of asymmetric tails and displaced cline centres in the wake of the moving hybrid zone. A peak of admixture linkage disequilibrium is predicted to exist ahead of the centre of the moving hybrid zone. We test these predictions of the movement hypothesis in a hybrid zone between common (Bufo bufo) and spined toads (B. spinosus), using 31 nuclear and one mtDNA SNPs along a transect in the northwest of France. Average effective selection in Bufo hybrids is low and clines vary in shape and centre. A weak pattern of asymmetric introgression is inferred from cline discordance of seven nuclear markers. The dominant direction of gene flow is from B. spinosus to B. bufo and is in support of southward movement of the hybrid zone. Conversely, a peak of admixture linkage disequilibrium north of the hybrid zone suggests northward movement. These contrasting results can be explained by reproductive isolation of the B. spinosus and B. bufo gene pools at the southern (B. spinosus) side of the hybrid zone. The joint occurrence of asymmetric introgression and admixture linkage disequilibrium can also be explained by the combination of low dispersal and random genetic drift due to low effective population sizes
Plant-derived recombinant F1, V, and F1-V fusion antigens of Yersinia pestis activate human cells of the innate and adaptive immune system
Plague is still endemic in different regions of the world. Current vaccines raise concern for their side effects and limited protection, highlighting the need for an efficacious and rapidly producible vaccine. F1 and V antigens of Yersinia pestis, and F1-V fusion protein produced in Nicotiana benthamiana administered to guinea pigs resulted in immunity and protection against an aerosol challenge of virulent h pestis. We examined the effects of plant-derived F1, V, and F1-V on human cells of the innate immunity. F1, V, and F1-V proteins engaged TLR2 signalling and activated IL-6 and CXCL-8 production by monocytes, without affecting the expression of TNF-alpha, IL-12, IL-10, IL-1 beta, and CXCL10. Native F1 antigen and recombinant plant-derived F1 (rF1) and rF1-V all induced similar specific T-cell responses, as shown by their recognition by T-cells from subjects who recovered from E pestis infection. Native F1 and rF1 were equally well recognized by serum antibodies of Y. pestis-primed donors, whereas serological reactivity to rF1-V hybrid was lower, and that to rV was virtually absent. In conclusion, plant-derived F1, V, and F1-V antigens are weakly reactogenic for human monocytes and elicit cell-mediated and humoral responses similar to those raised by Y pestis infection
High genetic diversity of common toad (Bufo bufo) populations under strong natural fragmentation on a Northern archipelago
The last decades have shown a surge in studies focusing on the interplay
between fragmented habitats, genetic variation, and conservation. In the present
study, we consider the case of a temperate pond-breeding anuran (the common
toad Bufo bufo) inhabiting a naturally strongly fragmented habitat at the
Northern fringe of the species’ range: islands offshore the Norwegian coast. A
total of 475 individuals from 19 populations (three mainland populations and
16 populations on seven adjacent islands) were genetically characterized using
nine microsatellite markers. As expected for a highly fragmented habitat, genetic
distances between populations were high (pairwise Fst values ranging between
0.06 and 0.33), with however little differences between populations separated by
ocean and populations separated by terrestrial habitat (mainland and on
islands). Despite a distinct cline in genetic variation from mainland populations
to peripheral islands, the study populations were characterized by overall high
genetic variation, in line with effective population sizes derived from
single-sample estimators which were on average about 20 individuals. Taken
together, our results reinforce the notion that spatial and temporal scales of
fragmentation need to be considered when studying the interplay between
landscape fragmentation and genetic erosion
Novel syntrophic populations dominate an ammonia-tolerant methanogenic microbiome
Biogas reactors operating with protein-rich substrates have high methane potential and industrial value; however, they are highly susceptible to process failure because of the accumulation of ammonia. High ammonia levels cause a decline in acetate-utilizing methanogens and instead promote the conversion of acetate via a two-step mechanism involving syntrophic acetate oxidation (SAO) to H2 and CO2, followed by hydrogenotrophic methanogenesis. Despite the key role of syntrophic acetate-oxidizing bacteria (SAOB), only a few culturable representatives have been characterized. Here we show that the microbiome of a commercial, ammonia-tolerant biogas reactor harbors a deeply branched, uncultured phylotype (unFirm_1) accounting for approximately 5% of the 16S rRNA gene inventory and sharing 88% 16S rRNA gene identity with its closest characterized relative. Reconstructed genome and quantitative metaproteomic analyses imply unFirm_1’s metabolic dominance and SAO capabilities, whereby the key enzymes required for acetate oxidation are among the most highly detected in the reactor microbiome. While culturable SAOB were identified in genomic analyses of the reactor, their limited proteomic representation suggests that unFirm_1 plays an important role in channeling acetate toward methane. Notably, unFirm_1-like populations were found in other high-ammonia biogas installations, conjecturing a broader importance for this novel clade of SAOB in anaerobic fermentations
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