2,269 research outputs found
Anaerobic digestion of whole-crop winter wheat silage for renewable energy production
With biogas production expanding across Europe in response to renewable energy incentives, a wider variety of crops need to be considered as feedstock. Maize, the most commonly used crop at present, is not ideal in cooler, wetter regions, where higher energy yields per hectare might be achieved with other cereals. Winter wheat is a possible candidate because, under these conditions, it has a good biomass yield, can be ensiled, and can be used as a whole crop material. The results showed that, when harvested at the medium milk stage, the specific methane yield was 0.32 m3 CH4 kgâ1 volatile solids added, equal to 73% of the measured calorific value. Using crop yield values for the north of England, a net energy yield of 146â155 GJ haâ1 yearâ1 could be achieved after taking into account both direct and indirect energy consumption in cultivation, processing through anaerobic digestion, and spreading digestate back to the land. The process showed some limitations, however: the relatively low density of the substrate made it difficult to mix the digester, and there was a buildup of soluble chemical oxygen demand, which represented a loss in methane potential and may also have led to biofoaming. The high nitrogen content of the wheat initially caused problems, but these could be overcome by acclimatization. A combination of these factors is likely to limit the loading that can be applied to the digester when using winter wheat as a substrat
Pseudorapidity distributions of charged particles from Au+Au collisions at the maximum RHIC energy, Sqrt(s_NN) = 200 GeV
We present charged particle densities as a function of pseudorapidity and
collision centrality for the 197Au+197Au reaction at Sqrt{s_NN}=200 GeV. For
the 5% most central events we obtain dN_ch/deta(eta=0) = 625 +/- 55 and
N_ch(-4.7<= eta <= 4.7) = 4630+-370, i.e. 14% and 21% increases, respectively,
relative to Sqrt{s_NN}=130 GeV collisions. Charged-particle production per pair
of participant nucleons is found to increase from peripheral to central
collisions around mid-rapidity. These results constrain current models of
particle production at the highest RHIC energy.Comment: 4 pages, 5 figures; fixed fig. 5 caption; revised text and figures to
show corrected calculation of and ; final version accepted for
publicatio
Do national resources have to be centrally managed? Vested interests and institutional reform in Norwegian fisheries governance
Corporatism -with its privileged access, restricted participation and centralized
structures - has a long history in Norwegian fisheries governance. Co-management â
understood as a decentralized, bottom-up and more inclusive form of fisheries
governance - has not been considered a relevant alternative.. Why does corporatism
still prevail in a context where stakeholder status in fisheries governance globally â both
in principle and practice - has been awarded environmental organizations, municipal
authorities and even consumer advocacy groups? Why then have alternatives to the
corporatist system of centralized consultation and state governance never been seriously
considered in Norway, in spite of the growing emphasis on fish as a public resource and
fisheries management as human intervention in geographically confined and complex
ecosystems? We suggest that thismay have to do with the fundamental assumptions
behind Norwegian fisheries governance that since fish is a national resource, it must be
centrally managed. We argue that this is an assumption that may be contested
Adenosine Triphosphate (ATP) as a Metric of Microbial Biomass in Aquatic Systems: New Simplified Protocols, Laboratory Validation, and a Reflection on Data From the Literature
The use of adenosine triphosphate (ATP) as a universal biomass indicator is built on the premise that ATP concentration tracks biomass rather than the physiological condition of cells. However, reportedly high variability in ATP in response to environmental conditions is the main reason the method has not found widespread application. To test possible sources of this variability, we used the diatom Thalassiosira weissflogii as a model and manipulated its growth rate through nutrient limitation and through exposure to three different temperatures (15°C, 20°C, and 25°C). We simplified the ATP protocol with hotâwater or chemical extraction methods, modified a commercially available luciferinâluciferase assay, and employed singleâphoton counting in a scintillation counter, all of which increased sensitivity and throughput. Perâcell ATP levels remained relatively constant despite changes in growth rates by approximately 10âfold in the batch culture (i.e., nutrient limitation) experiments, and approximately 2âfold in response to temperature. The reâexamination of related literature values revealed that average cellular ATP levels differed little among taxonomic groups of aquatic microbes, even at the domain level, and correlated well with bulk properties such as elemental carbon or nitrogen. Fulfilling multiple cellular functions in addition to being the universal energy currency requires ATP to be maintained in a millimolar concentration range. Consequently, ATP relates directly to live cytoplasm volume, while elemental carbon and nitrogen are constrained by an indeterminate pool of detrital material and intracellular storage compounds. The ATPâbiomass indicator is sensitive, economical, and can be readily standardized among laboratories and across environments
Quark Gluon Plasma an Color Glass Condensate at RHIC? The perspective from the BRAHMS experiment
We review the main results obtained by the BRAHMS collaboration on the
properties of hot and dense hadronic and partonic matter produced in
ultrarelativistic heavy ion collisions at RHIC. A particular focus of this
paper is to discuss to what extent the results collected so far by BRAHMS, and
by the other three experiments at RHIC, can be taken as evidence for the
formation of a state of deconfined partonic matter, the so called
quark-gluon-plasma (QGP). We also discuss evidence for a possible precursor
state to the QGP, i.e. the proposed Color Glass Condensate.Comment: 32 pages, 18 figure
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