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 kg–1 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 146–155 GJ ha–1 year–1 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

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

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 – 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 – 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

Nuclear Stopping in Au+Au Collisions at sqrt(sNN) = 200 GeV

Transverse momentum spectra and rapidity densities, dN/dy, of protons, anti-protons, and net--protons (p-pbar) from central (0-5%) Au+Au collisions at sqrt(sNN) = 200 GeV were measured with the BRAHMS experiment within the rapidity range 0 < y < 3. The proton and anti-proton dN/dy decrease from mid-rapidity to y=3. The net-proton yield is roughly constant for y<1 at dN/dy~7, and increases to dN/dy~12 at y~3. The data show that collisions at this energy exhibit a high degree of transparency and that the linear scaling of rapidity loss with rapidity observed at lower energies is broken. The energy loss per participant nucleon is estimated to be 73 +- 6 GeV.Comment: 5 pages, 4 figure

Effective gauge field theory of the t-J model in the charge-spin separated state and its transport properties

We study the slave-boson t-J model of cuprates with high superconducting transition temperatures, and derive its low-energy effective field theory for the charge-spin separated state in a self-consistent manner. The phase degrees of freedom of the mean field for hoppings of holons and spinons can be regarded as a U(1) gauge field, $A_i$. The charge-spin separation occurs below certain temperature, $T_{\rm CSS}$, as a deconfinement phenomenon of the dynamics of $A_i$. Below certain temperature $T_{\rm SG} (< T_{\rm CSS})$, the spin-gap phase develops as the Higgs phase of the gauge-field dynamics, and $A_i$ acquires a mass $m_A$. The effective field theory near $T_{\rm SG}$ takes the form of Ginzburg-Landau theory of a complex scalar field $\lambda$ coupled with $A_i$, where $\lambda$ represents d-wave pairings of spinons. Three dimensionality of the system is crucial to realize a phase transition at $T_{\rm SG}$. By using this field theory, we calculate the dc resistivity $\rho$. At $T > T_{\rm SG}$, $\rho$ is proportional to $T$. At $T < T_{\rm SG}$, it deviates downward from the $T$-linear behavior as $\rho \propto T \{1 -c(T_{\rm SG}-T)^d \}$. When the system is near (but not) two dimensional, due to the compactness of the phase of the field $\lambda$, the exponent $d$ deviates from its mean-field value 1/2 and becomes a nonuniversal quantity which depends on temperature and doping. This significantly improves the comparison with the experimental data

Centrality dependence of charged-particle pseudorapidity distributions from d+Au collisions at sqrt(s_{NN})=200 GeV

Charged-particle pseudorapidity densities are presented for the d+Au reaction at sqrt{s_{NN}}=200 GeV with -4.2 <= eta <= 4.2$. The results, from the BRAHMS experiment at RHIC, are shown for minimum-bias events and 0-30%, 30-60%, and 60-80% centrality classes. Models incorporating both soft physics and hard, perturbative QCD-based scattering physics agree well with the experimental results. The data do not support predictions based on strong-coupling, semi-classical QCD. In the deuteron-fragmentation region the central 200 GeV data show behavior similar to full-overlap d+Au results at sqrt{s_{NN}}=19.4 GeV.Comment: 4 pages, 3figures; expanded discussion of uncertainties; added 60-80% centrality range; added additional discussion on centrality selection bia