Bio-IGCC with CCS as a long-term mitigation option in a coupled energy-system and land-use model

This study analyses the impact of techno-economic performance of the BIGCC process and the effect of different biomass feedstocks on the technology's long term deployment in climate change mitigation scenarios. As the BIGCC technology demands high amounts of biomass raw material it also affects the land-use sector and is dependent on conditions and constraints on the land-use side. To represent the interaction of biomass demand and supply side the global energy-economy-climate model ReMIND is linked to the global land-use model MAgPIE. The link integrates biomass demand and price as well as emission prices and land-use emissions. Results indicate that BIGCC with CCS could serve as an important mitigation option and that it could even be the main bioenergy conversion technology sharing 33% of overall mitigation in 2100. The contribution of BIGCC technology to long-term climate change mitigation is much higher if grass is used as fuel instead of wood, provided that the grass-based process is highly efficient. The capture rate has to significantly exceed 60 % otherwise the technology is not applied. The overall primary energy consumption of biomass reacts much more sensitive to price changes of the biomass than to technoeconomic performance of the BIGCC process. As biomass is mainly used with CCS technologies high amounts of carbon are captured ranging from 130 GtC to 240 GtC (cumulated from 2005-2100) in different scenarios

A microscopic approach to critical phenomena at interfaces: an application to complete wetting in the Ising model

We study how the formalism of the Hierarchical Reference Theory (HRT) can be extended to inhomogeneous systems. HRT is a liquid state theory which implements the basic ideas of Wilson momentum shell renormalization group (RG) to microscopic Hamiltonians. In the case of homogeneous systems, HRT provides accurate results even in the critical region, where it reproduces scaling and non-classical critical exponents. We applied the HRT to study wetting critical phenomena in a planar geometry. Our formalism avoids the explicit definition of effective surface Hamiltonians but leads, close to the wetting transition, to the same renormalization group equation already studied by RG techiques. However, HRT also provides information on the non universal quantities because it does not require any preliminary coarse graining procedure. A simple approximation to the infinite HRT set of equations is discussed. The HRT evolution equation for the surface free energy is numerically integrated in a semi-infinite three-dimensional Ising model and the complete wetting phase transition is analyzed. A renormalization of the adsorption critical amplitude and of the wetting parameter is observed. Our results are compared to available Monte Carlo simulations.Comment: To be published in Phy. Rev.

Real firms, transaction costs and firm development: a suggested formalisation

The motivation of this discussion is threefold: to integrate transaction costs (TCs) into a standard model of the firm; to examine the interaction between organisational factors (i.e. TCs) and standard demand-cost factors; and to analyse key propositions of transaction cost economics with the general model. Two sets of results are derived. First, when analysis is based on significant interaction between organisational effort and production costs two possible organisational solutions can exist. First we have a “normal” relationship that the existence of small firms is subject to a threshold effect for transaction complexity. Secondly large firms can develop because of interactions between organisation effort and marketing and production costs. A second key result concerns strategies to shift from small to large solutions that can be based on either “small steps” or “developmental leap”. The viability of these alternatives is shown to depend on transaction complexity that affects the transition costs involved. In short these findings collectively indicate that analysis of the interaction between organisational and technical aspects of the firm using a formal method does indeed add value in terms of our understanding

Nuclear Flow Excitation Function

We consider the dependence of collective flow on the nuclear surface thickness in a Boltzmann--Uehling--Uhlenbeck transport model of heavy ion collisions. Well defined surfaces are introduced by giving test particles a Gaussian density profile of constant width. Zeros of the flow excitation function are as much influenced by the surface thickness as the nuclear equation of state, and the dependence of this effect is understood in terms of a simple potential scattering model. Realistic calculations must also take into account medium effects for the nucleon--nucleon cross section, and impact parameter averaging. We find that balance energy scales with the mass number as $A^{-y}$, where $y$ has a numerical value between 0.35 and 0.5, depending on the assumptions about the in-medium nucleon-nucleon cross section.Comment: 11 pages (LaTeX), 7 figures (not included), MSUCL-884, WSU-NP-93-

N2O emissions from the global agricultural nitrogen cycle – current state and future scenarios

Reactive nitrogen (Nr) is not only an important nutrient for plant growth, thereby safeguarding human alimentation, but it also heavily disturbs natural systems. To mitigate air, land, aquatic, and atmospheric pollution caused by the excessive availability of Nr, it is crucial to understand the long-term development of the global agricultural Nr cycle. For our analysis, we combine a material flow model with a land-use optimization model. In a first step we estimate the state of the Nr cycle in 1995. In a second step we create four scenarios for the 21st century in line with the SRES storylines. Our results indicate that in 1995 only half of the Nr applied to croplands was incorporated into plant biomass. Moreover, less than 10 per cent of all Nr in cropland plant biomass and grazed pasture was consumed by humans. In our scenarios a strong surge of the Nr cycle occurs in the first half of the 21st century, even in the environmentally oriented scenarios. Nitrous oxide (N2O) emissions rise from 3 Tg N2O-N in 1995 to 7–9 in 2045 and 5–12 Tg in 2095. Reinforced Nr pollution mitigation efforts are therefore required

Superdiffusion in a Model for Diffusion in a Molecularly Crowded Environment

We present a model for diffusion in a molecularly crowded environment. The model consists of random barriers in percolation network. Random walks in the presence of slowly moving barriers show normal diffusion for long times, but anomalous diffusion at intermediate times. The effective exponents for square distance versus time usually are below one at these intermediate times, but can be also larger than one for high barrier concentrations. Thus we observe sub- as well as super-diffusion in a crowded environment.Comment: 8 pages including 4 figure

Modification of the rho meson detected by low-mass electron-positron pairs in central Pb-Au collisions at 158 A GeV/c

We present a measurement of $e^+e^-$ pair production in central Pb-Au collisions at 158$A$ GeV/$c$. As reported earlier, a significant excess of the $e^+e^-$ pair yield over the expectation from hadron decays is observed. The improved mass resolution of the present data set, recorded with the upgraded CERES experiment at the CERN-SPS, allows for a comparison of the data with different theoretical approaches. The data clearly favor a substantial in-medium broadening of the $\rho$ spectral function over a density-dependent shift of the $\rho$ pole mass. The in-medium broadening model implies that baryon induced interactions are the key mechanism to in-medium modifications of the $\rho$-meson in the hot fireball at SPS energy.Comment: Revised versio

Event-by-event fluctuations at SPS

Results on event-by-event fluctuations of the mean transverse momentum and net charge in Pb-Au collisions, measured by the CERES Collaboration at CERN-SPS, are presented. We discuss the centrality and beam energy dependence and compare our data to cascade calculations.Comment: 4 pages, 4 figures, proceedings to INPC2004 Goteborg, Swede

Response, relaxation and transport in unconventional superconductors

We investigate the collision-limited electronic Raman response and the attenuation of ultrasound in spin-singlet d-wave superconductors at low temperatures. The dominating elastic collisions are treated within a t-matrix approximation, which combines the description of weak (Born) and strong (unitary) impurity scattering. In the long wavelength limit a two-fluid description of both response and transport emerges. Collisions are here seen to exclusively dominate the relaxational dynamics of the (Bogoliubov) quasiparticle system and the analysis allows for a clear connection of response and transport phenomena. When applied to quasi-2-d superconductors like the cuprates, it turns out that the transport parameter associated with the Raman scattering intensity for B1g and B2g photon polarization is closely related to the corresponding components of the shear viscosity tensor, which dominates the attenuation of ultrasound. At low temperatures we present analytic solutions of the transport equations, resulting in a non-power-law behavior of the transport parameters on temperature.Comment: 22 pages, 3 figure

A minimal quasiparticle approach for the QGP and its large-NcN_c limits

We propose a quasiparticle approach allowing to compute the equation of state of a generic gauge theory with gauge group SU($N_c$) and quarks in an arbitrary representation. Our formalism relies on the thermal quasiparticle masses (quarks and gluons) computed from Hard-Thermal-Loop techniques, in which the standard two-loop running coupling constant is used. Our model is minimal in the sense that we do not allow any extra ansatz concerning the temperature-dependence of the running coupling. We first show that it is able to reproduce the most recent equations of state computed on the lattice for temperatures higher than 2 $T_c$. In this range of temperatures, an ideal gas framework is indeed expected to be relevant. Then we study the accuracy of various inequivalent large-$N_c$ limits concerning the description of the QCD results, as well as the equivalence between the QCD$_{AS}$ limit and the ${\cal N}=1$ SUSY Yang-Mills theory. Finally, we estimate the dissociation temperature of the $\Upsilon$-meson and comment on the estimations' stability regarding the different considered large-$N_c$ limits.Comment: 19 pages, 6 figure