41,506 research outputs found
Political Shaping Of Transitions To Biofuels In Europe, Brazil And The USA
Faced with major challenges of global climate change, declining fossil fuel reserves, and competition between alternative uses of land, the transition to renewable transport fuels has been marked by new modes of political economic governance and the strategic direction of innovation. In this paper, we compare the different trajectories to the development and uptake of biofuels in Europe, Brazil and the USA. In terms of the timing, direction, and development of biofuels for road transport, the early lead taken by Brazil in sugarcane based ethanol and flex-fuel cars, the USA drive to corn-to-ethanol, and the European domination of biodiesel from rapeseed, manifest significant contrasts at many levels. Adopting a neo-Polanyian ?instituted economic process? approach we argue that the contrasting trajectories exemplify the different modes of politically instituting markets. We analyse the contrasting weight and impact of different drivers in each case (energy security, climate change mitigation, rural economy development, and market opportunity) in the context of diverse initial conditions and resource endowments. We explore the ?politics of markets? that arise from the different modes of instituting markets for ecologically sustainable economic growth, including the role of NGOs, the scientific controversies over land-use change, and the contrasting political institutions in our case studies. We also place our analysis in the historical perspective of other major carbon energy transitions (charcoal to coal, coal to petrochemicals). In so doing, we explore the idea of the emergence of new modes of governance of contemporary capitalist political economies, and the significance of politically directed innovation. The research is based on an extensive primary research programme of in-depth interviews with strategic players in each of the geographic regions, qualitative institutional analysis, a scenario workshop, and secondary data analysis
Public or private economies of knowledge: The economics of diffusion and appropriation of bioinformatics tools
The past three decades have witnessed a period of great turbulence in the economies of biological knowledge, during which there has been great uncertainty as to how and where boundaries could be drawn between public or private knowledge especially with regard to the explosive growth in biological databases and their related bioinformatic tools. This paper will focus on some of the key software tools developed in relation to bio-databases. It will argue that bioinformatic tools are particularly economically unstable, and that there is a continuing tension and competition between their public and private modes of production, appropriation, distribution, and use. The paper adopts an ?instituted economic process? approach, and in this paper will elaborate on processes of making knowledge public in the creation of ?public goods?. The question is one of continuously creating and sustaining new institutions of the commons. We believe this critical to an understanding of the division and interdependency between public and private economies of knowledge
Focussing effects in laser-electron Thomson scattering
We study the effects of laser pulse focussing on the spectral properties of
Thomson scattered radiation. Modelling the laser as a paraxial beam we find
that, in all but the most extreme cases of focussing, the temporal envelope has
a much bigger effect on the spectrum than the focussing itself. For the case of
ultra-short pulses, where the paraxial model is no longer valid, we adopt a
sub-cycle vector beam description of the field. It is found that the emission
harmonics are blue shifted and broaden out in frequency space as the pulse
becomes shorter. Additionally the carrier envelope phase becomes important,
resulting in an angular asymmetry in the spectrum. We then use the same model
to study the effects of focussing beyond the limit where the paraxial expansion
is valid. It is found that fields focussed to sub-wavelength spot sizes produce
spectra that are qualitatively similar to those from sub-cycle pulses due to
the shortening of the pulse with focussing. Finally, we study high-intensity
fields and find that, in general, the focussing makes negligible difference to
the spectra in the regime of radiation reaction.Comment: 14 pages, 17 figure
D0-brane tension in string field theory
We compute the D0-brane tension in string field theory by representing it as
a tachyon lump of the D1-brane compactified on a circle of radius . To this
aim, we calculate the lump solution in level truncation up to level L=8. The
normalized D0-brane tension is independent on . The compactification radius
is therefore chosen in order to cancel the subleading correction . We
show that an optimal radius indeed exists and that at the
theoretical prediction for the tension is reproduced at the level of .
As a byproduct of our calculation we also discuss the determination of the
marginal tachyon field at .Comment: 13 pages, 3 Eps figure
Beyond the random phase approximation: Stimulated Brillouin backscatter for finite laser coherence times
We develop a statistical theory of stimulated Brillouin backscatter (BSBS) of
a spatially and temporally partially incoherent laser beam for laser fusion
relevant plasma. We find a new collective regime of BSBS (CBSBS) with intensity
threshold controlled by diffraction, an insensitive function of the laser
coherence time, , once light travel time during exceeds a laser
speckle length. The BSBS spatial gain rate is approximately the sum of that due
to CBSBS, and a part which is independent of diffraction and varies linearly
with . We find that the bandwidth of KrF-laser-based fusion systems would
be large enough to allow additional suppression of BSBS.Comment: 8 pages, 5 figures. arXiv admin note: substantial text overlap with
arXiv:1105.209
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