CHP or biofuel production in Europe?

In this study, the opportunity to invest in combined heat and power (CHP) plants and second-generation biofuel production plants in Europe is investigated. To determine the number and type of production plants, a mixed integer linear model is used, based on minimization of the total cost of the whole suply chain. Different policy scenarios are studied with varying values of carbon cost and biofuel support. The study focuses on the type of technology to invest in and the CO2 emission substitution potential, at constant energy prices. The CHP plants and the biofuel production plants are competing for the same feedstock (forest biomass), which is available in limited quantities. The results show that CP plants are preferred over biofuel production plants at high carbon costs (over 50 EUR/tCO2) and low biofuel support (below 10 EUR/GJ), whereas more biofuel production plants would be set up at high biofuel support (over 15 EUR/GJ), irrespective of the carbon cost. Regarding the CO2 emission substitution potential, the highest potential can be reached at a high carbon cost and low biofuel support. It is concluded that there is a potential conflict of interest between policies promoting increased use of biofuels, and policies aiming at decreased CO2 emissions

Status of RF power couplers for superconducting cavities at CERN

For LEP2 fixed RF power couplers of the open-ended coaxial line type with d.c. bias are used. The nominal power under matched conditions is about 120 kW at 352 MHz. However, to avoid ponderomotive instabilities, the cavities may not be detuned, i.e. the reactive beam loading cannot be compensated. The coupler is therefore exposed to standing waves with an equivalent power (travelling-wave (TW) producing the same field as the peak fields on the coupler line) of more than 200 kW. The final design of these couplers, their conditioning sequence and their actual performance are presented. For LHC a motor-driven mobile coupler is required to change the external cavity Q by a factor of four between beam injection and storage. During injection the forward power levels at 400 MHz are about 120 kW CW (for approximately 20 minutes) and 180 kW peak (for several milliseconds). Since practically all this RF power is reflected the equivalent travelling power is 480 kW and 720 kW, respectively. These couplers will be also provided with d.c. bias to suppress multipacting and ³deconditioning²

Electron transport and current fluctuations in short coherent conductors

Employing a real time effective action formalism we analyze electron transport and current fluctuations in comparatively short coherent conductors in the presence of electron-electron interactions. We demonstrate that, while Coulomb interaction tends to suppress electron transport, it may {\it strongly enhance} shot noise in scatterers with highly transparent conducting channels. This effect of excess noise is governed by the Coulomb gap observed in the current-voltage characteristics of such scatterers. We also analyze the frequency dispersion of higher current cumulants and emphasize a direct relation between electron-electron interaction effects and current fluctuations in disordered mesoscopic conductors.Comment: 16 pages, 4 figure

Global Feedstock Scenarios for Bioenergy - Land-Use Change and Trade-Offs

This paper presents scenarios of global feedstock supply for the production of bioenergy under specified social and environmental safeguard provisions. In particular, concerns for the preservation of biodiversity and the reduction of deforestation are considered in different combinations of scenarios. The objectives of this study were 3-fold: (a) to achieve a global perspective using an integrated modeling approach; (b) to frame the boundaries for lower scale assessments; and (c) to identify potential trade-offs to be considered in future research. The aggregate results, achieved through the application of an integrated global modeling cluster, are in line with other studies predicting a doubling of global biomass supplies by mid-century. These supplies will to the largest extent be sourced from the conversion of unmanaged forest into managed forest, from new fast growing short rotation plantations and from intensification as well as optimization of land-use. Depending on the underlying scenario, it can be shown that zero net deforestation by 2020 can be reached and uphold while implying only a minor expansion into managed forests. Results further indicate that especially regions of the southern hemisphere i.e. the tropical belt will face controlled forest conversion from unmanaged to sustainably managed as well as increased protection of area for ecosystems services such as biodiversity. The study concludes with the recommendation of increased focus on targeted regional policy design and implementation following integrated global assessments

Planar Drawings of Fixed-Mobile Bigraphs

A fixed-mobile bigraph G is a bipartite graph such that the vertices of one partition set are given with fixed positions in the plane and the mobile vertices of the other part, together with the edges, must be added to the drawing. We assume that G is planar and study the problem of finding, for a given k >= 0, a planar poly-line drawing of G with at most k bends per edge. In the most general case, we show NP-hardness. For k=0 and under additional constraints on the positions of the fixed or mobile vertices, we either prove that the problem is polynomial-time solvable or prove that it belongs to NP. Finally, we present a polynomial-time testing algorithm for a certain type of "layered" 1-bend drawings

Introduction effort, climate matching and species traits as predictors of global establishment success in non-native reptiles

Non-native reptiles are often detrimental to native communities and ecosystems and can be extremely difficult to manage once established. Thus, there is considerable interest in predicting the likelihood of establishment of nonnative reptiles. We assessed three hypotheses describing possible factors contributing to the successful establishment of introduced reptiles in an effort to better identify potential invaders

Time ordering and counting statistics

The basic quantum mechanical relation between fluctuations of transported charge and current correlators is discussed. It is found that, as a rule, the correlators are to be time-ordered in an unusual way. Instances where the difference with the conventional ordering matters are illustrated by means of a simple scattering model. We apply the results to resolve a discrepancy concerning the third cumulant of charge transport across a quantum point contact.Comment: 19 pages, 1 figure; inconsequential mistake and typos correcte