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

Maximal positive cross shot noise from Andreev reflection

The current flowing from a superconductor to a two-terminal setup describing a nanostructure connected to normal-metal leads is studied. We provide an example of scattering matrix giving ideal splitting off electrons from a Cooper pair by means of Cauchy-Bunyakovsky-Schwarz inequality. The proposal of the junction and its possible variants are discussed in a context of possible experiments.Comment: 10 pages, 11 figures, to be published in PR

Current density distribution in cylindrical Li-Ion cells during impedance measurements

In this work, modified commercial cylindrical lithium-ion cells with multiple separate current tabs are used to analyze the influence of tab pattern, frequency and temperature on electrochemical impedance spectroscopy. In a first step, the effect of different current tab arrangements on the impedance spectra is analyzed and possible electrochemical causes are discussed. In a second step, one terminal is used to apply a sinusoidal current while the other terminals are used to monitor the local potential distribution at different positions along the electrodes of the cell. It is observed that the characteristic decay of the voltage amplitude along the electrode changes non-linearly with frequency, where high-frequent currents experience a stronger attenuation along the current collector than low-frequent currents. In further experiments, the decay characteristic is controlled by the cell temperature, driven by the increasing resistance of the current collector and the enhanced kinetic and transport properties of the active material and electrolyte. Measurements indicate that the ac current distribution depends strongly on the frequency and the temperature. In this context, the challenges for electrochemical impedance spectroscopy as cell diagnostic technique for commercial cells are discussed

Quantum theory of electromechanical noise and momentum transfer statistics

A quantum mechanical theory is developed for the statistics of momentum transferred to the lattice by conduction electrons. Results for the electromechanical noise power in the semiclassical diffusive transport regime agree with a recent theory based on the Boltzmann-Langevin equation. All moments of the transferred momentum are calculated for a single-channel conductor with a localized scatterer, and compared with the known statistics of transmitted charge.Comment: 10 pages, 2 figure

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

The quest for companions to post-common envelope binaries: I. Searching a sample of stars from the CSS and SDSS

As part of an ongoing collaboration between student groups at high schools and professional astronomers, we have searched for the presence of circum-binary planets in a bona-fide unbiased sample of twelve post-common envelope binaries (PCEBs) from the Catalina Sky Survey (CSS) and the Sloan Digital Sky Survey (SDSS). Although the present ephemerides are significantly more accurate than previous ones, we find no clear evidence for orbital period variations between 2005 and 2011 or during the 2011 observing season. The sparse long-term coverage still permits O-C variations with a period of years and an amplitude of tens of seconds, as found in other systems. Our observations provide the basis for future inferences about the frequency with which planet-sized or brown-dwarf companions have either formed in these evolved systems or survived the common envelope (CE) phase.Comment: accepted by A&

ThermoElectric Transport Properties of a Chain of Quantum Dots with Self-Consistent Reservoirs

We introduce a model for charge and heat transport based on the Landauer-Buttiker scattering approach. The system consists of a chain of $N$ quantum dots, each of them being coupled to a particle reservoir. Additionally, the left and right ends of the chain are coupled to two particle reservoirs. All these reservoirs are independent and can be described by any of the standard physical distributions: Maxwell-Boltzmann, Fermi-Dirac and Bose-Einstein. In the linear response regime, and under some assumptions, we first describe the general transport properties of the system. Then we impose the self-consistency condition, i.e. we fix the boundary values (T_L,\mu_L) and (T_R,mu_R), and adjust the parameters (T_i,mu_i), for i = 1,...,N, so that the net average electric and heat currents into all the intermediate reservoirs vanish. This condition leads to expressions for the temperature and chemical potential profiles along the system, which turn out to be independent of the distribution describing the reservoirs. We also determine the average electric and heat currents flowing through the system and present some numerical results, using random matrix theory, showing that these currents are typically governed by Ohm and Fourier laws.Comment: Minor changes (45 pages

Exciton swapping in a twisted graphene bilayer as a solid-state realization of a two-brane model

It is shown that exciton swapping between two graphene sheets may occur under specific conditions. A magnetically tunable optical filter is described to demonstrate this new effect. Mathematically, it is shown that two turbostratic graphene layers can be described as a "noncommutative" two-sheeted (2+1)-spacetime thanks to a formalism previously introduced for the study of braneworlds in high energy physics. The Hamiltonian of the model contains a coupling term connecting the two layers which is similar to the coupling existing between two braneworlds at a quantum level. In the present case, this term is related to a K-K' intervalley coupling. In addition, the experimental observation of this effect could be a way to assess the relevance of some theoretical concepts of the braneworld hypothesis.Comment: 15 pages, 3 figures, final version published in European Physical Journal

Mapping certified forests for sustainable management - A global tool for information improvement through participatory and collaborative mapping

There are currently no spatially explicit, openly accessible data available on forest certification below national level, so understanding the drivers of certification in the past, examining the scope for further certification and using this information for development of future sustainable forest management strategies is challenging. Hence, this paper presents a methodology for the development of a global map of certified forest areas at 1 km resolution in order to satisfy this information need. Validation of the map with certified areas in Russia showed reasonable results, but the lack of openly accessible data requires broadening the strategy for improving the global certification map in the future. Thus, the second aim of the paper is to present an online tool for visualization and interactive improvement of the global forest certification product through collaborative mapping, aiming at a range of stakeholders including third-party certifiers, green NGOs, forestry organizations, decision-makers, scientists and local experts. Such an approach can help to make more accurate information on forest certification available, promote the sharing of data and encourage more transparent and sustainable forest management, i.e. both producers and users can benefit from this online tool