1,982 research outputs found
Spin orbit coupling at the level of a single electron
We utilize electron counting techniques to distinguish a spin conserving fast
tunneling process and a slower process involving spin flips in
AlGaAs/GaAs-based double quantum dots. By studying the dependence of the rates
on the interdot tunnel coupling of the two dots, we find that as many as 4% of
the tunneling events occur with a spin flip related to spin-orbit coupling in
GaAs. Our measurement has a fidelity of 99 % in terms of resolving whether a
tunneling event occurred with a spin flip or not
Quantum Noise Measurement of a Carbon Nanotube Quantum Dot in the Kondo Regime
The current emission noise of a carbon nanotube quantum dot in the Kondo
regime is measured at frequencies of the order or higher than the
frequency associated with the Kondo effect , with the Kondo
temperature. The carbon nanotube is coupled via an on-chip resonant circuit to
a quantum noise detector, a superconductor-insulator-superconductor junction.
We find for a Kondo effect related singularity at a
voltage bias , and a strong reduction of this singularity
for , in good agreement with theory. Our experiment
constitutes a new original tool for the investigation of the non-equilibrium
dynamics of many-body phenomena in nanoscale devices.Comment: 6 pages, 4 figure
Variation in carbon footprint of milk due to management differences between Swedish dairy farms
To identify mitigation options to reduce greenhouse gas (GHG) emissions from milk production (i.e. the carbon footprint (CF) of milk), this study examined the variation in GHG emissions among dairy farms using data from previous CF studies on Swedish milk. Variation between farms in these production data, which were found to have a strong influence on milk CF were obtained from existing databases of e.g. 1051 dairy farms in Sweden in 2005. Monte Carlo analysis was used to analyse the impact of variations in seven important parameters on milk CF concerning milk yield (energy corrected milk (ECM) produced and delivered), feed dry matter intake (DMI), enteric methane emissions, N content in feed DMI, N-fertiliser rate and diesel used on farm. The largest between farm variation among the analysed production data were N-fertiliser rate (kg/ha) and diesel used (l/ha) on farm (coefficient of variation (CV) 31-38%). For the parameters concerning milk yield and feed DMI the CV was approx. 11 and 8%, respectively. The smallest variation in production data was found for N content in feed DMI. According to the Monte Carlo analysis, these variations in production data led to a variation in milk CF of between 0.94 and 1.33 kg CO2 equivalents (CO2e) per kg ECM, with an average value of 1.13 kg/CO2e kg ECM. We consider that this variation of ±17% that was found based on the used farm data would be even greater if all Swedish dairy farms were included, as the sample of farms in this study was not totally unbiased. The variation identified in milk CF indicates that a potential exists to reduce GHG emissions from milk production on both national and farm level through changes in management. As milk yield and feed DMI are two of the most influential parameters for milk CF, feed conversion efficiency (i.e. units ECM produced per unit DMI) can be used as a rough key performance indicator for predicting CF reductions. However, it must be borne in mind that feeds have different CF due to where and how they are produced
Whole-ecosystem experimental manipulations of tropical forests.
Tropical forests are highly diverse systems involving extraordinary numbers of interactions between species, with each species responding in a different way to the abiotic environment. Understanding how these systems function and predicting how they respond to anthropogenic global change is extremely challenging. We argue for the necessity of 'whole-ecosystem' experimental manipulations, in which the entire ecosystem is targeted, either to reveal the functioning of the system in its natural state or to understand responses to anthropogenic impacts. We survey the current range of whole-ecosystem manipulations, which include those targeting weather and climate, nutrients, biotic interactions, human impacts, and habitat restoration. Finally we describe the unique challenges and opportunities presented by such projects and suggest directions for future experiments.This review was initiated during a symposium on ‘The effects of large
scale manipulations of tropical forests on arthropod assemblages’ at the
INTECOL 2013 congress, London 18–23 August 2013. T.M.F. is funded
by the Australian Research Council (DP140101541), T.M.F. and R.M.E.
by Yayasan Sime Darby, TMF and Y.B. by the project Biodiversity
of Forest Ecosystems (CZ.1.07/2.3.00/20.0064) co-financed by the
European Social Fund and the state budget of the Czech Republic,
and T.M.F. Y.B. and V.N. by the Czech Science Foundation (GACR
14-32302S, 14-36098G, 14-04258S respectively). Y.B. is also supported
by the Sistema Nacional de Investigacio´n of Panama. E.C.T. is
supported by funds from PT SMART Research Institute and the Isaac
Newton Trust, Cambridge. R.M.E. is supported by European Research
Council Project number 281986. We are grateful to Maureen Fayle,
Andrew Hector, Jan Leps, Scott Miller, Kalsum M. Yusah, Paul Craze,
and two anonymous reviewers for advice during the drafting of the
manuscript, and Jennifer Balch for additional information regarding
her burning experiments.This is the final published version. It first appeared at http://www.cell.com/trends/ecology-evolution/abstract/S0169-5347%2815%2900069-5
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