1,626 research outputs found
Transforum system innovation towards sustainable food. A review
Innovations in the agri-food sector are needed to create a sustainable food supply. Sustainable food supply requires unexpectedly that densely populated regions remain food producers. A Dutch innovation program has aimed at showing the way forward through creating a number of practice and scientific projects. Generic lessons from the scientific projects in this program are likely to be of interest to agricultural innovation in other densely populated regions in the world. Based on the executed scientific projects, generic lessons across the whole innovation program are derived. We found that the agricultural sector requires evolutionary rather than revolutionary changes to reshaping institutions. Measuring sustainability is possible against benchmarks and requires stakeholder agreement on sustainability values. Results show the importance of multiple social views and multiple stakeholder involvement in agricultural innovation. Findings call for flexible goal rather than process-oriented management of innovation. Findings also emphasise the essential role of profit in anchoring sustainable development in business. The results agree with concepts of evolutionary innovation. We conclude that there is no single best solution to making the agri-food sector more sustainable densely populated areas, but that the combination of a range of solutions and approaches is likely to provide the best way forward
On the Currents and Transports Connected With the Atlantic Meridional Overturning Circulation in the Subpolar North Atlantic
Results from an interannually forced, 0.08 degrees eddy-resolving simulation based on the Hybrid Coordinate Ocean Model, in conjunction with a small but well-determined transport database, are used to investigate the currents and transports associated with the Atlantic meridional overturning circulation (AMOC) in the subpolar North Atlantic (SPNA). The model results yield a consistent warming in the western SPNA since the early 1990s, along with mean transports similar to those observed for the trans-basin AMOC across the World Ocean Circulation Experiment hydrographic section AR19 (16.4 Sv) and boundary currents at the exit of the Labrador Sea near 53 degrees N (39.0 Sv) and east of the Grand Banks near 43 degrees N (15.9 Sv). Over a 34 year integration, the model-determined AMOC across the AR19 section and the western boundary current near 53 degrees N both exhibit no systematic trend but some long-term (interannual and longer) variabilities, including a decadal transport variation of 3-4 Sv from relatively high in the 1990s to low in the 2000s. The decadal variability of the model boundary current transport near 53 degrees N lags the observed winter time North Atlantic Oscillation index by about 2 years and leads the model AMOC across the AR19 section by about 1 year. The model results also show that the long-term variabilities are low compared to those on shorter time scales. Thus, rapid sampling of the current over long time intervals is required to filter out high-frequency variabilities in order to determine the lower frequency variabilities of interest. Citation: Xu, X., H. E. Hurlburt, W. J. Schmitz Jr., R. Zantopp, J. Fischer, and P. J. Hogan (2013), On the currents and transports connected with the atlantic meridional overturning circulation in the subpolar North Atlantic, J. Geophys. Res. Oceans, 118, 502-516, doi:10.1002/jgrc.20065
Relativistic transition wavelenghts and probabilities for spectral lines of Ne II
Transition wavelengths and probabilities for several 2p4 3p - 2p4 3s and 2p4
3d - 2p4 3p lines in fuorine-like neon ion (NeII) have been calculated within
the multiconfiguration Dirac-Fock (MCDF) method with quantum electrodynamics
(QED) corrections. The results are compared with all existing experimental and
theoretical data
Chiral and deconfinement transition from correlation functions: SU(2) vs. SU(3)
We study a gauge invariant order parameter for deconfinement and the chiral
condensate in SU(2) and SU(3) Yang-Mills theory in the vicinity of the
deconfinement phase transition using the Landau gauge quark and gluon
propagators. We determine the gluon propagator from lattice calculations and
the quark propagator from its Dyson-Schwinger equation, using the gluon
propagator as input. The critical temperature and a deconfinement order
parameter are extracted from the gluon propagator and from the dependency of
the quark propagator on the temporal boundary conditions. The chiral transition
is determined using the quark condensate as order parameter. We investigate
whether and how a difference in the chiral and deconfinement transition between
SU(2) and SU(3) is manifest.Comment: 15 pages, 9 figures. For clarification one paragraph and two
references added in the introduction and two sentences at the end of the
first and last paragraph of the summary. Appeared in EPJ
What Does Low Energy Physics Tell Us About The Zero Momentum Gluon Propagator
The connection between QCD, a nonlocal Nambu--Jona-Lasinio type model and the
Landau gauge gluon propagator is explored. This two point function is
parameterized by a functional form which is compatible with Dyson-Schwinger and
lattice QCD results. Demanding the nonlocal model to reproduce the experimental
values for the pion mass, the pion decay constant, and the light quark condensate we conclude that low energy
physics does not distinguish between the so-called decoupling and scaling
solutions of the Dyson-Schwinger equations. This result means that, provided
that the model parameters are chosen appropriately, one is free to chose any of
the above scenarios. Furthermore, the nonlocal Nambu--Jona-Lasinio quark model
considered here is chiral invariant and satisfies the GMOR relation at the 1%
level of precision.Comment: 12 pages, 4 figures, 2 table
Measuring the elements of the optical density matrix
Most methods for experimentally reconstructing the quantum state of light
involve determining a quasiprobability distribution such as the Wigner
function. In this paper we present a scheme for measuring individual density
matrix elements in the photon number state representation. Remarkably, the
scheme is simple, involving two beam splitters and a reference field in a
coherent state.Comment: 6 pages and 1 figur
Is the readmission rate a valid quality indicator? A review of the evidence
Conclusions: Although readmission rates are a promising quality indicator, several methodological concerns identified in this study need to be addressed, especially when the indi
Strong-coupling study of the Gribov ambiguity in lattice Landau gauge
We study the strong-coupling limit beta=0 of lattice SU(2) Landau gauge
Yang-Mills theory. In this limit the lattice spacing is infinite, and thus all
momenta in physical units are infinitesimally small. Hence, the infrared
behavior can be assessed at sufficiently large lattice momenta. Our results
show that at the lattice volumes used here, the Gribov ambiguity has an
enormous effect on the ghost propagator in all dimensions. This underlines the
severity of the Gribov problem and calls for refined studies also at finite
beta. In turn, the gluon propagator only mildly depends on the Gribov
ambiguity.Comment: 14 pages, 22 figures; minor changes, matches version to appear in
Eur. Phys. J.
Accessing directly the properties of fundamental scalars in the confinement and Higgs phase
The properties of elementary particles are encoded in their respective
propagators and interaction vertices. For a SU(2) gauge theory coupled to a
doublet of fundamental complex scalars these propagators are determined in both
the Higgs phase and the confinement phase and compared to the Yang-Mills case,
using lattice gauge theory. Since the propagators are gauge-dependent, this is
done in the Landau limit of 't Hooft gauge, permitting to also determine the
ghost propagator. It is found that neither the gauge boson nor the scalar
differ qualitatively in the different cases. In particular, the gauge boson
acquires a screening mass, and the scalar's screening mass is larger than the
renormalized mass. Only the ghost propagator shows a significant change.
Furthermore, indications are found that the consequences of the residual
non-perturbative gauge freedom due to Gribov copies could be different in the
confinement and the Higgs phase.Comment: 11 pages, 6 figures, 1 table; v2: one minor error corrected; v3: one
appendix on systematic uncertainties added and some minor changes, version to
appear in EPJ
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