524 research outputs found
Towards resilience through systems-based plant breeding. A review
How the growing world population can feed itself is a crucial, multi-dimensional problem that goes beyond sustainable development. Crop production will be affected by many changes in its climatic, agronomic, economic, and societal contexts.
Therefore, breeders are challenged to produce cultivars that strengthen both ecological and societal resilience by striving for
six international sustainability targets: food security, safety and quality; food and seed sovereignty; social justice;
agrobiodiversity; ecosystem services; and climate robustness. Against this background, we review the state of the art in plant
breeding by distinguishing four paradigmatic orientations that currently co-exist: community-based breeding, ecosystem-based
breeding, trait-based breeding, and corporate-based breeding, analyzing differences among these orientations. Our main findings
are: (1) all four orientations have significant value but none alone will achieve all six sustainability targets; (2) therefore, an
overarching approach is needed: “systems-based breeding,” an orientation with the potential to synergize the strengths of the
ways of thinking in the current paradigmatic orientations; (3) achieving that requires specific knowledge development and
integration, a multitude of suitable breeding strategies and tools, and entrepreneurship, but also a change in attitude based on
corporate responsibility, circular economy and true-cost accounting, and fair and green policies. We conclude that systems-based
breeding can create strong interactions between all system components. While seeds are part of the common good and the basis of
agrobiodiversity, a diversity in breeding approaches, based on different entrepreneurial approaches, can also be considered part of
the required agrobiodiversity. To enable systems-based breeding to play a major role in creating sustainable agriculture, a shared
sense of urgency is needed to realize the required changes in breeding approaches, institutions, regulations and protocols. Based
on this concept of systems-based breeding, there are opportunities for breeders to play an active role in the development of an
ecologically and societally resilient, sustainable agriculture
Interplay between shear loading and structural aging in a physical gel
We show that the aging of the mechanical relaxation of a gelatin gel exhibits
the same scaling phenomenology as polymer and colloidal glasses. Besides,
gelatin is known to exhibit logarithmic structural aging (stiffening). We find
that stress accelerates this process. However, this effect is definitely
irreducible to a mere age shift with respect to natural aging. We suggest that
it is interpretable in terms of elastically-aided elementary (coilhelix)
local events whose dynamics gradually slows down as aging increases geometric
frustration
Field-scale validation of an automated soil nitrate extraction and measurement system
One of the many gaps that needs to be solved by precision agriculture technologies is the availability of an economic, automated, on-the-go mapping system that can be used to obtain intensive and accurate ‘real-time’ data on the levels of nitrate nitrogen (NO3–N) in the soil. A soil nitrate mapping system (SNMS) has been developed to provide a way to collect such data. This study was done to provide extensive field-scale validation testing of the system’s nitrate extraction and measurement sub-unit (NEMS) in two crop (wheat and carrot) production systems. Field conditions included conventional tillage (CT) versus no tillage (NT), inorganic versus organic fertilizer application, four soil groups and three points in time throughout the season. Detailed data analysis showed that: (i) the level of agreement, as measured by root mean squared error (RMSE), mean absolute error (MAE) and coefficient of efficiency (CE), between NEMS soil NO3–N and standard laboratory soil NO3–N measurements was excellent; (ii) at the field-scale, there was little practical difference when using either integer or real number data processing; (iii) regression equations can be used to enable field measurements of soil NO3–N using the NEMS to be obtained with laboratory accuracy; (iv) future designs of the SNMS’s control system can continue to use cheaper integer chip technology for processing the nitrate ion-selective electrode (NO3 -–ISE) readings; and (v) future designs of the SNMS would not need a soil moisture sensor, ultimately saving on manufacturing costs of a more simple syste
Spatially heterogeneous dynamics in granular compaction
We prove the emergence of spatially correlated dynamics in slowly compacting
dense granular media by analyzing analytically and numerically multi-point
correlation functions in a simple particle model characterized by slow
non-equilibrium dynamics. We show that the logarithmically slow dynamics at
large times is accompanied by spatially extended dynamic structures that
resemble the ones observed in glass-forming liquids and dense colloidal
suspensions. This suggests that dynamic heterogeneity is another key common
feature present in very different jamming materials.Comment: 4 pages, 3 figure
Effective field theory of 3He
3He and the triton are studied as three-body bound states in the effective
field theory without pions. We study 3He using the set of integral equations
developed by Kok et al. which includes the full off-shell T-matrix for the
Coulomb interaction between the protons. To leading order, the theory contains:
two-body contact interactions whose renormalized strengths are set by the NN
scattering lengths, the Coulomb potential, and a three-body contact
interaction. We solve the three coupled integral equations with a sharp
momentum cutoff, Lambda, and find that a three-body interaction is required in
3He at leading order, as in the triton. It also exhibits the same limit-cycle
behavior as a function of Lambda, showing that the Efimov effect remains in the
presence of the Coulomb interaction. We also obtain the difference between the
strengths of the three-body forces in 3He and the triton.Comment: 18 pages, 6 figures; further discussion and references adde
Temperature Chaos, Rejuvenation and Memory in Migdal-Kadanoff Spin Glasses
We use simulations within the Migdal-Kadanoff real space renormalization
approach to probe the scales relevant for rejuvenation and memory in spin
glasses. One of the central questions concerns the role of temperature chaos.
First we investigate scaling laws of equilibrium temperature chaos, finding
super-exponential decay of correlations but no chaos for the total free energy.
Then we perform out of equilibrium simulations that follow experimental
protocols. We find that: (1) rejuvenation arises at a length scale smaller than
the ``overlap length'' l(T,T'); (2) memory survives even if equilibration goes
out to length scales much larger than l(T,T').Comment: 4 pages, 4 figures, added references, slightly changed content,
modified Fig.
Glass transition in self organizing cellular patterns
We have considered the dynamical evolution of cellular patterns controlled by
a stochastic Glauber process determined by the deviations of local cell
topology from that of a crystalline structure. Above a critical temperature
evolution is towards a common equilibrium state from any initial configuration,
but beneath this temperature there is a dynamical phase transition, with a
start from a quasi-random state leading to non-equilibrium glassy freezing
whereas an ordered start rests almost unchanged. A temporal persistence
function decays exponentially in the high temperature equilibrating state but
has a characteristic slow non-equilibrium aging-like behaviour in the low
temperature glassy phase.Comment: Added references, text minor change
Field cooling memory effect in Bi2212 and Bi2223 single crystals
A memory effect in the Josephson vortex system created by magnetic field in
the highly anisotropic superconductors Bi2212 and Bi2223 is demonstrated using
microwave power absorption. This surprising effect appears despite a very low
viscosity of Josephson vortices compared to Abrikosov vortices. The
superconductor is field cooled in DC magnetic field H_{m} oriented parallel to
the CuO planes through the critical temperature T_{c} down to 4K, with
subsequent reduction of the field to zero and again above H_{m}. Large
microwave power absorption signal is observed at a magnetic field just above
the cooling field clearly indicating a memory effect. The dependence of the
signal on deviation of magnetic field from H_{m} is the same for a wide range
of H_{m} from 0.15T to 1.7T
Ageing and dynamical scaling in the critical Ising spin glass
The non-equilibrium ageing behaviour of the 3D and 4D critical Ising spin
glass is studied for both binary and gaussian disorder. The same phenomenology
of the time-dependent scaling as in non-disordered magnets is found but the
non-equilibrium exponents and the universal limit fluctuation-dissipation ratio
depend on the distribution of the coupling constants.Comment: Latex2e, 7 pages with epl macro, 4 figures included, final for
- …