2,349 research outputs found
An evolutionary economic perspective on technical change and adjustment in cane harvesting systems in the Australian sugar industry
Australian sugar-producing regions have differed in terms of the extent and rate of incorporation of new technology into harvesting systems. The Mackay sugar industry has lagged behind most other sugar-producing regions in this regard. The reasons for this are addressed by invoking an evolutionary economics perspective. The development of harvesting systems, and the role of technology in shaping them, is mapped and interpreted using the concept of path dependency. Key events in the evolution of harvesting systems are identified, which show how the past has shaped the regional development of harvesting systems. From an evolutionary economics perspective, the outcomes observed are the end result of a specific history.Crop Production/Industries,
Product recognition in store shelves as a sub-graph isomorphism problem
The arrangement of products in store shelves is carefully planned to maximize
sales and keep customers happy. However, verifying compliance of real shelves
to the ideal layout is a costly task routinely performed by the store
personnel. In this paper, we propose a computer vision pipeline to recognize
products on shelves and verify compliance to the planned layout. We deploy
local invariant features together with a novel formulation of the product
recognition problem as a sub-graph isomorphism between the items appearing in
the given image and the ideal layout. This allows for auto-localizing the given
image within the aisle or store and improving recognition dramatically.Comment: Slightly extended version of the paper accepted at ICIAP 2017. More
information @project_page -->
http://vision.disi.unibo.it/index.php?option=com_content&view=article&id=111&catid=7
Non-perturbative k-body to two-body commuting conversion Hamiltonians and embedding problem instances into Ising spins
An algebraic method has been developed which allows one to engineer several
energy levels including the low-energy subspace of interacting spin systems. By
introducing ancillary qubits, this approach allows k-body interactions to be
captured exactly using 2-body Hamiltonians. Our method works when all terms in
the Hamiltonian share the same basis and has no dependence on perturbation
theory or the associated large spectral gap. Our methods allow problem instance
solutions to be embedded into the ground energy state of Ising spin systems.
Adiabatic evolution might then be used to place a computational system into
it's ground state.Comment: Published versio
EntscheidungsunterstĂŒtzung bei der Gestaltung von Agrarumweltprogrammen
In dem Beitrag wird dargelegt, wie in Zusammenarbeit von Wissenschaft, Politik und Verwaltung konÂkrete EntscheidungsunterstĂŒtzung fĂŒr die Politikgestaltung in komplexen Systemen geleistet werden kann. Zur Anwendung kommt ein interaktiver PC-gestĂŒtzter Programmierungsansatz, dessen Möglichkeiten fĂŒr die Verbesserung von Agrarumweltprogrammen in Sachsen-Anhalt genutzt werden. Gemeinsam mit den betroffenen Akteuren wird auf der Grundlage interaktiv durchgefĂŒhrter Simulationsrechungen unter Einbeziehung verschiedener Einflussfaktoren (Zielgewichtung, KofinanzierungssĂ€tze und Budgetumfang) eine Strategie zur Verbesserung des Agrarumweltprogramms entwickelt.Peer Reviewe
Priming by Chemokines Restricts Lateral Mobility of the Adhesion Receptor LFA-1 and Restores Adhesion to ICAM-1 Nano-Aggregates on Human Mature Dendritic Cells
LFA-1 is a leukocyte specific ÎČ2 integrin that plays a major role in regulating adhesion and migration of different immune cells. Recent data suggest that LFA-1 on mature dendritic cells (mDCs) may function as a chemokine-inducible anchor during homing of DCs through the afferent lymphatics into the lymph nodes, by transiently switching its molecular conformational state. However, the role of LFA-1 mobility in this process is not yet known, despite that the importance of lateral organization and dynamics for LFA-1-mediated adhesion regulation is broadly recognized. Using single particle tracking approaches we here show that LFA-1 exhibits higher mobility on resting mDCs compared to monocytes. Lymphoid chemokine CCL21 stimulation of the LFA-1 high affinity state on mDCs, led to a significant reduction of mobility and an increase on the fraction of stationary receptors, consistent with re-activation of the receptor. Addition of soluble monomeric ICAM-1 in the presence of CCL21 did not alter the diffusion profile of LFA-1 while soluble ICAM-1 nano-aggregates in the presence of CCL21 further reduced LFA-1 mobility and readily bound to the receptor. Overall, our results emphasize the importance of LFA-1 lateral mobility across the membrane on the regulation of integrin activation and its function as adhesion receptor. Importantly, our data show that chemokines alone are not sufficient to trigger the high affinity state of the integrin based on the strict definition that affinity refers to the adhesion capacity of a single receptor to its ligand in solution. Instead our data indicate that nanoclustering of the receptor, induced by multi-ligand binding, is required to maintain stable cell adhesion once LFA-1 high affinity state is transiently triggered by inside-out signals.Peer ReviewedPostprint (published version
Ultrafast Coulomb-induced dynamics of 2D magnetoexcitons
We study theoretically the ultrafast nonlinear optical response of quantum
well excitons in a perpendicular magnetic field. We show that for
magnetoexcitons confined to the lowest Landau levels, the third-order
four-wave-mixing (FWM) polarization is dominated by the exciton-exciton
interaction effects. For repulsive interactions, we identify two regimes in the
time-evolution of the optical polarization characterized by exponential and
{\em power law} decay of the FWM signal. We describe these regimes by deriving
an analytical solution for the memory kernel of the two-exciton wave-function
in strong magnetic field. For strong exciton-exciton interactions, the decay of
the FWM signal is governed by an antibound resonance with an
interaction-dependent decay rate. For weak interactions, the continuum of
exciton-exciton scattering states leads to a long tail of the time-integrated
FWM signal for negative time delays, which is described by the product of a
power law and a logarithmic factor. By combining this analytic solution with
numerical calculations, we study the crossover between the exponential and
non-exponential regimes as a function of magnetic field. For attractive
exciton-exciton interaction, we show that the time-evolution of the FWM signal
is dominated by the biexcitonic effects.Comment: 41 pages with 11 fig
Theory of exciton-exciton correlation in nonlinear optical response
We present a systematic theory of Coulomb interaction effects in the
nonlinear optical processes in semiconductors using a perturbation series in
the exciting laser field. The third-order dynamical response consists of
phase-space filling correction, mean-field exciton-exciton interaction, and
two-exciton correlation effects expressed as a force-force correlation
function. The theory provides a unified description of effects of bound and
unbound biexcitons, including memory-effects beyond the Markovian
approximation. Approximations for the correlation function are presented.Comment: RevTex, 35 pages, 10 PostScript figs, shorter version submitted to
Physical Review
On the Runtime Analysis of the Clearing Diversity-Preserving Mechanism
Clearing is a niching method inspired by the principle of assigning the available resources
among a niche to a single individual. The clearing procedure supplies these resources only to
the best individual of each niche: the winner. So far, its analysis has been focused on experimental
approaches that have shown that clearing is a powerful diversity-preserving mechanism.
Using rigorous runtime analysis to explain how and why it is a powerful method, we prove that
a mutation-based evolutionary algorithm with a large enough population size, and a phenotypic
distance function always succeeds in optimising all functions of unitation for small niches
in polynomial time, while a genotypic distance function requires exponential time. Finally, we
prove that with phenotypic and genotypic distances clearing is able to find both optima for
Twomax and several general classes of bimodal functions in polynomial expected time. We
use empirical analysis to highlight some of the characteristics that makes it a useful mechanism
and to support the theoretical results
Determination of the Michel Parameters rho, xi, and delta in tau-Lepton Decays with tau --> rho nu Tags
Using the ARGUS detector at the storage ring DORIS II, we have
measured the Michel parameters , , and for
decays in -pair events produced at
center of mass energies in the region of the resonances. Using
as spin analyzing tags, we find , , , , and . In addition, we report
the combined ARGUS results on , , and using this work
und previous measurements.Comment: 10 pages, well formatted postscript can be found at
http://pktw06.phy.tu-dresden.de/iktp/pub/desy97-194.p
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