3,947 research outputs found
An information-theoretic on-line update principle for perception-action coupling
Inspired by findings of sensorimotor coupling in humans and animals, there
has recently been a growing interest in the interaction between action and
perception in robotic systems [Bogh et al., 2016]. Here we consider perception
and action as two serial information channels with limited
information-processing capacity. We follow [Genewein et al., 2015] and
formulate a constrained optimization problem that maximizes utility under
limited information-processing capacity in the two channels. As a solution we
obtain an optimal perceptual channel and an optimal action channel that are
coupled such that perceptual information is optimized with respect to
downstream processing in the action module. The main novelty of this study is
that we propose an online optimization procedure to find bounded-optimal
perception and action channels in parameterized serial perception-action
systems. In particular, we implement the perceptual channel as a multi-layer
neural network and the action channel as a multinomial distribution. We
illustrate our method in a NAO robot simulator with a simplified cup lifting
task.Comment: 8 pages, 2017 IEEE/RSJ International Conference on Intelligent Robots
and Systems (IROS
Time Averaged VHE Spectrum of Mrk 421 in 2005
The blazar Mrk421 was observed independently, but contemporaneously, in 2005
at TeV energies by MAGIC, the Whipple 10m telescope, and by a single VERITAS
telescope during the construction phase of operations. A comparison of the time
averaged spectra, in what was a relatively quiescent state, demonstrates the
level of agreement between instruments. In addition, the increased sensitivity
of the new generation instruments, and ever decreasing energy thresholds,
questions how best to compare new observational data with archival results.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium
on High Energy Gamma-Ray Astronomy 2008
Non-Contact Measurement of Thermal Diffusivity in Ion-Implanted Nuclear Materials
Knowledge of mechanical and physical property evolution due to irradiation
damage is essential for the development of future fission and fusion reactors.
Ion-irradiation provides an excellent proxy for studying irradiation damage,
allowing high damage doses without sample activation. Limited
ion-penetration-depth means that only few-micron-thick damaged layers are
produced. Substantial effort has been devoted to probing the mechanical
properties of these thin implanted layers. Yet, whilst key to reactor design,
their thermal transport properties remain largely unexplored due to a lack of
suitable measurement techniques. Here we demonstrate non-contact thermal
diffusivity measurements in ion-implanted tungsten for nuclear fusion armour.
Alloying with transmutation elements and the interaction of retained gas with
implantation-induced defects both lead to dramatic reductions in thermal
diffusivity. These changes are well captured by our modelling approaches. Our
observations have important implications for the design of future fusion power
plants.Comment: 15 pages, 3 figure
Zu altertumswissenschaftlichen Kartierungspraktiken
Altertumswissenschaftliche Karten sind nicht als unabhängi-
ge wissenschaftliche Instrumente zu betrachten, sondern als
technische Dinge, die auf der Sedimentation älterer Arbei-
ten sowie den Instrumenten, Sprachen und Praktiken anderer
Disziplinen beruhen. Durch diese Grundlegungen wurde die
Kartographie der verschiedenen Altertumswissenschaften von
Beginn an präjudiziert und in ein System spezifischer regio-
naler, disziplinärer, wissenschaftspolitischer und politischer
Konstellationen eingebunden. In der Einleitung des Sammel-
bandes, der Beispiele zur Kartierung kollektiver Entitäten aus
verschiedenen Altertumswissenschaften, aber auch aus der
Humangeographie und der Linguistik enthält, setzen wir uns
mit der Frage der Rückkopplungen auf die kartographischen
Strategien zur Darstellung und Identifikation antiker Kollek-
tive auseinander. Hierzu beleuchten wir die altertumswissen-
schaftlichen Kartierungspraktiken aus diagrammatischer, wis-
senschaftsgeschichtlicher und identitätstheoretischer Perspek-
tive
Gtdap-1 and the role of autophagy during planarian regeneration and starvation
Planarians have been established as an ideal model organism for stem cell research and regeneration. Planarian regeneration and homeostasis require an exquisite balancing act between cell death and cell proliferation as new tissues are made (epimorphosis) and existing tissues remodeled (morphallaxis). Some of the genes and mechanisms that control cell proliferation and pattern formation are known. However, studies about cell death during remodeling are few and far between. We have studied the gene Gtdap-1, the planarian ortholog of human death-associated protein-1 or DAP-1. DAP-1 together with DAP-kinase has been identified as a positive mediator of programmed cell death induced by gamma-interferon in HeLa cells. We have found that the gene functions at the interface between autophagy and cell death in the remodeling of the organism that occurs during regeneration and starvation in sexual and asexual races of planarians. Our data suggest that autophagy of existing cells may be essential to fuel the continued proliferation and differentiation of stem cells by providing the necessary energy and building blocks to neoblasts
The Potential of Organic and Inorganic Nutrient Sources in Sub-Saharan African Crop Farming Systems
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