1,176 research outputs found
RAFCON: a Graphical Tool for Task Programming and Mission Control
There are many application fields for robotic systems including service
robotics, search and rescue missions, industry and space robotics. As the
scenarios in these areas grow more and more complex, there is a high demand for
powerful tools to efficiently program heterogeneous robotic systems. Therefore,
we created RAFCON, a graphical tool to develop robotic tasks and to be used for
mission control by remotely monitoring the execution of the tasks. To define
the tasks, we use state machines which support hierarchies and concurrency.
Together with a library concept, even complex scenarios can be handled
gracefully. RAFCON supports sophisticated debugging functionality and tightly
integrates error handling and recovery mechanisms. A GUI with a powerful state
machine editor makes intuitive, visual programming and fast prototyping
possible. We demonstrated the capabilities of our tool in the SpaceBotCamp
national robotic competition, in which our mobile robot solved all exploration
and assembly challenges fully autonomously. It is therefore also a promising
tool for various RoboCup leagues.Comment: 8 pages, 5 figure
A Bayesian model for anchovy (Engraulis encrasicolus): the combined forcing of man and environment
Fishery collapses frequently result from combined
pressures of the environment and man, which are
difficult to discern because of the complexities
involved and our limited knowledge. Models to resolve
this complexity often become too sophisticated,
with too many assumptions and, consequently, with
little capacity to predict beyond calibration data. In
this paper we implement a different procedure where
the model is kept simple and uncertainty accounts for
the equation imperfectness to reproduce ecological
complexity. Human and environmental forcing on an
anchovy (Engraulis encrasicolus) stock are simulated
with only six parameters plus their error terms, and
the uncertainty is computed with Bayesian methods.
The simple structure is able to reproduce the major
dynamical features of this species in the Gulf of
Ca´diz, including data on life stages and age structure
that had no contact with the model. This is a distinct
performance for a frugal approach working on a
mid-trophic species and a positive instance where
parsimony can simulate the interaction of man,
fish and the environment, provided uncertainty is
accounted for in the process.Publicado
Plant’s gypsum affinity shapes responses to specific edaphic constraints without limiting responses to other general constraints
Aims: Harsh edaphic environments harbor species with different soil affinities. Plant’s responses to specific edaphic constraints may be compromised against responses to prevalent stresses shared with other semi-arid environments. We expect that species with high edaphic affinity may show traits to overcome harsh soil properties, while species with low affinity may respond to environmental constraints shared with arid environments. Methods: We quantified the edaphic affinity of 12 plant species co-occurring in gypsum outcrops and measured traits related to plant responses to specific gypsum constraints (rooting and water uptake depth, foliar accumulation of Ca, S and Mg), and traits related to common constraints of arid environments (water use efficiency, macronutrients foliar content). Results: Plants in gypsum outcrops differed in their strategies to face edaphic limitations. A phylogenetic informed PCA segregated species based on their foliar Ca and S accumulation and greater water uptake depths, associated with plant responses to specific gypsum limitations. Species’ gypsum affinity explained this segregation, but traits related to water or nutrient use efficiency did not contribute substantially to this axis. Conclusions: Plant’s specializations to respond to specific edaphic constraints of gypsum soils do not limit their ability to deal with other non-specific environmental constraints
SEDIMENTACIÓN Y DISTRIBUCIÓN SUPERFICIAL DE PALINOMORFOS EN CUEVAS DEL SE IBÉRICO. IMPLICACIONES EN PALEOECOLOGÍA
Pollen from several karstic caves of Mediterranean Spain has been studied in order to understand taphonomic processes affecting cave systems. Results confirm the palaeoecological potential of cave sediments, which show pollen spectra that may reflect external vegetation from both local and regional catchment areas. Pollen distribution, deposition, and preservation are not homogeneous throughout the cave surface, but they are greatly influenced by cave morphology, and stochastic processes. The aridity is a positive factor for pollen preservation, thus enhancing the use of cave deposits as sources of palaeoenvironmental information.Se ha realizado un análisis polínico del sedimento superficial de varias cavidades kársticas de la España mediterránea con el fin de conocer los procesos tafonómicos que afectan al polen en este contexto sedimentario. Los resultados confirman el potencial paleoecológico de los depósitos de cuevas. Los espectros polínicos reflejan la vegetación que crece en los alrededores de la cueva, así como, parcialmente, la vegetación regional. La distribución, deposición y preservación polínicas no son homogéneas en el interior de las cuevas, estando influenciadas por la morfología de la cueva y diversos procesos estocásticos. La aridez se confirma como un factor positivo para la preservación polínica y, por tanto, resulta una garantía en estudios de reconstrucción paleoambiental
Unraveling the extracellular matrix-tumor cell interactions to aid better targeted therapies for neuroblastoma
Treatment in children with high-risk neuroblastoma remains largely unsuccessful due to the development of metastases and drug resistance. The biological complexity of these tumors and their microenvironment represent one of the many challenges to face. Matrix glycoproteins such as vitronectin act as bridge elements between extracellular matrix and tumor cells and can promote tumor cell spreading. In this study, we established through a clinical cohort and preclinical models that the interaction of vitronectin and its ligands, such as αv integrins, are related to the stiffness of the extracellular matrix in high-risk neuroblastoma. These marked alterations found in the matrix led us to specifically target tumor cells within these altered matrices by employing nanomedicine and combination therapy. Loading the conventional cytotoxic drug etoposide into nanoparticles significantly increased its efficacy in neuroblastoma cells. We noted high synergy between etoposide and cilengitide, a high-affinity cyclic pentapeptide αv integrin antagonist. The results of this study highlight the need to characterize cell-extracellular matrix interactions, to improve patient care in high-risk neuroblastoma
Layer-dependent mechanical properties and enhanced plasticity in the van der Waals chromium trihalide magnets
The mechanical properties of magnetic materials are instrumental for the
development of the magnetoelastic theory and the optimization of
strain-modulated magnetic devices. In particular, two-dimensional (2D) magnets
hold promise to enlarge these concepts into the realm of low-dimensional
physics and ultrathin devices. However, no experimental study on the intrinsic
mechanical properties of the archetypal 2D magnet family of the chromium
trihalides has thus far been performed. Here, we report the room temperature
layer-dependent mechanical properties of atomically thin CrI3 and CrCl3,
finding that bilayers of CrI3 and CrCl3 have Young's moduli of 62.1 GPa and
43.4 GPa, with the highest sustained strain of 6.09% and 6.49% and breaking
strengths of 3.6 GPa and 2.2 GPa, respectively. Both the elasticity and
strength of the two materials decrease with increased thickness, which is
attributed to a weak interlayer interaction that enables interlayer sliding
under low levels of applied load. The mechanical properties observed in the
few-layer chromium trihalide crystals provide evidence of outstanding
plasticity in these materials, which is qualitatively demonstrated in their
bulk counterparts. This study will contribute to various applications of the
van der Waals magnetic materials, especially for their use in magnetostrictive
and flexible devices.Comment: Main text and supplementary informatio
Edge-control and surface-smoothness in sub-aperture polishing of mirror segments
This paper addresses two challenges in establishing a new process chain for polishing hexagonal segments for extremely large telescopes:- i) control of edge and corner profiles in small-tool polishing of hexagons, and ii) achieving the required smoothness of the bulk aspheric form. We briefly describe the performance of a CNC-grinding process used to create the off-axis asphere, which established the input-quality for subsequent processing. We then summarize processes for smoothing ground mid-spatials and pre- and corrective polishing using Zeeko CNC machines. The impact of two cases is considered; i) all processing stages are performed after the segment is cut hexagonal, and ii) final rectification of a hexagon after cutting from an aspherised roundel, as an alternative to ionfiguring. We then report on experimental results on witness samples demonstrating edges and corners close to the EELT segment specification, and results on a full-aperture spherical segment showing excellent surface smoothness. © 2012 SPIE
A spectroscopic survey of thick disc stars outside the solar neighbourhood
We performed a spectroscopic survey of nearly 700 stars probing the galactic
thick disc far from the solar neighbourhood towards the galactic coordinates
(l~277, b~47). The derived effective temperatures, surface gravities and
overall metallicities were then combined with stellar evolution isochrones,
radial velocities and proper motions to derive the distances, kinematics and
orbital parameters of the sample stars. The targets belonging to each galactic
component (thin disc, thick disc, halo) were selected either on their
kinematics or according to their position above the galactic plane, and the
vertical gradients were also estimated. We present here atmospheric parameters,
distances and kinematics for this sample, and a comparison of our kinematic and
metallicity distributions with the Besancon model of the Milky Way. The thick
disc far from the solar neighbourhood is found to differ only slightly from the
thick disc properties as derived in the solar vicinity. For regions where the
thick disc dominates, we measured vertical velocity and metallicity trends of
d(V_phi)/dZ = 19 +/- 8 km/s/kpc and d[M/H]/dZ = -0.14 +/- 0.05 dex/kpc,
respectively. These trends can be explained as a smooth transition between the
different galactic components, although intrinsic gradients could not be
excluded. In addition, a correlation d(V_phi)/d[M/H] = -45 +/- 12 km/s/dex
between the orbital velocity and the metallicity of the thick disc is detected.
This gradient is inconsistent with the SDSS photometric survey analysis, which
did not detect any such trend, and challenges radial migration models of thick
disc formation. Estimations of the scale heights and scale lengths for
different metallicity bins of the thick disc result in consistent values, with
hR~3.4 \pm 0.7 kpc, and hZ~694 \pm 45 pc, showing no evidence of relics of
destroyed massive satellites.Comment: 19 pages, 15 figures, accepted for publication in A&
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