2,936 research outputs found
A comparative evaluation of interest point detectors and local descriptors for visual SLAM
Abstract In this paper we compare the behavior of different interest points detectors and descriptors under the
conditions needed to be used as landmarks in vision-based simultaneous localization and mapping (SLAM).
We evaluate the repeatability of the detectors, as well as the invariance and distinctiveness of the descriptors,
under different perceptual conditions using sequences of images representing planar objects as well as 3D scenes.
We believe that this information will be useful when selecting an appropriat
An integrated probabilistic framework for robot perception, learning and memory
Learning and perception from multiple sensory modalities are crucial processes for the development of intelligent systems capable of interacting with humans. We present an integrated probabilistic framework for perception, learning and memory in robotics. The core component of our framework is a computational Synthetic Autobiographical Memory model which uses Gaussian Processes as a foundation and mimics the functionalities of human memory. Our memory model, that operates via a principled Bayesian probabilistic framework, is capable of receiving and integrating data flows from multiple sensory modalities, which are combined to improve perception and understanding of the surrounding environment. To validate the model, we implemented our framework in the iCub humanoid robotic, which was able to learn and recognise human faces, arm movements and touch gestures through interaction with people. Results demonstrate the flexibility of our method to successfully integrate multiple sensory inputs, for accurate learning and recognition. Thus, our integrated probabilistic framework offers a promising core technology for robust intelligent systems, which are able to perceive, learn and interact with people and their environments
Characterizing Changes in a Salt Hydrate Bed Using Micro X-Ray Computed Tomography
Thermochemical storage using salt hydrates presents a promising energy storage method. Ensuring the long-term effectiveness of the system is critical, demanding both chemical and mechanical stability of material for repetitive cycling. Challenges arise from agglomeration and volume variations during discharging and charging, impacting the cyclability of thermochemical materials (TCM). For practical usage, the material is often used in a packed bed containing millimetre-sized grains. A micro-level analysis of changes in a packed bed system, along with a deeper understanding involving quantifying bed characteristics, is crucial. In this study, micro X-ray computed tomography (XCT) is used to compare changes in the packed bed before and after cycling the material. Findings indicate a significant decrease in pore size distribution in the bed after 10 cycles and a decrease in porosity from 41.34 to 19.91% accompanied by an increase in grain size, reducing void space. A comparison of effective thermal conductivity between the uncycled and cycled reactor indicates an increase after cycling. Additionally, the effective thermal conductivity is lower in the axial direction compared to the radial. XCT data from uncycled and cycled experiments are further used to observe percolation paths inside the bed. Furthermore, at a system scale fluid flow profile comparison is presented for uncycled and cycled packed beds. It has been observed that the permeability decreased and the pressure drop increased from 0.31 to 4.88Â Pa after cycling.</p
Orbital Polarons in the Metal-Insulator Transition of Manganites
The metal-insulator transition in manganites is strongly influenced by the
concentration of holes present in the system. Based upon an orbitally
degenerate Mott-Hubbard model we analyze two possible localization scenarios to
account for this doping dependence: First, we rule out that the transition is
initiated by a disorder-order crossover in the orbital sector, showing that its
effect on charge mobility is only small. Second, we introduce the idea of
orbital polarons originating from a strong polarization of orbitals in the
vicinity of holes. Considering this direct coupling between charge and orbital
degree of freedom in addition to lattice effects we are able to explain well
the phase diagram of manganites for low and intermediate hole concentrations
Structural models of the different trimers present in the core of phycobilisomes from <i>Gracilaria chilensis</i> based on crystal structures and sequences
Phycobilisomes (PBS) are accessory light harvesting protein complexes that directionally transfer energy towards photosystems. Phycobilisomes are organized in a central core and rods radiating from it. Components of phycobilisomes in Gracilaria chilensis (Gch) are Phycobiliproteins (PBPs), Phycoerythrin (PE), and Phycocyanin (PC) in the rods, while Allophycocyanin (APC) is found in the core, and linker proteins (L). The function of such complexes depends on the structure of each component and their interaction. The core of PBS from cyanobacteria is mainly composed by cylinders of trimers of α and β subunits forming heterodimers of Allophycocyanin, and other components of the core including subunits αII and β18. As for the linkers, Linker core (LC) and Linker core membrane (LCM) are essential for the final emission towards photoreaction centers. Since we have previously focused our studies on the rods of the PBS, in the present article we investigated the components of the core in the phycobilisome from the eukaryotic algae, Gracilaria chilensis and their organization into trimers. Transmission electron microscopy provided the information for a three cylinders core, while the three dimensional structure of Allophycocyanin purified from Gch was determined by X-ray diffraction method and the biological unit was determined as a trimer by size exclusion chromatography. The protein sequences of all the components of the core were obtained by sequencing the corresponding genes and their expression confirmed by transcriptomic analysis. These subunits have seldom been reported in red algae, but not in Gracilaria chilensis. The subunits not present in the crystallographic structure were modeled to build the different composition of trimers. This article proposes structural models for the different types of trimers present in the core of phycobilisomes of Gch as a first step towards the final model for energy transfer in this system
Pilot3 D1.1 - Technical resources and problem definition
This deliverable starts with the proposal of Pilot3 but incorporates the development produced during the first four months of the project: activities on different workpackages, interaction with Topic Manager and Project Officer, and input received during the first Advisory Board meeting.
This deliverable presents the definition of Pilot3 concept and methodology. It includes the high level the requirements of the prototype, preliminary data requirements, preliminary indicators that will be considered and a preliminary definition of case studies.
The deliverable aims at defining the view of the consortium on the project at these early stages, while highlighting the feedback obtained from the Advisory Board and the further activities required to define some of the aspects of the project
Susceptibility and dilution effects of the kagome bi-layer geometrically frustrated network. A Ga-NMR study of SrCr_(9p)Ga_(12-9p)O_(19)
We present an extensive gallium NMR study of the geometrically frustrated
kagome bi-layer compound SrCr_(9p)Ga_(12-9p)O_(19) (Cr^3+, S=3/2) over a broad
Cr-concentration range (.72<p<.95). This allows us to probe locally the kagome
bi-layer susceptibility and separate the intrinsic properties due to the
geometric frustration from those related to the site dilution. Our major
findings are: 1) The intrinsic kagome bi-layer susceptibility exhibits a
maximum in temperature at 40-50 K and is robust to a dilution as high as ~20%.
The maximum reveals the development of short range antiferromagnetic
correlations; 2) At low-T, a highly dynamical state induces a strong wipe-out
of the NMR intensity, regardless of dilution; 3) The low-T upturn observed in
the macroscopic susceptibility is associated to paramagnetic defects which stem
from the dilution of the kagome bi-layer. The low-T analysis of the NMR
lineshape suggests that the defect can be associated with a staggered
spin-response to the vacancies on the kagome bi-layer. This, altogether with
the maximum in the kagome bi-layer susceptibility, is very similar to what is
observed in most low-dimensional antiferromagnetic correlated systems; 4) The
spin glass-like freezing observed at T_g=2-4 K is not driven by the
dilution-induced defects.Comment: 19 pages, 19 figures, revised version resubmitted to PRB Minor
modifications: Fig.11 and discussion in Sec.V on the NMR shif
The dark side of curvature
Geometrical tests such as the combination of the Hubble parameter H(z) and
the angular diameter distance d_A(z) can, in principle, break the degeneracy
between the dark energy equation of state parameter w(z), and the spatial
curvature Omega_k in a direct, model-independent way. In practice, constraints
on these quantities achievable from realistic experiments, such as those to be
provided by Baryon Acoustic Oscillation (BAO) galaxy surveys in combination
with CMB data, can resolve the cosmic confusion between the dark energy
equation of state parameter and curvature only statistically and within a
parameterized model for w(z). Combining measurements of both H(z) and d_A(z) up
to sufficiently high redshifts around z = 2 and employing a parameterization of
the redshift evolution of the dark energy equation of state are the keys to
resolve the w(z)-Omega_k degeneracy.Comment: 18 pages, 9 figures. Minor changes, matches version accepted in JCA
Workshop on immunotherapy combinations. Society for immunotherapy of cancer annual meeting Bethesda, November 3, 2011
Although recent FDA approvals on ipilimumab and sipuleucel-T represent major milestones, the ultimate success of immunotherapy approaches will likely benefit from appropriate combinations with other immunotherapeutic and/or non-immunotherapeutic approaches. However, implementation of ideal combinations in the clinic may still face formidable challenges in regulatory, drug-availability and intellectual property aspects. The 2011 SITC annual meeting hosted a workshop on combination immunotherapy to discuss: 1) the most promising combinations found in the laboratory; 2) early success of combination immunotherapy in clinical trials; 3) industry perspectives on combination approaches, and 4) relevant regulatory issues. The integrated theme was how to accelerate the implementation of efficacious combined immunotherapies for cancer patients. Rodent animal models are providing many examples of synergistic combinations that typically include more than two agents. However, mouse and human immunology differ in a significant number of mechanisms and hence we might be missing opportunities peculiar to humans. Nonetheless, incisive animal experimentation with deep mechanistic insight remains the best compass that we can use to guide our paths in combinatorial immunotherapy. Combination immunotherapy clinical trials are already in progress and preliminary results are extremely promising. As a key to translate promising combinations into clinic, real and “perceived” business and regulatory hurdles were debated. A formidable step forward would be to be able to test combinations of investigational agents prior to individual approval. Taking together the FDA and the industrial perspective on combinatorial immunotherapy, the audience was left with the clear message that this is by no means an impossible task. The general perception is that the road ahead of us is full of combination clinical trials which hopefully will bring clinical benefit to our cancer patients at a fast pace
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