6,202 research outputs found
Improved image quality with new ultrasound imaging techniques
AbstractThis work addresses three key subjects to the image quality with phased arrays: timing accuracy, beamforming strategy and post-processing for increased resolution and suppression of grating and side lobes.Timing accuracy is achieved by defining a modular and scalable architecture which guarantees timing errors of a few tens of picoseconds, whatever is the system size. The proposed beamforming methodology follows the progressive focusing correction technique, which keeps low focusing errors, provides a high information density and has a simple implementation for real-time imaging. Then, phase coherence imaging is defined to suppress grating and sidelobe indications and increasing the lateral resolution
Multi-Modal Human-Machine Communication for Instructing Robot Grasping Tasks
A major challenge for the realization of intelligent robots is to supply them
with cognitive abilities in order to allow ordinary users to program them
easily and intuitively. One way of such programming is teaching work tasks by
interactive demonstration. To make this effective and convenient for the user,
the machine must be capable to establish a common focus of attention and be
able to use and integrate spoken instructions, visual perceptions, and
non-verbal clues like gestural commands. We report progress in building a
hybrid architecture that combines statistical methods, neural networks, and
finite state machines into an integrated system for instructing grasping tasks
by man-machine interaction. The system combines the GRAVIS-robot for visual
attention and gestural instruction with an intelligent interface for speech
recognition and linguistic interpretation, and an modality fusion module to
allow multi-modal task-oriented man-machine communication with respect to
dextrous robot manipulation of objects.Comment: 7 pages, 8 figure
Environmental Dependence of the Fundamental Plane of Galaxy Clusters
Galaxy clusters approximate a planar (FP) distribution in a three-dimensional
parameter space which can be characterized by optical luminosity, half-light
radius, and X-ray luminosity. Using a high-quality catalog of cluster
redshifts, we find the nearest neighbor cluster for those common to an FP study
and the cluster catalog. Examining scatter about the FP, we find 99.2%
confidence that it is dependent on nearest neighbor distance. Our study of
X-Ray clusters finds that those with high central gas densities are
systematically closer to neighbor clusters. If we combine results here with
those of Fritsch and Buchert, we find an explanation for some of our previous
conclusions: Clusters in close proximity to other clusters are more likely to
have massive cooling flows because they are more relaxed and have higher
central gas densities.Comment: Accepted for publication in Astrophysical Journal Letters. Moderate
revisions, including more statistical analysis and discussion. Latex, 7 page
Optimum porphyrin accumulation in epithelial skin tumours and psoriatic lesions after topical application of δ-aminolaevulinic acid
Photodynamic therapy with topically applied δ-aminolaevulinic acid is used to treat skin tumours by employing endogenously formed porphyrins as photosensitizers. This study examines the time course of porphyrin metabolite formation after topical application of δ-aminolaevulinic acid. Porphyrin biosynthesis in human skin tumours (basal cell carcinoma, squamous cell carcinoma), in psoriatic lesions, and in normal skin was investigated. Skin areas were treated with δ-aminolaevulinic acid, and levels of total porphyrins, porphyrin metabolites and proteins were measured in samples excised after 1, 2, 4, 6, 9, 12 and 24 h. There was an increase in porphyrin biosynthesis in all tissues with maximum porphyrin levels in tumours between 2 and 6 h and in psoriatic lesions 6 h after treatment. The pattern of porphyrins showed no significant difference between normal and neoplastic skin, protoporphyrin being the predominant metabolite. The results suggest that optimum irradiation time for superficial epithelial skin tumours may be as soon as 2 h after application of δ-aminolaevulinic acid, whereas for treatment of psoriatic lesions an application time of 6 h is more suitable. © 1999 Cancer Research Campaig
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