1,393 research outputs found
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
Diffusion and transport in the human interphase cell nucleus - FCS experiments compared to simulations.
Despite the succesful linear sequencing of the human genome the three-dimensional arrangement of chromatin,
functional, and structural components is still largely unknown. Molecular transport and diffusion are important
for processes like gene regulation, replication, or repair and are vitally influenced by the structure. With a
comparison between fluorescence correlation spectroscopy (FCS) experiments and simulations we show here an
interdisciplinary approach for the understanding of transport and diffusion properties in the human interphase
cell nucleus.
For a long time the interphase nucleus has been viewed as a 'spaghetti soup' of DNA without much internal
structure, except during cell division. Only recently has it become apparent that chromosomes occupy distinct
'territories' also in interphase. Two models for the detailed folding of the 30 nm chromatin fibre within these
territories are under debate: In the Random-Walk/Giant-Loop-model big loops of 3 to 5 Mbp are attached to a
non-DNA backbone. In the Multi-Loop-Subcompartment (MLS) model loops of around 120 kbp are forming
rosettes which are also interconnected by the chromatin fibre. Here we show with a comparison between
simulations and experiments an interdisciplinary approach leading to a determination of the three-dimensional
organization of the human genome: For the predictions of experiments various models of human interphase
chromosomes and the whole cell nucleus were simulated with Monte Carlo and Brownian Dynamics methods.
Only the MLS-model leads to the formation of non-overlapping chromosome territories and distinct functional
and dynamic subcompartments in agreement with experiments. Fluorescence in situ hybridization is used for the
specific marking of chromosome arms and pairs of small chromosomal DNA regions. The labelling is visualized
with confocal laser scanning microscopy followed by image reconstruction procedures. Chromosome arms show
only small overlap and globular substructures as predicted by the MLS-model. The spatial distances between
pairs of genomic markers as function of their genomic separation result in a MLS-model with loop and linker
sizes around 126 kbp. With the development of GFP-fusion-proteins it is possible to study the chromatin
distribution and dynamics resulting from cell cycle, treatment by chemicals or radiation in vivo. The chromatin
distributions are similar to those found in the simulation of whole cell nuclei of the MLS-model. Fractal analysis
is especially suited to quantify the unordered and non-euclidean chromatin distribution of the nucleus. The
dynamic behaviour of the chromatin structure and the diffusion of particles in the nucleus are also closely
connected to the fractal dimension. Fractal analysis of the simulations reveal the multi-fractality of
chromosomes. First fractal analysis of chromatin distributions in vivo result in significant differences for
different morphologies and might favour a MLS-model-like chromatin distribution. Simulations of fragment
distributions based on double strand breakage after carbon-ion irradiation differ in different models. Here again a
comparison with experiments favours a MLS-model.
FCS in combination with a scanning device is a suitable tool to study the diffusion characteristics of fluorescent
proteins in living cell nuclei with high spatial resolution. Computer simulations of the three-dimensional
organization of the human interphase nucleus allows a detailed test of theoretical models in comparison to
experiments. Diffusion and transport in the nucleus are most appropriately described with the concept of
obstructed diffusion. A large volume fraction of the nucleus seems to contain a cytosol-like liquid with an
apparent viscosity 5 times higher than in water. The geometry of particles and structure as well as their
interactions influence the mobilities in terms of speed and spatial coverage. A considerable amount of genomic
sites is accessible for not too large particles. FCS experiments and simulations based on the polymer model are
in a good agreement. Using recently developed in vivo chromatin markers, a detailed study of mobility vs.
structure is subject of current work
Functional MRI Readouts From BOLD and Diffusion Measurements Differentially Respond to Optogenetic Activation and Tissue Heating
Functional blood-oxygenation-level-dependent (BOLD) MRI provides a brain-wide readout that depends on the hemodynamic response to neuronal activity. Diffusion fMRI has been proposed as an alternative to BOLD fMRI and has been postulated to directly rely on neuronal activity. These complementary functional readouts are versatile tools to be combined with optogenetic stimulation to investigate networks of the brain. The cell-specificity and temporal precision of optogenetic manipulations promise to enable further investigation of the origin of fMRI signals. The signal characteristics of the diffusion fMRI readout vice versa may better resolve network effects of optogenetic stimulation. However, the light application needed for optogenetic stimulation is accompanied by heat deposition within the tissue. As both diffusion and BOLD are sensitive to temperature changes, light application can lead to apparent activations confounding the interpretation of fMRI data. The degree of tissue heating, the appearance of apparent activation in different fMRI sequences and the origin of these phenomena are not well understood. Here, we disentangled apparent activations in BOLD and diffusion measurements in rats from physiological activation upon sensory or optogenetic stimulation. Both, BOLD and diffusion fMRI revealed similar signal shapes upon sensory stimulation that differed clearly from those upon heating. Apparent activations induced by high-intensity light application were dominated by T2â-effects and resulted in mainly negative signal changes. We estimated that even low-intensity light application used for optogenetic stimulation reduces the BOLD response close to the fiber by up to 0.4%. The diffusion fMRI signal contained T2, T2â and diffusion components. The apparent diffusion coefficient, which reflects the isolated diffusion component, showed negative changes upon both optogenetic and electric forepaw stimulation. In contrast, positive changes were detected upon high-intensity light application and thus ruled out heating as a major contributor to the diffusion fMRI signal
Using standard typing algorithms incrementally
Modern languages are equipped with static type checking/inference that helps programmers to keep a clean programming style and to reduce errors. However, the ever-growing size of programs and their continuous evolution require building fast and efficient analysers. A promising solution is incrementality, aiming at only re-typing the diffs, i.e. those parts of the program that change or are inserted, rather than the entire codebase. We propose an algorithmic schema that drives an incremental usage of existing, standard typing algorithms with no changes. Ours is a grey-box approach: just the shape of the input, that of the results and some domain-specific knowledge are needed to instantiate our schema. Here, we present the foundations of our approach and the conditions for its correctmess. We show it at work to derive two different incremental typing algorithms. The first type checks an imperative language to detect information flow and non-interference, and the second infers types for a functional language. We assessed our proposal on a prototypical imple- mentation of an incremental type checker. Our experiments show that using the type checker incrementally is (almost) always rewardin
Using Standard Typing Algorithms Incrementally
Modern languages are equipped with static type checking/inference that helps
programmers to keep a clean programming style and to reduce errors. However,
the ever-growing size of programs and their continuous evolution require
building fast and efficient analysers. A promising solution is incrementality,
so one only re-types those parts of the program that are new, rather than the
entire codebase. We propose an algorithmic schema driving the definition of an
incremental typing algorithm that exploits the existing, standard ones with no
changes. Ours is a grey-box approach, meaning that just the shape of the input,
that of the results and some domain-specific knowledge are needed to
instantiate our schema. Here, we present the foundations of our approach and we
show it at work to derive three different incremental typing algorithms. The
first two implement type checking and inference for a functional language. The
last one type-checks an imperative language to detect information flow and
non-interference. We assessed our proposal on a prototypical implementation of
an incremental type checker. Our experiments show that using the type checker
incrementally is (almost) always rewarding.Comment: corrected and updated; experimental results adde
PT-symmetric models in curved manifolds
We consider the Laplace-Beltrami operator in tubular neighbourhoods of curves
on two-dimensional Riemannian manifolds, subject to non-Hermitian parity and
time preserving boundary conditions. We are interested in the interplay between
the geometry and spectrum. After introducing a suitable Hilbert space framework
in the general situation, which enables us to realize the Laplace-Beltrami
operator as an m-sectorial operator, we focus on solvable models defined on
manifolds of constant curvature. In some situations, notably for non-Hermitian
Robin-type boundary conditions, we are able to prove either the reality of the
spectrum or the existence of complex conjugate pairs of eigenvalues, and
establish similarity of the non-Hermitian m-sectorial operators to normal or
self-adjoint operators. The study is illustrated by numerical computations.Comment: 37 pages, PDFLaTeX with 11 figure
From neighbourhood to 'globalhood'? Three propositions on the rapid rise of short-term rentals
This Commentary is an attempt to understand the recent, rapid rise of shortâterm property rentals in some of the world's most popular neighbourhoods, and what it means for communities, whether urban or rural. The literature to date has tackled the issue from a number of different perspectives, but there is no clear consensus on what the key issues are within this sector of the soâcalled âsharing economy.â Despite claims to the contrary, I argue that there is something new about this phenomenon, in relation to its growth, intensity and spatial concentration. I also argue that it represents a kind of double disruption, and that home sharing can usefully be conceptualised as neighbourhood sharing if we want to arrive at a better understanding of local reactions to it, and how we might best respond to it from a regulatory point of view
Spectrum and Charge Ratio of Vertical Cosmic Ray Muons up to Momenta of 2.5 TeV/c
The ALEPH detector at LEP has been used to measure the momentum spectrum and charge ratio of vertical cosmic ray muons underground. The sea-level cosmic ray muon spectrum for momenta up to 2.5 TeV/c has been obtained by correcting for the overburden of 320 meter water equivalent (mwe). The results are compared with Monte Carlo models for air shower development in the atmosphere. From the analysis of the spectrum the total flux and the spectral index of the cosmic ray primaries is inferred. The charge ratio suggests a dominantly light composition of cosmic ray primaries with energies up to 10^15 eV
The sleep of elite athletes at sea level and high altitude: A comparison of sea-level natives and high-altitude natives (ISA3600)
Background Altitude exposure causes acute sleep disruption in non-athletes, but little is known about its effects in elite athletes. The aim of this study was to examine the effects of altitude on two groups of elite athletes, that is, sea-level natives and high-altitude natives. Methods Sea-level natives were members of the Australian under-17 soccer team (n=14). High-altitude natives were members of a Bolivian under-20 club team (n=12). Teams participated in an 18-day (19 nights) training camp in Bolivia, with 6 nights at near sea level in Santa Cruz (430 m) and 13 nights at high altitude in La Paz (3600 m). Sleep was assessed on every day/night using activity monitors. Results The Australiansâ sleep was shorter, and of poorer quality, on the first night at altitude compared with sea level. Sleep quality returned to normal by the end of the first week at altitude, but sleep quantity had still not stabilised at its normal level after 2 weeks. The quantity and quality of sleep obtained by the Bolivians was similar, or greater, on all nights at altitude compared with sea level. The Australians tended to obtain more sleep than the Bolivians at sea level and altitude, but the quality of the Boliviansâ sleep tended to be better than that of the Australians at altitude. Conclusions Exposure to high altitude causes acute and chronic disruption to the sleep of elite athletes who are sea-level natives, but it does not affect the sleep of elite athletes who are high-altitude natives
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