950 research outputs found
Customising games for non-formal rehabilitation
The field of rehabilitation has increasingly adopted commercially available games using perceptual interfaces as a means for physically training patients. The adaptability of such systems to match each person’s need and rehabilitation goal remains problematic. This paper presents a rapid prototyping approach for customising gaming technology using various affordable commercial devices and open source software. We first demonstrate how a freely available game is adapted for training disabled people through different sensors and control modes. We then show how an open online virtual world such as Second Life® offers sufficient conditions for quickly building custom content for testing with interactive devices. When presented with these prototyping possibilities, people from the target groups (healthcare professionals, patients, people with disabilities, older people, families) related such systems to their needs and further elaborated on the use of such systems. Our research indicates how availability of simple prototyping platforms expands upon the possibilities for developers and practitioners
The NNLO non-singlet QCD analysis of parton distributions based on Bernstein polynomials
A non-singlet QCD analysis of the structure function up to NNLO is
performed based on the Bernstein polynomials approach. We use recently
calculated NNLO anomalous dimension coefficients for the moments of the
structure function in scattering. In the fitting procedure, Bernstein
polynomial method is used to construct experimental moments from the
data of the CCFR collaboration in the region of which is inaccessible
experimentally. We also consider Bernstein averages to obtain some unknown
parameters which exist in the valence quark densities in a wide range of
and . The results of valence quark distributions up to NNLO are in good
agreement with the available theoretical models. In the analysis we determined
the QCD-scale MeV (LO), 259 MeV (NLO)
and 230 MeV (NNLO), corresponding to LO,
NLO and NNLO. We compare our
results for the QCD scale and the with those obtained from
deep inelastic scattering processes.Comment: 20 pages, 7 figures, published in JHE
Open-Ended Evolutionary Robotics: an Information Theoretic Approach
This paper is concerned with designing self-driven fitness functions for
Embedded Evolutionary Robotics. The proposed approach considers the entropy of
the sensori-motor stream generated by the robot controller. This entropy is
computed using unsupervised learning; its maximization, achieved by an on-board
evolutionary algorithm, implements a "curiosity instinct", favouring
controllers visiting many diverse sensori-motor states (sms). Further, the set
of sms discovered by an individual can be transmitted to its offspring, making
a cultural evolution mode possible. Cumulative entropy (computed from ancestors
and current individual visits to the sms) defines another self-driven fitness;
its optimization implements a "discovery instinct", as it favours controllers
visiting new or rare sensori-motor states. Empirical results on the benchmark
problems proposed by Lehman and Stanley (2008) comparatively demonstrate the
merits of the approach
Entanglement and entropy operator for strings in pp-wave time dependent background
In this letter new aspects of string theory propagating in a pp-wave time
dependent background with a null singularity are explored. It is shown the
appearance of a 2d entanglement entropy dynamically generated by the
background. For asymptotically flat observers, the vacuum close to the
singularity is unitarily inequivalent to the vacuum at and it
is shown that the 2d entanglement entropy diverges close to this point. As a
consequence, the positive time region is inaccessible for observers in . For a stationary measure, the vacuum at finite time is seen by those
observers as a thermal state and the information loss is encoded as a heat bath
of string states.Comment: revtex4, 15 pages, revised version to appear in Physics Letters
Observer dependent D-brane for strings propagating in pp-wave time dependent background
We study type IIB superstring in the pp-wave time-dependent background, which
has a singularity at . We show that this background can provide a toy
model to study some ideas related to the stretched horizon paradigm and the
complementary principle of black holes. To this end, we construct a unitary
Bogoliubov generator which relates the asymptotically flat string Hilbert
space, defined at , to the finite time Hilbert space. For
asymptotically flat observers, the closed string vacuum close to the
singularity appears as a boundary state which is in fact a D-brane described in
the closed string channel. However, observers who go with the string towards to
the singularity see the original vacuum.Comment: 12 pages, revtex 4, added references, corrected mistake
Identification of functionally distinct macrophage subpopulations in Drosophila
Vertebrate macrophages are a highly heterogeneous cell population, but while Drosophila blood is dominated by a macrophage-like lineage (plasmatocytes), until very recently these cells were considered to represent a homogeneous population. Here, we present our identification of enhancer elements labelling plasmatocyte subpopulations, which vary in abundance across development. These subpopulations exhibit functional differences compared to the overall population, including more potent injury responses and differential localisation and dynamics in pupae and adults. Our enhancer analysis identified candidate genes regulating plasmatocyte behaviour: pan-plasmatocyte expression of one such gene (Calnexin14D) improves wound responses, causing the overall population to resemble more closely the subpopulation marked by the Calnexin14D-associated enhancer. Finally, we show that exposure to increased levels of apoptotic cell death modulates subpopulation cell numbers. Taken together this demonstrates macrophage heterogeneity in Drosophila, identifies mechanisms involved in subpopulation specification and function and facilitates the use of Drosophila to study macrophage heterogeneity in vivo
High frequency resonant experiments in Fe molecular clusters
Precise resonant experiments on Fe magnetic clusters have been
conducted down to 1.2 K at various tranverse magnetic fields, using a
cylindrical resonator cavity with 40 different frequencies between 37 GHz and
110 GHz. All the observed resonances for both single crystal and oriented
powder, have been fitted by the eigenstates of the hamiltonian . We have identified the
resonances corresponding to the coherent quantum oscillations for different
orientations of spin S = 10.Comment: to appear in Phys.Rev. B (August 2000
Epistemic and social scripts in computer-supported collaborative learning
Collaborative learning in computer-supported learning environments typically means that learners work on tasks together, discussing their individual perspectives via text-based media or videoconferencing, and consequently acquire knowledge. Collaborative learning, however, is often sub-optimal with respect to how learners work on the concepts that are supposed to be learned and how learners interact with each other. One possibility to improve collaborative learning environments is to conceptualize epistemic scripts, which specify how learners work on a given task, and social scripts, which structure how learners interact with each other. In this contribution, two studies will be reported that investigated the effects of epistemic and social scripts in a text-based computer-supported learning environment and in a videoconferencing learning environment in order to foster the individual acquisition of knowledge. In each study the factors ‘epistemic script’ and ‘social script’ have been independently varied in a 2×2-factorial design. 182 university students of Educational Science participated in these two studies. Results of both studies show that social scripts can be substantially beneficial with respect to the individual acquisition of knowledge, whereas epistemic scripts apparently do not to lead to the expected effects
Hydrophobic and ionic-interactions in bulk and confined water with implications for collapse and folding of proteins
Water and water-mediated interactions determine thermodynamic and kinetics of
protein folding, protein aggregation and self-assembly in confined spaces. To
obtain insights into the role of water in the context of folding problems, we
describe computer simulations of a few related model systems. The dynamics of
collapse of eicosane shows that upon expulsion of water the linear hydrocarbon
chain adopts an ordered helical hairpin structure with 1.5 turns. The structure
of dimer of eicosane molecules has two well ordered helical hairpins that are
stacked perpendicular to each other. As a prelude to studying folding in
confined spaces we used simulations to understand changes in hydrophobic and
ionic interactions in nano droplets. Solvation of hydrophobic and charged
species change drastically in nano water droplets. Hydrophobic species are
localized at the boundary. The tendency of ions to be at the boundary where
water density is low increases as the charge density decreases. Interaction
between hydrophobic, polar, and charged residue are also profoundly altered in
confined spaces. Using the results of computer simulations and accounting for
loss of chain entropy upon confinement we argue and then demonstrate, using
simulations in explicit water, that ordered states of generic amphiphilic
peptide sequences should be stabilized in cylindrical nanopores
Semiconductive and Photoconductive Properties of the Single Molecule Magnets Mn-Acetate and FeBr
Resistivity measurements are reported for single crystals of
Mn-Acetate and FeBr. Both materials exhibit a
semiconductor-like, thermally activated behavior over the 200-300 K range. The
activation energy, , obtained for Mn-Acetate was 0.37 0.05
eV, which is to be contrasted with the value of 0.55 eV deduced from the
earlier reported absorption edge measurements and the range of 0.3-1 eV from
intramolecular density of states calculations, assuming = , the
optical band gap. For FeBr, was measured as 0.73 0.1 eV,
and is discussed in light of the available approximate band structure
calculations. Some plausible pathways are indicated based on the crystal
structures of both lattices. For Mn-Acetate, we also measured
photoconductivity in the visible range; the conductivity increased by a factor
of about eight on increasing the photon energy from 632.8 nm (red) to 488 nm
(blue). X-ray irradiation increased the resistivity, but was insensitive
to exposure.Comment: 7 pages, 8 figure
- …