967 research outputs found
Controlled Natural Language Generation from a Multilingual FrameNet-based Grammar
This paper presents a currently bilingual but potentially multilingual
FrameNet-based grammar library implemented in Grammatical Framework. The
contribution of this paper is two-fold. First, it offers a methodological
approach to automatically generate the grammar based on semantico-syntactic
valence patterns extracted from FrameNet-annotated corpora. Second, it provides
a proof of concept for two use cases illustrating how the acquired multilingual
grammar can be exploited in different CNL applications in the domains of arts
and tourism
Full regularity for a C*-algebra of the Canonical Commutation Relations. (Erratum added)
The Weyl algebra,- the usual C*-algebra employed to model the canonical
commutation relations (CCRs), has a well-known defect in that it has a large
number of representations which are not regular and these cannot model physical
fields. Here, we construct explicitly a C*-algebra which can reproduce the CCRs
of a countably dimensional symplectic space (S,B) and such that its
representation set is exactly the full set of regular representations of the
CCRs. This construction uses Blackadar's version of infinite tensor products of
nonunital C*-algebras, and it produces a "host algebra" (i.e. a generalised
group algebra, explained below) for the \sigma-representation theory of the
abelian group S where \sigma(.,.):=e^{iB(.,.)/2}.
As an easy application, it then follows that for every regular representation
of the Weyl algebra of (S,B) on a separable Hilbert space, there is a direct
integral decomposition of it into irreducible regular representations (a known
result).
An Erratum for this paper is added at the end.Comment: An erratum was added to the original pape
Gravitational Lensing by Dark Matter Caustics
Dark matter caustics have specific density profiles and, therefore, precisely
calculable gravitational lensing properties. We present a formalism which
simplifies the relevant calculations, and apply it to four specific cases. In
the first three, the line of sight is tangent to a smooth caustic surface. The
curvature of the surface at the tangent point is positive, negative or zero. In
the fourth case the line of sight passes near a cusp. For each we derive the
map between the image and source planes. In some cases, a point source has
multiple images and experiences infinite magnification when the images merge.
Unfortunately, for the dark matter caustics expected in realistic galactic halo
models, the angular resolution required to resolve the multiple images is not
presently achievable. A more promising approach aims to observe the distortions
caused by dark matter caustics in the images of extended sources such as radio
jets.Comment: 36 pages, 11 figure
Non-radial motion and the NFW profile
The self-similar infall model (SSIM) is normally discussed in the context of
radial orbits in spherical symmetry. However it is possible to retain the
spherical symmetry while permitting the particles to move in Keplerian
ellipses, each having the squared angular momentum peculiar to their 'shell'.
The spherical 'shell', defined for example by the particles turning at a given
radius, then moves according to the radial equation of motion of a 'shell'
particle. The 'shell' itself has no physical existence except as an ensemble of
particles, but it is convenient to sometimes refer to the shells since it is
they that are followed by a shell code. In this note we find the distribution
of squared angular momentum as a function of radius that yields the NFW density
profile for the final dark matter halo. It transpires that this distribution is
amply motivated dimensionally. An effective 'lambda' spin parameter is roughly
constant over the shells. We also study the effects of angular momentum on the
relaxation of a dark matter system using a three dimensional representation of
the relaxed phase space.Comment: accepted for publication in Astronomy and Astrophysics. date
received: 31-03-03 date accepted: 10-06-0
Alcohol-induced retrograde facilitation renders witnesses of crime less suggestible to misinformation
RATIONALE: Research has shown that alcohol can have both detrimental and facilitating effects on memory: intoxication can lead to poor memory for information encoded after alcohol consumption (anterograde amnesia) and may improve memory for information encoded before consumption (retrograde facilitation). This study examined whether alcohol consumed after witnessing a crime can render individuals less vulnerable to misleading post-event information (misinformation). METHOD: Participants watched a simulated crime video. Thereafter, one third of participants expected and received alcohol (alcohol group), one third did not expect but received alcohol (reverse placebo), and one third did not expect nor receive alcohol (control). After alcohol consumption, participants were exposed to misinformation embedded in a written narrative about the crime. The following day, participants completed a cued-recall questionnaire about the event. RESULTS: Control participants were more likely to report misinformation compared to the alcohol and reverse placebo group. CONCLUSION: The findings suggest that we may oversimplify the effect alcohol has on suggestibility and that sometimes alcohol can have beneficial effects on eyewitness memory by protecting against misleading post-event information
Differential regulation of ENA-78 and GCP-2 gene expression in human corneal keratocytes and epithelial
PURPOSE. To determine whether interleukin (IL)-1␣-and tumor necrosis factor (TNF)-␣-stimulated human corneal epithelial cells (HCECs) and human corneal keratocytes (HCKs) produce the ␣-chemokines epithelial cell-derived neutrophil attractant (ENA)-78 and granulocyte chemotactic protein (GCP)-2. METHODS. Cultures of HCECs and HCKs were stimulated with either human recombinant IL-1␣ or TNF-␣. At selected times after stimulation, culture supernatants were harvested and assayed for ENA-78 and GCP-2 by enzyme-linked immunosorbent assay. RNA was extracted from cell cultures to measure steady state levels of intracellular ENA-78 and GCP-2 pre-mRNA and mRNA by the reverse transcription-polymerase chain reaction. RESULTS. Exposure of HCECs to either IL-1␣ or TNF-␣ stimulated a more than 4.5-fold increase in ENA-78 RNA and protein synthesis without stimulating a significant increase in either GCP-2 RNA synthesis or protein production. Exposure of HCK to IL-1␣ stimulated a 10-fold increase in ENA-78 and GCP-2 RNA synthesis and a more than 300-fold increase in ENA-78 and GCP-2 protein production. In contrast, exposure of keratocytes to TNF-␣ significantly enhanced ENA-78 RNA synthesis, resulting in a more than 68-fold increase in ENA-78 protein synthesis without significantly enhancing either GCP-2 gene expression or protein secretion. CONCLUSIONS. ENA-78 gene expression is significantly enhanced in both HCECs and HCKs in response to either IL-1␣ or TNF-␣ stimulation. In contrast, GCP-2 synthesis is only inducible in IL-1␣-stimulated HCKs. The results suggest that GCP-2 gene expression is more tightly regulated in diseased or injured corneal tissue than is ENA-78 gene expression. (Invest Ophthalmol Vis Sci. 2003;44:3432-3437
Model independent analysis of dark matter points to a particle mass at the keV scale
We present a model independent analysis of dark matter (DM) both decoupling
ultra relativistic (UR) and non-relativistic (NR) based in the phase-space
density D = rho_{DM}/sigma^3_{DM}. We derive explicit formulas for the DM
particle mass m and for the number of ultra relativistic degrees of freedom g_d
at decoupling. We find that for DM particles decoupling UR both at local
thermal equilibrium (LTE) and out of LTE, m turns to be at the keV scale. For
example, for DM Majorana fermions decoupling at LTE the mass results m ~ 0.85
keV. For DM particles decoupling NR, sqrt{m T_d} results in the keV scale (T_d
is the decoupling temperature) and the m value is consistent with the keV
scale. In all cases, DM turns to be cold DM (CDM). Also, lower and upper bounds
on the DM annihilation cross-section for NR decoupling are derived. We evaluate
the free-streaming (Jeans') length and Jeans' mass: they result independent of
the type of DM except for the DM self-gravity dynamics. The free-streaming
length today results in the kpc range. These results are based on our
theoretical analysis, astronomical observations of dwarf spheroidal satellite
galaxies in the Milky Way and N-body numerical simulations. We analyze and
discuss the results on D from analytic approximate formulas both for linear
fluctuations and the (non-linear) spherical model and from N-body simulations
results. We obtain in this way upper bounds for the DM particle mass which all
result below the 100 keV range.Comment: 11 pages, 2 figures. Expanded version to be published in Monthly
Notices of the Royal Astronomical Societ
Black holes and Galactic density cusps -- I. Radial orbit cusps and bulges
In this paper, we study the distribution functions that arise naturally
during self-similar radial infall of collisionless matter. Such matter may be
thought of either as stars or as dark matter particles. If a rigorous steady
state is assumed, then the system is infinite and is described by a universal
distribution function given the self-similar index. The steady logarithmic
potential case is exceptional and yields the familiar Gaussian for an infinite
system with an inverse-square density profile. We show subsequently that for
time-dependent radial self-similar infall, the logarithmic case is accurately
described by the Fridmann and Polyachenko distribution function. The system in
this case is finite but growing. We are able to embed a central mass in the
universal steady distribution only by iteration, except in the case of massless
particles. The iteration yields logarithmic corrections to the massless
particle case and requires a `renormalization' of the central mass. A central
spherical mass may be accurately embedded in the Fridmann and Polyachenko
growing distribution however. Some speculation is given concerning the
importance of radial collisionless infall in actual galaxy formation.Comment: 10 pp, 3 fig
Testing the interaction of dark energy to dark matter through the analysis of virial relaxation of clusters Abell Clusters A586 and A1689 using realistic density profiles
Interaction between dark energy and dark matter is probed through deviation
from the virial equilibrium for two relaxed clusters: A586 and A1689. The
evaluation of the virial equilibrium is performed using realistic density
profiles. The virial ratios found for the more realistic density profiles are
consistent with the absence of interaction.Comment: 16pp 1 fig; accepted by GeR
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