525 research outputs found
An algorithm for the computation of posterior moments and densities using simple importance sampling
In earlier work (van Dijk, 1984, Chapter 3) one of the authors discussed the use of Monte Carlo integration methods for the computation of the multivariate integrals that are defined in the posterior moments and densities of the parameters of interest of econometric models. In the present paper we describe the computational steps of one Monte Carlo method, which is known in the literature as importance sampling. Further, a set of standard programs is available, which may be used for the implementation of a simple case of importance sampling. The computer programs have been written in FORTRAN 77
Response function analysis of excited-state kinetic energy functional constructed by splitting k-space
Over the past decade, fundamentals of time independent density functional
theory for excited state have been established. However, construction of the
corresponding energy functionals for excited states remains a challenging
problem. We have developed a method for constructing functionals for excited
states by splitting k-space according to the occupation of orbitals. In this
paper we first show the accuracy of kinetic energy functional thus obtained. We
then perform a response function analysis of the kinetic energy functional
proposed by us and show why method of splitting the k-space could be the method
of choice for construction of energy functionals for excited states.Comment: 11 page
Dogs as Sources and Sentinels of Parasites in Humans and Wildlife, Northern Canada
A minimum of 11 genera of parasites, including 7 known or suspected to cause zoonoses, were detected in dogs in 2 northern Canadian communities. Dogs in remote settlements receive minimal veterinary care and may serve as sources and sentinels for parasites in persons and wildlife, and as parasite bridges between wildlife and humans
A look at the other 90 per cent: Investigating British Sign Language vocabulary knowledge in deaf children from different language learning backgrounds
In this study we present new data on deaf children's receptive and expressive vocabulary knowledge in British Sign Language (BSL) from a sample consisting of children with deaf parents, children with hearing parents, and children with additional needs. Their performance on three BSL vocabulary tasks was compared with (previously reported findings from) a sample of deaf fluent signers. We use these data to assess the effects of some key demographic/ child variables on deaf signing children's vocabulary and discuss findings in the relation to the meaning of 'normative' data and samples for this heterogeneous population. Findings show no effect of the presence of additional disabilities on participants' scores for any of the three tasks. As expected, chronological age is the most significant factor in performance on all vocabulary tasks while the number of deaf relatives only becomes statistically significant for the form recall task. This study contributes to the field of sign language assessment by seeking to identify key variables in heterogeneity and how these variables affect signed vocabulary acquisition with the long-term objective of informing intervention
N=8 superconformal gauge theories and M2 branes
Based on recent developments, in this letter we find 2+1 dimensional gauge
theories with scale invariance and N=8 supersymmetry. The gauge theories are
defined by a Lagrangian and are based on an infinite set of 3-algebras,
constructed as an extension of ordinary Lie algebras. Recent no-go theorems on
the existence of 3-algebras are circumvented by relaxing the assumption that
the invariant metric is positive definite. The gauge group is non compact, and
its maximally compact subgroup can be chosen to be any ordinary Lie group,
under which the matter fields are adjoints or singlets. The theories are parity
invariant and do not admit any tunable coupling constant. In the case of SU(N)
the moduli space of vacua contains a branch of the form (R^8)^N/S_N. These
properties are expected for the field theory living on a stack of M2 branes.Comment: 14 pages, no figure
The Giant Inflaton
We investigate a new mechanism for realizing slow roll inflation in string
theory, based on the dynamics of p anti-D3 branes in a class of mildly warped
flux compactifications. Attracted to the bottom of a warped conifold throat,
the anti-branes then cluster due to a novel mechanism wherein the background
flux polarizes in an attempt to screen them. Once they are sufficiently close,
the M units of flux cause the anti-branes to expand into a fuzzy NS5-brane,
which for rather generic choices of p/M will unwrap around the geometry,
decaying into D3-branes via a classical process. We find that the effective
potential governing this evolution possesses several epochs that can
potentially support slow-roll inflation, provided the process can be arranged
to take place at a high enough energy scale, of about one or two orders of
magnitude below the Planck energy; this scale, however, lies just outside the
bounds of our approximations.Comment: 31 pages, 4 figures, LaTeX. v2: references added, typos fixe
The implications of biodiversity loss for the dynamics of wildlife in Australia
Our study aimed to identify the broad effects of native fossorial species on leaf litter, and make
inferences about their mechanistic influence on fire behavior using simulation models (Hayward et al.,
2016). This conceptual link has long been hypothesized, but here we present empirical evidence to
support it; our results suggest that native fossorial mammals have fire-suppressive effects because
their activity results in higher levels of litter decomposition, and a reduced fuel load across the
landscape. The expert commentaries build on this study and raise pertinent points for further
consideration.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-17952017-12-31hb2016Centre for Wildlife Managemen
Two-dimensional superstrings and the supersymmetric matrix model
We present evidence that the supersymmetric matrix model of Marinari and
Parisi represents the world-line theory of N unstable D-particles in type II
superstring theory in two dimensions. This identification suggests that the
matrix model gives a holographic description of superstrings in a
two-dimensional black hole geometry.Comment: 22 pages, 2 figures; v2: corrected eqn 4.6; v3: corrected appendices
and discussion of vacua, added ref
Evolution of HCl Concentrations in the Lower Stratosphere from 1991 to 1996 Following the Eruption of Mt. Pinatubo
Geophysical Research Letters, Vol. 25, No. 7, pp. 995-998, April 1, 1998.In situ measurements of hydrochloric acid in the lower stratosphere reveal that its mean abundance relative to that of total inorganic chlorine..
Nonlinear electrodynamics and CMB polarization
Recently WMAP and BOOMERanG experiments have set stringent constraints on the
polarization angle of photons propagating in an expanding universe: . The polarization of the Cosmic Microwave
Background radiation (CMB) is reviewed in the context of nonlinear
electrodynamics (NLED). We compute the polarization angle of photons
propagating in a cosmological background with planar symmetry. For this
purpose, we use the Pagels-Tomboulis (PT) Lagrangian density describing NLED,
which has the form , where , and the parameter featuring the
non-Maxwellian character of the PT nonlinear description of the electromagnetic
interaction. After looking at the polarization components in the plane
orthogonal to the ()-direction of propagation of the CMB photons, the
polarization angle is defined in terms of the eccentricity of the universe, a
geometrical property whose evolution on cosmic time (from the last scattering
surface to the present) is constrained by the strength of magnetic fields over
extragalactic distances.Comment: 17 pages, 2 figures, minor changes, references adde
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