7,116 research outputs found
Dynamics of Logamediate Inflation
A computation of the inflationary observables n_{s} and r is made for
`logamediate' inflation where the cosmological scale factor expands as , and is compared to their predicted values in the
intermediate inflationary theory, where . Both versions prove
to be consistent with observational measurements of the cosmic background
radiation. It is shown that the dynamics of a single inflaton field can be
mimicked by a system of several fields in an analogous manner to that created
by the joint evolution of the fields in assisted power-law inflation.Comment: 7 pages, 5 figures. Extended introductio
A New Generation Gap? Some thoughts on the consequences of increasingly early ICT first contact
One possible consequence of ICT’s rapid rise will be a new ‘generation gap’ arising from differing perceptions of the learning technologies. The nature, causes and consequences of this gap are of interest to educational practitioners and policymakers.
This paper uses data from an ongoing project together with a synopsis of research to describe the ICT-based generation gap that currently exists between students and their teachers and parents. It is argued that this gap may exist between students differing in age by as little as five years.
Results from a related project exploring Networked Information and Communication Literacy Skills (NICLS), are used to introduce a discussion on the nature of any skills gap that must be addressed in the light of this generation gap
Carvão do arroz: epidemiologia, ocorrência e controle.
bitstream/item/56015/1/comunicado-146.pd
DNA-psoralen: single-molecule experiments and first principles calculations
The authors measure the persistence and contour lengths of DNA-psoralen
complexes, as a function of psoralen concentration, for intercalated and
crosslinked complexes. In both cases, the persistence length monotonically
increases until a certain critical concentration is reached, above which it
abruptly decreases and remains approximately constant. The contour length of
the complexes exhibits no such discontinuous behavior. By fitting the relative
increase of the contour length to the neighbor exclusion model, we obtain the
exclusion number and the intrinsic intercalating constant of the psoralen-DNA
interaction. Ab initio calculations are employed in order to provide an
atomistic picture of these experimental findings.Comment: 9 pages, 4 figures in re-print format 3 pages, 4 figures in the
published versio
Non-linear non-local Cosmology
Non-local equations of motion contain an infinite number of derivatives and
commonly appear in a number of string theory models. We review how these
equations can be rewritten in the form of a diffusion-like equation with
non-linear boundary conditions. Moreover, we show that this equation can be
solved as an initial value problem once a set of non-trivial initial conditions
that satisfy the boundary conditions is found. We find these initial conditions
by looking at the linear approximation to the boundary conditions. We then
numerically solve the diffusion-like equation, and hence the non-local
equations, as an initial value problem for the full non-linear potential and
subsequently identify the cases when inflation is attained.Comment: 6 pages, 7 figures. Prepared for 4th International Workshop on The
Dark Side of the Universe, BUE, 1-5 June 200
Fluctuations and oscillations in a simple epidemic model
We show that the simplest stochastic epidemiological models with spatial
correlations exhibit two types of oscillatory behaviour in the endemic phase.
In a large parameter range, the oscillations are due to resonant amplification
of stochastic fluctuations, a general mechanism first reported for
predator-prey dynamics. In a narrow range of parameters that includes many
infectious diseases which confer long lasting immunity the oscillations persist
for infinite populations. This effect is apparent in simulations of the
stochastic process in systems of variable size, and can be understood from the
phase diagram of the deterministic pair approximation equations. The two
mechanisms combined play a central role in explaining the ubiquity of
oscillatory behaviour in real data and in simulation results of epidemic and
other related models.Comment: acknowledgments added; a typo in the discussion that follows Eq. (3)
is corrected
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