15,536 research outputs found
Scaling in a continuous time model for biological aging
In this paper we consider a generalization to the asexual version of the
Penna model for biological aging, where we take a continuous time limit. The
genotype associated to each individual is an interval of real numbers over
which Dirac --functions are defined, representing genetically
programmed diseases to be switched on at defined ages of the individual life.
We discuss two different continuous limits for the evolution equation and two
different mutation protocols, to be implemented during reproduction. Exact
stationary solutions are obtained and scaling properties are discussed.Comment: 10 pages, 6 figure
Nanometric pitch in modulated structures of twist-bend nematic liquid crystals
The extended Frank elastic energy density is used to investigate the
existence of a stable periodically modulate structure that appears as a ground
state exhibiting a twist-bend molecular arrangement. For an unbounded sample,
we show that the twist-bend nematic phase is characterized by a
heliconical structure with a pitch in the nano-metric range, in agreement with
experimental results. For a sample of finite thickness, we show that the wave
vector of the stable periodic structure depends not only on the elastic
parameters but also on the anchoring energy, easy axis direction, and the
thickness of the sample.Comment: 11 page
Frequency up- and down-conversions in two-mode cavity quantum electrodynamics
In this letter we present a scheme for the implementation of frequency up-
and down-conversion operations in two-mode cavity quantum electrodynamics
(QED). This protocol for engineering bilinear two-mode interactions could
enlarge perspectives for quantum information manipulation and also be employed
for fundamental tests of quantum theory in cavity QED. As an application we
show how to generate a two-mode squeezed state in cavity QED (the original
entangled state of Einstein-Podolsky-Rosen)
Sherrington-Kirkpatrick model near : expanding around the Replica Symmetric Solution
An expansion for the free energy functional of the Sherrington-Kirkpatrick
(SK) model, around the Replica Symmetric SK solution is investigated. In particular, when the
expansion is truncated to fourth order in. . The
Full Replica Symmetry Broken (FRSB) solution is explicitly found but it turns
out to exist only in the range of temperature , not
including T=0. On the other hand an expansion around the paramagnetic solution
up to fourth order yields a FRSB solution
that exists in a limited temperature range .Comment: 18 pages, 3 figure
Regulagem do disco de corte para o plantio direto.
Visando melhorar a eficiência do disco de corte de uma semeadora adubadora, a tração animal, desenvolveu-se uma roda limitadora de profundidade, com um formato especial de haste e eixos independentes para cada lado da roda, que possibilitasse a regulagem de encaixe no disco de corte
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