16,807 research outputs found
Pan-European Chikungunya surveillance: Designing risk stratified surveillance zones
This article has been made available through the Brunel Open Access Publishing Fund - Copyright @ 2009 Tilston et alThe first documented transmission of Chikungunya within Europe took place in Italy during the summer of 2007. Chikungunya, a viral infection affecting millions of people across Africa and Asia, can be debilitating and no prophylactic treatment exists. Although imported cases are reported frequently across Europe, 2007 was the first confirmed European outbreak and available evidence suggests that Aedes albopictus was the vector responsible and the index case was a visitor from India. This paper proposed pan-European surveillance zones for Chikungunya, based on the climatic conditions necessary for vector activity and viral transmission. Pan-European surveillance provides the best hope for an early-warning of outbreaks, because national boundaries do not play a role in defining the risk of this new vector borne disease threat. A review of climates, where Chikungunya has been active, was used to inform the delineation of three pan-European surveillance zones. These vary in size each month across the June-September period of greatest risk. The zones stretch across southern Europe from Portugal to Turkey. Although the focus of this study was to define the geography of potential surveillance zones based on the climatic limits on the vector and virus, a preliminary examination of inward bound airline passengers was also undertaken. This indicated that France and Italy are likely to be at greater risk due to the number of visitors they receive from Chikungunya active regions, principally viraemic visitors from India. Therefore this study represents a first attempt at creating risk stratified surveillance zones, which we believe could be usefully refined with the use of higher resolution climate data and more complete air travel data
Symplectic Microgeometry II: Generating functions
We adapt the notion of generating functions for lagrangian submanifolds to
symplectic microgeometry. We show that a symplectic micromorphism always admits
a global generating function. As an application, we describe hamiltonian flows
as special symplectic micromorphisms whose local generating functions are the
solutions of Hamilton-Jacobi equations. We obtain a purely categorical
formulation of the temporal evolution in classical mechanics.Comment: 27 pages, 1 figur
Defect Modes and Homogenization of Periodic Schr\"odinger Operators
We consider the discrete eigenvalues of the operator
H_\eps=-\Delta+V(\x)+\eps^2Q(\eps\x), where V(\x) is periodic and Q(\y)
is localized on . For \eps>0 and sufficiently small, discrete
eigenvalues may bifurcate (emerge) from spectral band edges of the periodic
Schr\"odinger operator, H_0 = -\Delta_\x+V(\x), into spectral gaps. The
nature of the bifurcation depends on the homogenized Schr\"odinger operator
L_{A,Q}=-\nabla_\y\cdot A \nabla_\y +\ Q(\y). Here, denotes the inverse
effective mass matrix, associated with the spectral band edge, which is the
site of the bifurcation.Comment: 26 pages, 3 figures, to appear SIAM J. Math. Ana
Aerodynamic heating in the vicinity of corners at hypersonic speeds
Aerodynamic heating in vicinity of corners at hypersonic speed
Euler-Poincare reduction for discrete field theories
In this note, we develop a theory of Euler-Poincare reduction for discrete
Lagrangian field theories. We introduce the concept of Euler-Poincare equations
for discrete field theories, as well as a natural extension of the
Moser-Veselov scheme, and show that both are equivalent. The resulting discrete
field equations are interpreted in terms of discrete differential geometry. An
application to the theory of discrete harmonic mappings is also briefly
discussed.Comment: 24 pages, 3 figures (v2: simplified treatment
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