Methodology of the biological risk classification of animal pathogens in Belgium

The biological hazards posed by micro-organisms have lead to their categorisation into risk groups and the elaboration of classification lists. Current classification systems rely on criteria defined by the World Health Organization, which cover the severity of the disease the micro-organism might cause, its ability to spread and the availability of prophylaxis or efficient treatment. Animal pathogens are classified according to the definitions of the World Organization of Animal Health, which also consider economic aspects of disease. In Europe, classification is often directly linked to containment measures. The Belgian classification system however, only considers the inherent characteristics of the micro-organism, not its use, making the risk classification independent of containment measures. A common classification list for human and animal pathogens has been developed in Belgium using as comprehensive an approach as possible. Evolution of scientific knowledge will demand regular updating of classification lists. This paper describes the Belgian risk classification system and the methodology that was used for its peer-reviewed revision (with a focus on animal pathogens)

Parameterized Post-Newtonian coefficients for Brans-Dicke gravity with d+1 dimensions

We present calculations of Post-Newtonian parameters for Brans-Dicke tensor-scalar gravity in an arbitrary number of compact extra dimensions in both the Jordan and Einstein conformal frames. We find that the parameter gamma, which measures the amount of spacetime curvature per unit mass, becomes a function of omega, the coefficient of the scalar kinetic term in the Brans-Dicke Lagrangian. Experiment has placed strong constraints on gamma which require that omega become negative in the Jordan frame for any number of extra dimensions, highlighting that this formulation is not physical. We also confirm the well-known result that a compact extra dimension can be equivalently viewed as a massless scalar `dilaton.' In the Einstein frame, we find that the behavior of gamma as constrained by experiment replicates that which is predicted by string theory.Comment: 9 pages, accepted in Classical and Quantum Gravit

Kaluza-Klein and Gauss-Bonnet cosmic strings

We make a systematic investigation of stationary cylindrically symmetric solutions to the five-dimensional Einstein and Einstein-Gauss-Bonnet equations. Apart from the five-dimensional neutral cosmic string metric, we find two new exact solutions which qualify as cosmic strings, one corresponding to an electrically charged cosmic string, the other to an extended superconducting cosmic string surrounding a charged core. In both cases, test particles are deflected away from the singular line source. We extend both kinds of solutions to exact multi-cosmic string solutions.Comment: 26 pages, LaTex, no figure

Evaluation, contrôle et prévention du risque de transmission du virus influenza aviaire à l'homme

Since mid-december 2003, an epizootic of highly pathogenic avian influenza (type A, sub-type H5N1) occurs in eastern and south-eastern Asia. This epizootic is historically unprecedented in its virulence, geographical spread, and economic consequences for the agricultural sector. Implications for human health were registered in Vietnam and in Thailand. This paper summarizes the current knowledge about the risk evaluation of the transmission of avian influenza virus to humans. The current asian epizootic has highlighted the key role of global health information systems and also the need for exhaustive notification of human and animal cases. It reinforces the concept of veterinary public health

Solutions of multigravity theories and discretized brane worlds

We determine solutions to 5D Einstein gravity with a discrete fifth dimension. The properties of the solutions depend on the discretization scheme we use and some of them have no continuum counterpart. In particular, we find that the neglect of the lapse field (along the discretized direction) gives rise to Randall-Sundrum type metric with a negative tension brane. However, no brane source is required. We show that this result is robust under changes in the discretization scheme. The inclusion of the lapse field gives rise to solutions whose continuum limit is gauge fixed by the discretization scheme. We find however one particular scheme which leads to an undetermined lapse reflecting the reparametrization invariance of the continuum theory. We also find other solutions, with no continuum counterpart with changes in the metric signature or avoidance of singularity. We show that the models allow a continuous mass spectrum for the gravitons with an effective 4D interaction at small scales. We also discuss some cosmological solutions.Comment: 19 page

O adsorption and incipient oxidation of the Mg(0001) surface

First principles density functional calculations are used to study the early oxidation stages of the Mg(0001) surface for oxygen coverages 1/16 <= Theta <= 3 monolayers. It is found that at very low coverages O is incorporated below the topmost Mg layer in tetrahedral sites. At higher oxygen-load the binding in on-surface sites is increased but at one monolayer coverage the on-surface binding is still about 60 meV weaker than for subsurface sites. The subsurface octahedral sites are found to be unfavorable compared to subsurface tetrahedral sites and to on-surface sites. At higher coverages oxygen adsorbs both under the surface and up. Our calculations predict island formation and clustering of incorporated and adsorbed oxygen in agreement with previous calculations. The calculated configurations are compared with the angle-scanned x-ray photoelectron diffraction experiment to determine the geometrical structure of the oxidized Mg(0001) surface.Comment: 10 pages, 5 figure

Consistent Group and Coset Reductions of the Bosonic String

Dimensional reductions of pure Einstein gravity on cosets other than tori are inconsistent. The inclusion of specific additional scalar and p-form matter can change the situation. For example, a D-dimensional Einstein-Maxwell-dilaton system, with a specific dilaton coupling, is known to admit a consistent reduction on S^2= SU(2)/U(1), of a sort first envisaged by Pauli. We provide a new understanding, by showing how an S^3=SU(2) group-manifold reduction of (D+1)-dimensional Einstein gravity, of a type first indicated by DeWitt, can be broken into in two steps; a Kaluza-type reduction on U(1) followed by a Pauli-type coset reduction on S^2. More generally, we show that any D-dimensional theory that itself arises as a Kaluza U(1) reduction from (D+1) dimensions admits a consistent Pauli reduction on any coset of the form G/U(1). Extensions to the case G/H are given. Pauli coset reductions of the bosonic string on G= (G\times G)/G are believed to be consistent, and a consistency proof exists for S^3=SO(4)/SO(3). We examine these reductions, and arguments for consistency, in detail. The structures of the theories obtained instead by DeWitt-type group-manifold reductions of the bosonic string are also studied, allowing us to make contact with previous such work in which only singlet scalars are retained. Consistent truncations with two singlet scalars are possible. Intriguingly, despite the fact that these are not supersymmetric models, if the group manifold has dimension 3 or 25 they admit a superpotential formulation, and hence first-order equations yielding domain-wall solutions.Comment: Latex, 5 figures, 45 pages, minor correction