2,761 research outputs found
Pricing of drugs and donations: options for sustainable equity pricing.
Effective medicines exist to treat or alleviate many diseases which predominate in the developing world and cause high mortality and morbidity rates. Price should not be an obstacle preventing access to these medicines. Increasingly, drug donations have been established by drug companies, but these are often limited in time, place or use. Measures exist which are more sustainable and will have a greater positive impact on people's health. Principally, these are encouraging generic competition; adopting into national legislation and implementing TRIPS safeguards to gain access to cheaper sources of drugs; differential pricing; creating high volume or high demand through global and regional procurement; and supporting the production of quality generic drugs by developing countries through voluntary licenses if needed, and facilitating technology transfer
The family of quaternionic quasi-unitary Lie algebras and their central extensions
The family of quaternionic quasi-unitary (or quaternionic unitary
Cayley--Klein algebras) is described in a unified setting. This family includes
the simple algebras sp(N+1) and sp(p,q) in the Cartan series C_{N+1}, as well
as many non-semisimple real Lie algebras which can be obtained from these
simple algebras by particular contractions. The algebras in this family are
realized here in relation with the groups of isometries of quaternionic
hermitian spaces of constant holomorphic curvature. This common framework
allows to perform the study of many properties for all these Lie algebras
simultaneously. In this paper the central extensions for all quasi-simple Lie
algebras of the quaternionic unitary Cayley--Klein family are completely
determined in arbitrary dimension. It is shown that the second cohomology group
is trivial for any Lie algebra of this family no matter of its dimension.Comment: 17 pages, LaTe
Central extensions of the families of quasi-unitary Lie algebras
The most general possible central extensions of two whole families of Lie
algebras, which can be obtained by contracting the special pseudo-unitary
algebras su(p,q) of the Cartan series A_l and the pseudo-unitary algebras
u(p,q), are completely determined and classified for arbitrary p,q. In addition
to the su(p,q) and u({p,q}) algebras, whose second cohomology group is well
known to be trivial, each family includes many non-semisimple algebras; their
central extensions, which are explicitly given, can be classified into three
types as far as their properties under contraction are involved. A closed
expression for the dimension of the second cohomology group of any member of
these families of algebras is given.Comment: 23 pages. Latex2e fil
Integrable potentials on spaces with curvature from quantum groups
A family of classical integrable systems defined on a deformation of the
two-dimensional sphere, hyperbolic and (anti-)de Sitter spaces is constructed
through Hamiltonians defined on the non-standard quantum deformation of a sl(2)
Poisson coalgebra. All these spaces have a non-constant curvature that depends
on the deformation parameter z. As particular cases, the analogues of the
harmonic oscillator and Kepler--Coulomb potentials on such spaces are proposed.
Another deformed Hamiltonian is also shown to provide superintegrable systems
on the usual sphere, hyperbolic and (anti-)de Sitter spaces with a constant
curvature that exactly coincides with z. According to each specific space, the
resulting potential is interpreted as the superposition of a central harmonic
oscillator with either two more oscillators or centrifugal barriers. The
non-deformed limit z=0 of all these Hamiltonians can then be regarded as the
zero-curvature limit (contraction) which leads to the corresponding
(super)integrable systems on the flat Euclidean and Minkowskian spaces.Comment: 19 pages, 1 figure. Two references adde
Maximal superintegrability on N-dimensional curved spaces
A unified algebraic construction of the classical Smorodinsky-Winternitz
systems on the ND sphere, Euclidean and hyperbolic spaces through the Lie
groups SO(N+1), ISO(N), and SO(N,1) is presented. Firstly, general expressions
for the Hamiltonian and its integrals of motion are given in a linear ambient
space , and secondly they are expressed in terms of two geodesic
coordinate systems on the ND spaces themselves, with an explicit dependence on
the curvature as a parameter. On the sphere, the potential is interpreted as a
superposition of N+1 oscillators. Furthermore each Lie algebra generator
provides an integral of motion and a set of 2N-1 functionally independent ones
are explicitly given. In this way the maximal superintegrability of the ND
Euclidean Smorodinsky-Winternitz system is shown for any value of the
curvature.Comment: 8 pages, LaTe
A Bayesian approach to discrete object detection in astronomical datasets
A Bayesian approach is presented for detecting and characterising the signal
from discrete objects embedded in a diffuse background. The approach centres
around the evaluation of the posterior distribution for the parameters of the
discrete objects, given the observed data, and defines the
theoretically-optimal procedure for parametrised object detection. Two
alternative strategies are investigated: the simultaneous detection of all the
discrete objects in the dataset, and the iterative detection of objects. In
both cases, the parameter space characterising the object(s) is explored using
Markov-Chain Monte-Carlo sampling. For the iterative detection of objects,
another approach is to locate the global maximum of the posterior at each
iteration using a simulated annealing downhill simplex algorithm. The
techniques are applied to a two-dimensional toy problem consisting of Gaussian
objects embedded in uncorrelated pixel noise. A cosmological illustration of
the iterative approach is also presented, in which the thermal and kinetic
Sunyaev-Zel'dovich effects from clusters of galaxies are detected in microwave
maps dominated by emission from primordial cosmic microwave background
anisotropies.Comment: 20 pages, 12 figures, accepted by MNRAS; contains some additional
material in response to referee's comment
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