17,723 research outputs found
Spending Health Care Dollars Wisely: Can Cost-Effectiveness Analysis Help? 16th Annual Herbert Lourie Memorial Lecture on Health Policy
Are we getting the most health improvement possible for our money. In other words, are all the things that we do in medicine really worth it? That is where cost-effectiveness comes in. As a nation, we have been unwilling, at least publicly, to look explicitly at the value, in terms of improved health outcome, that we get for our health care dollars. With advances in medical technology putting unsustainable pressure on health care costs, our historical reluctance to measure value for health care may have to change. I start this brief by describing cost-effectiveness analysis as a method of determining the value, measured in Quality-Adjusted Life Years, of medical technologies as they are applied to treat, diagnose, or prevent various conditions. Based on this information, I then argue that some highly beneficial, low-cost procedures are significantly underutilized, and that other medical technologies may be overutilized based on the amount of health benefit they yield in relation to their cost. Next, I give examples from current research, my own and that of colleagues, illustrating how cost-effectiveness analysis can be used to guide the use of new diagnostic testing technologies (such as DNA or RNA typing of infectious agents or identification of genomic or proteinomic markers in cancer patients).
An Extension of the Faddeev-Jackiw Technique to Fields in Curved Spacetimes
The Legendre transformation on singular Lagrangians, e.g. Lagrangians
representing gauge theories, fails due to the presence of constraints. The
Faddeev-Jackiw technique, which offers an alternative to that of Dirac, is a
symplectic approach to calculating a Hamiltonian paired with a well-defined
initial value problem when working with a singular Lagrangian. This phase space
coordinate reduction was generalized by Barcelos-Neto and Wotzasek to simplify
its application. We present an extension of the Faddeev-Jackiw technique for
constraint reduction in gauge field theories and non-gauge field theories that
are coupled to a curved spacetime that is described by General Relativity. A
major difference from previous formulations is that we do not explicitly
construct the symplectic matrix, as that is not necessary. We find that the
technique is a useful tool that avoids some of the subtle complications of the
Dirac approach to constraints. We apply this formulation to the Ginzburg-Landau
action and provide a calculation of its Hamiltonian and Poisson brackets in a
curved spacetime.Comment: 30 pages, updated to reflect published versio
Quantum Fidelity Decay of Quasi-Integrable Systems
We show, via numerical simulations, that the fidelity decay behavior of
quasi-integrable systems is strongly dependent on the location of the initial
coherent state with respect to the underlying classical phase space. In
parallel to classical fidelity, the quantum fidelity generally exhibits
Gaussian decay when the perturbation affects the frequency of periodic phase
space orbits and power-law decay when the perturbation changes the shape of the
orbits. For both behaviors the decay rate also depends on initial state
location. The spectrum of the initial states in the eigenbasis of the system
reflects the different fidelity decay behaviors. In addition, states with
initial Gaussian decay exhibit a stage of exponential decay for strong
perturbations. This elicits a surprising phenomenon: a strong perturbation can
induce a higher fidelity than a weak perturbation of the same type.Comment: 11 pages, 11 figures, to be published Phys. Rev.
Energetic Suppression of Decoherence in Exchange-Only Quantum Computation
Universal quantum computation requiring only the Heisenberg exchange
interaction and suppressing decoherence via an energy gap is presented. The
combination of an always-on exchange interaction between the three physical
qubits comprising the encoded qubit and a global magnetic field generates an
energy gap between the subspace of interest and all other states. This energy
gap suppresses decoherence. Always-on exchange couplings greatly simplify
hardware specifications and the implementation of inter-logical-qubit gates. A
controlled phase gate can be implemented using only three Heisenberg exchange
operations all of which can be performed simultaneously.Comment: 4 pages, 4 figure
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
A Scalable Architecture for Coherence-Preserving Qubits
We propose scalable architectures for the coherence-preserving qubits
introduced by Bacon, Brown, and Whaley [Phys. Rev. Lett. {\bf 87}, 247902
(2001)]. These architectures employ extra qubits providing additional degrees
of freedom to the system. We show that these extra degrees of freedom can be
used to counter errors in coupling strength within the coherence-preserving
qubit and to combat interactions with environmental qubits. The presented
architectures incorporate experimentally viable methods for inter-logical-qubit
coupling and can implement a controlled phase gate via three simultaneous
Heisenberg exchange operations. The extra qubits also provide flexibility in
the arrangement of the physical qubits. Specifically, all physical qubits of a
coherent-preserving qubit lattice can be placed in two spatial dimensions. Such
an arrangement allows for universal cluster state computation.Comment: 4 pages, 4 figure
Quantum Cellular Automata Pseudo-Random Maps
Quantum computation based on quantum cellular automata (QCA) can greatly
reduce the control and precision necessary for experimental implementations of
quantum information processing. A QCA system consists of a few species of
qubits in which all qubits of a species evolve in parallel. We show that, in
spite of its inherent constraints, a QCA system can be used to study complex
quantum dynamics. To this aim, we demonstrate scalable operations on a QCA
system that fulfill statistical criteria of randomness and explore which
criteria of randomness can be fulfilled by operators from various QCA
architectures. Other means of realizing random operators with only a few
independent operators are also discussed.Comment: 7 pages, 8 figures, submitted to PR
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