8,485 research outputs found
Inequalities in maternity care and newborn outcomes: one-year surveillance of births in vulnerable slum communities in Mumbai
Background: Aggregate urban health statistics mask inequalities. We described maternity care in
vulnerable slum communities in Mumbai, and examined differences in care and outcomes between
more and less deprived groups.
Methods: We collected information through a birth surveillance system covering a population of
over 280 000 in 48 vulnerable slum localities. Resident women identified births in their own
localities and mothers and families were interviewed at 6 weeks after delivery. We analysed data
on 5687 births over one year to September 2006. Socioeconomic status was classified using
quartiles of standardized asset scores.
Results: Women in higher socioeconomic quartile groups were less likely to have married and
conceived in their teens (Odds ratio 0.74, 95% confidence interval 0.69–0.79, and 0.82, 0.78–0.87,
respectively). There was a socioeconomic gradient away from public sector maternity care with
increasing socioeconomic status (0.75, 0.70–0.79 for antenatal care and 0.66, 0.61–0.71 for
institutional delivery). Women in the least poor group were five times less likely to deliver at home
(0.17, 0.10–0.27) as women in the poorest group and about four times less likely to deliver in the
public sector (0.27, 0.21–0.35). Rising socioeconomic status was associated with a lower
prevalence of low birth weight (0.91, 0.85–0.97). Stillbirth rates did not vary, but neonatal mortality
rates fell non-significantly as socioeconomic status increased (0.88, 0.71–1.08).
Conclusion: Analyses of this type have usually been applied across the population spectrum from
richest to poorest, and we were struck by the regularly stepped picture of inequalities within the
urban poor, a group that might inadvertently be considered relatively homogeneous. The poorest
slum residents are more dependent upon public sector health care, but the regular progression
towards the private sector raises questions about its quality and regulation. It also underlines the
need for healthcare provision strategies to take account of both sectors
Vacuum as a less hostile environment to entanglement
We derive sufficient conditions for infinite-dimensional systems whose
entanglement is not completely lost in a finite time during its decoherence by
a passive interaction with local vacuum environments. The sufficient conditions
allow us to clarify a class of bipartite entangled states which preserve their
entanglement or, in other words, are tolerant against decoherence in a vacuum.
We also discuss such a class for entangled qubits.Comment: Replaced by the published versio
Minimum-error discrimination between subsets of linearly dependent quantum states
A measurement strategy is developed for a new kind of hypothesis testing. It
assigns, with minimum probability of error, the state of a quantum system to
one or the other of two complementary subsets of a set of N given
non-orthogonal quantum states occurring with given a priori probabilities. A
general analytical solution is obtained for N states that are restricted to a
two-dimensional subspace of the Hilbert space of the system. The result for the
special case of three arbitrary but linearly dependent states is applied to a
variety of sets of three states that are symmetric and equally probable. It is
found that, in this case, the minimum error probability for distinguishing one
of the states from the other two is only about half as large as the minimum
error probability for distinguishing all three states individually.Comment: Representation improved and generalized, references added. Accepted
as a Rapid Communication in Phys. Rev.
Probing the quantumness of channels with mixed states
We present an alternative approach to the derivation of benchmarks for
quantum channels, such as memory or teleportation channels. Using the concept
of effective entanglement and the verification thereof, a testing procedure is
derived which demands very few experimental resources. The procedure is
generalized by allowing for mixed test states. By constructing optimized
measure & re-prepare channels, the benchmarks are found to be very tight in the
considered experimental regimes.Comment: 11 Pages, 9 Figures, published versio
Driven harmonic oscillator as a quantum simulator for open systems
We show theoretically how a driven harmonic oscillator can be used as a
quantum simulator for non-Markovian damped harmonic oscillator. In the general
framework, the results demonstrate the possibility to use a closed system as a
simulator for open quantum systems. The quantum simulator is based on sets of
controlled drives of the closed harmonic oscillator with appropriately tailored
electric field pulses. The non-Markovian dynamics of the damped harmonic
oscillator is obtained by using the information about the spectral density of
the open system when averaging over the drives of the closed oscillator. We
consider single trapped ions as a specific physical implementation of the
simulator, and we show how the simulator approach reveals new physical insight
into the open system dynamics, e.g. the characteristic quantum mechanical
non-Markovian oscillatory behavior of the energy of the damped oscillator,
usually obtained by the non-Lindblad-type master equation, can have a simple
semiclassical interpretation.Comment: 10 pages, 4 figures. V2: Minor modifications and added 2 appendixes
for more details about calculation
Quantum state transformation by dispersive and absorbing four-port devices
The recently derived input-output relations for the radiation field at a
dispersive and absorbing four-port device [T. Gruner and D.-G. Welsch, Phys.
Rev. A 54, 1661 (1996)] are used to derive the unitary transformation that
relates the output quantum state to the input quantum state, including
radiation and matter and without placing frequency restrictions. It is shown
that for each frequency the transformation can be regarded as a well-behaved
SU(4) group transformation that can be decomposed into a product of U(2) and
SU(2) group transformations. Each of them may be thought of as being realized
by a particular lossless four-port device. If for narrow-bandwidth radiation
far from the medium resonances the absorption matrix of the four-port device
can be disregarded, the well-known SU(2) group transformation for a lossless
device is recognized. Explicit formulas for the transformation of Fock-states
and coherent states are given.Comment: 24 pages, RevTe
Molecular dynamics in shape space and femtosecond vibrational spectroscopy of metal clusters
We introduce a method of molecular dynamics in shape space aimed at metal
clusters. The ionic degrees of freedom are described via a dynamically
deformable jellium with inertia parameters derived from an incompressible,
irrotational flow. The shell correction method is used to calculate the
electronic potential energy surface underlying the dynamics. Our finite
temperature simulations of Ag_14 and its ions, following the negative to
neutral to positive scheme, demonstrate the potential of pump and probe
ultrashort laser pulses as a spectroscopy of cluster shape vibrations.Comment: Latex/Revtex, 4 pages with 3 Postscript figure
Off Resonant Pumping for Transition from Continuous to Discrete Spectrum and Quantum Revivals in Systems in Coherent States
We show that in parametrically driven systems and, more generally, in systems
in coherent states, off-resonant pumping can cause a transition from a
continuum energy spectrum of the system to a discrete one, and result in
quantum revivals of the initial state. The mechanism responsible for quantum
revivals in the present case is different from that in the non-linear
wavepacket dynamics of systems such as Rydberg atoms. We interpret the reported
phenomena as an optical analog of Bloch oscillations realized in Fock space and
propose a feasible scheme for inducing Bloch oscillations in trapped ions.Comment: 5 pages, 4 figures, submitted to Jnl. of Optics
s-ordered phase-sum and phase-difference distribuitons of entangled coherent states
The -ordered phase-sum and phase-difference distributions are considered
for Bell-like superpositions of two-mode coherent states. The distributions are
sensitive, respectively, to the sum and difference of the phases of the
entangled coherent states. They show loss of information about the entangled
state and may take on negative values for some orderings .Comment: 8 pages, 2 figures, iopart. accepted for publication in J. Opt. B:
Quantum Semiclass Op
A schematic model for QCD I: Low energy meson states
A simple model for QCD is presented, which is able to reproduce the meson
spectrum at low energy. The model is a Lipkin type model for quarks coupled to
gluons. The basic building blocks are pairs of quark-antiquarks coupled to a
definite flavor and spin. These pairs are coupled to pairs of gluons with spin
zero. The multiplicity problem, which dictates that a given experimental state
can be described in various manners, is removed when a particle-mixing
interaction is turned on. In this first paper of a series we concentrates on
the discussion of meson states at low energy, the so-called zero temperature
limit of the theory. The treatment of baryonic states is indicated, also.Comment: 29 pages, 6 figures. submitted to Phys. Rev.
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