1,342 research outputs found
Testing the Children: Do Non-Genetic Health-Care Providers Differ in Their Decision to Advise Genetic Presymptomatic Testing on Minors? A Cross-Sectional Study in Five Countries in the European Union
BACKGROUND: Within Europe many guidelines exist regarding the genetic testing of minors. Predictive and presymptomatic genetic testing of minors is recommended for disorders for which medical intervention/preventive measures exist, and for which early detection improves future medical health. AIM: This study, which is part of the larger 5th EU-framework "genetic education" (GenEd) study, aimed to evaluate the self-reported responses of nongenetic health-care providers in five different EU countries (Germany, France, Sweden, the United Kingdom, and the Netherlands) when confronted with a parent requesting presymptomatic testing on a minor child for a treatable disease. METHODS: A cross-sectional study design using postal, structured scenario-based questionnaires that were sent to 8129 general practitioners (GPs) and pediatricians, between July 2004 and October 2004, addressing self-reported management of a genetic case for which early medical intervention during childhood is beneficial, involving a minor. RESULTS: Most practitioners agreed on testing the oldest child, aged 12 years (81.5% for GPs and 87.2% for pediatricians), and not testing the youngest child, aged 6 months (72.6% for GPs and 61.3% for pediatricians). After multivariate adjustment there were statistical differences between countries in recommending a genetic test for the child at the age of 8 years. Pediatricians in France (50%) and Germany (58%) would recommend a test, whereas in the United Kingdom (22%), Sweden (30%), and the Netherlands (32%) they would not. CONCLUSION: Even though presymptomatic genetic testing in minors is recommended for disorders for which medical intervention exists, EU physicians are uncertain at what age starting to do so in young children
Characterisation of a three-dimensional Brownian motor in optical lattices
We present here a detailed study of the behaviour of a three dimensional
Brownian motor based on cold atoms in a double optical lattice [P. Sjolund et
al., Phys. Rev. Lett. 96, 190602 (2006)]. This includes both experiments and
numerical simulations of a Brownian particle. The potentials used are spatially
and temporally symmetric, but combined spatiotemporal symmetry is broken by
phase shifts and asymmetric transfer rates between potentials. The diffusion of
atoms in the optical lattices is rectified and controlled both in direction and
speed along three dimensions. We explore a large range of experimental
parameters, where irradiances and detunings of the optical lattice lights are
varied within the dissipative regime. Induced drift velocities in the order of
one atomic recoil velocity have been achieved.Comment: 8 pages, 14 figure
Enhancement of Rabi Splitting in a Microcavity with an Embedded Superlattice
We have observed a large coupling between the excitonic and photonic modes of
an AlAs/AlGaAs microcavity filled with an 84-({\rm {\AA}})/20({\rm {\AA}})
GaAs/AlGaAs superlattice. Reflectivity measurements on the coupled
cavity-superlattice system in the presence of a moderate electric field yielded
a Rabi splitting of 9.5 meV at T = 238 K. This splitting is almost 50% larger
than that found in comparable microcavities with quantum wells placed at the
antinodes only. We explain the enhancement by the larger density of optical
absorbers in the superlattice, combined with the quasi-two-dimensional binding
energy of field-localized excitons.Comment: 5 pages, 4 figures, submitted to PR
Theoretical Analysis of a Large Momentum Beamsplitter using Bloch Oscillations
In this paper, we present the implementation of Bloch oscillations in an
atomic interferometer to increase the separation of the two interfering paths.
A numerical model, in very good agreement with the experiment, is developed.
The contrast of the interferometer and its sensitivity to phase fluctuations
and to intensity fluctuations are also calculated. We demonstrate that the
sensitivity to phase fluctuations can be significantly reduced by using a
suitable arrangement of Bloch oscillations pulses
Quantum Dynamics in Non-equilibrium Strongly Correlated Environments
We consider a quantum point contact between two Luttinger liquids coupled to
a mechanical system (oscillator). For non-vanishing bias, we find an effective
oscillator temperature that depends on the Luttinger parameter. A generalized
fluctuation-dissipation relation connects the decoherence and dissipation of
the oscillator to the current-voltage characteristics of the device. Via a
spectral representation, this result is generalized to arbitrary leads in a
weak tunneling regime.Comment: 4 pages, 1 figur
All-Optical Broadband Excitation of the Motional State of Trapped Ions
We have developed a novel all-optical broadband scheme for exciting,
amplifying and measuring the secular motion of ions in a radio frequency trap.
Oscillation induced by optical excitation has been coherently amplified to
precisely control and measure the ion's secular motion. Requiring only laser
line-of-sight, we have shown that the ion's oscillation amplitude can be
precisely controlled. Our excitation scheme can generate coherent motion which
is robust against variations in the secular frequency. Therefore, our scheme is
ideal to excite the desired level of oscillatory motion under conditions where
the secular frequency is evolving in time. Measuring the oscillation amplitude
through Doppler velocimetry, we have characterized the experimental parameters
and compared them with a molecular dynamics simulation which provides a
complete description of the system.Comment: 8 pages, 10 figure
Compton scattering beyond the impulse approximation
We treat the non-relativistic Compton scattering process in which an incoming
photon scatters from an N-electron many-body state to yield an outgoing photon
and a recoil electron, without invoking the commonly used frameworks of either
the impulse approximation (IA) or the independent particle model (IPM). An
expression for the associated triple differential scattering cross section is
obtained in terms of Dyson orbitals, which give the overlap amplitudes between
the N-electron initial state and the (N-1) electron singly ionized quantum
states of the target. We show how in the high energy transfer regime, one can
recover from our general formalism the standard IA based formula for the cross
section which involves the ground state electron momentum density (EMD) of the
initial state. Our formalism will permit the analysis and interpretation of
electronic transitions in correlated electron systems via inelastic x-ray
scattering (IXS) spectroscopy beyond the constraints of the IA and the IPM.Comment: 7 pages, 1 figur
Efimov physics from the functional renormalization group
Few-body physics related to the Efimov effect is discussed using the
functional renormalization group method. After a short review of
renormalization in its modern formulation we apply this formalism to the
description of scattering and bound states in few-body systems of identical
bosons and distinguishable fermions with two and three components. The Efimov
effect leads to a limit cycle in the renormalization group flow. Recently
measured three-body loss rates in an ultracold Fermi gas Li atoms are
explained within this framework. We also discuss briefly the relation to the
many-body physics of the BCS-BEC crossover for two-component fermions and the
formation of a trion phase for the case of three species.Comment: 28 pages, 13 figures, invited contribution to a special issue of
"Few-Body Systems" devoted to Efimov physics, published versio
On the self-consistent spin-wave theory of layered Heisenberg magnets
The versions of the self-consistent spin-wave theories (SSWT) of
two-dimensional (2D) Heisenberg ferro- and antiferromagnets with a weak
interlayer coupling and/or magnetic anisotropy, that are based on the
non-linear Dyson-Maleev, Schwinger, and combined boson-pseudofermion
representations, are analyzed. Analytical results for the temperature
dependences of (sublattice) magnetization and short-range order parameter, and
the critical points are obtained. The influence of external magnetic field is
considered. Fluctuation corrections to SSWT are calculated within a
random-phase approximation which takes into account correctly leading and
next-leading logarithmic singularities. These corrections are demonstrated to
improve radically the agreement with experimental data on layered perovskites
and other systems. Thus an account of these fluctuations provides a
quantitative theory of layered magnets.Comment: 46 pages, RevTeX, 7 figure
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