704 research outputs found
Congenital Cytomegalovirus Infection: Management Update
Purpose of review
Until recently, management options in congenital cytomegalovirus (cCMV) infection have been either
conservative or termination of pregnancy. However, medical therapies aimed at reducing the risk of
infection and/or its severity have recently been investigated.
Recent findings
In a phase 2 open label, nonrandomized trial, valaciclovir (ValACV) was given to women carrying a
CMV-infected fetus. ValACV was associated with a greater proportion of asymptomatic neonates when
compared with a historical cohort (82 vs. 43%). However, the study design and the small number of
treated women limit its applicability. Even though initial observational data suggested that hyperimmune
globulin (HIG) therapy in pregnancy was associated with a significantly lower risk of cCMV, its efficacy
has not been borne out in a subsequent phase 2 randomized, placebo controlled, double-blind study
[cCMV 30% in the HIG group, 44% in the placebo group (
P=0.13)]. Furthermore, 11% of fetuses in the
HIG group had transient or permanent abnormalities, compared with 16% in the placebo group.
Summary
ValACV might have a promising role in the antenatal treatment of cCMV infection, but definitive
recommendations require further research. The use of HIG should currently be limited to the research
setting.
Video abstract http://links.lww.com/COID/A18
Sparse image reconstruction on the sphere: implications of a new sampling theorem
We study the impact of sampling theorems on the fidelity of sparse image
reconstruction on the sphere. We discuss how a reduction in the number of
samples required to represent all information content of a band-limited signal
acts to improve the fidelity of sparse image reconstruction, through both the
dimensionality and sparsity of signals. To demonstrate this result we consider
a simple inpainting problem on the sphere and consider images sparse in the
magnitude of their gradient. We develop a framework for total variation (TV)
inpainting on the sphere, including fast methods to render the inpainting
problem computationally feasible at high-resolution. Recently a new sampling
theorem on the sphere was developed, reducing the required number of samples by
a factor of two for equiangular sampling schemes. Through numerical simulations
we verify the enhanced fidelity of sparse image reconstruction due to the more
efficient sampling of the sphere provided by the new sampling theorem.Comment: 11 pages, 5 figure
Implications for compressed sensing of a new sampling theorem on the sphere
A sampling theorem on the sphere has been developed recently, requiring half
as many samples as alternative equiangular sampling theorems on the sphere. A
reduction by a factor of two in the number of samples required to represent a
band-limited signal on the sphere exactly has important implications for
compressed sensing, both in terms of the dimensionality and sparsity of
signals. We illustrate the impact of this property with an inpainting problem
on the sphere, where we show the superior reconstruction performance when
adopting the new sampling theorem compared to the alternative.Comment: 1 page, 2 figures, Signal Processing with Adaptive Sparse Structured
Representations (SPARS) 201
Non-Abelian statistics as a Berry phase in exactly solvable models
We demonstrate how to directly study non-Abelian statistics for a wide class
of exactly solvable many-body quantum systems. By employing exact eigenstates
to simulate the adiabatic transport of a model's quasiparticles, the resulting
Berry phase provides a direct demonstration of their non-Abelian statistics. We
apply this technique to Kitaev's honeycomb lattice model and explicitly
demonstrate the existence of non-Abelian Ising anyons confirming the previous
conjectures. Finally, we present the manipulations needed to transport and
detect the statistics of these quasiparticles in the laboratory. Various
physically realistic system sizes are considered and exact predictions for such
experiments are provided.Comment: 10 pages, 3 figures. To appear in New Journal of Physic
Interacting non-Abelian anyons as Majorana fermions in the honeycomb lattice model
We study the collective states of interacting non-Abelian anyons that emerge
in Kitaev's honeycomb lattice model. Vortex-vortex interactions are shown to
lead to the lifting of the topological degeneracy and the energy is discovered
to exhibit oscillations that are consistent with Majorana fermions being
localized at vortex cores. We show how to construct states corresponding to the
fusion channel degrees of freedom and obtain the energy gaps characterizing the
stability of the topological low energy spectrum. To study the collective
behavior of many vortices, we introduce an effective lattice model of Majorana
fermions. We find necessary conditions for it to approximate the spectrum of
the honeycomb lattice model and show that bi-partite interactions are
responsible for the degeneracy lifting also in many vortex systems.Comment: 22 pages, 12 figures, published versio
Harmonic analysis of spherical sampling in diffusion MRI
In the last decade diffusion MRI has become a powerful tool to non-invasively
study white-matter integrity in the brain. Recently many research groups have
focused their attention on multi-shell spherical acquisitions with the aim of
effectively mapping the diffusion signal with a lower number of q-space
samples, hence enabling a crucial reduction of acquisition time. One of the
quantities commonly studied in this context is the so-called orientation
distribution function (ODF). In this setting, the spherical harmonic (SH)
transform has gained a great deal of popularity thanks to its ability to
perform convolution operations efficiently and accurately, such as the
Funk-Radon transform notably required for ODF computation from q-space data.
However, if the q-space signal is described with an unsuitable angular
resolution at any b-value probed, aliasing (or interpolation) artifacts are
unavoidably created. So far this aspect has been tackled empirically and, to
our knowledge, no study has addressed this problem in a quantitative approach.
The aim of the present work is to study more theoretically the efficiency of
multi-shell spherical sampling in diffusion MRI, in order to gain understanding
in HYDI-like approaches, possibly paving the way to further optimization
strategies.Comment: 1 page, 2 figures, 19th Annual Meeting of International Society for
Magnetic Resonance in Medicin
New procedures for testing whether stock price processes are martingales
We propose procedures for testing whether stock price processes are
martingales based on limit order type betting strategies. We first show that
the null hypothesis of martingale property of a stock price process can be
tested based on the capital process of a betting strategy. In particular with
high frequency Markov type strategies we find that martingale null hypotheses
are rejected for many stock price processes
ISUOG consensus statement on current understanding of the association of neurodevelopmental delay and congenital heart disease: impact on prenatal counseling
Tomograms and other transforms. A unified view
A general framework is presented which unifies the treatment of wavelet-like,
quasidistribution, and tomographic transforms. Explicit formulas relating the
three types of transforms are obtained. The case of transforms associated to
the symplectic and affine groups is treated in some detail. Special emphasis is
given to the properties of the scale-time and scale-frequency tomograms.
Tomograms are interpreted as a tool to sample the signal space by a family of
curves or as the matrix element of a projector.Comment: 19 pages latex, submitted to J. Phys. A: Math and Ge
Suppression of 1/f noise in one-qubit systems
We investigate the generation of quantum operations for one-qubit systems
under classical noise with 1/f^\alpha power spectrum, where 2>\alpha > 0. We
present an efficient way to approximate the noise with a discrete multi-state
Markovian fluctuator. With this method, the average temporal evolution of the
qubit density matrix under 1/f^\alpha noise can be feasibly determined from
recently derived deterministic master equations. We obtain qubit operations
such as quantum memory and the NOT}gate to high fidelity by a gradient based
optimization algorithm. For the NOT gate, the computed fidelities are
qualitatively similar to those obtained earlier for random telegraph noise. In
the case of quantum memory however, we observe a nonmonotonic dependency of the
fidelity on the operation time, yielding a natural access rate of the memory.Comment: 8 pages, 7 figure
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