7,997 research outputs found
Aperture Supervision for Monocular Depth Estimation
We present a novel method to train machine learning algorithms to estimate
scene depths from a single image, by using the information provided by a
camera's aperture as supervision. Prior works use a depth sensor's outputs or
images of the same scene from alternate viewpoints as supervision, while our
method instead uses images from the same viewpoint taken with a varying camera
aperture. To enable learning algorithms to use aperture effects as supervision,
we introduce two differentiable aperture rendering functions that use the input
image and predicted depths to simulate the depth-of-field effects caused by
real camera apertures. We train a monocular depth estimation network end-to-end
to predict the scene depths that best explain these finite aperture images as
defocus-blurred renderings of the input all-in-focus image.Comment: To appear at CVPR 2018 (updated to camera ready version
On Convergence Properties of Shannon Entropy
Convergence properties of Shannon Entropy are studied. In the differential
setting, it is shown that weak convergence of probability measures, or
convergence in distribution, is not enough for convergence of the associated
differential entropies. A general result for the desired differential entropy
convergence is provided, taking into account both compactly and uncompactly
supported densities. Convergence of differential entropy is also characterized
in terms of the Kullback-Liebler discriminant for densities with fairly general
supports, and it is shown that convergence in variation of probability measures
guarantees such convergence under an appropriate boundedness condition on the
densities involved. Results for the discrete setting are also provided,
allowing for infinitely supported probability measures, by taking advantage of
the equivalence between weak convergence and convergence in variation in this
setting.Comment: Submitted to IEEE Transactions on Information Theor
Reversality of optical interactions in noncentrosymmetric media
The interaction of an electromagnetic wave with a noncentrosymmetric crystal is not necessarily time reversible, and the departure from reversality may be seen in nonlocal (wave-vector linear) phenomena. However, relativistic symmetry with respect to simultaneous time and space inversion is always preserved in optics
Relating Agulhas leakage to the Agulhas Current retroflection location
The relation between the Agulhas Current
retroflection location and the magnitude of Agulhas leakage,
the transport of water from the Indian to the Atlantic Ocean,
is investigated in a high-resolution numerical ocean model.
Sudden eastward retreats of the Agulhas Current retroflection
loop are linearly related to the shedding of Agulhas rings,
where larger retreats generate larger rings. Using numerical
Lagrangian floats a 37 year time series of the magnitude of
Agulhas leakage in the model is constructed. The time series
exhibits large amounts of variability, both on weekly and annual
time scales. A linear relation is found between the magnitude
of Agulhas leakage and the location of the Agulhas
Current retroflection, both binned to three month averages.
In the relation, a more westward location of the Agulhas Current
retroflection corresponds to an increased transport from
the Indian Ocean to the Atlantic Ocean. When this relation
is used in a linear regression and applied to almost 20 years
of altimetry data, it yields a best estimate of the mean magnitude
of Agulhas leakage of 13.2 Sv. The early retroflection
of 2000, when Agulhas leakage was probably halved, can be
identified using the regression
Elimination of mother- to - child transmission of HIV in South Africa : Rapid scale- up using quality improvement
PKBackground: South Africa (SA) is committed to achieving the goal of eliminating mother-to-child transmission (MTCT) of HIV by 2015. To achieve this, universal coverage of quality antenatal, labour, delivery and postnatal services for all women has to be attained. Over the past decade, the prevention of mother-to-child transmission (PMTCT) programme has been scaled up to reach all healthcare facilities in the country. However, challenges persist in achieving 100% coverage and access to the programme.
Objectives: We describe the process undertaken by the National Department of Health (NDoH), in collaboration with partners, to develop, implement and monitor a data-driven intervention to improve facility, district, provincial and national PMTCT-related performance.
Methods: Between 2011 and 2013, the NDoH developed and implemented an intervention using data-driven participatory processes to understand facility-level bottlenecks to optimise PMTCT implementation and to scale up priority PMTCT actions nationally.
Results: There was remarkable improvement across all key indicators in the PMTCT cascade over the 3 years 2011 - 2013. Simple monitoring tools such as a visual dashboard and data for action reports were successfully used to improve the performance of the PMTCT programme across SA. MTCT has shown a significant downward trend.
Conclusions: It is feasible to implement district-level, data-driven quality improvement processes at a national scale to improve the performance of the PMTCT programme at the local level
A district health service in Khayelitsha panacea or pipedream?
Khayelitsha is an underserviced, largely infonnal urban settlement on the edge of Cape Town. It is home to some 350 000 people. This paper maintains that a district health service would be beneficial in Khayelitsha. Advantages include (i) the integration and co-ordination of services with coherent management of health care; (ii) the ability to prioritise and act on problems with the full range of preventive and curative measures as well as intersectoral support; and (iil) the accountability of health providers. Some ofthe steps taken towards the initiation of a district health service are illustrated in a discussion of the recent changes in health service structures in Khayelitsha. There are many obstacles to the implementation ofa formal district health service and these are discussed briefly
Circular dichroism of cholesteric polymers and the orbital angular momentum of light
We explore experimentally if the light's orbital angular momentum (OAM)
interacts with chiral nematic polymer films. Specifically, we measure the
circular dichroism of such a material using light beams with different OAM. We
investigate the case of strongly focussed, non-paraxial light beams, where the
spatial and polarization degrees of freedom are coupled. Within the
experimental accuracy, we cannot find any influence of the OAM on the circular
dichroism of the cholesteric polymer.Comment: 3 pages, 4 figure
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