5,140 research outputs found
Decentralization and Health: Case Studies of Kenya, Pakistan, and the Philippines
Decentralization, defined by the World Bank (2001) as, “the transfer of authority and responsibility for public functions from the central government to intermediate and local governments or quasi-‐independent government organizations and/or the private sector,” is a movement that has gained much traction in recent history. For many countries undergoing decentralization, a major driver has been a desire to increase the role and participation of local governments in the decision-‐making space. In doing this, it is hoped to create governance structures that are more accountable and responsive to the people. For health, decentralization has been touted as a potential way to improve responsiveness to local needs, improve service delivery, and improve equitability. In light of these goals, many countries as part of their political decentralization have also opted to decentralize healthcare.https://jdc.jefferson.edu/cwicposters/1020/thumbnail.jp
Spatial distribution and characterization of non-apical progenitors in the zebrafish embryo central nervous system.
Studies of non-apical progenitors (NAPs) have been largely limited to the developing mammalian cortex. They are postulated to generate the increase in neuron numbers that underlie mammalian brain expansion. Recently, NAPs have also been reported in the retina and central nervous system of non-mammalian species; in the latter, however, they remain poorly characterized. Here, we characterize NAP location along the zebrafish central nervous system during embryonic development, and determine their cellular and molecular characteristics and renewal capacity. We identified a small population of NAPs in the spinal cord, hindbrain and telencephalon of zebrafish embryos. Live-imaging analysis revealed at least two types of mitotic behaviour in the telencephalon: one NAP subtype retains the apical attachment during division, while another divides in a subapical position disconnected from the apical surface. All NAPs observed in spinal cord lost apical contact prior to mitoses. These NAPs express HuC and produce two neurons from a single division. Manipulation of Notch activity reveals that neurons and NAPs in the spinal cord use similar regulatory mechanisms. This work suggests that the majority of spinal NAPs in zebrafish share characteristics with basal progenitors in mammalian brains
Binding Sites Analyser (BiSA): Software for genomic binding sites archiving and overlap analysis
Genome-wide mapping of transcription factor binding and histone modification reveals complex patterns of interactions. Identifying overlaps in binding patterns by different factors is a major objective of genomic studies, but existing methods to archive large numbers of datasets in a personalised database lack sophistication and utility. Therefore we have developed transcription factor DNA binding site analyser software (BiSA), for archiving of binding regions and easy identification of overlap with or proximity to other regions of interest. Analysis results can be restricted by chromosome or base pair overlap between regions or maximum distance between binding peaks. BiSA is capable of reporting overlapping regions that share common base pairs; regions that are nearby; regions that are not overlapping; and average region sizes. BiSA can identify genes located near binding regions of interest, genomic features near a gene or locus of interest and statistical significance of overlapping regions can also be reported. Overlapping results can be visualized as Venn diagrams. A major strength of BiSA is that it is supported by a comprehensive database of publicly available transcription factor binding sites and histone modifications, which can be directly compared to user data. The documentation and source code are available on http://bisa.sourceforge.net © 2014 Khushi et al
Light splitting in nanoporous gold and silver
Figure Persented: Nanoporous gold and silver exhibit strong, omnidirectional broad-band absorption in the far-field. Even though they consist entirely of gold or silver atoms, these materials appear black and dull, in great contrast with the familiar luster of continuous gold and silver. The nature of these anomalous optical characteristics is revealed here by combining nanoscale electron energy loss spectroscopy with discrete dipole and boundary element simulations. It is established that the strong broad-band absorption finds its origin in nanoscale splitting of light, with great local variations in the absorbed color. This nanoscale polychromaticity results from the excitation of localized surface plasmon resonances, which are imaged and analyzed here with deep sub-wavelength, nanometer spatial resolution. We demonstrate that, with this insight, it is possible to customize the absorbance and reflectance wavelength bands of thin nanoporous films by only tuning their morphology. © 2011 American Chemical Society
Sequential Posted Price Mechanisms with Correlated Valuations
We study the revenue performance of sequential posted price mechanisms and
some natural extensions, for a general setting where the valuations of the
buyers are drawn from a correlated distribution. Sequential posted price
mechanisms are conceptually simple mechanisms that work by proposing a
take-it-or-leave-it offer to each buyer. We apply sequential posted price
mechanisms to single-parameter multi-unit settings in which each buyer demands
only one item and the mechanism can assign the service to at most k of the
buyers. For standard sequential posted price mechanisms, we prove that with the
valuation distribution having finite support, no sequential posted price
mechanism can extract a constant fraction of the optimal expected revenue, even
with unlimited supply. We extend this result to the the case of a continuous
valuation distribution when various standard assumptions hold simultaneously.
In fact, it turns out that the best fraction of the optimal revenue that is
extractable by a sequential posted price mechanism is proportional to ratio of
the highest and lowest possible valuation. We prove that for two simple
generalizations of these mechanisms, a better revenue performance can be
achieved: if the sequential posted price mechanism has for each buyer the
option of either proposing an offer or asking the buyer for its valuation, then
a Omega(1/max{1,d}) fraction of the optimal revenue can be extracted, where d
denotes the degree of dependence of the valuations, ranging from complete
independence (d=0) to arbitrary dependence (d=n-1). Moreover, when we
generalize the sequential posted price mechanisms further, such that the
mechanism has the ability to make a take-it-or-leave-it offer to the i-th buyer
that depends on the valuations of all buyers except i's, we prove that a
constant fraction (2-sqrt{e})/4~0.088 of the optimal revenue can be always be
extracted.Comment: 29 pages, To appear in WINE 201
Network-wide Configuration Synthesis
Computer networks are hard to manage. Given a set of high-level requirements
(e.g., reachability, security), operators have to manually figure out the
individual configuration of potentially hundreds of devices running complex
distributed protocols so that they, collectively, compute a compatible
forwarding state. Not surprisingly, operators often make mistakes which lead to
downtimes. To address this problem, we present a novel synthesis approach that
automatically computes correct network configurations that comply with the
operator's requirements. We capture the behavior of existing routers along with
the distributed protocols they run in stratified Datalog. Our key insight is to
reduce the problem of finding correct input configurations to the task of
synthesizing inputs for a stratified Datalog program. To solve this synthesis
task, we introduce a new algorithm that synthesizes inputs for stratified
Datalog programs. This algorithm is applicable beyond the domain of networks.
We leverage our synthesis algorithm to construct the first network-wide
configuration synthesis system, called SyNET, that support multiple interacting
routing protocols (OSPF and BGP) and static routes. We show that our system is
practical and can infer correct input configurations, in a reasonable amount
time, for networks of realistic size (> 50 routers) that forward packets for
multiple traffic classes.Comment: 24 Pages, short version published in CAV 201
On the Origin of the Spiral Morphology in the Elias 2-27 Circumstellar Disk
The young star Elias 2-27 has recently been observed to posses a massive circumstellar disk with two prominent large-scale spiral arms. In this Letter, we perform three-dimensional Smoothed Particle Hydrodynamics simulations, radiative transfer modeling, synthetic ALMA imaging, and an unsharped masking technique to explore three possibilities for the origin of the observed structures - an undetected companion either internal or external to the spirals, and a self-gravitating disk. We find that a gravitationally unstable disk and a disk with an external companion can produce morphology that is consistent with the observations. In addition, for the latter, we find that the companion could be a relatively massive planetary-mass companion (≲10-13 M Jup ) and located at large radial distances (between ≈300-700 au). We therefore suggest that Elias 2-27 may be one of the first detections of a disk undergoing gravitational instabilities, or a disk that has recently undergone fragmentation to produce a massive companion.We acknowledge support from the DISCSIM project, grant agreement 341137 under ERC-2013-ADG. F.M. acknowledges support from The Leverhulme Trust. This Letter uses the following ALMA data: ADS/JAO.ALMA# 2013.1.00498.S. This work used the Darwin DiRAC HPC cluster at the University of Cambridge and was undertaken on the Cambridge COSMOS SMP system, part of the STFC DiRAC HPC Facility supported by BIS NeI capital grant ST/J005673/1 and STFC grants ST/H008586/1, ST/K00333X/1
The extremely truncated circumstellar disc of V410 X-ray 1: A precursor to TRAPPIST-1?
Protoplanetary discs around brown dwarfs and very low mass stars offer some
of the best prospects for forming Earth-sized planets in their habitable zones.
To this end, we study the nature of the disc around the very low mass star V410
X-ray 1, whose SED is indicative of an optically thick and very truncated dust
disc, with our modelling suggesting an outer radius of only 0.6 au. We
investigate two scenarios that could lead to such a truncation, and find that
the observed SED is compatible with both. The first scenario involves the
truncation of both the dust and gas in the disc, perhaps due to a previous
dynamical interaction or the presence of an undetected companion. The second
scenario involves the fact that a radial location of 0.6 au is close to the
expected location of the HO snowline in the disc. As such, a combination of
efficient dust growth, radial migration, and subsequent fragmentation within
the snowline leads to an optically thick inner dust disc and larger, optically
thin outer dust disc. We find that a firm measurement of the CO --1 line
flux would enable us to distinguish between these two scenarios, by enabling a
measurement of the radial extent of gas in the disc. Many models we consider
contain at least several Earth-masses of dust interior to 0.6 au, suggesting
that V410 X-ray 1 could be a precursor to a system with tightly-packed inner
planets, such as TRAPPIST-1
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