4,381 research outputs found
Planning an integrated agriculture and health program and designing its evaluation: Experience from Western Kenya.
AbstractMulti-sectoral programs that involve stakeholders in agriculture, nutrition and health care are essential for responding to nutrition problems such as vitamin A deficiency among pregnant and lactating women and their infants in many poor areas of lower income countries. Yet planning such multi-sectoral programs and designing appropriate evaluations, to respond to different disciplinary cultures of evidence, remain a challenge. We describe the context, program development process, and evaluation design of the Mama SASHA project (Sweetpotato Action for Security and Health in Africa) which promoted production and consumption of a bio-fortified, orange-fleshed sweetpotato (OFSP). In planning the program we drew upon information from needs assessments, stakeholder consultations, and a first round of the implementation evaluation of a pilot project. The multi-disciplinary team worked with partner organizations to develop a program theory of change and an impact pathway which identified aspects of the program that would be monitored and established evaluation methods. Responding to the growing demand for greater rigour in impact evaluations, we carried out quasi-experimental allocation by health facility catchment area, repeat village surveys for assessment of change in intervention and control areas, and longitudinal tracking of individual mother-child pairs. Mid-course corrections in program implementation were informed by program monitoring, regular feedback from implementers and partners’ meetings. To assess economic efficiency and provide evidence for scaling we collected data on resources used and project expenses. Managing the multi-sectoral program and the mixed methods evaluation involved bargaining and trade-offs that were deemed essential to respond to the array of stakeholders, program funders and disciplines involved
Antibiotic Elution and Mechanical Strength of PMMA Bone Cement Loaded With Borate Bioactive Glass
A grant from the One-University Open Access Fund at the University of Kansas was used to defray the author's publication fees in this Open Access journal. The Open Access Fund, administered by librarians from the KU, KU Law, and KUMC libraries, is made possible by contributions from the offices of KU Provost, KU Vice Chancellor for Research & Graduate Studies, and KUMC Vice Chancellor for Research. For more information about the Open Access Fund, please see http://library.kumc.edu/authors-fund.xml.Introduction: Local delivery of antibiotics using bone cement as the delivery vehicle is an
established method of managing implant-associated orthopedic infections. Various fillers have been
added to cement to increase antibiotic elution, but they often do so at the expense of strength. This
study evaluated the effect of adding a borate bioactive glass, previously shown to promote bone
formation, on vancomycin elution from PMMA bone cement.
Methods: Five cement composites were made: three loaded with borate bioactive glass along with
0, 1, and 5 grams of vancomycin and two without any glass but with 1 and 5 grams vancomycin to
serve as controls. The specimens were soaked in PBS. Eluate of vancomycin was collected every 24
hours and analyzed by HPLC. Orthopedic-relevant mechanical properties of each composite were
tested over time.
Results: The addition of borate bioactive glass provided an increase in vancomycin release at Day 1
and an increase in sustained vancomycin release throughout the treatment period. An 87.6% and
21.1% increase in cumulative vancomycin release was seen for both 1g and 5g loading groups,
respectively. Compressive strength of all composites remained above the weight-bearing threshold
of 70 MPa throughout the duration of the study with the glass-containing composites showing
comparable strength to their respective controls.
Conclusion: The incorporation of borate bioactive glass into commercial PMMA bone cement can
significantly increase the elution of vancomycin. The mechanical strength of the cement-glass
composites remained above 70 MPa even after soaking for 8 weeks, suggesting their suitability for
orthopedic weight-bearing applications.Marc A. and Elinor J. Asher Orthopedic Research Endowmen
The Nature of the Halo Population of NGC 5128 Resolved with NICMOS on the Hubble Space Telescope
We present the first infrared color-magnitude diagram (CMD) for the halo of a
giant elliptical galaxy. The CMD for the stars in the halo of NGC 5128
(Centaurus A) was constructed from HST NICMOS observations of the WFPC2 CHIP-3
field of Soria et al. (1996) to a 50% completeness magnitude limit of
[F160W]=23.8. This field is located at a distance of 08'50" (~9 kpc) south of
the center of the galaxy. The luminosity function (LF) shows a marked
discontinuity at [F160W]=20.0. This is 1-2 mag above the tip of the red giant
branch (TRGB) expected for an old population (~12 Gyr) at the distance modulus
of NGC 5128. We propose that the majority of stars above the TRGB have
intermediate ages (~2 Gyr), in agreement with the WFPC2 observations of Soria
et al. (1996). Five stars with magnitudes brighter than the LF discontinuity
are most probably due to Galactic contamination. The weighted average of the
mean giant branch color above our 50% completeness limit is
[F110W]-[F160W]=1.22+-0.08 with a dispersion of 0.19 mag. From our
artificial-star experiments we determine that the observed spread in color is
real, suggesting a real spread in metallicity. We estimate the lower and upper
bounds of the stellar metallicity range by comparisons with observations of
Galactic star clusters and theoretical isochrones. Assuming an old population,
we find that, in the halo field of NGC 5128 we surveyed, stars have
metallicities ranging from roughly 1% of solar at the blue end of the color
spread to roughly solar at the red end, with a mean of [Fe/H]=-0.76 and a
dispersion of 0.44 dex.Comment: Accepted for publication in AJ, 23 pages of text, 13 figures, uses
aastex v5.
Doppler assessment of aortic stenosis: a 25-operator study demonstrating why reading the peak velocity is superior to velocity time integral
Aims
Measurements with superior reproducibility are useful clinically and research purposes. Previous reproducibility studies of Doppler assessment of aortic stenosis (AS) have compared only a pair of observers and have not explored the mechanism by which disagreement between operators occurs. Using custom-designed software which stored operators’ traces, we investigated the reproducibility of peak and velocity time integral (VTI) measurements across a much larger group of operators and explored the mechanisms by which disagreement arose.
Methods and results
Twenty-five observers reviewed continuous wave (CW) aortic valve (AV) and pulsed wave (PW) left ventricular outflow tract (LVOT) Doppler traces from 20 sequential cases of AS in random order. Each operator unknowingly measured each peak velocity and VTI twice. VTI tracings were stored for comparison. Measuring the peak is much more reproducible than VTI for both PW (coefficient of variation 10.1 vs. 18.0%; P < 0.001) and CW traces (coefficient of variation 4.0 vs. 10.2%; P < 0.001). VTI is inferior because the steep early and late parts of the envelope are difficult to trace reproducibly. Dimensionless index improves reproducibility because operators tended to consistently over-read or under-read on LVOT and AV traces from the same patient (coefficient of variation 9.3 vs. 17.1%; P < 0.001).
Conclusion
It is far more reproducible to measure the peak of a Doppler trace than the VTI, a strategy that reduces measurement variance by approximately six-fold. Peak measurements are superior to VTI because tracing the steep slopes in the early and late part of the VTI envelope is difficult to achieve reproducibly
The Galaxy Structure-Redshift Relationship
There exists a gradual, but persistent, evolutionary effect in the galaxy
population such that galaxy structure and morphology change with redshift. This
galaxy structure-redshift relationship is such that an increasingly large
fraction of all bright and massive galaxies at redshifts 2 < z < 3 are
morphologically peculiar at wavelengths from rest-frame ultraviolet to
rest-frame optical. There are however examples of morphologically selected
spirals and ellipticals at all redshifts up to z ~ 3. At lower redshift, the
bright galaxy population smoothly transforms into normal ellipticals and
spirals. The rate of this transformation strongly depends on redshift, with the
swiftest evolution occurring between 1 < z < 2. This review characterizes the
galaxy structure-redshift relationship, discusses its various physical causes,
and how these are revealing the mechanisms responsible for galaxy formation.Comment: 20 pages, 8 figures. Invited Review to appear in "Penetrating Bars
Through Masks of Cosmic Dust: The Hubble Tuning Fork Strikes A New Note", ed.
D. Block et a
On the Origin of the Dichotomy of Early-Type Galaxies: The Role of Dry Mergers and AGN Feedback
Using a semi-analytical model for galaxy formation, combined with a large
N-body simulation, we investigate the origin of the dichotomy among early-type
galaxies. We find that boxy galaxies originate from mergers with a progenitor
mass ratio and with a combined cold gas mass fraction . Our model accurately reproduces the observed fraction of boxy systems as
a function of luminosity and halo mass, for both central galaxies and
satellites. After correcting for the stellar mass dependence, the properties of
the last major merger of early-type galaxies are independent of their halo
mass. This provides theoretical support for the conjecture of Pasquali et al
(2007) that the stellar mass of an early-type galaxy is the main parameter that
governs its isophotal shape. We argue that the observed dichotomy of early-type
galaxies has a natural explanation within hierarchical structure formation, and
does not require AGN feedback. Rather, we argue that it owes to the fact that
more massive systems (i) have more massive progenitors, (ii) assemble later,
and (iii) have a larger fraction of early-type progenitors. Each of these three
trends causes the cold gas mass fraction of the progenitors of more massive
early-types to be lower, so that their last major merger was dryer. Finally,
our model predicts that (i) less than 10 percent of all early-type galaxies
form in major mergers that involve two early-type progenitors, (ii) more than
95 percent of all boxy early-type galaxies with M_* < 2 \times 10^{10} h^{-1}
\Msun are satellite galaxies, and (iii) about 70 percent of all low mass
early-types do not form a supermassive black hole binary at their last major
merger. The latter may help to explain why low mass early-types have central
cusps, while their massive counterparts have cores.Comment: 13 pages, 8 figures, submitted for publication in MNRA
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Microcraters in aluminum foils exposed by Stardust
We will present preliminary results on the nature and size frequency distribution of microcraters that formed in aluminum foils during the flyby of comet Wild 2 by the Stardust spacecraft
Gradients of absorption-line strengths in elliptical galaxies
© 1999. The American Astronomical Society. All rights reserved. This is the final published version of the work, which was originally published at https://doi.org/10.1086/308092We have restudied line-strength gradients of 80 elliptical galaxies. Typical metallicity gradients of elliptical galaxies are Delta[Fe/H]/Delta log r similar or equal to -0.3, which is flatter than the gradients predicted by monolithic collapse simulations. The metallicity gradients do not correlate with any physical properties of galaxies, including central and mean metallicities, central velocity dispersions sigma(0), absolute B magnitudes M-B, absolute effective radii R-e, and dynamical masses of galaxies. By using the metallicity gradients, we have calculated mean stellar metallicities for individual ellipticals. Typical mean stellar metallicities are [[Fe/H]] similar or equal to -0.3 and range from [[Fe/H]] similar or equal to -0.8 to +0.3, which is contrary to what Gonzalez & Gorgas claimed; the mean metallicities of ellipticals are not universal. The mean metallicities correlate well with sigma(0) and dynamical masses, though relations for M-B and R-e include significant scatters. We find fundamental planes defined by surface brightnesses SBe, [[Fe/H]], and R-e (or M-B), the scatters of which are much smaller than those of the [[Fe/H]]-R-e (or [[Fe/H]]-M-B) relations. The [[Fe/H]]-log sigma(0) relation is nearly parallel to the [Fe/H](0)-log sigma(0) relation but systematically lower by 0.3 dex; thus the mean metallicities are about one-half of the central values. The metallicity-mass relation or, equivalently, the color-magnitude relation of ellipticals holds not only for the central parts of galaxies but also for entire galaxies. Assuming that Mg-2 and Fe-1 give [Mg/H] and [Fe/H], respectively, we find [[Mg/Fe]] similar or equal to +0.2 in most of elliptical galaxies. [[Mg/Fe]] shows no correlation with galaxy mass tracers such as sigma(0), in contrast to what was claimed for the central [Mg/Fe]. This can be most naturally explained if the star formation had stopped in elliptical galaxies before the bulk of Type Ia supernovae began to occur. Elliptical galaxies can have significantly different metallicity gradients and [[Fe/H]], even if they have the same galaxy mass. This may result from galaxy mergers, but no evidence is found from presently available data to support the same origin for metallicity gradients, the scatters around the metallicity-mass relation, and dynamical disturbances. This may suggest that the scatters have their origin at the formation epoch of galaxies.Peer reviewe
Importance of transient resonances in extreme-mass-ratio inspirals
The inspiral of stellar-mass compact objects, like neutron stars or
stellar-mass black holes, into supermassive black holes provides a wealth of
information about the strong gravitational-field regime via the emission of
gravitational waves. In order to detect and analyse these signals, accurate
waveform templates which include the effects of the compact object's
gravitational self-force are required. For computational efficiency, adiabatic
templates are often used. These accurately reproduce orbit-averaged
trajectories arising from the first-order self-force, but neglect other
effects, such as transient resonances, where the radial and poloidal
fundamental frequencies become commensurate. During such resonances the flux of
gravitational waves can be diminished or enhanced, leading to a shift in the
compact object's trajectory and the phase of the waveform. We present an
evolution scheme for studying the effects of transient resonances and apply
this to an astrophysically motivated population. We find that a large
proportion of systems encounter a low-order resonance in the later stages of
inspiral; however, the resulting effect on signal-to-noise recovery is small as
a consequence of the low eccentricity of the inspirals. Neglecting the effects
of transient resonances leads to a loss of 4% of detectable signals.Comment: 24 pages, 12 figures, 2 appendices; changes to match published
versio
The Kardar-Parisi-Zhang equation in the weak noise limit: Pattern formation and upper critical dimension
We extend the previously developed weak noise scheme, applied to the noisy
Burgers equation in 1D, to the Kardar-Parisi-Zhang equation for a growing
interface in arbitrary dimensions. By means of the Cole-Hopf transformation we
show that the growth morphology can be interpreted in terms of dynamically
evolving textures of localized growth modes with superimposed diffusive modes.
In the Cole-Hopf representation the growth modes are static solutions to the
diffusion equation and the nonlinear Schroedinger equation, subsequently
boosted to finite velocity by a Galilei transformation. We discuss the dynamics
of the pattern formation and, briefly, the superimposed linear modes.
Implementing the stochastic interpretation we discuss kinetic transitions and
in particular the properties in the pair mode or dipole sector. We find the
Hurst exponent H=(3-d)/(4-d) for the random walk of growth modes in the dipole
sector. Finally, applying Derrick's theorem based on constrained minimization
we show that the upper critical dimension is d=4 in the sense that growth modes
cease to exist above this dimension.Comment: 27 pages, 19 eps figs, revte
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