2,506 research outputs found
Impact and Cost-Effectiveness of Point-Of-Care CD4 Testing on the HIV Epidemic in South Africa.
Rapid diagnostic tools have been shown to improve linkage of patients to care. In the context of infectious diseases, assessing the impact and cost-effectiveness of such tools at the population level, accounting for both direct and indirect effects, is key to informing adoption of these tools. Point-of-care (POC) CD4 testing has been shown to be highly effective in increasing the proportion of HIV positive patients who initiate ART. We assess the impact and cost-effectiveness of introducing POC CD4 testing at the population level in South Africa in a range of care contexts, using a dynamic compartmental model of HIV transmission, calibrated to the South African HIV epidemic. We performed a meta-analysis to quantify the differences between POC and laboratory CD4 testing on the proportion linking to care following CD4 testing. Cumulative infections averted and incremental cost-effectiveness ratios (ICERs) were estimated over one and three years. We estimated that POC CD4 testing introduced in the current South African care context can prevent 1.7% (95% CI: 0.4% - 4.3%) of new HIV infections over 1 year. In that context, POC CD4 testing was cost-effective 99.8% of the time after 1 year with a median estimated ICER of US$4,468/DALY averted. In healthcare contexts with expanded HIV testing and improved retention in care, POC CD4 testing only became cost-effective after 3 years. The results were similar when, in addition, ART was offered irrespective of CD4 count, and CD4 testing was used for clinical assessment. Our findings suggest that even if ART is expanded to all HIV positive individuals and HIV testing efforts are increased in the near future, POC CD4 testing is a cost-effective tool, even within a short time horizon. Our study also illustrates the importance of evaluating the potential impact of such diagnostic technologies at the population level, so that indirect benefits and costs can be incorporated into estimations of cost-effectiveness
Influence of Alternate Host Densities on Brown-Headed Cowbird Parasitism Rates in Black-Capped Vireos
Brown-headed Cowbird (Molothrus ater) parasitism is thought to be partly influenced by density of the host species, although tests of host density are relatively rare. We examined parasitism rates relative to the density of individual host species and densities of coexisting host species. We monitored 392 nests among coexisting host species and measured their densities among six habitats on Fort Hood Military Reservation, Texas during 1991-1992 to test the hypothesis that coexisting species affect parasitism rates in the endangered Black-capped Vireo (Vireo atricapillus). Black-capped Vireos and White-eyed Vireos (V. griseus) suffered three to four times higher cowbird parasitism than Northern Cardinals (Cardinalis cardinalis) or Painted Buntings (Passerina ciris). After controlling for removal of female cowbirds, which has been conducted on the study site since 1988, parasitism rates in Black-capped Vireos were positively correlated with cumulative host density in general, and Northern Cardinal density in particular. Only density of Northern Cardinals explained a significant amount of variation in parasitism rates in Black-capped Vireos among sites. We suggest that cowbirds may be attracted to conspicuous species, such as cardinals, and that high densities of such species may negatively affect coexisting species by increasing probabilities of being parasitized. Vireo nests were characterized by less nest concealment, greater canopy cover, and more stems than other species. However nest site and vegetation characteristics did not differ between parasitized and unparasitized nests for any species, suggesting habitat was unimportant to parasitism
The Sound of Sonoluminescence
We consider an air bubble in water under conditions of single bubble
sonoluminescence (SBSL) and evaluate the emitted sound field nonperturbatively
for subsonic gas-liquid interface motion. Sound emission being the dominant
damping mechanism, we also implement the nonperturbative sound damping in the
Rayleigh-Plesset equation for the interface motion. We evaluate numerically the
sound pulse emitted during bubble collapse and compare the nonperturbative and
perturbative results, showing that the usual perturbative description leads to
an overestimate of the maximal surface velocity and maximal sound pressure. The
radius vs. time relation for a full SBSL cycle remains deceptively unaffected.Comment: 25 pages; LaTex and 6 attached ps figure files. Accepted for
publication in Physical Review
Critical behavior and Griffiths effects in the disordered contact process
We study the nonequilibrium phase transition in the one-dimensional contact
process with quenched spatial disorder by means of large-scale Monte-Carlo
simulations for times up to and system sizes up to sites. In
agreement with recent predictions of an infinite-randomness fixed point, our
simulations demonstrate activated (exponential) dynamical scaling at the
critical point. The critical behavior turns out to be universal, even for weak
disorder. However, the approach to this asymptotic behavior is extremely slow,
with crossover times of the order of or larger. In the Griffiths region
between the clean and the dirty critical points, we find power-law dynamical
behavior with continuously varying exponents. We discuss the generality of our
findings and relate them to a broader theory of rare region effects at phase
transitions with quenched disorder.Comment: 10 pages, 8 eps figures, final version as publishe
A tracking algorithm for the stable spin polarization field in storage rings using stroboscopic averaging
Polarized protons have never been accelerated to more than about GeV. To
achieve polarized proton beams in RHIC (250GeV), HERA (820GeV), and the
TEVATRON (900GeV), ideas and techniques new to accelerator physics are needed.
In this publication we will stress an important aspect of very high energy
polarized proton beams, namely the fact that the equilibrium polarization
direction can vary substantially across the beam in the interaction region of a
high energy experiment when no countermeasure is taken. Such a divergence of
the polarization direction would not only diminish the average polarization
available to the particle physics experiment, but it would also make the
polarization involved in each collision analyzed in a detector strongly
dependent on the phase space position of the interacting particle. In order to
analyze and compensate this effect, methods for computing the equilibrium
polarization direction are needed. In this paper we introduce the method of
stroboscopic averaging, which computes this direction in a very efficient way.
Since only tracking data is needed, our method can be implemented easily in
existing spin tracking programs. Several examples demonstrate the importance of
the spin divergence and the applicability of stroboscopic averaging.Comment: 39 page
Statistical pairwise interaction model of stock market
Financial markets are a classical example of complex systems as they comprise
many interacting stocks. As such, we can obtain a surprisingly good description
of their structure by making the rough simplification of binary daily returns.
Spin glass models have been applied and gave some valuable results but at the
price of restrictive assumptions on the market dynamics or others are
agent-based models with rules designed in order to recover some empirical
behaviours. Here we show that the pairwise model is actually a statistically
consistent model with observed first and second moments of the stocks
orientation without making such restrictive assumptions. This is done with an
approach based only on empirical data of price returns. Our data analysis of
six major indices suggests that the actual interaction structure may be thought
as an Ising model on a complex network with interaction strengths scaling as
the inverse of the system size. This has potentially important implications
since many properties of such a model are already known and some techniques of
the spin glass theory can be straightforwardly applied. Typical behaviours, as
multiple equilibria or metastable states, different characteristic time scales,
spatial patterns, order-disorder, could find an explanation in this picture.Comment: 11 pages, 8 figure
Laterally driven interfaces in the three-dimensional Ising lattice gas
We study the steady state of a phase-separated driven Ising lattice gas in
three dimensions using computer simulations with Kawasaki dynamics. An external
force field F(z) acts in the x direction parallel to the interface, creating a
lateral order parameter current j^x(z) which varies with distance z from the
interface. Above the roughening temperature, our data for `shear-like' linear
variation of F(z) are in agreement with the picture wherein shear acts as
effective confinement in this system, thus supressing the interfacial
capillary-wave fluctuations. We find sharper magnetisation profiles and reduced
interfacial width as compared to equilibrium. Pair correlations are more
suppressed in the vorticity direction y than in the driving direction; the
opposite holds for the structure factor. Lateral transport of capillary waves
occurs for those forms of F(z) for which the current j^x(z) is an odd function
of z, for example the shear-like drive, and a `step-like' driving field. For a
V-shaped driving force no such motion occurs, but capillary waves are
suppressed more strongly than for the shear-like drive. These findings are in
agreement with our previous simulation studies in two dimensions. Near and
below the (equilibrium) roughening temperature the effective-confinement
picture ceases to work, but the lateral motion of the interface persists.Comment: 20 pages, 11 figures, submitted to Phys. Rev.
Glucocorticoid-induced hyperglycaemia and diabetes : call for action
Diabetes and hyperglycaemia are associated with increased morbidity and large healthcare and economic costs.1 Glucocorticoid-induced diabetes and hyperglycaemia are common. Glucocorticoids are used widely to treat people with inflammatory and autoimmune conditions,2 malignancies3 and in hospitalised patients with COVID-19.4 In the United Kingdom (UK), among hospitalised patients, the prevalence of glucocorticoid use is 10% in all patients5 and 25–40% in those with diabetes.6 This is associated with adverse metabolic outcomes including impaired glycaemic control7 and can manifest as a new-onset diabetes (glucocorticoid-induced diabetes) or worsening hyperglycaemia in people with diabetes (glucocorticoid-induced hyperglycaemia). The hypothesised mechanism for glucocorticoid-induced diabetes and hyperglycaemia is reduced insulin sensitivity and increased gluconeogenesis. Approximately 2% of all newly diagnosed diabetes cases in the United Kingdom are related to glucocorticoid use over a mean duration of 8.9 (±1.7) years.8 A meta-analysis by Liu et al.9 demonstrated that the incidence of glucocorticoid-induced diabetes and hyperglycaemia is 18.6% and 32.3%, respectively, over the period of 1–12 months. Patients from the included studies were adults in outpatient and inpatient settings treated with systemic glucocorticoids for a variety of indications including haematological malignancies, rheumatoid arthritis, pemphigus, pemphigoid, systemic lupus erythematosus, respiratory and neurological conditions.
The distortion of a cylinder with non-uniform axial heat conduction
Closed form expressions are developed for the thermoelastic curvature of the initially plane end faces of a traction free cylinder subjected to arbitrary axisymmetric heat flux, the curved surfaces being assumed insulated. The solution is developed from a potential function representation of displacement and temperature for an elastic layer. The reciprocal theorem is invoked to show that the tractions at the curved surface of the cylinder vary linearly along the axis and they are removed by superposition of biaxial bending. It is found that the curvature of the plane ends depends on the local heat flux and the mean heat flux, whilst the cylindrical face distorts into a cone.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42669/1/10659_2004_Article_BF00042521.pd
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