144 research outputs found
Semi-classical analysis of a random walk on a manifold
We prove a sharp rate of convergence to stationarity for a natural random
walk on a compact Riemannian manifold . The proof includes a detailed
study of the spectral theory of the associated operator.Comment: Published in at http://dx.doi.org/10.1214/09-AOP483 the Annals of
Probability (http://www.imstat.org/aop/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Gibbs/Metropolis algorithms on a convex polytope
This paper gives sharp rates of convergence for natural versions of the
Metropolis algorithm for sampling from the uniform distribution on a convex
polytope. The singular proposal distribution, based on a walk moving locally in
one of a fixed, finite set of directions, needs some new tools. We get useful
bounds on the spectrum and eigenfunctions using Nash and Weyl-type
inequalities. The top eigenvalues of the Markov chain are closely related to
the Neuman eigenvalues of the polytope for a novel Laplacian.Comment: 21 pages, 1 figur
Spectral Analysis of hypoelliptic random walks
We study the spectral theory of a reversible Markov chain associated to a
hypoelliptic random walk on a manifold M. This random walk depends on a
parameter h which is roughly the size of each step of the walk. We prove
uniform bounds with respect to h on the rate of convergence to equilibrium, and
the convergence when h goes to zero to the associated hypoelliptic diffusion
Random walk on surfaces with hyperbolic cusps
We consider the operator associated to a random walk on finite volume
surfaces with hyperbolic cusps. We study the spectral gap (upper and lower
bound) associated to this operator and deduce some rate of convergence of the
iterated kernel towards its stationary distribution.Comment: 28 page
The effect of university–industry collaboration on the scientific impact of publications : the Canadian case, 1980–2005
Previous research on university-industry collaboration in Canada concluded, using mean impact
factors as a proxy, that the scientific impact of such research is not inferior to that of university
research. Using field-normalized impact factors and citation counts, this paper reexamines the
Canadian case. It shows that, when impact factors are field-normalized, university-industry
papers are published, on average, in journals with lower impact factors than papers originating
from universities only. However, field-normalized citation values reveal the opposite: the average
scientific impact of university-industry papers is significantly above that of both university-only
papers and industry-only papers. Collaboration with industries is, thus far from detrimental to the
scientific impact of university research and even increases it significantly
Quality Control and Characterization of Scintillating Crystals for High Energy Physics and Medical Applications
Direct synthesis of mesoporous silica containing cobalt: A new strategy using a cobalt soap as a co-template
A novel approach to incorporate transition metals into porous structures is presented, which makes use of a cobalt soap in combination with the templating agent C16TMABr. An ordered mesoporous silica MCM-41 type material doped with Co is obtained after removal of the organic part by calcination. The a unit cell parameter of the cobalt containing mesoporous matrices is larger than that of pure MCM-41 and increases with the amount of cobalt present in the sample as well as the diameter of the pores. This is not observed when e.g. cobalt acetate is employed instead of the metal soap. The procedure presented establishes a new route for the incorporation of a transition metal into MCM-41 together with a tuning of the porous structure
Effects of a multifaceted intervention on cardiovascular risk factors in high-risk hypertensive patients: the ESCAPE trial, a pragmatic cluster randomized trial in general practice
BACKGROUND: Several observational studies on hypertensive patients have shown a gap between therapeutic targets recommended in guidelines and those achieved in daily practice. The ESCAPE trial aimed to determine whether a multifaceted intervention focused on general practitioners (GPs), could increase significantly the proportion of hypertensive patients at high risk in primary prevention who achieved all their recommended therapeutic targets. METHODS: A pragmatic, cluster randomized trial involving 257 GPs randomized by region. The GPs in the intervention group had a one-day training session and were given an electronic blood pressure measurement device and a short recommendation leaflet. Along with usual follow-up, they focused one consultation on hypertension and other cardiovascular risk factors every six months for two years. They also received feedback at baseline and at one year on their patients’ clinical and biological parameters. Main outcome measures were change in the proportion of patients achieving all their therapeutic targets and each individual therapeutic target at two years, and quality of life. RESULTS: 1,832 high-risk hypertensive patients were included. After two years, the proportion of patients achieving all their therapeutic targets increased significantly in both groups, but significantly more in the intervention group: OR (odds-ratio) 1.89, (95% confidence interval (CI) 1.09 to 3.27, P = 0.02). Significantly more patients achieved their blood pressure targets in the intervention group than in the usual care group: OR 2.03 (95% CI 1.44 to 2.88, P < 0.0001). Systolic and diastolic blood pressures decreased significantly more in the intervention group than in the usual care group, by 4.8 mmHg and 1.9 mmHg, respectively (P < 0.0001 for both). There were no significant difference changes in physical and mental quality of life between groups. CONCLUSION: An easy-to-perform, multifaceted intervention targeting only GPs increased significantly the proportion of high-risk hypertensive patients in primary prevention achieving their recommended therapeutic targets. TRIAL REGISTRATION: This trial was registered with ClinicalTrials.gov, number NCT0034885
Organized mesoporous solids: mechanism of formation and use as host materials to prepare carbon and oxide replicas
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