130,374 research outputs found
Existence, multiplicity and stability of endemic states for an age-structured S-I epidemic model
No full textWe study an S--I type epidemic model in an age-structured population, with mortality due to the disease. A threshold quantity is found that controls the stability of the
disease-free equilibrium and guarantees the existence of an
endemic equilibrium. We obtain conditions on the age-dependence of the susceptibility to infection that imply the uniqueness of the endemic equilibrium. An example with two
endemic equilibria is shown. Finally, we analyse numerically how the stability of the endemic equilibrium is affected by the extra-mortality and by the possible periodicities induced by
the demographic age-structure
Multiplicity and nondegeneracy of positive solutions to quasilinear equations on compact Riemannian manifolds
No full textWe consider a compact, connected, orientable, boundaryless Riemannian manifold (M, g) of class C∞ where g denotes the metric tensor. Let n = dim M ≥ 3. Using Morse techniques, we prove the existence of nonconstant solutions u H1,p(M) to the quasilinear problem (P-epsilon) left{{egin{array}{@{}l@{}} -epsilon^p Delta-{p,g} u +u^{p-1}=u^{q-1}, \u>0,end{array}}
ight for ε > 0 small enough, where 2 ≤ p < n, p < q < p∗, p∗= np/(n - p) and is the p-laplacian associated to g of u (note that Δ2,g = Δg) and denotes the Poincaré polynomial of M. We also establish results of genericity of nondegenerate solutions for the quasilinear elliptic problem (Pε)
An Eigenvalue Problem for a Quasilinear Elliptic Field Equation on R^N
No full textWe study the field equation
on , with positive parameter.
The function is singular in a point and so the configurations are characterized
by a topological invariant: the topological charge.
By a min-max method, for sufficiently small, there
exists a finite number of solutions
of the eigenvalue problem for any given charge
On the number of blowing-up solutions to a nonlinear elliptic equation with critical growth
No full textIn this paper we estimate the number of solutions to -Delta w + V(x)w = n(n - 2)w((n+2)/(n-2)-is an element of) in R-n w > 0 in R-n w is an element of D-1,D-2 (R-n) which blow tip at a suitable critical point of the potential V as the parameter is an element of goes to zero
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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