130,534 research outputs found
Well-posedness for a modified bidomain model describing bioelectric activity in damaged heart tissues
Get PDFWe prove the existence and the uniqueness of a solution for a modified bidomain model, describing the electrical behaviour of the cardiac tissue in pathological situations. The main idea is to reduce the problem to an abstract parabolic setting, which requires to introduce several auxiliary differential systems and a non-standard bilinear form.
The main difficulties are due to the degeneracy of the bidomain system and to its non-standard coupling with the diffusion equation
Homogenization of a modified bidomain model involving imperfect transmission
Get PDFWe study, by means of the periodic unfolding technique, the homogenization of a modified bidomain model, which describes the propagation of the action potential in the cardiac electrophysiology. Such a model, allowing the presence of pathological zones in the heart, involves various geometries and non-standard transmission conditions on the interface between the healthy and the damaged part of the cardiac muscle
Asymptotic analysis for non-local problems in composites with different imperfect contact conditions
Get PDFWe consider a composite material made up of a hosting medium containing an \eps-periodic array of perfect thermal conductors. Comparing with the previous contributions in the literature, in the present paper, the inclusions are completely disconnected and form two families with dissimilar physical behaviour. More specifically, the imperfect contact between the hosting medium and the inclusions
obeys two different laws, according to the two different types of inclusions.
The contact conditions involve the small parameter \eps and two positive constants \contuno,\contdue. We investigate the homogenization limit \eps\to 0 and the limits for \contuno,\contdue going to or , taken in any order, with the aim to find out the cases in which the two limits commute
Interface potential in composites with general imperfect transmission conditions
Get PDFThe model analyzed in this paper has its origins in the description of composites made by a hosting medium containing a periodic array of inclusions coated by a thin layer consisting of sublayers of two different
materials.
This two-phase coating material is such that the external part has a
low diffusivity in the orthogonal direction, while the internal one has high diffusivity along the tangential direction.
In a previous paper [14], by means of a concentration procedure, the internal layer was replaced by an imperfect interface.
The present paper is concerned with the concentration of the external coating layer and the homogenization, via the periodic unfolding method, of the resulting model, which is far from being a standard one.
Despite the fact that the limit problem looks like a classical Dirichlet problem for an elliptic equation, in the construction of the homogenized matrix and of the source term, a very delicate analysis is required
A degenerate pseudo-parabolic equation with memory
Get PDFWe prove the existence and uniqueness for a degenerate pseudo-parabolic problem with memory. This kind of problem arises in the study of the homogenization of some differential systems involving the Laplace-Beltrami operator and describes the effective behaviour of the electrical conduction in some composite materials
Well-posedness of two pseudo-parabolic problems for electrical conduction in heterogeneous media
Get PDFWe prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through
interfaces, which is mediated by a suitable Laplace-Beltrami type equation
Enantioselective synthesis of tetrafluorinated glucose and galactose
No full textPolyfluorinated carbohydrates have emerged as interesting probes to investigate “polar hydrophobicity” effect(s) in protein?carbohydrate interactions. A convenient enantioselective synthesis of tetrafluorinated analogues of two of the most important monosaccharides, d-glucose and d-galactose, is reported, as well as our first results regarding the glycosylation of these sugar analogues
Homogenization of a heat conduction problem with a total flux boundary condition
No full textWe study the overall thermal conductivity of a composite material obtained by inserting in a hosting medium an array of finely mixed inclusions made of perfect heat conductors.
The physical properties of this material are useful in applications and are obtained using the periodic unfolding method.
The peculiarity of this problem calls for a suitable choice of test functions in the unfolding procedure, which leads to a non-standard variational two-scale problem, that cannot be written in a strong form, as usual
MeSH term explosion and author rank improve expert recommendations
Get PDFInformation 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
Get PDFThe 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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