1,721,015 research outputs found
Some Weighted Isoperimetric Problems on with Stable Half Balls Have No Solutions
No full textWe show the counter-intuitive fact that some weighted isoperimetric problems on the half-space , for which half-balls centered at the origin are stable, have no solutions.
A particular case is the measure , with . Some results on stability and nonexistence for weighted isoperimetric problems on are also obtained
Isoperimetric estimates for the first eigenfunction of a class of linear elliptic problem
No full textWe find some optimal estimates for the first eigenfunction of a class of elliptic equations whose prototype is - (gamma u(xi)) (xi) = lambda gamma u in Omega subset of R-n with Dirichlet boundary condition, where gamma is the normalized Gaussian function in R-n. To this aim we make use of the Gaussian symmetrization which transforms a domain into an half-space with the same Gaussian measure. The main tools we use are the properties of the weighted rearrangements and in particular the isoperimetric inequality with respect to Gaussian measure
Isoperimetric estimate for the first eigenfunction of a class of linear elliptic problems
No full textA sharp estimate for Neumann eigenvalues of the Laplace-Beltrami operator for domains in a hemisphere
Full text linkHere, we prove an isoperimetric inequality for the harmonic mean of the first N - 1 non-trivial Neumann eigenvalues of the Laplace-Beltrami operator for domains contained in a hemisphere of N
Integrating modelling of maintenance policies within a stochastic hybrid automaton framework of dynamic reliability
Full text linkThe dependability assessment is a crucial activity for determining the availability, safety and maintainability of a system and establishing the best mitigation measures to prevent serious flaws and process interruptions. One of the most promising methodologies for the analysis of complex systems is Dynamic Reliability (also known as DPRA) with models that define explicitly the interactions between components and variables. Among the mathematical techniques of DPRA, Stochastic Hybrid Automaton (SHA) has been used to model systems characterized by continuous and discrete variables. Recently, a DPRA-oriented SHA modelling formalism, known as Stochastic Hybrid Fault Tree Automaton (SHyFTA), has been formalized together with a software library (SHyFTOO) that simplifies the resolution of complex models. At the state of the art, SHyFTOO allows analyzing the dependability of multistate repairable systems characterized by a reactive maintenance policy. Exploiting the flexibility of SHyFTA, this paper aims to extend the tools’ functionalities to other well-known maintenance policies. To achieve this goal, the main features of the preventive, risk-based and condition-based maintenance policies will be analyzed and used to design a software model to integrate into the SHyFTOO. Finally, a case study to test and compare the results of the different maintenance policies will be illustrated
A model of cytotoxic T antitumor activation stimulated by pulsed dendritic cells
No full textWe present a preliminary ODE model to sketch the immune response of cytotoxic T cells against cancer through the use of pulsed autologous dendritic cells. The model is partially based on data coming from experiments that are presently in progress in the wet lab of our collaborators, but it can be applied in principle to different tumors. To this end, we show the immune response of cytotoxic T cells stimulated by autologous dendritic cells for different cancers
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