Bronchial hyperreactivity and spirometric impairment in patients with allergic rhinitis.

Background: The Link between allergic rhinitis and asthma is well known. Bronchial hyperreactivity (BHR) may be present in rhinitics. The present study is aimed at evaluating a large group of subjects suffering from allergic rhinitis alone to investigate the presence of spirometric impairment and BHR both during and outside the pollen season. Methods: 360 rhinitics (subdivided in 3 groups: seasonal, SAR, perennial, PAR, and polysensitized, PolysR) were investigated by spirometry and methacholine challenge. Results: There was a significant seasonal difference concerning the number of rhinitics with impaired FEV1 (p<0.01 for SAR, p<0.02 for PAR, and p<0.03 for PolysR) and FEF25-75 (p<0.05 for SAR, p<0.03 for PAR, and p<0.05 for PolysR) as well as with BHR (p<0.05 for SAR and p<0.03 for PAR). Conclusions: This study evidences that an impairment of spirometric parameters and BHR may be observed in patients with allergic rhinitis alone. Thus, careful evaluation of lower airways should be performed in patients with allergic rhinitis alone

Comparison of reduction methods for finite element geometrically nonlinear beam structures

The aim of this contribution is to present numerical comparisons of model-order reduction methods for geometrically nonlinear structures in the general framework of finite element (FE) procedures. Three different methods are compared: the implicit condensation and expansion (ICE), the quadratic manifold computed from modal derivatives (MD), and the direct normal form (DNF) procedure, the latter expressing the reduced dynamics in an invariant-based span of the phase space. The methods are first presented in order to underline their common points and differences, highlighting in particular that ICE and MD use reduction subspaces that are not invariant. A simple analytical example is then used in order to analyze how the different treatments of quadratic nonlinearities by the three methods can affect the predictions. Finally, three beam examples are used to emphasize the ability of the methods to handle curvature (on a curved beam), 1:1 internal resonance (on a clamped-clamped beam with two polarizations), and inertia nonlinearity (on a cantilever beam)

Comparison of nonlinear mappings for reduced-order modelling of vibrating structures: normal form theory and quadratic manifold method with modal derivatives

The objective of this contribution is to compare two methods proposed recently in order to build efficient reduced-order models for geometrically nonlinear structures. The first method relies on the normal form theory that allows one to obtain a nonlinear change of coordinates for expressing the reduced-order dynamics in an invariant-based span of the phase space. The second method is the modal derivative (MD) approach, and more specifically the quadratic manifold defined in order to derive a second-order nonlinear change of coordinates. Both methods share a common point of view, willing to introduce a nonlinear mapping to better define a reduced-order model that could take more properly into account the nonlinear restoring forces. However the calculation methods are different and the quadratic manifold approach has not the in variance property embedded in its definition. Modal derivatives and static modal derivatives are investigated, and their distinctive features in the treatment of the quadratic nonlinearity is underlined.Assuming a slow/fast decomposition allows understanding how the three methods tend to share equivalent properties. While they give proper estimations for flat symmetric structures having a specific shape of nonlinearities and a clear slow/fast decomposition between flexural and in-plane modes, the treatment of the quadratic nonlinearity makes the predictions different in the case of curved structures such as arches and shells. In the more general case, normal form approach appears preferable since it allows correct predictions of a number of important nonlinear features,including for example the hardening/softening behaviour, whatever the relationships between slave and master coordinates are