Scattering by cylinders with an arbitrary cross-section using domain decomposition and polynomial expansions.

In this paper, the electromagnetic field scattered by a cylinder with an arbitrary cross section is computed using a domain decomposition method in which the structure under consideration is enclosed with two fictitious circular cylinders. TE and TM polarizations are investigated. Our code is successfully validated by comparison with analytical results and with the finite element software COMSOL.

[Early detection of COPD in primary care: which tools?]. / Sujets à risque de BPCO en médecine générale: comment favoriser la réalisation de spirométries et la détection précoce de l'obstruction bronchique?

INTRODUCTION: The early diagnosis of COPD in general practice is not satisfactory. OBJECTIVES: To evaluate the impact of different diagnostic tools (Piko-6, Software) in general practice (GP). METHODS: A multicentre, randomised, controlled study in GP assessing the effect of the tested strategies on the rate of referrals for spirometry and the rate of detection of airflow obstruction. RESULTS: One thousand one hundred and three patients (55 years old, 60% males, 31 years of smoking habits) were included by 248 GP. The rates of referal to a pneumologist were significantly higher in the Software (50% of patients), and Piko/Software (47%) groups than in the Control (22%) and Piko groups (28%). A high proportion (44%) of lung function tests recommended by the GP were not performed, often because of patient refusal. The confirmation rates were lower in the Software and Piko/Software groups (47% and 43%, respectively) compared with the Piko and Control groups (68% and 79%, respectively). Concordance between PFT and Piko-6 for the diagnosis of airflow obstruction was poor (about 50%). CONCLUSIONS: The use of software in association or not with the Piko-6 was useful for GPs to identify patients to refer for further lung function testing, but did not improve the confirmation of the obstructive syndrome, mainly due to reluctance of patients to go on to have further lung function tests. The use of a diagnostic tool (software and/or mini-spirometry) does however seem to improve early COPD detection.

Disability related to COPD tool (DIRECT): towards an assessment of COPD-related disability in routine practice.

BACKGROUND: Chronic Obstructive Pulmonary Disease (COPD) is a worldwide public health concern. It is also a major source of disability that is often overlooked, depriving patients of effective treatments. This study describes the development and validation of a questionnaire specifically assessing COPD-related disability. METHODS: The DIsability RElated to COPD Tool (DIRECT) was developed according to reference methods, including literature review, patient and clinician interviews and test in a pilot study. A 12-item questionnaire was included for finalization and validation in an observational cross-sectional study conducted by 60 French pulmonologists, who recruited 275 COPD patients of stage II, III and IV according to the GOLD classification. Rasch modeling was conducted and psychometric properties were assessed (internal consistency reliability; concurrent and clinical validity). RESULTS: The DIRECT score was built from the 10 items retained in the Rasch model. Their internal consistency reliability was excellent (Cronbach's alpha = 0.95). The score was highly correlated with the Saint George's Respiratory Questionnaire Activity score (r = 0.83) and the London Handicap Scale (r = -0.70), a generic disability measure. It was highly statistically significantly associated to four clinical parameters (P < 0.001): GOLD classification, BODE index, FEV1 and 6-minute walk distance. CONCLUSION: DIRECT is a promising tool that could help enhance the management of COPD patients by integrating an evaluation of the COPD-related disability into daily practice.

Beam implementation in a nonorthogonal coordinate system: application to the scattering from random rough surfaces.

The C method is known to be one of the most efficient and versatile tools established for modeling diffraction gratings. Its main advantage is the use of a coordinate system in which the boundary conditions apply naturally and are, ipso facto, greatly simplified. In the context of scattering from random rough surfaces, we propose an extension of this method in order to treat the problem of diffraction of an arbitrary incident beam from a perfectly conducting (PEC) rough surface. For that, we were led to revisit some numerical aspects that simplify the implementation and improve the resulting codes.

Study of electromagnetic diffraction by curved strip gratings by use of the C-method.

The C-method is one of the most efficient and versatile methods designed for diffraction gratings. Its strength lies in the use of a coordinate system in which the surface of the grating coincides with a coordinate surface. The result is a great simplification in writing the boundary conditions. We exploit this simplification to treat the problem of diffraction from curved strip gratings, and we use the combined boundary conditions method that has been introduced for planar strip gratings and proved to be very efficient.

Localization of light in a lamellar structure with left-handed medium : the Light Wheel.

A rigorous analysis of the contra-directional coupling between a left-handed waveguide and a right-handed waveguide shows that such a structure supports twin modes with complex (conjugate) propagation constants. Using evanescent coupling or a source inside one of the waveguides, the twin modes can be excited. In this case, light rotates inside the lamellar structure forming an exotic mode : the light wheel. The structure can finally be seen as a new type of cavity and can be used for beam reshaping.

Light transmission by subwavelength square coaxial aperture arrays in metallic films.

Using the Fourier modal method, we study the enhanced transmission exhibited by arrays of square coaxial apertures in a metallic film. The calculated transmission spectrum is in good agreement with FDTD calculations. We show that the enhanced transmission can be explained when we consider a few guided modes of a coaxial waveguide.

Reformulation of the coordinate transformation method through the concept of adaptive spatial resolution. Application to trapezoidal gratings.

We reformulate the coordinate transformation method for profiles represented by parametric equations. Numerically, the eigenvalue problem is solved by expanding both the electromagnetic field and the periodic coefficients of Maxwell's equations into Fourier series. For trapezoidal gratings, it is shown that the convergence of the method is closely related to the representation of the profile. A proper choice of the representation permits handling profiles that previously had been out of reach owing to their sharp edges. From a practical point of view, we are now able to analyze gratings with two vertical facets by using the coordinate transformation method.

Rigorous and efficient grating-analysis method made easy for optical engineers.

The coordinate-transformation-based differential method of Chandezon et al. [J. Opt. (Paris) 11, 235 (1980); J. Opt. Soc. Am. 72, 839 (1982)] (the C method) is one of the simplest and most versatile methods for modeling surface-relief gratings. However, to date it has been used by only a small number of people, probably because, traditionally, elementary tensor theory is used to formulate the method. We reformulate the C method without using any knowledge of tensor, thus, we hope, making the C method more accessible to optical engineers.