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P Lalanne

Publications and source records attributed to P Lalanne.

7 recordsLinked to original sources
PubMed2001

Use of grating theories in integrated optics.

Recently [Opt. Lett. 25, 1092 (2000)], two of the present authors proposed extending the domain of applicability of grating theories to aperiodic structures, especially the diffraction structures that are encountered in integrated optics. This extension was achieved by introduction of virtual periodicity and incorporation of artificial absorbers at the boundaries of the elementary cells of periodic structures. Refinements and extensions of that previous research are presented. Included is a thorough discussion of the effect of the absorber quality on the accuracy of the computational results, with highly accurate computational results being achieved with perfectly matched layer absorbers. The extensions are concerned with the diversity of diffraction waveguide problems to which the method is applied. These problems include two-dimensional classical problems such as those involving Bragg mirrors and grating couplers that may be difficult to model because of the length of the components and three-dimensional problems such as those involving integrated diffraction gratings, photonic crystal waveguides, and waveguide airbridge microcavities. Rigorous coupled-wave analysis (also called the Fourier modal method) is used to support the analysis, but we believe that the approach is applicable to other grating theories. The method is tested both against available numerical data obtained with finite-difference techniques and against experimental data. Excellent agreement is obtained. A comparison in terms of convergence speed with the finite-difference modal method that is widely used in waveguide theory confirms the relevancy of the approach. Consequently, a simple, efficient, and stable method that may also be applied to waveguide and grating diffraction problems is proposed.

Journal Article↗
PubMed2000

Numerical performance of finite-difference modal methods for the electromagnetic analysis of one-dimensional lamellar gratings

The numerical performance of a finite-difference modal method for the analysis of one-dimensional lamellar gratings in a classical mounting is studied. The method is simple and relies on first-order finite difference in the grating to solve the Maxwell differential equations. The finite-difference scheme incorporates three features that accelerate the convergence performance of the method: (1) The discrete permittivity is interpolated at the lamellar boundaries, (2) mesh points are located on the permittivity discontinuities, and (3) a nonuniform sampling with increased resolution is performed near the discontinuities. Although the performance achieved with the present method remains inferior to that achieved with up-to-date grating theories such as rigorous coupled-wave analysis with adaptive spatial resolution, it is found that the present method offers rather good performance for metallic gratings operating in the visible and near-infrared regions of the spectrum, especially for TM polarization.

Journal Article↗
PubMed2000

Blazed-binary diffractive elements with periods much larger than the wavelength

Blazed-binary optical elements with only binary ridges or pillars are diffractive components that mimic standard blazed-echelette diffractive elements. We report on the behavior of one-dimensional blazed-binary optical elements with local periods much larger than the wavelength. For this purpose, an approximate model based on both scalar and electromagnetic theory is proposed. The model is tested against electromagnetic-theory computational results obtained for one-dimensional blazed-binary gratings with large periods. An excellent agreement is obtained, showing that the model is able to predict quantitatively the wavelength and the incidence-angle dependences of the diffraction efficiency of blazed-binary structures.

Journal Article↗
PubMed1996

Loss of the nocturnal decline in blood pressure in subjects with essential hypertension and microalbuminuria.

BACKGROUND: Microalbuminuria, a marker of early renal damage, predicts mortality in non-diabetic subjects. The loss of circadian blood pressure regulation is associated with the severity of essential hypertension and has been reported in hypertension due to renal disease. We therefore looked for a possible link between microalbuminuria and the smaller decrease in nocturnal blood pressure that occurs in essential hypertension.METHODS: The 24 h ambulatory blood pressure of 52 subjects with essential hypertension was measured and their urine tested for microalbuminuria (urinary albumin excretion of 30-300 mg/24 h). RESULTS: The subjects with (n = 10) and without (n = 42) microalbuminuria were comparable in clinical characteristics, antihypertensive treatments and serum creatinine. They had significantly different night-time systolic, diastolic and mean blood pressure decreases on ambulatory blood pressure monitoring. Two-factor analysis of variance showed that the day-night blood pressure decrease was linked to microalbuminuria status. The day-night blood pressure change of subjects with microalbuminuria differed from that of subjects without microalbuminuria independently from the daytime blood pressure level. CONCLUSION: Subjects with essential hypertension and microalbuminuria show a loss of nocturnal blood pressure decline. Whether microalbuminuria indicates a subtype of essential hypertension due to renal disease or severe hypertension with early renal damage remains to be clarified.

Journal Article↗
PubMed1996

[Decrease of nocturnal blood pressure in type II diabetic subjects with microalbuminuria].

The aim of this study was to evaluate the circadian blood pressure variations in subjects with or without microalbuminuria (Urinary Albumin Excretion (UAE) between 30 and 300 mg/24 h. Forty-nine non-insulin dependent diabetic subjects with essential arterial hypertension and without proteinuria (UAE < 300 mg/24 h) were consecutively recruited. Systolic (SBP) and Diastolic Blood Pressure (DBP) have been measured using a SpaceLabs 90207 ambulatory blood pressure monitor, every 15 minutes during daytime (7:00 a.m. to 22:00 p.m.) and every 30 minutes during nighttime (22:00 p.m. 7:00 a.m.). UAE has been measured by nephelometry on three 24 h urine collections. The group with microalbuminuria (n = 16) was not different from the group with normoalbuminuria (n = 33) for age, sex ratio, body mass index, known diabetes duration, proportion of anti-hypertensive treatment, serum creatinine and HbA1c. Daytime blood pressures (SBP/DBP: 144 +/- 15/83 +/- 8 vs 137 +/- 13/84 +/- 9 mmHg) and nighttime DBP (75 +/- 7 vs 74 +/- 9 mmHg) were comparable between both groups. In contrast, the nighttime SBP was higher in subjects with microalbuminuria than in those without (139 +/- 17 vs 129 +/- 17 mmHg; p = 0.016). If dippers are the subjects with a nocturnal blood pressure reduction (SBP and/or DBP) below 4%, there is a relationship between "non dippler" subjects and those with microalbuminuria (Chi-squared test = 5.67; p = 0.017). In conclusion, hypertensive non-insulin dependent diabetic subjects with microalbuminuria have a loss of nocturnal blood pressure decrease.

Aged↗
PubMed1975

[The problem of selection of monographs].

The problem of selecting the monographs to be inserted in a pharmacopoeia does not actually exist on a national, but only on an international scale, as was realized during the compilation of the European Pharmacopoeia. The problems encountered at that time are discussed here. The first section of this paper describes the various principles, ideas and interpretations that are at the root of the divergent opinions expressed by the delegations at Strasbourg in facing this problem each time it comes up for discussion. These divergent opinions are centered mainly on the following: -developments and progress in the pharmaceutical profession; -differences existing among various national legislations; -basic concepts concerning pharmacopoeias; -more or less broad interpretations of the obligations set down in the Convention and in the General Rules of the European Pharmacopoeia; that is, in essence, the principle of the possibility of opposing the monographs and the application of this principle. On the basis of these considerations, the author advances, and tries to justify, the criteria that, according to him, should be adopted in order to arrive at common rules. The criteria are the following: -therapeutic interest, provided it is medically confirmed; -importance of usage, under the four specific aspects to be considered. On the subject of a new substance: -necessity that the product be produced by several manufacturers; there are three cases, where the rules to be observed have not been obeyed by all concerned. -obligation that the product be marketed in bulk, except in cases specifically established. While making this report, the author intends to emphasize the fact that a great effort is needed in order to narrow the gap separating certain points of view.

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