Snapshot Mueller matrix polarimeter by wavelength polarization coding

International audienceWe present a new, to the best of our knowledge, experimental configuration of Mueller matrix polarimeter based on wavelength polarization coding. This is a compact and fast technique to study polarization phenomena. Our theoretical approach, the necessity to correct systematic errors and our experimental results are presented. The feasibility of the technique is tested on vacuum and on a linear polarizer

Systematic errors specific to a snapshot Mueller matrix polarimeter

International audienceSystematic errors specific to a snapshot Mueller matrix polarimeter are studied. Their origins and effects are highlighted, and solutions for correction and stabilization are proposed. The different effects induced by them are evidenced by experimental results acquired with a given setup and theoretical simulations carried out for more general cases. We distinguish the errors linked to some imperfection of elements in the experimental setup from those linked to the sample under study

Two-channel snapshot Mueller matrix polarimeter

International audienceWe describe a new setup for a snapshot Mueller matrix polarimeter (SMMP). It relies on the separation and orthogonal polarization of two light beams by a Wollaston prism located at the setup output. The simultaneous treatment of the two spectra allows an enhancement of accuracy for real-time measurements through reduction of the effects caused by random noise and systematic errors. Moreover, it gives insight into the nonuniform spectral response of the medium under study. Experimental results support the feasibility of the proposed technique

Shoot and compound leaf comparisons in eudicots: dynamic morphology as an alternative approach

Recent developmental studies suggest that the compound leaf is a more or less incompletely developed shoot. Instead of considering leaves and shoots as non - homologous, this interpretation draws a continuum between leaves and shoots. This study considers the plant as a hierarchical series of units on which similar developmental processes are at work, and where each level (shoot, compound leaf, leaflet) is 'repeated' by the next higher level. Measurements related to the expression of developmental processes operating on leaves at the shoot level and on leaflets at the compound leaf level were used to determine if similar processes are at work at these different levels during early stages of organogenesis. Plants with compound leaves showing acropetal leaflet inception, representing a total 16 species from 10 eudicot families, were studied. Based on several types of quantitative analyses, there appears to be a continuum between so-called leaflets, compound leaves, and shoots in the species studied. This perspective, qualified as dynamic morphology, parallels the classical interpretation and is an alternative to it

Experimentally based simulations on modulated lidar for shallow underwater target detection and localization

14 pagesInternational audienceLight detection and ranging (LIDAR) is currently used for bathymetric measurement or underwater target detection. A new underwater-target detection scheme named modulated lidar was recently proposed. The study reported here deals with optimization of the modulation process to be applied under such detection conditions. A theoretical model was extracted from available experimental results by deconvolution and further used to simulate realistic backscattered signals for the development of a new modulation scheme. Then, an optimum set of amplitude modulation code parameters was obtained by maximizing the target signal-to-noise ratio. This paper will highlight some particularly promising waveform configurations

Yngre og ældre ældres risiko for selvmord efter deres partners død

Annette Erlangsen og Bernard Jeune: Risk of suicide among the old and oldest old after death of partner The purpose of this article is to examine the relation between civil status and the death of a partner and suicide among the oldest old (80 years and older) compared with younger age groups. The article also analyses whether the death of a partner exerts a temporal influence on the risk of suicide. The study includes information about the entire Danish population aged 50 years and over in the period 1994-1998. Suicide rates were analysed by civil status and age group, and the risk of suicide after the death of a partner was assessed by using “event-history analysis“. The highest rate of suicide was found among the oldest old for both men and women. However, the highest increase in risk after the death of a partner is found among people aged 65-79. The oldest old men who are either never married, divorced, or widowed have higher suicide rates than married men, while there is little difference between married and widowed women in this age group. Compared to married people, the relative risk of suicide increases significantly during the first year after the death of a partner. In the following years the risk levels off. The first months after the death of a partner are associated with an elevated risk for suicide. Measured relative to married persons, the suicide risk of recently bereaved men increases more than for women

Exceptional Lifespans

How long can humans live? This open access book documents, verifies and brings to life the advance of the frontier of human survival. It carefully validates data on supercentenarians, aged 110+, and semi-supercentenarians, aged 105-109, stored in the International Database on Longevity (IDL). The chapters in this book contribute substantial advances in rigorously checked facts about exceptional lifespans and in the application of state-of-the-art analytical strategies to understand trends and patterns in these rare lifespans. The book includes detailed accounts of extreme long-livers and how their long lifespans were documented, as well as reports on the causes of death at the oldest ages. Its key finding, based on the analysis of 1,219 validated supercentenarians, is that the annual probability of death is constant at 50% after age 110. In contrast to previous assertions about a ceiling on the human lifespan, evidence presented in this book suggests that lifespan records in specific countries and globally will be broken again and again as more people survive to become supercentenarians.

Yngre og ældre ældres risiko for selvmord efter deres partners død

Annette Erlangsen og Bernard Jeune: Risk of suicide among the old and oldest old after death of partner The purpose of this article is to examine the relation between civil status and the death of a partner and suicide among the oldest old (80 years and older) compared with younger age groups. The article also analyses whether the death of a partner exerts a temporal influence on the risk of suicide. The study includes information about the entire Danish population aged 50 years and over in the period 1994-1998. Suicide rates were analysed by civil status and age group, and the risk of suicide after the death of a partner was assessed by using “event-history analysis“. The highest rate of suicide was found among the oldest old for both men and women. However, the highest increase in risk after the death of a partner is found among people aged 65-79. The oldest old men who are either never married, divorced, or widowed have higher suicide rates than married men, while there is little difference between married and widowed women in this age group. Compared to married people, the relative risk of suicide increases significantly during the first year after the death of a partner. In the following years the risk levels off. The first months after the death of a partner are associated with an elevated risk for suicide. Measured relative to married persons, the suicide risk of recently bereaved men increases more than for women

Conception d'un filtre hyperfréquence analogique pour le traitement de données lidar modulé

National audienceLa détection sous-marine par méthode optique LIDAR (LIght Detection And Ranging) fait actuellement l'objet de nombreuses recherches. L'inconvénient majeur de cette technique est le fait que la rétrodiffusion volumique de l'eau de mer domine le signal provenant de la cible. L'utilisation d'un laser impulsionnel modulé en hyperfréquence, associé à un filtrage passe-bande à la réception, permet d'améliorer considérablement la détection. Le traitement actuel des données consistant en un filtrage numérique différé en temps donne des résultats concluants. En vu d'une intégration du système, le traitement en temps-réel des données devient une nécessité. Cet article porte sur la définition et la conception, au moyen de simulations numériques, des caractéristiques d'un filtre analogique passe-bande hyperfréquence pour le traitement de données issues d'un lidar modulé

Correlation between static and dynamic polarimetric properties and the texture of surface-stabilised ferroelectric liquid crystal cells

International audienceSnapshot Mueller matrix polarimetry was performed for static and dynamic analyses of surface-stabilised ferroelectric liquid crystal cells under an electric field. A strong correlation between the static (at fixed voltage) and dynamic (upon field reversal) polarimetric properties and the texture of ferroelectric liquid crystal cells was established. The birefringence properties were different between a rooftop/zigzag-textured cell and a stripe-textured cell. The trajectory of the optic axis, plotted over the transition between two addressed states, was analysed for each cell. The shape of the trajectories could be explained by a reversible motion of the smectic layers while switching