Search results for " polar"

Surface plasmon interference excited by tightly focused laser beams

2007

International audience; We show that interfering surface plasmon polaritons can be excited with a focused laser beam at normal incidence to a plane metal film. No protrusions or holes are needed in this excitation scheme. Depending on the axial position of the focus, the intensity distribution on the metal surface is either dominated by interferences between counterpropagating plasmons or by a two-lobe pattern characteristic of localized surface plasmon excitation. Our experiments can be accurately explained by use of the angular spectrum representation and provide a simple means for locally exciting standing surface plasmon polaritons.

Nouveaux systèmes de contrôle de la polarisation de la lumière par effets non lineaires dans les fibres optiques

2013

This thesis deals with the work the development of an all-optical device for the control of the polarization state of light. Actually, this feature of light remains so far an uncontrolled variable, which can degrade the performances of all-optical systems. Based on nonlinear interaction between two counterpropagating waves inside an optical fiber, this device called polarization attractor allows to control the polarization state of light without polarization dependent losses.In a first part, we carry out extensive studies of the polarization attractor properties leading to the control and the regeneration of the polarization state of the 10-Gb/s NRZ and RZ telecommunication signals. Then, t…

3D acquisition system for transparent objects

2010

This thesis deals with a new automated tridimensional inspection system for transparent surfaces, based on polarization analysis. We first present an extension of the ‘Shape from Polarization’ method for transparent surfaces. After being reflected, an unpolarized light wave becomes partially linearly polarized, depending on the surface normal and on the refractive index of the media it impinges on. Hence, by measuring the polarization parameters of the reflected light, the surface normals are computed. The ambiguity concerning the normal orientation is solved here with a multispectral lighting system. Finally, the description of the whole acquisition prototype is given as well as some exper…

Using natural analogues to investigate the effects of climate change and ocean acidification on Northern ecosystems

2018

AbstractNorthern oceans are in a state of rapid transition. Still, our knowledge of the likely effects of climate change and ocean acidification on key species in the food web, functionally important habitats and the structure of Arctic and sub-Arctic ecosystems is limited and based mainly on short-term laboratory studies on single species. This review discusses how tropical and temperate natural analogues of carbonate chemistry drivers, such as CO2 vents, have been used to further our knowledge of the sensitivity of biological systems to predicted climate change, and thus assess the capacity of different species to show long-term acclimation and adaptation to elevated levels of pCO2. Natur…

X-Ray structure, Hirshfeld analysis and DFT studies of two new hits of triazolyl-indole bearing alkylsulfanyl moieties

2021

Two new hits of triazolyl-indole containing two different alkylsulfanyl analogues named tert-butyl 2-((4-amino-5-(1H-indol-2-yl)-4H-1,2,4-triazol-3-yl)thio)acetate 2, and ethyl 2-((4-amino-5-(1H-indol-2-yl)-4H-1,2,4-triazol-3-yl)thio)acetate 3 were synthesized via reaction of 4-amino-5-(1H-indol-2-yl)-1,2,4-triazol-3(2H)-thione 1 with tert-butyl bromoacetate and ethyl chloroacetate in the presence of base (Et3N). The molecular structure of 2, and 3 was confirmed by single-crystal X-ray diffraction and 1H/13C- NMR spectroscopic techniques. In compound 2, the molecular packing depends on significant O...H (9.3%), N...H (12.4%) and S...H (3.1%) as well as relatively weak C...H (14.1%), S...C (…

Artico nero. La lunga notte dei popoli dei ghiacci

2016

Sette storie da un Artico nero e morente, ambientate in Canada, nella Norvegia settentrionale, in Siberia, in Groenlandia: luoghi dove la distruzione di una cultura sta anticipando gli scenari peggiori. Un’analisi politica e sociale incassata nel modello romanzo-saggio. Un modo nuovo di raccontare e fare antropologia: antropofiction.

Pole-to-Pole Connections : Similarities between Arctic and Antarctic Microbiomes and Their Vulnerability to Environmental Change

2017

The global biogeography of microorganisms remains poorly resolved, which limits the current understanding of microbial resilience toward environmental changes. Using high-throughput 16S rRNA gene amplicon sequencing, we characterized the microbial diversity of terrestrial and lacustrine biofilms from the Arctic, Antarctic and temperate regions. Our analyses suggest that bacterial community compositions at the poles are more similar to each other than they are to geographically closer temperate habitats, with 32% of all operational taxonomic units (OTUs) co-occurring in both polar regions. While specific microbial taxa were confined to distinct regions, representing potentially endemic popul…

Sport and Quality of Life

2022

Negli ultimi trent’anni lo sport ha assunto un significato molto rilevante nella vita delle persone e, seppure con notevoli differenze, sia nei paesi a sviluppo economico avanzato, sia in quelli in via di sviluppo. A livello individuale, esso ha costituito un’area di investimento identitario quando ha assunto la forma di sport spettacolo del quale fruire, alimentando la pratica del tifo e il fandom o costituendo il modello di uno stile di vita vincente; ma anche quando ha assunto la forma di pratica del tempo libero attraverso la quale tenersi in forma, facendo crescere, in questo caso, la diffusione di una cultura della salute e del benessere. Si tratta di due modalità di approcciare al co…

Characterization of defect density states in MoOx for c-Si solar cell applications

Layers of MoOx have been deposited by thermal evaporation followed by post-deposition annealing (PDA). The density of states (DOS) distributions of the MoOx films were extracted deconvoluting the absorption spectra, measured by a phothermal deflection spectroscopy setup, including the small polaron contribution. Results revealed a sub-band defect distribution centered 1.1 eV below the conduction band; the amplitude of this distribution was found to increase with PDA temperature and film thickness.

First Measurement of the $Q^2$ Dependence of the Beam-Normal Single Spin Asymmetry for Elastic Scattering off Carbon

2018

We report on the first Q^{2}-dependent measurement of the beam-normal single spin asymmetry A_{n} in the elastic scattering of 570 MeV vertically polarized electrons off ^{12}C. We cover the Q^{2} range between 0.02 and 0.05  GeV^{2}/c^{2} and determine A_{n} at four different Q^{2} values. The experimental results are compared to a theoretical calculation that relates A_{n} to the imaginary part of the two-photon exchange amplitude. The result emphasizes that the Q^{2} behavior of A_{n} given by the ratio of the Compton to charge form factors cannot be treated independently of the target nucleus.