Return flux budget of polychromatic laser guide stars

The polychromatic laser guide star (PLGS) is one of the solutions proposed to extend the sky coverage by large telescopes to 100% by enabling a complete knowledge of all perturbation orders of the wavefront. The knowledge of the tip-tilt is deduced from the monitoring of the chromatic components of the PLGS, from 330 nm to the visible or near infrared. Here we study the original scheme to create the PLGS by resonant excitation of the mesospheric sodium by two pulsed lasers (tens of kilohertz repetition rate, tens of watts average power, tens of nanoseconds pulse duration), at 589 and 569 nm, respectively. The efficiency of this process is investigated numerically by means of both Bloch equation and rate equation models. The influence of numerous laser parameters is studied. In the best case, having optimized all laser parameters, the return flux at 330 nm should not exceed 7x10(4) photons/s/m2 for 2x18 W laser average power at the mesosphere. This maximum is obtained for a modeless laser whose spot diameter corresponds to 4 times the diffraction limit. For a diffraction-limited spot, the return flux falls down to 4x10(4)photons/s/m2.     

Polypyrrole oligosaccharide array and surface plasmon resonance imaging for the measurement of glycosaminoglycan binding interactions

In order to construct tools able to screen oligosaccharide-protein interactions, we have developed a polypyrrole-based oligosaccharide chip constructed via a copolymerization process of pyrrole and pyrrole-modified oligosaccharide. For our study, GAG (glycosaminoglycans) or GAG fragments, which are involved in many fundamental biological processes, were modified by the pyrrole moiety on their reducing end and then immobilized on the chip. The parallel binding events on the upperside of the surface can be simultaneously monitored and quantified in real time and without labeling by surface plasmon resonance imaging (SPRi). We show that electrocopolymerization of the oligosaccharide-pyrrole above a gold surface enables the covalent immobilization of multiple probes and the subsequent monitoring of their binding capacities using surface plasmon resonance imaging. Moreover, a biological application was made involving different GAG fragments and different proteins, including stromal cell-derived factor-1alpha (SDF-1alpha), interferon-gamma (IFN-gamma), and monoclonal antibody showing different affinity pattern.     

Natural organic matter (NOM) and pesticides removal using a combination of ion exchange resin and powdered activated carbon (PAC)

The combination of anion exchange resins (AERs) and powdered activated carbon (PAC) was studied to remove both natural organic matter (NOM) and pesticides. Experiments were conducted with high dissolved organic carbon (DOC) surface water (about 6.0mg DOC/L) spiked with both atrazine and isoproturon. AERs, like MIEX and IRA938, showed up to 75% removal of DOC after 30min contact time. The addition of PAC after treatment with these AERs only slightly decreased the residual DOC from 1.4 to 1.2mg/L. Experiments conducted with high (200microg/L) and low (1microg/L) initial pesticide concentrations showed that simultaneous and successive combinations of AER and PAC significantly improve the removal of both pesticides compared with PAC treatment on raw water. The improvement of short-term adsorption kinetics was explained by the adsorption of pesticides on AERs (about 5%) and the removal of high molecular weight (MW) NOM structures by AERs that reduce pore blockage phenomena. For 24h contact time with PAC (adsorption isotherms), the benefit of AER treatment was lower, which indicates that the refractory DOC to AER treatment still competes through direct site competition mechanism. MIEX resin had a distinct behavior since the simultaneous treatment with PAC showed no benefit on pesticide adsorption. The presence of fine residues of MIEX was shown to interfere with PAC adsorption.