Nonlinear resonance reflection from and transmission through a dense glassy system built up of oriented linear Frenkel chains: two-level models

A theoretical study of the resonance optical response of assemblies of oriented short (as compared to an optical wavelength) linear Frenkel chains is carried out using a two-level model. We show that both transmittivity and reflectivity of the film may behave in a bistable fashion and analyze how the effects found depend on the film thickness and on the inhomogeneous width of the exciton optical transition.Comment: 26 pages, 9 figure

Nanoscale control of Ag nanostructures for plasmonic fluorescence enhancement of near-infrared dyes

Potential utilization of proteins for early detection and diagnosis of various diseases has drawn considerable interest in the development of protein-based detection techniques. Metal induced fluorescence enhancement offers the possibility of increasing the sensitivity of protein detection in clinical applications. We report the use of tunable plasmonic silver nanostructures for the fluorescence enhancement of a near-infrared (NIR) dye (Alexa Fluor 790). Extensive fluorescence enhancement of ∼2 orders of magnitude is obtained by the nanoscale control of the Ag nanostructure dimensions and interparticle distance. These Ag nanostructures also enhanced fluorescence from a dye with very high quantum yield (7.8 fold for Alexa Fluor 488, quantum efficiency (Qy) = 0.92). A combination of greatly enhanced excitation and an increased radiative decay rate, leading to an associated enhancement of the quantum efficiency leads to the large enhancement. These results show the potential of Ag nanostructures as metal induced fluorescence enhancement (MIFE) substrates for dyes in the NIR “biological window” as well as the visible region. Ag nanostructured arrays fabricated by colloidal lithography thus show great potential for NIR dye-based biosensing applications

Impact du développement urbain sur les villes traditionnelles au Maroc (exemple de Fès)

AMIENS-BU Lettres (800212104) / SudocSudocFranceF

Coupling geomorphic field observation and Lidar derivatives to map complex landslides

High resolution LiDAR DEMs from regional or site specific surveys were used to map complexlandslides such as deep-seated rockslides and earth slides-earth flows. Regional surveys DEMs wereused to produce shaded relief maps that allowed delimiting rock slide units and sub-units at the slope scale.Multitemporal site-specific survey DEMs were used in eath slides-earth flows case studies to derive roughnessmaps that allowed defining the curvature fingerprint of the most active parts of earth flows, and to derivedifferential elevation maps that allowed assessing depletion and accumulation areas occurring in the slope asa consequence of post-failure dynamics

Using Lidar to define roughness fingerprint and displacement of earth flows

When confronted with earth \ufb02ows, \ufb01eld surveyors base their assessment of the state of activity of the landslide by performing (often unconsciously) a subjective, expert-based estimate of small scale topographic roughness. The general assumption is that the higher is the movement, the higher is terrain roughness. De\ufb01ning the roughness \ufb01ngerprint of dormant and active earth \ufb02ows using Lidar data from local surveys, could contribute, in perspective, to develop routines for semi automatic detection of landslides from large regional datasets, and for evaluating their degree of activity. Differential DEMs are only capable of detecting elevation changes related to depletion or accumulation, but not movements. Image correlation techniques might be used on Lidar data to estimate 3D displacement vectors, an information that cannot be retrieved by simple DEM subtraction. The validation of this approach could provide an added value to the use of multitemporal Lidar on active earth \ufb02ows. In this research we considered dormant and active earth \ufb02ows for which multitemporal local-scale Lidar surveys were available. Surveys contained an average of 4 to 6 pt/sqm classi\ufb01ed as ground. Several different roughness calculation methods (Slope Curvature Kernel 3x3, RMS height, RMS deviation, Hurst exponent, Flatness and Organization strength)were applied to 0.2 m rasters obtained by point-cloud interpolation. Results showd that the difference between active and dormant landslides is evident in most cases and that long-time dormant landslides are less easily discernable from stable areas than from active ones. However, results also demonstrated that roughness is highly variable within the same landslide, that the correlation with the measured rates of movement is not always straightforward and that different roughness estimate methods can provide partly contradictory results. Multitemporal Lidar surveys have been also analysed to generate displacement maps.. The use of Image Correlation techniques was found to be rather complex, raising many problems concerning point cloud densities, lidar-noise, subpixel correlation, change of morphology patterns, judging of miss-correlations. However, when compared with displacement vectors obtained by supervised analysis of shaded reliefs or by independent monitoring methods, preliminary results obtained so far are somehow promising. The activities reported in this abstract are part of research project WISELAND (Integrated Airborne and Wireless Sensor Network systems for Landslide Monitoring) funded by the Italian Ministry of Research (2007-2009) and Marie Curie Project \u201cMOUNTAIN RISKS\u201d funded by the EU (2006-2010

Continuous crossover from two dimensional to one dimensional electronic properties for metallic silicide nanowires

In a joint experimental and theoretical study on metallic TbSi2 nanowires, we observe a continuous crossover from a two-dimensional (2D) to a quasi-one-dimensional (1D) electronic structure by reduction of the nanowire width. The nanowires were grown by self-organization on vicinal Si(111) substrates denoted by the Miller indices (hhk). Their electronic structure was analyzed by angle-resolved photoemission spectroscopy (ARPES) and calculated using density functional theory (DFT). In ARPES, the TbSi2 nanowires show basically the 2D electronic structure of the TbSi2 film on planar Si(111) with an increasing momentum broadening for decreasing nanowire widths, consistent with Heisenberg's uncertainty principle. In contrast, DFT calculations predict a purely 1D electronic structure for TbSi2 nanowires. Unfolding this 1D electronic structure onto the Brillouin zone of the TbSi2 film leads to a Fermi surface appearing similar to the one of the 2D TbSi2 film, but with an additional 1D contribution from nanowire edges. Such an additional 1D signature is also observed in ARPES for narrow nanowires. These results indicate a continuous transition to a 1D electronic structure for decreasing nanowire widths

The Biocompatibility Analysis of Artificial Mucin-Like Glycopolymers

The ocular surface is covered by a tear film consisting of an aqueous/mucin phase and a superficial lipid layer. Mucins, highly O-glycosylated proteins, are responsible for lubrication and ocular surface protection. Due to contact lens wear or eye disorders, lubrication of the ocular surface can be affected. Artificial glycopolymers which mimic natural mucins could be efficient in ophthalmic therapy. Various neutral, positively, and negatively charged mucin-mimicking glycopolymers were synthesized (n = 11), cultured in different concentrations (1%, 0.1%, and 0.01% w/v) with human corneal epithelial cells (HCE), and analyzed by various cytotoxicity/viability, morphology, and immunohistochemistry (IHC) assays. Six of the eleven glycopolymers were selected for further analysis after cytotoxicity/viability assays. We showed that the six selected glycopolymers had no cytotoxic effect on HCE cells in the 0.01% w/v concentration. They did not negatively affect cell viability and displayed both morphology and characteristic markers as untreated control cells. These polymers could be used in the future as mucin-mimicking semi-synthetic materials for lubrication and protection of the ocular surface