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

Comparative analysis of surface roughness algorithms for the identification of active landslides

Parameters correlated to surface roughness are quite commonly used to describe landslide activity in quantitative geomorphology. Previous studies proved that topographic roughness is closely related to both landslide mechanics and features. A number of different techniques have emerged over the years to describe quantitatively the great variety of landforms and processes that affect unstable slopes. In this work we perform a comparative analysis of several methods used in literature to compute surface roughness (root mean square applied to elevation and slope grids, eigenvalue ratios, semivariance, discrete Fourier transform, continuous wavelet transform and wavelet lifting scheme) in order to evaluate quantitatively which algorithms are best suited to discriminate active landslides and to predict them for automated mapping purposes. A first test was carried out on artificial surfaces simulating different roughness patterns encountered in nature, so to highlight advantages and limits in controlled conditions. Then, the algorithms were applied to LiDAR datasets of two earth flow case studies in the Northern Apennines, Italy. Results obtained by using \u201ceffect-size\u201d statistical test to objectively quantify the capability of the different algorithms of discriminating active landslide slopes from other slope types showed that most algorithms perform reasonably well and that simple techniques (RMS-based, wavelet lifting scheme) achieve equal or sometimes even better results that more complex ones. Results from the use of roughness indexes for the prediction of landslide slopes in automated mapping showed that non-forested active slopes could be predicted by most methods with an accuracy greater than 85% and that most methods had a 15% drop in prediction accuracy in forested active slopes. Results also proved that increasing the size of the moving window has minor beneficial effects in predictive capability, suggesting that small size of pixels and moving windows should be used to retain a full resolution of surface conditions in slopes

SLOWMOVE - A numerical model for the propagation of slow-moving landslides: issues and theoretical concepts

Gravitational flows characterized by low velocities represent widely-spread and costly geological hazard and pose particular challenges for the development of a representative numerical model. In many cases their behavior depends on complex mechanical and fluid interactions. The development of a physical-based numerical simulation that allows for an accurate model of observed landslide motion is particularly challenging and underlies a number of assumptions and simplifications. Many conventional techniques do not take hydromechanical effects into account or include the inertia of the moving mass which may result in an overestimation of velocities of the flowing materials

SLOWMOVE – A numerical model for the propagation of slow-moving landslides: a 1D approach and its application to the analysis of the Valoria landslide (Apennines, Italy)

Understanding the behavior of landslides often starts with a numerical simulation that accurately accounts for observed physical processes. This research proposes a method for the implementation of the dynamic SLOWMOVE model to a high-mobility, moderate velocity earth flow located in the northern Apennines. The Valoria landslide is 3.5 km long earth slide- earth flow that resumed activity in 2001. Landslide materials comprised of disaggregated Flysch, Marl and Claystones are mainly transported as earth slides in the upper slope, and as earth flows in the main track. Repeated acceleration events lasting several weeks occur seasonally since 2001 reactivation. During events it can reach velocities of about 10 m per hour with a cumulative displacement of hundreds of meters. Through this intermittent activity, more than ten million cubic meters have been transferred down-slope since 2001, changing significantly and several times the morphology of the slope

Testing different concepts of the equations of motion, describing runouttime and distance of slow-moving gravitational slides and flows

The kinematics of rapid and slow moving landslides is commonly described by equations of motion, which in case of a viscous component are based on the Navier-Stokes equation. They consist of inertial terms related to the change in velocity in time (local acceleration) and space (convective acceleration) and terms related to respectively the gravity, pressure and viscous forces. These viscous resistance forces in the mass balance can be accompanied or replaced by other rheological (frictional and cohesive) terms depending on the liquid/solid ratio of the moving mass

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