Fire resistance of transport surfaces is a crucial aspect, especially in specific contexts such as road and railway tunnels in urban areas. In fact, tunnels are characterized by specific ...environmental and logistic conditions that make the consequences of a fire event severer. Furthermore, as far as bituminous mixes are concerned (flexible pavements, blankets for railways and rapid transit systems), the fire resistance of bituminous materials can have an outstanding role in terms of safety and security. Indeed, these materials burn at medium temperature (400– 500°C) and release toxic smokes. This fire behaviour makes bituminous pavements unsuitable for tunnel contexts. To this end, many studies tried to demonstrate that, by adding virgin flame-retardant additives, it is possible to improve the performance of bituminous pavements, in terms of mechanical properties and fire resistance. On the other hand, owing to the fact that a sustainable transportation surface needs to comply with environmental issues, meeting the needs of present-day users without compromising those of future generations, the use of recycled materials is becoming more and more relevant. In the light of the above premises, the objective of this study is to evaluate the effects of Reclaimed Extinguisher Powders (REP) on the performance of bituminous mixtures in urban transport surfaces. Fire resistance, mechanistic properties and environmental compatibility were considered. An experimental plan was designed and carried out. Results showed that the addition of REP can improve the fire resistance of asphalt binders and bituminous mixtures, without compromising mechanistic and environmental performance. Practical applications and perspectives in rehabilitation, maintenance, and research are outlined. Recommendations for future studies involving the application and
Phosphorus (P) is the limiting nutrient responsible for the development of algal blooms in freshwater bodies, adversely impacting the water quality of downstream lakes and rivers. Since agriculture ...is a major non-point source of P in southern Quebec, this study was carried out to investigate P transport under subsurface and naturally drained agricultural fields with two common soil types (clay loam and sandy loam). Monitoring stations were installed at four sites (A, B, C and D) in the Pike River watershed of southern Quebec. Sites A–B had subsurface drainage whereas sites C–D were naturally drained. In addition, sites A–C had clay loam soils whereas sites B–D had sandy loam soils. Analysis of data acquired over two hydrologic years (2004–2006) revealed that site A discharged 1.8 times more water than site B, 4 times more than site C and 3 times more than site D. The presence of subsurface drainage in sandy loam soils had a significant beneficial effect in minimizing surface runoff and total phosphorus (TP) losses from the field, but the contrary was observed in clay loam soils. This was attributed to the finding that P speciation as particulate phosphorus (PP) and dissolved phosphorus (DP) remained relatively independent of the hydrologic transport pathway, and was a strong function of soil texture. While 80% of TP occurred as PP at both clay loam sites, only 20% occurred as PP at both sandy loam sites. Moreover, P transport pathways in artificially drained soils were greatly influenced by the prevailing preferential and macropore flow conditions.
Adsorbate induced damping of the surface plasmon resonance in small noble particles was studied extending Persson's theory Surf. Sci. 281 (1993) 153 by taking into account the interband transitions ...in the dielectric function of the particles. The broadening and shift of the surface plasmon resonance caused by interface effects are significantly influenced by the interband transitions in the case of noble nanoparticles.
We develop and validate a nonlinear model for the current-driven dynamics of single-layer epitaxial islands on crystalline substrates. Simulations based on the model show that the dependence of the ...stable steady island migration speed vm on the inverse of the island size is not linear for larger-than-critical island sizes. In this nonlinear regime, we report morphological transitions, Hopf bifurcations, and instabilities for various surface crystallographic orientations and island misfit strains. Proper rescaling of vm gives a universal linear relationship for its dependence on island size.
Enzymatic biosensor reactions follow the Michaelis–Menten kinetics, coupled with diffusion. The diffusion reaction processes for amperometric enzyme biosensors have been simulated to explore the ...geometrical effects of nanowire array electrodes (NWAEs) and nanowire array stack electrodes (NWASEs) from the viewpoint of enhanced mass transport and increased reaction surface area in two limiting cases. For practical analysis considering sensor fabrication, most samples are assumed to have the same unit square (1cm×1cm) footprint. In the reaction-controlled case, the surface area increment improves the sensitivity regardless of electrode geometry. However, in the diffusion-controlled case, well-controlled NWAE or NWASE geometries as well as the increased surface area improve the sensitivity when the peak current at an early stage of the reaction is measured. Peak current engineering by adjusting the geometric parameters of NWAEs and NWASEs will result in a highly sensitive amperometric enzyme biosensor in the diffusion-controlled case. In contrast to previous micro- and nanoelectrode array studies, we investigated NWASEs representing entangled nanowire network electrodes, and report significant improvements in both limiting cases.
Treatment with ammonium sulfide ((NH
4)
2S
x
) solutions is used to produce model passivated InAs(0
0
1) surfaces with well-defined chemical and electronic properties. The passivation effectively ...removes oxides and contaminants, with minimal surface etching, and creates a covalently bonded sulfur layer with good short-term stability in ambient air and a variety of aqueous solutions, as characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and Hall measurements. The sulfur passivation also preserves the surface charge accumulation layer, increasing the associated downward band bending.
Simultaneous monitoring of ac and dc responses of the electrode-electrolyte interface with potentiodynamic electrochemical impedance spectroscopy (PDEIS) in silver underpotential and overpotential ...deposition on platinum has confirmed the role of intrinsic Pt surface changes in the irreversibility of Ag underpotential deposition and disclosed exceptionally high stability of Ag monolayer on Pt. PDEIS has been demonstrated to be a convenient means for wet surface chemistry monitoring.
Reflection energy electron loss spectra (REELS) have been measured for several metals and semiconductors (Be, Al, Si, V, Fe, Co, Ni, Cu, Ge, Mo, Pd, Te, Ta, W, Au, Pb) in the medium energy range ...(150–3400 eV) for normal incidence and an emission direction of 60° with respect to the surface normal. The ratio of the number of electrons that induced a surface excitation to the intensity of the elastic peak was extracted from each spectrum providing the so-called surface excitation parameter (SEP). This quantity is equal to the average number of surface excitations an electron experiences when it crosses the surface once. For the nearly free-electron materials the results agree reasonably with free-electron theory while significant deviations are observed for the other materials. In all cases the SEP is found to be inversely proportional to the speed of the probing particle. It is generally found that the surface excitation parameter decreases with the generalized plasmon energy. A simple predictive formula to estimate the surface excitation parameter for medium energy electrons entering or leaving an arbitrary material is proposed.
Recent progress in the development of microscopic four point probes permits surface-sensitive conductivity measurements on semiconductor surfaces. It is, however, not straightforward to extract the ...actual values for the surface and space-charge layer conductivity. Here we present an approach to data analysis which is based on numerical finite-element simulations. The results of such simulations are compared to the known analytical solutions for a collinear four point probe, and the approach is used to study the surface contribution to the conductivity of Si(111)(7×7). The procedure can also be used to study the influence of steps and other surface structures on the conductivity. This is illustrated by analysing the effect of mono-atomic steps on Si(111)(7×7). Finally, the potential benefits of collinear four point probe geometries with unequal contact spacings are discussed.
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