Surface quenching

Several types of testing were employed to evaluate the bactericidal efficacies of the coated substrates. Five of the coatings on circular glass cover-slips (12 mm diameter) were challenged with the bacterium Staphylococcus aureus (ATCC 6538). This was accomplished by adding a 50- jlL suspension of 10 CFU S. aureus to the surface of each sample. At predetermined contact times a 25- jlL aliquot was removed from the surface, quenched with sterile 0.02 N sodium thiosulfate, and plated on nutrient agar. The viable bacterial colonies were then counted after 48 h incubation at 37°C. Fabric samples were tested by two methods. In one, small squares (1.0-1.5 cm) were placed on a Tryptic Soy agar plate that was inoculated... 

In the simplest version of a surface reaction, the rate of termination of the chain reaction by reaction of R on a surface should be proportional to D, the square of the vessel diameter We will also leave this calculation for a homework problem, but the imphcations are profound for a chain reaction. When the vessel size increases, the rate of a chain reaction can increase drastically, from a slow surface-quenched process in small vessels to very fast process whose only quenching steps are homogeneous reactions. 

One example of half-space diffusion is the cooling of an oceanic plate. The oceanic plate when created at the mid-ocean ridge is hot, with a roughly uniform temperature of about 1600 K. It is cooled at the surface (quenched by ocean water) as it moves away from the ocean ridge. For simplicity, ignore complexities... 

In Figure 16.3, the excitation / relaxation electric fields that can interact with organic semiconductor are from the incident light field (E) and metal field (Em) for excitation and near metal surface quenching of non-radiative decay rates the radiative decay rate (F), metal radiative rate (F,), and metal radiative decay rate... 

Increasing the strength of glass articles by compression strain in the glass surface (quenching, ion exchange)... 

Figure 6-23. Concentration of nitrogen oxides generated in thermal air plasma with surface quenching as a function of flow enthalpy. Gas pressure 1 atm triangles correspond to experimental installation, circles to industrial installation.

Gradeck, M., Ouattara, A., Maillet, D., Gardin, P., Lebouche, M. (2011). Heat transfer associated to a hot surface quenched by a jet of oil-in-water emulsion. Experimental Thermal and Fluid Science, 35, 841-847. 

Fluorescence (which is a special case of luminescence) in the vicinity of plas-monic metal can be both surface-enhanced and surface-quenched (Weitz et al. 1983). The fluorescence is a stepwise process involving first absorption which is enhanced by EM mechanism. For the second step (emission), the presence of metal... 

An additional effect to consider for SERRS is that of the fluorescence which can occur simultaneously with a RRS process. This is the so-called delayed fluorescence, " which is a radiative decay process for molecules which have relaxed from their initial excited vibrational state of the excited electronic state to the lowest vibrational level of the excited state. Delayed fluorescence can be additionally damped on a rough Ag surface for the same reasons that the RRS process is additionally damped, i.e., by coupling to the surface plasmon resonances. On the other hand, the electromagnetic enhancement factors L (o)L (Oip), will also cause an enhancement of the fluorescence in a similar manner to the Raman process. However, the decay of excited molecules by the surface channel will tend to mitigate the EM fluorescence enhancement effect. Two cases have been discussed in the literature " (a) the case of a molecule with a fluorescence quantum efficiency near unity in the free state, i.e., QE 1, and (b) the case with QE 1. If QE is low (<0.01), the fluorescent emission is estimated to be enhanced by ca. 10 whereas, for QE 1, a surface quenching of fluorescent emission by ca. 10" has been... 

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