Quenching phenomena

Nelson RA, Pasamehmetoglu KO (1992) Quenching phenomena. In Hewitt GF, Delhaye JM, Zu-ber N (eds) Post-dryout Heat transfer. CRC, Boca Raton, pp 39-184 Owens WL (1961) Two-phase pressure gradient. In ASME International Developments in Heat Transfer, Part II. ASME, New York... 

There are several luminescence flow-through sensors based on both fluorescence quenching phenomena and biolimiinescent reactions. 

Recent improvement in the designs of PL cells and coupling of the cells to a dynamic vacuum system (Bailly et al., 2004) have made it possible to avoid quenching phenomena from gas-phase molecules. The emission spectra obtained with MgO are better resolved and more stable over time leading to an optimized PL yield of the more reactive surface species, namely Olc2 ions. 

The dependence L(T/) l/D implies that the left-hand side of equation (24) increases as the tube diameter D decreases. Since none of the other physical parameters in equation (24) depend on Z), an extinction condition is reached when the tube diameter D becomes sufficiently small. This minimum tube diameter is called the quenching diameter, which is empirically approximately the same as (perhaps 25 % or 50 % greater than) the quenching distance d defined in Section 8.1. Quenching phenomena can thus be attributed to conductive heat losses. 

The anneal at 350° C. may, therefore, be described as a softening anneal, producing maximum ductility in the metal. The anneal at 475° C. will be considered side by side with Quenching Phenomena in the following chapter. 

R. A. Nelson and K. O. Pasamehmetoglu, Quenching Phenomena, in Post-Dryout Heat Transfer, G. F. Hewitt, J.-M. Delhaye, and N. Zuber eds., chap. 2, CRC Press, Boca Raton, FL, 1992. 

J. Filipovic, F. P. Incropera, and R. Viskanta, Quenching Phenomena Associated with a Water Wall Jet II. Comparison of Experimental and Theoretical Results for the Film Boiling Region, Exp. Heat Transfer, 8, pp. 119-130,1995. 

However, the magnitudes of the binding constants do not correlate exactly with the extension of the quenching phenomena (06CC3824). 

Eug(W07)3.5H20. The presence of five water molecules in the tungstate structure, that is, an extra molecule in relation to the molybdate, can be pointed out as the main factor leading to such quenching phenomena. Furthermore, the presence of a larger number of oxygen atoms in the molybdate structure can promote efficient energy absorption and transfer to the europium cation. 

The main characteristics of the DNS-method used in our studies are summarized in [1,2]. This paper is devoted to recent work employing DNS with complex chemistry. A study of the flame structure of H2/O2/N2 flames is presented in Section 2, turbulent methane-air flames are addressed in Section 3 and an investigation of quenching phenomena of methane-air by a cold wall in Section 4 concludes. 

In a different approach not relying on AuNP-luminol redox chemistry, it has been shown that the incorporation of the well-known ECL-active dye Ru(bpy)3 into silica nanoparticles can increase the ECL intensity about three orders of magnitude compared to the free dye by limiting self-quenching phenomena [103]. However, the mechanism of ECL in silica particles is rather complex and presumably depends on parameters such as the concentration and diffusion properties of a co-reactant (e.g. tripropylamine). For instance, the co-reactant is crucial to activate ECL if the Ru(bpy)3 -containing core is completely passivated by the silica shell and resistant to direct oxidation or reduction, i.e. if the distance from the electrode is too large [104]. 

Some of these applications are complementary to the steady state methods discussed in section 8.2. Investigations of fluorescence lifetimes and of anisotropy or fluorescence quenching phenomena in the lifetime mode, that is during the decay after a single flash, require more elaborate instrumentation and theory than steady state investigations. On the whole applications rather than detail of methods are discussed here. The use of the lifetime method for the study of molecular rotation, domain movement and more local dynamic events can often, some experts say always, provide additional information even for those problems which can be investigated with considerable success by steady state measurements. 

The origin of the change in fluorescence emission at the temperature T lies in the photophysical process itself, i.e. in quenching phenomena, the extent of which shoj ld depend on the nature of the molecules next to the label. In fact, PS is surrounded by a mixture of PS and PVME in the homogeneous blends, but mainly by PS molecules in the phase-separated systems. Thus, a simple explanation of the change in fluorescence intensity would be that PS emission is greater in PS than in PS-PVME mixtures or, in other words, that PVME is responsible for the quenching of the fluorescence emission. 

In addition to the reasonable sensitivity toward SO2, which may, in fact, be extended to lower limits of detection with a modification of the experimental setup, p-PS is also relatively robust. PS survives many cycles of exposure to SO2 and Ar without any obvious degradation of PL intensity. Experiments of modulated exposure of PS to SO2 and Ar for over 6 hours at -lOmin. cycles did not result in a significant decrease in the PL intensity. The longer-term stability has not been ascertained, but the PS luminescence is stable over more than a year and exhibits a base quenching phenomena over at least many months. 

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