Emissivity ratio

Absorptivity.-emissivity ratio Alkyd silicone Thermal control coating... 

Parameters for crop differentiation are fine forms in leaves (trend), colouration of the leaves (hypothesis, but here too much growth for autumn colouration). Parameters for carrot differentiation are root form (from pointed to stump, Fig. 5.4), dry matter and emission ratio in spectral range luminescence. 

Fig. 6.11. Two types of FRET probes. (A) Ratiometric probes are formed by two fluorescent molecules that allow determination of emission ratio. (B) Quenched probes feature a donor fluorophore and a quencher. The emission increase of the donor after release of the acceptor is detected. Both types are frequently used to build proteinases probes.

A different strategy for measuring protease activity is based on the property of xanthene dyes to form H-type dimers (see Sect. 6.2.3) when they are in close proximity. These dimers are accompanied with a characteristic quenching of their fluorescence and, particularly for rhodamines, with a blue shift in the absorption spectrum [121, 122]. The probe D-NorFES-D designed to measure activity of elastase in HL-60 cells consists of an undecapeptide derivatized with one tetramethylrhodamine dye on each side. The sequence contains proline residues to create a bent structure and bring the two fluoro-phores in close proximity. Intact D-NorFES-D shows 90% of its fluorescence quenched plus a blue shift of the absorption spectrum. After addition of the serine protease elastase, an increase in the fluorescence and a bathochromic shift of the absorption spectrum is observed, resulting in an increase in the emission ratio [80],... 

Emission ratio imaging is extremely popular due to its simplicity and speed. In essence, cells expressing donors and acceptors are illuminated at the donor wavelength and fluorescence intensity data are collected both at donor (D) and at acceptor (S) channels. Collected data may be either images, or, in case high acquisition speed is crucial and spatial information is not required, dualchannel photometer readings (see Textbox 1). S and D are not overlap-corrected and FRET is simply expressed as the ratio of intensities1 as ratio = S/D. 

Ratio imaging nicely cancels out some of the main complications in the interpretation of wide-field images in that it normalizes fluorescence intensity differences caused by for example, cell height (Fig. 7.T1) as well as possible slow drift in excitation intensity. Light sources invariably are much less stable than detectors. Incidentally, for these reasons emission ratio imaging has been applied for over 3 decades by the Ca2+ imaging community. 

SNAFL dyes 7.0-7.8 excitation ratio 490/540 nm or emission ratio 540/630 nm... 

SNARF and SNAFL indicators are benzo[c]xanthene dyes that can be described as semi-naphthofluoresceins and semi-naphthorhodafluors, respectively, depending on whether the benzo[c]xanthene ring is substituted at the 10-position with oxygen or with nitrogen, respectively (Whitaker et al., 1991). These indicators, whose p K l values are in the physiological range, exhibit distinct emission bands for the pro-tonated and deprotonated forms so that emission ratio measurements are possible. In SNAFL, the acidic form is more fluorescent, whereas in SNARF, the basic form is more fluorescent. 

In the case of carboxypeptidase B, Shaklai et al.(2lT> compared the relative contributions to the protein phosphorescence from tyrosine and tryptophan for the apoenzyme, the zinc-containing metalloenzyme in the absence of substrate, the metalloenzyme in the presence of the substrate iV-acetyl-L-arginine, and the metalloenzyme in the presence of the specific inhibitor L-arginine. The tyrosine tryptophan emission ratio of the metalloenzyme was about a factor of four smaller than that of the apoenzyme. Binding of either the substrate or the inhibitor led to an increase in the emission ratio to a value similar to that of the apoenzyme. The change in the tyrosine tryptophan phosphorescence ratio was attributed to an interaction between a tyrosine and the catalytically essential zinc. The emission ratio was also studied as a function of pH. The titration data are difficult to interpret, however, because a Tris buffer was used and the ionization of Tris is strongly temperature dependent. In general, the use of Tris buffers for phosphorescence studies should be avoided. 

Carslaw DC (2005) Evidence of an increasing N02/NOx emissions ratio from road traffic emissions. Atmos Environ 39 4793 1802... 

Finally the so-called mono- and macro-tracer approaches can be applied for determining source contributions. These methods rely on the fact that a number of chemical compounds can be directly linked to biomass combustion emissions. For example, ambient concentrations of water-soluble potassium, certain PAHs, anhydrosugars and many other tracers have been used as indicators for the impact of biomass burning. When the fractions of one of these tracers in PM and carbonaceous aerosols emitted by wood burning are known (emissions ratios), the contribution of wood burning at a receptor site can be calculated based on the concentration of the considered tracer (mono tracer method). 

Instead of single tracers, a set of (macro) tracers such as OC, EC and levoglucosan can be used for source apportionment [43]. In this so-called macrotracer approach (MTA), the individual tracers are weighted according to published emission ratios. Optionally, the weighting factors can be further tailored according to local conditions [52] or constrained in sensitivity studies to derive an optimal solution [14]. 

In addition to using the absolute intensities of the atomic emission lines, the peak intensity ratios of these lines have been used to analyze samples. Tran et al. [77] analyzed the atomic intensity ratios of several organic compounds with the hope to determine the empirical formula of a compound based on the ratios from several elements. Calibration curves were built based on C H, C 0, and C N atomic emission ratios from various compounds that covered a wide range of stoichiometries. Then, four compounds with known stoichiometries were tested against the calibration curves. The ratios determined from the calibration curves were compared with the actual stoichiometries and showed accuracy of 3% on average. In the study of nitroaromatic and polycyclic aromatic hydrocarbon samples, the ratios between C2 and CN and between O and N of different samples were shown to correlate with the molecular formula [75], Anzano et al. [71] also attribute success of their correlation of plastics to differences in the C/H atomic emission intensity ratio of each sample. 

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