Signal Attenuation

Figure Bl.14.13. Derivation of the droplet size distribution in a cream layer of a decane/water emulsion from PGSE data. The inset shows the signal attenuation as a fiinction of the gradient strength for diflfiision weighting recorded at each position (top trace = bottom of cream). A Stokes-based velocity model (solid lines) was fitted to the experimental data (solid circles). The curious horizontal trace in the centre of the plot is due to partial volume filling at the water/cream interface. The droplet size distribution of the emulsion was calculated as a fiinction of height from these NMR data. The most intense narrowest distribution occurs at the base of the cream and the curves proceed logically up tlirough the cream in steps of 0.041 cm. It is concluded from these data that the biggest droplets are found at the top and the smallest at the bottom of tlie cream.

Dual chamber test method Measures near field shielding effectiveness by indicating the signal attenuation caused by passage through test material. 

Desensitization describes the rapid signal attenuation in response to stimulation of cells by receptor agonists. Changes in the coupling efficiency of receptors to signal transduction pathways and receptor internalization can account for desensitization and the development of pharmacodynamic tolerance. 

Here, S0 is the signal when G = 0, D is the self-diffusion coefficient, yG is the gyromagnetic ratio and am are roots of the Bessel function equation amaf3 2(ama) — (l/2)J3/2(a ma) = 0. If the system is polydisperse, the signal decay is due to contributions from droplets of different sizes. Then, the signal attenuation is given by the volume average over all sizes as... 

The flow artifacts detected in the droplet size measurements are similar to those reported by Goux et al. [79] and Mohoric and Stepisnik [80]. In their work natural convection effects led to an increase in the decay of signal attenuation curves, causing over-prediction in the self-diffusion coefficient of pure liquids. In order to avoid flow effects in droplet size distributions, flow compensating pulse sequences such as the double PGSTE should be used. It has been demonstrated recently that this sequence facilitates droplet size measurements in pipe flows [81]. 

It responds to electric arcs from welding operations. It can be affected by deposits of grease and oil on the lens. This reduces it s ability to "see" a fire. Lightning with long duration strikes can cause false alarm problems. Some vapors typically those with unsaturated bonds may cause signal attenuation. Smoke will cause a reduction in signal level seen during a fire. It may produce a false alarm response when subject to other forms of radiation such as from NDT operations. 

The signal attenuation in the diffusion-weighted spectra does not depend on the binding mode and position but only on the effective diffusion coefficient and on the experimental parameters mentioned above. 

Measurements were performed on a Waters 470 HPLC fluorescence detector equipped with a JASCO cuvette accessory and connected to a Perkin Elmer 561 strip chart recorder. Excitation and emission band-widths were 18 nm. Emission spectra were measured for the three excitation wavelengths mentioned above and emission starting from 10 nm higher than excitation up to 700 nm. Fluorescence at fixed wavelengths was measured four minutes after cuvette insertion and expressed as per-millage of the 275/303 fluorescence of 3.0 pM tyrosine in 50 mM HEPES, pH 7.4. Corrections were made for buffer- and blank collagenase fluorescence, and for signal attenuation. 

In all CSSF experiments filtration was performed immediately after the COSY step. Should there not be a sufficient chemical shift separation between H-2 protons, the magnetization could be further transferred along the spin system and filtered during one of the later spin-echoes. We note that such extensive transfer of magnetization can bring some signal attenuation due to the relaxation losses and a compromise setting of spin-echo intervals. 

An = the measured area of the N2H4 peak multiplied by its signal attenuation factor... 

EAj = the sum. of all the measured peak areas in the signal attenuation factors... 

Sharma SV, Fischbach MA, Haber DA et al. Oncogenic shock explaining oncogene addiction through differential signal attenuation. Clin Cancer Res 2006 12 4392s 395s. 

An estimate of the silane coverage could be made on the basis of the glass substrate signal attenuation and the carbon or nitrogen signal. This method of... 

Durham RM, Moran JJ, Mazuski JE, Shapiro MJ, Baue AE, Flint LM (2003) Multiple organ failure in trauma patients. J Trauma 55(4) 608-616 Eckle T, Grenz A, Laucher S, Eltzschig HK (2008) A2B adenosine receptor signaling attenuates acute lung injury by enhancing alveolar fluid clearance in mice. J Clin Invest 118(10) 3301-3315... 

Hollingsworth JW, Whitehead GS, Lin K, Nakano H, et al. 2006. TLR4 signaling attenuates ongoing allergic inflammation. J Immunol. 176 5856-5862. 

The resulting In A diagram is shown in Fig. 4, where the vertical dotted lines indicated the peak centers of the A, B,C,D peaks of Fig. 3. Notwithstanding the obvious signal attenuation (in comparison with Fig. 3), the coincidence of the peak structures is exact. 

---