Attenuation length measurement

In this formula A and Aj are the spin-dependent hot electron attenuation lengths, which have been measured by various experimental techniques for different ferromagnetic materials [135-145]. The SVT and MTT have also successfully been used to measure Af and for 3d transition metal alloys [146-148], In these experiments the collector current is measured as a function of the ferromagnetic base layer thickness. 

Fig. 1. Mean free path for inelastic scattering, A, for aluminium [after Refs. (6) and (7)]. Experimental points measured mean attenuation lengths taken from the compilation by Powell (5)...

B. The NEMO Collaboration measured also the value of blue light attenuation length (L,. 1 = L/1 + A 1 j Lc = 35 5 m. Several authors usually quote the water effective scattering length, which is defined as /./, / < cos 1 >, where < cost > is the average cosine of the light scattering distribution in... 

Figure 7. Field attenuation length versus radio frequency for 2004 measurements at the South Pole.

Figure 4. Examples of direct and diffuse solar irradiance and a correction factor for diffuse path length in measurements (Hargreaves, unpublished). (A) Diffuse fraction of irradiance as a function of solar zenith angle during summer, 1996, L. Lacawac, Pennsylvania (41.3°N) and August 2001, Crater Lake, Oregon (42.9°N). (B) Calculated correction [17] to remove effects of irradiance field from near-surface diffuse attenuation (K ) measurements, based on data in part (A).

Fig. 5.2 Left attenuation of the tungsten feature as a function of cobalt thickness in monolayers (ML) for the spin integrated measurement (filled dianwnd), for majority (filled square) and minority (open circle) electrons. Right universal curve of the inelastic mean firee path [4] included are the different attenuation lengths for majority (filled square) and minority (open circle) electrons being 4.4 and 3.2 ML, respectively, at a kinetic energy of 10 eV...

For the volume fractions presented in Figs. (3-6) the shear modulus is on the order of lOdyn/cm and the sound velocity V(= /s/p) = l-5cm/s. The microscopic relaxation time T(-rj/E) 1-10 ms, and the attenuation length A.[= (ImK) =2F/0 t1 1-10cm. For frequencies below IkHz the dissipation is small and the shear waves are propagating. The dimensions of the measuring cell encourage the formation of standing waves. 

An alternative method of deriving relative sensitivity factors would be to use the calculated intensities of. Scofield [40]. after correction for the energy dependences of the attenuation length and analyzer function, as in Eq. (.34). but to use an accurate measure of the full intensity for the experimental data, such as would be obtained from the Tougaard background method (31 ]. A full evaluation of such an approach is not yet available. Preliminary work seems to suggest that the overall results may be more accurate, but possibly with lower precision. That is, there may be benefits in using this method if the analysis is... 

To obtain an accurate measurement of the regional distribution of isotope concentration in the body, the primary correction is that for attenuation. The basic principles of attenuation correction, relatively straightforward in PET, are as follows. Consider the attenuation lengths a and b on either side of the point source in Figure 2B. From Equation [2], attenuation along these two paths will be proportional to exp[-p,a]... 

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