Extinction profile

In these density profiles the latex particles, added before starting the experiment, migrate to that position in the cell where their density coincides with the density of the surrounding medium. The position of the particles can be recorded by schlieren optics or, if there is a particle density distribution, more precisely by scanning extinction measurements normally used for the characterization of proteins. Thus the density and extinction profile in the ultracentrifugation cell yield a criterion for the density distribution and hence, because of the correlation between chemical composition and particle density, a criterion for the composition distribution or heterogeneity of the latex particles. 

Figure 4. Density and extinction profile in rapid density gradient centrifugation of a latex mixture (concentration c 10 mg L 1, N = 40.000 min1, t — t0 = 15 min, wavelength of light v = 298 nm)...

The radiative transfer model in Madronich (1987) permits the proper treatment of several cloud layers, each with height-dependent liquid water contents. The extinction coefficient of cloud water is parameterized as a function of the cloud water computed by the three-dimensional model based on a parametrization given by Slingo (1989). For the Madronich scheme used in WRF/Chem, the effective radius of the cloud droplets follows Jones et al. (1994). For aerosol particles, a constant extinction profile with an optical depth of 0.2 is applied. 

High latitude aerosol observations have been secured by the Stratospheric Aerosol Measurement (SAM II) satellite system these have shown that the aerosol extinction profiles measured within the northern polar vortex differ significantly above 18 km from those measured outside the vortex (Me Cormick et d., 1983). 

The simplest approach to this problem is to approximate it by the (far-field) extinction profile (flfj), much easier to measure, i.e. 

For a nano-particle-based substrate, additional complications may arise because of polydispersity, i.e variations in size and / or shape of the particles. This introduces changes in the LSP resonance wavelength from one particle to another and can broaden dramatically the extinction profile To avoid... 

In all the results shown here, the extinction spectra were measured on bare substrates (not covered with molecules). However, it has been shown that molecular adsorption may affect the underlying LSP resonances and therefore change slightly the extinction profiles [39]. This aspect can be improved upon by measuring the extinction spectrum of the arrays for each molecule. 

The physicist Mie created the theoretical basis for choosing the appropriate opacifying agent Through his work the extinction profile of ball-shaped dielectric particles and, therefore, the optimum particle diameter of an opacifier dependent on wavelength, has become calculable. 

The appropriate SVD-derived spectral and temporal eigenvectors were selected and the temporal vectors were modeled. Ideally, the temporal vectors are the kinetic traces of individual components, each one being associated with a spectrum of a pure component Le., the spectral vector). Once the temporal vectors had been modeled the pure component spectra were reconstructed as a function of the pre-exponential multiplier obtained from the analysis, SVD determined spectral eigenvectors, and the corresponding eigenvalues. After the spectra of the component species were determined, the extinction profile was calculated and used along with the calculated decay times to construct a linear combination of the pure component species contributions to the observed... 

After creating the concentration profiles (Figure 6), an absorption profile was generated fi-om the pure component spectra using eq 9, and the spectral data matrix was reconstructed as a linear combination of the component spectra. The best fit was obtained using the simplest mechanism, A - B C, and was taken as the plausible mechanism. Using this mechanism and the extinction profiles, absorption spectra at different time points were calculated (Figure 7). TTie SVD derived kinetic parameters were compared with those obtained (7) from the... 

T. Dedoff, T. Sobisch, D. Lerche, Particle size distribution by space or time dependent extinction profiles obtained by analytical centrifugation. Part. Part. Syst. Charact. 23(2), 184—187 (2006). doi 10.1002/ppsc.200601028... 

In 1908, Mie proposed a theoretical model to explain the optical extinction (sum of the absorption and scattering properties) of noble metal nanoparticles. For nanoparticles with a radius (r) much smaller than the wavelength of light (2r X.), the extinction profile can be adequately explained by the simplified Mie formula (Eq.l). ... 

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