Later papers associated the scattering coefficient b with scattering into a much smaller angle of 4°. The first correlation based on measurements was presented by Mankovsky (1971). Morel (1974), who used the Mie model (an analytical http://www.selleckchem.com/products/LDE225(NVP-LDE225).html solution of electromagnetic wave interaction with spherical particles), showed that the ratio βp(4°)/bp changes only slightly with the refractive index and the particle size distribution. Recent measurements by Chami et al. (2005) show a linear correlation between the values of βp(4°) and the scattering coefficient bp. As with the scattering coefficient b, links between the backscattering

coefficient bb and scattering functions β were sought. One of the first to address the problem was Oishi (1990), who used modelling methods to show that the scattering function for an angle of 120° gave the best linear correlation with bb. Modelling was carried out with Mie algorithms for various refractive indices and different particle size distributions. In his paper, Oishi published some measurements that confirmed

the Crenolanib results of calculations. The optical scheme of an instrument for determining the backscattering coefficient on the basis of β(140°) measurements was presented by Maffione et al. (1991) and Maffione & Dana (1997). The designs of the latter authors were incorporated into commercially available instruments. In response to that latter paper Boss & Pegau (2001) supplied new arguments to justify Oishi’s ideas. Like Maffione & Dana (1997) they used the non-dimensional quantity χ(θ, λ), the definition of which includes the ratio of the backscattering coefficient bb to the volume scattering function for various scattering angles: equation(1) χθλ=bbλ2πβθλ. Boss & Pegau (2001) analysed the variability of χ(θ) for clean sea water and for suspensions. They also used new measurements and stated that the most accurate approximation of the backscattering coefficient could be obtained with measured β(117°). Other instruments were designed, enabling bbp to be obtained on the basis of the measurement of light scattered into angles around 117°. Sullivan

& Twardowski (2009) recently carried out research based on a very large number of measurements. They showed that the strongest correlation between backscattering coefficient and volume FER scattering function was obtained for scattering angles in the 110°–120° range. An interesting spectral analysis of the function χ(θ, λ), based on measurements made with the previous version of a prototypical volume scattering meter for Black Sea water and selected phytoplankton cultures, was presented by Chami et al. (2006). They considered the particle-affected function χ for scattering angles 120° and 140°, concluding that χp(120°) was spectrally less dependent than χp(140°); the former is therefore recommended, especially during phytoplankton blooms.