In this manuscript we investigate the capabilities of the Discrete Dipole Approximation (DDA) to simulate scattering from particles that are much larger than the wavelength of the incident light, and describe an optimized publicly available DDA computer program that processes the large number of dipoles required for such simulations. Numerical simulations of light scattering by spheres with size parameters x up to 160 and 40 for refractive index and 2 respectively are presented and compared with exact results of the Mie theory. Errors of both integral and angle-resolved scattering quantities generally increase with m and show no systematic dependence on x. Computational times increase steeply with both x and m, reaching values of more than 2 weeks on a cluster of 64 processors. The main distinctive feature of the computer program is the ability to parallelize a single DDA simulation over a cluster of computers, which allows it to simulate light scattering by very large particles, like the ones that are considered in this manuscript. Current limitations and possible ways for improvement are discussed. 05. 1 = m

General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Abstract. We characterize T-and B-lymphocytes from several donors, determining cell diameter, ratio of nucleus to cell diameter, and refractive index of the nucleus and cytoplasm for each individual cell. We measure light-scattering profiles with a scanning flow cytometer and invert the signals using a coated sphere as an optical model of the cell and by relying on a global optimization technique. The main difference in morphology of T-and B-lymphocytes is found to be the larger mean diameters of the latter. However, the difference is smaller than the natural biological variability of a single cell. We propose nuclear inhomogeneity as a possible reason for the deviation of measured light-scattering profiles from real lymphocytes from those obtained from the coated sphere model. © 2009 Society of Photo-Optical Instrumentation Engineers.

With this work we review the development of theoretical and experimental aspects of the scanning flow cytometry (SFC). The optical and hydrodynamic systems of the SFC provide the measurement of fluorescence and light scattering of individual particles with a typical rate up to 500 particles/s. In addition the optical system of the SFC has the capability of individual particle analysis beyond that of an ordinary flow cytometry. The SFC measures an entire angular dependency of light scattering intensity (flying light scattering indicatrix, FLSI) over angles ranging from 5° to 120°. The fluorescence collection efficiency of the SFC approaches 1/3 of a sphere. Moreover, the optical system of the SFC provides the measurement of fluorescence in a time-resolved mode on a microsecond time scale. The processing of the output data in light scattering is based on a parametric solution of the inverse light-scattering problem, the FLSI method. The FLSI method allows the determination of size and refractive index of spherically modeled particles over a range of diameters from 0.9 to 15 μm and a range of refractive indexes from 1.37 to 1.60. The performance of the SFC in different applications has been demonstrated.