-
[show abstract]
[hide abstract]
ABSTRACT: Inadvertent inhalation of asbestos fibers and the subsequent development of incurable cancers is a leading cause of work-related deaths worldwide. Currently, there is no real-time in situ method for detecting airborne asbestos. We describe an optical method that seeks to address this deficiency. It is based on the use of laser light scattering patterns to determine the change in angular alignment of individual airborne fibers under the influence of an applied magnetic field. Detection sensitivity estimates are given for both crocidolite (blue) and chrysotile (white) asbestos. The method has been developed with the aim of providing a low-cost warning device to tradespeople and others at risk from inadvertent exposure to airborne asbestos.
Optics Express 05/2013; 21(9):11356-67. · 3.59 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Inadvertent inhalation of asbestos fibers and the subsequent development of incurable cancers is a leading cause of work-related deaths worldwide. Currently, there is no real-time in situ method for detecting airborne asbestos. We describe an optical method that seeks to address this deficiency. It is based on the use of laser light scattering patterns to determine the change in angular alignment of individual airborne fibers under the influence of an applied magnetic field. Detection sensitivity estimates are given for both crocidolite (blue) and chrysotile (white) asbestos. The method has been developed with the aim of providing a low-cost warning device to tradespeople and others at risk from inadvertent exposure to airborne asbestos.
Optics Express. 05/2013; 21(9):11356-11367.
-
[show abstract]
[hide abstract]
ABSTRACT: We describe preliminary results from an optical scattering instrument designed to assess the shapes and sizes of microscopic atmospheric cloud particles, especially the smallest ice crystals, that can profoundly affect cloud processes and radiative properties. The new instrument captures high-resolution spatial light scattering patterns from individual particles down to approximately 1 microm in size passing through a focused laser beam. Its significance lies in the ability of these patterns to provide morphological data for particle sizes well below the optical resolution limits of current cloud particle probes.
Optics Letters 08/2008; 33(13):1545-7. · 3.40 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A new model suitable for rapid computation of scattering on faceted dielectric objects such as ice crystals, which combines ray tracing with diffraction on flat facets, is tested against SVM. Phase functions and asymmetry parameters are compared for scattering from long hexagonal prisms at normal incidence.
-
[show abstract]
[hide abstract]
ABSTRACT: A 3D implementation of a new model of light scattering applicable to dielectric faceted objects is introduced. The model combines standard geometric optics with diffraction on individual facets. It can be applied to any faceted geometry. The model adds no significant computational overheads to classical geometric optics yet provides much improved results. Initial results for long hexagonal columns are compared to SVM and appear favourable. 2D scattering patterns are calculated for a hexagonal column in a fixed orientation and compared to those created by ice analogue crystals in the laboratory with close agreement. The comparison includes the observation of a guided wave propagating along the length of the column. The new model is then applied to a selection of geometries to illustrate how it could be used to aid particle characterization, particularly in the case of cirrus ice.
Journal of Quantitative Spectroscopy and Radiative Transfer.
-
[show abstract]
[hide abstract]
ABSTRACT: Angle-dependent light-scattering measurements on single ice analogues crystals are described. Phase functions and degree of linear polarization are measured for electrodynamically levitated crystals. A procedure for randomizing particle orientation during levitation is demonstrated. The dependence of scattering on the shape, complexity and surface roughness of the crystals is examined. The phase functions from complex crystals with smooth surfaces show little dependence on shape. There is close agreement between the measured functions and the analytic phase function for ice clouds. However, rosettes with rough surfaces have qualitatively different phase functions, with raised side and back scattering. The asymmetry parameter is typically about 0.8±0.04 and 0.63±0.05 for smooth and rough crystals, respectively. The 22° halo peak is present for smooth rosettes and aggregates but absent for rough rosettes. Two-dimensional scattering patterns from several crystals in fixed orientations are also shown. The results suggest that it may be possible to use such patterns to discriminate not only between crystals of different shape but also to obtain some information on surface properties.
Journal of Quantitative Spectroscopy and Radiative Transfer.
-
[show abstract]
[hide abstract]
ABSTRACT: A new model suitable for rapid computation of scattering on faceted dielectric objects such as ice crystals is presented. It combines ray tracing with diffraction on flat facets. The model allows retaining the ray nature of the internal field by calculating the diffraction component using an approximation for the far field direction of the Poynting vector. While this approach is similar to methods using the uncertainty principle, it does not require the use of angular distributions of diffracted rays, which leads to negligible computational overheads with respect to pure ray tracing. Results showing angle-dependent scattering computed for long hexagonal prisms, including phase functions and degree of linear polarization, are presented and compared with other models and with measurements on hexagonal fibers.
Journal of Quantitative Spectroscopy and Radiative Transfer.
