Abstract: An optical illumination and monitoring subsystem controls the operation of a flow cytometer having a carrier fluid that flows along a channel coupled to a droplet generator, which controls a point at which droplets break off from the carrier fluid, and a droplet sorter that is operative to cause selected droplets to be sorted along one or more droplet travel paths. The subsystem is operative to illuminate a respective droplet monitoring location along each of one or more droplet travel paths with a respective beam of light, such as that sourced from a common laser. In response to backscatter reflection from a droplet passing through the respective beam of light at a respective droplet monitoring location, the amplitude of the beam of light is increased. Then the droplet is monitored for the presence of a particle therein exhibiting detectable fluorescence as a result of the increase in the amplitude of the respective beam of light.

Abstract: Methods, systems and apparatus are provided for sorting particles in a stream of a sample in a flow cytometer by producing from a stable sort having desirable sort characteristics multiple images of a portion of the stream; generating from the multiple images an averaged numerical reference standard representative of the stable sort; continuously collecting during the sorting multiple running images of the portion of the stream; generating from the multiple running images at least one numerical sample average representative of the sample sort of each collection of the multiple running images; and comparing each numerical sample average to the numerical reference standard and determining whether a sample average exhibits a deviation from the reference standard that requires an adjustment of the sort. The sort may then be adjusted to eliminate or reduce the deviation and maintain the stable sort of the reference histogram. A novel imaging apparatus may be employed in a flow cytometer performing this method.

Abstract: Methods, systems and apparatus are provided for sorting particles in a stream of a sample in a flow cytometer by producing from a stable sort having desirable sort characteristics multiple images of a portion of the stream; generating from the multiple images an averaged numerical reference standard representative of the stable sort; continuously collecting during the sorting multiple running images of the portion of the stream; generating from the multiple running images at least one numerical sample average representative of the sample sort of each collection of the multiple running images; and comparing each numerical sample average to the numerical reference standard and determining whether a sample average exhibits a deviation from the reference standard that requires an adjustment of the sort. The sort may then be adjusted to eliminate or reduce the deviation and maintain the stable sort of the reference histogram. A novel imaging apparatus may be employed in a flow cytometer performing this method.

Abstract: A method was discovered of graft polymerizing water-soluble monomers with starch under conditions which are outwardly dry appearing. Conversion of monomer to polymer is nearly quantitative; and, since excess water is not present, there is no need for separate isolation and drying steps.