Introduction 1 1. Bundles 2 1.1. Pullback 2 1.2. Sections 3 1.3. Fiber bundles as fibrations 4 2. Vector bundles 4 2.1. Whitney sum 5 2.2. Sections of vector bundles 6 2.3. Inner products 6 3. Principal Bundles 7 3.1. Morphisms 7 3.2. Sections and trivializations 8 3.3. Associated bundles 9 3.4. Homotopy classification 11 3.5. B as a functor 14 4. Characteristic classes 16 4.1. Line Bundles 16 ...

In developing Drosophila bristles two species of cross-linker, the forked proteins and fascin, connect adjacent actin filaments into bundles. Bundles form in three phases: (a) tiny bundles appear; (b) these bundles aggregate into larger bundles; and (c) the filaments become maximally cross-linked by fascin. In mutants that completely lack forked, aggregation of the bundles does not occur so tha...