Filament bundle

Prior to deposition on a moving belt or screen, the molten polymer threads from a spinnerette must be attenuated to orient the molecular chains of the fibers in order to increase fiber strength and decrease extendibiUty. This is accompHshed by hauling the plastic fibers off immediately after they have exited the spinnerette. In practice this is done by accelerating the fibers either mechanically (18) or pneumatically (17,19,20). In most processes, the fibers are pneumatically accelerated in multiple filament bundles however, other arrangements have been described wherein a linearly aligned row(s) of individual filaments is pneumatically accelerated (21,22). 

The pneumatic deposition of the filament bundles onto the moving belt results in formation of the web. A pneumatic gun uses high pressure air to move the filaments through a constricted area of lower pressure but higher velocity, as in a venturi tube. Pneumatic jets used in spunbonded production have been described (17,24). Unfortunately, the exceUent filament uniformity coming out of the spinnerette is lost when the filaments are consoHdated going through a gun. 

Glass-fiber reinforcement corrosion Unlike steel reinforcement, glass fibers are introduced in random orientation and throughout the paste. Typically, as filament bundles (of around 50 filaments), the fiber will be of variable length (usually up to 2 cm). 

FIGURE 1-9 The three types of cytoskeletal filaments. The upper panels show epithelial cells photographed after treatment with antibodies that bind to and specifically stain (a) actin filaments bundled together to form "stress fibers," (b) microtubules radiating from the cell center, and (c) intermediate filaments extending throughout the cytoplasm. For these experiments, antibodies that specifically recognize actin, tubu-... 

Bornslaeger, E. B., Corcoran, C. M., Stappenbeck, T. S., and Green, K. J. (1996). Breaking the connection Displacement of the desmosomal plaque protein desmo-plakin from cell-cell interfaces disrupts anchorage of intermediate filament bundles and alters intercellular junction assembly./. Biol. Chem. 134, 985-1002. 

Djabali, K., Piron, G., de Nechaud, B., and Portier, M. M. (1999). alphaB-crystallin interacts with cytoplasmic intermediate filament bundles during mitosis. Exp. Cell Res. 253, 649-662. 

The scale of the cells within the multifilament strand is controlled by two factors (1) the number of primary filaments bundled into the second feedrod, and (2) the size of the extrusion die used to form the second filament. The number of filaments bundled into the second feedrod is determined by both the size of the primary filaments and the size of the second feedrod. The decreasing ratio of extrusion die sizes results in a dramatic increase in the number of cells within a strand. In addition to making finer cell sizes possible, it is also much easier to lay coarse multifilament strands into a die than it is to lay small fibers. The strands lay straight and flat, whereas fibers tend to curl up and become intertwined. However, despite the fine cell size, the coarseness of the strands limits their use to architectures in which the scale of a cluster of cells is no less than 0.75 mm. 

Filament yams are twisted for two reasons. One is to supply certain esthetic characteristics such as touch, drapability, and elasticity. The other more fundamental reason is to provide physical integrity to the filament bundle so that it can be warped, woven, and knitted without excessive breakage or fraying of individual filaments. 

Furukawa, R., and M. Fechheimer. 1997. The structure, function, and assembly of actin filament bundles. IntT. Rev. Cytol. 175 29-90. 

Fig. 3. In vitro TIRF microscopy can also be employed to visualize complex protein-actin interactions. By attaching F-actin elongating proteins on beads (e.g., VASP, left) or on coverslips (e.g., formins, middle, processive elongation of single filaments can be visualized and analyzed. In these cases, filament buckling (white arrowdf can be observed due to the insertional assembly of actin monomers at the anchored filament barbed end (white circied). Moreover, the dynamic formation of complex structures such as filament bundles induced by VASP, fascin, or other actin-binding proteins in solution can be monitored in real time.

Cramer, L.P., Siebert, M. and Mitchison, T.J. (1997). Identification of novel graded polarity actin filament bundles in locomoting heart fibroblasts implications for the generation of motile force. J. Cell Biol. 136, 1287-1305. 

Demma, M., Warren, V, Hock, R. et al. (1990). Isolation of an abundant 50,000-dalton actin filament bundling protein from Dictyostelium amoebae./. Biol. Chem. 265, 2286-2291. 

Increasing twist in a cord further reduces filament buckling by increasing the extensibility of the filament bundle. 

Cotterill, G. R, Fergusson, J. A., Gani, J. S., and Burns, G. F. 1993. Scanning tunneUing microscopy of collagen I reveals filament bundles to be arranged in a left-handed helix, Biochem Biophys Res... 

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