Principal and Associated Bundles

1997 ◽  
pp. 258-264
Author(s):  
Krzysztof Maurin
Keyword(s):  
Associated Bundles

Rational Equivalence of Fibrations with Fibre G/K

1982 ◽  
Vol 34 (1) ◽  
pp. 31-43 ◽  
Author(s):  
Stephen Halperin ◽  
Jean Claude Thomas
Keyword(s):  
Finite Type ◽  
Homotopy Type ◽  
Lie Group ◽  
The Other ◽  
Homotopy Groups ◽  
Homotopy Equivalence ◽  
Rational Homotopy ◽  
Algebraic Invariants ◽  
Associated Bundles ◽  
Connected Lie Group

Let be two Serre fibrations with same base and fibre in which all the spaces have the homotopy type of simple CW complexes of finite type. We say they are rationally homotopically equivalent if there is a homotopy equivalence between the localizations at Q which covers the identity map of BQ.Such an equivalence implies, of course, an isomorphism of cohomology algebras (over Q) and of rational homotopy groups; on the other hand isomorphisms of these classical algebraic invariants are usually (by far) insufficient to establish the existence of a rational homotopy equivalence.Nonetheless, as we shall show in this note, for certain fibrations rational homotopy equivalence is in fact implied by the existence of an isomorphism of cohomology algebras. While these fibrations are rare inside the class of all fibrations, they do include principal bundles with structure groups a connected Lie group G as well as many associated bundles with fibre G/K.

On fibers of fat associated bundles

2017 ◽  
Vol 150 (1) ◽  
pp. 149-159
Author(s):  
Maciej Bocheński ◽  
Anna Szczepkowska ◽  
Aleksy Tralle ◽  
Artur Woike
Keyword(s):  
Associated Bundles

The detergent-resistant cytoskeleton of higher plant protoplasts contains nucleus-associated fibrillar bundles in addition to microtubules

1982 ◽  
Vol 56 (1) ◽  
pp. 319-335
Author(s):  
A.J. Powell ◽  
G.W. Peace ◽  
A.R. Slabas ◽  
C.W. Lloyd
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Sieve Tube ◽  
Optical Diffraction ◽  
Higher Plant ◽  
Accessory Cells ◽  
Drug Treatments ◽  
P Proteins ◽  
Associated Bundles ◽  
Carrot Protoplasts

Cytoskeletons prepared from carrot protoplasts often retain the nucleus, which is associated with bundles of 7 nm fibrils. These were also seen in cytoskeletons from oil palm, maize and Italian rye grass cells. By examining such cytoskeletons by immunofluorescence, negative staining and stereo scanning electron microscopy it appears that the bundles could be part of a more delicate system of fibrils distal to the nucleus. Optical diffraction of the bundles, staining with heavy meromyosin, drug treatments and phalloidin-staining all confirm that the bundles are not composed of actin. Bundles could not be isolated from such cytoskeletons in quantities sufficient for analysis, but by disrupting protoplasts prepared from stationary-phase cells it was possible to purify fibrillar bundles that appeared in the lysate. These were similar in size and properties to the nucleus-associated bundles. The former were shown by sodium dodecyl sulphate/polyacrylamide gel electrophoresis to be composed of several proteins and were sensitive to reducing agents. Since they are not composed of actin, the possibility was explored that these fibrils are related to the P-proteins of phloem sieve tube and accessory cells.

scholarly journals F actin bundles in Drosophila bristles. I. Two filament cross-links are involved in bundling.

1995 ◽  
Vol 130 (3) ◽  
pp. 629-638 ◽  
Author(s):  
L G Tilney ◽  
M S Tilney ◽  
G M Guild
Keyword(s):  
Plasma Membrane ◽  
Gene Product ◽  
Actin Filaments ◽  
Double Mutant ◽  
Longitudinal Section ◽  
Actin Bundles ◽  
Early Stages ◽  
Filament Bundles ◽  
Cross Links ◽  
Associated Bundles

Transverse sections though Drosophila bristles reveal 7-11 nearly round, plasma membrane-associated bundles of actin filaments. These filaments are hexagonally packed and in a longitudinal section they show a 12-nm periodicity in both the 1.1 and 1.0 views. From earlier studies this periodicity is attributable to cross-links and indicates that the filaments are maximally cross-linked, singed mutants also have 7-11 bundles, but the bundles are smaller, flattened, and the filaments within the bundles are randomly packed (not hexagonal); no periodicity can be detected in longitudinal sections. Another mutant, forked (f36a), also has 7-11 bundles but even though the bundles are very small, the filaments within them are hexagonally packed and display a 12-nm periodicity in longitudinal section. The singed-forked double mutant lacks filament bundles. Thus there are at least two species of cross-links between adjacent actin filaments. Hints of why two species of cross-links are necessary can be gleaned by studying bristle formation. Bristles sprout with only microtubules within them. A little later in development actin filaments appear. At early stages the filaments in the bundles are randomly packed. Later the filaments in the bundles become hexagonally packed and maximally cross-linked. We consider that the forked proteins may be necessary early in development to tie the filaments together in a bundle so that they can be subsequently zippered together by fascin (the singed gene product).

TRANSGRESSION IN ASSOCIATED BUNDLES

1991 ◽  
Vol 02 (04) ◽  
pp. 383-393
Author(s):  
SHIING-SHEN CHERN
Keyword(s):  
Associated Bundles
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