Effect of Helix Angle

The helix angle in the feed section will also have an optimum value for which the solids conveying rate reaches a maximum. This is obvious if one realizes that a zero-degree helix angle results in zero rate and a 90° helix angle also results in zero rate. Thus, somewhere between zero and 90°, the solids conveying rate will reach a maximum. The optimum helix angle can be determined from  

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An analysis of the flow behavior which is more or less confirmed by numerical simulations is presented by Leblanc. " The total flow in an internal mixer (tangential type) can be divided into a laminar, circulating flow which is pushed by the rotor tip, an axial directed flow, as an effect of the helix angle between axis and rotor wing and a leakage flow between rotor tip and mixing chamber waU (refer to Figure 35.6), or... 

Figure 4.24 Superhelix with helix angle < > governing handedness of packing between preferential helical main chains of contiguous polysilane chains for origin of Cotton effect of polysilane aggregates.

Fig. 17. Effect of the orientation of a helical structure on the position of the amide I band adapted from Cornut et al. [98]. Variation of the amide I band wavenumber maximum on the PM-IRRAS spectra as a function of the 6 tilt angle of the a-helix is shown. 9 is the tilt angle between the helical axis and the normal to the interface. Taken from Ref. [107] with permission from American Chemical Society.

Fig. 17 shows the effects of the orientation of a-helix structures on the position of the amide I band [107], It is adapted from calculated spectra in the amide I and II regions for pure a-helices when changing the tilt angle [98]. If the helix tilt angle is varied from 0° (a-helix perpendicular to the interface) to 90° (a-helix parallel to the interface), the amide I band position should shift from 1656 to 1649 cm-1. Therefore, changes in the orientation of a-helix structure may cause the shift of the amide I band, as well as the intensity ratio of amide land II. 

In the context of the collagen triple helix it can be concluded that the Cf-exo pucker of the proline in Yaa position is favored by stereoelectronic effects of a (4R)-OH substituent which also stabilizes the traus-Xaa-(4R)-Hyp peptide bond, thus preorganizing this residue in a conformation that best befits a triple helix. Conversely, in the Xaa position the Pro residue is preferred in the Cy-endo pucker the related dihedral angles are reported in Table 11.3. 

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