Cross-/? orientation

Figure C3.1.13. Experimentai configuration for far-UV nanosecond CD measurements using a frequency-upconverted Ti sapphire iaser as a probe source. Pj and P2 are Mgp2 Rochon poiarizers at cross orientations. SP is a strained transparent piate with about i ° of iinear birefringence for quasi-nuii eiiipsometric CD detection. Prism PMj and the iris Ij seiect the far-UV fourth hannonic of the argon iaser-pumped Ti-sapphire iaser s near-IR fundamentai output to probe the eiiipticity of the sampie. A second iaser beam at 532 nm is used to pump CD...

Lay-up proceeds by laying down the veneer which is to be the back surface of the panel. Then a sufficient number of pieces of core veneer are passed through the glue spreader to form the next layer of cross-oriented veneer. The glue spreader commonly used in hardwood plywood manufacture is a roU coater in which a pair of opposing mbber roUs are coated with a thin layer of adhesive. As the veneer is passed between the roUs, the adhesive is transferred to the surfaces of the veneer. Adhesive is appHed only to the cross-pfles and in sufficient quantity to provide a continuous layer on both opposing faces of veneer. Thus, in the case of a three-ply panel, only the core layer is spread with adhesive and in that of a five-ply panel, the second and fourth layers both of which are cross-pfles, are spread with adhesive. Then the top surface veneer, which is normally the decorative surface, is placed on the assembly. 

Fibers are commercially made from uniaxially drawn film. The film is extruded, slit into tapelike strips, drawn, fibrillated, and wound. As in the case of spinning, the drawing produces preferred alignment of the polymer chains along the axis of pull. If the drawing precedes slitting, the fiber gives some cross orientation and is less apt to split. 

Double-layered tetrathiafulvalenes have been prepared but with different face-to-face orientations. The coupling of 12 with triethylphosphine in toluene under reflux gave (26 %) 13, in which the TTF planes are slightly bent into a boat shape and overlapped with each other [95CL523]. Whereas, the related dimeric structure 14, where the two TTF moieties possess a cross-orientation, has recently been reported [95CL579,95TL5045]. 

W. Mai, W. Hu, C. Wang and T. A. Cross, Orientational constraints as three-dimensional structural constraints from chemical shift anisotropy The polypeptide backbone of gramicidin A in a lipid bilayer. Protein Sci., 1993, 2, 532—542. 

Other molecules that contain four key aromatic units arranged in a tetrahedral array, do not necessarily have Td symmetry. Distortion creates two groups of lower symmetric structures, D2d and Qv Two examples of what stem from D2d symmetry are the adamantane-like macrotricycle (119, R=C6H13), synthesized by Moore and Wu [160], and Tani et al. s cross-oriented biphenylophane (120) [134] obtained with its parallel polycyclic isomer (99). 

It is interesting that pyranoid systems having a cross-oriented, dienol ether linkage proved to be stable under the same conditions. Such a... 

The dienol ether 181 has an endo- and an exo-cyclic double bond which are cross-oriented to each other as shown in 183. The alkaline cleavage of the acetate groups led to the diol 182, which also proved stable. The dienol ethers 181 and 182 show u.v. and Cotton-effect maxima (see Fig. 4). 

For t = o this function is identical to the ordinary second moment. At larger times M2(t), a cross orientation-angular velocity correlation function, resembles the angular velocity correlation function C (t) for systems close to the diffusion limit 46-48. Contrary to the memory functions discussed above, M2(t) has the... 

Pig 14 Cross orientation-angular velocity correlation function for CH,J at various pressures 31 ... 

Processes in which tape cutting is carried out after stretching of the film has been performed cutting of a stretched film prevents width shrinkage, introduces some cross-orientation, and reduces the length-splitting tendency of the film. 

---